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Background: Kidney transplantation is the optimal treatment of end-stage renal disease. Extracellular vesicles (EVs) have tremendous therapeutic potential, but their role in modulating immune responses in kidney transplantation remains unclear. Methods: We performed a systematic review and meta-analysis to investigate the therapeutic efficacy of EVs in preclinical kidney transplant models. Outcomes for meta-analysis were graft survival and renal function. Subgroup analysis was conducted between immune cell derived EVs (immune cell-EVs) and mesenchymal stromal cell derived EVs (MSC-EVs). Results: Seven studies published from 2013 to 2021 were included. The overall effects showed that EVs had a positive role in prolonging allograft survival (standardized mean difference (SMD) = 2.00; 95% confidence interval (CI), 0.79 to 3.21; P < 0.01; I2 = 94%), reducing serum creatinine (SCr) (SMD = -2.19; 95%CI, −3.35 to −1.04; P < 0.01; I2 = 93%) and blood urea nitrogen (BUN) concentrations (SMD = -1.69; 95%CI, −2.98 to −0.40; P = 0.01; I2 = 94%). Subgroup analyses indicated that only immune cell-EVs significantly prolonged graft survival and improve renal function but not MSC-EVs. Conclusions: EVs are promising candidates to suppress allograft rejection and improve kidney transplant outcome. Immune cell-EVs showed their superiority over MSC-EVs in prolonging graft survival and improving renal function. For interpretation of the outcomes, additional studies are needed to validate these findings.

INTRODUCTION: Ageing of the general population has led to an increase in the use of suboptimal kidneys from expanded criteria donation after brain death (ECD-DBD) and donation after circulatory death (DCD) donors. However, these kidneys have inferior graft outcomes and lower rates of immediate function. Normothermic machine perfusion (NMP) may improve outcomes of these suboptimal donor kidneys. Previous non-randomized studies have shown the safety of this technique and suggested its efficacy in improving the proportion of immediate functioning kidneys compared to static cold storage (SCS). However, its additional value to hypothermic machine perfusion (HMP), which has already been proved superior to SCS, has not yet been established.METHODS AND ANALYSIS: This single-center, open-label, randomized controlled trial aims to assess immediate kidney function after 120 minutes additional, end-ischemic NMP compared to HMP alone. Immediate kidney function is defined as no dialysis treatment in the first week after transplant. Eighty recipients on dialysis at the time of transplant who receive an ECD-DBD or DCD kidney graft are eligible for inclusion. In the NMP group, the donor kidney is taken of HMP upon arrival in the recipient hospital and thereafter put on NMP for 120 minutes at 37 degrees Celsius followed by transplantation. In the control group, donor kidneys stay on HMP until transplantation. The primary outcome is immediate kidney function.ETHICS AND DISSEMINATION: The protocol has been approved by the Medical Ethical Committee of Erasmus Medical Center (2020-0366). Results of this study will be submitted to peer-reviewed journals.REGISTRATION: registered in clinicaltrials.gov (NCT04882254).HIGHLIGHTS: This is the first RCT to compare additional NMP to HMP alone.Extensive sampling will offer in-depth analysis of kidney physiology during NMP.This RCT may help identify biomarkers to predict clinical outcomes during NMP.Biomarkers can help develop NMP as assessment tool for declined kidneys.

We present an updated overview of the literature comparing normothermic with hypothermic machine perfusion in porcine kidneys. We conducted a systematic literature review in Embase, Medline Epub (Ovid), Cochrane Central, Web of Science, and Google Scholar on studies comparing normothermic (NMP) to hypothermic machine perfusion (HMP) in porcine kidneys. A meta‐analysis was judged inappropriate because of heterogeneity in study design and perfusion methods. The quality of evidence of each included study was assessed. We included 8 studies. One out of 5 studies reported a significant difference in peak renal blood flow in favor of NMP. Oxygen consumption was significantly higher in NMP kidneys in 2 out of 5 studies. Peak creatinine clearance in NMP was significantly higher than that in HMP in 1 out of 6 studies. Two out of 4 studies reported a higher degree of epithelial vacuolation in kidneys receiving NMP over HMP. None of the studies found a significant difference between NMP and HMP in peak serum creatinine or graft survival after autotransplantation. The results need to be interpreted with caution in view of the diversity in perfusion protocols, the low quality of evidence, and the limited sample sizes.

Background Since the introduction of the Model for End-stage Liver disease criteria in 2002, more combined liver kidney transplants are performed. Until 2017, no standard allocation policy for combined liver kidney transplant (CLKT) was available and each transplant center decided eligibility for CLKT or liver transplant alone (LTA) on a case-by-case basis. The aim of this systematic review was to compare the clinical outcomes of CLKT compared to LTA in patients with renal dysfunction. Methods Databases were systematically searched for studies published between January 2010 and March 2021. Outcomes were expressed as risk ratios and pooled with a random-effects model. The primary outcome was patient survival. Results Four studies were included. No differences were observed for mortality risk at 1 year (risk ratio (RR) 1.03 [confidence interval (CI) 0.97–1.09], 3 years (RR 1.06 [CI 0.99–1.13]) and 5 years (RR 1.08 [CI 0.98–1.19]). The risk of graft loss was similar in the first year (RR 1.10 [CI 0.93–1.30], while 3-year risk of graft loss was significantly lower in CLKT patients (RR 1.15 [CI 1.08–1.24]). Conclusions CLKT has similar short-term graft and patient survival as LTA in patients with renal dysfunction. More data is needed to decide from which KDIGO stage patients benefit the most from CLKT.