Preservation Strategies for Vascularized Composite Allotransplantation: An Updated Systematic Review of a Rapidly Expanding Field.

The effect on early renal function of various dynamic preservation strategies in a preclinical pig ischemia-reperfusion autotransplant model.

Randomized evaluation of comparative effects of optimized static cold storage, hypothermic and normothermic machine perfusion, and colchicine pretreatment on ischemia-reperfusion injury in a porcine model.

Introduction Continuous and end ischemic preservation strategies (hypothermic machine perfusion (HMP) and normothermic perfusion (NP)) have demonstrated improved early graft function compared to static cold storage (SCS) alone. The aim of this study was to evaluate the impact of several machine perfusion variables (oxygen, temperature as well as timing to start perfusion) on early graft function in a porcine auto-transplant model. Materials and Methods The left kidney of a ±40 kg female Landrace pig was exposed to 30 minutes of warm ischemia by vascular clamping and randomized after standard procurement and ex vivo donor blood flush out to one of 6 studied preservation strategies: 1) 22hrs SCS, 2) 22hrs HMP, 3) 22hrs oxygenated HMP, 4) 20hrs HMP + 2hrs NP, 5) 20hrs SCS + 2hrs oxygenated HMP, and 6) 20hrs SCS + 2hrs NP. The LifePort Kidney Transporter® (Organ Recovery Systems) was used for all machine perfusion strategies. The left kidney was auto-transplanted in a right orthotopic position. The primary and secondary endpoints were kidney function and physical parameters during machine perfusion, respectively. Results Thirty-seven auto-transplants were performed with a minimum of 6 pigs per study group. Serum creatinine at day 3 after transplantation was significantly lower both in the 22hrs oxygenated (p=0.0011) and non-oxygenated HMP (p=0.0116) group compared to 22hrs of SCS but no treatment effect could be demonstrated between these 2 HMP groups (p=0.3622) at day 3 (figure 1). End ischemic strategies could not be demonstrated a statistical significant treatment benefice on early graft function compared to SCS (figure 2).From 8 to 19 hours on machine perfusion the renal blood flow (RBF) was significantly higher in the continuous oxygenated compared to the non-oxygenated HMP group. However RBF at the end of machine perfusion was comparable between these 2 groups (figure 3) (p=0.0812). NP results in the highest RBF when performed after HMP (p<0.0001) but no difference in RBF was observed between oxygenated HMPO2/NP after SCS (p=0.31) (figure 4). Discussion Graft recovery from ischemia reperfusion injury was significantly better using continuous HMP strategies compared to end ischemic machine perfusion strategies. Continuous oxygenated HMP demonstrated a faster increase of ex vivo RBF compared to non-oxygenated HMP and better initial graft function, especially during the first week after transplantation.Conclusions In this study, hypothermic perfusion strategies only when applied from time of kidney procurement until transplantation and irrespective of supplemental oxygenation, led to a positive effect on early graft function. Continuous oxygenated HMP preservation demonstrated a faster increase of RBF compared to non-oxygenated HMP but without any effect on graft recovery. Further studies are needed to evaluate the effect of oxygen pressure during HMP. Organ Recovery Systems. Astellas.

Despite the annual rise in patients with end-stage diseases necessitating organ transplantation, the scarcity of high-quality grafts constrains the further development of transplantation. The primary causes of the graft shortage are the scarcity of standard criteria donors, unsatisfactory organ preservation strategies, and mismatching issues. Organ preservation strategies are intimately related to pre-transplant graft viability and the incidence of adverse clinical outcomes. Static cold storage (SCS) is the current standard practice of organ preservation, characterized by its cost-effectiveness, ease of transport, and excellent clinical outcomes. However, cold-induced injury during static cold preservation, toxicity of organ preservation solution components, and post-transplantation reperfusion injury could further exacerbate graft damage. Long-term ex vivo dynamic machine perfusion (MP) preserves grafts in a near-physiological condition, evaluates graft viability, and cures damage to grafts, hence enhancing the usage and survival rates of marginal organs. With the increased use of extended criteria donors (ECD) and advancements in machine perfusion technology, static cold storage is being gradually replaced by machine perfusion. This review encapsulates the latest developments in cryopreservation, subzero non-freezing storage, static cold storage, and machine perfusion. The emphasis is on the injury mechanisms linked to static cold storage and optimization strategies, which may serve as references for the optimization of machine perfusion techniques.

