Outcomes of donation after circulatory death kidneys undergoing hypothermic machine perfusion following static cold storage: A UK population-based cohort study

Hypothermic Oxygenated Perfusion in Extended Criteria Donor Kidney Transplantation-A Randomized Clinical Trial

BACKGROUND

The role of machine perfusion after kidney transplantation (KT) in extended criteria donors (ECD) is unclear, and the current evidence in the literature remains controversial.

METHODS

We present an open-label single center randomized trial where 109 patients undergoing KT with ECD grafts between January 2019 and December 2022 were randomized to receive kidneys treated with either hypothermic oxygenated perfusion (HOPE, n = 54) or static cold storage (SCS, n = 55) alone. The primary endpoint was the incidence of delayed graft function (DGF). The secondary endpoints included postoperative complications and graft function and survival in the first year after KT.

RESULTS

The trial failed to meet its primary endpoint. DGF developed in 31 (57%) and 37 (67%) patients in the HOPE and SCS groups, respectively (p = 0.3). Posthoc analysis showed that HOPE was associated with a lower risk for DGF for grafts from donors aged 60 years or older (OR 0.32, 95% CI 0.12-0.87, p = 0.026) and in patients undergoing dual KTs (OR 0.22, 95% CI 0.06-0.87, p = 0.031).

CONCLUSIONS

HOPE does not reduce the rate of DGF after KT in ECD donors. However, HOPE appears to be associated with better outcomes in the case of older donors and dual KTs.

Metabolic Characterization of Deceased Donor Kidneys Undergoing Hypothermic Machine Perfusion Before Transplantation Using 13C-enriched Glucose

BACKGROUND

The provision of a metabolic substrate is one mechanism by which hypothermic machine perfusion (HMP) of kidneys provides clinical benefit. This study aimed to describe de novo metabolism in ex vivo human kidneys undergoing HMP before transplantation using 13C-labeled glucose as a metabolic tracer.

METHODS

Cadaveric human kidneys were perfused with modified clinical-grade perfusion fluid (kidney perfusion solution [KPS-1], Organ Recovery Systems), in which glucose was uniformly enriched with the stable isotope 13C ([U-13C] glucose). The sampled perfusion fluid was analyzed using a blood gas analyzer, and metabolic profiling was performed using 1-dimensional and 2-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. Functional outcome measures included serum creatinine levels and the development of delayed graft function.

RESULTS

Fourteen kidneys were perfused with the modified KPS-1 and successfully transplanted. The mean duration of HMP was 8.7 h. There was a sustained increase in the conversion of glucose into de novo glycolytic end products, such as lactate, in donor kidneys during HMP. There was no significant association between functional outcomes and metabolism during the HMP. De novo anaerobic metabolism was indicated by continuing lactate production, as indicated by increasing concentrations of universally 13C-labeled lactate ([U-13C] lactate) in perfusion fluid from all kidneys. This was more evident in donation after circulatory death donor kidneys.

CONCLUSIONS

Our study is the first to use [U-13C] glucose to describe the metabolism during HMP. The consequences of an initial warm ischemic insult on circulatory death in donor kidneys continue during the preservation period.

Developing an Injury-Free 15 Hour Preservation Protocol of Donor Porcine Kidneys Using Normothermic Machine Perfusion

Normothermic machine perfusion (NMP) offers a superior alternative to hypothermic preservation but is currently time limited. Extending this time could electivise transplantation and enable physiologic assessments of functionality. Porcine kidneys were retrieved, stored on ice for 3.5 hours before being placed onto a NMP circuit for 12 hours. Hemodynamics, biochemistry, and urine output were assessed. After 12 hours, kidneys were scored using the clinical assessment score. Biopsies were collected for histological assessment. Kidneys demonstrated continual improvements in hemodynamics. Perfusate sodium concentrations remained within physiologic parameters. Sodium bicarbonate increased over-time with corresponding decreases in lactate, demonstrating active renal gluconeogenesis and Cori cycle processes. Urine production began immediately and was sustained, indicating renal functionality. Under the clinical perfusion assessment score, all kidneys received a score of 1 and would be considered suitable for transplantation. Histological assessment revealed kidneys were injury free. Our NMP protocol safely preserves kidneys for over 15 hours. Successful perfusion was achieved with stable hemodynamics and biochemistry, with maintained urination. Importantly, kidneys remained in optimal health, with no evidence of injury. This may enable electivisation of transplantation, while reducing hypothermic injury.

