Delayed graft function in kidney transplantation

APOD: A biomarker associated with oxidative stress in acute rejection of kidney transplants based on multiple machine learning algorithms and animal experimental validation

BACKGROUND

Oxidative stress is an unavoidable process in kidney transplantation and is closely related to the development of acute rejection after kidney transplantation. This study aimed to investigate the biomarkers associated with oxidative stress and their potential biological functions during acute rejection of kidney transplants.

METHODS

We identified Hub genes using five machine learning algorithms based on differentially expressed genes (DEGs) in the kidney transplant acute rejection dataset GSE50058 and oxidative stress-related genes (OS) obtained from the MSigDB database, and validated them with the datasets GSE1563 and GSE9493, as well as with animal experiments; Subsequently, we explored the potential biological functions of Hub genes using single-gene GSEA enrichment analysis; The Cibersort algorithm was used to explore the altered levels of infiltration of 22 immune cells during acute rejection of renal transplantation, and a correlation analysis between Hub genes and immune cells was performed; Finally, we also explored transcription factors (TFs), miRNAs, and potential drugs that regulate Hub genes.

RESULTS

We obtained a total of 57 genes, which we defined as oxidative stress-associated differential genes (DEOSGs), after intersecting DEGs during acute rejection of kidney transplants with OSs obtained from the MSigDB database; The results of enrichment analysis revealed that DEOSGs were mainly enriched in response to oxidative stress, response to reactive oxygen species, and regulation of oxidative stress and reactive oxygen species; Subsequently, we identified one Hub gene as APOD using five machine learning algorithms, which were validated by validation sets and animal experiments; The results of single-gene GSEA enrichment analysis revealed that APOD was closely associated with the regulation of immune signaling pathways during acute rejection of kidney transplants; The Cibersort algorithm found that the infiltration levels of a total of 10 immune cells were altered in acute rejection, while APOD was found to correlate with the expression of multiple immune cells; Finally, we also identified 154 TFs, 12 miRNAs, and 12 drugs or compounds associated with APOD regulation.

CONCLUSION

In this study, APOD was identified as a biomarker associated with oxidative stress during acute rejection of kidney transplants using multiple machine learning algorithms, which provides a potential therapeutic target for mitigating oxidative stress injury and reducing the incidence of acute rejection in kidney transplantation.

Transcriptomics-based exploration of shared M1-type macrophage-related biomarker in acute kidney injury after kidney transplantation and acute rejection after kidney transplantation

BACKGROUND

Macrophage type 1 (M1) cells are associated with both acute kidney injury (AKI) during kidney transplantation and acute rejection (AR) after kidney transplantation. Our study explored M1-related biomarkers involved in both AKI and AR and their potential biological functions.

METHODS

Based on the Gene Expression Omnibus (GEO) database, the immune cell infiltration levels and differentially expressed genes were examined in AKI and AR in the kidney transplantation; M1-related genes shared in AKI and AR were identified using weighted gene co-expression analysis (WGCNA) system. Subsequently, protein-protein interaction (PPI) networks and machine learning methods to identify Hub genes and construct diagnostic models. Both AKI model and AR rat models were built to validate the expressions of Hub genes and test the injury phenotype, oxidative stress markers, and inflammatory factors. Finally, the transcription factor (TF)-Hub gene and micro-RNA (miRNA)-Hub gene regulatory networks were constructed based on identified Hub genes.

RESULTS

Out of 2167 differential expression genes (DEGs) in AKI and 2100 DEGs in AR, four M1-related Hub genes were obtained by PPI networks and machine learning methods, namely GBP2, TYROBP, CCR5, and TLR8. The calibration curves in the nomogram diagnostic model for these four Hub genes suggested the same predictive probability as an ideal model for AKI and AR after kidney transplantation (AUC values of the area under the ROC curve were all >0.7). The same observations were confirmed in ischemia reperfusion injury (IRI) and AR rat models by identifying common four Hub genes (GBP2, TYROBP, TLR8, and CCR5). Western blots showed that these four Hub genes were significantly different in rat models of IRI and AR (all p<0.05). Compared with the control group, IRI and AR groups showed aggravated histopathological damage and increased secretion of oxidative stress markers and inflammatory factors in rat kidneys (all p<0.05). Finally, TF-Hub and miRNA-Hub gene regulatory networks were constructed to provide a theoretical basis for the regulation of Hub genes.

CONCLUSION

We identified four macrophage M1-related Hub genes shared among AKI and AR after kidney transplantation. These genes may be considered for diagnosis of AKI and AR after kidney transplantation.

Delivery of exogenous miR-19b by Wharton's Jelly Mesenchymal Stem Cells attenuates transplanted kidney ischemia/reperfusion injury by regulating cellular metabolism

Renal ischemia-reperfusion injury (IRI) frequently occurs following kidney transplantation, and exosomes derived from umbilical cord mesenchymal stem cells (WJ-MSC-Exos) have shown promise in treating IRI in transplanted kidneys. Our study delved into the potential mechanism of WJ-MSC-Exos in ameliorating IRI in transplanted kidneys, revealing that miR-19b is abundantly present in WJ-MSC-Exos. Both in vivo and in vitro experiments demonstrated that the absence of miR-19b abolished the protective effects of WJ-MSC-Exos against renal IRI. Mechanistically, miR-19b suppressed glycogen synthase kinase-3β (GSK3β) expression, thereby stabilizing PDXK protein through direct binding. Treatment with WJ-MSC-Exos led to reduced PDXK levels and enhanced pyridoxine accumulation, ultimately mitigating IRI in transplanted kidneys and I/R-induced HK2 cell apoptosis. These findings elucidate the underlying mechanism of WJ-MSC-Exos in alleviating IRI in transplanted kidneys, unveiling novel therapeutic targets for post-kidney transplantation IRI and providing a solid theoretical foundation for the clinical application of WJ-MSC-Exos in IRI treatment post-transplantation.

Hypothermia for expanded criteria organ donors in kidney transplantation in France (HYPOREME): a multicentre, randomised controlled trial

BACKGROUND

Expanded criteria donors help to increase graft availability, but provide organs with an increased risk of delayed graft function. We aimed to investigate whether donor hypothermia decreases the risk of delayed graft function compared with normothermia.

METHODS

We did this multicentre, randomised, controlled, parallel-arm trial at 53 intensive care units and transplant centres in France. We included expanded criteria donors in whom death was diagnosed based on neurological criteria, in compliance with French law, and the recipients of their kidney grafts. Eligible expanded criteria donors were older than 60 years or were aged 50-59 years and had at least two other risk factors (history of hypertension, creatinine >132 μmol/L, or cerebrovascular cause of death). Donors were randomly assigned to hypothermia (34-35°C) or normothermia (36·5-37·5°C). Machine perfusion was used routinely. Randomisation was done using a computer-generated, interactive, web-response system, in permuted blocks (block size six), stratified by centre. Outcome assessors were masked; investigator masking was not feasible. The primary outcome was the proportion of kidney recipients with delayed graft function, defined as renal replacement therapy within 7 days after transplantation, assessed in the modified intention-to-treat (mITT) population, which included all recipients who received at least one kidney from an expanded criteria donor, with the exception of those under guardianship. Secondary outcomes in expanded criteria donors were the number of organs recovered and transplanted, kidney function, body temperature, total volume of fluids administered, blood pressure and need for vasopressors and inotropes, and adverse events (cardiovascular events, metabolic disturbances, and coagulation disorders). Secondary outcomes in kidney recipients were duration of hospital stay, kidney graft function and vital status at day 7, day 28, 3 months, and 1 year after transplantation, and adverse events (infections, cardiovascular events, and surgical complications). Secondary outcomes were assessed in the mITT population. The trial was registered at ClinicalTrials.gov, NCT03098706.

FINDINGS

Between Nov 9, 2017, and March 3, 2021, 365 donors were randomly assigned, of whom 298 (151 [51%] male, 147 [49%] female) provided kidneys to 526 recipients (323 [61%] male, 203 [39%] female). 251 recipients in the hypothermia group and 275 recipients in the normothermia group were included in the analysis. Graft function was delayed in 40 (16%) of 251 recipients in the hypothermia group and 58 (21%) of 275 recipients in the normothermia group (odds ratio 0·71 [95% CI 0·44-1·13]; p=0·14; absolute difference -5·2% [95% CI 11·8-1·5]). Compared with donors in the normothermia group, donors in the hypothermia group had higher highest mean arterial pressure (115 mm Hg [SD 22] vs 108 mm Hg [20]; p=0·001). 1 year after transplantation, recipients in the hypothermia group had a lower mean creatinine concentration (152·4 μmol/L [SD 59·1] vs 169·7 μmol/L [51·4]; p=0·0351) and a higher mean creatinine clearance (42·3 mL/min/1·73 m2 [15·8] vs 40·5 mL/min/1·73 m2 [17·9]; p=0·0414) than those in the normothermia group. No significant differences between groups were identified for any other secondary outcomes.

