Kidney allograft function and histology in recipients dying with a functioning graft

Increased Pretransplant Inflammatory Biomarkers Predict Death With Function After Kidney Transplantation

BACKGROUND

Chronic systemic inflammation is associated with mortality in patients with chronic kidney disease, cardiovascular disease, and diabetes. The goal of this study was to examine the relationship between pretransplant inflammatory biomarkers (growth differentiation factor-15 [GDF-15], interleukin-6 [IL-6], soluble tumor necrosis factor receptor-1, monokine induced by gamma interferon/chemokine [C-X-C motif] ligand 9 [MIG/CXCL9], monocyte chemoattractant protein-1, soluble FAS, tumor necrosis factor-α, interleukin-15, and interleukin-1β) and death with function (DWF) after kidney transplantation (KT).

METHODS

We retrospectively measured inflammatory biomarker levels in serum collected up to 1 y before KT (time from blood draw to KT was 130 ± 110 d) in recipients transplanted between January 2006 and December 2018. Kaplan-Meier estimation, Cox regression, and Gradient Boosting Machine modeling were used to examine the relationship between inflammatory biomarkers and DWF.

RESULTS

Our cohort consisted of 1595 KT recipients, of whom 62.9% were male and 83.2% were non-Hispanic White. Over a mean follow-up of 7.4 ± 3.9 y, 21.2% of patients (n = 338) experienced DWF. Patients with the highest quartile levels of GDF-15 (>4766 pg/mL), IL-6 (>6.11 pg/mL), and MIG/CXCL9 (> 5835 pg/mL) had increased rates of DWF, and each predicted mortality independently of the others. When adjusted for clinical factors (age, diabetes, etc), the highest quartile levels of GDF-15 and IL-6 remained independently associated with DWF. Adding inflammatory markers to a clinical Cox model improved the C-statistic for DWF from 0.727 to 0.762 using a Gradient Boosting Machine modeling approach.

CONCLUSIONS

These findings suggest that pre-KT serum concentrations of GDF-15, IL-6, and MIG/CXCL9 may help to risk stratify and manage patients undergoing KT and suggests that chronic inflammation may play a role in mortality in KT recipients.

Creatinine-cystatin C ratio and death with a functioning graft in kidney transplant recipients

Death with a functioning graft is important cause of graft loss after kidney transplantation. However, little is known about factors predicting death with a functioning graft among kidney transplant recipients. In this study, we evaluated the association between post-transplant creatinine-cystatin C ratio and death with a functioning graft in 1592 kidney transplant recipients. We divided the patients into tertiles based on sex-specific creatinine-cystatin C ratio. Among the 1592 recipients, 39.5% were female, and 86.1% underwent living-donor kidney transplantation. The cut-off value for the lowest creatinine-cystatin C ratio tertile was 0.86 in males and 0.73 in females. The lowest tertile had a significantly lower 5-year patient survival rate and was independently associated with death with a functioning graft (adjusted hazard ratio 2.574, 95% confidence interval 1.339-4.950, P < 0.001). Infection was the most common cause of death in the lowest tertile group, accounting for 62% of deaths. A low creatinine-cystatin C ratio was significantly associated with an increased risk of death with a functioning graft after kidney transplantation.

Entering the Third Decade After Kidney Transplantation: Excellent Graft Function Refers to Superior Graft but Not Patient Survival

Kidney transplant recipients (KTRs) with ultralong-term survival represent a growing, yet insufficiently studied patient cohort. In this single-center retrospective study, we analyzed 248 ultralong-term survivors (≥20 years). KTRs were classified into those with superior graft function (defined as eGFR ≥45 ml/min + proteinuria ≤300 mg/day + eGFR-slope ≤ 2 ml/min/1.73 m2/year) and inferior graft function regarding the risk of CKD progression. 20 years post-transplant, median eGFR was 54 ml/min (11-114), proteinuria 200 mg/24 h (0-7,620), eGFR decline 0.45 ml/min/1.73 m2/year (11.7 6.5) and DSA had been detected in 19.7% of KTRs. We identified 96 KTRs (38.7%) with superior (group 1) and 152 KTRs (61.3%) with inferior graft function (group 2). Donation after cardiac death, female sex, glomerulonephritis as primary disease, and early TCMR were independently associated with inferior graft function. Graft survival was significantly better in group 1 compared to group 2 (LogRank, p < 0.001). Besides group affiliation (HR 20.515, p = 0.003), multivariable analysis identified DSA development (HR 3.081, p = 0.023) and donor age (HR 1.032, p = 0.024) as independent factors. Interestingly, there was no significant difference in patient survival (LogRank, p = 0.350). In ultralong-term survivors, excellent graft function refers to superior graft survival but does not extend ultimate patient survival. DSA-formation should be taken seriously even in the ultralong-term.

Late Graft Loss After Kidney Transplantation: Is "Death With Function" Really Death With a Functioning Allograft?

BACKGROUND

About half of late kidney allograft losses are attributed to death with function (DWF), a poorly characterized outcome. An ongoing question is whether DWF is a consequence of chronic allograft dysfunction. Using the prospective Long-term Deterioration of Kidney Allograft Function study database, we sought to better define the impact, phenotype, and clinical course of DWF in the current era.

METHODS

Three thousand five hundred eighty-seven kidney recipients with functional grafts at 90 days post-transplant were followed prospectively for a median of 5.2 years.

