The risk of graft loss 5 years after kidney transplantation is increased if cold ischemia time exceeds 14 hours

Advances in the study of B cells in renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) is a non-negligible clinical challenge for clinicians in surgeries such as renal transplantation. Functional loss of renal tubular epithelial cell (TEC) in IRI leads to the development of acute kidney injury, delayed graft function (DGF), and allograft rejection. The available evidence indicates that cellular oxidative stress, cell death, microvascular dysfunction, and immune response play an important role in the pathogenesis of IRI. A variety of immune cells, including macrophages and T cells, are actively involved in the progression of IRI in the immune response. The role of B cells in IRI has been relatively less studied, but there is a growing body of evidence for the involvement of B cells, which involve in the development of IRI through innate immune responses, adaptive immune responses, and negative immune regulation. Therefore, therapies targeting B cells may be a potential direction to mitigate IRI. In this review, we summarize the current state of research on the role of B cells in IRI, explore the potential effects of different B cell subsets in the pathogenesis of IRI, and discuss possible targets of B cells for therapeutic aim in renal IRI.

Long and Short-Term Effects of Hypothermic Machine Perfusion vs. Cold Storage on Transplanted Kidneys from Expanded Criteria Donors-A Matched Comparison Study

Hypothermic machine perfusion (HMP) has been shown to reduce delayed graft function (DGF)-rates in kidneys from expanded criteria donors (ECD) and may increase graft survival compared with static cold storage (SCS). This single-center, retrospective observational study aimed to evaluate this effect. The primary endpoint was the DGF-rate, defined as the use of dialysis in the first postoperative week, excluding the first 24 h. The main secondary endpoint was graft survival at 5 years. Recipients of ECD-kidneys between 2013 and 2021 with ≤2 grafts were included (n = 438). The SCS-kidneys were marginal-matched by propensity score to the HMP-group for donor age, cold ischemia time, and graft number. Multivariable adjusted analysis for confounders in the unmatched cohort and caliper-based ID-matching constituted sensitivity analyses. HMP showed a trend to lower DGF-rate in the marginal-matched comparison (9.2% vs. 16.1%, p = 0.063). This was strengthened by a significant benefit observed for HMP in both the sensitivity analyses: an adjusted OR of 0.45 (95% CI: 0.24; 0.84; p = 0.012) in the multivariable analysis and DGF-rate of 8.7% vs. 17.4% (p = 0.024) after ID-matching. The 5-year graft survival rate was >90% in both groups, with no benefit using HMP (HR = 0.79; 95% CI:0.39-1.16; p = 0.52). Our results suggest that HMP may be effective in decreasing DGF-rates, however, without any significant benefit in graft survival.

Proteomics reveals specific biological changes induced by the normothermic machine perfusion of donor kidneys with a significant up-regulation of Latexin

Renal normothermic machine perfusion (NMP) is an organ preservation method based on the circulation of a warm (35-37 °C) perfusion solution through the renal vasculature to deliver oxygen and nutrients. However, its biological effects on marginal kidneys are unclear. We therefore used mass spectrometry to determine the proteomic profile of kidney tissue and urine from eight organs reconditioned for 120 min using a Kidney Assist device. Biopsies were taken during the pre-implantation histological evaluation (T-1), at the start of back table preparation (T0), and after 60 and 120 min of perfusion (T60, T120). Urine samples were collected at T0 (urine produced in the first 15 min after the beginning of normothermic reperfusion), T30, T60 and T120. Multiple algorithms, support vector machine learning and partial least squares discriminant analysis were used to select the most discriminative proteins during NMP. Statistical analysis revealed the upregulation of 169 proteins and the downregulation of 196 during NMP. Machine learning algorithms identified the top 50 most discriminative proteins, five of which were concomitantly upregulated (LXN, ETFB, NUDT3, CYCS and UQCRC1) and six downregulated (CFHR3, C1S, CFI, KNG1, SERPINC1 and F9) in the kidney and urine after NMP. Latexin (LXN), an endogenous carboxypeptidase inhibitor, resulted the most-upregulated protein at T120, and this result was confirmed by ELISA. In addition, functional analysis revealed that the most strongly upregulated proteins were involved in the oxidative phosphorylation system and ATP synthesis, whereas the downregulated proteins represented the complement system and coagulation cascade. Our proteomic analysis demonstrated that even brief periods of NMP induce remarkable metabolic and biochemical changes in marginal organs, which supports the use of this promising technique in the clinic.

