Summary of FDA workshop on ischemia reperfusion injury in kidney transplantation

Lymphocytes and innate immune cells in acute kidney injury and repair

Acute kidney injury (AKI) is a common and serious disease entity that affects native kidneys and allografts but for which no specific treatments exist. Complex intrarenal inflammatory processes driven by lymphocytes and innate immune cells have key roles in the development and progression of AKI. Many studies have focused on prevention of early injury in AKI. However, most patients with AKI present after injury is already established. Increasing research is therefore focusing on mechanisms of renal repair following AKI and prevention of progression from AKI to chronic kidney disease. CD4+ and CD8+ T cells, B cells and neutrophils are probably involved in the development and progression of AKI, whereas regulatory T cells, double-negative T cells and type 2 innate lymphoid cells have protective roles. Several immune cells, such as macrophages and natural killer T cells, can have both deleterious and protective effects, depending on their subtype and/or the stage of AKI. The immune system not only participates in injury and repair processes during AKI but also has a role in mediating AKI-induced distant organ dysfunction. Targeted manipulation of immune cells is a promising therapeutic strategy to improve AKI outcomes.

Mineralocorticoid receptor antagonists in kidney transplantation

BACKGROUND

The fundamental role of the renin-angiotensin-aldosterone system in the pathophysiology of chronic kidney disease, congestive heart failure, hypertension and proteinuria is well established in pre-clinical and clinical studies. Mineralocorticoid receptor antagonists are among the primary options for renin-angiotensin-aldosterone system blockage, along with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

METHODS

In this narrative review, we aim to evaluate the efficiency and safety of mineralocorticoid receptor antagonists in kidney transplant recipients, including the potential underlying pathophysiology.

RESULTS

The efficiency and safety of mineralocorticoid receptor antagonists in managing chronic kidney disease and proteinuria, either non-nephrotic or nephrotic range, have been demonstrated among nontransplanted patients, though studies investigating the role of mineralocorticoid receptor antagonists among kidney transplant recipients are scarce. Nevertheless, promising results have been reported in pre-clinical and clinical studies among kidney transplant recipients regarding the role of mineralocorticoid receptor antagonists in terms of ischaemia-reperfusion injury, proteinuria, or calcineurin inhibitor-mediated nephrotoxicity without considerable adverse events such as hypotension, hyperkalaemia or worsening renal functions.

CONCLUSION

Even though initial results regarding the role of mineralocorticoid receptor antagonist therapy for kidney transplant recipients are promising, there is clear need for large-scale randomized clinical trials with long-term follow-up data.

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.

Remote ischemic conditioning may improve graft function following kidney transplantation: a systematic review and meta-analysis with trial sequential analysis

BACKGROUND

Remote ischemic conditioning (RIC) has the potential to benefit graft function following kidney transplantation by reducing ischemia-reperfusion injury; however, the current clinical evidence is inconclusive. This meta-analysis with trial sequential analysis (TSA) aimed to determine whether RIC improves graft function after kidney transplantation.

METHODS

A comprehensive search was conducted on PubMed, Cochrane Library, and EMBASE databases until June 20, 2023, to identify all randomized controlled trials that examined the impact of RIC on graft function after kidney transplantation. The primary outcome was the incidence of delayed graft function (DGF) post-kidney transplantation. The secondary outcomes included the incidence of acute rejection, graft loss, 3- and 12-month estimated glomerular filtration rates (eGFR), and the length of hospital stay. Subgroup analyses were conducted based on RIC procedures (preconditioning, perconditioning, or postconditioning), implementation sites (upper or lower extremity), and graft source (living or deceased donor).

RESULTS

Our meta-analysis included eight trials involving 1038 patients. Compared with the control, RIC did not significantly reduce the incidence of DGF (8.8% vs. 15.3%; risk ratio = 0.76, 95% confidence interval [CI], 0.48-1.21, P = 0.25, I2 = 16%), and TSA results showed that the required information size was not reached. However, the RIC group had a significantly increased eGFR at 3 months after transplantation (mean difference = 2.74 ml/min/1.73 m2, 95% CI: 1.44-4.05 ml/min/1.73 m2, P < 0.0001, I2 = 0%), with a sufficient evidence suggested by TSA. The secondary outcomes were comparable between the other secondary outcomes. The treatment effect of RIC did not differ between the subgroup analyses.

CONCLUSION

In this meta-analysis with trial sequential analysis, RIC did not lead to a significant reduction in the incidence of DGF after kidney transplantation. Nonetheless, RIC demonstrated a positive correlation with 3-month eGFR. Given the limited number of patients included in this study, well-designed clinical trials with large sample sizes are required to validate the renoprotective benefits of RIC.

TRIAL REGISTRATION

This systematic review and meta-analysis was registered at the International Prospective Register of Systematic Reviews (Number CRD42023464447).

Reducing Oxidative Stress and Inflammation by Pyruvate Dehydrogenase Kinase 4 Inhibition Is Important in Prevention of Renal Ischemia-Reperfusion Injury in Diabetic Mice

BACKGRUOUND

Reactive oxygen species (ROS) and inflammation are reported to have a fundamental role in the pathogenesis of ischemia-reperfusion (IR) injury, a leading cause of acute kidney injury. The present study investigated the role of pyruvate dehydrogenase kinase 4 (PDK4) in ROS production and inflammation following IR injury.

METHODS

We used a streptozotocin-induced diabetic C57BL6/J mouse model, which was subjected to IR by clamping both renal pedicles. Cellular apoptosis and inflammatory markers were evaluated in NRK-52E cells and mouse primary tubular cells after hypoxia and reoxygenation using a hypoxia work station.

RESULTS

Following IR injury in diabetic mice, the expression of PDK4, rather than the other PDK isoforms, was induced with a marked increase in pyruvate dehydrogenase E1α (PDHE1α) phosphorylation. This was accompanied by a pronounced ROS activation, as well as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) production. Notably, sodium dichloroacetate (DCA) attenuated renal IR injury-induced apoptosis which can be attributed to reducing PDK4 expression and PDHE1α phosphorylation levels. DCA or shPdk4 treatment reduced oxidative stress and decreased TNF-α, IL-6, IL-1β, and MCP-1 production after IR or hypoxia-reoxygenation injury.

CONCLUSION

PDK4 inhibition alleviated renal injury with decreased ROS production and inflammation, supporting a critical role for PDK4 in IR mediated damage. This result indicates another potential target for reno-protection during IR injury; accordingly, the role of PDK4 inhibition needs to be comprehensively elucidated in terms of mitochondrial function during renal IR injury.

Identification of Differentially Expressed Genes in Cold Storage-associated Kidney Transplantation

BACKGROUND

Although it is acknowledged that ischemia-reperfusion injury is the primary pathology of cold storage-associated kidney transplantation, its underlying mechanism is not well elucidated.

METHODS

To extend the understanding of molecular events and mine hub genes posttransplantation, we performed bulk RNA sequencing at different time points (24 h, day 7, and day 14) on a murine kidney transplantation model with prolonged cold storage (10 h).

RESULTS

In the present study, we showed that genes related to the regulation of apoptotic process, DNA damage response, cell cycle/proliferation, and inflammatory response were steadily elevated at 24 h and day 7. The upregulated gene profiling delicately transformed to extracellular matrix organization and fibrosis at day 14. It is prominent that metabolism-associated genes persistently took the first place among downregulated genes. The gene ontology terms of particular note to enrich are fatty acid oxidation and mitochondria energy metabolism. Correspondingly, the key enzymes of the above processes were the products of hub genes as recognized. Moreover, we highlighted the proximal tubular cell-specific increased genes at 24 h by combining the data with public RNA-Seq performed on proximal tubules. We also focused on ferroptosis-related genes and fatty acid oxidation genes to show profound gene dysregulation in kidney transplantation.

CONCLUSIONS

The comprehensive characterization of transcriptomic analysis may help provide diagnostic biomarkers and therapeutic targets in kidney transplantation.

Interleukin-2/anti-interleukin-2 immune complex attenuates cold ischemia-reperfusion injury after kidney transplantation by increasing renal regulatory T cells

BACKGROUND

Cold ischemia-reperfusion injury (IRI) is an unavoidable complication of kidney transplantation. We investigated the role of regulatory T cells (Treg) in cold IRI and whether the interleukin (IL)-2/anti-IL-2 antibody complex (IL-2C) can ameliorate cold IRI.

METHODS

We developed a cold IRI mouse model using kidney transplantation and analyzed the IL-2C impact on cold IRI in acute, subacute and chronic phases.

RESULTS

Treg transfer attenuated cold IRI, while Treg depletion aggravated cold IRI. Next, IL-2C administration prior to IRI mitigated acute renal function decline, renal tissue damage and apoptosis and inhibited infiltration of effector cells into kidneys and pro-inflammatory cytokine expression on day 1 after IRI. On day 7 after IRI, IL-2C promoted renal regeneration and reduced subacute renal damage. Furthermore, on day 28 following IRI, IL-2C inhibited chronic fibrosis. IL-2C decreased reactive oxygen species-mediated injury and improved antioxidant function. When IL-2C was administered following IRI, it also increased renal regeneration with Treg infiltration and suppressed renal fibrosis. In contrast, Treg depletion in the presence of IL-2C eliminated the positive effects of IL-2C on IRI.

