pISSN 3022-6783
eISSN 3022-7712

View

Article View

Clin Transplant Res 2024; 38(4): 377-403

Published online December 31, 2024

https://doi.org/10.4285/ctr.24.0039

© The Korean Society for Transplantation

Beyond the icebox: modern strategies in organ preservation for transplantation

Kidus Haile Yemaneberhan1,2,* , Minseok Kang1,* , Jun Hwan Jang3 , Jin Hee Kim3 , Kyeong Sik Kim1 , Ho Bum Park3 , Dongho Choi1,2,4,5

1Department of Surgery, Hanyang University College of Medicine, Seoul, Korea
2Hanyang Institute of Bioscience and Biotechnology, Hanyang University, Seoul, Korea
3Department of Energy Engineering, Hanyang University, Seoul, Korea
4Research Institute of Regenerative Medicine and Stem Cells, Hanyang University, Seoul, Korea
5Department of HY-KIST Bio-convergence, Hanyang University, Seoul, Korea

Correspondence to: Kyeong Sik Kim
Department of Surgery, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea
E-mail: crane87@hanyang.ac.kr

Dongho Choi
Department of Surgery, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea
E-mail: crane87@hanyang.ac.kr

*These authors contributed equally to this study as co-first authors.

Received: September 4, 2024; Revised: October 18, 2024; Accepted: October 21, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Organ transplantation, a critical treatment for end-stage organ failure, has witnessed significant advancements due to the integration of improved surgical techniques, immunosuppressive therapies, and donor-recipient matching. This review explores the progress of organ preservation, focusing on the shift from static cold storage (SCS) to advanced machine perfusion techniques such as hypothermic (HMP) and normothermic machine perfusion (NMP). Although SCS has been the standard approach, its limitations in preserving marginal organs and preventing ischemia-reperfusion injury (IRI) have led to the adoption of HMP and NMP. HMP, which is now the gold standard for high-risk donor kidneys, reduces metabolic activity and improves posttransplant outcomes. NMP allows real-time organ viability assessment and reconditioning, especially for liver transplants. Controlled oxygenated rewarming further minimizes IRI by addressing mitochondrial dysfunction. The review also highlights the potential of cryopreservation for long-term organ storage, despite challenges with ice formation. These advances are crucial for expanding the donor pool, improving transplant success rates, and addressing organ shortages. Continued innovation is necessary to meet the growing demands of transplantation and save more lives.

Keywords: Organ transplantation, Machine perfusion, Cryopreservation, Nanobiotechnology

HIGHLIGHTS
  • Machine perfusion extends organ viability and improves transplant outcomes.

  • Hypothermic perfusion reduces ischemia-reperfusion injury in organ preservation.

  • Hypothermic machine perfusion is now the gold standard for preserving high-risk kidneys, leading to more favorable transplant outcomes.

  • Normothermic perfusion revitalizes marginal organs, significantly lowering discard rates and enabling real-time organ function assessment.

  • Cryopreservation holds future promise for long-term organ storage.

The advent of organ transplantation has significantly improved the quality of life for many individuals suffering from end-stage organ failure. The first successful kidney transplant, performed between identical twins, took place in 1954. This was followed by liver, pancreas, and heart transplants in the late 1960s [1]. However, the success of these transplants was limited by immunological rejection until the development of effective immunosuppressive medications in the 1980s [2].

A variety of solutions with properties similar to those of the human body have been developed for organ preservation. These include Euro-Collins (EC), University of Wisconsin (UW), and histidine-tryptophan-ketoglutarate solutions [3]. These solutions enable the flushing, storage in an icebox, and transportation of organs. This method, known as static cold storage (SCS), is currently the standard approach for organ preservation [4,5].

Despite ongoing efforts, the current approach is insufficient to meet the growing demand for organ transplants. According to the United Network for Organ Sharing, the number of people currently on the waiting list for organ transplants has reached 103,991, more than double the 46,630 transplants performed in 2023 [6]. The Health Resources and Services Administration notes that 17 individuals die each day while waiting for an organ transplant [7]. Additionally, the waiting list for organ transplants in South Korea has grown by 10,000 in the past 5 years [8]. In response to this discrepancy, healthcare professionals and researchers are exploring the use of extended criteria donor (ECD) organs, which are typically considered unsuitable for transplantation [9].

The development of improved organ preservation techniques and equipment has been driven by research into the cellular and molecular mechanisms of ischemia-reperfusion injury (IRI), which significantly contributes to organ damage during preservation and transplantation [10]. These innovations aim to sustain organs in an ideal environment, thus extending the preservation duration or employing advanced machines to simulate conditions akin to physiological states (Fig. 1). This approach facilitates the evaluation, preservation, and possible treatment of organs before transplantation [11].

Figure 1. Progression of temperature trends in organ machine perfusion. Hypothermic machine perfusion (HMP): blue-shaded, hypothermic oxygenated perfusion (HOPE): gray-shaded, subnormothermic machine perfusion (SNMP): yellow-shaded, normothermic machine perfusion (NMP): green shaded, controlled oxygenated rewarming (COR): orange-shaded [1262].

Furthermore, novel subzero organ preservation techniques are currently under investigation with the goal of improving existing preservation methods and ultimately enabling organ banking. This review paper explores the current organ preservation strategies, including SCS, hypothermic machine perfusion (HMP), subnormothermic machine perfusion (SNMP), and normothermic machine perfusion (NMP). Additionally, this review examines the latest advancements and current status of subzero organ preservation techniques such as partial freezing, supercooling, isochoric preservation, vitrification, and nanowarming.

IRI poses a significant challenge in organ transplantation. It is unavoidable for transplant organs to undergo a period of reduced blood flow (ischemia) followed by the restoration of blood flow (reperfusion) upon transplantation. During the ischemic phase, anaerobic metabolism predominates, leading to adenosine triphosphate (ATP) depletion, cellular damage, and the accumulation of metabolic waste products. This process results in the generation of danger-associated molecular patterns (DAMPs) due to cellular debris and metabolic stress. DAMPs activate pattern recognition receptors, triggering a signaling pathway that leads to the release of proinflammatory cytokines and intensifies the inflammatory response. Upon reperfusion, the restored blood flow activates the immune system, and the sudden influx of oxygen promotes the production of mitochondrial reactive oxygen species (ROS), further exacerbating inflammation and tissue damage [63,64]. This cascade continues and ultimately leads to organ injury, potentially increasing the risk of graft dysfunction and rejection [65].

IRI has been shown to negatively impact organs in various transplantation scenarios. In liver transplants, IRI leads to the early demise of hepatocytes and sinusoidal cells. At the same time, it activates hepatic stellate cells, which affects long-term recovery and can lead to clinical complications such as early allograft dysfunction (EAD) and nonanastomotic biliary strictures (NAS) [66,67]. Similarly, in kidney transplantation, IRI is crucial in the development of conditions like delayed graft function (DGF) or primary nonfunction. The associated proinflammatory response may also promote progressive interstitial fibrosis, potentially leading to chronic graft dysfunction, which is characterized by interstitial fibrosis and tubular atrophy [68]. In heart transplantation, IRI increases the risk of primary nonfunction, graft rejection, and cardiac edema. It also worsens myocardial and endothelial damage, which in turn promotes allograft fibrosis [69]. Lastly, in lung transplantation, IRI causes increased permeability of the pulmonary endothelium, leading to pulmonary edema and a subsequent reduction in function. Furthermore, IRI heightens the likelihood of prolonged mechanical ventilation and extended hospital stays for lung transplant recipients, thereby increasing the risk of late graft failure [70].

SCS is currently the most prevalent method used for organ preservation. This process involves flushing the organs with a preservation solution and then storing them at low temperatures between 2 °C and 4 °C [71]. The fundamental principle of SCS is that low temperatures reduce the rate of cellular metabolism, thereby decreasing the energy demand. Additionally, the preservation solution helps optimize the cellular environment and mitigate cellular damage by reducing osmotic and reperfusion injury [72].

A variety of solutions have been introduced in clinical practice; however, the UW solution remains the gold standard for multiorgan retrieval [73]. The effectiveness of the UW solution depends on its unique composition, which includes multiple cell-impermeant agents such as lactobionic acid, raffinose, and hydroxyethyl starch. These agents help prevent cellular swelling during cold ischemic storage. Additionally, the solution contains glutathione and adenosine, which support the restoration of normal metabolism during reperfusion. They do this by enhancing the antioxidant capacity of the organs and promoting the generation of high-energy phosphates, respectively [72].

Despite the simplicity and cost-effectiveness of SCS compared to more complex preservation techniques, it has several significant drawbacks. Prolonged hypothermic preservation can damage tissue, reducing the viability of donor organs [74,75]. Additionally, assessing organ function and predicting viability during cold storage pose significant challenges. Furthermore, marginal organs, such as those from cardiac-death donors and ECDs, are more susceptible to IRI, leading to the discarding of many nonideal organs due to the high risk of unfavorable outcomes [76].

Although SCS presents inherent challenges, the primary limitation in organ transplantation is the scarcity of available organs. To broaden the donor pool and improve transplant outcomes from marginal organs such as ECD or donors after circulatory death (DCD), current research is shifting focus from SCS to ex vivo machine perfusion. Unlike SCS, machine perfusion supports effective nutrient and oxygen delivery for cellular metabolism and facilitates the removal of metabolic waste products. This process creates an environment that mimics natural cardiac perfusion, thus preventing ischemic injury and potentially enabling the use of marginal organs. For example, a study involving NMP of 42 discarded livers showed improved preservation of peribiliary glands and microvasculature, as well as a higher level of cholangiocyte proliferation. Consequently, 25 of these livers were accepted for transplantation following NMP [58]. Additionally, machine perfusion enables the administration of various substances, such as cytoprotective or immunomodulating agents, during the cold ischemic period. It also enables the surgical team to assess organ viability and function before transplantation, aiding in more informed decisions regarding its suitability.

Perfusion protocols for organ preservation are primarily categorized based on the temperature of the perfusate. These categories include HMP (2 °C–10 °C), SNMP (20 °C–33 °C), and NMP (36 °C–38 °C) [77,78]. Table 1 summarizes the experiments and outcomes of machine perfusion for liver and kidney preservation, organized by temperature. The machine perfusion technique offers a promising approach to mitigate IRI. It is crucial, however, to understand the distinct advantages and limitations of each technique, as they are not interchangeable (Table 2) [79]. For example, HMP is primarily employed to reduce IRI, whereas NMP is utilized for assessing organ viability [80].

Table 1. Summary of machine perfusion experiments and outcomes according to the temperature used