Liver transplantation is the only chance of cure for people with end-stage liver disease and some people with advanced liver cancers or acute liver failure. The increasing prevalence of these conditions drives demand and necessitates the increasing use of donated livers which have traditionally been considered suboptimal. Several novel machine perfusion preservation technologies have been developed, which attempt to ameliorate some of the deleterious effects of ischaemia reperfusion injury. Machine perfusion technology aims to improve organ quality, thereby improving outcomes in recipients of suboptimal livers when compared to traditional static cold storage (SCS; ice box). To evaluate the effects of different methods of machine perfusion (including hypothermic oxygenated machine perfusion (HOPE), normothermic machine perfusion (NMP), controlled oxygenated rewarming, and normothermic regional perfusion) versus each other or versus static cold storage (SCS) in people undergoing liver transplantation. We used standard, extensive Cochrane search methods. The latest search date was 10 January 2023. We included randomised clinical trials which compared different methods of machine perfusion, either with each other or with SCS. Studies comparing HOPE via both hepatic artery and portal vein, or via portal vein only, were grouped. The protocol detailed that we also planned to include quasi-randomised studies to assess treatment harms. We used standard Cochrane methods. Our primary outcomes were 1. overall participant survival, 2. quality of life, and 3. serious adverse events. Secondary outcomes were 4. graft survival, 5. ischaemic biliary complications, 6. primary non-function of the graft, 7. early allograft function, 8. non-serious adverse events, 9. transplant utilisation, and 10. transaminase release during the first week post-transplant. We assessed bias using Cochrane's RoB 2 tool and used GRADE to assess certainty of evidence. We included seven randomised trials (1024 transplant recipients from 1301 randomised/included livers). All trials were parallel two-group trials; four compared HOPE versus SCS, and three compared NMP versus SCS. No trials used normothermic regional perfusion. When compared with SCS, it was uncertain whether overall participant survival was improved with either HOPE (hazard ratio (HR) 0.91, 95% confidence interval (CI) 0.42 to 1.98; P = 0.81, I2 = 0%; 4 trials, 482 recipients; low-certainty evidence due to imprecision because of low number of events) or NMP (HR 1.08, 95% CI 0.31 to 3.80; P = 0.90; 1 trial, 222 recipients; very low-certainty evidence due to imprecision and risk of bias). No trials reported quality of life. When compared with SCS alone, HOPE was associated with improvement in the following clinically relevant outcomes: graft survival (HR 0.45, 95% CI 0.23 to 0.87; P = 0.02, I2 = 0%; 4 trials, 482 recipients; high-certainty evidence), serious adverse events in extended criteria DBD liver transplants (OR 0.45, 95% CI 0.22 to 0.91; P = 0.03, I2 = 0%; 2 trials, 156 participants; moderate-certainty evidence) and clinically significant ischaemic cholangiopathy in recipients of DCD livers (OR 0.31, 95% CI 0.11 to 0.92; P = 0.03; 1 trial, 156 recipients; high-certainty evidence). In contrast, NMP was not associated with improvement in any of these clinically relevant outcomes. NMP was associated with improved utilisation compared with SCS (one trial found a 50% lower rate of organ discard; P = 0.008), but the reasons underlying this effect are unknown. We identified 11 ongoing studies investigating machine perfusion technologies. In situations where the decision has been made to transplant a liver donated after circulatory death or donated following brain death, end-ischaemic HOPE will provide superior clinically relevant outcomes compared with SCS alone. Specifically, graft survival is improved (high-certainty evidence), serious adverse events are reduced (moderate-certainty evidence), and in donors after circulatory death, clinically relevant ischaemic biliary complications are reduced (high-certainty evidence). There is no good evidence that NMP has the same benefits over SCS in terms of these clinically relevant outcomes. NMP does appear to improve utilisation of grafts that would otherwise be discarded with SCS; however, the reasons for this, and whether this effect is specific to NMP, is not clear. Further studies into NMP viability criteria and utilisation, as well as head-to-head trials with other perfusion technologies are needed. In the setting of donation following circulatory death transplantation, further trials are needed to assess the effect of these ex situ machine perfusion methods against, or in combination with, normothermic regional perfusion.

