Kidney transplantation is the preferred treatment for end-stage renal disease and is limited by donor organ availability. Normothermic Machine Perfusion (NMP) might facilitate safe transplantation of marginal organs. NKP1 is a single centre, phase 1, 36-patient, three-stage cohort study investigating the safety and feasibility of up to 24 hours of renal NMP prior to transplantation. 30-day graft survival (primary endpoint) was 100%. Secondary objectives were assessment of the effect of NMP on post-transplant clinical outcomes and ischaemia-reperfusion injury, identification of predictive biomarkers, and characterisation of the performance of the preservation system. Clinical outcomes were comparable to a matched control cohort with 12-month estimated glomerular filtration rate (eGFR) 46.3 vs 49.5 mL/min/1.73m2 (p = 0.44) despite much longer total preservation times (15.7 vs 8.9 hours controls, p < 0.0001). We saw strong correlations between biomarkers measured ex-situ and post-transplant outcomes, including graft function at one year (correlation between GST-Pi delta and 12-month eGFR, R = 0.54, p = 0.001). Renal NMP is useful for optimising logistics and as an organ assessment technique, and has potential to expand the donor pool. Trial registration number: ISRCTN13292277.

Patients with end-stage renal disease often face prolonged waiting times for kidney transplants. Historically, the use of marginal kidneys was limited due to suboptimal preservation methods. Normothermic machine perfusion (NMP) preserves physiological activity during the preservation process, potentially improving graft function and viability, expanding the use of marginal kidneys. While preliminary results are promising, NMP has not yet undergone sufficient clinical trials to determine whether it offers advantages over more widely used techniques. The aim of this systematic review is to assess several outcomes between kidneys that underwent NMP compared to traditional preservation methods after kidney transplant.

A systematic review was conducted following PRISMA guidelines. Randomized controlled trials, case series, and studies comparing NMP with hypothermic machine perfusion (HMP) or static cold storage (SCS) were included. The primary outcome assessed was delayed graft function (DGF). Secondary outcomes included primary non-function (PNF), acute rejection, and 1-year graft survival.

Eight NMP studies met the inclusion criteria. Meta-analysis showed significant differences in DGF between NMP and control (HMP or SCS) groups (OR: 0.47 [0.22, 0.99], p < 0.05). There were no significant differences between NMP and controls for PNF, acute rejection, or 1-year graft survival.

These findings suggest that NMP yields similar adverse outcome rates compared to traditional methods. Notably, NMP could be associated with reduced rates of DGF. While NMP is a promising technique for renal allograft preservation, further randomized controlled trials are necessary to definitively establish its benefits over conventional preservation methods.

Kidney transplantation is considered the benchmark treatment for end-stage kidney disease patients, yet the scarcity of suitable kidneys poses a significant hindrance for patients and healthcare providers. One approach is to extend the criteria for the use of kidneys from deceased brain death and deceased circulatory death donors. Use of these organs, especially from these extended criteria donors, is associated with ischemia reperfusion injury and resultant delayed graft function as well as increased rates of allograft rejection. To lessen these complications as well as increase the time of organ viability assessment, machine perfusion has been evaluated on recovered kidneys. In this study we examined the immunogenic molecular content of perfusates from discarded organs that had undergone Controlled Oxygenated Rewarming (COR). Perfusates were analyzed for extracellular vesicles (EVs), DNA (Deoxyribonucleic acid), and microRNAs. These perfusates were then pumped over a plasma separator containing a lectin affinity resin. Following treatment, a significant diminution in extracellular vesicles, dsDNA (double-stranded DNA) associated with EVs, and microRNAs (miRNA) were observed. Specifically, in three out of the four renal perfusates analyzed there was significant removal of small EVs (<200 nm) and vesicles loaded with dsDNA (p < 0.05). Notably, depletion of larger EVs (100-500 nm) was found to be significant in all treated perfusates (p < 0.01). NanoString analysis of miRNA found 5 species potentially involved in renal dysfunction (hsa-let 7a-5p, hsa-miR-148b-3p, hsa-miR-148a-3p, hsa-miR-29b-3pb and hsa-miR-99a5p) to be significantly depleted in treated renal perfusates (p ≤ 0.05). These results support a future study incorporating this treatment method into a dynamic machine perfusion circuit to explore if reduction of these mediators is associated with improved function of retrieved kidneys.

Human donor kidneys release (pro)renin, erythropoietin (EPO), active vitamin D, and urodilatin during normothermic machine perfusion (NMP). However, whether the endocrine function of donor kidneys is associated with post-transplant kidney function is unclear.

We studied 28 donor kidneys, including seven from donation after brain death (DBD) donors and 21 from donation after circulatory death (DCD) donors. Prior to transplantation, we measured levels of (pro)renin, EPO, 1,25(OH)2D in the perfusate, and urodilatin in urine during NMP. Hormone release rates were compared between kidneys with and without delayed graft function (DGF), and correlations were assessed between hormone release rates and donor characteristics and transplant outcome, including DGF duration, serum creatinine levels at 1-week post-transplant, and estimated glomerular filtration rate at 1-month post-transplant.