StudyTypeOrganTemperature (°C)Warm ischemia time (min)Cold ischemia time (hr)Perfusion time (hr)Perfusate solutionResult
Hypothermic machine perfusion (HMP)
Guarrera et al. (2010) [24]HumanLiver4–640–507–113–5Vasosol• The HMP group had a 5% early allograft dysfunction rate versus 25% in the control group, with no vascular complications and lower serum injury markers
• They also had a shorter mean hospital stay
Henry et al. (2012) [27]HumanLiver4–640–507–113–5Hextend• The HMP group had lower inflammatory marker expression and no ultrastructural damage, unlike the cold storage group
Zhang et al. (2016) [35]RabbitKidney4–835NA4Human carbonic anhydrase II• The HMP group had significantly lower apoptosis rates and cleaved caspase-3 expression, with higher ezrin and phosphorylated AKT levels than the cold storage group
• HMP reduced renal cell apoptosis during ischemia-reperfusion injury via the ezrin/AKT pathway
Faucher et al. (2022) [52]HumanKidney2–5NA1610Kidney preservation solution-1• With a longer perfusion time, 23 metabolites increased and 8 decreased in the solution
• Extended perfusion did not affect transporter mRNA expression, and neither were predictive of graft outcomes
Hypothermic oxygenated perfusion (HOPE)
Jochmans et al. (2020) [48]HumanKidney4NANA24University of Wisconsin Machine Perfusion Solution + O2 (100%)• In the study, the HOPE group had fewer severe complications (11% vs. 16%), a lower rate of graft failure (3% vs. 10%), and a mean estimated glomerular filtration rate difference of 3.7 mL/min per 1.73 m2 at 12 months compared to the HMP group
Panayotova et al. (2024) [60]HumanLiver5–720–302–52–4Vasosol + O2 (100%)• Early allograft dysfunction rates were 11.1% with HOPE and 16.4% with static cold storage. Biliary strictures occurred in 16.4% of static cold storage cases and 6.3% of HOPE cases
• The predicted 7-day graft failure risk was lower with HOPE (3.4%) than with static cold storage (4.5%)
Subnormothermic machine perfusion (SNMP)
Tolboom et al. (2012) [26]RatLiver20–3060NA5Williams medium E, insulin erythrocytes, L-glutamine, heparin• After 4 weeks posttransplantation, livers preserved with SNMP had a 100% survival rate, while those preserved with cold storage died within 24 hours
• Hematoxylin and eosin analysis showed that machine perfusion-preserved livers maintained a fresh liver-like architecture
• At 28 days, livers preserved at 20 °C and 30 °C had the highest total bilirubin values
Hoyer et al. (2014) [28]PigKidney2030NA7Custodiol-N, pyrogen-free dextran 40• Kidneys preserved by SNMP had significantly higher blood flow, urine output, and creatinine-clearance—10 times higher than cold storage and 2 times higher than hypothermic machine perfusion
• SNMP also best-preserved structural integrity histologically
Bruinsma et al. (2014) [29]HumanLiver2120–505–193Phenol-red Williams medium E, insulin, penicillin/streptomycin, nutrients, hydrocortisone• After perfusion, liver oxygen uptake and ATP levels improved, bile production increased, and bile composition became more favorable
• Liver function, indicated by urea and albumin production, was also observed during perfusion
Abraham et al. (2024) [62]Pig & humanKidney22–2530NA24Albumin, dexamethasone, heparin, insulin, multivitamins• The human kidney maintained stable functional and biological parameters after 24 hours of SNMP perfusion
• Pig kidneys perfused with SNMP for 24 hours and then autotransplanted showed reduced creatinine and blood urea nitrogen levels after 7 days compared to the cold storage group
Normothermic machine perfusion (NMP)
Schön et al. (2001) [15]PigLiver3760–100NA4Whole pig blood, electrolyte solutions, heparin• All animals receiving livers treated with normothermic extracorporeal liver perfusion survived more than 7 days posttransplant
• In contrast, all animals in the 4-hour static cold storage group experienced primary graft nonfunction within 24 hours
Hosgood et al. (2018) [39]HumanKidney35–3614271Red blood cell-based solution, supplements• In Phase 1, 28 kidneys were deemed suitable for transplantation with a quality assessment score of 1–3
• In Phase 2, 10 kidneys were assessed by NMP, leading to 5 transplants, of which 4 showed initial graft function
Nasralla et al. (2018) [40]HumanLiver3717–251–25–12Packed red blood cells, antibiotics, Gelofusine, insulin, heparin, nutrition• Compared to cold storage, NMP resulted in a 50% reduction in graft injury, a 50% lower organ discard rate, and a 54% longer preservation time
• However, there was no significant difference in bile duct complications or patient survival
Thompson et al. (2022) [54]HumanKidney37NA206Packed red blood cells, heparin, dexamethasone, mannitol, sodium bicarbonate, 1 mg miRNA-24-3p antagomir• During NMP, using a perfused antagomir targeting miR-24-3p increased the expression of genes controlled by this microRNA, such as heme oxygenase-1
• This effect was absent in the cold perfusion group, and other gene expressions remained unchanged, highlighting the antagomirʼs specificity
Controlled oxygenated rewarming (COR)
Minor et al. (2013) [91]PigLiverIncrease from 4 to 20NA181.5Custodiol-N• COR significantly reduced cellular enzyme loss, gene expression, and tumor necrosis factor-alpha perfusate activities
• It also led to higher bile production, lower histological injury scores, and decreased caspase 3 activation compared to cold storage
Schopp et al. (2015) [31]PigKidneyIncrease from 4 to 20NA183Custodiol-N• COR led to a 2-fold increase in creatinine and urea clearances during warm reperfusion compared to controls, along with significant mitigation of postischemic mitochondrial dys-homeostasis
• COR also improved renal oxygen consumption, preserved total nicotinamide adenine dinucleotide tissue content, and largely prevented mitochondrial initiation of apoptosis, as indicated by reduced caspase 9 activation
Hoyer et al. (2016) [32]HumanLiverIncrease from 4 to 2018–336–151.5Custodiol-N• COR reduced peak serum transaminases by approximately 50% posttransplantation compared to untreated controls
• Graft survival after 6 months was 100% in the COR group versus 80.9% in controls, with patient survival at 100% in the COR group and 84.7% in controls
Minor et al. (2022) [44]HumanKidneyIncrease from 8 to 35NA122Steen solution, sodium bicarbonate, calcium gluconate, ampicillin• The kidney was transplanted without complications and showed good immediate function
• Serum creatinine decreased from 720 µmol/L preoperatively to 506 µmol/L within the first 24 hours, with a clearance of 43.1 mL/min after 1 week

NA, not available; ATP, adenosine triphosphate.



Table 2. Comparison of perfusion methods for organ preservation

MethodAdvantagesDisadvantagesPotential indicationsCosts
SCS• Widely adopted with well-defined protocols
• No complex machinery required; simple and inexpensive
• Reduced cellular metabolism
• Limited preservation time (12 hours in liver, 24 hours in kidney)
• Higher risk of ischemia-reperfusion injury and posttransplant complications
• Low-risk grafts with shorter transport timesLow
HMP• Reduces IRI
• Reduces cellular metabolism
• Oxygenation increases ATP generation
• High complexity
• Requires expertise and specialized ambulance for transportation
• High-risk grafts with longer transport times
• Ideal for DCD and ECD organs needing better preservation
Moderate
NMP• Reduces IRI
• Simulates physiological conditions
• Potential for metabolic recovery
• Allows functional evaluation of organs
• High complexity
• High cost of consumables and machinery
• Requires expertise and specialized ambulance for transportation
• Optimal for evaluating marginal organs
• Ideal for DCD and ECD organs needing better preservation
High
COR• Reduces IRI
• Minimizes reperfusion injury during temperature transition
• Allows functional evaluation of organs
• High complexity
• High cost of consumables and machinery
• Limited clinical data
• Emerging technique to optimize hypothermic preservation strategiesModerate
SNMP• Reduces IRI
• Potential for metabolic recovery
• Allows functional evaluation of organs
• Simple and cost-effective with no need for temperature control or whole blood
• Not as ideal as NMP for evaluating graft function
• Limited clinical data
• Emerging technique combining the advantages of HMP and NMPLow-moderate

SCS, static cold storage; HMP, hypothermic machine perfusion; IRI, ischemia-reperfusion injury; DCD, donation after circulatory death; ECD, extended criteria donor; NMP, normothermic machine perfusion; COR, controlled oxygenated rewarming; SNMP, subnormothermic machine perfusion.



Hypothermic Machine Perfusion

HMP is a technique that involves the continuous circulation of a cold perfusate through the organ's vasculature, typically within a temperature range of 2 °C to 10 °C (Fig. 2). HMP provides a multifaceted strategy for mitigating IRI [51]. During IRI, ischemia-induced cellular hypoxia activates hypoxia-inducible factor (HIF). Studies have shown that HMP can reduce HIF expression, which is associated with improved transplant outcomes [27,37]. Additionally, HMP has been demonstrated to mitigate IRI by reducing cell apoptosis in comparison to SCS [35,41,52]. This results in a reduction in the production of DAMPs, which in turn attenuates the proinflammatory cascade. Furthermore, studies have demonstrated that HMP improves endothelial function, which is linked to a reduction in immune cell transmigration [23,41]. The microvascular injury and endothelial dysfunction caused by IRI make the organ vulnerable to alloimmune damage; HMP helps counteract these effects by reducing their severity [81]. Furthermore, hypothermic oxygenated machine perfusion (HOPE) has shown additional benefits. HOPE helps restore cellular functions by rejuvenating mitochondria and restoring ATP levels [34]. Furthermore, it modifies the redox state of mitochondria by temporarily inhibiting oxidative metabolism, thereby reducing the initial release of ROS, and limiting tissue damage upon reperfusion [82,83].

Figure 2. Pictures of organ perfusion platforms: hypothermic, normothermic, and our lab’s innovations. (A) OrganOx Metra System: normothermic machine perfusion currently in clinical trials (with permission of OrganOx), (B) LifePort Liver Transporter: hypothermic machine perfusion currently in clinical trials (with permission of Organ Recovery Systems), and (C) BioCool Organ Preservation Machine: Hanyang’s Regenerative Medicine and Stem Cells institution hypothermic machine perfusion.

HMP has become the gold standard for high-risk donor kidney transplantation in many countries, supported by high-quality randomized clinical trials (RCTs) and meta-analyses [8486]. Currently, a prospective study is evaluating the potential of HOPE in kidney transplantation, which has shown promise in reducing posttransplant complications without significant costs [48]. Additionally, the noninferiority of end-ischemic HMP compared to full HMP is being investigated, due to the cost-effectiveness and simplicity of the former. However, the existing evidence does not support this hypothesis, and the studies are statistically underpowered [50,84].

The use of HMP in liver transplantation has only recently started to gain popularity, with the first successful application in a human liver reported in 2010 [24]. Unlike in kidney transplantation, end-ischemic HOPE has become the primary focus in liver transplantation studies. This focus is due to technological constraints that allow oxygenation only through a fixed, continuous source for a period of 1–2 hours during the recipient's hepatectomy [60,87]. A meta-analysis has shown that end-ischemic HOPE, compared to SCS, can reduce complications and improve graft survival in DCD and ECD liver transplantations [61,88]. However, the routine use of end-ischemic HOPE in donation after brain death (DBD) organs has not been recommended [59].

The existing literature on HMP in human heart transplantation is limited, with no RCTs currently available. In a study conducted by Nilsson et al. [47], the 6-month survival rates were 100% for the HOPE group and 72% for the SCS group, despite the latter experiencing longer preservation times. In another study, Andrijauskaite et al. [89] found that a 6-hour HOPE procedure significantly improved left ventricular relaxation compared to SCS, and was also associated with reduced inflammation markers. McGiffin et al. [90] reported that HOPE allows for the extension of preservation times to nearly 9 hours.

Subnormothermic Machine Perfusion

SNMP is conducted at approximately 20 ºC with oxygenated perfusate. Unlike NMP, SNMP simplifies the protocol by eliminating the need for temperature control and the use of donor blood or oxygen carriers, since the demand for tissue oxygenation is lower [26]. Additionally, reoxygenation without neutrophils and blood-derived inflammatory factors allows for a reduction in proinflammatory responses during reperfusion [58,92]. In this setting, with a moderate metabolic rate, it becomes feasible to conduct viability testing while controlling adverse cellular events.

A study comparing SNMP and NMP in porcine kidneys found that kidneys treated with SNMP were more susceptible to tubular and renal injuries, highlighting the need for an oxygen-carrier [93]. However, animal studies that compared SNMP with SCS for liver or kidney transplantation showed that SNMP could increase tissue ATP levels through mitochondrial resuscitation, reduce markers of tissue injury, and improve graft function after surgery [28,30,46,94]. When applied to discarded human livers, SNMP enhanced oxygen uptake, decreased lactate levels, and increased ATP following perfusion [29]. During the perfusion process, liver function was preserved, with an increase in bile production and improvements in bile composition noted. In research conducted by Abraham et al. [62] a discarded human kidney was perfused with SNMP for 24 hours, resulting in stable functional and biological parameters.

SNMP has been explored as an effective platform for delivering cytoprotective drugs, such as the hydrogen sulfide (H2S) donor AP29, when added to UW solution, compared to normothermic or hypothermic conditions [38,49]. In another study focusing on liver supercooling, SNMP was used to introduce 3-O-methylglucose (3-OMG) into hepatocytes [29]. This method was selected because 3-OMG is absorbed by hepatocytes through glucose transporter protein 1 (GLUT-1) and GLUT-2 transporters, requiring the use of SNMP while the hepatocytes are still metabolically active.

Normothermic Machine Perfusion

NMP enables an organ to sustain its physiological state by perfusing essential metabolic substrates with oxygen at body temperature (Fig. 2). This process supports cellular metabolism and ATP production, while also preventing ischemic changes. Numerous studies have demonstrated the safety and efficacy of this approach, which reduces IRI by mitigating inflammation and cell death, and by promoting tissue regeneration [15,36,42].

As NMP simulates physiological conditions, it enables the evaluation of graft viability and functionality in high risk, ECD organs of uncertain quality by assessing various markers [39,57,95]. If the organ meets the viability criteria, it is approved for transplantation; if not, it is either discarded or kept on NMP for further therapeutic interventions. Several regenerative strategies have been suggested as potential methods for repairing damaged livers during NMP. These include the use of senolytics, defatting cocktails, RNA interference, and stem cell therapy [54,55]. In conclusion, NMP serves as an effective platform for the reconditioning and enhancement of high-risk allografts, potentially rescuing organs that might otherwise be discarded.