INTERPRETATION

Hypothermia in expanded criteria donors whose organs were routinely stored using machine perfusion did not decrease the frequency of delayed kidney graft function. However, hypothermia was associated with a lower serum creatinine concentration and a higher creatinine clearance 1 year after transplantation.

FUNDING

French Ministry of Health and French Intensive Care Society.

Delayed Graft Function and the Renin-angiotensin System

Delayed graft function (DGF) is a form of acute kidney injury (AKI) and a common complication following kidney transplantation. It adversely influences patient outcomes increases the financial burden of transplantation, and currently, no specific treatments are available. In developing this form of AKI, activation of the renin-angiotensin system (RAS) has been proposed to play an important role. In this review, we discuss the role of RAS activation and its contribution to the pathophysiology of DGF following the different stages of the transplantation process, from procurement and ischemia to transplantation into the recipient and including data from experimental animal models. Deceased kidney donors, whether during cardiac or brain death, may experience activation of the RAS. That may be continued or further potentiated during procurement and organ preservation. Additional evidence suggests that during implantation of the kidney graft and reperfusion in the recipient, the RAS is activated and may likely remain activated, extrapolating from other forms of AKI where RAS overactivity is well documented. Of particular interest in this setting is the status of angiotensin-converting enzyme 2, a key RAS enzyme essential for the metabolism of angiotensin II and abundantly present in the apical border of the proximal tubules, which is the site of predominant injury in AKI and DGF. Interventions aimed at safely downregulating the RAS using suitable shorter forms of angiotensin-converting enzyme 2 could be a way to offer protection against DGF.

Application of ultrasound in early prediction of delayed graft function after renal transplantation

Kidney transplantation is currently the most effective treatment for end-stage renal disease. Delayed graft function (DGF) is one of the most common complications after renal transplantation and is a significant complication affecting graft function and the survival time of transplanted kidneys. Therefore, early diagnosis of DGF is crucial for guiding post-transplant care and improving long-term patient survival. This article will summarize the pathological basis and clinical characteristics of DGF after kidney transplantation, with a focus on contrast-enhanced ultrasound. It will analyze the current application status of ultrasound technology in DGF diagnosis and provide a comprehensive review of the clinical applications of ultrasound technology in this field, serving as a reference for the further application of ultrasound technology in kidney transplantation.

Development and validation of a novel nomogram model for predicting delayed graft function in deceased donor kidney transplantation based on pre-transplant biopsies

BACKGROUND

Delayed graft function (DGF) is an important complication after kidney transplantation surgery. The present study aimed to develop and validate a nomogram for preoperative prediction of DGF on the basis of clinical and histological risk factors.

METHODS

The prediction model was constructed in a development cohort comprising 492 kidney transplant recipients from May 2018 to December 2019. Data regarding donor and recipient characteristics, pre-transplantation biopsy results, and machine perfusion parameters were collected, and univariate analysis was performed. The least absolute shrinkage and selection operator regression model was used for variable selection. The prediction model was developed by multivariate logistic regression analysis and presented as a nomogram. An external validation cohort comprising 105 transplantation cases from January 2020 to April 2020 was included in the analysis.

RESULTS

266 donors were included in the development cohort, 458 kidneys (93.1%) were preserved by hypothermic machine perfusion (HMP), 96 (19.51%) of 492 recipients developed DGF. Twenty-eight variables measured before transplantation surgery were included in the LASSO regression model. The nomogram consisted of 12 variables from donor characteristics, pre-transplantation biopsy results and machine perfusion parameters. Internal and external validation showed good discrimination and calibration of the nomogram, with Area Under Curve (AUC) 0.83 (95%CI, 0.78-0.88) and 0.87 (95%CI, 0.80-0.94). Decision curve analysis demonstrated that the nomogram was clinically useful.

CONCLUSION

A DGF predicting nomogram was developed that incorporated donor characteristics, pre-transplantation biopsy results, and machine perfusion parameters. This nomogram can be conveniently used for preoperative individualized prediction of DGF in kidney transplant recipients.

Urinary Biomarkers for Cell Cycle Arrest TIMP-2 and IGFBP7 for Prediction of Graft Function Recovery after Kidney Transplantation

TIMP-2 and IGFBP7 have been identified and validated for the early detection of renal injury in critically ill patients, but data on recovery of allograft function after kidney transplantation (KTx) are scarce. In a prospective observational multicenter cohort study of renal transplant recipients, urinary [TIMP-2] × [IGFBP7] was evaluated daily from day 1 to 7 after KTx. Different stages of early graft function were defined: immediate graft function (IGF) (decrease ≥ 10% in serum creatinine (s-crea) within 24 h post KTx); slow graft function (SGF) (decrease in s-crea < 10% within 24 h post KTx); and delayed graft function (DGF) (any dialysis needed within the first week after KTx). A total of 186 patients were analyzed. [TIMP-2] × [IGFBP7] was significantly elevated as early as day 1 in patients with DGF compared to SGF and IGF. ROC analysis of [TIMP-2] × [IGFBP7] at day 1 post-transplant for event "Non-DGF" revealed a cut-off value of 0.9 (ng/mL)2/1000 with a sensitivity of 87% and a specificity of 71%. The positive predictive value for non-DGF was 93%. [TIMP-2] × [IGFBP7] measured at day 1 after KTx can predict early recovery of transplant function and is therefore a valuable biomarker for clinical decision making.

The effect of goal-directed fluid therapy on delayed graft function in kidney transplant recipients: A systematic review and meta-analysis

Delayed graft function (DGF) is a common post-operative complication with potential long-term sequelae for many kidney transplant recipients, and hemodynamic factors and fluid status play a role. Fixed perioperative fluid infusions are the standard of care, but more recent evidence in the non-transplant population has suggested benefit with goal-directed fluid strategies based on hemodynamic targets. We searched MEDLINE, EMBASE, Cochrane Controlled Trials Registry and Google Scholar through December 2022 for randomized controlled trials comparing risk of DGF between goal-directed and conventional fluid therapy in adults receiving a living or deceased donor kidney transplant. Effect estimates were reported with odds ratios (OR) and pooled using random effects meta-analysis. We identified 4 studies (205 participants) that met the inclusion criteria. The use of goal-directed fluid therapy had no significant effect on DGF (OR 1.37 95% CI, 0.34-5.6; p = 0.52; I2 = 0.11). Subgroup analysis examining effects among deceased and living kidney donation did not reveal significant differences in the effects of fluid strategy on DGF between subgroups. Overall, the strength of the evidence for goal-directed versus conventional fluid therapy to reduce DGF was of low certainty. Our findings highlight the need for larger trials to determine the effect of goal-directed fluid therapy on this patient-centered outcome.

Untargeted NMR-based metabolomics analysis of kidney allograft perfusates identifies a signature of delayed graft function

INTRODUCTION

Kidney transplantation (KTx) necessarily conveys an ischemia/reperfusion (I/R) process, which impacts on allograft outcomes. Delayed graft function (DGF) is defined as a non-decrease of serum creatinine by at least 10% daily on 3 consecutive days during the first 7 days post-KTx. DGF significantly conditions both short- and long-term graft outcomes. Still there is a lack of DGF predictive biomarkers.

OBJECTIVES

This study aimed to explore the potential of kidney graft perfusate metabolomics to predict DGF occurrence.

METHODS

49 human perfusates from grafts categorized upon donor type [donation after brain death (DBD)/donation after circulatory death (DCD)] and DGF occurrence and 19 perfusates from a murine model classified upon death type (DBD/DCD) were collected and analyzed by NMR-based metabolomics.

RESULTS

The multivariate analysis of the murine data highlighted significant differences between perfusate metabolomes of DBD versus DCD. These differences were similarly observed in the human perfusates. After correcting for the type of donor, multivariate analysis of human data demonstrated a metabolomics signature that could be correlated with DGF occurrence.