CONCLUSION

Tregs protect kidneys from cold IRI and IL-2C inhibited cold IRI by increasing the renal Tregs, suggesting a potential of IL-2C in treating cold IRI.

KEY POINTS

Interleukin (IL)-2/anti-IL-2 antibody complex attenuated acute renal injury, facilitated subacute renal regeneration and suppressed chronic renal fibrosis after cold ischemia-reperfusion injury (IRI) by increasing the renal Tregs. IL-2/anti-IL-2 antibody complex decreased reactive oxygen species-mediated injury and improved antioxidant function. This study suggests the therapeutic potential of the IL-2/anti-IL-2 antibody complex in kidney transplantation-associated cold IR.

Characteristics of Delayed Graft Function and Long-Term Outcomes After Kidney Transplantation From Brain-Dead Donors: A Single-Center and Multicenter Registry-Based Retrospective Study

Delayed graft function (DGF) after kidney transplantation is common and associated with worse graft outcomes. However, little is known about factors affecting graft survival post-DGF. We studied the association of cold ischemia time (CIT) and Kidney Donor Profile Index (KDPI) with the long-term outcomes of deceased brain-dead donor kidneys with and without DGF. Data from Finland (n = 2,637) and from the US Scientific Registry of Transplant Recipients (SRTR) registry (n = 61,405) was used. The association of KDPI and CIT with the graft survival of kidneys with or without DGF was studied using multivariable models. 849 (32%) kidneys had DGF in the Finnish cohort. DGF and KDPI were independent risk factors for graft loss, [HR 1.32 (95% CI 1.14-1.53), p < 0.001, and HR 1.01 per one point (95% CI 1.01-1.01), p < 0.001, respectively], but CIT was not, [HR 1.00 per CIT hour (95% CI 0.99-1.02), p = 0.84]. The association of DGF remained similar regardless of CIT and KDPI. The US cohort had similar results, but the association of DGF was stronger with higher KDPI. In conclusion, DGF and KDPI, but not CIT, are independently associated with graft survival. The association of DGF with worse graft survival is consistent across different CITs but stronger among marginal donors.

p40 homodimers bridge ischemic tissue inflammation and heterologous alloimmunity in mice via IL-15 transpresentation

Virus-induced memory T cells often express functional cross-reactivity, or heterologous immunity, to other viruses and to allogeneic MHC molecules that is an important component of pathogenic responses to allogeneic transplants. During immune responses, antigen-reactive naive and central memory T cells proliferate in secondary lymphoid organs to achieve sufficient cell numbers to effectively respond, whereas effector memory T cell proliferation occurs directly within the peripheral inflammatory microenvironment. Mechanisms driving heterologous memory T cell proliferation and effector function expression within peripheral tissues remain poorly understood. Here, we dissected proliferation of heterologous donor-reactive memory CD8+ T cells and their effector functions following infiltration into heart allografts with low or high intensities of ischemic inflammation. Proliferation within both ischemic conditions required p40 homodimer-induced IL-15 transpresentation by graft DCs, but expression of effector functions mediating acute allograft injury occurred only in high-ischemic allografts. Transcriptional responses of heterologous donor-reactive memory CD8+ T cells were distinct from donor antigen-primed memory CD8+ T cells during early activation in allografts and at graft rejection. Overall, the results provide insights into mechanisms driving heterologous effector memory CD8+ T cell proliferation and the separation between proliferation and effector function that is dependent on the intensity of inflammation within the tissue microenvironment.

Kidney Survival Impact of Delayed Graft Function Depends on Kidney Donor Risk Index: A Single-Center Cohort Study

BACKGROUND

Delayed graft function (DGF) is a significant challenge in renal transplantation, particularly with deceased donors, necessitating early postoperative dialysis. The prolonged effects of medium- and long-term DGF remain uncertain, marked by contradictory graft survival outcomes. This incongruity might arise from the inherent graft resilience and regenerative capacity during transplantation. This study investigates DGF's impact on graft survival, focusing on grafts displaying favorable (KDRI < 1) and unfavorable outcomes (KDRI ≥ 1).

METHODS

In this retrospective cohort study (January 2015-December 2019), we assessed kidney transplants at our center, excluding multiorgan simultaneous cases, primary non-functioning grafts, and surgical complications causing graft loss. Patients were categorized into DGF presence or absence groups. Univariate and multivariate analyses, alongside propensity score matching (PSM), were performed.

RESULTS

The study encompassed 322 deceased donor kidneys, with 83 encountering DGF. Grafts with higher KDRI indices (KDRI ≥ 1) and DGF exhibited a notably increased graft loss risk (HR: 4.17, 95% CI: 1.93-9.01). However, lower-KDRI donor grafts displayed no significant disparities between the DGF and non-DGF groups.

CONCLUSIONS

Delayed graft function (DGF) development significantly contributes to graft loss in kidney transplants, particularly in grafts with KDRI ≥ 1.

Identification of signature genes for renal ischemia‒reperfusion injury based on machine learning and WGCNA

Background

As an inevitable event after kidney transplantation, ischemia‒reperfusion injury (IRI) can lead to a decrease in kidney transplant success. The search for signature genes of renal ischemia‒reperfusion injury (RIRI) is helpful in improving the diagnosis and guiding clinical treatment.

Methods

We first downloaded 3 datasets from the GEO database. Then, differentially expressed genes (DEGs) were identified and applied for functional enrichment analysis. After that, we performed three machine learning methods, including random forest (RF), Lasso regression analysis, and support vector machine recursive feature elimination (SVM-RFE), to further predict candidate genes. WGCNA was also executed to screen candidate genes from DEGs. Then, we took the intersection of candidate genes to obtain the signature genes of RIRI. Receiver operating characteristic (ROC) analysis was conducted to measure the predictive ability of the signature genes. Kaplan‒Meier analysis was used for association analysis between signature genes and graft survival. Verifying the expression of signature genes in the ischemia cell model.

Results

A total of 117 DEGs were screened out. Subsequently, RF, Lasso regression analysis, SVM-RFE and WGCNA identified 17, 25, 18 and 74 candidate genes, respectively. Finally, 3 signature genes (DUSP1, FOS, JUN) were screened out through the intersection of candidate genes. ROC analysis suggested that the 3 signature genes could well diagnose and predict RIRI. Kaplan‒Meier analysis indicated that patients with low FOS or JUN expression had a longer OS than those with high FOS or JUN expression. Finally, we validated using the ischemia cell model that compared to the control group, the expression level of JUN increased under hypoxic conditions.

Conclusions

Three signature genes (DUSP1, FOS, JUN) offer a good prediction for RIRI outcome and may serve as potential therapeutic targets for RIRI intervention, especially JUN. The prediction of graft survival by FOS and JUN may improve graft survival in patients with RIRI.

Predicting Long-term Outcomes in Deceased Donor Kidney Transplant Recipients Using Three Short-term Graft Characteristics

Key Points

Delayed graft function is not an ideal measure of graft function, yet is used to assess risk in kidney transplantation. We propose a model that combines it with two other measures of 90-day graft function to identify recipients at incremental risk of inferior long-term outcomes.

Background

Delayed graft function (DGF) in kidney transplant recipients is used to determine graft prognosis, make organ utilization decisions, and as an important end point in clinical trials. However, DGF is not an ideal measure of graft function. We aimed to develop and validate a model that provides incremental risk assessment for inferior patient and graft outcomes.

Methods

We included adult kidney-only deceased donor transplant recipients from 1996 to 2016. In addition to DGF, two short-term measures were used to assess risk: renal function recovery <100% (attaining half the donor's eGFR) and recipient's 90-day eGFR <30. Recipients were at no, low, moderate, or high risk if they met zero, one, two, or all criteria, respectively. Cox proportional hazard models were used to assess the independent relationship between exposure and death-censored graft failure (DCGF) and mortality.

Results

Of the 792 eligible recipients, 24.5% experienced DGF, 40.5% had renal function recovery <100%, and 6.9% had eGFR <30. Over a median follow-up of 7.3 years, the rate of DCGF was 18.7% and mortality was 25.1%. When compared with recipients at no risk, those at low, moderate, and high risk were noted to have an increase in risk of DCGF (adjusted hazard ratio [aHR], 1.53; 95% confidence interval [CI], 1.03 to 2.27; aHR, 2.84; 95% CI, 1.68 to 4.79; aHR, 15.46; 95% CI, 8.04 to 29.71) and mortality (aHR, 1.16; 95% CI, 0.84 to 1.58; aHR, 1.85; 95% CI, 1.13 to 3.07; aHR, 2.66; 95% CI, 1.19 to 5.97). When using a hierarchical approach, each additional exposure predicted the risk of DCGF better than DGF alone and 100 random bootstrap replications supported the internal validity of the risk model. In an external validation cohort deemed to be at lower risk of DCGF, similar nonsignificant trends were noted.

Conclusion

We propose a risk model that provides an incremental assessment of recipients at higher risk of adverse long-term outcomes than DGF alone. This can help advance the field of risk assessment in transplantation and inform therapeutic decision making in patients at the highest spectrum of inferior outcomes.