DBD kidneys secreted significantly less EPO and more active vitamin D than DCD kidneys. Kidneys with DGF exhibited significantly higher release rates of active vitamin D and lower release rates of urodilatin compared to those without DGF. In addition, EPO release rate was positively correlated with serum creatinine levels at 1-week post-transplant. Finally, urodilatin release rates were negatively correlated with DGF duration and positively correlated with urine output.

Urodilatin release in urine and EPO and active vitamin D release in perfusate during NMP may serve as potential biomarkers for predicting early post-transplant outcomes.

ClinicalTrials.gov identifier: NCT04882254.

Normothermic machine perfusion (NMP) provides opportunity for viability assessment of donated kidneys. Diminished microvascular perfusion, despite adequate total blood flow, is a key pathophysiology in ischaemia-mediated acute kidney injury. Contrast-enhanced ultrasound (CEUS) could allow objective assessment of microvascular perfusion during renal NMP. Blood-based NMP was performed on porcine kidneys (circulatory death model) and human kidneys declined for transplant (preclinical). CEUS was performed with a contrast bolus into the NMP circuit arterial limb. Microvascular perfusion quality was quantified and z-score normalisation allowed combination of metrics and regions into an overall "CEUS-score." In porcine kidneys, inferior microvascular perfusion of cortex and medulla correlated with increased urinary NGAL (Neutrophil gelatinase-associated lipocalin) and histological DNA-fragmentation (a hallmark of apoptosis). In human kidneys, CEUS-score at 2 h was correlated with histological DNA-fragmentation (r = -0.937; P = 0.019) and predicted urinary NGAL at 24 h of NMP (r = -0.925; P = 0.024). Total renal flow was not correlated with these outcomes. An open-source web application (stingle.shinyapps.io/Time_intensity_analysis) and R package ("tican") were developed for quantitative time-intensity curve analysis. CEUS allows objective point-of-care microvascular perfusion assessment during NMP. As 2-hour CEUS-score predicts NGAL at 24 h, CEUS warrants future clinical investigation as a potential tool to assess kidney quality in assessment and reconditioning centres.

Transplantation is the standard treatment for end-stage kidney disease but carries with it a non-trivial risk of post-operative complication. There is a need for a continuous, real-time, not additionally invasive method of monitoring organ perfusion. We present an approach to allograft perfusion monitoring using a human kidney model using ex vivo normothermic perfusion (EVNP) and custom spectroscopic optical reflectance probes. Five discarded human kidneys underwent EVNP, spectroscopic measurement and were subjected to perfusion compromising events (rejection, thrombosis or haemorrhage). Oxygenated and deoxygenated haemoglobin spectra were fitted to the spectra acquired from the kidneys in order to estimate the oxygen saturation. Average oxygen saturations before the perfusion compromising events were estimated to be higher than after (or similar in the control cases). Changes in oxygen saturation estimated from measurements made continuously were synchronized well with changes in renal blood flow index measurements. This proof of concept study proves promising in identifying a technique for continuous monitoring of perfusion and oxygenation of a transplanted kidney in vivo with minimal additional invasiveness.

To overcome organ shortages, donation after circulatory death (DCD) kidneys are being increasingly used for transplantation. Prior research suggests that DCD kidneys have inferior outcomes compared with kidneys donated after brain death. Normothermic machine perfusion (NMP) and normothermic regional perfusion (NRP) may enhance the preservation of DCD kidneys and improve transplant outcomes. This study aimed to review the evidence surrounding NMP and NRP in DCD kidney transplantation.

Two independent reviewers conducted searches for all publications reporting outcomes for NMP and NRP-controlled DCD kidneys, focusing on delayed graft function, primary nonfunction, graft function, graft survival, and graft utilization. Weighted means were calculated for all relevant outcomes and controls. Formal meta-analyses could not be conducted because of significant heterogeneity.

Twenty studies were included for review (6 NMP studies and 14 NRP studies). Delayed graft function rates seemed to be lower for NRP kidneys (24.6%) compared with NMP kidneys (54.3%). Both modalities yielded similar outcomes with respect to primary nonfunction (NMP 3.3% and NRP 5.6%), graft function (12-mo creatinine 149.3 μmol/L for NMP and 129.9 μmol/L for NRP), and graft utilization (NMP 83.3% and NRP 89%). Although no direct comparisons exist, our evidence suggests that both modalities have good short- and medium-term graft outcomes and high graft survival rates.

Current literature demonstrates that both NMP and NRP are feasible strategies that may increase donor organ utilization while maintaining acceptable transplant outcomes and likely improved outcomes compared with cold-stored DCD kidneys. Further research is needed to directly compare NRP and NMP outcomes.

Normothermic machine perfusion (NMP) provides a platform for kidney quality assessment. Donation after circulatory death (DCD) donor kidneys are associated with great ischemic injury and high intrarenal resistance (IRR). This experimental study aims to investigate the impact of different perfusion pressures on marginal kidney function and injury during NMP.

Twenty-seven slaughterhouse porcine kidneys were retrieved and subjected to 60 min of warm ischemia time to mimic DCD condition. These kidneys were randomized into 75 mmHg (subphysiological, n = 9), 95 mmHg (physiological, n = 9), and 115 mmHg NMP (high physiological, n = 9). Renal function and injury were assessed during NMP.