Complex Bench Surgery Does Not Increase the Risk of Vascular Complications after Pediatric Kidney Transplantation

INTRODUCTION

 Vascular complications are severe complications of pediatric kidney transplantation (KT). We aimed to investigate whether a complex bench surgery (BS) affects the outcomes.

METHODS

 All pediatric KT performed at the University Hospital of Padua from 2015 to 2019 were analyzed, comparing those in which a standard BS was possible to those that necessitated a complex BS. The rates of vascular complications, patients' outcome, and graft survival were compared in the two groups.

RESULTS

 Eighty KTs were performed in 78 patients with a median age of 11 years (interquartile range [IQR] 4.3-14) and a median body weight of 24 kg (IQR 13-37). Thirty-nine donor kidneys (49%) needed a complex BS due to anomalies of renal veins in 12 (31%) and renal arteries in 16 (41%). The remaining 11 grafts (28%) underwent an elongation of the vein. There was no difference in the rate of primary graft non function (p = 0.97), delayed graft function (p = 0.72), and overall survival (p = 0.27). The rates of vascular complications, bleedings, and venous graft thrombosis were similar (p = 0.51, p = 0.59, p = 0.78, respectively). No arterial thrombosis or stenosis was reported.

CONCLUSION

 Complex BS did not compromise survival of the graft and did not put the allograft at risk of vascular complications, such as bleedings or thrombosis.

Excellent Clinical Long-Term Outcomes of Kidney Transplantation From Small Pediatric Donors (Age ≤ 5 Years) Despite Early Hyperfiltration Injury

Background:

The use of small pediatric donors (age ≤ 5 years and body weight < 20kg) for adult transplant recipients is still regarded controversially in terms of early complications, long-term outcomes, and development of hyperfiltration injury due to body size mismatch.

Objective:

To investigate long-term outcomes of adult renal allograft recipients receiving a kidney from small pediatric donor (SPD) in terms of kidney function and early features of hyperfiltration injury such as histological changes and proteinuria.

Design:

Retrospective, single center study.

Settings:

Transplant center of the University Hospital of Basel, Switzerland.

Patients:

Adult renal allograft recipients receiving a kidney from a small pediatric donor at our center between 2005 and 2017.

Methods:

The outcome of 47 transplants from SPD were compared with 153 kidney transplants from deceased-standard criteria donors (SCD) occurring during the same time period. Incidence of clinical signs of hyperfiltration injury (eg, proteinuria) was investigated. According to our policy, surveillance biopsies were taken at 3 and 6 months post-transplant and were evaluated in terms of signs of hyperfiltration injury.

Results:

At a median follow-up of 2.3 years post-transplant, death-censored graft survival of SPD was comparable to transplants from SCD (94% vs 93%; P = .54). Furthermore, allograft function at last follow-up (estimated glomerular filtration rate–Modification of Diet in Renal Disease) was significantly higher in pediatric transplant (80 vs 55 ml/min/1.73 m2, P = .002). We found histological signs of early hyperfiltration injury in 55% of SPD. There was an equally low proteinuria in both groups during follow-up.

Limitations:

It is a single center and retrospective observational study with small sample size. The outcomes were investigated in a well-selected population of recipients with low body mass index, low immunological risk, and well-controlled hypertension and was not compared with equal selected group of recipients.