CONCLUSIONS

The metabolome of kidney grafts is influenced by the donor's type in both human and pre-clinical studies and could be correlated with DGF in the human DBD cohort. Thus, metabolomic analysis of perfusate applied prior to KTx may represent a new predictive tool for clinicians in a more personalized management of DGF. Moreover, our data paves the way to better understand the impact of donor's types on the biochemical events occurring between death and the hypothermic storage.

Histopathological Features and Role of Allograft Kidney Biopsy Among Recipients With Prolonged Delayed Graft Function: A Review

Delayed graft function (DGF) is an early posttransplant complication predictive of adverse outcomes. This "acute kidney injury of transplantation" is often defined as allograft dysfunction requiring renal replacement within 7 d posttransplantation. DGF is an important area of study because it is emerging with efforts to expand the donor pool and address the supply-demand gap in kidney transplantation. DGF is often caused by severe kidney injury mechanisms because of multiple donors, recipients, and immunologic factors. The role of kidney biopsy, particularly in prolonged DGF, is an ongoing area of research and inquiry for clinicians and researchers alike to better define, manage, and predict outcomes of this early posttransplant event. This review aims to provide an in-depth, comprehensive summary of the literature to date on the histopathology of DGF and the role of kidney transplant biopsies in prolonged DGF.

Old for young kidney transplantation: a responsible option for our patients to reduce waiting time?

PURPOSE

The Eurotransplant Senior program allocating grafts from donors ≥ 65 years to recipients aged ≥ 65 years has proven good results within the last 20 years. However, "old" grafts are also allocated to younger recipients < 65 years, and this outcome of "old for young" kidney transplantations (KT) still lacks detailed investigations.

METHODS

All "old for young" KT performed at four tertiary referral centers were retrospectively compared including a recent follow-up, stratifying for "old for young" (donor ≥ 65 years to recipient < 65 years) vs. "very old for young" KT (donor ≥ 70 years to recipient < 65 years).

RESULTS

Overall, 99 patients were included with 56 (56.6%) "old for young" and 43 (43.4%) "very old for young" KT. The median waiting time did not differ (60.7 vs. 45.8 months, respectively) at comparable living donation rates (57.1% vs. 44.2%) as well as intra- and postoperative results. At a median follow-up of 44 months (range 1; 133), the 3-year graft survival of 91% vs. 87% did not significantly vary. In subgroup analyses assessing living donation or donation after brain death (DBD) KT only, the graft survival was significantly longer for "old for young" KT within the living donation subgroup. In multivariate Cox regression analyses, the presence of panel-reactive antibodies was the only significant impact factor on graft survival (HR 8.32, p = 0.001).

CONCLUSION

This analysis clearly demonstrates the effectiveness of the "old for young" approach, enabling favorable perioperative results as well as comparable data of graft- and overall survival, while reducing waiting time for eligible patients.

The combinatorial effect of age and biological sex on alloimmunity and transplantation outcome

Both age and biological sex affect transplantation outcomes. We have recently shown in a large volume clinical analysis utilizing the SRTR data that graft survival is inferior in young female kidney transplant recipients. In this multi-factorial analysis, older female recipients presented with a trend towards improved transplant outcomes compared to both young female recipients and male recipients of any age. Those data supported by reports of those of others suggest that sex and age impact alloimmune responses both, individually and synergistically. Biological sex and hormone levels change throughout a lifetime with recognized effects on longevity in addition to an impact on the development and course of several disease preconditions. Detailed mechanisms of those sex and age-specific aspects have thus far been studied outside of transplantation. Effects on alloimmunity are largely unknown. Moreover, the combinatorial impact that both, biological sex and age have on transplant outcomes is not understood. Here, we summarize available data that analyze how age in combination with biological sex may shape alloimmune responses and affect transplant outcomes.

Organ storage in renal transplantation

PURPOSE OF REVIEW

Kidney transplantation is vital for those with end-stage renal disease, enhancing quality of life and longevity. It is the preferred treatment but is hindered by a global disparity between donor kidney availability and demand. Therefore, optimizing organ storage techniques is crucial to mitigate the effects of ischemia reperfusion injury in available organs. Recent interest has centered on innovative methods like oxygenated normothermic perfusion and abdominal regional perfusion.

RECENT FINDINGS

Multiple recent metanalyses, including a Cochrane review, confirm the benefits of hypothermic machine perfusion (HMP) for deceased donor kidneys, demonstrating its utility and cost effectiveness. The benefits of oxygenated normothermic perfusion have been seen in retrospective data sets but not in prospective trials. Abdominal regional perfusion (aNRP) is gaining interest, especially for liver transplantation, but kidney specific data are scant.

SUMMARY

High-quality evidence backs the use of HMP for deceased donor kidneys. Despite interest in other techniques, clinical evidence for their benefits in kidney transplantation is lacking. The gap between innovation and verified success emphasizes the need for continued research and collaboration between medical professionals, researchers, and ethical committees. This review aims to further illuminate the complexities and advancements in the field, bridging the knowledge gap and aiding in the continual pursuit of excellence in transplantation.

Graft survival and postoperative complications following orthotopic renal transplantation

The iliac fossa is the most commonly used site to place the graft in renal transplantation in adults. However, iliac fossa may not be used in various conditions. Thus, orthotopic renal transplantation becomes a viable alternative for these selected patients. Given the technically challenging surgery and limited number of patients, data on the long-term outcomes on this regard are scarce. This narrative review serves as an update on the clinical outcomes after orthotopic renal transplantation, focusing on overall recipient survival and renal graft survival, as well as postoperative complications. We found that studies to date showed a comparable survival rate in both recipients and renal grafts in the postoperative follow-up period after orthotopic renal transplantation with a lower complication rate compared to the published data on heterotopic renal transplantation. The results of our review may encourage transplant centers to reevaluate their policies to consider orthotopic renal transplantation as an alternative technique in cases where heterotopic kidney transplantation is not possible.

Effect of vitamin K on improving post‑kidney transplant outcomes: a meta‑analysis

The effect of vitamin K on clinical outcomes in patients receiving kidney transplantation is contested according to previous studies. This meta-analysis aimed to summarize the impact of vitamin K on all-cause mortality, renal function, inflammation, and vascular/bone health in patients receiving kidney transplantation. EMBASE, PubMed, and Cochrane were searched for literature concerning the effect of vitamin K on clinical outcomes of patients receiving kidney transplantation until December 2022. Normal vitamin K status/vitamin K supplementation was considered as the experimental group; while vitamin K deficiency/no vitamin K supplementation was considered as the control group. All-cause mortality, renal function indexes, C-reactive protein (CRP), and vascular/bone health indexes were extracted and analyzed. A total of seven studies with 1,101 patients in the experimental group and 651 patients in the control group were included. All-cause mortality was decreased in the experimental group vs. the control group [relative risk (95% confidence interval (CI)]: 0.72 (0.60-0.86), P<0.001]. Regarding renal function indexes, the estimated glomerular filtration rate was increased in the experimental group vs. the control group [mean difference (95% CI): 9.87 (1.48-18.26), P=0.021]; while creatinine and albumin remained unchanged between the two groups (both P>0.05). Moreover, CRP, systolic blood pressure, diastolic blood pressure, triglycerides, hemoglobin, calcium, and 25-hydroxyvitamin D were unchanged between the two groups (all P>0.05). Publication bias was low, and the robustness assessed by sensitivity analysis was generally acceptable. Thus vitamin K exerted a potential implication in reducing all-cause mortality and improving renal function in patients receiving kidney transplantation.

Noninvasive measurement of 13Carbon turnover for evaluation of porcine renal grafts during ex vivo machine perfusion

BACKGROUND

Kidney transplantation suffers from a shortage of donor organs. Despite this, a lot of grafts are discarded due to inadequate quality. As many kidneys are afflicted by transient filtration failure early after preservation, classical renal function tests are not applicable to differentiate between prospective recovery or continuing deficit of renal function.

METHODS

Using normothermic machine perfusion as a platform for pre-implantation evaluation of the graft, we present a novel evaluative approach based on the metabolic turnover of 13C-acetate during isolated perfusion. After injection of the tracer, 13CO2 as a metabolic end-product can be quantified by high-precision laser-based spectroscopy in the gas outflow of the oxygenator. Three groups of porcine kidneys with graduated ischemic injury were investigated.

RESULTS

This quantitative approach is able to discriminate acceptable quality kidneys, most likely to recover within days from poor kidney grafts that are unlikely to regain notable glomerular function with high discriminatory power (area under the ROC curve 0.91; P < 0.001 By contrast, conventional renal function tests are rather ineffective under these circumstances.