Renal Function at Discharge Among Kidney Recipients Experiencing Delayed Graft Function and Its Associations With Long-term Outcomes

Delayed graft function (DGF) after kidney transplantation is associated with higher rates of acute rejection and poor graft survival and outcomes. Current DGF definitions based on posttransplant need for dialysis are not standardized and there are no objective methodologies for quantifying DGF severity.

METHODS

Using Organ Procurement and Transplantation Network data, we examined DGF, and used recipient serum creatinine at discharge as a correlate of renal function and DGF severity (mild: <2.5 mg/dL; severe: ≥2.5 mg/dL). The associations between donor and recipient factors and DGF severity were quantified using logistic regression. We also examined the associations between DGF severity and long-term recipient outcomes, adjusting for potential confounders.

RESULTS

A predictive model using donor and recipient factors had a reasonably good ability to discriminate mild (low creatinine) versus severe (high creatinine) DGF (c-statistic of 0.70). In Cox regression, DGF and creatinine at discharge were both independently associated with long-term outcomes, yet their effects differed depending on the outcome (graft function, death-censored graft function, recipient mortality). Our findings suggest that having DGF, but with relatively good renal function (creatinine <2.5) at discharge, may be less deleterious on graft and recipient survival compared with severe, prolonged DGF, which was associated with a decreased median graft survival of ~2.6 y compared with no DGF with low creatinine at discharge.

CONCLUSIONS

Our novel DGF severity stratification identified unique factors associated with DGF severity, along with DGF's association with long-term graft and patient survival. The adverse cost and outcome implications of severe DGF warrant additional investigation to improve kidney transplantation practice.

Clinical Outcomes of Transplanted Kidneys from Deceased Donors Using Different Generic Preservation Solutions

Background and Objectives: StoreProtect Plus® is a preserving solution for cold organ storage, with a composition identical to Institute Georges Lopez (IGL-1) solution. The aim of this single center study was to compare the clinical performance of StoreProtect Plus with the generic counterpart of University of Wisconsin preservation fluid, named SPS-1®. Materials and Methods: The clinical outcomes of 168 consecutive organs preserved with StoreProtect Plus solution and 167 organs preserved with SPS-1 solution were compared. During an 18-month post-transplant follow-up period, kidney graft function, the frequency of acute rejection, post-transplant diabetes, and infectious complications, as well as patient and graft survival were analyzed. Results: There was significantly more immediate graft function (IGF) (39.3 vs. 24.0%; p < 0.01) and less slow graft function (SGF) (38.7 vs. 51.5%; p < 0.05) in the StoreProtect Plus group in comparison with the SPS-1 group, whereas the occurrence of DGF was similar in both groups. Long-term kidney graft function was comparable. Multivariate regression analysis showed that the use of StoreProtect Plus vs. SPS-1 solution (rpartial = 0.217; p < 0.001) and the amount of residual diuresis (rpartial = 0.147; p < 0.001) independently increased the occurrence of IGF, whereas Scr > 1.5 mg/dL prior to organ procurement (rpartial = −0.198; p < 0.001), longer CIT (rpartial = −0.170; p < 0.01), and CVD donor death (rpartial = −0.214; p < 0.001) were associated with SGF. Conclusions: The higher occurrence of IGF was found in kidney transplant recipients whose organs were preserved using StoreProtect Plus solution as compared with SPS-1 solution. The two groups did not differ in kidney graft function, the frequency of post-transplant complications, as well as patient and graft survival.

Epigenetic memory contributing to the pathogenesis of AKI-to-CKD transition

Epigenetic memory, which refers to the ability of cells to retain and transmit epigenetic marks to their daughter cells, maintains unique gene expression patterns. Establishing programmed epigenetic memory at each stage of development is required for cell differentiation. Moreover, accumulating evidence shows that epigenetic memory acquired in response to environmental stimuli may be associated with diverse diseases. In the field of kidney diseases, the “memory” of acute kidney injury (AKI) leads to progression to chronic kidney disease (CKD); epidemiological studies show that patients who recover from AKI are at high risk of developing CKD. The underlying pathological processes include nephron loss, maladaptive epithelial repair, inflammation, and endothelial injury with vascular rarefaction. Further, epigenetic alterations may contribute as well to the pathophysiology of this AKI-to-CKD transition. Epigenetic changes induced by AKI, which can be recorded in cells, exert long-term effects as epigenetic memory. Considering the latest findings on the molecular basis of epigenetic memory and the pathophysiology of AKI-to-CKD transition, we propose here that epigenetic memory contributing to AKI-to-CKD transition can be classified according to the presence or absence of persistent changes in the associated regulation of gene expression, which we designate “driving” memory and “priming” memory, respectively. “Driving” memory, which persistently alters the regulation of gene expression, may contribute to disease progression by activating fibrogenic genes or inhibiting renoprotective genes. This process may be involved in generating the proinflammatory and profibrotic phenotypes of maladaptively repaired tubular cells after kidney injury. “Priming” memory is stored in seemingly successfully repaired tubular cells in the absence of detectable persistent phenotypic changes, which may enhance a subsequent transcriptional response to the second stimulus. This type of memory may contribute to AKI-to-CKD transition through the cumulative effects of enhanced expression of profibrotic genes required for wound repair after recurrent AKI. Further understanding of epigenetic memory will identify therapeutic targets of future epigenetic intervention to prevent AKI-to-CKD transition.

A Potential Route to Reduce Ischemia/Reperfusion Injury in Organ Preservation

The pathophysiological process of ischemia and reperfusion injury (IRI), an inevitable step in organ transplantation, causes important biochemical and structural changes that can result in serious organ damage. IRI is relevant for early graft dysfunction and graft survival. Today, in a global context of organ shortages, most organs come from extended criteria donors (ECDs), which are more sensitive to IRI. The main objective of organ preservation solutions is to protect against IRI through the application of specific, nonphysiological components, under conditions of no blood or oxygen, and then under conditions of metabolic reduction by hypothermia. The composition of hypothermic solutions includes osmotic and oncotic buffering components, and they are intracellular (rich in potassium) or extracellular (rich in sodium). However, above all, they all contain the same type of components intended to protect against IRI, such as glutathione, adenosine and allopurinol. These components have not changed for more than 30 years, even though our knowledge of IRI, and much of the relevant literature, questions their stability or efficacy. In addition, several pharmacological molecules have been the subjects of preclinical studies to optimize this protection. Among them, trimetazidine, tacrolimus and carvedilol have shown the most benefits. In fact, these drugs are already in clinical use, and it is a question of repositioning them for this novel use, without additional risk. This new strategy of including them would allow us to shift from cold storage solutions to cold preservation solutions including multitarget pharmacological components, offering protection against IRI and thus protecting today's more vulnerable organs.

Epigenetic Regulation in Kidney Transplantation

Kidney transplantation is a standard care for end stage renal disease, but it is also associated with a complex pathogenesis including ischemia-reperfusion injury, inflammation, and development of fibrosis. Over the past decade, accumulating evidence has suggested a role of epigenetic regulation in kidney transplantation, involving DNA methylation, histone modification, and various kinds of non-coding RNAs. Here, we analyze these recent studies supporting the role of epigenetic regulation in different pathological processes of kidney transplantation, i.e., ischemia-reperfusion injury, acute rejection, and chronic graft pathologies including renal interstitial fibrosis. Further investigation of epigenetic alterations, their pathological roles and underlying mechanisms in kidney transplantation may lead to new strategies for the discovery of novel diagnostic biomarkers and therapeutic interventions.

Artificial oxygen carriers in organ preservation: Dose dependency in a rat model of ex-vivo normothermic kidney perfusion

INTRODUCTION

Organ preservation through ex-vivo normothermic perfusion (EVNP) with albumin-derived perfluorocarbon-based artificial oxygen carriers (A-AOCs) consisting of albumin-derived perfluorodecalin-filled nanocapsules prior to transplantation would be a promising approach to avoid hypoxic tissue injury during organ storage.

METHODS

The kidneys of 16 rats underwent EVNP for 2 h with plasma-like solution (5% bovine serum albumin, Ringer-Saline, inulin) with or without A-AOCs in different volume fractions (0%, 2%, 4%, or 8%). Cell death was determined using TdT-mediated dUTP-biotin nick end labeling (TUNEL). Aspartate transaminase (AST) activity in both perfusate and urine as well as the glomerular filtration rate (GFR) were determined. The hypoxia inducible factors 1α and 2α (HIF-1α und -2α) were quantified in tissue homogenates.

RESULTS

GFR was substantially decreased in the presence of 0%, 2%, and 8% A-AOC but not of 4%. In accordance, hypoxia-mediated cell death, as indicated by both AST activity and TUNEL-positive cells, was significantly decreased in the 4% group compared to the control group. The stabilization of HIF-1α and 2α decreased with 4% and 8% but not with 2% A-AOCs.

CONCLUSION

The dosage of 4% A-AOCs in EVNP was most effective in maintaining the physiological renal function.

