Jeffrey Damman

Local renal complement C3 induction by donor brain death is associated with reduced renal allograft function after transplantation

BACKGROUND Kidneys derived from brain-dead donors have inferior outcomes after transplantation compared to kidneys from living donors. Strikingly, early and profound serum levels of IL-6 in brain-dead donors are observed. IL-6 is the main regulator of the acute phase response (APR). The aim of this translational study was to investigate the expression of renal acute phase proteins (APPs) following brain death (BD) and to assess the association with renal allograft outcome after transplantation. METHODS BD was induced in rats by inflating a subdurally placed balloon catheter. Kidney biopsies were obtained from human living and brain-dead donors at donation, after cold preservation and reperfusion. In vitro, renal proximal tubular epithelial cells (HK-2 cells) were stimulated with IL-6. RESULTS Both in human and rat brain-dead donors, C3 and FBG expression was enhanced at donation compared to living donors and sham-operated animals. In human donors, no additional expression was found after cold ischaemia or reperfusion. C3 expression after reperfusion was independently associated with decreased short-term function after transplantation in grafts from brain-dead donors. In cultured HK-2 cells, C3 production was induced in the presence of IL-6. CONCLUSIONS In conclusion, BD induces renal C3 and FBG expression. Moreover, C3 expression is associated with a worse allograft function early after transplantation. Therefore, targeting renal APPs in brain-dead donors, especially complement C3, may improve transplant outcome.

Crosstalk between Complement and Toll‐like Receptor Activation in Relation to Donor Brain Death and Renal Ischemia‐Reperfusion Injury

Two central pathways of innate immunity, complement and Toll‐like receptors (TLRs), play an important role in the pathogenesis of renal injury inherent to kidney transplantation. Recent findings indicate close crosstalk between complement and TLR signaling pathways. It is suggested that mitogen activated protein kinases (MAPKs) might be the key molecules linking both the complement and TLR pathways together. Complement and TLRs are important mediators of renal ischemia‐reperfusion injury (IRI). Besides IRI, complement C3 can also be upregulated and activated in the kidney before transplantation as a direct result of brain death (BD) in the donor. This local upregulation and activation of complement in the donor kidney has been proven to be detrimental for renal allograft outcome. Also TLR4 and several of its major ligands are upregulated by donor BD compared to living donors. Important and in line with the observations above, kidney transplant recipients have a benefit when receiving a kidney from a TLR4 Asp299Gly/Thr399Ile genotypic donor. The role of complement and TLRs and crosstalk between these two innate immune systems in relation to renal injury during donor BD and ischemia‐reperfusion are focus of this review. Future strategies to target complement and TLR activation in kidney transplantation are considered.

Systemic complement activation in deceased donors is associated with acute rejection after renal transplantation in the recipient.

Background. Acute rejection after renal transplantation has been shown to be negatively associated with long-term graft survival. Identifying donor factors that are associated with acute rejection in the recipient could help to a better understanding of the relevant underlying processes that lead to graft injury. Complement activation has been shown to be an important mediator of renal transplant related injury. In this study, we analyzed the effect of systemic complement activation in deceased donors before transplantation of their kidneys on posttransplant outcome in the recipient. Methods. Plasma from 232 deceased brain-dead and deceased cardiac-dead donors were analyzed for the complement activation markers C5b-9, C4d, Bb, and complement component mannan binding lectin by ELISA. The association of these parameters with posttransplant outcome in recipients was analyzed in a multivariate regression model. Results. It was found that C5b-9 level in donor plasma is associated with biopsy-proven acute rejection in the recipient during the first year after renal transplantation (P=0.035). Both in deceased brain-dead and deceased cardiac-dead donors increased complement activation was found. Conclusions. In conclusion, we found C5b-9 in the donor to be associated with acute rejection of renal transplants in the recipient. Whether targeting complement activation in the donor may ameliorate acute rejection in the recipient needs to be studied.