RESULTS

Characteristics at transplantation in those with DWF (N = 350, 9.8%) differed from those who otherwise lost their grafts (death-censored graft failure [DC-GF], N = 295, 8.2%) or maintained function (N = 2942, 82.0%); DWF patients were older, sicker, and had been on dialysis longer, with more preexisting cardiovascular disease, whereas DC-GF patients experienced more early rejection, more acute rejection after 90 days, and a clinically significant decrease in kidney function before graft failure. In contrast, the clinical course after transplantation in DWF patients did not differ before death from those who maintained function throughout.

CONCLUSIONS

DWF and DC-GF in kidney transplant recipients represent differing clinical phenotypes occurring in distinct patient populations. Reducing the impact of DWF requires better definition of causes and clinical course and then trials of therapies to improve outcomes. Composite endpoints in clinical trials that group DWF and DC-GF together may obscure important clinical findings.

Expression Profiling of Exosomal miRNAs Derived from the Peripheral Blood of Kidney Recipients with DGF Using High-Throughput Sequencing

Delayed graft function (DGF) is one of the major obstacles for graft survival for kidney recipients. It is profound to reduce the incidence of DGF for maintaining long-term graft survival. However, the molecular regulation of DGF is still not adequately explained and the biomarkers for DGF are limited. Exosomes are cell-derived membrane vesicles, contents of which are stable and could be delivered into recipient cells to exert their biological functions. Consequently, exosome-derived proteomic and RNA signature profiles are often used to account for the molecular regulation of diseases or reflect the conditional state of their tissue as biomarkers. Few researches have been done to demonstrate the function of exosomes associated with DGF. In this study, high-throughput sequencing was used to explore the miRNA expression profiling of exosomes in the peripheral blood of kidney recipients with DGF. We identified 52 known and 5 conserved exosomal miRNAs specifically expressed in recipients with DGF. Three coexpressed miRNAs, hsa-miR-33a-5p_R-1, hsa-miR-98-5p, and hsa-miR-151a-5p, were observed to be significantly upregulated in kidney recipients with DGF. Moreover, hsa-miR-151a-5p was positively correlated with the first-week serum CR, BUN, and UA levels of the kidney recipients after transplantation. Furthermore, we also analyzed functions and signaling pathways of the three upregulated miRNAs target genes to uncover putative mechanism of how these exosomal miRNAs functioned in DGF. Overall, these findings identified biomarker candidates for DGF and provided new insights into the important role of the exosomal miRNAs regulation in DGF.

Interleukin-33 levels are elevated in chronic allograft dysfunction of kidney transplant recipients and promotes epithelial to mesenchymal transition of human kidney (HK-2) cells

This study is aimed to investigate the potential role of interleukin (IL)-33 in transplanted kidney interstitial fibrosis and the associated mechanism. Serum IL-33 levels were detected using an enzyme-linked immunosorbent assay (ELISA) in healthy volunteers, stable kidney transplantation recipients (KTRs) (stable), KTRs with acute rejection (AR), and KTRs with chronic allograft dysfunction (CAD) (CAD). Immunohistochemical (IHC) staining, Western blotting, and quantitative real-time PCR (qRT-PCR) were used to detect the expression of IL-33 in human kidney tissues obtained from control and CAD patients. In addition, human kidney (HK)-2 cells were treated with human IL-33 at different doses or intervals, and the markers of epithelial to mesenchymal transition (EMT) were assessed by the presence of proteins and mRNA extracted from these cells using Western blotting and qRT-PCR. Cell motility and migration were evaluated with a cell motility and migration assay. The mechanism involved in EMT induced by IL-33 was investigated by Western blot. Finally, fibronectin, E-cadherin, and α-SMA expression, as well as the level of activity in the MAPK signaling pathway in the kidney tissues from the control and CAD group were also detected using a Western blot and an IHC staining assay. The intensity of fibrosis was substantially higher in the CAD group. IL-33 was significantly upregulated in the CAD patients compared to the control group. In vitro, IL-33 could induce EMT in a dose-dependent and time-dependent manner and promoted both the cellular motility and migration capabilities of HK-2 cells. Moreover, the p38 MAPK signaling pathway might be involved in the pathogenesis of EMT induced by IL-33, which was consistent with the in vivo results of the kidney specimens from the control and CAD patients. IL-33 was upregulated in CAD patients and could promote EMT of HK-2 cells.

Predicting Individual Renal Allograft Outcomes Using Risk Models with 1-Year Surveillance Biopsy and Alloantibody Data

The ability to predict outcomes for individual patients would be a significant advance for not only counseling, but also identifying those for whom interventions may be needed. The goals of this study were to validate an existing risk prediction score that incorporates easily obtainable clinical factors and determine if histologic findings at 1-year surveillance biopsy and/or serum donor-specific alloantibody status could improve predictability of graft loss by 5 years. We retrospectively studied 1465 adults who received a solitary kidney transplant between January of 1999 and December of 2008 and had sufficiently detailed 5-year follow-up data for modeling. In this cohort, the Birmingham risk model (incorporating recipient factors at 1 year, including age, sex, ethnicity, renal function, proteinuria, and prior acute rejection) predicted death-censored and overall graft survival (c statistics =0.84 and 0.78, respectively). The presence of glomerulitis or chronic interstitial fibrosis (g and ci scores by Banff, respectively) on 1-year biopsy specimens independently correlated with graft loss by 5 years. Adding these variables to the model for death-censored graft loss increased predictability (c statistic =0.90), improved calibration (ability to stratify risk from high to low), and reclassified risk of failure in 29% of patients. Adding the presence of donor-specific alloantibody at 1 year did not improve predictability or reclassification but did improve calibration marginally. We conclude that, at 1 year after kidney transplant, a risk model of graft survival that incorporates clinical factors and histologic findings at surveillance biopsy is highly predictive of individual risk and well calibrated.