Preclinical models versus clinical renal ischemia reperfusion injury: A systematic review based on metabolic signatures

Despite decennia of research and numerous successful interventions in the preclinical setting, renal ischemia reperfusion (IR) injury remains a major problem in clinical practice, pointing toward a translational gap. Recently, two clinical studies on renal IR injury (manifested either as acute kidney injury or as delayed graft function) identified metabolic derailment as a key driver of renal IR injury. It was reasoned that these unambiguous metabolic findings enable direct alignment of clinical with preclinical data, thereby providing the opportunity to elaborate potential translational hurdles between preclinical research and the clinical context. A systematic review of studies that reported metabolic data in the context of renal IR was performed according to the PRISMA guidelines. The search (December 2020) identified 35 heterogeneous preclinical studies. The applied methodologies were compared, and metabolic outcomes were semi-quantified and aligned with the clinical data. This review identifies profound methodological challenges, such as the definition of IR injury, the follow-up time, and sampling techniques, as well as shortcomings in the reported metabolic information. In light of these findings, recommendations are provided in order to improve the translatability of preclinical models of renal IR injury.

Risk Prediction for Delayed Allograft Function: Analysis of the Deterioration of Kidney Allograft Function (DeKAF) Study Data

BACKGROUND

Delayed graft function (DGF) of a kidney transplant results in increased cost and complexity of management. For clinical care or a DGF trial, it would be ideal to accurately predict individual DGF risk and provide preemptive treatment. A calculator developed by Irish et al has been useful for predicting population but not individual risk.

METHODS

We analyzed the Irish calculator (IC) in the DeKAF prospective cohort (incidence of DGF = 20.4%) and investigated potential improvements.

RESULTS

We found that the predictive performance of the calculator in those meeting Irish inclusion criteria was comparable with that reported by Irish et al. For cohorts excluded by Irish: (a) in pump-perfused kidneys, the IC overestimated DGF risk; (b) in simultaneous pancreas kidney transplants, the DGF risk was exceptionally low. For all 3 cohorts, there was considerable overlap in IC scores between those with and those without DGF. Using a modified definition of DGF-excluding those with single dialysis in the first 24 h posttransplant-we found that the calculator had similar performance as with the traditional DGF definition. Studying whether DGF prediction could be improved, we found that recipient cardiovascular disease was strongly associated with DGF even after accounting for IC-predicted risk.

CONCLUSIONS

The IC can be a useful population guide for predicting DGF in the population for which it was intended but has limited scope in expanded populations (SPK, pump) and for individual risk prediction. DGF risk prediction can be improved by inclusion of recipient cardiovascular disease.

Proximal Tubule p53 in Cold Storage/Transplantation-Associated Kidney Injury and Renal Graft Dysfunction

Kidney injury associated with cold storage/transplantation is a primary factor for delayed graft function and poor outcome of renal transplants. p53 contributes to both ischemic and nephrotoxic kidney injury, but its involvement in kidney cold storage/transplantation is unclear. Here, we report that p53 in kidney proximal tubules plays a critical role in cold storage/transplantation kidney injury and inhibition of p53 can effectively improve the histology and function of transplanted kidneys. In a mouse kidney cold storage/transplantation model, we detected p53 accumulation in proximal tubules in a cold storage time-dependent manner, which correlated with tubular injury and cell death. Pifithrin-α, a pharmacologic p53 inhibitor, could reduce acute tubular injury, apoptosis and inflammation at 24 h after cold storage/transplantation. Similar effects were shown by the ablation of p53 from proximal tubule cells. Notably, pifithrin-α also ameliorated kidney injury and improved the function of transplanted kidneys in 6 days when it became the sole life-supporting kidney in recipient mice. in vitro, cold storage followed by rewarming induced cell death in cultured proximal tubule cells, which was accompanied by p53 activation and suppressed by pifithrin-α and dominant-negative p53. Together, these results support a pathogenic role of p53 in cold storage/transplantation kidney injury and demonstrate the therapeutic potential of p53 inhibitors.

Evaluation of severity of delayed graft function in kidney transplant recipients

BACKGROUND

The most common definition of delayed graft function (DGF) relies on dialysis during the first week post-transplant and does not consider DGF severity. The impact of DGF severity on long-term graft outcome remains controversial.

METHODS

We analyzed 627 deceased-donor kidney transplant recipients (KTR) transplanted 2005-2015 at our center for DGF-severity, associated risk factors and long-term consequences of DGF.

RESULTS

We found 349 (55.7%) KTR with DGF, which were classified into 4 groups according to DGF duration (0-1, 2-7, 8-14, >14 days) and were compared to KTR with no DGF. Increasing duration of DGF was associated with progressive worsening of 10-year death-censored graft survival (no DGF: 88.3% (95%CI: 82.4-94.2), 0-1 day: 81.3% (95%CI: 68.2-94.4), 2-7 days: 61.5% (95%CI: 43.1.1-79.9), 8-14 days: 66.6% (95%CI: 47.4-85.8), >14 days: 51.2% (95%CI: 33-69.4); p < 0.001). In kidneys with a Kidney Donor Profile Index (KDPI) ≥85% all DGF severity groups demonstrated reduced graft survival. However, in < 85%KDPI kidneys, only > 14 days DGF duration showed worse outcomes.

CONCLUSIONS

DGF had a duration-dependent effect on graft survival, which varied depending on KDPI. Of note, 0-1-day DGF showed comparable results to no DGF in the whole cohort.

Plasma Macrophage Migration Inhibitory Factor Predicts Graft Function Following Kidney Transplantation: A Prospective Cohort Study

Background: Delayed graft function (DGF) is a common complication after kidney transplantation (KT) with a poor clinical outcome. There are no accurate biomarkers for the early prediction of DGF. Macrophage migration inhibitory factor (MIF) release during surgery plays a key role in protecting the kidney, and may be a potential biomarker for predicting post-transplant renal allograft recovery.

Methods: Recipients who underwent KT between July 2020 and December 2020 were enrolled in the study. Plasma MIF levels were tested in recipients at different time points, and the correlation between plasma MIF and DGF in recipients was evaluated. This study was registered in the Chinese Clinical Trial Registry (ChiCTR2000035596).

Results: Intraoperative MIF levels were different between immediate, slowed, and delayed graft function groups (7.26 vs. 6.49 and 5.59, P < 0.001). Plasma MIF was an independent protective factor of DGF (odds ratio = 0.447, 95% confidence interval [CI] 0.264–0.754, P = 0.003). Combining plasma MIF level and donor terminal serum creatinine provided the best predictive power for DGF (0.872; 95%CI 0.795–0.949). Furthermore, plasma MIF was significantly associated with allograft function at 1-month post-transplant (R² = 0.42, P < 0.001).

Conclusion: Intraoperative MIF, as an independent protective factor for DGF, has excellent diagnostic performance for predicting DGF and is worthy of further exploration.

Caspase-3-dependent peritubular capillary dysfunction is pivotal for the transition from acute to chronic kidney disease after acute ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a major risk factor for chronic renal failure. Caspase-3, an effector responsible for apoptosis execution, is activated within the peritubular capillary (PTC) in the early stage of IRI-induced acute kidney injury (AKI). Recently, we showed that caspase-3-dependent microvascular rarefaction plays a key role in fibrosis development after mild renal IRI. Here, we further characterized the role of caspase-3 in microvascular dysfunction and progressive renal failure in both mild and severe AKI, by performing unilateral renal artery clamping for 30/60 min with contralateral nephrectomy in wild-type (C57BL/6) or caspase-3-/- mice. In both forms of AKI, caspase-3-/- mice showed better long-term outcomes despite worse initial tubular injury. After 3 wk, they showed reduced PTC injury, decreased PTC collagen deposition and α-smooth muscle actin expression, and lower tubular injury scores compared with wild-type animals. Caspase-3-/- mice with severe IRI also showed better preservation of long-term renal function. Intravital imaging and microcomputed tomography revealed preserved PTC permeability and better terminal capillary density in caspase-3-/- mice. Collectively, these results demonstrate the pivotal importance of caspase-3 in regulating long-term renal function after IRI and establish the predominant role of PTC dysfunction as a major contributor to progressive renal dysfunction.NEW & NOTEWORTHY Our findings demonstrate the pivotal importance of caspase-3 in regulating renal microvascular dysfunction, fibrogenesis, and long-term renal impairment after acute kidney injury induced by ischemia-reperfusion injury. Furthermore, this study establishes the predominant role of peritubular capillary integrity as a major contributor to progressive renal dysfunction after ischemia-reperfusion injury.

Mitochondrial DNA may act as a biomarker to predict donor-kidney quality

Kidney transplantation is the best therapy for end-stage renal disease. Demand for kidney transplantation rises year-on-year, and the gap between kidney supply and demand remains large. To meet this clinical need, a gradual expansion in the supply of donors is required. However, clinics lack appropriate tools capable of quickly and accurately predicting post-transplant renal allograft function, and thus assess donor-kidney quality before transplantation. Mitochondrial DNA (mtDNA) is a key component of damage-associated molecular patterns (DAMPs) and plays an important part in ischemia-reperfusion injury (IRI), accelerating the progression of IRI by inducing inflammation and type I interferon responses. mtDNA is known to be closely involved in delayed graft function (DGF) and acute kidney injury (AKI) after transplantation. Thus, mtDNA is a potential biomarker able to predict post-transplant renal allograft function. This review summarizes mtDNA biology, the role mtDNA plays in renal transplantation, outlines advances in detecting mtDNA, and details mtDNA's able to predict post-transplant renal allograft function. We aim to elucidate the potential value of mtDNA as a biomarker in the prediction of IRI, and eventually provide help for predicting donor-kidney quality.