Benefits of Living Over Deceased Donor Kidney Transplantation in Elderly Recipients. A Propensity Score Matched Analysis of a Large European Registry Cohort

Although kidney transplantation from living donors (LD) offers better long-term results than from deceased donors (DD), elderly recipients are less likely to receive LD transplants than younger ones. We analyzed renal transplant outcomes from LD versus DD in elderly recipients with a propensity-matched score. This retrospective, observational study included the first single kidney transplants in recipients aged ≥65 years from two European registry cohorts (2013-2020, n = 4,257). Recipients of LD (n = 408), brain death donors (BDD, n = 3,072), and controlled cardiocirculatory death donors (cDCD, n = 777) were matched for donor and recipient age, sex, dialysis time and recipient diabetes. Major graft and patient outcomes were investigated. Unmatched analyses showed that LD recipients were more likely to be transplanted preemptively and had shorter dialysis times than any DD type. The propensity score matched Cox's regression analysis between LD and BDD (387-pairs) and LD and cDCD (259-pairs) revealing a higher hazard ratio for graft failure with BDD (2.19 [95% CI: 1.16-4.15], p = 0.016) and cDCD (3.38 [95% CI: 1.79-6.39], p < 0.001). One-year eGFR was higher in LD transplants than in BDD and cDCD recipients. In elderly recipients, LD transplantation offers superior graft survival and renal function compared to BDD or cDCD. This strategy should be further promoted to improve transplant outcomes.

Outcomes of Kidney Perfusion Techniques in Transplantation from Deceased Donors: A Systematic Review and Meta-Analysis

The high demand for organs in kidney transplantation and the expansion of the donor pool have led to the widespread implementation of machine perfusion technologies. In this study, we aim to provide an up-to-date systematic review of the developments in this expanding field over the past 10 years, with the aim of answering the question: "which perfusion technique is the most promising technique in kidney transplantation?" A systematic review of the literature related to machine perfusion in kidney transplantation was performed. The primary outcome measure was delayed graft function (DGF), and secondary outcomes included rates of rejection, graft survival, and patient survival rates after 1 year. Based on the available data, a meta-analysis was performed. The results were compared with data from static cold storage, which is still the standard of care in many centers worldwide. A total of 56 studies conducted in humans were included, and 43 studies reported outcomes of hypothermic machine perfusion (HMP), with a DGF rate of 26.4%. A meta-analysis of 16 studies showed significantly lower DGF rates in the HMP group compared to those of static cold storage (SCS). Five studies reported outcomes of hypothermic machine perfusion + O₂, with an overall DGF rate of 29.7%. Two studies explored normothermic machine perfusion (NMP). These were pilot studies, designed to assess the feasibility of this perfusion approach in the clinical setting. Six studies reported outcomes of normothermic regional perfusion (NRP). The overall incidence of DGF was 71.5%, as it was primarily used in uncontrolled DCD (Maastricht category I-II). Three studies comparing NRP to in situ cold perfusion showed a significantly lower rate of DGF with NRP. The systematic review and meta-analysis provide evidence that dynamic preservation strategies can improve outcomes following kidney transplantation. More recent approaches such as normothermic machine perfusion and hypothermic machine perfusion + O₂ do show promising results but need further results from the clinical setting. This study shows that the implementation of perfusion strategies could play an important role in safely expanding the donor pool.