For the kidney, Hosgood et al. [39] conducted the first RCT to compare 1-hour NMP before implantation with SCS in DCD organ transplantation. This multicenter RCT found no statistically significant differences in the incidence of DGF or complications between the two groups. The evaluation of the allocated kidneys was based on a scoring system that included urine output, renal blood flow, and macroscopic appearance. Nonrandomized and experimental studies have shown that kidneys subjected to end-ischemic NMP exhibit a lower incidence of DGF, minimal tubular injury, and enhanced metabolic function [35,41]. However, other studies on end-ischemic NMP have found no significant differences in outcomes compared to SCS [23,52].

The first report of NMP in human liver transplantation appeared in 2016 [33]. RCTs have shown that NMP leads to a 50% decrease in discard rates and a 20% increase in liver transplantations compared to SCS, by incorporating high-risk donors previously considered unsuitable [40,45]. A meta-analysis of NMP-RCTs demonstrated a statistically significant reduction in the incidence of NAS, major complications, and EAD [56,88,96]. However, NMP has not shown any significant benefits in terms of 1-year graft or patient survival.

A meta-analysis comparing NMP-DBD and NMP-DCD with SCS-DBD heart transplantation showed no significant differences in short- and long-term survival outcomes [53], indicating that NMP is a safe and effective strategy. The efficacy of NMP for DCD hearts and high-risk cases is further supported by the results of studies that have explored these issues [9799].

Controlled Rewarming and Mixed Perfusion Modalities

It has been demonstrated that exposing an organ stored at low temperatures to a sudden increase in temperature, either through NMP or reperfusion after transplantation, can cause mitochondrial dysfunction [80,91]. A potential solution to this problem is controlled oxygenated rewarming (COR) [43,91,100]. The COR technique involves oxygenated machine perfusion, where the temperature of the perfusate is gradually raised from hypothermia to subnormothermia or normothermia, facilitating a gentle and controlled rewarming process.

Minor et al. [91] compared COR with SCS, simple HMP, and SNMP in porcine livers. Following a viability assessment using NMP, COR significantly increased cellular ATP storage and decreased ROS production, hepatocellular necrosis, proinflammatory gene expression, and vascular resistance. These changes led to a substantial reduction in IRI. Another study on porcine kidneys showed that COR, compared to HMP, doubled the clearance rates of creatinine and urea, and improved renal oxygen consumption and mitochondrial functions [31]. The first clinical application of COR on a liver took place in 2014 [32]. The transplantation outcomes included a 50% reduction in peak serum transaminases compared to a historical cohort and showed 100% graft and patient survival. A case report on the first human kidney transplantation using COR to rewarm to 35 ºC indicated optimal immediate function and no complications, supporting its clinical use [44]. The first RCT focusing on COR in liver grafts demonstrated that COR significantly lowered 3-day postsurgery peak aspartate aminotransferase levels and major complications compared to SCS [100].

To minimize the duration of ischemia for organs, novel approaches such as ischemia-free liver transplantation are under investigation. This technique integrates normothermic regional perfusion with NMP, enabling the procurement, preservation, and implantation of livers while continuously providing normothermic, oxygenated blood. Studies have shown that this method offers significant advantages over SCS, including reductions in EAD, postreperfusion syndrome, NAS, and the comprehensive complication index at 1 year [101].

Cryopreservation is a biopreservation technique that involves storing biological samples at subzero temperatures. This method utilizes cryoprotective agents (CPAs) and controlled cooling techniques to preserve cellular viability and functionality [102]. The history of cryopreservation dates back to ancient civilizations, which utilized cold temperatures to preserve various items [103]. However, the modern era of cryopreservation began in 1948 when Polge and his colleagues discovered the cryoprotective properties of glycerol on fowl sperm [104]—a breakthrough that paved the way for preserving human red blood cells by 1950 [105]. This foundational discovery catalyzed the development of other effective cryoprotectants and significantly advanced biopreservation methods [106].

Unlike NMP, which is designed to maintain organ function by supporting metabolic activity, subzero preservation methods lower temperatures to induce metabolic depression, thereby extending the preservation period [45,107]. A 10 °C reduction in temperature has been shown to decrease metabolic activity by 50%, thus prolonging the preservation time [108]. Cryopreservation offers the possibility of storing biological samples indefinitely, depending on the techniques and conditions used [109]. Nonetheless, the process is intrinsically linked to the formation of ice, which can damage cells through extracellular or intracellular nucleation [110]. Typically, ice formation begins outside the cell, creating a hypertonic environment that draws water out and leads to dehydration (Fig. 3). Rapid cooling, in contrast, may cause intracellular ice formation, which is often fatal due to its potential to disrupt cell membranes and internal structures [111,112].

Figure 3. Schematic illustration of ice formation and cryoinjury. EC, extracellular; conc, concentration; IC, intracellular.

To mitigate ice-related cellular damage, researchers have developed two primary strategies based on the survival mechanisms of certain animals adapted to frigid climates: ice tolerance and ice avoidance [113,114]. Ice tolerance restricts ice formation to the extracellular space, thereby minimizing cellular dehydration, while ice avoidance aims to prevent ice formation altogether [115]. Both strategies extensively utilize CPAs, substances that protect biological specimens from the adverse effects of freezing and thawing [116]. CPAs are generally classified into two categories: permeable CPAs and nonpermeable CPAs [115]. Permeable CPAs, such as dimethyl sulfoxide, ethylene glycol, glycerol, and propylene glycol, can penetrate cell membranes, thus preventing excessive dehydration and reducing osmotic stress (Fig. 4). Nonpermeable CPAs, including sucrose, polyethylene glycol, glucan, albumin, and polyvinylpyrrolidone, remain outside the cells, minimizing ice formation in the extracellular space and reducing osmotic imbalances [117119].

Figure 4. Diagrammatic illustration of the role of cryoprotective agents (CPAs) in subzero preservation: permeable CPAs (pCPAs) and nonpermeable CPAs (npCPAs). EC, extracellular; IC, intracellular.

Cryopreservation is utilized across a broad spectrum of medical fields, including blood transfusion, regenerative medicine, research, and organ transplantation [120123]. It is particularly critical in organ preservation, where it facilitates long-distance transport and can extend the timeframe for organ matching and recovery, potentially allowing transplantation to become an elective procedure [124,125]. However, applying cryopreservation to larger, more complex structures like whole organs presents several challenges. One major issue is achieving uniform cooling and rewarming, especially in large tissues where uneven temperatures can cause localized ice formation. Additionally, reducing CPA toxicity and cryoinjury is crucial for maintaining cellular integrity [126128].

The categorization of subzero preservation techniques is a complex process. These techniques are divided into high subzero storage and low subzero storage based on temperature [129]. Additionally, cryopreservation techniques can be grouped into two categories according to their underlying mechanisms. These categories include ice-avoidance methods, such as supercooling, isochoric preservation, vitrification, and nanowarming, and ice-tolerance methods, such as partial freezing [130]. Fig. 5 illustrates the interrelationship between these two classification systems.

Figure 5. Classification of cryopreservation techniques by temperature and principle of ice preservation.

In the field of translational medicine, methods for avoiding ice formation have shown significant progress. These techniques have been successfully scaled up to human organs, and certain animal organs have been preserved for more than 3 months, yielding promising outcomes. The subsequent section offers a detailed analysis of the different preservation techniques (Table 3).

Table 3. Summary of subzero organ preservation methods and outcomes

StudyTypeOrganTemperature (°C)Perfusate solutionCPA/vitrification solutionStorage time (day)Result
Partial freezing
Tessier et al. (2022) [133]RatLiver–10 to –15UW, insulin, trehalose, dexamethasone, sodium bicarbonateGlycerol, antifreeze glycoprotein, polyvinyl alcohol/propylene glycol, X/Z-10001–5• Livers preserved with glycerol showed minimal DNA damage on TUNEL but had the lowest ATP levels, while those preserved with antifreeze glycoprotein and X/Z-1000 had high ATP levels but experienced endothelial cell damage
Tessier et al. (2022) [135]RatLiver–10 to –15UWPropylene glycol, glycerol, ethylene glycol, 3-OMG1–5• Livers preserved for 5 days with partial freezing had better outcomes than controls, despite lower bile and higher enzyme levels
• Propylene glycol also outperformed glycerol in preservation
Supercooling
Bruinsma et al. (2015) [152]RatLiver–6UW, insulin, dexamethasone, penicillin3-OMG, polyethylene glycol2–4• 3-month recipient survival was 100% for livers supercooled for 72 hours and 58% for those supercooled for 96 hours, tripling the 24-hour storage limit
• However, postoperative recovery took longer, with liver function normalizing within a month
de Vries et al. (2019) [153]HumanLiver–4UW, Trolox, insulin, dexamethasone, penicillinGlycerol, polyethylene glycol, trehalose1• Livers remain viable post-supercooling with no change in function or stress tolerance during simulated transplantation
• Key metrics, including bile levels, blood vessel resistance, oxygen uptake, and apoptotic cell levels, showed no significant differences from pre-supercooled livers
Isochoric
Wan et al. (2018) [154]RatHeart0 to –8UWNo CPA was used, constant volume was maintained in an isochoric chamber at 0.1–78 MPa1 hr• Hearts at –4 °C (41 MPa) showed similar histological injury to cold storage-preserved hearts but less interstitial edema, indicating better protection against vascular permeability
• At –6 °C (60 MPa), heartbeat activity decreased, and at –8 °C (78 MPa), hearts failed to beat
Botea et al. (2023) [155]PigLiver–2Custodial, normal salineNo CPA was used, constant volume was maintained in an isochoric chamber at –0.02 MPa1–2• Pig liver was successfully preserved ice-free for 2 days, and postthawing hematoxylin and eosin analysis showed normal appearance
• In contrast, livers frozen to –2 °C showed severe tissue disruption after 24 hours
Vitrification & nanowarming
Sharma et al. (2021) [156]RatKidney–150Euro-Collins100% VS55, 10 mg Fe/mL sIONPNA• Kidneys were vitrified without ice formation and successfully nanowarmed without devitrification or cracking
• Histology, confocal imaging, and viability assessments indicated superior outcomes compared to convective rewarming controls
Gao et al. (2022) [157]RatHeart–150Euro-Collins100% VS55, 10 mg Fe/mL sIONPNA• Successfully vitrified hearts were nanowarmed, displaying improved histology and endothelial integrity compared to convective rewarming, along with promising cardiac electrical activity
Sharma et al. (2023) [158]RatLiver–150Euro-CollinsEthylene glycol, sucrose, 10 mg Fe/mL sIONPNA• Liver retained intact architecture, normal bile ducts, and continuous epithelial layers, with preserved hepatocyte function and homogeneous perfusion
• Bile effluent volumes were comparable to the control group
Han et al. (2023) [159]RatKidney–150LM5, X-1000, Z-1000VMP, 10 mg Fe/mL sIONPUp to 100• Nanowarmed kidneys produced urine within 40–45 minutes following reperfusion
• A 30-day posttransplant follow-up showed normal creatinine, urea, and estimated glomerular filtration rate levels
• Histology revealed some focal tubular necrosis and hyaline changes, but basement membranes and vasculature remained intact

CPA, cryoprotective agent; UW, University of Wisconsin solution; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; ATP, adenosine triphosphate; 3-OMG, 3-O-methyl-d-glucose; sIONP, silica-coated iron oxide nanoparticles; NA, not available.


Partial Freezing

In the extreme cold of nature, where survival is a challenge for humans, the wood frog (Rana sylvatica) exhibits a remarkable adaptation to its environment [131]. This adaptation involves the controlled formation of ice within its nonvital organs, utilizing glucose products as natural CPAs and ice nucleating agents [132]. Partial freezing is a preservation method that controls both the rate and location of ice formation, while also maintaining enough unfrozen tissue to prevent ice-mediated injury. This technique is effective in high subzero temperatures, typically between –10 °C and –15 °C [133].

In a recent study, researchers utilized cryopreservation techniques, incorporating CPAs and ice nucleators, to store rat livers in a partially frozen state. Ice nucleators play a crucial role in controlling the freezing process, which significantly reduces the risk of lethal ice formation [134]. This method successfully extended the preservation time by a factor of five. Subsequent analysis after thawing indicated that propylene glycol led to the most favorable outcomes, compared to ethylene glycol and glycerol [135]. Although still in the early stages of development, partial freezing demonstrates significant potential as a method that aligns with natural processes rather than contradicting them.