The inflammatory state is a risk factor for cardiovascular disease and graft fibrosis in kidney transplantation

Several factors, such as donor brain death, ischemia-reperfusion injury, rejection, infection, and chronic allograft dysfunction, may induce an inflammatory state in kidney transplantation. Furthermore, inflammatory cells, cytokines, growth factors, complement and coagulation cascade create an unbalanced interaction with innate and adaptive immunity, which are both heavily involved in atherogenesis. The crosstalk between inflammation and thrombosis may lead to a prothrombotic state and impaired fibrinolysis in kidney transplant recipients increasing the risk of cardiovascular disease. Inflammation is also associated with elevated levels of fibroblast growth factor 23 and low levels of Klotho, which contribute to major adverse cardiovascular events. Hyperuricemia, glucose intolerance, arterial hypertension, dyslipidemia, and physical inactivity may create a condition called metaflammation that concurs in atherogenesis. Another major consequence of the inflammatory state is the development of chronic hypoxia that through the mediation of interleukins 1 and 6, angiotensin II, and transforming growth factor beta can result in excessive accumulation of extracellular matrix, which can disrupt and replace functional parenchyma, leading to interstitial fibrosis and chronic allograft dysfunction. Lifestyle and regular physical activity may reduce inflammation. Several drugs have been proposed to control the graft inflammatory state, including low-dose aspirin, statins, renin-angiotensin inhibitors, xanthine-oxidase inhibitors, vitamin D supplements, and interleukin-6 blockade. However, no prospective controlled trial with these measures has been conducted in kidney transplantation.

Influenza vaccination uptake and factors influencing vaccination decision among patients with chronic kidney or liver disease

Introduction

Seasonal influenza is a major global health problem causing substantial morbidity and health care costs. Yet, in many countries, the rates of influenza vaccination remain low. Chronic kidney or liver diseases (CKLD) predispose patients to severe influenza infections, but data on vaccination acceptance and status is limited in this risk population. We investigated the influenza vaccination awareness considering sociodemographic factors in CKLD patients.

Patients and methods

This cross-sectional, questionnaire-based study recruited CKLD patients managed at three Viennese tertiary care centers between July and October 2020. CKLD was defined as chronic kidney- (all stages) or compensated/decompensated liver disease, including kidney/liver transplant recipients. Questionnaires assessed sociodemographic and transplant- associated parameters, patients vaccination status and the individuals self-perceived risks of infection and associated complications.

Results

In total 516 patients (38.1% female, mean age 56.4 years) were included. 43.9% of patients declared their willingness to be vaccinated in the winter season 2020/2021, compared to 25.4% in 2019/2020 and 27.3% in 2016–2018. Vaccination uptake was associated with the self-perceived risks of infection (OR: 2.8 (95%CI: 1.8–4.5), p<0.001) and associated complications (OR: 3.8 (95%CI: 2.3–6.3), p<0.001) as well as with previously received influenza vaccination (2019/2020: OR 17.1 (95%CI: 9.5–30.7), p<0.001; season 2016–2018: OR 8.9 (95%CI: 5.5–14.5), p<0.001). Most frequent reasons for not planning vaccination were fear of a) graft injury (33.3%), b) complications after vaccination (32.4%) and c) vaccine inefficiency (15.0%).

Conclusion

While influenza vaccination willingness in patients with CKLD is increasing in the 2020/2021 season, vaccination rates may still remain <50%. Novel co-operations with primary health care, active vaccination surveillance and financial reimbursement may substantially improve vaccination rates in high-risk CKLD patients.

Acute Kidney Injury, Microvascular Rarefaction, and Estimated Glomerular Filtration Rate in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Animal studies suggest that microvascular rarefaction is a key factor in the acute kidney disease to CKD transition. Hence, delayed graft function appears as a unique human model of AKI to further explore the role of microvascular rarefaction in kidney transplant recipients. Here, we assessed whether delayed graft function is associated with peritubular capillary loss and evaluated the association between this loss and long-term kidney graft function.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational, retrospective cohort study included 61 participants who experienced delayed graft function and 130 who had immediate graft function. We used linear regression models to evaluate associations between delayed graft function and peritubular capillary density expressed as the percentage of efficient cortical area occupied by peritubular capillaries in pre- and post-transplant graft biopsies. eGFRs 1 and 3 years post-transplant were secondary outcomes.

RESULTS

Post-transplant biopsies were performed at a median of 113 days (interquartile range, 101-128) after transplantation. Peritubular capillary density went from 15.4% to 11.5% in patients with delayed graft function (median change, -3.7%; interquartile range, -6.6% to -0.8%) and from 19.7% to 15.1% in those with immediate graft function (median change, -4.5%; interquartile range, -8.0% to -0.8%). Although the unadjusted change in peritubular capillary density was similar between patients with and without delayed graft function, delayed graft function was associated with more peritubular capillary loss in the multivariable analysis (adjusted difference in change, -2.9%; 95% confidence interval, -4.0 to -1.8). Pretransplant peritubular capillary density and change in peritubular capillary density were associated with eGFR 1 and 3 years post-transplantation.

CONCLUSIONS

Perioperative AKI is associated with lower density in peritubular capillaries before transplantation and with loss of peritubular capillaries following transplantation. Lower peritubular capillary density is linked to lower long-term eGFR.

Prevention of Chronic Rejection of Marginal Kidney Graft by Using a Hydrogen Gas-Containing Preservation Solution and Adequate Immunosuppression in a Miniature Pig Model

In clinical kidney transplantation, the marginal kidney donors are known to develop chronic allograft rejection more frequently than living kidney donors. In our previous study, we have reported that the hydrogen gas-containing organ preservation solution prevented the development of acute injuries in the kidney of the donor after cardiac death by using preclinical miniature pig model. In the present study, we verified the impact of hydrogen gas treatment in transplantation with the optimal immunosuppressive protocol based on human clinical setting by using the miniature pig model. Marginal kidney processed by hydrogen gas-containing preservation solution has been engrafted for long-term (longer than 100 days). A few cases showed chronic rejection reaction; however, most were found to be free of chronic rejection such as graft tissue fibrosis or renal vasculitis. We concluded that marginal kidney graft from donor after cardiac death is an acceptable model for chronic rejection and that if the transplantation is carried out using a strict immunosuppressive protocol, chronic rejection may be alleviated even with the marginal kidney.

Kidney-intrinsic factors determine the severity of ischemia/reperfusion injury in a mouse model of delayed graft function

Delayed graft function due to transplant ischemia/reperfusion injury adversely affects up to 50% of deceased-donor kidney transplant recipients. However, key factors contributing to the severity of ischemia/reperfusion injury remain unclear. Here, using a clinically relevant mouse model of delayed graft function, we demonstrated that donor genetic background and kidney-intrinsic MyD88/Trif-dependent innate immunity were key determinants of delayed graft function. Functional deterioration of kidney grafts directly corresponded with the duration of cold ischemia time. The graft dysfunction became irreversible after cold ischemia time exceeded six hours. When cold ischemia time reached four hours, kidney grafts displayed histological features reflective of delayed graft function seen in clinical kidney transplantation. Notably, kidneys of B6 mice exhibited significantly more severe histological and functional impairment than kidneys of C3H or BALB/c mice, regardless of recipient strains or alloreactivities. Furthermore, allografts of B6 mice also showed an upregulation of IL-6, neutrophil gelatinase-associated lipocalin, and endoplasmic reticulum stress genes, as well as an increased influx of host neutrophils and memory CD8 T-cells. In contrast, donor MyD88/Trif deficiency inhibited neutrophil influx and decreased the expression of IL-6 and endoplasmic reticulum stress genes, along with improved graft function and prolonged allograft survival. Thus, kidney-intrinsic factors involving genetic characteristics and innate immunity serve as critical determinants of the severity of delayed graft function. This preclinical murine model allows for further investigations of the mechanisms underlying delayed graft function.

Quantitative evaluation of dexamethasone treatment effects in renal ischemia-reperfusion injury using contrast enhanced ultrasonography in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury often occurs in various clinical events, and its incidence and mortality have been increasing.

OBJECTIVE

To investigate the value of contrast enhanced ultrasonography (CEUS) in the monitoring of dexamethasone in the improvement of renal I/R injury in rats.

METHODS

Eighteen healthy male Sprague-Dawley rats were randomly divided into sham-operated, I/R, and I/R surgery plus dexamethasone treatment (Dexa) groups. In the I/R group 45-minute renal ischemia with 24 h reperfusion period was monitored. Time-intensity curve (TIC)-derived parameters, which included peak value, time to peak (TP), area under the curve (AUC), and mean transit time (MTT) were compared to the blood creatinine, urea, Caspase-1, and NLRP3 levels.