CONCLUSIONS

This assessment method offers the potential to quantitatively assess donor kidney quality using a measurable output, salvaging donors that would otherwise have been discarded.

Unveiling the Hidden Power of Uromodulin: A Promising Potential Biomarker for Kidney Diseases

Uromodulin, also known as Tamm-Horsfall protein, represents the predominant urinary protein in healthy individuals. Over the years, studies have revealed compelling associations between urinary and serum concentrations of uromodulin and various parameters, encompassing kidney function, graft survival, cardiovascular disease, glucose metabolism, and overall mortality. Consequently, there has been a growing interest in uromodulin as a novel and effective biomarker with potential applications in diverse clinical settings. Reduced urinary uromodulin levels have been linked to an elevated risk of acute kidney injury (AKI) following cardiac surgery. In the context of chronic kidney disease (CKD) of different etiologies, urinary uromodulin levels tend to decrease significantly and are strongly correlated with variations in estimated glomerular filtration rate. The presence of uromodulin in the serum, attributable to basolateral epithelial cell leakage in the thick ascending limb, has been observed. This serum uromodulin level is closely associated with kidney function and histological severity, suggesting its potential as a biomarker capable of reflecting disease severity across a spectrum of kidney disorders. The UMOD gene has emerged as a prominent locus linked to kidney function parameters and CKD risk within the general population. Extensive research in multiple disciplines has underscored the biological significance of the top UMOD gene variants, which have also been associated with hypertension and kidney stones, thus highlighting the diverse and significant impact of uromodulin on kidney-related conditions. UMOD gene mutations are implicated in uromodulin-associated kidney disease, while polymorphisms in the UMOD gene show a significant association with CKD. In conclusion, uromodulin holds great promise as an informative biomarker, providing valuable insights into kidney function and disease progression in various clinical scenarios. The identification of UMOD gene variants further strengthens its relevance as a potential target for better understanding kidney-related pathologies and devising novel therapeutic strategies. Future investigations into the roles of uromodulin and regulatory mechanisms are likely to yield even more profound implications for kidney disease diagnosis, risk assessment, and management.

A Randomized Controlled Trial of Envarsus Versus Immediate Release Tacrolimus in Kidney Transplant Recipients With Delayed Graft Function

BACKGROUND

The incidence of delayed graft function (DGF) among kidney transplant recipients (KTRs) in the United States continues to increase. The effect of immediate-release tacrolimus (tacrolimus) compared with extended-release tacrolimus (Envarsus) among recipients with DGF is unknown.

METHODS

This was a single-center open-label randomized control trial among KTRs with DGF (ClinicalTrials. gov, NCT03864926). KTRs were randomized either to continue on tacrolimus or switch to Envarsus at a 1:1 ratio. Duration of DGF (study period), number of dialysis treatments, and need for adjustment of calcineurin inhibitor (CNI) doses during the study period were outcomes of interest.

RESULTS

A total of 100 KTRs were enrolled, 50 in the Envarsus arm and 50 in the tacrolimus arm; of those, 49 in the Envarsus arm and 48 in the tacrolimus arm were included for analysis. There were no differences in the baseline characteristics, all P > .5, except donors in the Envarsus arm had higher body mass index (mean body mass index 32.9 ± 11.3 vs 29.4 ± 7.6 kg/m2 [P = .007]) compared with the tacrolimus arm. The median duration of DGF (5 days vs 4 days, P = .71) and the number of dialysis treatments (2 vs 2, P = .83) were similar between the groups. However, the median number of CNI dose adjustments during the study period in the Envarsus group was significantly lower (3 vs 4, P = .002).

CONCLUSIONS

Envarsus patients had less fluctuation in the CNI level, requiring fewer CNI dose adjustments. However, there were no differences in the DGF recovery duration or number of dialysis treatments.

Delayed Graft Function Among Kidney Transplant Recipients Is Associated With an Increased Risk of Urinary Tract Infection and BK Viremia

Background

Delayed graft function (DGF) among deceased donor kidney transplant recipients (DDKTRs) is a well-known risk factor for allograft rejection, decreased graft survival, and increased cost. Although DGF is associated with an increased risk of rejection, it is unclear whether it also increases the risk of infection.

Methods

We reviewed all adult DDKTRs at our center between 2010 and 2018. The primary outcomes of interest were BK viremia, cytomegalovirus viremia, pneumonia, and urinary tract infection (UTI) within the first year of transplant. Additional analysis was made with censoring follow-up at the time of allograft rejection.

Results

A total of 1512 DDKTRs were included, of whom 468 (31%) had DGF. As expected, several recipient, donor, and baseline immunological characteristics differed by DGF status. After adjustment, DGF was significantly associated with an increased risk of BK viremia (hazard ratio: 1.34; 95% confidence interval, 1.0-1.81; P = 0.049) and UTI (hazard ratio: 1.70; 95% confidence interval, 1.31-2.19; P < 0.001) but not cytomegalovirus viremia or pneumonia. Associations were similar in models censored at the time of rejection.

Conclusions

DGF is associated with an increased risk of early infectious complications, mainly UTI and BK viremia. Close monitoring and appropriate management are warranted for better outcomes in this unique population.

Longitudinal estimated glomerular filtration rate (eGFR) modeling in long-term renal function to inform clinical trial design in kidney transplantation

Kidney transplantation is the preferred treatment for individuals with end-stage kidney disease. From a modeling perspective, our understanding of kidney function trajectories after transplantation remains limited. Current modeling of kidney function post-transplantation is focused on linear slopes or percent decline and often excludes the highly variable early timepoints post-transplantation, where kidney function recovers and then stabilizes. Using estimated glomerular filtration rate (eGFR), a well-known biomarker of kidney function, from an aggregated dataset of 4904 kidney transplant patients including both observational studies and clinical trials, we developed a longitudinal model of kidney function trajectories from time of transplant to 6 years post-transplant. Our model is a nonlinear, mixed-effects model built in NONMEM that captured both the recovery phase after kidney transplantation, where the graft recovers function, and the long-term phase of stabilization and slow decline. Model fit was assessed using diagnostic plots and individual fits. Model performance, assessed via visual predictive checks, suggests accurate model predictions of eGFR at the median and lower 95% quantiles of eGFR, ranges which are of critical clinical importance for assessing loss of kidney function. Various clinically relevant covariates were also explored and found to improve the model. For example, transplant recipients of deceased donors recover function more slowly after transplantation and calcineurin inhibitor use promotes faster long-term decay. Our work provides a generalizable, nonlinear model of kidney allograft function that will be useful for estimating eGFR up to 6 years post-transplant in various clinically relevant populations.

Neutrophil diversity and plasticity: Implications for organ transplantation

Neutrophils, as the first defenders against external microbes and stimuli, are highly active and finely regulated innate immune cells. Emerging evidence has challenged the conventional dogma that neutrophils are a homogeneous population with a short lifespan that promotes tissue damage. Recent findings on neutrophil diversity and plasticity in homeostatic and disease states have centered on neutrophils in the circulation. In contrast, a comprehensive understanding of tissue-specialized neutrophils in health and disease is still lacking. This article will first discuss how multiomics advances have contributed to our understanding of neutrophil heterogeneity and diversification in resting and pathological settings. This discussion will be followed by a focus on the heterogeneity and role of neutrophils in solid organ transplantation and how neutrophils may contribute to transplant-related complications. The goal of this article is to provide an overview of the research on the involvement of neutrophils in transplantation, with the aim that this may draw attention to an underappreciated area of neutrophil research.

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.

rhMYDGF Alleviates I/R-induced Kidney Injury by Inhibiting Inflammation and Apoptosis via the Akt Pathway

BACKGROUND

Renal ischemia/reperfusion (I/R) injury is one of the crucial factors affecting the outcome of renal transplantation. In recent years, myeloid-derived growth factor (MYDGF) has received a lot of attention for its extensive beneficial effects on cardiac repair and protection of cardiomyocytes from cell death. Therefore, we hypothesized that the recombinant human MYDGF (rhMYDGF) protein might play an essential role in safeguarding renal I/R injury.

METHODS

In vivo experiments were conducted using a mouse unilateral I/R model. Mice were pretreated with rhMYDGF by intraperitoneal injection to study the potential mechanism of renal protection. In vitro, we established hypoxia/reoxygenation and H 2 O 2 treatment models to pretreat cells with rhMYDGF. The expression levels of oxidative stress, inflammation, and apoptosis-related factors in tissues and cells were detected. Finally, we explored the role of the protein kinase B (Akt) pathway in the renal protective mechanism of rhMYDGF.