Supercooling

Supercooling is a technique used in subzero organ preservation that cools biological materials below their freezing point without forming ice crystals [136,137]. This process typically occurs between –4 °C and –6 °C, although temperatures can drop to as low as –20 °C [138]. Supercooling reduces cryoinjury and allows for the use of lower concentrations of CPAs, thereby decreasing toxicity [139]. The method primarily aims to prevent heterogeneous ice nucleation, which necessitates nucleation sites such as impurities. Despite its benefits, supercooling is still susceptible to spontaneous ice crystallization due to stochastic nucleation events [140].

Two primary mechanisms of ice nucleation are observed in supercooling: heterogeneous and homogeneous [141]. Heterogeneous nucleation occurs in the presence of surfaces or particles, whereas homogeneous nucleation results from the spontaneous clustering of water molecules [142]. The main objective of the technique is to inhibit heterogeneous nucleation to broaden the supercooling range [143]. However, maintaining supercooling poses a challenge due to its inherent instability. To stabilize supercooling, researchers have introduced supercooling-promoting substances and have sealed the gas-liquid interface with oil. This approach allows for the storage of water at –20 °C for extended periods without the formation of ice [144,145].

Recent studies have highlighted the potential of supercooling in organ preservation. For example, rat hepatocytes demonstrated improved viability following storage through supercooling [146148], and this method preserved cortical bone allografts more effectively than conventional techniques [149]. Notably, supercooling also extended the storage time and enhanced posttransplant outcomes in organs such as porcine hindlimbs and murine hearts, compared to traditional preservation at 4 °C [150,151].

Pioneering work by Bruinsma et al. [152] demonstrated that rat livers could survive up to 4 days of supercooling, surpassing the results of HMP. The researchers used CPAs such as 3-O-methyl glucose and polyethylene glycol, along with a multistep perfusion strategy, achieving remarkable outcomes, including a 100% survival rate, posttransplant after 3 days [152]. Extending this technique to human livers, they successfully preserved organs for 27 hours at subzero temperatures by using additional CPAs like glycerol and trehalose, and by gradually introducing these agents to minimize osmotic injury [153].

Innovative supercooling methods, including the application of electric voltage, have shown promising results. Kuro et al. [160] successfully preserved rat femoral arteries at –2 °C using 1,000 V for 3 days, achieving favorable outcomes posttransplant. The use of voltage has also been explored in other organs, demonstrating reduced biomolecular markers and enhanced preservation outcomes compared to conventional cold storage [161]. These methods could potentially eliminate the need for CPAs, positioning supercooling as a viable alternative to existing preservation techniques.

While supercooling effectively prevents heterogeneous ice formation, it cannot inhibit homogeneous nucleation, which occurs around –20 °C [144,162]. Consequently, supercooling is not well-suited for long-term preservation but shows potential for facilitating global organ transport and short-term storage in transplantation settings.

Isochoric Preservation

Isochoric preservation is a technique used to protect biological specimens in an ice-free environment by applying pressure [163]. Also known as constant volume preservation, this method involves the use of a pressure chamber to monitor and apply pressure, effectively lowering the freezing point of water [164]. Ice formation causes an expansion that increases the pressure of the liquid inside the chamber, as ice has a larger molar volume than liquid water. This increased pressure further depresses the freezing point of the remaining liquid, allowing the specimen to be stored at lower temperatures without freezing [165,166].

This approach shares similarities with supercooling but distinguishes itself by using pressure instead of CPAs to prevent the formation of ice nuclei, thus avoiding CPA toxicity [167]. Wan et al. [154] found that rat hearts preserved at –4 °C (41 MPa) without CPAs had reduced interstitial edema, indicating better protection against increased vascular permeability compared to SCS. Pig livers were effectively preserved in a nonfreezing state for up to 48 hours in a pressure chamber, and subsequent analysis after warming showed that the tissue architecture remained intact [155]. Additionally, human cardiac tissue was successfully preserved at –3 °C without CPAs, with spontaneous contractility restored upon rewarming [168].

Isochoric preservation may be a highly effective method for organ preservation. However, Ueno et al. [169] demonstrated that hepatocytes experience pressure-dependent degeneration. Conversely, other experiments have shown that higher pressures are necessary to achieve further reductions in temperature [170]. Therefore, additional research is needed to find a balance between sustainable pressure levels and optimal temperature conditions.

Vitrification

Vitrification is a preservation technique in which biological samples are rapidly cooled, bypassing the crystallization phase to enter a glass-like, amorphous state [171]. In this state, the sample becomes highly viscous and molecular motion is nearly halted, effectively mimicking the properties of a solid [172]. Two critical parameters ensure successful vitrification: the critical cooling rate (CCR), which prevents ice formation during cooling, and the critical warming rate (CWR), which avoids devitrification during warming [173]. For water, the CCR is exceptionally high (greater than 107 °C/min), posing a challenge for biological specimens due to the practical limitations of achieving such rates [108]. To address this, CPAs are used to lower the CCR and help reach the glass transition temperature [174]. However, high concentrations of CPAs can be toxic, leading researchers to develop CPA cocktails that combine agents with different ice-inhibiting mechanisms to reduce toxicity [115].

Vitrification enables the long-term preservation of organs in liquid nitrogen by halting metabolic activity at extremely low temperatures. The foundational studies by Rall and Fahy [175] set the stage for this field, and Rall's [176] subsequent research marked a significant advancement, successfully vitrifying mouse embryos with an 80% survival rate upon rewarming. Since then, the scope of vitrification has broadened to include applications in reproductive medicine and organ preservation [177180]. For example, rat livers have been vitrified and demonstrated preserved tissue architecture after thawing [158], and small animal hearts and kidneys have also been successfully vitrified [156,181]. A notable achievement by Fahy’s team was the successful vitrification of a rabbit kidney, which functioned for 48 days posttransplant, despite challenges such as persistently elevated creatinine levels and lethargy [182]. This highlights the potential of vitrification for organ preservation.

The primary challenge in vitrification is the rewarming process, which necessitates precise control to prevent devitrification and ensure uniform heating [183]. Early methods, such as water baths, were ineffective, as they could not meet the required CWR and often induced thermal stress due to uneven heating. Additionally, the high CPA concentrations needed for both cooling and warming often led to cytotoxicity [184]. These issues have led researchers to investigate alternative rewarming techniques, including the use of radiation [185,186]. Electromagnetic fields, for instance, can provide a more uniform heat distribution [187]. Research in this field, including studies on microwave heating, has demonstrated potential [188190]. For instance, a study that involved rewarming dog kidneys frozen at –80 °C with microwaves reported a 50% survival rate over a period ranging from 2 to 14 months, though challenges related to organ shape and material properties persist [191].

Despite these advances, vitrification still faces technical challenges, particularly when applied to complex and irregularly shaped organs [156]. Achieving uniform rewarming and minimizing CPA toxicity remain key areas of ongoing research. As technology advances, vitrification shows promise in transforming organ preservation, potentially allowing for long-term storage and alleviating the time constraints that currently limit transplantation logistics.

Nanowarming

Nanowarming is a novel rewarming technology that employs radiofrequency (RF) coils to generate an alternating electromagnetic field, thereby causing preloaded nanomagnetic particles within the organ to oscillate [192]. The oscillation produces heat, ensuring the organ warms uniformly and reducing the thermomechanical stress that typically accompanies nonuniform warming. Additionally, this method reduces the risk of devitrification, as the frequency and strength of the field can be adjusted to surpass the CWR required by the organ [193]. The nanoparticles used in this process are made of elements with magnetic properties, such as iron, and are thus known as iron oxide nanoparticles (IONPs) [194]. Their colloidally stable nature facilitates efficient loading into the organ and subsequent removal through machine perfusion [195].

The successful nanowarming of tissues [196] and small animal organs [157,197] has yielded encouraging results. In a recent study, Han et al. [159] successfully transplanted a nanowarmed, vitrified rat kidney that had been preserved for 100 days. Before vitrification, the kidney was infused with 10 mg Fe/mL IONPs and then uniformly rewarmed using a 15 kW RF coil. After rewarming, the nanoparticles were removed through NMP. Following transplantation, the rats demonstrated adequate urine output and creatinine levels comparable to those of the control group, with no significant histological changes [159]. In comparison to the previously discussed vitrified rabbit kidney, the posttransplant outcomes were superior [182]. Given that vitrification is an isovolumetric process [108], it is theoretically scalable to human organs. Additionally, nanowarming technology is engineered to uniformly rewarm organs regardless of size. Successful integration of this system could significantly advance the long-sought goal of organ banking.

Subzero preservation methods are continuously evolving, and researchers are striving to make a clinical impact, yet significant advancements are still necessary. Currently, supercooling is at the forefront, having successfully preserved human livers. The primary advantage of supercooling is that it necessitates only minor modifications to existing hypothermic equipment, such as adding a chiller with an independent cooling system [152]. Additionally, the use of lower concentrations of CPAs diminishes the risk of CPA toxicity, a common issue with vitrification. However, supercooling presents challenges; it is unstable and requires meticulous monitoring to avoid lethal ice formation. While partial freezing is a strong contender, other methods lag significantly behind. Table 4 offers a detailed comparison of the advantages, disadvantages, and potential applications of each cryopreservation method.

Table 4. Comprehensive overview of cryopreservation methods: advantages, disadvantages, and potential indications for organ preservation

Cryopreservation methodAdvantagesDisadvantagesPotential indications
Partial freezing• Allows controlled ice formation to avoid lethal cellular damage
• Uses natural ice tolerance strategies
• Low cryoprotective agent toxicity
• Can be applied using currently available technology
• Risk of cellular dehydration and osmotic stress if not monitored correctly properly
• Not ideal for organs with complex vascular structures
• For short-term organ storage
• Useful for experimental studies on the effects of ice on organ preservation
Supercooling• Minimizes structural damage by avoiding ice and reduces the risk of ice formation from impurities
• Low cryoprotective agent toxicity
• Extends storage time compared to cold storage without additional sophisticated equipment
• Promising results have been shown in human organ research
• Prone to spontaneous ice formation
• Limited temperature range (–4 °C to –20 °C)
• Stability issues require constant monitoring
• Not suitable for long-term preservation
• Short-term organ storage
• Transport organs over moderate distances (intracontinental)
• This method has the potential to enable organ cryopreservation without the need for cryoprotective agents
Isochoric preservation• Utilizes pressure rather than cryoprotective agents, reducing toxicity risks
• Effective at maintaining ice-free conditions
• May be scalable with appropriate pressure control
• Specialized equipment is needed for constant pressure maintenance
• High-pressure requirements limit scalability to larger organs
• This method has the potential to enable organ cryopreservation without the need for cryoprotective agents
Vitrification & nanowarming• Bypasses ice formation
• Enables long-term storage
• Nanowarming provides uniform, rapid rewarming, reducing devitrification risk
• Supports preservation of complex organs with intricate structures
• Can be scaled to human-size organs
• High cryoprotective agent concentrations needed, risking cytotoxicity
• Requires loading of magnetic nanoparticles for nanowarming
• Specialized equipment with significant energy requirements
• Requires precise temperature control during both cooling and warming
• Long-term organ storage for potential organ banking
• Transport organs over long distances (intercontinental)
• Ideal for large organs and tissues needing uniform rewarming

Despite being one of the most significant advancements in healthcare over the past century, organ transplantation still fails to meet the needs of a considerable number of individuals. In 2022, the World Health Organization reported that only 10% of the global demand for organ transplants was met, highlighting the urgent need for advanced preservation strategies to improve transplant outcomes and increase the donor pool.

Recent advancements in organ preservation techniques, particularly in machine perfusion, have significantly advanced the field. Currently, the trend in organ preservation involves maintaining the organ close to its physiological temperature and supplying oxygen during perfusion, as illustrated in Fig. 1. Machine perfusion offers notable advantages over traditional SCS. HMP has now become the gold standard for preserving high-risk kidneys. It reduces IRI by maintaining cellular metabolism at lower temperatures and facilitating the removal of waste products. Additionally, the benefits of HOPE include rejuvenating mitochondrial function and minimizing oxidative stress, which together optimize preservation.

NMP provides the benefit of preserving organs at body temperature, which allows for real-time evaluation of organ function and viability. This method could potentially recondition organs from ECD or DCD, potentially reducing discard rates and expanding the donor pool. While more complex and expensive than SCS, NMP has shown significant benefits in liver transplantation, such as improved early graft function and decreased discard rates.