Conclusions:

Early histological and clinical signs of hyperfiltration injury in SPD is frequent. Despite the hyperfiltration injury, there is an equal allograft survival and even superior allograft function in SPD compared with SCD during follow-up. This observation supports the concept of high adaptive capacity of pediatric donor kidneys.

Cold Ischemia Time, Kidney Donor Profile Index, and Kidney Transplant Outcomes: A Cohort Study

Rationale & Objective

An average of 3,280 recovered deceased donor kidneys are discarded annually in the United States. Increased cold ischemia time is associated with an increased rate of organ decline and subsequent discard. Here we examined the effect of prolonged cold ischemia time on kidney transplant outcomes.

Study Design

Retrospective observational study.

Setting & Participants

Recipients of deceased donor kidney transplants in the United States from 2000 to 2018.

Exposure

Recipients of deceased donor kidneys were divided based on documented cold ischemia time: ≤16, 16-24, 24-32, 32-40, and >40 hours.

Outcomes

The incidence of delayed graft function, primary nonfunction, and 10-year death-censored graft survival.

Analytical Approach

The Kaplan-Meier method was used to generate survival curves, and the log rank test was used to compare graft survival.

Results

The rate of observed delayed graft function increased with cold ischemia time (20.9%, 28.1%, 32.4%, 37.5%, and 35.8%). Primary nonfunction also showed a similar increase with cold ischemia time (0.6%, 0.9%, 1.3%, 2.1%, and 2.3%), During a median follow-up time of 4.6 years, 37,301 recipients experienced death-censored graft failure. Analysis based on kidney donor profile index (KDPI) demonstrated significant differences in 10-year death-censored graft survival, with a death-censored graft survival in recipients of a kidney with a KDPI <85% of 71.0% (95% CI, 70.5%-71.5%), 70.5% (95% CI, 69.9%-71.0%), 69.6% (95% CI, 68.7%-70.4%), 65.5% (95% CI, 63.7%-67.3%), and 67.2% (95% CI, 64.6%-69.6%), compared to 53.5% (95% CI, 51.1%-55.8%), 50.7% (95% CI, 48.3%-53.1%), 50.3% (95% CI, 46.6%-53.8%), 50.7% (95% CI, 45.1%-56.1%), and 48.3% (95% CI, 40.0%-56.1%), for recipients of a kidney with a KDPI >85%.

Limitations

Heterogeneity of acceptance patterns among transplant centers, presence of confounding variables leading to acceptance of kidneys with prolonged cold ischemia times.

Conclusions

Cold ischemia time was associated with an increased risk of delayed graft function and primary nonfunction. However, the effect of increased cold ischemia time is modest and has less impact than the KDPI. Transplant programs should not consider prolonged cold ischemia time alone as a predominant reason to decline an organ, especially with a KDPI <85%.

Supervivencia del injerto y pacientes postrasplante renal de un hospital de Yucatán, México

Introducción: El trasplante de órganos es considerado como uno de los mayores avances de la medicina, no solo por recuperar la salud, sino por mejorar la calidad de vida de las personas con enfermedades crónicas o terminales.Objetivo: Identificar la supervivencia del injerto y pacientes sometidos a trasplante renal, así como los factores asociados en un Hospital de Alta Especialidad de Mérida, Yucatán, México.Material y Método: Estudio epidemiológico, observacional, longitudinal y retrospectivo donde se analizó el 100% de los expedientes disponibles de pacientes con trasplante renal, cuyo procedimiento se realizó a partir de enero de 2010 a diciembre de 2018.Resultados: La supervivencia global de los pacientes, fue de 96,7% a 1 año (IC:95%: 0,92-0,99) y 90,7% a 5 años (IC:95%: 0,75-0,97). La administración de terapia inmunosupresora previa al trasplante es un factor independiente de protección frente al desenlace de mortalidad o fallo del injerto (p=0,02). La supervivencia del injerto fue de 79,2% a 1 año (IC:95%: 0,71-0,85), y 41,37% a 5 años (IC:95%: 0,27-0,54). La dislipidemia (p=0,01), la Diabetes Tipo 2 (p=0,09), la isquemia fría (p=0,01), la isquemia caliente (p=0,02), la edad (p=0,03), y el Índice de Masa Corporal (p=0,01) fueron determinantes de la supervivencia del injerto.Conclusiones: La supervivencia del paciente y del injerto son distintas. La administración de inmunosupresor previo al trasplante afecta la supervivencia del paciente; mientras que factores de riesgo cardiovascular y los tiempos de isquemia estuvieron ligados a la supervivencia del injerto.