RESULTS

In this study, we found that intraperitoneal injection of 1.25 μg rhMYDGF could significantly improve renal function of I/R mice, and reduce oxidative stress, inflammation, and apoptosis. For the human proximal tubular epithelial cell line and human kidney cell line, pretreatment with 0.3 μg/mL rhMYDGF for 24 h significantly downregulated oxidative stress, inflammation, and apoptosis via the phosphorylation of Akt, which could be ameliorated by LY294002.

CONCLUSIONS

rhMYDGF protects kidney from I/R injury by attenuating oxidative stress, inflammation, and apoptosis through the activation of the Akt pathway.

Empagliflozin improves renal ischemia-reperfusion injury by reducing inflammation and enhancing mitochondrial fusion through AMPK-OPA1 pathway promotion

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is one reason for renal transplantation failure. Recent studies have shown that mitochondrial dynamics is closely related to IRI, and that inhibition or reversal of mitochondrial division protects organs against IRI. Optic atrophy protein 1 (OPA1), an important factor in mitochondrial fusion, has been shown to be upregulated by sodium-glucose cotransporter 2 inhibitor (SGLT2i). Also, the antiinflammatory effects of SGLT2i have been demonstrated in renal cells. Thus, we hypothesized that empagliflozin could prevent IRI through inhibiting mitochondrial division and reducing inflammation.

METHODS

Using hematoxylin-eosin staining, enzyme linked immunosorbent assay (ELISA), flow cytometry, immunofluorescent staining, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) staining, real-time PCR, RNA-sequencing, and western blot, we analyzed renal tubular tissue from in vivo and in vitro experiments.

RESULTS

Through animal experiments and sequencing analysis, we first confirmed the protection against IRI and the regulation of mitochondrial dynamics-related factors and inflammatory factors by empagliflozin pretreatment. Then, through hypoxia/reoxygenation (H/R) cellular experiments, we confirmed that empagliflozin could inhibit mitochondrial shortening and division and upregulate OPA1 in human renal tubular epithelial cell line (HK-2) cells. Subsequently, we knocked down OPA1, and mitochondrial division and shortening were observed, which could be alleviated by empagliflozin treatment. Combined with the previous results, we concluded that OPA1 downregulation leads to mitochondrial division and shortening, and empagliflozin can alleviate the condition by upregulating OPA1. We further explored the pathway through which empagliflozin functions. Related studies have shown the activation of AMPK pathway by empagliflozin and the close correlation between the AMPK pathway and OPA1. In our study, we blocked the AMPK pathway, and OPA1 upregulation by empagliflozin was not observed, thus demonstrating the dependence of empagliflozin on the AMPK pathway.

CONCLUSION

The results indicated that empagliflozin could prevent or alleviate renal IRI through antiinflammatory effects and the AMPK-OPA1 pathway. Ischemia-reperfusion injury is an inevitable challenge in organ transplantation. It is necessary to develop a new therapeutic strategy for IRI prevention in addition to refining the transplantation process. In this study, we confirmed the preventive and protective effects of empagliflozin in renal ischemia-reperfusion injury. Based on these findings, empagliflozin is promising to be a preventive agent for renal ischemia-reperfusion injury and can be applied for preemptive administration in kidney transplantation.

Delayed graft function: current status and future directions

PURPOSE OF REVIEW

Delayed graft function is a common early posttransplant event predictive of adverse outcomes including hospital readmission, impaired long-term graft function, and decreased graft and patient survival. The purpose of this review is to summarize recent literature describing delayed graft function in hopes of better understanding and managing this condition.

RECENT FINDINGS

Recent research efforts have been garnered towards risk factor modification, prevention, and earlier detection of delayed graft function. In this review, we aim to summarize current innovative approaches and future directions.

SUMMARY

Delayed graft function portends worse graft and patient outcomes. Continued research to prevent, and detect early perturbations in allograft function, and more optimally manage this disease will hopefully improve graft function, along with graft/patient survival.

Extracellular histone release by renal cells after warm and cold ischemic kidney injury: Studies in an ex-vivo porcine kidney perfusion model

Extracellular histones are cytotoxic molecules involved in experimental acute kidney injury. In patients receiving a renal transplant from donors after circulatory death, who suffer from additional warm ischemia, worse graft outcome is associated with higher machine perfusate extracellular histone H3 concentrations. We now investigated temperature-dependent extracellular histone release in an ex vivo porcine renal perfusion model, and subsequently studied histone release in the absence and presence of non-anticoagulant heparin. Seven pairs of ischemically damaged porcine kidneys were machine perfused at 4°C (cold ischemia) or 28°C (warm ischemia). Perfusate histone H3 concentration was higher after warm as compared to cold ischemia (median (IQR) = 0.48 (0.20-0.83) μg/mL vs. 0.02 (0.00-0.06) μg/mL; p = .045, respectively). Employing immune-electron microscopy (EM), histone containing cytoplasmic protrusions of tubular and endothelial cells were found after warm ischemic injury. Furthermore, abundant histone localization was detected in debris surrounding severely damaged glomerular cells, in a "buck shot" pattern. In vitro, histones were cytotoxic to endothelial and kidney epithelial cells in a temperature-dependent manner. In a separate ex vivo experiment, addition of heparin did not change the total histone H3 levels observed in the perfusate but revealed a continuous increase in the level of a lower molecular weight histone H3 variant. Our findings show that ischemically damaged kidneys release more extracellular histones in warm ischemia, which by EM was due to histone release by renal cells. Blocking of histone-mediated damage during transplantation may be beneficial in prevention of renal injury.

Renal transplant anastomotic time-Every minute counts!

The impact of anastomotic time in renal transplant is under recognized and not well studied. It is one of the few controllable factors that affect the incidence of delayed graft function (DGF). Our study aimed at quantifying the impact of anastomotic time. We performed a retrospective review of 424 renal transplants between the years 2006 and 2020. A total of 247 deceased donor renal transplants formed the study cohort. Patients were divided into two groups based on the presence or absence of DGF. Variables with p < 0.3 were analyzed using the binary logistic regression test. The final analysis showed anastomotic time to be significantly associated with DGF with odds ratio of 1.04 per minute corresponding to 4% increase in DGF incidence with every minute increment in anastomotic time. Other variables that had significant impact on DGF were DCD donor (odds ratio - 8.7) and donor terminal creatinine. We concluded that anastomotic time had significant impact on the development of DGF and hence should be minimized.

Contrast-Enhanced Ultrasonography Value for Early Prediction of Delayed Graft Function in Renal Transplantation Patients

OBJECTIVES

Delayed graft function (DGF) is a common early complication after kidney transplantation. The aim of the present study was to evaluate the value of contrast-enhanced ultrasonography (CEUS) in the early prediction of DGF after kidney transplantation.

METHODS

A total of 89 renal transplant recipients were retrospectively enrolled and divided into DGF group or normal graft function (NGF) group according to the allograft function. Conventional Doppler ultrasound and CEUS examination data on the first postoperative day were collected and analyzed.

RESULTS

The resistive indices of segmental and interlobar artery in the DGF group were significantly higher than those in the NGF group (0.71 ± 0.17 versus 0.63 ± 0.08, P = .006; 0.70 ± 0.16 versus 0.62 ± 0.08, P = .004, respectively). The patients experiencing DGF had significantly lower PI-c (14.7 dB ± 6.1 dB versus 18.5 dB ± 3.3 dB, P = .001) and smaller AUC-c (779.8 ± 375.8 dB·seconds versus 991.0 ± 211.7 dB·seconds, P = .003), as well as significantly lower PI-m (12.6 dB ± 5.9 dB versus 15.9 dB ± 3.9 dB, P = .006), shorter MTT-m (30.7 ± 9.4 seconds versus 36.3 ± 7.1 seconds, P = .01), and smaller AUC-m (P = .007). Multivariate analysis demonstrated that PI-c, AUC-c, and MTT-m were independent risk factors for DGF. The area under the receiver operating characteristic curve values of the combined predicted value (PI-c + MTT-m, PI-c + AUC-c + MTT-m) of DGF incidence were bigger than that of PI-c, AUC-c, or MTT-m.

CONCLUSIONS

CEUS parameters of the cortex and medulla have a good value for an early prediction of DGF after renal transplantation.