SNMP provides a balanced solution that reduces metabolic rates while maintaining cellular activity and repair mechanisms. This method streamlines the preservation process, extends preservation times, and enhances organ viability. By integrating COR into preservation protocols, it addresses temperature-induced mitochondrial dysfunction, thus minimizing IRI and improving posttransplant outcomes.

While the necessity for preservation techniques in living donors remains a topic of debate [198], there is some evidence supporting the potential benefits of machine perfusion in this context. Machine perfusion has demonstrated promising results, including improved preservation quality and enhanced transplant success rates. However, this approach is still under-researched, especially for living donors [199]. The current literature is limited, with much of the existing research focusing on organs from deceased donors. Consequently, a more comprehensive investigation into the applications and long-term effects of machine perfusion for living donor organs is crucial to fully realize its potential and optimize organ preservation methods.

Despite current limitations, such as ice formation and cellular damage, cryopreservation holds considerable promise for long-term organ storage. If cryopreservation techniques are successfully implemented, they could help mitigate the organ shortage crisis by allowing organs to be stored indefinitely and enabling more equitable distribution across various regions and over time.

Notwithstanding these advances, several challenges remain. Many conservative societies continue to overlook basic innovations like machine perfusion, often due to financial constraints, limited awareness, and a lack of respect for organ donation [200]. To overcome these obstacles, it is crucial for researchers, clinicians, industry stakeholders, and healthcare administrators to engage in enhanced collaboration.

This review has certain limitations, notably the omission of particular solid organs and vascularized composite allografts. Future research should aim to fill these gaps, thereby offering a more thorough understanding of the advancements and challenges in organ preservation. It is crucial to continue innovating and researching to broaden the donor pool, enhance transplant success rates, and ultimately save more lives.

Conflict of Interest

Kyeong Sik Kim is an associate editor, and Dongho Choi is the editor-in-chief of the journal. They were not involved in the peer reviewer selection, evaluation, or decision process of this article. No other potential conflict of interest relevant to this article was reported.

Funding/Support

This study was supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science and ICT (MSIT) of the Korean government. Numbers (2022R1A2C2004593, 2023R1A2C1005279).