Donor Death Category Is an Effect Modifier Between Cold Ischemia Time and Post-transplant Graft Function in Deceased-Donor Kidney Transplant Recipients

Objectives: We aimed to analyze the effect of cold ischemia time (CIT) on post-transplant graft function through mixed-effect model analysis to reduce the bias caused by paired mate kidneys.

Methods: We reviewed all kidney transplantation records from 2015 to 2019 at our center. After applying the exclusion criteria, 561 cases were included for analysis. All donor characteristics, preservation and matching information, and recipient characteristics were collected. Transplant outcomes included delayed graft function (DGF) and estimated glomerular filtration rate (eGFR). Generalized linear mixed models were applied for analysis. We also explored potential effect modifiers, namely, donor death category, expanded criteria donors, and donor death causes.

Results: Among the 561 cases, 79 DGF recipients developed DGF, and 15 recipients who died after surgery were excluded from the eGFR estimation. The median stable eGFR of the 546 recipients was 60.39 (47.63, 76.97) ml/min/1.73 m². After adjusting for confounding covariates, CIT had a negative impact on DGF incidence [odds ratio = 1.149 (1.006, 1.313), P = 0.041]. In the evaluation of the impact on eGFR, the regression showed that CIT had no significant correlation with eGFR [β = −0.287 (−0.625, 0.051), P = 0.096]. When exploring potential effect modifiers, only the death category showed a significant interaction with CIT in the effect on eGFR (P_interaction = 0.027). In the donation after brain death (DBD) group, CIT had no significant effect on eGFR [β = 0.135 (−0.433, 0.702), P = 0.642]. In the donation after circulatory death/donation after brain death followed by circulatory death (DCD/DBCD) group, CIT had a significantly negative effect on eGFR [β= −0.700 (−1.196, −0.204), P = 0.006]. Compared to a CIT of 0–6 h, a CIT of 6–8 or 8–12 h did not decrease the post-transplant eGFR. CIT over 12 h (12–16 h or over 16 h) significantly decreased eGFR. With the increase in CIT, the regenerated eGFR worsened (P_trend = 0.011).

Conclusion: Considering the effect of paired mate kidneys, the risk of DGF increased with prolonged CIT. The donor death category was an effect modifier between CIT and eGFR. Prolonged CIT did not reduce the eGFR level in recipients from DBDs but significantly decreased the eGFR in recipients from DCDs/DBCDs. This result indicates the potential biological interaction between CIT and donor death category.

Normothermic kidney perfusion: An overview of protocols and strategies

Normothermic machine perfusion (NMP) technologies are emerging as an important adjunct in organ preservation and transplantation. NMP can enable the reduction or avoidance of cold ischemia and allows for pretransplant measurement of function and metabolic status to assess the suitability of the organ for transplantation. The key requirement of NMP is to provide an environment that is protective to the organ, ensures optimal oxygen delivery and supports metabolic function. Red blood cell-based solutions, artificial hemoglobin solutions, and acellular solutions have all been utilized in NMP. However, there is no clear consensus on perfusion protocols. A period of NMP after hypothermic preservation is the most commonly used strategy. As an alternative, several groups have developed and tested the feasibility of more prolonged periods of NMP. There are only a few reports of the application of NMP in clinical kidney transplantation and each uses different approach and conditions. This review details the rationale for NMP protocols considering duration of NMP and different perfusate compositions in experimental and clinical models. We also include a discussion on the mechanistic action of NMP, comparison of subnormothermic and hypothermic conditions, the different logistical approaches and future requirements.