Complement mediated renal inflammation induced by donor brain death : role of renal C5a-C5aR interaction

Kidneys retrieved from brain‐dead donors have impaired allograft function after transplantation compared to kidneys from living donors. Donor brain death (BD) triggers inflammatory responses, including both systemic and local complement activation. The mechanism by which systemic activated complement contributes to allograft injury remains to be elucidated. The aim of this study was to investigate systemic C5a release after BD in human donors and direct effects of C5a on human renal tissue. C5a levels were measured in plasma from living and brain‐dead donors. Renal C5aR gene and protein expression in living and brain‐dead donors was investigated in renal pretransplantation biopsies. The direct effect of C5a on human renal tissue was investigated by stimulating human kidney slices with C5a using a newly developed precision‐cut method. Elevated C5a levels were found in plasma from brain‐dead donors in concert with induced C5aR expression in donor kidney biopsies. Exposure of precision‐cut human kidney slices to C5a induced gene expression of pro‐inflammatory cytokines IL‐1 beta, IL‐6 and IL‐8. In conclusion, these findings suggest that systemic generation of C5a mediates renal inflammation in brain‐dead donor grafts via tubular C5a‐C5aR interaction. This study also introduces a novel in vitro technique to analyze renal cells in their biological environment.

Complement and renal transplantation: from donor to recipient.

Long-term kidney graft survival is affected by different variables including donor condition, ischemia-reperfusion injury, and graft rejection during the transplantation process. The complement system is an important mediator of renal ischemia-reperfusion injury and in rejecting allografts. However, donor complement C3 seems to be crucial in renal transplantation-related injury as renal injury is attenuated in C3 deficient kidney grafts. Interestingly, before ischemia-reperfusion induced C3 expression, C3 is already induced in donors suffering from brain death. Therefore, strategies targeting complement activation in the brain-dead donor may increase graft viability and transplant outcome.

Targeting complement activation in brain-dead donors improves renal function after transplantation.

Kidneys recovered from brain-dead donors have inferior outcomes after transplantation compared to kidneys from living donors. Since complement activation plays an important role in renal transplant related injury, targeting complement activation in brain-dead donors might improve renal function after transplantation. Brain death (BD) was induced in Fisher rats by inflation of an epidurally placed balloon catheter and ventilated for 6h. BD animals were treated with soluble complement receptor 1 (sCR1) 1h before or 1h after BD. Kidney transplantation was performed and 7 days after transplantation animals were sacrificed. Plasma creatinine and urea were measured at days 0, 1, 3, 5 and 7 after transplantation. Renal function was significantly better at day 1 after transplantation in recipients receiving a sCR1 pre-treated donor kidney compared to recipients of a non-treated donor graft. Also treatment with sCR1, 1h after the diagnosis of BD, resulted in a better renal function after transplantation. Gene expression of IL-6, IL-1beta and TGF-beta were significantly lower in renal allografts recovered from treated donors. This study shows that targeting complement activation, during BD in the donor, leads to an improved renal function after transplantation in the recipient.

Kidney Injury Molecule-1 is an Early Noninvasive Indicator for Donor Brain Death-Induced Injury Prior to Kidney Transplantation

With more marginal deceased donors affecting graft viability, there is a need for specific parameters to assess kidney graft quality at the time of organ procurement in the deceased donor. Recently, kidney injury molecule‐1 (Kim‐1) was described as an early biomarker of renal proximal tubular damage. We assessed Kim‐1 in a small animal brain death model as an early and noninvasive marker for donor‐derived injury related to brain death and its sequelae, with subsequent confirmation in human donors.

Hypoxia and Complement-and-Coagulation Pathways in the Deceased Organ Donor as the Major Target for Intervention to Improve Renal Allograft Outcome.

