Because older donor age is a major concern when considering kidneys for potential transplantation, we explored the actual effect of donor age on the features of kidneys that have been transplanted. We studied the correlations of donor age with molecular injury and rejection scores in 4,502 kidney transplant biopsies assessed by microarrays as well as function and postbiopsy survival. We used multivariable analyses to correct for the correlations of donor age with other predictive variables: recipient age, time of biopsy after transplant, and deceased versus living donors. Older donor age correlated with lower glomerular filtration rate (GFR) and increased acute and chronic injury transcripts but had no effect on rejection, which was anticorrelated with recipient age. Acute injury transcripts peaked immediately after transplant and regressed. Older donor age had little effect on acute molecular injury immediately after transplant but strongly increased molecular injury scores at later times, peaking about 1-year after transplant, indicating that older age does not increase molecular injury but increases failed repair after injury. As expected, older donor age correlated with increased chronic injury and lower GFR, evident from the earliest time after transplant, pretransplant aging. However, despite substantial age-related effects, the quantitative contribution of donor aging to molecular injury, function, and survival was very small.

Urine proteomics and extracellular vesicle (EV) research have emerged as promising fields for biomarker discovery. While urine protein concentration is known to influence proteomics and EV isolation, its effect on both of these combined remains unclear. This study compares proteomic signatures between neat urine and EV-enriched urine in two protein concentration groups (≤0.50 and >0.5 g/L) using two EV enrichment methods. Data-independent acquisition (DIA) was employed for mass spectrometry (MS) proteomic analysis. At low-protein concentrations, neat urine yielded a richer proteome, identifying more proteins, including EV-associated proteins, compared to enriched urine. At high-protein concentrations, neat urine showed reduced protein identification, while enrichment improved the detection of unique proteins and decreased the relative abundance of high-abundance proteins. These findings suggest that, based on (MS)-based proteomics with DIA (DIA-MS), neat urine is a superior source of potential biomarkers at low-protein concentrations, whereas at high-protein concentrations, EV enrichment effectively standardizes signatures for better proteome detection. This study highlights the impact of urine protein concentration on discovery proteomics and the importance of tailoring methodologies to different sample characteristics in biomarker discovery.

BACKGROUND:Expression of acute kidney injury-associated (AKI-associated) transcripts in kidney transplants may reflect recent injury and accumulation of epithelial cells in "failed repair" states. We hypothesized that the phenomenon of failed repair could be associated with deterioration and failure in kidney transplants. METHODS:We defined injury-induced transcriptome states in 4,502 kidney transplant biopsies injury-induced gene sets and classifiers previously developed in transplants. RESULTS:In principal component analysis (PCA), PC1 correlated with both acute and chronic kidney injury and related inflammation and PC2 with time posttransplant. Positive PC3 was a dimension that correlated with epithelial remodeling pathways and anticorrelated with inflammation. Both PC1 and PC3 correlated with reduced survival, with PC1 effects strongly increasing over time whereas PC3 effects were independent of time. In this model, we studied the expression of 12 "new" gene sets annotated in single-nucleus RNA-sequencing studies of epithelial cells with failed repair in native kidneys. The new gene sets reflecting epithelial-mesenchymal transition correlated with injury PC1 and PC3, lower estimated glomerular filtration rate, higher donor age, and future failure as strongly as any gene sets previously derived in transplants and were independent of nephron segment of origin and graft rejection. CONCLUSION:These results suggest 2 dimensions in the kidney transplant response to injury: PC1, AKI-induced changes, failed repair, and inflammation; and PC3, a response involving epithelial remodeling without inflammation. Increasing kidney age amplifies PC1 and PC3. TRIAL REGISTRATION:INTERCOMEX (ClinicalTrials.gov NCT01299168); Trifecta-Kidney (ClinicalTrials.gov NCT04239703). FUNDING:Genome Canada; Natera, Inc.; and Thermo Fisher Scientific.

Background:Posttransplant immunosuppression in kidney transplant recipients is associated with an increased risk of developing cutaneous squamous cell carcinoma (CSCC), contributing to significant morbidity and mortality. Various dermatological and immunosuppression modulation strategies have been identified that may reduce the risk of CSCC, both in primary and secondary prevention settings. Recent recommendations have provided consensus regarding dermatological approaches to prevent CSCC. Comparable transplant nephrology recommendations to guide immunosuppression modulation for CSCC prevention are currently lacking, leading to marked variation in practice. Methods:To address this knowledge gap, 46 international transplant nephrology experts participated in a 3-round Delphi survey to develop consensus recommendations for CSCC secondary prevention based on the actinic damage and skin cancer index stages of CSCC. Results:The panel of experts reached consensus to consider a change in immunosuppression after multiple low-risk invasive CSCC (stage 5a, 1/y >3 y) and encouraged collaboration with dermatology to optimize dermatologic preventative care after the first CSCC. There was also consensus to prioritize azathioprine modification where this is present in an immunosuppressive regimen. Conclusions:This study provides the first international consensus recommendations for management of immunosuppression in kidney transplant recipients at discrete stages of CSCC. Additional prospective studies are necessary to determine the optimal management of immunosuppression in this patient population. These recommendations have been endorsed by the Board of the American Society of Transplantation.