Identification of renal ischemia reperfusion injury subtypes and predictive strategies for delayed graft function and graft survival based on neutrophil extracellular trap-related genes

Background

Ischemia reperfusion injury (IRI) is an inevitable process in renal transplantation, which is closely related to serious postoperative complications such as delayed graft function (DGF), acute rejection and graft failure. Neutrophil extracellular traps (NETs) are extracellular DNA structures decorated with various protein substances released by neutrophils under strong signal stimulation. Recently, NETs have been found to play an important role in the process of IRI. This study aimed to comprehensively analyze the expression landscape of NET-related genes (NRGs) during IRI, identify clusters with different degrees of IRI and construct robust DGF and long-term graft survival predictive strategies.

Methods

The microarray and RNA-seq datasets were obtained from the GEO database. Differentially expressed NRGs (DE-NRGs) were identified by the differential expression analysis, and the NMF algorithm was used to conduct a cluster analysis of IRI samples. Machine learning algorithms were performed to screen DGF-related hub NRGs, and DGF and long-term graft survival predictive strategies were constructed based on these hub NRGs. Finally, we verified the expression of Cxcl1 and its effect on IRI and NETs generation in the mouse IRI model.

Results

This study revealed two IRI clusters (C1 and C2 clusters) with different molecular features and clinical characteristics. Cluster C1 was characterized by active metabolism, mild inflammation and lower incidence of DGF, while Cluster C2 was inflammation activated subtype with a higher incidence of DGF. Besides, based on DGF-related hub NRGs, we successfully constructed robust DGF and long-term graft survival predictive strategies. The mouse renal IRI model verified that Cxcl1 was significantly upregulated in renal tissues after IRI, and using a CXCL8/CXCL1 inhibitor could significantly improve renal function, alleviate renal tubular necrosis, tissue inflammatory response, and NET formation.

Conclusion

This study identified two distinct IRI clusters based on DE-NRGs and constructed robust prediction methods for DGF and graft survival, which can provide references for early prevention and individualized treatment of various postoperative complications after renal transplantation.

Risk factors of tigecycline-associated fibrinogen reduction in patients with renal transplantation: a case-control study

BACKGROUND

Hypofibrinogenemia is a serious adverse reaction related to tigecycline administered against multidrug-resistant (MDR) bacteria and can lead to therapy termination. High dose and prolonged tigecycline therapy, renal failure, and base level of fibrinogen (FIB) were reported risk factors of tigecycline-associated FIB reduction. But results are unknown in patients with renal transplantation.

METHODS

A single-center and a case-control study involving renal transplantation patients was conducted. From January, 2017 to January, 2020, patients with a tigecycline course more than 2 days and a baseline FIB level greater than 2 g/L were enrolled. Hypofibrinogenemia was defined as plasma FIB <2.0 g/L. The extent of FIB reduction was calculated based on the baseline of FIB level before tigecycline administration. FIBRO was defined as the extent of FIB reduction over 50%, and FIBRB referred to the extent of FIB reduction below 50%. Univariate and multivariate analyses were performed by logistic regression models to identify independent risk factors of tigecycline-associated FIB reduction.

RESULTS

In total, 120 patients were enrolled. A total of 114 patients (95.00%) developed with hypofibrinogenaemia. Hypofibrinogenemia mainly occurred 3 days after tigecycline administration. Of them, 79 (65.83%) developed FIBRO with a median occurrence of 3 [2-4] days after initiation of tigecycline. Multivariable regression analysis demonstrated that the FIB level before tigecycline use [odds ratio (OR): 3.225, 95% confidence interval (CI): 1.801-5.772] and total tigecycline dose (OR: 4.930, 95% CI: 1.433-16.959) were risk factors for FIBRO.

CONCLUSIONS

The FIB level before tigecycline use and total tigecycline dose were significantly associated with FIBRO, suggesting that FIB level and coagulation-related indicators should be closely monitored during tigecycline treatment to avoid life-threatening bleeding events.

Delayed Graft Function in Kidney Transplant: Risk Factors, Consequences and Prevention Strategies

Background. Delayed graft function is a frequent complication of kidney transplantation that requires dialysis in the first week posttransplant. Materials and Methods. We searched for the most relevant articles in the National Institutes of Health library of medicine, as well as in transplantation, pharmacologic, and nephrological journals. Results. The main factors that may influence the development of delayed graft function (DGF) are ischemia–reperfusion injury, the source and the quality of the donated kidney, and the clinical management of the recipient. The pathophysiology of ischemia–reperfusion injury is complex and involves kidney hypoxia related to the duration of warm and cold ischemia, as well as the harmful effects of blood reperfusion on tubular epithelial cells and endothelial cells. Ischemia–reperfusion injury is more frequent and severe in kidneys from deceased donors than in those from living donors. Of great importance is the quality and function of the donated kidney. Kidneys from living donors and those with normal function can provide better results. In the peri-operative management of the recipient, great attention should be paid to hemodynamic stability and blood pressure; nephrotoxic medicaments should be avoided. Over time, patients with DGF may present lower graft function and survival compared to transplant recipients without DGF. Maladaptation repair, mitochondrial dysfunction, and acute rejection may explain the worse long-term outcome in patients with DGF. Many different strategies meant to prevent DGF have been evaluated, but only prolonged perfusion of dopamine and hypothermic machine perfusion have proven to be of some benefit. Whenever possible, a preemptive transplant from living donor should be preferred.

Tacrolimus Concentration Is Effectively Predicted Using Combined Clinical and Genetic Factors in the Perioperative Period of Kidney Transplantation and Associated with Acute Rejection

Background

Tacrolimus has unpredictable pharmacokinetic (PK) characteristics, which are partially attributed to CYP3A5 polymorphism. The potential effects of clinical factors in the postoperative period of transplantation on tacrolimus PK and those of early tacrolimus PK variability on clinical outcomes are yet to be clarified.

Methods

We examined the genetic and clinical factors affecting early tacrolimus PK variability in 256 kidney transplant recipients. The relationships among tacrolimus exposure, graft function delay (DGF), and acute rejection (AR) were further explored. Findings. The CYP3A5 genotype were strongly associated with tacrolimus concentration/dose ratio (C₀/D). Additionally, ABCB1 (rs1045642 and rs2032582) and ABCC2 (rs3740066) were found to have potential independent effects on early tacrolimus C₀/D in multivariate analysis. Red blood counts and albumin level were the most significant clinical factors associated with tacrolimus C₀/D. Wuzhi capsule also exerted an effect on tacrolimus PK. A model combined with pharmacogenetic and clinical factors explained 43.4% tacrolimus PK variability compared with 16.3% on the basis of CYP3A5 genotype only. Notably, increasing tacrolimus concentrations in the early postoperative stage were associated with AR, but not DGF.

Conclusions

Combined analysis of genotype and specific clinical factors is important for the formulation of precise tacrolimus dose regimens in the early stage after kidney transplantation.

Prediction model of delayed graft function based on clinical characteristics combined with serum IL-2 levels

BACKGROUND

Kidney transplantation is an effective treatment for end-stage renal disease (ESRD). Delayed graft function (DGF) is a common complication after kidney transplantation and exerts substantial effects on graft function and long-term graft survival. Therefore, the construction of an effective model to predict the occurrence of DGF is particularly important.

METHODS

Seventy-one patients receiving their first kidney transplant at the First Affiliated Hospital of Nanchang University from October 2020 to October 2021 were enrolled in the discovery cohort. Based on clinical characteristics and serum markers, a logistic regression model was used to simulate the risk of DGF in the discovery cohort. The DGF prediction model was named the prediction system and was composed of risk factors related to DGF. Thirty-two patients receiving a kidney transplant at the First Affiliated Hospital of Nanchang University from October 2021 to February 2022 were enrolled in the validation cohort. The validation cohort was used to verify the accuracy and reliability of the prediction model.

RESULTS

Cold ischemia time (CIT), donor history of diabetes mellitus, donor interleukin-2 (IL-2) level and donor terminal creatinine level constitute the prediction system. In the validation test, the area under the receiver operating characteristic curve (AUC) was 0.867 for the prediction system, and good calibration of the model was confirmed in the validation cohort.

CONCLUSIONS

This study constructed a reliable and highly accurate prediction model that provides a practical tool for predicting DGF. Additionally, IL-2 participates in the kidney injury process and may be a potential marker of kidney injury.

Postoperative day 1 serum cystatin C level predicts postoperative delayed graft function after kidney transplantation

Background

Delayed graft function (DGF) commonly occurs after kidney transplantation, but no clinical predictors for guiding post-transplant management are available.