Comparison of Different Ex-Vivo Preservation Strategies on Cardiac Metabolism in an Animal Model of Donation after Circulatory Death

Transplantation of heart following donation after circulatory death (DCD) was recently introduced into clinical practice. Ex vivo reperfusion following DCD and retrieval is deemed necessary in order to evaluate the recovery of cardiac viability after the period of warm ischemia. We tested the effect of four different temperatures (4 °C-18 °C-25 °C-35 °C) on cardiac metabolism during 3-h ex vivo reperfusion in a porcine model of DCD heart. We observed a steep fall in high-energy phosphate (ATP) concentrations in the myocardial tissue at the end of the warm ischemic time and only limited regeneration during reperfusion. Lactate concentration in the perfusate increased rapidly during the first hour of reperfusion and slowly decreased afterward. However, the temperature of the solution does not seem to have an effect on either ATP or lactate concentration. Furthermore, all cardiac allografts showed a significant weight increase due to cardiac edema, regardless of the temperature.

Evaluating the Performance of a Nonelectronic, Versatile Oxygenating Perfusion System across Viscosities Representative of Clinical Perfusion Solutions Used for Organ Preservation

Introduction: On the United States' Organ Transplantation Waitlist, approximately 17 people die each day waiting for an organ. The situation continues to deteriorate as the discrepancy between harvested organs and the number of patients in need is increasing. Static cold storage is the clinical standard method for preserving a harvested organ but is associated with several drawbacks. Machine perfusion of an organ has been shown to improve preservation quality as well as preservation time over static cold storage. While there are machine perfusion devices clinically available, they are costly and limited to specific organs and preservation solutions. This study presents a versatile oxygenating perfusion system (VOPS) that supplies oxygen and pulsatile perfusion. Materials and Methods: Experiments evaluated the system's performance with a human kidney mimicking hydraulic analog using multiple compressed oxygen supply pressures and aqueous solutions with viscosities ranging from 1 to 6.5 cP, which simulated viscosities of commonly used organ preservation solutions. Results and Conclusions: The VOPS produced mean flow rates ranging from 0.6 to 28.2 mL/min and perfusion pressures from 4.8 to 96.8 mmHg, which successfully achieved the desired perfusion parameters for human kidneys. This work provides evidence that the VOPS described herein has the versatility to perfuse organs using many of the clinically available preservation solutions.

The role of hypothermic machine perfusion in selecting renal grafts with advanced histological score

BACKGROUND

Few studies explored the role of hypothermic machine perfusion (HMP) in the sub-group of non-standard renal grafts with a biopsy-proven advanced histological impairment. This study aimed to investigate the role of HMP in grafts with a Karpinski Score >3 in terms of the need for dialysis, creatinine reduction ratio at day-7 (CRR7), and 3-year graft survival.

METHODS

Twenty-three perfused grafts with Karpinski Score >3 evaluated between November 2017 and December 2018 were retrospectively analyzed and compared with a control group of 32 non-perfused grafts transplanted between January 2014 and October 2017.

RESULTS

After transplantation, perfused grafts had fewer cases requiring dialysis (8.7% vs. 34.4%; p = 0.051), a better reduction in serum creatinine (median at 7 days: 2.2 vs. 4.3 mg/dl; p = 0.045), and shorter length of hospital stay (median 11 vs. 15 days; p = 0.01). Three-year death-censored graft survival was better in the perfused cases (91.3% vs. 77.0%; p = 0.16). In perfused grafts, initial renal resistance (RR) had the best predictive value for renal function recovery after the first week, as defined by CRR7 ≤ 70% (AUC = 0.83; p = 0.02). A cut-off value of 0.5 mm Hg/ml/min showed a sensitivity of 82.4%, a specificity of 83.3%, and diagnostic odds ratio = 23.4. After dividing the entire population into a Low-RR (n = 8) and a High-RR Group (n = 15), more cases with CRR7 ≤ 70% were reported in the latter group (86.7 vs. 13.3%; p = 0.03).