RESULTS

The I/R group showed an increased peak value, prolonged TP and MTT, and greater AUC (P < 0.05). The Dexa group showed shorter TP and MTT, and smaller AUC (P < 0.05). Results show that the associations between (i) TP, AUC, and MTT and (ii) creatinine, urea, Caspase-1, and NLRP3 levels were significant (P < 0.05).

CONCLUSION

Dexamethasone can alleviate renal I/R injury in rats, which may be related to the inhibition of NLRP3 and caspase-1. CEUS can quantitatively measure this change, in which the changes in TP, AUC and MMT values have considerable reference values.

Results of an explorative clinical evaluation suggest immediate and persistent post-reperfusion metabolic paralysis drives kidney ischemia reperfusion injury

Delayed graft function is the manifestation of ischemia reperfusion injury in the context of kidney transplantation. While hundreds of interventions successfully reduce ischemia reperfusion injury in experimental models, all clinical interventions have failed. This explorative clinical evaluation examined possible metabolic origins of clinical ischemia reperfusion injury combining data from 18 pre- and post-reperfusion tissue biopsies with 36 sequential arteriovenous blood samplings over the graft in three study groups. These groups included living and deceased donor grafts with and without delayed graft function. Group allocation was based on clinical outcome. Magic angle NMR was used for tissue analysis and mass spectrometry-based platforms were used for plasma analysis. All kidneys were functional at one-year. Integration of metabolomic data identified a discriminatory profile to recognize future delayed graft function. This profile was characterized by post-reperfusion ATP/GTP catabolism (significantly impaired phosphocreatine recovery and significant persistent (hypo)xanthine production) and significant ongoing tissue damage. Failing high-energy phosphate recovery occurred despite activated glycolysis, fatty-acid oxidation, glutaminolysis and autophagia, and related to a defect at the level of the oxoglutarate dehydrogenase complex in the Krebs cycle. Clinical delayed graft function due to ischemia reperfusion injury associated with a post-reperfusion metabolic collapse. Thus, efforts to quench delayed graft function due to ischemia reperfusion injury should focus on conserving metabolic competence, either by preserving the integrity of the Krebs cycle and/or by recruiting metabolic salvage pathways.

Review 1: Lung transplant-from donor selection to graft preparation

For various end-stage lung diseases, lung transplantation remains one of the only viable treatment options. While the demand for lung transplantation has steadily risen over the last few decades, the availability of donor grafts is limited, which have resulted in progressively longer waiting lists. In the early years of lung transplantation, only the 'ideal' donor grafts are considered for transplantation. Due to the donor shortages, there is ongoing discussion about the safe use of 'suboptimal' grafts to expand the donor pool. In this review, we will discuss the considerations around donor selection, donor-recipient matching, graft preparation and graft optimisation.

Early graft function and intrarenal resistant index after kidney transplantation using Biolasol-A new solid organ preservation fluid

Biolasol is a newly developed preserving solution for cold organ storage prior to transplantation. To date, only animal model experiments results are available. The aim of this single-center analysis was to summarize the clinical experience concerning the early post-transplant course of kidney grafts preserved with Biolasol in comparison with other preservation solutions. Before transplantation, 173 kidney grafts were preserved using Biolasol and 240 organs with other solutions (University of Wisconsin-UW, Institute Georges Lopez-IGL-1, or StoreProtect Plus solutions). Early graft function was defined based on serum creatinine concentration at day 3 (<3 mg/dL-immediate graft function, IGF or >3 mg/dL-slow graft function, SGF) or the need of dialysis therapy during first post-operative week (delayed graft function, DGF). The analysis included intrarenal resistive indices measured by Doppler sonography early after transplantation and before discharge from the hospital. IGF was more frequent in patients with organs preserved with IGL-1 (33.5%) and StoreProtect Plus (38.8%) than Biolasol (18.5%), whereas there was no difference in the occurrence of DGF. Both initial and discharge median resistance index values were significantly higher in the Biolasol subgroup (0.77 and 0.75) than in all three other subgroups (P values for all comparisons <.001), also after 1:1 propensity score matching for baseline characteristics. Multiple logistic regression analysis based on the propensity score-matched cohort revealed that the use of Biolasol solution [OR 0.59 (0.35-0.98); P < .05] independently decreased the occurrence of IGF. In our single-center clinical experience, kidney preservation using Biolasol solution was associated with significantly higher intrarenal resistant index in comparison with other preservation fluids, as well as worse early graft function than in the IGL-1 and the StoreProtect Plus subgroups. Long-term follow-up is needed in order to assess the kidney graft and patient survival.

Prognostic value for long-term graft survival of estimated glomerular filtration rate and proteinuria quantified at 3 months after kidney transplantation

Background

The estimated glomerular filtration rate (eGFR) measured at 1 year is the usual benchmark applied in kidney transplantation (KT). However, acting on earlier eGFR values could help in managing KT during the first post-operative year. We aimed to assess the prognostic value for long-term graft survival of the early (3 months) quantification of eGFR and proteinuria following KT.

Methods

The 3-, 6- and 12-month eGFR using the Modified Diet in Renal Disease equation (eGFR_MDRD) was determined and proteinuria was measured in 754 patients who underwent their first KT between 2000 and 2010 (with a mean follow-up of 8.3 years) in our centre. Adjusted associations with graft survival were estimated using a multivariable Cox model. The predictive accuracy was estimated using the C-index and net reclassification index. These same analyses were measured in a multicentre validation cohort of 1936 patients.

Results

Both 3-month eGFR_MDRD and proteinuria were independent predictors of return to dialysis (all P < 0.05) and there was a strong correlation between eGFR at 3 and 12 months (Spearman’s ρ = 0.76). The predictive accuracy of the 3-month eGFR was within a similar range and did not differ significantly from the 12-month eGFR in either the derivation cohort [C-index 62.6 (range 57.2–68.1) versus 66.0 (range 60.1–71.9), P = 0.41] or the validation cohort [C-index 69.3 (range 66.4–72.1) versus 71.7 (range 68.7–74.6), P = 0.25].

Conclusion

The 3-month eGFR was a valuable predictor of the long-term return to dialysis whose predictive accuracy was not significantly less than that of the 12-month eGFR in multicentre cohorts totalling >2500 patients. Three-month outcomes may be useful in randomized controlled trials targeting early therapeutic interventions.

Donor cardiac arrest and cardiopulmonary resuscitation: impact on outcomes after simultaneous pancreas-kidney transplantation - a retrospective study

Donor cardiac arrest and cardiopulmonary resuscitation (CACPR) has been considered critically because of concerns over hypoperfusion and mechanical trauma to the donor organs. We retrospectively analyzed 371 first simultaneous pancreas–kidney transplants performed at the Medical University of Innsbruck between 1997 and 2017. We evaluated short‐ and long‐term outcomes from recipients of organs from donors with and without a history of CACPR. A total of 63 recipients received a pancreas and kidney graft from a CACPR donor. At 1, and 5‐years, patient survival was similar with 98.3%, and 96.5% in the CACPR and 97.0%, and 90.2% in the non‐CACPR group (log rank P = 0.652). Death‐censored pancreas graft survival was superior in the CACPR group with 98.3%, and 91.4% compared to 86.3%, and 77.4% (log rank P = 0.028) in the non‐CACPR group, which remained statistically significant even after adjustment [aHR 0.49 (95% CI 0.24–0.98), P = 0.044]. Similar relative risks for postoperative complications Clavien Dindo > 3a, pancreatitis, abscess, immunologic complications, delayed pancreas graft function, and relative length of stay were observed for both groups. Donors with a history of CACPR are, in the current practice, safe for transplantation. Stringent donor selection and short CPR durations may allow for outcomes surpassing those of donors without CACPR.

Renoprotective and Immunomodulatory Effects of GDF15 following AKI Invoked by Ischemia-Reperfusion Injury

BACKGROUND

Gdf15 encodes a TGF-β superfamily member that is rapidly activated in response to stress in multiple organ systems, including the kidney. However, there has been a lack of information about Gdf15 activity and effects in normal kidney and in AKI.

METHODS

We used genome editing to generate a Gdf15 ^nuGFP-CE mouse line, removing Gdf15 at the targeted allele, and enabling direct visualization and genetic modification of Gdf15-expressing cells. We extensively mapped Gdf15 expression in the normal kidney and following bilateral ischemia-reperfusion injury, and quantified and compared renal responses to ischemia-reperfusion injury in the presence and absence of GDF15. In addition, we analyzed single nucleotide polymorphism association data for GDF15 for associations with patient kidney transplant outcomes.

RESULTS

Gdf15 is normally expressed within aquaporin 1-positive cells of the S3 segment of the proximal tubule, aquaporin 1-negative cells of the thin descending limb of the loop of Henle, and principal cells of the collecting system. Gdf15 is rapidly upregulated within a few hours of bilateral ischemia-reperfusion injury at these sites and new sites of proximal tubule injury. Deficiency of Gdf15 exacerbated acute tubular injury and enhanced inflammatory responses. Analysis of clinical transplantation data linked low circulating levels of GDF15 to an increased incidence of biopsy-proven acute rejection.

CONCLUSIONS

Gdf15 contributes to an early acting, renoprotective injury response, modifying immune cell actions. The data support further investigation in clinical model systems of the potential benefit from GDF15 administration in situations in which some level of tubular injury is inevitable, such as following a kidney transplant.