Materials and methods

Data including demographics, surgery, anesthesia, postoperative day 1 serum cystatin C (S-CysC) level, kidney functions, and postoperative complications in 603 kidney transplant recipients who met the enrollment criteria from January 2017 to December 2018 were collected and analyzed to form the Intention-To-Treat (ITT) set. All perioperative data were screened using the least absolute shrinkage and selection operator. The discrimination, calibration, and clinical effectiveness of the predictor were verified with area under curve (AUC), calibration plot, clinical decision curve, and impact curve. The predictor was trained in Per-Protocol set, validated in the ITT set, and its stability was further tested in the bootstrap resample data.

Result

Patients with DGF had significantly higher postoperative day 1 S-CysC level (4.2 ± 1.2 vs. 2.8 ± 0.9 mg/L; P < 0.001), serum creatinine level (821.1 ± 301.7 vs. 554.3 ± 223.2 μmol/L; P < 0.001) and dialysis postoperative (74 [82.2%] vs. 25 [5.9%]; P < 0.001) compared with patients without DGF. Among 41 potential predictors, S-CysC was the most effective in the parsimonious model, and its diagnostic cut-off value was 3.80 mg/L with the risk score (OR, 13.45; 95% CI, 8.02–22.57; P < 0.001). Its specificity and sensitivity indicated by AUC was 0.832 (95% CI, 0.779–0.884; P < 0.001) with well fit calibration. S-CysC yielded up to 50% of clinical benefit rate with 1:4 of cost/benefit ratio.

Conclusion

The postoperative day 1 S-CysC level predicts DGF and may be used as a predictor of DGF but warrants further study.

In kidney recipients from the same deceased donor, discordance in delayed graft function is associated with the worst outcomes

Delayed graft function(DGF) is a common complication among deceased donor kidney transplant recipients(DDKTs) and is associated with worse outcomes. The effect on outcomes of concordance versus discordance in DGF between two different recipients of kidneys from the same donor is largely unknown. We reviewed all adult DDKTs for which both kidneys were transplanted to two different recipients at our center between 2014-2019. DDKTs were divided into four groups based on the DGF status: concordance no DGF(cc-no-DGF); discordance no DGF(dd-no-DGF); discordance DGF(dd-DGF) and concordance in DGF(cc-DGF). Acute rejection (AR) and death censored graft failure (DCGF) were outcomes of interest. A total of 578 DDKTs fulfilled our selection criteria, 280 were in cc-no-DGF, 83 in dd-no-DGF, 83 in dd-DGF, and 132 in cc-DGF. Compared to cc-no-DGF, in univariate analysis, dd-DGF was associated with an increased risk of AR(HR:1.60; 95% CI:1.0-2.56) but cc-DGF was not(HR:1.01; 95% CI:0.63-1.62). dd-DGF was not associated with an increased risk of AR in multivariate analysis. In multivariate analysis, dd-DGF was associated with an increased risk of DCGF (HR: 2.70; 95% CI: 1.05-6.93) but cc-DGF was not (HR:2.36; 95% CI:0.97-5.70). Discordance in DGF is associated with worse outcomes and may need close follow-up and monitoring to improve the outcomes. This article is protected by copyright. All rights reserved.

GATA1 regulates the microRNA‑328‑3p/PIM1 axis via circular RNA ITGB1 to promote renal ischemia/reperfusion injury in HK‑2 cells

Acute kidney injury (AKI) is caused by renal ischemia/reperfusion injury (IRI) during kidney transplantation. The levels of both circular RNAs (circRNAs) and microRNAs (miRNAs/miR) appear to be critical for AKI detection. While several RNA interactions in AKI have been found, the regulatory mechanisms between the molecules remain to be fully elucidated. In the present study, miRNA expression profiling analysis was conducted using an online dataset to identify the differentially expressed miRNAs in rats with IRI. miR-328-3p was also found to be downregulated in human kidney-2 (HK-2) cells subjected to hypoxia/reperfusion (H/R), and its overexpression targeting pim-1 proto-oncogene (PIM1) resulted in an increased viability and a reduced apoptosis, as well as in the decreased expression of inflammatory factors upon H/R exposure. Putative targets and circRNAs of miR-328-3p were identified using publically available databases. The inhibition of circRNA integrin beta 1 (ITGB1; circITGB1) suppressed the inflammatory response induced by H/R by sponging miR-328-3p in HK-2 cells. Furthermore, a sequence of the functional ITGB1 promoter was studied for transcription factor GATA binding protein 1 (GATA1) binding sites. GATA1 binds to the ITGB1 promoter, leading to the expression of circITGB1. On the whole, the findings of the present study revealed a regulatory pathway modulating miR-328-3p in IRI, demonstrating that the GATA1-mediated regulation of circITGB1 enhanced the H/R-induced inflammatory response via the miR-328-3p/PIM1 axis.

The Selective Estrogen Receptor Modulator, Raloxifene, Is Protective Against Renal Ischemia-Reperfusion Injury

BACKGROUND

There is increasing evidence that estrogen is responsible for improved outcomes in female kidney transplant recipients. Although the exact mechanism is not yet known, estrogen appears to exert its protective effects by ameliorating ischemia-reperfusion injury (IRI). In this study, we have examined whether the beneficial effects of exogenous estrogen in renal IRI are replicated by therapy with any one of several selective estrogen receptor modulators.

METHODS

C57BL/6 adult mice underwent standardized warm renal ischemia for 28 min after being injected with the selective estrogen receptor modulators, raloxifene, lasofoxifene, tamoxifen, bazedoxifene, or control vehicle (dimethyl sulfoxide), at 16 and 1 h before IRI. Plasma concentrations of blood urea nitrogen and creatinine were assessed 24, 48, 72, and 96 h post-IRI. Tissue was collected 30 d postischemia for fibrosis analysis using Sirius Red staining.

RESULTS

Raloxifene treatment in female mice resulted in significantly lower blood urea nitrogen and creatinine after IRI and significantly lower fibrosis 30 d following IRI.

CONCLUSIONS

Raloxifene is protective against both acute kidney injury and fibrosis resulting from renal IRI in a mouse model.

Identification of Multiple Hub Genes in Acute Kidney Injury after Kidney Transplantation by Bioinformatics Analysis

Background and Objectives: The molecular mechanisms of the development of acute kidney injury (AKI) after kidney transplantation are not yet clear. The aim of this study was to confirm the genes and mechanisms related to AKI after transplantation. Materials and Methods: To investigate potential genetic targets for AKI, an analysis of the gene expression omnibus database was used to identify key genes and pathways. After identification of differentially expressed genes, Kyoto Encyclopedia of Genes and Genome pathway enrichment analyses were performed. We identified the hub genes and established the protein–protein interaction network. Results: Finally, we identified 137 differentially expressed genes (59 upregulated genes and 16 downregulated genes). AKAP12, AMOT, C3AR1, LY96, PIK3AP1, PLCD4, PLCG2, TENM2, TLR2, and TSPAN5 were filtrated by the hub genes related to the development of post-transplant AKI from the Protein–Protein Interaction (PPI) network. Conclusions: This may provide important evidence of the diagnostic and therapeutic biomarker of AKI.

The Role of Peritoneal Dialysis in Different Phases of Kidney Transplantation

The utilization of peritoneal dialysis (PD) has been increasing in the past decade owing to various government initiatives and recognition of benefits such as better preservation of residual renal function, quality of life, and lower cost. The Advancing American Kidney Health initiative aims to increase the utilization of home therapies such as PD and kidney transplantation to treat end stage kidney disease (ESKD). A natural consequence of this development is that more patients will receive PD, and many will eventually undergo kidney transplantation. Therefore, it is important to understand the effect of pretransplant PD on posttransplant outcomes such as delayed graft function (DGF), rejection, thrombosis, graft, and patient survival. Furthermore, some of these patients may develop DGF, which raises the question of the utility of PD during DGF and its risks. Although transplant is the best renal replacement therapy option, it is not everlasting, and many transplant recipients must go on dialysis after allograft failure. Can PD be a good option for these patients? This is another critical question. Furthermore, a significant proportion of nonrenal solid organ transplant recipients develop ESKD. Is PD feasible in this group? In this review, we try to address all of these questions in the light of available evidence.