CONCLUSION

HMP yielded promising results in kidneys with Karpinski Score >3. Initial RR should be of interest in selecting non-standard organs for single kidney transplantation even in impaired histology.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and DBD/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

Advances in Hypothermic and Normothermic Perfusion in Kidney Transplantation

Hypothermic and normothermic machine perfusion in kidney transplantation are purported to exert a beneficial effect on post-transplant outcomes compared to the traditionally used method of static cold storage. Kidney perfusion techniques provide a window for organ reconditioning and quality assessment. However, how best to deliver these preservation methods or improve organ quality has not yet been conclusively defined. This review summarises the promising advances in machine perfusion science in recent years, which have the potential to further improve early graft function and prolong graft survival.

Advances in Kidney Preservation Techniques and Their Application in Clinical Practice

The use of cold preservation solutions to rapidly flush and cool the kidney followed by static cold storage in ice has been the standard kidney preservation technique for the last 50 y. Nonetheless, changing donor demographics that include organs from extended criteria donors and donation after circulatory death donors have led to the adoption of more diverse techniques of preservation. Comparison of hypothermic machine perfusion and static cold storage techniques for deceased donor kidneys has long been debated and is still contested by some. The recent modification of hypothermic machine perfusion techniques with the addition of oxygen or perfusion at subnormothermic or near-normothermic temperatures are promising strategies that are emerging in clinical practice. In addition, the use of normothermic regional perfusion to resuscitate abdominal organs of donation after circulatory death donors in situ before cold flushing is also increasingly being utilized. This review provides a synopsis of the different types of preservation techniques including their mechanistic effects and the outcome of their application in clinical practice for different types of donor kidney.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and brain death/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

Efficacy and Safety of Machine Perfusion for Brain Death Marginal Donor Kidney Transplantation: A Report of 2 Cases

BACKGROUND

After the revised organ transplant law came into effect in Japan, donations of organs under brain death have been increasing; however, because of the expansion of donor indications, donations from expanded criteria donors and cardiac arrest donors (donation after cardiac death) have also increased. In kidney transplantation, ischemia-reperfusion injury results in a high rate of delayed graft function, which adversely affects patients' long-term prognoses. Hypothermic machine perfusion preservation results in superior postoperative function and survival rates compared with cold storage preservation. We used an organ preservation device for kidneys and performed a graft viability evaluation before to kidney transplantation.

METHODS

We used the CMP-X08 perfusion device (Chuo-Seiko Co, Ltd, Asahikawa, Hokkaido, Japan) and Belzer MPS solution to preserve the donated organ. The perfusion pressure and temperature were monitored during cold storage with continuous perfusion. Standard renal transplantation protocols were followed. A renal biopsy was performed 1 hour after transplantation and the renal function was evaluated. This study followed the principles of the Declaration of Helsinki.

RESULTS

The first presented case is of a 63-year-old woman who received a kidney from a middle-aged man with brain death due to hypoxic encephalopathy. The creatinine at the time of admission was 0.9 mg/dL and at the time of excision was 2.86 mg/dL. The total perfusion time was 120 minutes. The total ischemia time was 7 hours and 15 minutes. The recipient urinated 115 minutes postoperatively, and no dialysis was required. The second presented case is of a 47-year-old man with a 15-year history of dialysis who received a kidney from a middle-aged woman with brain death due to subarachnoid hemorrhage. The creatinine at the time of admission was 0.8 mg/dL and at the time of excision was 0.77 mg/dL. The total perfusion time was 240 minutes. The total ischemia time was 13 hours and 14 minutes. The recipient urinated 38 minutes postoperatively, and no dialysis was required.

CONCLUSIONS

Mechanical perfusion storage performed for 2 to 4 hours resulted in a viable organ that was successfully transplanted in both cases.