Mesenchymal stromal cell treatment of donor kidneys during ex vivo normothermic machine perfusion: A porcine renal autotransplantation study.

Oxygen Consumption by Warm Ischemia-Injured Porcine Kidneys in Hypothermic Static and Machine Preservation

Strategies in Organ Preservation-A New Golden Age.

Better preservation strategies for the storage of donation after circulatory death grafts are essential to improve graft function and to increase the kidney donor pool. We compared continuous normothermic ex vivo kidney perfusion (NEVKP) with hypothermic anoxic machine perfusion (HAMP) and static cold storage (SCS) in a porcine kidney autotransplantation model. Porcine kidneys were exposed to 30 minutes of warm ischemia and then reimplanted following either 16 hours of either SCS, HAMP (LifePort 1.0), or NEVKP before autotransplantation (n = 5 per group). The contralateral kidney was removed. Animals were followed for 8 days. Grafts preserved by NEVKP demonstrated improved function with more rapid recovery compared with HAMP and SCS (mean peak serum creatinine: 3.66 ± 1.33 mg/dL [postoperative d 1 [(POD1)], 8.82 ± 3.17 mg/dL [POD2], and 12.90 ± 2.19 mg/dL [POD3], respectively). The NEVKP group demonstrated significantly increased creatinine clearance calculated on POD3 (63.6 ± 19.0 mL/min) compared with HAMP (13.5 ± 10.3 mL/min, P = 0.001) and SCS (4.0 ± 2.6 mL/min, P = 0.001). Histopathologic injury scores on POD8 were lower in both perfused groups (NEVKP and HAMP, score: 1-1.5) compared with SCS (score: 1-3, P = 0.3), without reaching statistical significance. NEVKP storage significantly improved early kidney function compared with both cold preservation strategies, although HAMP also demonstrates improvement over SCS. NEVKP may represent a novel, superior preservation option for donation after circulatory death renal grafts compared with conventional hypothermic methods.