Variable Benefits of Antibody Induction by Kidney Allograft Type

BACKGROUND

Kidneys from acute renal failure (ARF), expanded criteria donors (ECD), and donation after cardiac death (DCD) donors are often discarded due to concerns for delayed graft function (DGF) and graft failure. Induction immunosuppression may be used to minimize these risks, but practices vary widely. Furthermore, little is known regarding national outcomes of transplant recipients receiving induction immunosuppression for receipt of high-risk kidneys.

MATERIALS AND METHODS

Using a center-level retrospective study, deceased donor transplants (115,485) from the Scientific Registry of Transplant Recipients from January 2003 to June 2016 were evaluated. Patients who received induction immunosuppression, including lymphocyte immune globulin, muromonab CD-3, IL-1 receptor antagonist, anti-thymocyte globulin, daclizumab, basiliximab, alemtuzumab, and rituximab, were included. Associations of center-level induction use with acute rejection in the first post-transplant year, graft failure, and patient mortality were evaluated using multivariable Cox and logistic regression.

RESULTS

Among all kidneys, increasing percentage of center-level induction was associated with lower risk of graft failure, acute rejection, and patient mortality. In recipients of ARF kidneys, the beneficial association of induction on graft failure and acute rejection was greater than in those that received non-ARF kidneys. Marginally greater benefit of induction was seen for acute rejection in ECD compared to standard criteria donor (SCD) recipients and for graft failure in DCD compared to donors after brain death (DBD). No benefit of induction was detected for patient and graft survival in ECD recipients, acute rejection in DCD recipients, and patient survival in DGF recipients. No difference in the benefit of induction was detected in any other comparisons.

CONCLUSIONS

While seemingly beneficial for recipients of all kidneys, induction has more robust associations with lower graft failure and acute rejection probability for recipients of ARF kidneys. Given the lack of observed benefit for ECD recipients, induction policies should be carefully considered in these patients.

A Computer Model of Oxygen Dynamics in the Cortex of the Rat Kidney at the Cell-Tissue Level

The renal cortex drives renal function. Hypoxia/reoxygenation are primary factors in ischemia-reperfusion (IR) injuries, but renal oxygenation per se is complex and awaits full elucidation. Few mathematical models address this issue: none captures cortical tissue heterogeneity. Using agent-based modeling, we develop the first model of cortical oxygenation at the cell-tissue level (RCM), based on first principles and careful bibliographical analysis. Entirely parameterized with Rat data, RCM is a morphometrically equivalent 2D-slice of cortical tissue, featuring peritubular capillaries (PTC), tubules and interstitium. It implements hemoglobin/O2 binding-release, oxygen diffusion, and consumption, as well as capillary and tubular flows. Inputs are renal blood flow RBF and PO2 feeds; output is average tissue PO2 (tPO2). After verification and sensitivity analysis, RCM was validated at steady-state (tPO2 37.7 ± 2.2 vs. 36.9 ± 6 mmHg) and under transients (ischemic oxygen half-time: 4.5 ± 2.5 vs. 2.3 ± 0.5 s in situ). Simulations confirm that PO2 is largely independent of RBF, except at low values. They suggest that, at least in the proximal tubule, the luminal flow dominantly contributes to oxygen delivery, while the contribution of capillaries increases under partial ischemia. Before addressing IR-induced injuries, upcoming developments include ATP production, adaptation to minutes-hours scale, and segmental and regional specification.

Clinical relevance of cell-free mitochondrial DNA during the early postoperative period in kidney transplant recipients

Recent studies indicate that urinary mitochondrial DNA (mtDNA) is predictive of ischemic AKI and is related to delayed graft function (DGF) in renal transplantation. Nevertheless, the clinical implications and prognostic value of urinary mtDNA in kidney transplantation remain undetermined. Here, we aimed to evaluate the associations between cell-free mtDNA and clinical parameters, including pathological findings in allograft biopsy and post-transplant renal function. A total of 85 renal transplant recipients were enrolled, and blood and urine samples were collected at a median of 17 days after transplantation. Cell-free nuclear and mtDNA levels were measured by quantitative polymerase chain reaction for LPL and ND1 genes. Urinary cell-free mtDNA levels were significantly higher in patients with DGF (P < 0.001) and cases of deceased donor transplantation (P < 0.001). The subjects with acute rejection showed higher urinary mtDNA levels than those without abnormalities (P = 0.043). In addition, allograft functions at 9- and 12-month post-transplantation were significantly different between tertile groups of mtDNA independent of the presence of DGF or acute rejection, showing significantly better graft outcome in the lowest tertile group. Urinary cell-free mtDNA levels during the early post-transplant period are significantly associated with DGF, acute rejection in graft biopsy, and short-term post-transplant renal function.

Changes in double-strand DNA breaks predict delayed graft function (DGF) in Japanese renal allograft recipients

BACKGROUND

Although delayed graft function (DGF) is a serious complication following kidney transplantation, a reliable and early diagnostic test is lacking to identify the grade of DGF.

METHODS

We investigated changes in double-strand DNA breaks (DSBs), and factors related to DGF, such as ischemic times at transplantation and serum creatinine (sCr) levels. DSBs were detected by phospho-histone H2A.X (γ-H2AX) expression and cellular regeneration by Ki-67 before (0 h) and 1 h after allograft reperfusion (1 h) in each subject.

RESULTS

The expression of γ-H2AX or Ki-67 at 0 h showed no difference between the living and deceased donors. γ-H2AX at 1 h decreased in the living donors, but increased in the deceased donors compared with that of 0 h(p = 0.017). Changes (Δ) in γ-H2AX between 0 and 1 h were different among subgroups, i.e., immediate function, slow graft function with dialysis < 7 days, DGF with dialysis < 4 weeks, severe DGF with dialysis > 4 weeks, or primary non-function (PNF) (p = 0.04). Severe DGF and PNF cases showed greater increase in Δγ-H2AX (p = 0.019), and were distinguished by > 12% of Δγ-H2AX at 100% sensitivity and 88.2% specificity (ROC analysis, AUC: 0.922, p = 0.023). In a multivariate regression analysis, donor sCr and Δγ-H2AX were two main predictors of the grade of DGF (p = 0.002). The expression of Ki-67 was very low at both 0 h and 1 h.

CONCLUSION

The combination of donor sCr and Δγ-H2AX from 0 to 1 h after reperfusion may predict severe DGF and PNF in the early phase.

Donor Urinary C5a Levels Independently Correlate With Posttransplant Delayed Graft Function

BACKGROUND

Accumulating evidence implicates the complement cascade as pathogenically contributing to ischemia-reperfusion injury and delayed graft function (DGF) in human kidney transplant recipients. Building on observations that kidney injury can initiate in the donor before nephrectomy, we tested the hypothesis that anaphylatoxins C3a and C5a in donor urine before transplantation associate with risk of posttransplant injury.

METHODS

We evaluated the effects of C3a and C5a in donor urine on outcomes of 469 deceased donors and their corresponding 902 kidney recipients in a subset of a prospective cohort study.

RESULTS

We found a threefold increase of urinary C5a concentrations in donors with stage 2 and 3 acute kidney injury (AKI) compared donors without AKI (P < 0.001). Donor C5a was higher for the recipients with DGF (defined as dialysis in the first week posttransplant) compared with non-DGF (P = 0.002). In adjusted analyses, C5a remained independently associated with recipient DGF for donors without AKI (relative risk, 1.31; 95% confidence interval, 1.13-1.54). For donors with AKI, however, urinary C5a was not associated with DGF. We observed a trend toward better 12-month allograft function for kidneys from donors with C5a concentrations in the lowest tertile (P = 0.09). Urinary C3a was not associated with donor AKI, recipient DGF, or 12-month allograft function.

CONCLUSIONS

Urinary C5a correlates with the degree of donor AKI. In the absence of clinical donor AKI, donor urinary C5a concentrations associate with recipient DGF, providing a foundation for testing interventions aimed at preventing DGF within this high-risk patient subgroup.

N,N-dimethyltryptamine Prevents Renal Ischemia-Reperfusion Injury in a Rat Model

BACKGROUND

Ischemia reperfusion (I/R) injury remains one of the most challenging fields of organ transplantation. It is highly associated with the use of expanded criteria donors that might conclude to delayed graft function or early or late graft failure.

OBJECTIVE

To investigate the metabolic, microcirculatory parameters, and histologic changes under the effect of N,N-dimethyltryptamine (DMT) in a renal I/R model in rats.

METHOD

In 26 anesthetized rats both kidneys were exposed. In the control group (n = 6) no other intervention happened. In 20 other animals, the right renal vessels were ligated, and after 60 minutes the right kidney was removed. The left renal vessels were clamped for 60 minutes then released, followed by 120 minutes of reperfusion. In the I/R group (n = 10), there was no additive treatment, while in I/R + DMT group (n = 10) DMT was administered 15 minutes before ischemia. Blood samples were taken, laser Doppler measurement was performed, and both kidneys were evaluated histologically.