Hypothermic, oxygenated perfusion (HOPE) provides cardioprotection via succinate oxidation prior to normothermic perfusion in a rat model of donation after circulatory death (DCD)

In donation after circulatory death (DCD), cardiac grafts are subjected to warm ischemia in situ, prior to a brief period of cold, static storage (CSS) at procurement, and ex situ, normothermic, machine perfusion (NMP) for transport and graft evaluation. Cold ischemia and normothermic reoxygenation during NMP could aggravate graft injury through continued accumulation and oxidation, respectively, of mitochondrial succinate, and the resultant oxidative stress. We hypothesized that replacing CSS with hypothermic, oxygenated perfusion (HOPE) could provide cardioprotection by reducing cardiac succinate levels before NMP. DCD was simulated in male Wistar rats. Following 21 minutes in situ ischemia, explanted hearts underwent 30 minutes hypothermic storage with 1 of the following: (1) CSS, (2) HOPE, (3) hypothermic deoxygenated perfusion (HNPE), or (4) HOPE + AA5 (succinate dehydrogenase inhibitor) followed by normothermic reperfusion to measure cardiac and metabolic recovery. After hypothermic storage, tissue ATP/ADP levels were higher and succinate concentration was lower in HOPE vs CSS, HNPE, and HOPE + AA5 hearts. After 60 minutes reperfusion, cardiac function was increased and cellular injury was decreased in HOPE compared with CSS, HNPE, and HOPE + AA5 hearts. HOPE provides improved cardioprotection via succinate oxidation prior to normothermic reperfusion compared with CSS, and therefore is a promising strategy for preservation of cardiac grafts obtained with DCD.

Donor pretreatment and machine perfusion: current views

PURPOSE OF REVIEW

To summarise recently published studies of donor pretreatment and machine perfusion strategies in kidney transplantation.

RECENT FINDINGS

The sparsity of donor pretreatment trials has resulted in the re-analysis of already existing data, and RCTs are urgently needed to reinvigorate this aspect of donor research. Uncontrolled donation after circulatory death kidney transplantation has the highest risk of delayed graft function and graft failure, and recent studies have reported that normothermic regional perfusion improves graft function and survival in this setting. Hypothermic machine perfusion reduces delayed graft function following deceased donor kidney transplantation across donor types but unanswered questions still remain regarding its use. The use of oxygenated hypothermic machine perfusion appears to improve graft function in controlled donation after circulatory death mediated by a reduction in acute rejection. Ex-situ normothermic perfusion is emerging and while technically challenging it may facilitate the delivery of pretreatments.

SUMMARY

RCTs are urgently needed to reinvigorate research into donor pretreatment and to establish the place of specific preservation techniques in deceased donor kidney transplantation.

Cold Pulsatile Machine Perfusion Versus Static Cold Storage for Kidneys Donated After Circulatory Death: A Multicenter Randomized Controlled Trial

BACKGROUND

The benefits of cold pulsatile machine perfusion (MP) for the storage and transportation of kidneys donated after circulatory death are disputed. We conducted a UK-based multicenter, randomized controlled trial to compare outcomes of kidneys stored with MP versus static cold storage (CS).

METHODS

Fifty-one pairs of kidneys donated after circulatory death were randomly allocated to receive static CS or cold pulsatile MP. The primary endpoint, delayed graft function, was analyzed by "intention-to-treat" evaluation.

RESULTS

There was no difference in the incidence of delayed graft function between CS and MP (32/51 (62.8%) and 30/51 (58.8%) P = 0.69, respectively), although the trial stopped early due to difficulty with recruitment. There was no difference in the incidence of acute rejection, or in graft or patient survival between the CS and MP groups. Median estimated glomerular filtration rate at 3 months following transplantation was significantly lower in the CS group compared with MP (CS 34 mL/min IQR 26-44 vs MP 45 mL/min IQR 36-60, P = 0.006), although there was no significant difference in estimated glomerular filtration rate between CS and MP at 12 months posttransplant.

CONCLUSIONS

This study is underpowered, which limits definitive conclusions about the use of MP, as an alternative to static CS. It did not demonstrate that the use of MP reduces the incidence of delayed graft function in donation after circulatory death kidney transplantation.