Background In the last few decades, strategies to improve allograft survival after kidney transplantation have been directed to recipient-dependent mechanisms of renal injury. In contrast, no such efforts have been made to optimize organ quality in the donor. Optimizing deceased donor kidney quality opens new possibilities to improve renal allograft outcome. Methods A total of 554 kidney biopsies were taken from donation after brain death (DBD) and donation after cardiac death (DCD) kidneys before donation, after cold ischemia and after reperfusion. Healthy living donor kidney biopsies served as controls. Transcriptomics was performed by whole genome microarray analyses followed by functional pathway analyses. Results Before organ retrieval and before cessation of blood circulation, metabolic pathways related to hypoxia and complement-and-coagulation cascades were the major pathways enhanced in DBD donors. Similar pathways were also enriched in DCD donors after the first warm ischemia time. Shortly after reperfusion of DCD grafts, pathways related to prolonged and worsening deprivation of oxygen were associated with delayed graft function in the recipient. Conclusion In conclusion, this large deceased donor study shows enrichment of hypoxia and complement-and-coagulation pathways already in DBD donors before cessation of blood flow, before organ retrieval. Therefore, future intervention therapies should target hypoxia and complement-and-coagulation cascades in the donor to improve renal allograft outcome in the recipient.

Acute but transient release of terminal complement complex after reperfusion in clinical kidney transplantation.

Background Ischemia/reperfusion (I/R) injury has a major impact on kidney graft function and survival. Animal studies have suggested a role for complement activation in mediating I/R injury; however, results are not unambiguous. Whether complement activation is involved in clinical I/R injury in humans is still unclear. Methods In the present study, we assessed the formation and release of C5b-9 during early reperfusion in clinical kidney transplantation in living donor, brain-dead donor, and cardiac dead donor kidney transplantation. By arteriovenous measurements and histologic studies, local terminal complement activation in the reperfused kidney was assessed. Results There was no release of soluble C5b-9 (sC5b-9) from living donor kidneys, nor was there a release of C5a. In contrast, instantly after reperfusion, there was a significant but transient venous release of sC5b-9 from the reperfused kidney graft in brain-dead donor and cardiac dead donor kidney transplantation. This short-term activation of the terminal complement cascade in deceased-donor kidney transplantation was not reflected by renal tissue deposition of C5b-9 in biopsies taken 45 min after reperfusion. Conclusions This systematic study in human kidney transplantation shows an acute but nonsustained sC5b-9 release on reperfusion in deceased-donor kidney transplantation. This instantaneous, intravascular terminal complement activation may be induced by intravascular cellular debris and hypoxic or injured endothelium.

UMOD as a susceptibility gene for end-stage renal disease

BackgroundIn recent genetic association studies, common variants including rs12917707 in the UMOD locus have shown strong evidence of association with eGFR, prevalent and incident chronic kidney disease and uromodulin urinary concentration in general population cohorts. The association of rs12917707 with end-stage renal disease (ESRD) in a recent case-control study was only nominally significant.MethodsTo investigate whether rs12917707 associates with ESRD, graft failure (GF) and urinary uromodulin levels in an independent cohort, we genotyped 1142 ESRD patients receiving a renal transplantation and 1184 kidney donors as controls. After transplantation, 1066 renal transplant recipients were followed up for GF. Urinary uromodulin concentration was measured at median [IQR] 4.2 [2.2-6.1] yrs after kidney transplantation.ResultsThe rs12917707 minor allele showed association with lower risk of ESRD (OR 0.89 [0.76-1.03], p = 0.04) consistent in effect size and direction with the previous report (Böger et al, PLoS Genet 2011). Meta-analysis of these findings showed significant association of rs12917707 with ESRD (OR 0.91 [0.85-98], p = 0.008). In contrast, rs12917707 was not associated with incidence of GF. Urinary uromodulin concentration was lower in recipients-carriers of the donor rs12917707 minor allele as compared to non-carriers, again consistent with previous observations in general population cohorts.ConclusionsOur study thus corroborates earlier evidence and independently confirms the association between UMOD and ESRD.