RESULTS

Microcirculation (blood flux units [BFU]) diminished in all groups, but remarkably so in the I/R + DMT group. This group compensated better after the 30th minute of reperfusion. The control and I/R + DMT groups had similar BFUs after 120 minutes of reperfusion, but in the I/R group BFU was higher. Tubular necrosis developed in the I/R and I/R + DMT groups too; it was moderated under DMT effect, and severe without. Histologic injuries were less in I/R + DMT Group compared to non-treated animals.

CONCLUSION

Histologic changes characteristic to I/R injuries were reversible and microcirculation recovered at the end of 120 minutes reperfusion under the administration of DMT. DMT can be used for renoprotection in kidney transplantation.

Crosstalk Between Connexin32 and Mitochondrial Apoptotic Signaling Pathway Plays a Pivotal Role in Renal Ischemia Reperfusion-Induced Acute Kidney Injury

Aims: Perioperative acute kidney injury (AKI) resulting from renal ischemia reperfusion (IR) is not conducive to the postoperative surgical recovery. Our previous study demonstrated that reactive oxygen species (ROS) transmitted by gap junction (GJ) composed of connexin32 (Cx32) contributed to AKI. However, the precise underlying pathophysiologic mechanisms were largely unknown. This study focuses on the underlying mechanisms related to ROS transmitted by Cx32 responsible for AKI aggravation. Results: In a set of in vivo studies, renal IR was found to cause severe impairment in renal tissues with massive ROS generation, which occurred contemporaneously with activation of NF-κB/p53/p53 upregulated modulator of apoptosis (PUMA)-mediated mitochondrial apoptosis pathways. Cx32 deficiency alleviated renal IR-induced AKI, and simultaneously attenuated ROS generation and distribution in renal tissues, which further inhibited NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathways. Correspondingly, in a set of in vitro studies, hypoxia reoxygenation (HR)-induced cellular injury, and cell apoptosis in both human kidney tubular epithelial cells (HK-2s) and rat kidney tubular epithelial cells (NRK52Es) were significantly attenuated by Cx32 inhibitors or Cx32 gene knockdown. More importantly, Cx32 inhibition not only decreased ROS generation and distribution in human or rat kidney tubular epithelial cells but also inhibited its downstream NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathway activation. Innovation and Conclusion: This is the first identification of the underlying mechanisms of IR-induced renal injury integrally which demonstrates the critical role played by Cx32 in IR-induced AKI. Moreover, GJ composed of Cx32 manipulates ROS generation and distribution between neighboring cells, and alters activation of NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathways. Both inhibiting Cx32 function and scavenging ROS effectively reduce mitochondrial apoptosis and subsequently attenuate AKI, providing effective strategies for kidney protection.

Allograft and patient survival after sequential HSCT and kidney transplantation from the same donor-A multicenter analysis

Tolerance induction through simultaneous hematopoietic stem cell and renal transplantation has shown promising results, but it is hampered by the toxicity of preconditioning therapies and graft-versus-host disease (GVHD). Moreover, renal function has never been compared to conventionally transplanted patients, thus, whether donor-specific tolerance results in improved outcomes remains unanswered. We collected follow-up data of published cases of renal transplantations after hematopoietic stem cell transplantation from the same donor and compared patient and transplant kidney survival as well as function with caliper-matched living-donor renal transplantations from the Austrian dialysis and transplant registry. Overall, 22 tolerant and 20 control patients were included (median observation period 10 years [range 11 months to 26 years]). In the tolerant group, no renal allograft loss was reported, whereas 3 were lost in the control group. Median creatinine levels were 85 μmol/l (interquartile range [IQR] 72-99) in the tolerant cohort and 118 μmol/l (IQR 99-143) in the control group. Mixed linear-model showed around 29% lower average creatinine levels throughout follow-up in the tolerant group (P < .01). Our data clearly show stable renal graft function without long-term immunosuppression for many years, suggesting permanent donor-specific tolerance. Thus sequential transplantation might be an alternative approach for future studies targeting tolerance induction in renal allograft recipients.

Time-intensity curve analysis of contrast-enhanced ultrasound is unable to differentiate renal dysfunction in the early post-transplant period - a prospective study

Background

Contrast enhanced ultrasonography (CEUS) assessment of kidney allografts mainly focuses on graft rejection. However, studies on delayed graft function (DGF) without acute rejection are still lacking. The aim of this study was to build a time-intensity curve (TIC) using CEUS in non-immunological DGF to understand the utility of CEUS in early transplantation.

Methods

Twenty-eight patients in the short-term postoperative period (<14 days) were divided according to the need for dialysis (early graft function [EGF] and [DGF]) and 37 subjects with longer than 90 days follow-up were divided into creatinine tertiles. Time to peak [TTP] and rising time [RT were compared between groups.

Results

EGF and DGF were similar, except for creatinine. In comparison to the late group, medullary TTP and RT were shorter in the early group as well as the delay regarding contrast arrival in the medulla (in relation to cortex) and reaching the medullary peak (in relation to artery and cortex). In the late group, patients with renal dysfunction showed shorter temporal difference to reach medullary peak in relation to artery and cortex.

Conclusions

Although it was not possible to differentiate EGF and DGF using TIC, differences between early and late groups point to blood shunting in renal dysfunction.

Ischemia reperfusion injury in kidney transplantation: A case report

RATIONALE

Kidney transplantation is considered the best treatment for patients with end stage renal disease. Ischemia- reperfusion injury (IRI) is an evitable event after deceased donor transplantation and influences short term and long term graft outcome. Few data on IRI's histology in the setting of kidney transplantation are available in the literature despite its frequency and its severity.

PATIENT CONCERNS

A 64-year-old patient was admitted for his 1st kidney transplantation. There were no pre-existing immunization. The surgery proceeded without complications; with cold ischemia estimated at 37 h 50 min and warm ischemia at 44 min. The immunosuppression protocol was as follows: induction by thymoglobulins, mycophelonate mofetil, corticosteroids. Few hours after transplantation, the patient remained anuric and the biological assessment highlighted in addition to renal failure, hyperlactatemia at 5 mmol/L and a high increase in lactate deshydrogenase (LDH) at 5239 U/L. An abdominopelvic angio-scanner was performed urgently to eliminate the hypothesis of thrombosis of the artery or vein of the graft. A kidney biopsy was performed the day after the transplant and revealed massive lesions of acute tubular necrosis including apoptosis, autophagy-associated cell death, and necrosis. Microvascular dysfunction with increased vascular permeability and endothelial cell inflammation were also present. Activation of coagulation is represented by thrombi in the lumens of the glomerular capillaries.

DIAGNOSIS

The diagnosis was ischemia reperfusion injury responsible for delayed graft function (DGF).

INTERVENTIONS

Immunosuppressive regimen was delayed use of calcineurin inhibitors, mycophenolate mofetil, and corticosteroids.

OUTCOMES

At 1 year post transplant, the patient has a renal autonomy with a graft function stable and physiological proteinuria.

LESSONS

The main clinical consequences of IRI in kidney transplant are DGF, acute and chronic graft rejection, and chronic graft dysfunction. Reducing IRI is one of the most relevant challenge in kidney transplantation.

EPURE Transplant (Eplerenone in Patients Undergoing Renal Transplant) study: study protocol for a randomized controlled trial

BACKGROUND

Despite advances in immunosuppressive therapy, kidney graft survival has failed to improve during the last decades. Ischemia/reperfusion injury (IRI) is one of the main pathophysiological mechanisms underlying delayed graft function, which is associated with poor long-term graft survival. Due to organ shortage, the proportion of grafts from expanded criteria donors (ECDs) is ever growing. These grafts may particularly benefit from IRI prevention. In preclinical models, mineralocorticoid receptor antagonists (MRAs) have been shown to efficiently prevent IRI. This study aims to assess the effect of MRA administration in the early phase of kidney transplantation (KT) among recipients of ECD grafts on mid-term graft function.

METHODS/DESIGN

This is a multicenter, double-blind, placebo-controlled, randomized clinical trial. Patients on hemodialysis and undergoing a single or a dual KT from an ECD will be eligible for inclusion. We plan to randomize 132 patients. Included patients will be randomized (1:1) to receive either eplerenone 25 mg every 12 h during 4 days (the first dose being administered just prior to KT) or placebo. The primary outcome is graft function at 3 months, assessed by glomerular filtration rate (GFR, in mL/min/1.73m²) measured using iohexol clearance. Secondary outcomes include (1) proportion of patients with either dialysis dependency or a GFR < 30 mL/min/1.73m² at 3 months, (2) proportion of patients with immediate, slow, or delayed graft function, (3) proteinuria at 3 months, (4) occurrence of hyperkalemia during the first week following KT, (5) length of hospital stay for the KT, and (6) occurrence of biopsy-proven acute rejection in the first 3 months following KT. Estimated GFR, graft, and patient survival will also be collected at 1, 3, and 10 years via the national database of organ recipients.

DISCUSSION

Improvement of ECD grafts is a public health priority, since better ECD outcomes could eventually limit organ shortage. MRA administration in the early phase of KT may prevent IRI and subsequently improve mid-term graft function. The trial will also assess the safety of MRA administration in this population, primarily the absence of threatening hyperkalemia.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02490904 . Registered on 1 July 2015.