Three groups showed comparable IRR, with the 115 mmHg group exhibiting the highest blood flow. The 95 mmHg group [0.48 (0.36-1.15) ml/min/100g] and 115 mmHg group [0.93 (0.45-1.41) ml/min/100g] showed significantly higher creatinine clearance compared to the 75 mmHg group [0.16 (0.08-0.37) ml/min/100g] during the first hour of NMP (p = 0.049, p = 0.009, respectively). The 115 mmHg group exhibited significantly higher oxygen consumption compared to the 75 mmHg group at 30 min of NMP [1.37 (1.05-1.92) versus 0.72 (0.61-0.82) mlO2/min/100g, p = 0.009]. Perfusate neutrophil gelatinase-associated lipocalin (NGAL) levels were consistently lowest in the 95 mmHg group and highest in the 75 mmHg group. Aspartate aminotransferase (AST) levels of the 115 mmHg group were significantly higher than the 75 mmHg group.

For kidneys with high IRR, both 95 mmHg and 115 mmHg perfusion pressures enable an early improvement in renal hemodynamics and function compared to 75 mmHg during NMP, while a high physiological perfusion can cause additional injury.

A growing interest in renal normothermic machine perfusion (NMP) has resulted in more clinically available perfusion devices. While all perfusion systems have the same aim, there are significant differences in their circuits, pumps, sensors, and software. Therefore, our objective was to assess the impact of different perfusion protocols and devices on kidney function and perfusion parameters during NMP.

Porcine kidneys were subjected to 30 min of warm ischemia, 24 h of static cold storage, and subsequently perfused for 6 h using (1) the Kidney Assist (KA) machine with a pressure of 75 mm Hg, (2) the KA device incorporating several adjustments and a pressure of 85 mm Hg (modified KA), or (3) the Perlife (PL) perfusion device (n = 4). Consecutively, discarded human kidneys were perfused using the KA or modified KA (n = 3) protocol.

The PL group quickly reached the device's upper flow limit and consequently received a significantly lower pressure compared to the KA groups. The arterial pO2 was significantly lower in the PL group. Yet, hemoglobin concentration increased over time, and oxygen consumption was significantly higher compared to the KA groups. Fractional sodium excretion was significantly lower in the PL group. Tissue ATP levels, urine production, and creatinine clearance rates did not differ between groups. In human kidneys, the modified KA group showed significantly lower vascular resistance, higher oxygen delivery, and lower levels of lactate in the perfusate compared to the KA group.

This study shows that perfusion characteristics and kidney function are significantly influenced by the perfusion protocol and the device and its settings during normothermic machine perfusion and therefore should be interpreted with caution.

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.

Ex vivo perfusion of transplant-declined human organs has emerged as a promising platform to study the response of an organ to novel therapeutic strategies. However, to fully realize the capability of this platform for performing translational research in human organ pathophysiology, there is a need for robust assays to assess organ function and disease. State-of-the-art research methods rely on analyses of biopsies taken during perfusion, which both damages the organ and only provides localized information. Developing non-invasive, whole organ methods of assessment is critical to the further development of this research platform.

We use ex vivo cold infusion scanning (EXCIS) with contrast-enhanced computed tomography (CT) to quantify perfusion in kidneys preserved ex vivo. EXCIS-CT computes three complementary metrics for whole organ assessment: a dynamic assessment of contrast filling, a measure of vascular network anatomical structure, and a static assessment of perfusion heterogeneity.

These metrics were applied to a series of six transplant-declined human kidneys, which demonstrated a range of anatomies and perfusion. Lastly, two transplant-declined human kidneys were imaged before and after a 1-h period of ex vivo normothermic perfusion (NMP). We found variable responses to NMP, with one kidney maintaining the vascular network and hemodynamics and the other showing significant changes in vessel size and spatial perfusion profile.

EXCIS-CT provides metrics that can be used to characterize whole organ perfusion and vascular function.

Current kidney perfusion protocols are not optimized for addressing the ex vivo physiological and metabolic needs of the kidney. Ex vivo normothermic perfusion may be utilized to distinguish high-risk kidneys to determine suitability for transplantation. Here, we assessed the association of tissue metabolic changes with changes in a kidney injury biomarker and functional parameters in eight deceased donor kidneys deemed unsuitable for transplantation during a 12-hour ex vivo normothermic perfusion. The kidneys were grouped into good and poor performers based on blood flow and urine output. The mean age of the deceased kidney donors was 43 years with an average cold ischemia time of 37 hours. Urine output and creatinine clearance progressively increased and peaked at six hours post-perfusion among good performers. Poor performers had 71 ng/ml greater (95% confidence interval 1.5, 140) urinary neutrophil gelatinase-associated lipocalin at six hours compared to good performers corresponding to peak functional differences. Organ performance was distinguished by tissue metabolic differences in branched chain amino acid metabolism and that their tissue levels negatively correlated with urine output among all kidneys at six hours. Tissue lipid profiling showed poor performers were highlighted by the accumulation of membrane structure components including glycerolipids and sphingolipids at early perfusion time points. Thus, we showed that six hours is needed for kidney function recovery during ex vivo normothermic perfusion and that branched chain amino acid metabolism may be a major determinant of organ function and resilience.