  1. Nordham KD, Ninokawa S. The history of organ transplantation. Proc (Bayl Univ Med Cent) 2021;35:124-8.
    Pubmed KoreaMed CrossRef
  2. Colaneri J. An overview of transplant immunosuppression-history, principles, and current practices in kidney transplantation. Nephrol Nurs J 2014;41:549-60.
  3. Ploeg RJ. Kidney preservation with the UW and Euro-Collins solutions: a preliminary report of a clinical comparison. Transplantation 1990;49:281-4.
    Pubmed CrossRef
  4. Peters TG, Shaver TR, Ames JE 4th, Santiago-Delpin EA, Jones KW, Blanton JW. Cold ischemia and outcome in 17,937 cadaveric kidney transplants. Transplantation 1995;59:191-6.
    Pubmed CrossRef
  5. O'Callaghan JM, Morgan RD, Knight SR, Morris PJ. Systematic review and meta-analysis of hypothermic machine perfusion versus static cold storage of kidney allografts on transplant outcomes. Br J Surg 2013;100:991-1001.
    Pubmed CrossRef
  6. United Network for Organ Sharing (UNOS). Current state of organ donation and transplantation: transplant trends [Internet]. UNOS; 2024 [cited 2024 Jul 27].
    Available from: https://unos.org/.
  7. Health Resources and Services Administration (HRSA). Organ donation statistics [Internet]. HRSA; 2024 [cited 2024 Mar 31].
    Available from: https://www.organdonor.gov/learn/organ-donation-statistics.
  8. Statista. Number of people waiting for organ transplants in South Korea from 2019 to September 2023 [Internet]. Statista; 2023 [cited 2024 Sep 2].
    Available from: https://www.statista.com/statistics/1419295/south-korea-people-waiting-for-organ-transplants/.
  9. López-Navidad A, Caballero F. Extended criteria for organ acceptance: strategies for achieving organ safety and for increasing organ pool. Clin Transplant 2003;17:308-24.
    Pubmed CrossRef
  10. Fernández AR, Sánchez-Tarjuelo R, Cravedi P, Ochando J, López-Hoyos M. Review: ischemia reperfusion injury-a translational perspective in organ transplantation. Int J Mol Sci 2020;21:8549.
    Pubmed KoreaMed CrossRef
  11. Lurje I, Uluk D, Hammerich L, Pratschke J, Tacke F, Lurje G. Comparing hypothermic oxygenated and normothermic liver machine perfusion: translation matters. J Hepatol 2024;80:e163-5.
    Pubmed CrossRef
  12. Lee CY, Zhang JX, Jones JW Jr, Southard JH, Clemens MG. Functional recovery of preserved livers following warm ischemia: improvement by machine perfusion preservation. Transplantation 2002;74:944-51.
    Pubmed CrossRef
  13. Brasile L, Stubenitsky BM, Booster MH, Lindell S, Araneda D, Buck C, et al. Overcoming severe renal ischemia: the role of ex vivo warm perfusion. Transplantation 2002;73:897-901.
    Pubmed CrossRef
  14. Gok MA, Buckley PE, Shenton BK, Balupuri S, El-Sheikh MA, Robertson H, et al. Long-term renal function in kidneys from non-heart-beating donors: a single-center experience. Transplantation 2002;74:664-9.
    Pubmed CrossRef
  15. Schön MR, Kollmar O, Wolf S, Schrem H, Matthes M, Akkoc N, et al. Liver transplantation after organ preservation with normothermic extracorporeal perfusion. Ann Surg 2001;233:114-23.
    Pubmed KoreaMed CrossRef
  16. Bessems M, Doorschodt BM, van Marle J, Vreeling H, Meijer AJ, van Gulik TM. Improved machine perfusion preservation of the non-heart-beating donor rat liver using Polysol: a new machine perfusion preservation solution. Liver Transpl 2005;11:1379-88.
    Pubmed CrossRef
  17. Lindell SL, Compagnon P, Mangino MJ, Southard JH. UW solution for hypothermic machine perfusion of warm ischemic kidneys. Transplantation 2005;79:1358-61.
    Pubmed CrossRef
  18. Maathuis MH, Manekeller S, van der Plaats A, Leuvenink HG, 't Hart NA, Lier AB, et al. Improved kidney graft function after preservation using a novel hypothermic machine perfusion device. Ann Surg 2007;246:982-8.
    Pubmed CrossRef
  19. Sohrabi S, Navarro AP, Wilson C, Sanni A, Wyrley-Birch H, Anand DV, et al. Donation after cardiac death kidneys with low severity pre-arrest acute renal failure. Am J Transplant 2007;7:571-5.
    Pubmed CrossRef
  20. Xu H, Lee CY, Clemens MG, Zhang JX. Inhibition of TXA synthesis with OKY-046 improves liver preservation by prolonged hypothermic machine perfusion in rats. J Gastroenterol Hepatol 2008;23(7 Pt 2):e212-20.
    CrossRef
  21. Jain S, Lee SH, Korneszczuk K, Culberson CR, Southard JH, Berthiaume F, et al. Improved preservation of warm ischemic livers by hypothermic machine perfusion with supplemented University of Wisconsin solution. J Invest Surg 2008;21:83-91.
    Pubmed CrossRef
  22. Bagul A, Hosgood SA, Kaushik M, Kay MD, Waller HL, Nicholson ML. Experimental renal preservation by normothermic resuscitation perfusion with autologous blood. Br J Surg 2008;95:111-8.
    Pubmed CrossRef
  23. Hosgood SA, Yang B, Bagul A, Mohamed IH, Nicholson ML. A comparison of hypothermic machine perfusion versus static cold storage in an experimental model of renal ischemia reperfusion injury. Transplantation 2010;89:830-7.
    Pubmed CrossRef
  24. Guarrera JV, Henry SD, Samstein B, Odeh-Ramadan R, Kinkhabwala M, Goldstein MJ, et al. Hypothermic machine preservation in human liver transplantation: the first clinical series. Am J Transplant 2010;10:372-81.
    Pubmed CrossRef
  25. Berendsen TA, Bruinsma BG, Lee J, D'Andrea V, Liu Q, Izamis ML, et al. A simplified subnormothermic machine perfusion system restores ischemically damaged liver grafts in a rat model of orthotopic liver transplantation. Transplant Res 2012;1:6.
    Pubmed KoreaMed CrossRef
  26. Tolboom H, Izamis ML, Sharma N, Milwid JM, Uygun B, Berthiaume F, et al. Subnormothermic machine perfusion at both 20°C and 30°C recovers ischemic rat livers for successful transplantation. J Surg Res 2012;175:149-56.
    Pubmed KoreaMed CrossRef
  27. Henry SD, Nachber E, Tulipan J, Stone J, Bae C, Reznik L, et al. Hypothermic machine preservation reduces molecular markers of ischemia/reperfusion injury in human liver transplantation. Am J Transplant 2012;12:2477-86.
    Pubmed CrossRef
  28. Hoyer DP, Gallinat A, Swoboda S, Wohlschläger J, Rauen U, Paul A, et al. Subnormothermic machine perfusion for preservation of porcine kidneys in a donation after circulatory death model. Transpl Int 2014;27:1097-106.
    Pubmed CrossRef
  29. Bruinsma BG, Yeh H, Ozer S, Martins PN, Farmer A, Wu W, et al. Subnormothermic machine perfusion for ex vivo preservation and recovery of the human liver for transplantation. Am J Transplant 2014;14:1400-9.
    Pubmed KoreaMed CrossRef
  30. Fontes P, Lopez R, van der Plaats A, Vodovotz Y, Minervini M, Scott V, et al. Liver preservation with machine perfusion and a newly developed cell-free oxygen carrier solution under subnormothermic conditions. Am J Transplant 2015;15:381-94.
    Pubmed KoreaMed CrossRef
  31. Schopp I, Reissberg E, Lüer B, Efferz P, Minor T. Controlled rewarming after hypothermia: adding a new principle to renal preservation. Clin Transl Sci 2015;8:475-8.
    Pubmed KoreaMed CrossRef
  32. Hoyer DP, Mathé Z, Gallinat A, Canbay AC, Treckmann JW, Rauen U, et al. Controlled oxygenated rewarming of cold stored livers prior to transplantation: first clinical application of a new concept. Transplantation 2016;100:147-52.
    Pubmed CrossRef
  33. Ravikumar R, Jassem W, Mergental H, Heaton N, Mirza D, Perera MT, et al. Liver transplantation after ex vivo normothermic machine preservation: a phase 1 (first-in-man) clinical trial. Am J Transplant 2016;16:1779-87.
    Pubmed CrossRef
  34. Westerkamp AC, Karimian N, Matton AP, Mahboub P, van Rijn R, Wiersema-Buist J, et al. Oxygenated hypothermic machine perfusion after static cold storage improves hepatobiliary function of extended criteria donor livers. Transplantation 2016;100:825-35.
    Pubmed CrossRef
  35. Zhang Y, Fu Z, Zhong Z, Wang R, Hu L, Xiong Y, et al. Hypothermic machine perfusion decreases renal cell apoptosis during ischemia/reperfusion injury via the Ezrin/AKT pathway. Artif Organs 2016;40:129-35.
    Pubmed CrossRef
  36. Boteon YL, Laing R, Mergental H, Reynolds GM, Mirza DF, Afford SC, et al. Mechanisms of autophagy activation in endothelial cell and their targeting during normothermic machine liver perfusion. World J Gastroenterol 2017;23:8443-51.
    Pubmed KoreaMed CrossRef
  37. Zhao DF, Dong Q, Zhang T. Effects of static cold storage and hypothermic machine perfusion on oxidative stress factors, adhesion molecules, and zinc finger transcription factor proteins before and after liver transplantation. Ann Transplant 2017;22:96-100.
    Pubmed CrossRef
  38. Juriasingani S, Akbari M, Chan JY, Whiteman M, Sener A. H2S supplementation: a novel method for successful organ preservation at subnormothermic temperatures. Nitric Oxide 2018;81:57-66.
    Pubmed CrossRef
  39. Hosgood SA, Thompson E, Moore T, Wilson CH, Nicholson ML. Normothermic machine perfusion for the assessment and transplantation of declined human kidneys from donation after circulatory death donors. Br J Surg 2018;105:388-94.
    Pubmed KoreaMed CrossRef
  40. Nasralla D, Coussios CC, Mergental H, Akhtar MZ, Butler AJ, Ceresa CD, et al. A randomized trial of normothermic preservation in liver transplantation. Nature 2018;557:50-6.
    Pubmed CrossRef
  41. Zeng X, Li M, Fan X, Xue S, Liang W, Fang Z, et al. Hypothermic oxygenated machine perfusion alleviates donation after circulatory death liver injury through regulating p-selectin-dependent and -independent pathways in mice. Transplantation 2019;103:918-28.
    Pubmed CrossRef
  42. Jassem W, Xystrakis E, Ghnewa YG, Yuksel M, Pop O, Martinez-Llordella M, et al. Normothermic machine perfusion (NMP) inhibits proinflammatory responses in the liver and promotes regeneration. Hepatology 2019;70:682-95.
    Pubmed CrossRef
  43. Minor T, von Horn C. Rewarming injury after cold preservation. Int J Mol Sci 2019;20:2059.
    Pubmed KoreaMed CrossRef
  44. Minor T, von Horn C, Gallinat A, Kaths M, Kribben A, Treckmann J, et al. First-in-man controlled rewarming and normothermic perfusion with cell-free solution of a kidney prior to transplantation. Am J Transplant 2020;20:1192-5.
    Pubmed CrossRef
  45. Martins PN, Buchwald JE, Mergental H, Vargas L, Quintini C. The role of normothermic machine perfusion in liver transplantation. Int J Surg 2020;82S:52-60.
    Pubmed CrossRef
  46. Bhattacharjee RN, Patel SV, Sun Q, Jiang L, Richard-Mohamed M, Ruthirakanthan A, et al. Renal protection against ischemia reperfusion injury: hemoglobin-based oxygen carrier-201 versus blood as an oxygen carrier in ex vivo subnormothermic machine perfusion. Transplantation 2020;104:482-9.
    Pubmed CrossRef
  47. Nilsson J, Jernryd V, Qin G, Paskevicius A, Metzsch C, Sjöberg T, et al. A nonrandomized open-label phase 2 trial of nonischemic heart preservation for human heart transplantation. Nat Commun 2020;11:2976.
    Pubmed KoreaMed CrossRef
  48. Jochmans I, Brat A, Davies L, Hofker HS, van de Leemkolk FE, Leuvenink HG, et al. Oxygenated versus standard cold perfusion preservation in kidney transplantation (COMPARE): a randomised, double-blind, paired, phase 3 trial. Lancet 2020;396:1653-62.
    Pubmed CrossRef
  49. Juriasingani S, Ruthirakanthan A, Richard-Mohamed M, Akbari M, Aquil S, Patel S, et al. Subnormothermic perfusion with H2S donor AP39 improves DCD porcine renal graft outcomes in an ex vivo model of kidney preservation and reperfusion. Biomolecules 2021;11:446.
    Pubmed KoreaMed CrossRef
  50. Husen P, Boffa C, Jochmans I, Krikke C, Davies L, Mazilescu L, et al. Oxygenated end-hypothermic machine perfusion in expanded criteria donor kidney transplant: a randomized clinical trial. JAMA Surg 2021;156:517-25.
    Pubmed KoreaMed CrossRef
  51. Knijff LW, van Kooten C, Ploeg RJ. The effect of hypothermic machine perfusion to ameliorate ischemia-reperfusion injury in donor organs. Front Immunol 2022;13:848352.
    Pubmed KoreaMed CrossRef
  52. Faucher Q, Alarcan H, Sauvage FL, Forestier L, Miquelestorena-Standley E, Nadal-Desbarats L, et al. Perfusate metabolomics content and expression of tubular transporters during human kidney graft preservation by hypothermic machine perfusion. Transplantation 2022;106:1831-43.
    Pubmed CrossRef
  53. Langmuur SJ, Amesz JH, Veen KM, Bogers AJ, Manintveld OC, Taverne YJ. Normothermic ex situ heart perfusion with the organ care system for cardiac transplantation: a meta-analysis. Transplantation 2022;106:1745-53.
    Pubmed CrossRef
  54. Thompson ER, Sewpaul A, Figuereido R, Bates L, Tingle SJ, Ferdinand JR, et al. MicroRNA antagonist therapy during normothermic machine perfusion of donor kidneys. Am J Transplant 2022;22:1088-100.
    Pubmed CrossRef
  55. Lascaris B, de Meijer VE, Porte RJ. Normothermic liver machine perfusion as a dynamic platform for regenerative purposes: what does the future have in store for us? J Hepatol 2022;77:825-36.
    Pubmed CrossRef
  56. Olumba FC, Zhou F, Park Y, Chapman WC; RESTORE Investigators Group. Normothermic machine perfusion for declined livers: a strategy to rescue marginal livers for transplantation. J Am Coll Surg 2023;236:614-25.
    Pubmed CrossRef
  57. Li J, Lu H, Zhang J, Li Y, Zhao Q. Comprehensive approach to assessment of liver viability during normothermic machine perfusion. J Clin Transl Hepatol 2023;11:466-79.
  58. Kim J, Zimmerman MA, Shin WY, Boettcher BT, Lee JS, Park JI, et al. Effects of subnormothermic regulated hepatic reperfusion on mitochondrial and transcriptomic profiles in a porcine model. Ann Surg 2023;277:e366-75.
    Pubmed KoreaMed CrossRef