Oxygenation of the Transplanted Kidney

Although kidney oxygen tensions are heterogenous, and mostly below renal vein level, the nephron is highly dependent on aerobic metabolism for active tubular transport. This renders the kidney particularly susceptible to hypoxia, which is considered a main characteristic and driver of acute and chronic kidney injury, albeit the evidence supporting this assumption is not entirely conclusive. Kidney transplants are exposed to several conditions that may interfere with the balance between oxygen supply and consumption, and enhance hypoxia and hypoxic injury. These include conditions leading to and resulting from brain death of kidney donors, ischemia and reperfusion during organ donation, storage and transplantation, postoperative vascular complications, vasoconstriction induced by immunosuppression, and impaired perfusion resulting from interstitial edema, inflammation, and fibrosis. Acute graft injury, the immediate consequence of hypoxia and reperfusion, results in delayed graft function and increased risk of chronic graft failure. Although current strategies to alleviate hypoxic/ischemic graft injury focus on limiting injury (eg, by reducing cold and warm ischemia times), experimental evidence suggests that preconditioning through local or remote ischemia, or activation of the hypoxia-inducible factor pathway, can decrease hypoxic injury. In combination with ex vivo machine perfusion such approaches hold significant promise for improving transplantation outcomes.

Comparison of machine perfusion versus cold storage in kidney transplant recipients from expanded criteria donors: a cohort-based study

BACKGROUND

Most studies comparing the efficacy of hypothermic machine perfusion (HMP) versus static cold storage (SCS) are based on short-term outcomes. We aimed to better evaluate the mid-term impact of HMP in patients receiving expanded criteria donor (ECD) kidneys.

METHODS

The analyses were based on the French Données Informatisées et VAlidées en Transplantation (DIVAT) observational cohort. Patients aged ≥45 years transplanted for the first or second times from an ECD donor since 2010 were studied. Our study reported the graft and/or patient survivals and the incidence of acute rejection episode. The Cox models and the Kaplan-Meier estimators, weighted on the propensity score, were used to study the times-to-events.

RESULTS

Among the 2019 included patients, 1073 were in the SCS group versus 946 in the HMP group. The mean life expectancy with functioning graft was 5.7 years [95% confidence interval (CI) 5.4-6.1] for the HMP cohort followed-up for 8 years post-transplantation versus 6.0 years (95% CI 5.7-6.2) for the SCS group. These mid-term results were comparable in the patients receiving grafts from donors aged ≥70 years and in the transplantations with cold ischaemia time ≥18 h.

CONCLUSIONS

Our study challenges the utility of using HMP to improve mid-term patient and graft survival. Nevertheless, the improvement of the short-term outcomes is indisputable. It is necessary to continue technological innovations to obtain long-term results.

SUL-109 Protects Hematopoietic Stem Cells from Apoptosis Induced by Short-Term Hypothermic Preservation and Maintains Their Engraftment Potential

The newly developed 6-hydroxychromanol derivate SUL-109 was shown to provide protection during hypothermic storage of several cell lines, but has not been evaluated in hematopoietic stem cells (HSCs). Hypothermic preservation of HSCs would be preferred over short-term cryopreservation to prevent cell loss during freezing/thawing and would be particularly useful for short-term storage, such as during conditioning of patients or transport of HSC transplants. Here we cultured human CD34⁺ umbilical cord blood (UCB) cells and lineage-depleted (Lin^-) Balb/c bone marrow (BM) cells for up to 7 days in serum-free HSC expansion medium with hematopoietic growth factors. SUL-109-containing cultures were stored at 4°C for 3 to 14 days. The UCB cells were tested for viability, cell cycle, and reactive oxygen species (ROS). DMSO-cryopreserved Lin^- BM cells or Lin^- BM cells maintained for 14 days at 4°C were transplanted into RAG2^-/- Balb/c mice and engraftment was followed for 6 months. The addition of SUL-109 during the hypothermic storage of expanded CD34⁺ UCB cells provided a significant improvement in cell survival of the immature CD34⁺/CD38^- fraction after 7 days of hypothermic storage through scavenging of hypothermia-induced ROS and was able to preserve the multilineage capacity of human CD34⁺ UCB cells for up to 14 days of cold storage. In addition, SUL-109 protected murine BM Lin^- cells from 14 days of hypothermic preservation and maintained their engraftment potential after transplantation in immune-deficient RAG2^-/- mice. Our data indicate that SUL-109 is a promising novel chemical for use as a protective agent during cold storage of human and murine HSCs to prevent hypothermia-induced apoptosis and promote cell viability.