Normothermic machine perfusion (NMP) is increasingly considered for pretransplant kidney quality assessment. However, fundamental questions about differences between in vivo and ex vivo renal function, as well as the impact of ischemic injury on ex vivo physiology, remain unanswered. This study utilized magnetic resonance imaging (MRI), alongside conventional parameters to explore differences between in vivo and ex vivo renal function and the impact of warm ischemia on a kidney's behavior ex vivo. Renal MRI scans and samples were obtained from living pigs (n = 30) in vivo. Next, kidney pairs were procured and exposed to minimal, or 75 minutes of warm ischemia, followed by 6 hours of hypothermic machine perfusion. Both kidneys simultaneously underwent 6-hour ex vivo perfusion in MRI-compatible NMP circuits to obtain multiparametric MRI data. Ischemically injured ex vivo kidneys showed a significantly altered regional blood flow distribution compared to in vivo and minimally damaged organs. Both ex vivo groups showed diffusion restriction relative to in vivo. Our findings underscore the differences between in vivo and ex vivo MRI-based renal characteristics. Therefore, when assessing organ viability during NMP, it should be considered to incorporate parameters beyond the conventional functional markers that are common in vivo.

Using ex vivo normothermic machine perfusion (NMP) with whole blood we assessed marginal porcine kidneys under reperfusion. The aim was to link measureable machine and clinical blood parameters with the currently used visual assessment. This could serve as a baseline for a standardized evaluation score to identify potentially transplantable kidneys in the future.

Kidneys and autologous whole blood were procured from slaughterhouse pigs (n = 33) and were perfused for 4 h using NMP. The hemodynamic parameters arterial pressure (AP), renal blood flow (RBF) and intrarenal resistance (IRR) were measured. Activity of aspartate transaminase (AST), gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and lactate were assessed in blood at 0/1/2/4 h. Kidneys were grouped into "potentially transplantable" (PT) or "not transplantable" (NT) based on their overall macroscopic appearance after NMP by an experienced physician.

PT-kidneys (n = 20) had a significantly lower IRR and higher RBF than NT-kidneys (n = 13). GGT, ALP and LDH did not differ significantly, but at 4 h, AST was significantly higher in PT-kidneys compared to NT-kidneys. Lactate levels kept increasing during NMP in NT-kidneys and were significantly higher at 1/2/4 h than in PT-kidneys.

The immediately assessed macroscopic aspects of examined kidneys correlated with hemodynamic parameters, increased lactate and lower AST in this study. In the future, NMP with whole blood could be a useful tool to extend the donor pool by allowing the assessment of otherwise unknown characteristics of marginal kidneys before transplantation.

Kidney transplantation is the optimal treatment for kidney failure. Donation, transport and transplant of kidney grafts leads to significant ischaemia reperfusion injury. Static cold storage (SCS), whereby the kidney is stored on ice after removal from the donor until the time of implantation, represents the simplest preservation method. However, technology is now available to perfuse or "pump" the kidney during the transport phase ("continuous") or at the recipient centre ("end-ischaemic"). This can be done at a variety of temperatures and using different perfusates. The effectiveness of these treatments manifests as improved kidney function post-transplant.

To compare machine perfusion (MP) technologies (hypothermic machine perfusion (HMP) and (sub) normothermic machine perfusion (NMP)) with each other and with standard SCS.

We contacted the information specialist and searched the Cochrane Kidney and Transplant Register of Studies until 15 June 2024 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 Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

All randomised controlled trials (RCTs) and quasi-RCTs comparing machine perfusion techniques with each other or versus SCS for deceased donor kidney transplantation were eligible for inclusion. All donor types were included (donor after circulatory death (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 ratios (RR) with 95% confidence intervals (CI). Survival analyses (time-to-event) were performed with the generic inverse variance meta-analysis of hazard ratios (HR). Continuous scales of measurement were expressed as a mean difference (MD). Random effects models were used for data analysis. The primary outcome was the incidence of delayed graft function (DGF). Secondary outcomes included graft survival, incidence of primary non-function (PNF), DGF duration, economic implications, graft function, patient survival and incidence of acute rejection. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