Emerging treatments for antibody-mediated rejection (ABMR, NEJM391 (2):122-132) have increased the importance of ABMR detection when donor-specific antibody (DSA) is negative. We addressed this issue in the Trifecta-Kidney study (ClinicalTrials.gov #NCT04239703) using 3 centralized tests in 690 kidney transplant biopsies: DSA (One Lambda Inc), blood donor-derived cell-free DNA (dd-cfDNA, Prospera™ test, Natera, Inc), and molecular biopsy assessment (MMDx). We used an "AutoBanff 2022" algorithm to model the impact of alternative DSA interpretations on the histologic diagnosis of DSA-negative ABMR following Banff guidelines, including agreement with dd-cfDNA and molecular ABMR. Lowering MFI cutoffs for DSA positivity did not improve the detection of DSA-negative ABMR. However, simply calling all DSA as positive allowed the Banff 2022 guidelines to identify 46% more ABMR cases with no measurable conventional DSA, and per net reclassification improvement increased agreement between histologic diagnoses and both dd-cfDNA (P = 7.72E-7) and molecular ABMR (P = 7.69E-7). New ABMR cases were as strongly positive for dd-cfDNA and molecular ABMR as those found using the conventional DSA interpretation. A validation set analysis using INTERCOMEX study data (ClinicalTrials.gov NCT#01299168) confirmed these findings and found that the new DSA-negative ABMR cases identified by calling all DSA-positive had the same risk for graft loss as those found with conventional DSA interpretation. Trifecta-Kidney Study ClinicalTrials.gov #NCT04239703.

BACKGROUND:The identification of individuals who will benefit most from kidney transplantation is challenging, with no clear consensus as to which clinical features provide the most prognostic information. Recently, computed tomography (CT)-diagnosed sarcopenia has proven to be accurate in predicting poorer outcomes solid organ transplant recipients. This systematic review and meta-analysis evaluates the role of sarcopenia, as defined by preoperative CT, in the prediction of postoperative recipient and allograft outcomes in patients undergoing kidney transplantation. METHODS:A comprehensive literature search was performed on Medline, Embase, Google Scholar and CINAHL databases. Seven articles involving 1153 patients were included in this review. RESULTS:There was strong evidence to suggest that CT-defined sarcopenia was associated with increased mortality (OR: 2.72, 95% CI, 1.66-4.47, P < .0001) and greater likelihood of readmission (OR: 1.98, 95% CI, 1.34-2.92, P = .00006). There was a lack of evidence to support the use of preoperative CT to define sarcopenia as a prognostic factor for allograft and other postoperative outcomes following kidney transplantation. CONCLUSIONS:This systematic review and meta-analysis demonstrates evidence to suggest pretransplant sarcopenia identified on CT imaging is predictive of increased mortality and readmission. Given the limitations of evidence related to risk of bias and heterogeneity, there is a need for more robust prospective research to elucidate the true effect of CT diagnosed sarcopenia as a prognostic factor in the kidney transplant setting.

BackgroundCytomegalovirus (CMV) causes significant morbidity and mortality following kidney transplantation. Late CMV infection (≥2 years post-transplant) is uncommon, and its risk factors and outcomes may differ from earlier infection.MethodsWe conducted a single-centre retrospective study of kidney transplant recipients between 2009 and 2019. Patients were grouped by CMV status: no infection, early infection (<2 years post-transplant), and late infection (≥2 years post-transplant). Clinical characteristics and outcomes were compared.ResultsDonor-positive/recipient-negative (D+/R−) serostatus was observed in 105/710 (14.8%) patients without CMV, 28/42 (66.7%) with early CMV, and 2/28 (7.1%) with late CMV (p < 0.001). Prior rejection occurred in 5.9%, 16.7%, and 10.7% respectively (p = 0.017). Median serum creatinine was 113.0, 127.5, and 219.5 µmol/L respectively (p < 0.001). CMV serostatus was significantly associated with early infection (p < 0.001), while only serum creatinine was associated with late infection (p = 0.003). Trends were seen toward better one-year patient survival (97.6% vs. 85.7%, p = 0.051) and graft survival (88.1% vs. 71.4%, p = 0.073) after early vs. late infection.ConclusionsRisk factors for CMV infection differ by timing post-transplant. Renal dysfunction may be a key predictor of late infection. identifying at-risk patients may support targeted surveillance and improve long-term outcomes.