The Effects of Oxygenation on Ex Vivo Kidneys Undergoing Hypothermic Machine Perfusion

BACKGROUND

Supplemental oxygenation of the standard hypothermic machine perfusion (HMP) circuit has the potential to invoke favorable changes in metabolism, optimizing cadaveric organs before transplantation.

METHODS

Eight pairs of porcine kidneys underwent 18 hours of either oxygenated (HMP/O2) or aerated (HMP/Air) HMP in a paired donation after circulatory death model of transplantation. Circulating perfusion fluid was supplemented with the metabolic tracer universally labeled glucose.Perfusate, end-point renal cortex, and medulla samples underwent metabolomic analysis using 1-dimension and 2-dimension nuclear magnetic resonance experiments in addition to gas chromatography-mass spectrometry. Analysis of C-labeled metabolic products was combined with adenosine nucleotide levels and differences in tissue architecture.

RESULTS

Metabolomic analysis revealed significantly higher concentrations of universally labeled lactate in the cortex of HMP/Air versus HMP/O2 kidneys (0.056 mM vs 0.026 mM, P < 0.05). Conversely, newly synthesized [4,5-C] glutamate concentrations were higher in the cortex of HMP/O2 kidneys inferring relative increases in tricarboxylic acid cycle activity versus HMP/Air kidneys (0.013 mmol/L vs 0.003 mmol/L, P < 0.05). This was associated with greater amounts of adenoside triphosphate in the cortex HMP/O2 versus HMP/Air kidneys (19.8 mmol/mg protein vs 2.8 mmol/mg protein, P < 0.05). Improved flow dynamics and favorable ultrastructural features were also observed in HMP/O2 kidneys. There were no differences in thiobarbituric acid reactive substances and reduced glutathione levels, tissue markers of oxidative stress, between groups.

CONCLUSIONS

The supplementation of perfusion fluid with high-concentration oxygen (95%) results in a greater degree of aerobic metabolism versus aeration (21%) in the nonphysiological environment of HMP, with reciprocal changes in adenoside triphosphate levels.

Impact of distance between donor and recipient hospitals on cadaveric kidney transplantation outcomes

BACKGROUND

The impact of distance between donor and recipient hospitals on outcomes in cadaveric kidney transplantations is unknown. We investigated the association between inter-hospital distance and outcomes in cadaveric kidney transplantations in Japan.

METHODS

We retrospectively analyzed 363 cadaveric kidney transplantations between 2002 and 2017 in Japan. Inter-hospital distance, graft transport time, total ischemic time (TIT), and graft survival were compared between our hospital and national transplantation cohort in Japan. Estimated glomerular filtration rate (eGFR) 1 month and 1 year after transplantation was compared between cadaveric and living-donor kidney transplantations in our hospitals. Additionally, inter-hospital distances among the seven geographical regions in Japan were assessed.

RESULTS

There were 12 and 351 cadaveric kidney transplantations at our hospital and in Japan, respectively. Mean inter-hospital distance at our hospital (217 ± 121 km) was significantly longer than that of the national cohort (53 ± 80 km; P < 0.001). Mean TIT and graft survival for our hospital and national cohort were 539 ± 200 min and 91% and 491 ± 193 min and 81%, respectively. Mean eGFRs 1 year after cadaveric and living-donor transplantations at our hospitals were comparable (47 ± 16 vs. 47 ± 15 mL/min/1.73 m²). The comparison among seven regions in Japan indicated a regional difference in inter-hospital distance with an association between area (km²) and inter-hospital distance (km).