Twenty-two studies (4007 participants) were included. The risk of bias was generally low across all studies and bias domains. The majority of the evidence compared non-oxygenated HMP with standard SCS (19 studies). The use of non-oxygenated HMP reduces the rate of DGF compared to SCS (16 studies, 3078 participants: RR 0.78, 95% CI 0.69 to 0.88; P < 0.0001; I2 = 31%; high certainty evidence). Subgroup analysis revealed that continuous (from donor hospital to implanting centre) HMP reduces DGF (high certainty evidence). In contrast, this benefit over SCS was not seen when non-oxygenated HMP was not performed continuously (low certainty evidence). Non-oxygenated HMP reduces DGF in both DCD and DBD settings in studies performed in the 'modern era' and when cold ischaemia times (CIT) were short. The number of perfusions required to prevent one episode of DGF was 7.69 and 12.5 in DCD and DBD grafts, respectively. Continuous non-oxygenated HMP versus SCS also improves one-year graft survival (3 studies, 1056 participants: HR 0.46, 0.29 to 0.75; P = 0.002; I2 = 0%; high certainty evidence). Assessing graft survival at maximal follow-up confirmed a benefit of continuous non-oxygenated HMP over SCS (4 studies, 1124 participants (follow-up 1 to 10 years): HR 0.55, 95% CI 0.40 to 0.77; P = 0.0005; I2 = 0%; high certainty evidence). This effect was not seen in studies where HMP was not continuous. The effect of non-oxygenated HMP on our other outcomes (PNF, incidence of acute rejection, patient survival, hospital stay, long-term graft function, duration of DGF) remains uncertain. Studies performing economic analyses suggest that HMP is either cost-saving (USA and European settings) or cost-effective (Brazil). One study investigated continuous oxygenated HMP versus non-oxygenated HMP (low risk of bias in all domains); the simple addition of oxygen during continuous HMP leads to additional benefits over non-oxygenated HMP in DCD donors (> 50 years), including further improvements in graft survival, improved one-year kidney function, and reduced acute rejection. One large, high-quality study investigated end-ischaemic oxygenated HMP versus SCS and found end-ischaemic oxygenated HMP (median machine perfusion time 4.6 hours) demonstrated no benefit compared to SCS. The impact of longer periods of end-ischaemic HMP is unknown. One study investigated NMP versus SCS (low risk of bias in all domains). One hour of end ischaemic NMP did not improve DGF compared with SCS alone. An indirect comparison revealed that continuous non-oxygenated HMP (the most studied intervention) was associated with improved graft survival compared with end-ischaemic NMP (indirect HR 0.31, 95% CI 0.11 to 0.92; P = 0.03). No studies investigated normothermic regional perfusion (NRP) or included any donors undergoing NRP.

Continuous non-oxygenated HMP is superior to SCS in deceased donor kidney transplantation, reducing DGF, improving graft survival and proving cost-effective. This is true for both DBD and DCD kidneys, both short and long CITs, and remains true in the modern era (studies performed after 2008). In DCD donors (> 50 years), the simple addition of oxygen to continuous HMP further improves graft survival, kidney function and acute rejection rate compared to non-oxygenated HMP. Timing of HMP is important, and benefits have not been demonstrated with short periods (median 4.6 hours) of end-ischaemic HMP. End-ischaemic NMP (one hour) does not confer meaningful benefits over SCS alone and is inferior to continuous HMP in an indirect comparison of graft survival. Further studies assessing NMP for viability assessment and therapeutic delivery are warranted and in progress.

The time to arrest donors after circulatory death is unpredictable and can vary. This leads to variable periods of warm ischemic damage prior to pancreas transplantation. There is little evidence supporting procurement team stand-down times based on donor time to death (TTD). We examined what impact TTD had on pancreas graft outcomes following donors after circulatory death (DCD) simultaneous pancreas-kidney transplantation. Data were extracted from the UK transplant registry from 2014 to 2022. Predictors of graft loss were evaluated using a Cox proportional hazards model. Adjusted restricted cubic spline models were generated to further delineate the relationship between TTD and outcome. Three-hundred-and-seventy-five DCD simultaneous kidney-pancreas transplant recipients were included. Increasing TTD was not associated with graft survival (adjusted hazard ratio HR 0.98, 95% confidence interval 0.68-1.41, P = .901). Increasing asystolic time worsened graft survival (adjusted hazard ratio 2.51, 95% confidence interval 1.16-5.43, P = .020). Restricted cubic spline modeling revealed a nonlinear relationship between asystolic time and graft survival and no relationship between TTD and graft survival. We found no evidence that TTD impacts pancreas graft survival after DCD simultaneous pancreas-kidney transplantation; however, increasing asystolic time was a significant predictor of graft loss. Procurement teams should attempt to minimize asystolic time to optimize pancreas graft survival rather than focus on the duration of TTD.

To investigate whether ischemia alters donor kidney metabolism and whether these changes are associated with organ function.

An unmet need in kidney transplantation is the ability to predict posttransplant organ function before transplantation. Key to such viability testing is a profound understanding of the organ's complex biochemistry and how ischemia, inevitable during the transplantation process, influences this.

First, metabolic changes in perfusate glucose, lactate, and 20 amino acids, induced by no, 1 hour of warm, or 22 hours of cold ischemia, were investigated during 4-hour perfusion of pig kidneys with autologous whole blood (n = 6/group), simulating the ischemia-reperfusion phase of transplantation. Next, we confirmed similar metabolic changes during normothermic preservation of pigs (n = 3/group; n = 4 for cold ischemia) and discarded human kidneys (n = 6) perfused with a red blood cell-based perfusate.

At 2 hours of perfusion with autologous whole blood, abundances of 17/20 amino acids were significantly different between groups, reflecting the type of ischemia. Amino acid changes at 15 minutes and 2 hours of perfusion correlated with future kidney function during perfusion. Similar metabolic patterns were observed during perfusion preservation of pig and discarded human donor kidneys, suggesting an opportunity to assess kidney viability before transplantation.

Perfusate metabolite changes during normothermic kidney perfusion represent a unique noninvasive opportunity to assess graft viability. These findings now need validation in transplant studies.