Kidney transplantation is the optimal treatment for end-stage kidney disease. Retrieval, transport and transplant of kidney grafts causes ischaemia reperfusion injury. The current accepted standard is static cold storage (SCS) whereby the kidney is stored on ice after removal from the donor and then removed from the ice box at the time of implantation. However, technology is now available to perfuse or "pump" the kidney during the transport phase or at the recipient centre. This can be done at a variety of temperatures and using different perfusates. The effectiveness of treatment is manifest clinically as delayed graft function (DGF), whereby the kidney fails to produce urine immediately after transplant. To compare hypothermic machine perfusion (HMP) and (sub)normothermic machine perfusion (NMP) with standard SCS. We searched the Cochrane Kidney and Transplant Register of Studies to 18 October 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. All randomised controlled trials (RCTs) and quasi-RCTs comparing HMP/NMP versus SCS for deceased donor kidney transplantation were eligible for inclusion. All donor types were included (donor after circulatory (DCD) and brainstem death (DBD), standard and extended/expanded criteria donors). Both paired and unpaired studies were eligible for inclusion. The results of the literature search were screened and a standard data extraction form was used to collect data. Both of these steps were performed by two independent authors. Dichotomous outcome results were expressed as risk ratio (RR) with 95% confidence intervals (CI). Continuous scales of measurement were expressed as a mean difference (MD). Random effects models were used for data analysis. The primary outcome was incidence of DGF. Secondary outcomes included: one-year graft survival, incidence of primary non-function (PNF), DGF duration, long term graft survival, economic implications, graft function, patient survival and incidence of acute rejection. No studies reported on NMP, however one ongoing study was identified.Sixteen studies (2266 participants) comparing HMP with SCS were included; 15 studies could be meta-analysed. Fourteen studies reported on requirement for dialysis in the first week post-transplant (DGF incidence); there is high-certainty evidence that HMP reduces the risk of DGF when compared to SCS (RR 0.77; 95% CI 0.67 to 0.90; P = 0.0006). HMP reduces the risk of DGF in kidneys from DCD donors (7 studies, 772 participants: RR 0.75; 95% CI 0.64 to 0.87; P = 0.0002; high certainty evidence), as well as kidneys from DBD donors (4 studies, 971 participants: RR 0.78, 95% CI 0.65 to 0.93; P = 0.006; high certainty evidence). The number of perfusions required to prevent one episode of DGF (number needed to treat, NNT) was 7.26 and 13.60 in DCD and DBD kidneys respectively. Studies performed in the last decade all used the LifePort machine and confirmed that HMP reduces the incidence of DGF in the modern era (5 studies, 1355 participants: RR 0.77, 95% CI 0.66 to 0.91; P = 0.002; high certainty evidence). Reports of economic analysis suggest that HMP can lead to cost savings in both the North American and European settings.Two studies reported HMP also improves graft survival however we were not able to meta-analyse these results. A reduction in incidence of PNF could not be demonstrated. The effect of HMP on our other outcomes (incidence of acute rejection, patient survival, hospital stay, long-term graft function, duration of DGF) remains uncertain. HMP is superior to SCS in deceased donor kidney transplantation. This is true for both DBD and DCD kidneys, and remains true in the modern era (studies performed in the last decade). As kidneys from DCD donors have a higher overall DGF rate, fewer perfusions are needed to prevent one episode of DGF (7.26 versus 13.60 in DBD kidneys).Further studies looking solely at the impact of HMP on DGF incidence are not required. Follow-up reports detailing long-term graft survival from participants of the studies already included in this review would be an efficient way to generate further long-term graft survival data.Economic analysis, based on the results of this review, would help cement HMP as the standard preservation method in deceased donor kidney transplantation.RCTs investigating (sub)NMP are required.