  59. Grąt M, Morawski M, Zhylko A, Rykowski P, Krasnodębski M, Wyporski A, et al. Routine end-ischemic hypothermic oxygenated machine perfusion in liver transplantation from donors after brain death: a randomized controlled trial. Ann Surg 2023;278:662-8.
    Pubmed CrossRef
  60. Panayotova GG, Lunsford KE, Quillin RC 3rd, Rana A, Agopian VG, Lee-Riddle GS, et al. Portable hypothermic oxygenated machine perfusion for organ preservation in liver transplantation: a randomized, open-label, clinical trial. Hepatology 2024;79:1033-47.
    Pubmed KoreaMed CrossRef
  61. Tang G, Zhang L, Xia L, Zhang J, Wei Z, Zhou R. Hypothermic oxygenated perfusion in liver transplantation: a meta-analysis of randomized controlled trials and matched studies. Int J Surg 2024;110:464-77.
    KoreaMed CrossRef
  62. Abraham N, Gao Q, Kahan R, Alderete IS, Wang B, Howell DN, et al. Subnormothermic oxygenated machine perfusion (24 h) in DCD kidney transplantation. Transplant Direct 2024;10:e1633.
    Pubmed KoreaMed CrossRef
  63. Kalogeris T, Baines CP, Krenz M, Korthuis RJ. Cell biology of ischemia/reperfusion injury. Int Rev Cell Mol Biol 2012;298:229-317.
    Pubmed KoreaMed CrossRef
  64. Zhai Y, Petrowsky H, Hong JC, Busuttil RW, Kupiec-Weglinski JW. Ischaemia-reperfusion injury in liver transplantation-from bench to bedside. Nat Rev Gastroenterol Hepatol 2013;10:79-89.
    Pubmed KoreaMed CrossRef
  65. Liang Y, Christopher K, Finn PW, Colson YL, Perkins DL. Graft produced interleukin-6 functions as a danger signal and promotes rejection after transplantation. Transplantation 2007;84:771-7.
    Pubmed CrossRef
  66. Nabi Z, Reddy DN. Endoscopic management of combined biliary and duodenal obstruction. Clin Endosc 2019;52:40-6.
    Pubmed KoreaMed CrossRef
  67. de Rougemont O, Dutkowski P, Clavien PA. Biological modulation of liver ischemia-reperfusion injury. Curr Opin Organ Transplant 2010;15:183-9.
    Pubmed CrossRef
  68. Nieuwenhuijs-Moeke GJ, Pischke SE, Berger SP, Sanders JS, Pol RA, Struys MM, et al. Ischemia and reperfusion injury in kidney transplantation: relevant mechanisms in injury and repair. J Clin Med 2020;9:253.
    Pubmed KoreaMed CrossRef
  69. Hausenloy DJ, Yellon DM. Myocardial ischemia-reperfusion injury: a neglected therapeutic target. J Clin Invest 2013;123:92-100.
    Pubmed KoreaMed CrossRef
  70. Gielis JF, Boulet GA, Briedé JJ, Horemans T, Debergh T, Kussé M, et al. Longitudinal quantification of radical bursts during pulmonary ischaemia and reperfusion. Eur J Cardiothorac Surg 2015;48:622-9.
    Pubmed CrossRef
  71. Collins GM, Bravo-Shugarman M, Terasaki PI. Kidney preservation for transportation: initial perfusion and 30 hours' ice storage. Lancet 1969;2:1219-22.
    Pubmed CrossRef
  72. Southard JH, Belzer FO. Organ preservation. Annu Rev Med 1995;46:235-47.
    Pubmed CrossRef
  73. Mühlbacher F, Langer F, Mittermayer C. Preservation solutions for transplantation. Transplant Proc 1999;31:2069-70.
    Pubmed CrossRef
  74. Stringham JC, Southard JH, Hegge J, Triemstra L, Fields BL, Belzer FO. Limitations of heart preservation by cold storage. Transplantation 1992;53:287-94.
    Pubmed CrossRef
  75. Paloyo S, Sageshima J, Gaynor JJ, Chen L, Ciancio G, Burke GW. Negative impact of prolonged cold storage time before machine perfusion preservation in donation after circulatory death kidney transplantation. Transpl Int 2016;29:1117-25.
    Pubmed CrossRef
  76. Pascual J, Zamora J, Pirsch JD. A systematic review of kidney transplantation from expanded criteria donors. Am J Kidney Dis 2008;52:553-86.
    Pubmed CrossRef
  77. Karangwa SA, Dutkowski P, Fontes P, Friend PJ, Guarrera JV, Markmann JF, et al. Machine perfusion of donor livers for transplantation: a proposal for standardized nomenclature and reporting guidelines. Am J Transplant 2016;16:2932-42.
    Pubmed KoreaMed CrossRef
  78. Radajewska A, Krzywonos-Zawadzka A, Bil-Lula I. Recent methods of kidney storage and therapeutic possibilities of transplant kidney. Biomedicines 2022;10:1013.
    Pubmed KoreaMed CrossRef
  79. Boteon YL, Afford SC. Machine perfusion of the liver: which is the best technique to mitigate ischaemia-reperfusion injury? World J Transplant 2019;9:14-20.
    Pubmed KoreaMed CrossRef
  80. van Leeuwen OB, Bodewes SB, Lantinga VA, Haring MP, Thorne AM, Brüggenwirth IM, et al. Sequential hypothermic and normothermic machine perfusion enables safe transplantation of high-risk donor livers. Am J Transplant 2022;22:1658-70.
    Pubmed KoreaMed CrossRef
  81. Cardinal H, Dieudé M, Hébert MJ. Endothelial dysfunction in kidney transplantation. Front Immunol 2018;9:1130.
    Pubmed KoreaMed CrossRef
  82. Schlegel A, de Rougemont O, Graf R, Clavien PA, Dutkowski P. Protective mechanisms of end-ischemic cold machine perfusion in DCD liver grafts. J Hepatol 2013;58:278-86.
    Pubmed CrossRef
  83. Chazelas P, Steichen C, Favreau F, Trouillas P, Hannaert P, Thuillier R, et al. Oxidative stress evaluation in ischemia reperfusion models: characteristics, limits and perspectives. Int J Mol Sci 2021;22:2366.
    Pubmed KoreaMed CrossRef
  84. Kang M, Kim S, Choi JY, Kim KS, Jung YK, Park B, et al. Ex vivo kidney machine perfusion: meta-analysis of randomized clinical trials. Br J Surg 2024;111:znae102.
    Pubmed CrossRef
  85. Moers C, Smits JM, Maathuis MH, Treckmann J, van Gelder F, Napieralski BP, et al. Machine perfusion or cold storage in deceased-donor kidney transplantation. N Engl J Med 2009;360:7-19.
    Pubmed CrossRef
  86. Malinoski D, Saunders C, Swain S, Groat T, Wood PR, Reese J, et al. Hypothermia or machine perfusion in kidney donors. N Engl J Med 2023;388:418-26.
    Pubmed CrossRef
  87. Panayotova GG, Rosado J, Paterno F, Deo D, Dikdan G, McCarty MA, et al. Novel oxygenation technique for hypothermic machine perfusion of liver grafts: validation in porcine donation after cardiac death (DCD) liver model. Am J Surg 2020;220:1270-7.
    Pubmed CrossRef
  88. Liang A, Cheng W, Cao P, Cai S, Zhang L, Zhong K, et al. Effects of machine perfusion strategies on different donor types in liver transplantation: a systematic review and meta-analysis. Int J Surg 2023;109:3617-30.
    Pubmed KoreaMed CrossRef
  89. Andrijauskaite K, Veraza RJ, Lopez RP, Maxwell Z, Cano I, Cisneros EE, et al. Novel portable hypothermic machine perfusion preservation device enhances cardiac viability of donated human hearts. Front Cardiovasc Med 2024;11:1376101.
    Pubmed KoreaMed CrossRef
  90. McGiffin DC, Kure CE, Macdonald PS, Jansz PC, Emmanuel S, Marasco SF, et al. Hypothermic oxygenated perfusion (HOPE) safely and effectively extends acceptable donor heart preservation times: results of the Australian and New Zealand trial. J Heart Lung Transplant 2024;43:485-95.
    Pubmed CrossRef
  91. Minor T, Efferz P, Fox M, Wohlschlaeger J, Lüer B. Controlled oxygenated rewarming of cold stored liver grafts by thermally graduated machine perfusion prior to reperfusion. Am J Transplant 2013;13:1450-60.
    Pubmed CrossRef
  92. Nicholson ML, Hosgood SA. Renal transplantation after ex vivo normothermic perfusion: the first clinical study. Am J Transplant 2013;13:1246-52.
    Pubmed CrossRef
  93. Adams TD, Patel M, Hosgood SA, Nicholson ML. Lowering perfusate temperature from 37°c to 32°c diminishes function in a porcine model of ex vivo kidney perfusion. Transplant Direct 2017;3:e140.
    Pubmed KoreaMed CrossRef
  94. Berendsen TA, Bruinsma BG, Lee J, D'Andrea V, Liu Q, Izamis ML, et al. A simplified subnormothermic machine perfusion system restores ischemically damaged liver grafts in a rat model of orthotopic liver transplantation. Transplant Res 2012;1:6.
    Pubmed KoreaMed CrossRef
  95. Bona M, Wyss RK, Arnold M, Méndez-Carmona N, Sanz MN, Günsch D, et al. Cardiac graft assessment in the era of machine perfusion: current and future biomarkers. J Am Heart Assoc 2021;10:e018966.
    Pubmed KoreaMed CrossRef
  96. Parente A, Tirotta F, Pini A, Eden J, Dondossola D, Manzia TM, et al. Machine perfusion techniques for liver transplantation - a meta-analysis of the first seven randomized-controlled trials. J Hepatol 2023;79:1201-13.
    Pubmed CrossRef
  97. García Sáez D, Zych B, Sabashnikov A, Bowles CT, De Robertis F, Mohite PN, et al. Evaluation of the organ care system in heart transplantation with an adverse donor/recipient profile. Ann Thorac Surg 2014;98:2099-105.
    Pubmed CrossRef
  98. Sponga S, Vendramin I, Salman J, Ferrara V, De Manna ND, Lechiancole A, et al. Heart transplantation in high-risk recipients employing donor marginal grafts preserved with ex-vivo perfusion. Transpl Int 2023;36:11089.
    Pubmed KoreaMed CrossRef
  99. Sponga S, Bonetti A, Ferrara V, Beltrami AP, Isola M, Vendramin I, et al. Preservation by cold storage vs ex vivo normothermic perfusion of marginal donor hearts: clinical, histopathologic, and ultrastructural features. J Heart Lung Transplant 2020;39:1408-16.
    Pubmed CrossRef
  100. Minor T, von Horn C, Zlatev H, Saner F, Grawe M, Lüer B, et al. Controlled oxygenated rewarming as novel end-ischemic therapy for cold stored liver grafts: a randomized controlled trial. Clin Transl Sci 2022;15:2918-27.
    Pubmed KoreaMed CrossRef
  101. Guo Z, Zhao Q, Jia Z, Huang C, Wang D, Ju W, et al. A randomized-controlled trial of ischemia-free liver transplantation for end-stage liver disease. J Hepatol 2023;79:394-402.
    Pubmed CrossRef
  102. Pegg DE. Principles of cryopreservation. In: Wolkers WF, Oldenhof H, editors. Cryopreservation and freeze-drying protocols. Springer; 2015. p. 3–19.
  103. Love R. Chillin' at the symposium with Plato: refrigeration in the ancient world. ASHRAE Trans 2009;115:106.
  104. Polge C, Smith AU, Parkes AS. Revival of spermatozoa after vitrification and dehydration at low temperatures. Nature 1949;164:666.
    Pubmed CrossRef
  105. Smith AU. Prevention of haemolysis during freezing and thawing of red blood- cells. Lancet 1950;2:910-1.
    Pubmed CrossRef
  106. Lovelock JE, Bishop MW. Prevention of freezing damage to living cells by dimethyl sulphoxide. Nature 1959;183:1394-5.
    Pubmed CrossRef
  107. Toledo-Pereyra LH, Gordon DA, MacKenzie GH. Current research review: organ freezing. J Surg Res 1982;32:75-84.
    Pubmed CrossRef
  108. Finger EB, Bischof JC. Cryopreservation by vitrification: a promising approach for transplant organ banking. Curr Opin Organ Transplant 2018;23:35-60.
    Pubmed CrossRef
  109. Pullen LC. Supercooling halts biological time: new technologies can multiply the number of hours that an organ remains viable for transplant. Am J Transplant 2023;23:1473-5.
    Pubmed CrossRef
  110. Lin M, Cao H, Li J. Control strategies of ice nucleation, growth, and recrystallization for cryopreservation. Acta Biomater 2023;155:35-56.
    Pubmed CrossRef
  111. Jaiswal AN, Vagga A. Cryopreservation: a review article. Cureus 2022;14:e31564.
    CrossRef
  112. Zhao G, Luo D, Gao D. Universal model for intracellular ice formation and its growth. AIChE J 2006;52:2596-606.
    CrossRef
  113. Schmid WD. Survival of frogs in low temperature. Science 1982;215:697-8.
    Pubmed CrossRef
  114. Baust JG, Brown RT. Heterothermy and cold acclimation in the arctic ground squirrel, Citellus undulatus. Comp Biochem Physiol A Physiol 1980;67:447-52.
    CrossRef
  115. Bojic S, Murray A, Bentley BL, Spindler R, Pawlik P, Cordeiro JL, et al. Winter is coming: the future of cryopreservation. BMC Biol 2021;19:56.
    Pubmed KoreaMed CrossRef
  116. Pegg DE. Principles of cryopreservation. Methods Mol Biol 2007;368:39-57.
    Pubmed CrossRef
  117. Elliott GD, Wang S, Fuller BJ. Cryoprotectants: a review of the actions and applications of cryoprotective solutes that modulate cell recovery from ultra-low temperatures. Cryobiology 2017;76:74-91.
    Pubmed CrossRef
  118. Guo N, Wei Q, Xu Y. Optimization of cryopreservation of pathogenic microbial strains. J Biosaf Biosecur 2020;2:66-70.
    CrossRef
  119. Karow AM Jr. Cryoprotectants-a new class of drugs. J Pharm Pharmacol 1969;21:209-23.
    Pubmed CrossRef
  120. Trounson AO. Cryopreservation. Br Med Bull 1990;46:695-708.
    Pubmed CrossRef
  121. Arutyunyan I, Fatkhudinov T, Sukhikh G. Umbilical cord tissue cryopreservation: a short review. Stem Cell Res Ther 2018;9:236.
    Pubmed KoreaMed CrossRef
  122. Brandstadter JD, De Martin A, Lϋtge M, Ferreira A, Gaudette BT, Stanossek Y, et al. A novel cryopreservation and biobanking strategy to study lymphoid tissue stromal cells in human disease. Eur J Immunol 2023;53:e2250362.
    Pubmed KoreaMed CrossRef
  123. Gal S, Pu LL. An update on cryopreservation of adipose tissue. Plast Reconstr Surg 2020;145:1089-97.
    Pubmed CrossRef
  124. Liu D, Pan F. Advances in cryopreservation of organs. J Huazhong Univ Sci Technolog Med Sci 2016;36:153-61.
    Pubmed CrossRef
  125. Mazur P. Freezing of living cells: mechanisms and implications. Am J Physiol 1984;247(3 Pt 1):C125-42.
    Pubmed CrossRef
  126. Pegg DE. The relevance of ice crystal formation for the cryopreservation of tissues and organs. Cryobiology 2010;60(3 Suppl):S36-44.
    Pubmed CrossRef
  127. Steponkus PL. Advances in low-temperature biology. Elsevier; 1996.
  128. Whaley D, Damyar K, Witek RP, Mendoza A, Alexander M, Lakey JR. Cryopreservation: an overview of principles and cell-specific considerations. Cell Transplant 2021;30:963689721999617.
    Pubmed KoreaMed CrossRef
  129. Ozgur OS, Namsrai BE, Pruett TL, Bischof JC, Toner M, Finger EB, et al. Current practice and novel approaches in organ preservation. Front Transplant 2023;2:1156845.