The growing disparity between the demand for transplants and the available donor supply, coupled with an aging donor population and increasing prevalence of chronic diseases, highlights the urgent need for the development of platforms enabling reconditioning, repair, and regeneration of deceased donor organs. This necessitates the ability to preserve metabolically active kidneys ex vivo for days. However, current kidney normothermic machine perfusion (NMP) approaches allow metabolic preservation only for hours. Here we show that human kidneys discarded for transplantation can be preserved in a metabolically active state up to 4 days when perfused with a cell-free perfusate supplemented with TCA cycle intermediates at subnormothermia (25 °C). Using spatially resolved isotope tracing we demonstrate preserved metabolic fluxes in the kidney microenvironment up to Day 4 of perfusion. Beyond Day 4, significant changes were observed in renal cell populations through spatial lipidomics, and increases in injury markers such as LDH, NGAL and oxidized lipids. Finally, we demonstrate that perfused kidneys maintain functional parameters up to Day 4. Collectively, these findings provide evidence that this approach enables metabolic and functional preservation of human kidneys over multiple days, establishing a solid foundation for future clinical investigations.

Due to the shortage of kidneys donated for transplantation, surgeons are forced to use the organs with an elevated risk of poor function or even failure. Although the existing methods for pre-transplant quality evaluation have been validated over decades in population cohort studies across the world, new methods are needed as long as delayed graft function or failure in a kidney transplant occurs. In this study, we explored the potential of utilizing photoacoustic (PA) imaging during normothermic machine perfusion (NMP) as a means of evaluating kidney quality. We closely monitored twenty-two porcine kidneys using 3D PA imaging during a two-hour NMP session. Based on biochemical analyses of perfusate and produced urine, the kidneys were categorized into 'non-functional' and 'functional' groups. Our primary focus was to quantify oxygenation (sO2) within the kidney cortical layer of depths 2 mm, 4 mm, and 6 mm using two-wavelength PA imaging. Next, receiver operating characteristic (ROC) analysis was performed to determine an optimal cortical layer depth and time point for the quantification of sO2 to discriminate between functional and non-functional organs. Finally, for each depth, we assessed the correlation between sO2 and creatinine clearance (CrCl), oxygen consumption (VO2), and renal blood flow (RBF). We found that hypoxia of the renal cortex is associated with poor renal function. In addition, the determination of sO2 within the 2 mm depth of the renal cortex after 30 min of NMP effectively distinguishes between functional and non-functional kidneys. The non-functional kidneys can be detected with the sensitivity and specificity of 80% and 85% respectively, using the cut-off point of sO2 < 39%. Oxygenation significantly correlates with RBF and VO2 in all kidneys. In functional kidneys, sO2 correlated with CrCl, which is not the case for non-functional kidneys. We conclude that the presented technique has a high potential for supporting organ selection for kidney transplantation.

Fibrosis in kidney allografts is a major post-transplant complication that contributes to graft failure. Lately, multiple potent inhibitors of fibrosis-related pathways have been developed such as galunisertib, an inhibitor of the transforming growth factor-beta (TGF-β/TGFβ1) signalling pathway. This drug, however, poses risks for adverse effects when administered systemically. Therefore, we devised a new repurposing strategy in which galunisertib is administered ex vivo. We combined machine perfusion and tissue slices to explore the antifibrotic effects of galunisertib in renal grafts.

Porcine kidneys were subjected to 30 min of warm ischaemia, 24 h of oxygenated hypothermic machine perfusion and 6 h of normothermic machine perfusion with various treatments (i.e. untreated control, TGFβ1, galunisertib or TGFβ1 + galunisertib; n = 8 kidneys per group). To determine whether effects persisted upon ceasing treatment, kidney slices were prepared from respective kidneys and incubated for 48 h.

Galunisertib treatment improved general viability without negatively affecting renal function or elevating levels of injury markers or by-products of oxidative stress during perfusion. Galunisertib also reduced inflammation and, more importantly, reduced the onset of fibrosis after 48 h of incubation.

Our findings demonstrate the value of using machine perfusion for administering antifibrotic drugs such as galunisertib, proving it to be an effective example of repurposing.

Ex vivo machine perfusion is a novel preservation technique for storing and assessing marginal kidney grafts. All ex vivo perfusion techniques have advantages and shortcomings. The current study analyzed whether a combination of oxygenated hypothermic machine perfusion (oxHMP) followed by a short period of normothermic ex vivo kidney perfusion (NEVKP) could combine the advantages of both techniques.

Porcine kidneys were exposed to 30 min of warm ischemia followed by perfusion. Kidneys underwent either 16-h NEVKP or 16-h oxHMP. The third group was exposed to 16-h oxHMP followed by 3-h NEVKP (oxHMP + NEVKP group). After contralateral nephrectomy, grafts were autotransplanted and animals were followed up for 8 d.

All animals survived the follow-up period. Grafts preserved by continuous NEVKP showed improved function with lower peak serum creatinine and more rapid recovery compared with the other 2 groups. Urine neutrophil gelatinase-associated lipocalin, a marker of kidney injury, was found to be significantly lowered on postoperative day 3 in the oxHMP + NEVKP group compared with the other 2 groups.