CONCLUSIONS

Despite the longer inter-hospital distance at our hospital, TIT and transplant outcomes were acceptable in our cases. In addition, geographical inequity in graft allocation in Japan was suggested.

Cold Pulsatile Machine Perfusion versus Static Cold Storage in Kidney Transplantation: A Single Centre Experience

INTRODUCTION

We present our experience with hypothermic machine perfusion (HMP) versus cold storage (CS) in relation to kidney transplant outcomes.

METHODS

Retrospective analysis of 33 consecutive HMP kidney transplant outcomes matched with those of 33 cold stored: delayed graft function (DGF), length of hospital stay (LOS), estimated glomerular filtration rate (eGFR), and patient and graft survival were compared. Renal Resistive Indexes (RIs) during HMP in relation to DGF were also analysed.

RESULTS

In the HMP group, mean HMP time was 5.7 ± 3.9 hours with a mean cold ischaemic time (CIT) of 15 ± 5.6 versus 15.1 ± 5.3 hours in the CS group. DGF was lower in the HMP group (p=0.041), and donation after Circulatory Death (DCD) was a predictor for DGF (p<0.01). HMP decreased DGF in DCD grafts (p=0.036). Patient and graft survival were similar, but eGFR at 365 days was higher in the HMP cohort (p<0.001). RIs decreased during HMP (p<0.01); 2-hours RI ≥ 0.45 mmHg/mL/min predicted DGF in DCD kidneys (75% sensitivity, 80% specificity; area under the curve 0.78); 2-hours RI ≥ 0.2 mmHg/ml/min predicted DGF in DBD grafts (sensitivity 100%, specificity 91%; area under the curve 0.87).

CONCLUSION

HMP decreased DGF compared to CS, offering viability assessment pretransplant and improving one-year renal function of the grafts.

Hypothermic Machine Perfusion Versus Static Cold Storage in Deceased Donor Kidney Transplantation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Static cold storage (SCS) and hypothermic machine perfusion (HMP) are two primary options for renal allograft preservation. Compared with SCS, HMP decreased the incidence of delayed graft function (DGF) and protected graft function. However, more evidence is still needed to prove the advantages of the HMP. In this study, the outcomes of kidney grafts from the two preservation methods were compared by conducting a systematic review and meta-analysis. Randomized controlled trials (RCTs) comparing the effect of hypothermic machine perfusion and static cold storage in deceased donor kidney transplantation were identified through searches of the MEDLINE, EMBASE, and Cochrane databases between January 1, 1980 and December 30, 2017. The primary endpoints were delayed graft function and graft survival. Secondary endpoints included primary non-function (PNF), graft renal function, duration of DGF, acute rejection, postoperative hospital stay and patient survival. Summary effects were calculated as risk ratio (RR) with 95% confidence interval (CI) or mean difference (MD) with 95% confidence intervals (CI). A total of 13 RCTs were included, including 2048 kidney transplant recipients. The results indicated that compared with SCS, HMP decreased the incidence of DGF (RR 0.78, 95% CI 0.69-0.87, P < 0.0001), and improved the graft survival at 3 years (RR 1.06, 95% CI 1.02-1.11, P = 0.009). There was no significant difference in other endpoints. HMP might be a more desirable method of preservation for kidney grafts. The long-term outcomes of kidney allografts stored by hypothermic machine perfusion still need to be further investigated.

Biomarkers and Pharmacogenomics in Kidney Transplantation

This review is focused on present and future biomarkers, along with pharmacogenomics used in clinical practice for kidney transplantation. It aims to highlight biomarkers that could potentially be used to improve kidney transplant early and long-term graft survival, but also potentially patient co-morbidity. Future directions for improving outcomes are discussed, which include immune tolerance and personalising immunosuppression regimens.