    Pubmed KoreaMed CrossRef
  130. Bruinsma BG, Uygun K. Subzero organ preservation: the dawn of a new ice age? Curr Opin Organ Transplant 2017;22:281-6.
    Pubmed KoreaMed CrossRef
  131. Costanzo JP, Reynolds AM, do Amaral MC, Rosendale AJ, Lee RE Jr. Cryoprotectants and extreme freeze tolerance in a subarctic population of the wood frog. PLoS One 2015;10:e0117234.
    Pubmed KoreaMed CrossRef
  132. Storey KB, Storey JM. Biochemical adaption for freezing tolerance in the wood frog, Rana sylvatica. J Comp Physiol B 1984;155:29-36.
    CrossRef
  133. Tessier SN, Haque O, Pendexter CA, Cronin SE, Hafiz EOA, Weng L, et al. The role of antifreeze glycoprotein (AFGP) and polyvinyl alcohol/polyglycerol (X/Z-1000) as ice modulators during partial freezing of rat livers. Front Phys 2022;10:1033613.
    Pubmed KoreaMed CrossRef
  134. Melnik BS, Glukhova KA, Sokolova Voronova EA, Balalaeva IV, Garbuzynskiy SO, Finkelstein AV. Physics of ice nucleation and antinucleation: action of ice-binding proteins. Biomolecules 2023;14:54.
    Pubmed KoreaMed CrossRef
  135. Tessier SN, de Vries RJ, Pendexter CA, Cronin SE, Ozer S, Hafiz EO, et al. Partial freezing of rat livers extends preservation time by 5-fold. Nat Commun 2022;13:4008.
    Pubmed KoreaMed CrossRef
  136. Sultana T, Lee JI, Park JH, Lee S. Supercooling storage for the transplantable sources from the rat and the rabbit: a preliminary report. Transplant Proc 2018;50:1178-82.
    Pubmed CrossRef
  137. Basco MT, Yiu WK, Cheng SW, Sumpio BE. The effects of freezing versus supercooling on vascular cells: implications for balloon cryoplasty. J Vasc Interv Radiol 2010;21:910-5.
    Pubmed KoreaMed CrossRef
  138. Abe M, Jimi S, Hama H, Shiraishi T, Iwasaki A, Ono N, et al. A novel method for preserving human lungs using a super-cooling system. Ann Thorac Surg 2006;82:1085-8.
    Pubmed CrossRef
  139. Berendsen TA, Bruinsma BG, Puts CF, Saeidi N, Usta OB, Uygun BE, et al. Supercooling enables long-term transplantation survival following 4 days of liver preservation. Nat Med 2014;20:790-3.
    Pubmed KoreaMed CrossRef
  140. Zhmakin AI. Fundamentals of cryobiology: physical phenomena and mathematical models. Springer; 2009.
    CrossRef
  141. Morris GJ, Acton E. Controlled ice nucleation in cryopreservation-a review. Cryobiology 2013;66:85-92.
    Pubmed CrossRef
  142. William N, Acker JP. High sub-zero organ preservation: a paradigm of nature-inspired strategies. Cryobiology 2021;102:15-26.
    Pubmed CrossRef
  143. Prickett RC, Marquez-Curtis LA, Elliott JA, McGann LE. Effect of supercooling and cell volume on intracellular ice formation. Cryobiology 2015;70:156-63.
    Pubmed CrossRef
  144. Fujikawa S, Kuwabara C, Kasuga J, Arakawa K. Supercooling-promoting (anti-ice nucleation) substances. Adv Exp Med Biol 2018;1081:289-320.
    Pubmed CrossRef
  145. Huang H, Yarmush ML, Usta OB. Long-term deep-supercooling of large-volume water and red cell suspensions via surface sealing with immiscible liquids. Nat Commun 2018;9:3201.
    Pubmed KoreaMed CrossRef
  146. Usta OB, Kim Y, Ozer S, Bruinsma BG, Lee J, Demir E, et al. Supercooling as a viable non-freezing cell preservation method of rat hepatocytes. PLoS One 2013;8:e69334.
    Pubmed KoreaMed CrossRef
  147. Scotte M, Eschwege P, Cherruau C, Fontaliran F, Moreau F, Houssin D. Liver preservation below 0 degrees C with UW solution and 2,3-butanediol. Cryobiology 1996;33:54-61.
    Pubmed CrossRef
  148. Matsuda H, Yagi T, Matsuoka J, Yamamura H, Tanaka N. Subzero nonfreezing storage of isolated rat hepatocytes in University of Wisconsin solution. Transplantation 1999;67:186-91.
    Pubmed CrossRef
  149. Kim M, Yoon HY. The biomechanical and biological effect of supercooling on cortical bone allograft. J Vet Sci 2023;24:e79.
    Pubmed KoreaMed CrossRef
  150. Berkane Y, Filz von Reiterdank I, Tawa P, Charlès L, Goutard M, Dinicu AT, et al. VCA supercooling in a swine partial hindlimb model. Sci Rep 2024;14:12618.
    Pubmed KoreaMed CrossRef
  151. Que W, Hu X, Fujino M, Terayama H, Sakabe K, Fukunishi N, et al. Prolonged cold ischemia time in mouse heart transplantation using supercooling preservation. Transplantation 2020;104:1879-89.
    Pubmed CrossRef
  152. Bruinsma BG, Berendsen TA, Izamis ML, Yeh H, Yarmush ML, Uygun K. Supercooling preservation and transplantation of the rat liver. Nat Protoc 2015;10:484-94.
    Pubmed KoreaMed CrossRef
  153. de Vries RJ, Tessier SN, Banik PD, Nagpal S, Cronin SE, Ozer S, et al. Supercooling extends preservation time of human livers. Nat Biotechnol 2019;37:1131-6.
    Pubmed KoreaMed CrossRef
  154. Wan L, Powell-Palm MJ, Lee C, Gupta A, Weegman BP, Clemens MG, et al. Preservation of rat hearts in subfreezing temperature isochoric conditions to - 8 °C and 78 MPa. Biochem Biophys Res Commun 2018;496:852-7.
    Pubmed CrossRef
  155. Botea F, Năstase G, Herlea V, Chang TT, Șerban A, Barcu A, et al. An exploratory study on isochoric supercooling preservation of the pig liver. Biochem Biophys Rep 2023;34:101485.
    Pubmed KoreaMed CrossRef
  156. Sharma A, Rao JS, Han Z, Gangwar L, Namsrai B, Gao Z, et al. Vitrification and nanowarming of kidneys. Adv Sci (Weinh) 2021;8:e2101691.
    Pubmed KoreaMed CrossRef
  157. Gao Z, Namsrai B, Han Z, Joshi P, Rao JS, Ravikumar V, et al. Vitrification and rewarming of magnetic nanoparticle-loaded rat hearts. Adv Mater Technol 2022;7:2100873.
    Pubmed KoreaMed CrossRef
  158. Sharma A, Lee CY, Namsrai BE, Han Z, Tobolt D, Rao JS, et al. Cryopreservation of whole rat livers by vitrification and nanowarming. Ann Biomed Eng 2023;51:566-77.
    Pubmed KoreaMed CrossRef
  159. Han Z, Rao JS, Gangwar L, Namsrai BE, Pasek-Allen JL, Etheridge ML, et al. Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model. Nat Commun 2023;14:3407.
    Pubmed KoreaMed CrossRef
  160. Kuro A, Morimoto N, Hara T, Matsuoka Y, Fukui M, Hihara M, et al. Protection of rat artery grafts from tissue damage by voltage-applied supercooling. Med Mol Morphol 2022;55:91-9.
    Pubmed CrossRef
  161. Monzen K, Hosoda T, Hayashi D, Imai Y, Okawa Y, Kohro T, et al. The use of a supercooling refrigerator improves the preservation of organ grafts. Biochem Biophys Res Commun 2005;337:534-9.
    Pubmed CrossRef
  162. Sanz E, Vega C, Espinosa JR, Caballero-Bernal R, Abascal JL, Valeriani C. Homogeneous ice nucleation at moderate supercooling from molecular simulation. J Am Chem Soc 2013;135:15008-17.
    Pubmed CrossRef
  163. Takahashi T, Kakita A, Takahashi Y, Yokoyama K, Sakamoto I, Yamashina S. Preservation of rat livers by supercooling under high pressure. Transplant Proc 2001;33:916-9.
    Pubmed CrossRef
  164. Preciado JA, Rubinsky B. Isochoric preservation: a novel characterization method. Cryobiology 2010;60:23-9.
    Pubmed CrossRef
  165. Powell-Palm MJ, Koh-Bell A, Rubinsky B. Isochoric conditions enhance stability of metastable supercooled water. Appl Phys Lett 2020;116:123702.
    CrossRef
  166. Consiglio A, Ukpai G, Rubinsky B, Powell-Palm MJ. Suppression of cavitation-induced nucleation in systems under isochoric confinement. Phys Rev Res 2020;2:023350.
    CrossRef
  167. Năstase G, Botea F, Beșchea GA, Câmpean ȘI, Barcu A, Neacșu I, et al. Isochoric supercooling organ preservation system. Bioengineering (Basel) 2023;10:934.
    Pubmed KoreaMed CrossRef
  168. Powell-Palm MJ, Charwat V, Charrez B, Siemons B, Healy KE, Rubinsky B. Isochoric supercooled preservation and revival of human cardiac microtissues. Commun Biol 2021;4:1118.
    Pubmed KoreaMed CrossRef
  169. Ueno T, Omura T, Takahashi T, Matsumoto H, Takahashi Y, Kakita A, et al. Liver transplantation using liver grafts preserved under high pressure. Artif Organs 2005;29:849-55.
    Pubmed CrossRef
  170. Ukpai G, Năstase G, Șerban A, Rubinsky B. Pressure in isochoric systems containing aqueous solutions at subzero Centigrade temperatures. PLoS One 2017;12:e0183353.
    Pubmed KoreaMed CrossRef
  171. Armitage WJ, Rich SJ. Vitrification of organized tissues. Cryobiology 1990;27:483-91.
    Pubmed CrossRef
  172. Fuller BJ, Lane N, Benson EE. Life in the frozen state. CRC press; 2004.
    CrossRef
  173. Fahy GM, MacFarlane DR, Angell CA, Meryman HT. Vitrification as an approach to cryopreservation. Cryobiology 1984;21:407-26.
    Pubmed CrossRef
  174. Fahy GM, Wowk B, Wu J, Paynter S. Improved vitrification solutions based on the predictability of vitrification solution toxicity. Cryobiology 2004;48:22-35.
    Pubmed CrossRef
  175. Rall WF, Fahy GM. Ice-free cryopreservation of mouse embryos at -196 degrees C by vitrification. Nature 1985;313:573-5.
    Pubmed CrossRef
  176. Rall WF. Factors affecting the survival of mouse embryos cryopreserved by vitrification. Cryobiology 1987;24:387-402.
    Pubmed CrossRef
  177. Amorim CA, Curaba M, Van Langendonckt A, Dolmans MM, Donnez J. Vitrification as an alternative means of cryopreserving ovarian tissue. Reprod Biomed Online 2011;23:160-86.
    Pubmed CrossRef
  178. Yagoub SH, Lim M, Tan TC, Chow DJ, Dholakia K, Gibson BC, et al. Vitrification within a nanoliter volume: oocyte and embryo cryopreservation within a 3D photopolymerized device. J Assist Reprod Genet 2022;39:1997-2014.
    CrossRef
  179. Canosa S, Cimadomo D, Conforti A, Maggiulli R, Giancani A, Tallarita A, et al. The effect of extended cryo-storage following vitrification on embryo competence: a systematic review and meta-analysis. J Assist Reprod Genet 2022;39:873-82.
    Pubmed KoreaMed CrossRef
  180. Schulz M, Risopatrón J, Uribe P, Isachenko E, Isachenko V, Sánchez R. Human sperm vitrification: a scientific report. Andrology 2020;8:1642-50.
    Pubmed CrossRef
  181. Brockbank KG, Chen Z, Greene ED, Campbell LH. Vitrification of heart valve tissues. Methods Mol Biol 2015;1257:399-421.
    Pubmed KoreaMed CrossRef
  182. Fahy GM, Wowk B, Pagotan R, Chang A, Phan J, Thomson B, et al. Physical and biological aspects of renal vitrification. Organogenesis 2009;5:167-75.
    Pubmed KoreaMed CrossRef
  183. Fahy GM, Wowk B, Wu J, Phan J, Rasch C, Chang A, et al. Cryopreservation of organs by vitrification: perspectives and recent advances. Cryobiology 2004;48:157-78.
    Pubmed CrossRef
  184. Best BP. Cryoprotectant toxicity: facts, issues, and questions. Rejuvenation Res 2015;18:422-36.
    Pubmed KoreaMed CrossRef
  185. Diller KR. Modeling of bioheat transfer processes at high and low temperatures. In: Cho YI, editor. Advances in heat transfer. Elsevier; 1992. p. 157–357.
    CrossRef
  186. Karow AM. Electronic techniques for controlling thawing of major organs. Cryobiology 1984;21:403-6.
    Pubmed CrossRef
  187. Lovelock JE, Smith AU. Heat transfer from and to animals in experimental hypothermia and freezing. Ann N Y Acad Sci 1959;80:487-99.
    Pubmed CrossRef
  188. Goldzveig SA, Smith AU. A simple method for reanimating ice-cold rats and mice. J Physiol 1956;132:406-13.
    Pubmed KoreaMed CrossRef
  189. Burns CP, Burdett EC, Karow AM. Thawing of rabbit kidneys from −79 °C with 2450 MHz radiation. Cryobiology 1975;12:577.
    CrossRef
  190. Burdette EC, Wiggins S, Brown R, Karow AM Jr. Microwave thawing of frozen kidneys: a theoretically based experimentally-effective design. Cryobiology 1980;17:393-402.
    Pubmed CrossRef
  191. Guttman FM, Lizin J, Robitaille P, Blanchard H, Turgeon-Knaack C. Survival of canine kidneys after treatment with dimethyl-sulfoxide, freezing at -80 degrees C, and thawing by microwave illumination. Cryobiology 1977;14:559-67.
    Pubmed CrossRef
  192. Chen P, Wang S, Chen Z, Ren P, Hepfer RG, Greene ED, et al. Nanowarming and ice-free cryopreservation of large sized, intact porcine articular cartilage. Commun Biol 2023;6:220.
    Pubmed KoreaMed CrossRef
  193. Bischof J. Nanowarming: a new concept in tissue and organ preservation. Cryobiology 2015;71:176.
    CrossRef
  194. Ye Z, Liu S, Yin Y. Magnetic nanoparticles for nanowarming: seeking a fine balance between heating performance and biocompatibility. Mater Chem Front 2023;7:3427-33.
    CrossRef
  195. Gao Z, Ring HL, Sharma A, Namsrai B, Tran N, Finger EB, et al. Preparation of scalable silica-coated iron oxide nanoparticles for nanowarming. Adv Sci (Weinh) 2020;7:1901624.
    Pubmed KoreaMed CrossRef
  196. Manuchehrabadi N, Gao Z, Zhang J, Ring HL, Shao Q, Liu F, et al. Improved tissue cryopreservation using inductive heating of magnetic nanoparticles. Sci Transl Med 2017;9:eaah4586.
    Pubmed KoreaMed CrossRef
  197. Chiu-Lam A, Staples E, Pepine CJ, Rinaldi C. Perfusion, cryopreservation, and nanowarming of whole hearts using colloidally stable magnetic cryopreservation agent solutions. Sci Adv 2021;7:eabe3005.
    Pubmed KoreaMed CrossRef
  198. Dogar AW, Ullah K, Shams-Ud-Din, Abbas SH, Hussain A, Ghaffar A, et al. Is a preservation solution for living donor liver transplantation needed? Adding a new chapter in LDLT!. Transplant Direct 2022;8:e1396.
    Pubmed KoreaMed CrossRef
  199. Moser MA, Ginther N, Luo Y, Beck G, Ginther R, Ewen M, et al. Early experience with hypothermic machine perfusion of living donor kidneys - a retrospective study. Transpl Int 2017;30:706-12.
    Pubmed CrossRef
  200. Flores Carvalho M, Boteon YL, Guarrera JV, Modi PR, Lladó L, Lurje G, et al. Obstacles to implement machine perfusion technology in routine clinical practice of transplantation: why are we not there yet? Hepatology 2024;79:713-30.
    Pubmed CrossRef