Impact of targeted hypothermia in expanded-criteria organ donors on recipient kidney-graft function: study protocol for a multicentre randomised controlled trial (HYPOREME)

INTRODUCTION

Expanded-criteria donors (ECDs) are used to reduce the shortage of kidneys for transplantation. However, kidneys from ECDs are associated with an increased risk of delayed graft function (DGF), a risk factor for allograft loss and mortality. HYPOREME will be a multicentre randomised controlled trial (RCT) comparing targeted hypothermia to normothermia in ECDs, in a country where the use of machine perfusion for organ storage is the standard of care. We hypothesise that hypothermia will decrease the incidence of DGF.

METHODS AND ANALYSIS

HYPOREME is a multicentre RCT comparing the effect on kidney function in recipients of targeted hypothermia (34°C-35°C) and normothermia (36.5°C-37.5°C) in the ECDs. The temperature intervention starts from randomisation and is maintained until aortic clamping in the operating room. We aim to enrol 289 ECDs in order to analyse the kidney function of 516 recipients in the 53 participating centres. The primary outcome is the occurrence of DGF in kidney recipients, defined as a requirement for renal replacement therapy within 7 days after transplantation (not counting a single session for hyperkalemia during the first 24 hours). Secondary outcomes include the proportion of patients with individual organs transplanted in each group; the number of organs transplanted from each ECD and the vital status and kidney function of the recipients 7 days, 28 days, 3 months and 1 year after transplantation. An interim analysis is planned after the enrolment of 258 kidney recipients.

ETHICS AND DISSEMINATION

The trial was approved by the ethics committee of the French Intensive Care Society (CE-SRLF-16-07) on 26 April 2016 and by the competent French authorities on 20 April 2016 (Comité de Protection des Personnes-TOURS-Région Centre-Ouest 1, registration #2016-S3). Findings will be published in peer-reviewed journals and presented during national and international scientific meetings.

TRIAL REGISTRATION NUMBER

NCT03098706.

Necroptosis in Solid Organ Transplantation: A Literature Overview

Ischemia-reperfusion injury (IRI) is encountered in various stages during solid organ transplantation (SOT). IRI is known to be a multifactorial inflammatory condition involving hypoxia, metabolic stress, leukocyte extravasation, cellular death (including apoptosis, necrosis and necroptosis) and an activation of immune response. Although the cycle of sterile inflammation during IRI is consistent among different organs, the underlying mechanisms are poorly understood. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be crucial in the implementation of necroptosis. Moreover, apart from “silent” apoptotic death, necrosis also causes sterile inflammation—necroinflammation, which is triggered by various damage-associated molecular patterns (DAMPs). Those DAMPs activate the innate immune system, causing local and systemic inflammatory responses, which can result in graft failure. In this overview we summarize knowledge on mechanisms of sterile inflammation processes during SOT with special focus on necroptosis and IRI and discuss protective strategies.

BMAL1 regulates mitochondrial homeostasis in renal ischaemia-reperfusion injury by mediating the SIRT1/PGC-1α axis

The regulation of renal function by circadian gene BMAL1 has been recently recognized; however, the role and mechanism of BMAL1 in renal ischaemia‐reperfusion injury (IRI) are still unknown. The purpose of this study was to clarify the pathophysiological role of BMAL1 in renal IRI. We measured the levels of BMAL1 and mitochondrial biogenesis‐related proteins, including SIRT1, PGC‐1α, NRF1 and TFAM, in rats with renal IRI. In rats, the level of BMAL1 decreased significantly, resulting in inhibition of SIRT1 expression and mitochondrial biogenesis. In addition, under hypoxia and reoxygenation (H/R) stimulation, BMAL1 knockdown decreased the level of SIRT1 and exacerbated the degree of mitochondrial damage and apoptosis. Overexpression of BMAL1 alleviated H/R‐induced injury. Furthermore, application of the SIRT1 inhibitor EX527 not only reduced the activities of SIRT1 and PGC‐1α but also further aggravated mitochondrial dysfunction and partially reversed the protective effect of BMAL1 overexpression. Moreover, whether in vivo or in vitro, the application of SIRT1 agonist resveratrol rescued the mitochondrial dysfunction caused by H/R or IRI by activating mitochondrial biogenesis. These results indicate that BMAL1 is a key circadian gene that mediates mitochondrial homeostasis in renal IRI through the SIRT1/PGC‐1α axis, which provides a new direction for targeted therapy for renal IRI.

Peritoneal Dialysis for Potential Kidney Transplant Recipients: Pride or Prejudice?

Kidney transplantation (KT) is recognized as the gold-standard of treatment for patients with end-stage renal disease. Additionally, it has been demonstrated that receiving a pre-emptive KT ensures the best recipient and graft survivals. However, due to an overwhelming discrepancy between the organs available and the patients on the transplant waiting list, the vast majority of transplant candidates require prolonged periods of dialysis before being transplanted. For many years, peritoneal dialysis (PD) and hemodialysis (HD) have been considered competitive renal replacement therapies (RRT). This dualistic vision has recently been questioned by evidence suggesting that an individualized and flexible approach may be more appropriate. In fact, tailored and cleverly planned changes between different RRT modalities, according to the patient’s needs and characteristics, are often needed in order to achieve the best results. While home HD is still under scrutiny in this particular setting, current data seems to favor the use of PD over in-center HD in patients awaiting a KT. In this specific population, the demonstrated advantages of PD are superior quality of life, longer preservation of residual renal function, lower incidence of delayed graft function, better recipient survival, and reduced cost.

Protective effect of estradiol copreservation against kidney ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is the major cause of delayed graft function (DGF) during the posttransplantation period. Estradiol (E2) prevents IRI-induced kidney dysfunction and tissue injury. However, many side effects limit E2's in vivo application. Recent evidence uncovers E2's expanded use in the field of transplantation. We aimed to study if and how E2 exerts protective activity during the period of kidney organ preservation. The autologous kidney transplant model in rats was first established. Rats were divided into 5 groups: normal group (N), sham group (sham), static cold storage (SCS) 4 hours group (control), SCS 4 hours + ethanol (1 µL/mL) group (solvent), and SCS 4 hours + ethanol (1 µL/mL) + E2 (1000 ng/mL) group (E2). ERα expression under hypothermia was measured by western blotting. Moreover, biochemical analyses of plasma levels of creatinine, BUN, estradiol, and testosterone were examined. Among all groups, kidney tissues were collected and processed for further western blot analysis about ERα, eNOS, Bcl-2, and Bax expression, histological analyses such as H&E staining to evaluate pathological severity. In addition, a TUNEL assay is performed to evaluate apoptosis. E2 copreservation upregulated ERα expression under hypothermia. Moreover, E2 copreservation reduced levels of creatinine and BUN in plasma but without affecting estradiol and testosterone. Further, E2 copreservation increased expression of eNOS and antiapoptotic Bcl-2 and decreases expression of proapoptotic Bax. E2 copreservation significantly inhibited IRI-induced apoptosis and evidently improved pathological severity in the kidney of rats. E2 copreservation exerts protective activity against IRI-induced pro-inflammatory and proapoptotic effects in kidneys during organ preservation time and improves transplanted kidney function.

The value of cystatin C in predicting perioperative and long-term prognosis of renal transplantation

This study aimed to evaluate the value of cystatin C (Cys C) in predicting the perioperative and long-term prognosis of renal transplantation (RT). The clinical data of 198 RT recipients were collected. Blood samples were obtained daily until 7 d after transplantation and then discharge day to determine the serum levels of Cys C. The receiver-operating characteristic (ROC) analysis and the area under the curve (AUC) were used to determine the diagnostic accuracy of Cys C for delayed graft function (DGF). The presence of shrunken pore syndrome (SPS) with a cystatin C-based estimate of glomerular filtration rate less than 70% of a creatinine-based estimate, was also evaluated as a prognostic factor for the development of DGF. The serum Cys C levels of patients with DGF were higher than those of the non-DGF group. Cys C showed a higher AUC (0.928) in the ROC analysis than did sCr (0.862). Compared to the non-SPS group, there were more patients diagnosed with SPS in the DGF group (p < .05). The follow-up data showed that patients diagnosed with SPS had higher levels of sCr and Cys C compared to other patients, suggesting a poor long-term prognosis. Our findings suggest that Cys C is a sensitive indicator of renal function during the perioperative period. Cys C at a concentration of 4.9 mg/L had the highest sum of sensitivity and specificity for prediction of DGF, with a sensitivity of 0.889 and a specificity of 0.8. SPS is associated with the development of DGF and the poor long-term prognosis of RT.