A short period of NEVKP after oxHMP provides comparable short-term outcomes to prolonged NEVKP and is superior to oxHMP alone. A combination of oxHMP with end-ischemic NEVKP could be an attractive, practical strategy to combine the advantages of both preservation techniques.

Normothermic machine perfusion (NMP) aims to preserve organs ex vivo by simulating physiological conditions such as body temperature. Recent advancements in NMP system design have prompted the development of clinically effective devices for liver, heart, lung, and kidney transplantation that preserve organs for several hours/up to 1 d. In preclinical studies, adjustments to circuit structure, perfusate composition, and automatic supervision have extended perfusion times up to 1 wk of preservation. Emerging NMP platforms for ex vivo preservation of the pancreas, intestine, uterus, ovary, and vascularized composite allografts represent exciting prospects. Thus, NMP may become a valuable tool in transplantation and provide significant advantages to biomedical research. This review recaps recent NMP research, including discussions of devices in clinical trials, innovative preclinical systems for extended preservation, and platforms developed for other organs. We will also discuss NMP strategies using a global approach while focusing on technical specifications and preservation times.

In recent years, normothermic machine perfusion (NMP) has emerged in conversation surrounding organ preservation and transplantation techniques with the goal of improving patient and clinical outcomes. This is in great attempt to address the rate of non-utilization and the shortage of available organs in kidney transplantation. This focus in mind, normothermic perfusion presents itself as a potential tool to mimic physiological conditions and improve current preservation methods, such as static cold storage. This review serves to improve understanding of the observed connection between the consequences of ischemia and reperfusion injury and traditional preservation techniques as well as how renal NMP may mitigate these issues. Previous studies suggest that reducing time in static cold storage methods by promoting the normothermic perfusion model results in decreased delayed graft function and post-transplant complications. This review also aims to present the immense clinical potential NMP has on future kidney transplantation success and what this means for the fields of nephrology and transplantation. While great strides have been made to evaluate normothermic perfusion's impact on kidney graft viability and transplant success, future research into unified protocol, clinically relevant biomarkers, cost-utility analysis, and use with associated therapeutic and imaging modalities is paramount.

Stiffness plays a vital role in diagnosing renal fibrosis. However, perfusion influences renal stiffness in various chronic kidney diseases. Therefore, we aimed to characterize the effect of tissue perfusion on renal stiffness and tissue fluidity measured by tomoelastography based on multifrequency magnetic resonance elastography in an ex vivo model. Five porcine kidneys were perfused ex vivo in an MRI-compatible normothermic machine perfusion setup with adjusted blood pressure in the 50/10-160/120 mmHg range. Simultaneously, renal cortical and medullary stiffness and fluidity were obtained by tomoelastography. For the cortex, a statistically significant (p < 0.001) strong positive correlation was observed between both perfusion parameters (blood pressure and resulting flow) and stiffness (r = 0.95, 0.91), as well as fluidity (r = 0.96, 0.92). For the medulla, such significant (p < 0.001) correlations were solely observed between the perfusion parameters and stiffness (r = 0.88, 0.71). Our findings demonstrate a strong perfusion dependency of renal stiffness and fluidity in an ex vivo setup. Moreover, changes in perfusion are rapidly followed by changes in renal mechanical properties-highlighting the sensitivity of tomoelastography to fluid pressure and the potential need for correcting mechanics-derived imaging biomarkers when addressing solid structures in renal tissue.

Normothermic machine perfusion (NMP) has reshaped organ preservation in recent years. In this preclinical study, prolonged normothermic perfusions of discarded human kidney grafts were performed in order to investigate perfusion dynamics and identify potential quality and assessment indicators. Five human discarded kidney grafts were perfused normothermically (37°C) for 48 h using the Kidney Assist device with a red-blood-cell based perfusate with urine recirculation. Perfusion dynamics, perfusate and urine composition as well as injury markers were measured and analyzed. Donor age ranged from 41 to 68 years. All but one kidney were from brain dead donors. Perfusions were performed successfully for 48 h with all discarded kidneys. Median arterial flow ranged from 405 to 841 mL/min. All kidneys excreted urine until the end of perfusion (median 0.43 mL/min at the end of perfusion). While sodium levels were consistently lower in urine compared to perfusate samples, this was only seen for chloride and potassium in kidney KTX 2. Lactate, AST, LDH as well as pro-inflammatory cytokines increased over time, especially in kidneys KTX 3 and 4. Ex vivo normothermic perfusion is able to identify patterns of perfusion, biological function, and changes in inflammatory markers in heterogenous discarded kidney grafts.

Normothermic machine perfusion (NMP) provides a platform for pre-transplant kidney quality assessment that is essential for the use of marginal donor kidneys. Laser speckle contrast imaging (LSCI) presents distinct advantages as a real-time and noncontact imaging technique for measuring microcirculation. In this study, we aimed to assess the value of LSCI in visualizing renal cortical perfusion and investigate the additional value of dual-side LSCI measurements compared to single aspect measurement during NMP.

Porcine kidneys were obtained from a slaughterhouse and then underwent NMP. LSCI was used to measure one-sided cortical perfusion in the first 100 min of NMP. Thereafter, the inferior renal artery branch was occluded to induce partial ischemia and LSCI measurements on both ventral and dorsal sides were performed.