Introduction: There is renewed interest in Hypothermic Machine Perfusion (HMP) of kidneys in recent years with the development of a new generation of pumps. However, it remains controversial which method is most beneficial for the transplant recipient. A systematic review of the level of available evidence comparing HMP with SCS and a statistical analysis of the combined data was performed. Methods: A systematic literature search was performed using MEDLINE (1948 to October 2011), EMBASE (1980 to October 2011), the Cochrane Library, the Transplant Library of RCTs from the Centre for Evidence in Transplantation and the International Clinical Trials Registry Platform. Studies were assessed for methodological quality. Summary effects of meta-analysis are presented as Relative Risks (RR) and 95% Confidence Intervals (95%CI). RCTs alone were used for meta-analysis. Results: Nineteen studies met the full inclusion criteria, including 7 RCTs and 12 Non-RCTS with a total of 2,086 kidneys. The overall risk of Delayed Graft Function (DGF) was lower with HMP than with SCS (fixed effects, RR=0.81, 95%CI=0.70-0.92, p< 0.01). DGF was not significantly reduced when results were split into DBD kidneys (fixed effects, RR=0.84, 95%CI=0.68-1.04, p=0.10) and DCD kidneys (fixed effects, RR=0.80, (95%CI=0.62-1.04, p=0.09). There was no evidence that the effect on DGF comparing these two donor types was significantly different (Test of Interaction, p=0.78). There was no difference in the risk of graft loss within the first 12 months (fixed effects, RR=0.86, 95%CI=0.68-1.09, p=0.22) or the rate of Primary Non-Function (PNF) between HMP and SCS kidneys (random effects, RR=1.16, 95%CI=0.46-2.94, p=0.75). Three studies found a faster fall in serum creatinine for HMP preserved kidneys in the first 14 days; however 3 studies found no significant difference in longer term renal function (30-365 days). Rates of acute rejection were equal in 2 studies, although higher following SCS in 1 study. In the 7 studies that reported patient survival there was no relationship between preservation method and this outcome. Conclusion: Data from the included studies shows that HMP reduces DGF compared to SCS. This effect may be the same in both DBD and DCD kidneys. HMP may lead to a quicker reduction in serum creatinine post-op. There was no difference in graft loss in the first 12 months, PNF, long term renal function, acute rejection or patient survival. Figure: Forest plot to show RR of DGF comparing hypothermic machine perfusion (HMP) to static cold storage (SCS) in randomised controlled trials. N= total patients in study arm, n= number of patients with DGF. Summary RR calculated by fixed effects meta-analysis, < 1 Favours HMP. 95%CI=95% confidence interval.Figure: [Forest plot to show relative risk (RR) of DGF.]

Introduction: Liver transplantation remains the definitive treatment for end-stage liver disease but faces critical challenges including organ shortages and preservation difficulties, particularly with extended criteria donor (ECD) grafts. Hypothermic machine perfusion (HMP) represents a promising alternative to traditional static cold storage (SCS). Methods: This retrospective study analyzed outcomes from 62 liver transplant recipients between 2016 and 2025, comparing 8 grafts preserved by HMP using the Liver Assist® system and 54 grafts preserved by SCS. Parameters assessed included postoperative complications, hemodynamic stability, ischemia times, and survival outcomes. Results: HMP significantly reduced surgical (0% vs. 75.9%, p = 0.01) and biliary complications (0% vs. 34.4%, p = 0.004), improved hemodynamic stability post-reperfusion (∆MAP%: 1 vs. 21, p = 0.006), and achieved superior one-year survival rates (100% vs. 84.4%). Despite longer ischemia periods, grafts treated with HMP exhibited fewer adverse effects from ischemia-reperfusion injury. Discussion: These findings highlight the substantial benefits of HMP, particularly in improving graft quality from marginal donors and reducing postoperative morbidity. Further adoption of this technology could significantly impact liver transplantation outcomes by expanding the viable donor pool. Conclusions: The study underscores the effectiveness of hypothermic machine perfusion (HMP) as a superior preservation method compared to traditional static cold storage (SCS), HMP appears to be associated with improved short-term outcomes in liver transplantation. By substantially reducing postoperative complications and enhancing graft viability, HMP emerges as a pivotal strategy for maximizing the use of marginal donor organs. Further research and broader clinical implementation are recommended to validate these promising results and to fully harness the potential of HMP in liver transplantation.