Influence of cold ischemia time on the outcome of kidney transplants from donors aged 70 years and above - A Collaborative Transplant Study Report

BACKGROUND

The use of kidney allografts from ≥70-year-old donors has increased persistently over the last twenty years. Prolonged cold ischemia time (CIT) is well known to increase graft failure risk. However, despite their growing importance, no data is available on the impact of CIT specifically on survival of allografts from ≥70-year-old donors.

METHODS

47,585 kidney transplantations from expanded criteria donors (ECDs) performed during 2000-2017 and reported to the Collaborative Transplant Study were analysed. The impact of CIT on five-year death-censored graft and patient survival was studied for transplantations from <70- (n=33,305) and ≥70-year-old ECDs (n=14,280).

RESULTS

Compared to the reference of ≤12-hours CIT, a CIT of 13-18 hours did not increase the risk of graft failure significantly, neither for recipients of kidneys from <70- nor from ≥70-year-old ECDs. In contrast, graft failure risk increased significantly when CIT exceeded 18 hours, both in recipients of kidneys from <70- and, more pronounced, from ≥70-year-old ECDs (CIT 19-24 hours: hazard ratio (HR) =1.19 and =1.24; P<0.001; CIT ≥24 hours: HR=1.28 and =1.32, P<0.001 and =0.003, respectively). Within the 18-hour CIT interval, additional human leukocyte antigen (HLA) matching further improved survival of ECD transplants significantly, whereas the negative impact of a prolonged CIT >18 hours was stronger in >65-year-old recipients and for transplants with multiple HLA mismatches. The influence of CIT on patient survival was less pronounced.

CONCLUSIONS

CIT, as long it is kept ≤18 hours, has no significant impact on survival of kidney transplants even from ≥70-year-old ECDs.

Impact of Combinations of Donor and Recipient Ages and Other Factors on Kidney Graft Outcomes

As the availability of kidneys for transplantation continues to be outpaced by its growing demand, there has been an increasing utilization of older deceased donors in the last decades. Considering that definition of factors that influence deceased donor kidney transplant outcomes is important for allocation policies, as well as for individualization of post-transplant care, the purpose of this study was determine the risks for death censored graft survival and for patient survival conferred by older age of the donor in the context of the age of the recipient and of risk factors for graft and/or patient survival. The investigation was conducted in a single-center cohort of 5,359 consecutive first kidney transplants with adult deceased donors performed on non-prioritized adult recipients from January 1, 2002, to December 31, 2017. Death censored graft survival and patient survival were lower in older donors, whereas graft survival was higher and patient survival was lower in old recipients. The analyses of combinations of donor and recipient ages showed that death censored graft survival was lower in younger recipients in transplants from 18 to 59-year old donors, with standard or extended criteria, but no difference in graft survival was observed between younger and older recipients when the donor was ≥ 60-year old. Patient survival was higher in younger recipients in transplants with younger or older donors. Two to six HLA-A,B,DR mismatches, when compared to 0-1 MM, conferred risk for death-censored graft survival only in transplants from younger donors to younger recipients. Pre-transplant diabetes conferred risk for patient survival only in 50–59-year old recipients, irrespectively, of the age of the donor. Time on dialysis ≥ 10 years was a risk factor for patient survival in transplants with all donor-recipient age combinations, except in recipients with ≥ 60 years that received a kidney from an 18–49-year old donor. In conclusion, the results obtained in this study underline the importance of analyzing the impact of the age of the donor taking into consideration different scenarios.