LSCI fluxes correlated linearly with the renal blood flow (R2  = 0.90, p < 0.001). After renal artery branch occlusion, absence of renal cortical perfusion could be visualized and semiquantified by LSCI. The overall ischemic area percentage of the ventral and dorsal sides was comparable (median interquartile range [IQR], 38 [24-43]% vs. 29 [17-46]%, p = 0.43), but heterogenous patterns between the two aspects were observed. There was a significant difference in oxygen consumption (mean ± standard deviation [SD], 2.57 ± 0.63 vs. 1.83 ± 0.49 mLO2 /min/100 g, p < 0.001), urine output (median [IQR], 1.3 [1.1-1.7] vs. 0.8 [0.6-1.3] mL/min, p < 0.05), lactate dehydrogenase (mean ± SD, 768 ± 370 vs. 905 ± 401 U/L, p < 0.05) and AST (mean ± SD, 352 ± 285 vs. 462 ± 383 U/L, p < 0.01) before and after renal artery occlusion, while no significant difference was found in creatinine clearance, fractional excretion of sodium, total sodium reabsorption and histological damage.

LSCI fluxes correlated linearly with renal blood flow during NMP. Renal cortical microcirculation and absent perfusion can be visualized and semiquantified by LSCI. It provides a relative understanding of perfusion levels, allowing for a qualitative comparison between regions in the kidney. Dual-side LSCI measurements are of added value compared to single aspect measurement and renal function markers.

Currently, there is a shortfall in the number of suitable organs available for transplant resulting in a high number of patients on the active transplant waiting lists worldwide. To address this shortfall and increase the utilization of donor organs, the acceptance criteria for donor organs is gradually expanding including increased use of organs from donation after circulatory death. Use of such extended criteria donors and exposure of organs to more prolonged periods of warm or cold ischaemia also increases the risk of primary graft dysfunction occurring. Normothermic machine perfusion (NMP) offers a unique opportunity to objectively assess donor organ function outside the donor body and potentially recondition those deemed unsuitable on initial evaluation prior to implantation in the recipient. Furthermore, NMP provides a platform to support the use of established and novel therapeutics delivered directly to the organ, without the need to worry about potential deleterious 'off-target' side effects typically considered when treating the whole patient. This review will explore some of the novel therapeutics currently being added to perfusion platforms during NMP experimentally in an attempt to improve organ function and post-transplant outcomes.

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.

Optimizing deceased donor organ utilization is gaining recognition as a topical and important issue, both in the United Kingdom (UK) and globally. This review discusses pertinent issues in the field of organ utilization, with specific reference to UK data and recent developments within the UK.

A multifaceted approach is likely required in order to improve organ utilization. Having a solid evidence-base upon which transplant clinicians and patients on national waiting lists can base decisions regarding organ utilization is imperative in order to bridge gaps in knowledge regarding the optimal use of each donated organ. A better understanding of the risks and benefits of the uses of higher risk organs, along with innovations such as novel machine perfusion technologies, can help clinician decision-making and may ultimately reduce the unnecessary discard of precious deceased donor organs.

The issues facing the UK with regards to organ utilization are likely to be similar to those in many other developed countries. Discussions around these issues within organ donation and transplantation communities may help facilitate shared learning, lead to improvements in the usage of scarce deceased donor organs, and enable better outcomes for patients waiting for transplants.

Pancreas transplantation is the only curative treatment for patients with complicated diabetes, and organ shortage is a common and increasing problem. Strategies to expand the donor pool are needed, and normothermic ex vivo perfusion of the pancreas has the potential to test and repair grafts before implantation. Between January 2021 and April 2022, six human pancreases, declined for transplantation or islet isolation, were perfused using a previously established method by our group. All 6 cases were successfully perfused for 4 h, with minimal edema. The mean age of the donors was 44.16 ± 13.8 years. Five grafts were obtained from neurological death donors, and one was obtained from a donation after cardiac death. The mean glucose and lactate levels decreased throughout perfusion and insulin levels increased. All 6 grafts were metabolically active during perfusion and histopathology showed minimal tissue injury and no edema. Human normothermic ex vivo perfusion of the pancreas is feasible and safe and has the potential to expand the donor pool. Future studies will focus on tests and biomarkers for the assessment of grafts.

The use of high-risk renal grafts for transplantation requires the optimization of pretransplant assessment and preservation reconditioning strategies to decrease the organ discard rate and to improve short- and long-term clinical outcomes. Active oxygenation is increasingly recognized to play a central role in dynamic preservation strategies, independent of preservation temperature, to recondition mitochondria and to restore the cellular energy profile. The oxygen-related decrease in mitochondrial succinate accumulation ameliorates the harmful effects of ischemia-reperfusion injury. The differences between normothermic and hypothermic machine perfusion with regard to organ assessment, preservation, and reconditioning, as well as the logistic and economic implications, are factors to take into consideration for implementation at a local level. Therefore, these different techniques should be considered complementary to the perfusion strategy selected depending on functional intention and resource availability. This review provides an overview of the current clinical evidence of normothermic and oxygenated hypothermic machine perfusion, either as a continuous or end-ischemic preservation strategy, and future perspectives.