Heart transplantation in donation after circulatory death (DCD) relies on warm perfusion using either in situ normothermic regional perfusion (NRP) or ex situ normothermic machine perfusion. In this study, we explore an alternative: oxygenated hypothermic machine perfusion (HMP) using a novel clinically applicable perfusion system, which is compared to NRP with static cold storage (SCS). In a porcine model, a DCD setting was simulated, followed by either (1) NRP and SCS (2) NRP and HMP with the XVIVO Heart preservation system or (3) direct procurement (DPP) and HMP. After preservation, heart transplantation (HTX) was performed. After weaning from cardiopulmonary bypass (CPB), biventricular function was assessed by admittance and Swan-Ganz catheters. Only transplanted hearts in the HMP groups showed significantly increased biventricular contractility (end-systole elastance) 2 hour post-CPB (left ventricle absolute change: NRP HMP: +1.8 ± 0.56, p=0.047, DPP HMP: +1.5 ± 0.43, p=0.045 and NRP SCS: +0.97 ± 0.47 mmHg/ml, p=0.21; right ventricle absolute change: NRP HMP: +0.50 ± 0.12, p=0.025, DPP HMP: +0.82 ± 0.23, p=0.039 and NRP SCS: +0.28 ± 0.26, p=0.52) while receiving significantly less dobutamine to maintain a cardiac output >4l/min compared to SCS. Diastolic function was preserved in all groups. Post-HTX, both HMP groups showed significantly less increments in plasma troponin T compared to SCS. In DCD HTX, increased biventricular contractility post-HTX was only observed in hearts preserved with HMP. In addition, the need for inotropic support and signs of myocardial damage were lower in the HMP groups. DCD HTX can be successfully performed using DPP followed by preservation with HMP in a preclinical setting.

Vascularized composite allotransplantation (VCA) offers unparalleled reconstructive possibilities in complex cases but remains constrained by high immunogenicity and marked susceptibility to ischemia-reperfusion injury (IRI), particularly in muscle-rich grafts. Static cold storage (SCS), the current clinical standard, preserves grafts only for short durations. In contrast, machine perfusion (MP), already transformative in solid organ transplantation, is emerging as a promising strategy for VCA. This review summarizes the main challenges of exvivo VCA preservation and current perfusion strategies designed to overcome them. Particular attention is given to physiological and technical factors influencing graft integrity, as well as innovations in perfusate composition and protective additives that mitigate IRI and support tissue preservation. Beyond simple storage, MP platforms enable functional assessment and therapeutic interventions, including graft reconditioning and immune modulation prior to transplantation. Complementary subzero static preservation methods, such as supercooling and cryopreservation, also show promise for substantially extending preservation times. Together with advances in experimental models, these approaches are reshaping the preservation landscape. As the field evolves, MP is poised to become a cornerstone technology in VCA, improving graft quality, extending preservation duration, and enabling pre-implantation modification strategies to reduce rejection and enhance long-term outcomes.

Introduction Ischaemia-reperfusion injury (IRI) is inevitable in transplantation. Necroptosis is a form of cell death in kidney IRI and phosphorylation of RIPK1 plays a key role in this pathway. This study investigated the effectiveness of delivering GNE684 -a RIPK1 kinase inhibitor- during static cold storage (SCS) and hypothermic machine perfusion (HMP) in an ex-vivo model of kidney IRI. Methods Pig kidneys underwent 1h warm ischaemia and were retrieved. In the SCS model, kidney pairs (n=6) were randomised to treatment with UW+GNE684 via the renal artery (5µM) or control. Kidneys underwent 7h SCS in UW±GNE684 followed by 4h ex-vivo normothermic reperfusion with whole blood (NR). In the HMP model, kidney pairs (n=6) were randomised to HMP alone or treatment with UW-MPS+GNE684 (5µM) for 12h followed by 8h NR. Results In both SCS and HMP groups increasing levels of cytokines and injury markers (e.g. LDH, AST, IL-6) were observed without significant differences between control and treatment groups. HMP led to higher GNE684 tissue concentrations post preservation compared to SCS (3143±385.9 vs 1036.22±453.49ng/ml;P&amp;lt;0.0001) and during NR (987.5±507.6 vs 213.7±37.37ng/ml at t=4h;P=0.013) and levels stayed steady until t=8h NR. GNE684 in both models reduced pRIPK1 at 1h NR but the effect persisted at 4h NR in the HMP model. Discussion This study showed the superiority of HMP over SCS as a delivery method of GNE684 to ischaemically injured pig kidneys. GNE684 did not have marked effects on inflammation or IRI but did inhibit RIPK1 activation in the necroptosis pathway.