BACKGROUND:Antibody-mediated rejection (ABMR) poses a barrier to long-term graft survival and is one of the most challenging events after kidney transplantation. Removing donor specific antibodies (DSA) through therapeutic plasma exchange (PLEX) is a cornerstone of antibody depletion but has inconsistent effects. Imlifidase is a treatment currently utilized for desensitization with near-complete inactivation of DSA both in the intra- and extravascular space. METHODS:This was a 6-month, randomized, open-label, multicenter, multinational trial conducted at 14 transplant centers. Thirty patients were randomized to either imlifidase or PLEX treatment. The primary endpoint was reduction in DSA level during the 5 days following the start of treatment. RESULTS:Despite considerable heterogeneity in the trial population, DSA reduction as defined by the primary endpoint was 97% for imlifidase compared to 42% for PLEX. Additionally, imlifidase reduced DSA to noncomplement fixing levels, whereas PLEX failed to do so. After antibody rebound in the imlifidase arm (circa days 6-12), both arms had similar reductions in DSA. Five allograft losses occurred during the 6 months following the start of ABMR treatment-four within the imlifidase arm (18 patients treated) and one in the PLEX arm (10 patients treated). In terms of clinical efficacy, the Kaplan-Meier estimated graft survival was 78% for imlifidase and 89% for PLEX, with a slightly higher eGFR in the PLEX arm at the end of the trial. The observed adverse events in the trial were as expected, and there were no apparent differences between the arms. CONCLUSION:Imlifidase was safe and well-tolerated in the ABMR population. Despite meeting the primary endpoint of maximum DSA reduction compared to PLEX, the trial was unsuccessful in demonstrating a clinical benefit of imlifidase in this heterogenous ABMR population. TRIAL REGISTRATION:EudraCT number: 2018-000022-66, 2020-004777-49; ClinicalTrials.gov identifier: NCT03897205, NCT04711850.

AIM:Determining specific causes of allograft failure allows a focus on understanding and treating these conditions. Previous studies highlight chronic antibody-mediated rejection as a leading cause of late allograft failure. We sought to define causes of allograft failure in a large cohort of kidney transplant recipients across multiple centres in Australia and New Zealand, including cases previously attributed to chronic allograft nephropathy (CAN). METHODS:All death-censored allograft failures at 9 participating centres between 1 January 2014 to 31 December 2018 were included. Available clinical and biopsy data were reviewed and the "most likely" cause assigned. RESULTS:There were 642 death-censored allograft failures in the study period. Of these, 495 (77.1%) had an informative biopsy performed a median of 13.4 months (IQR 2.5-39.1 months) prior to allograft failure. Rejection of any type was the leading cause of allograft failure (47.5%), comprised chiefly of chronic antibody-mediated rejection (37.4%) and chronic T-cell mediated rejection (6.4%). Other leading causes were undifferentiated interstitial fibrosis and tubular atrophy (10.8%), late medical and surgical complications (8.1%) and recurrent or de novo glomerulonephritis (7.0%). Polyoma viral nephropathy and calcineurin inhibitor toxicity each contributed to <2%. Causes of allograft failure previously attributed to CAN (n = 419, 65.3%) had a similar distribution to the overall cohort, with 43.9% attributed to chronic antibody-mediated rejection. CONCLUSION:To prolong allograft survival, improved strategies are needed to curtail alloimmune responses. Greater understanding of the causes of undifferentiated interstitial fibrosis and tubular atrophy and potential treatments would also be of considerable benefit.

Most kidney transplant patients who undergo biopsies are classified as having no rejection based on consensus thresholds. However, we hypothesized that because these patients have normal adaptive immune systems, T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR) may exist as subthreshold activity in some transplants currently classified as no rejection. To examine this question, we studied genome-wide microarray results from 5086 kidney transplant biopsies (from 4170 patients). An updated molecular archetypal analysis designated 56% of biopsies as no rejection. Subthreshold molecular TCMR and/or ABMR activity molecular activity was detectable as elevated classifier scores in many biopsies classified as no rejection, with ABMR activity in many TCMR biopsies and TCMR activity in many ABMR biopsies. In biopsies classified as no rejection histologically and molecularly, molecular TCMR classifier scores correlated with increases in histologic TCMR features and molecular injury, lower estimated glomerular filtration rate, and higher risk of graft loss, and molecular ABMR activity correlated with increased glomerulitis and donor-specific antibody. No rejection biopsies with high subthreshold TCMR or ABMR activity had a higher probability of having TCMR or ABMR, respectively, diagnosed in a future biopsy. We conclude that many kidney transplant recipients have unrecognized subthreshold TCMR or ABMR activity, with significant implications for future problems.

Background. The reporting of a locally validated kidney donor profile index (KDPI) began in Australia in 2016. Across diverse populations, KDPI has demonstrated utility in predicting allograft survival and function. A metric that incorporates both elements may provide a more comprehensive picture of suboptimal recipient outcomes. Methods. A retrospective cohort study of adult kidney transplant recipients in Australia (January 2009 to December 2014) was conducted. Conventional recipient outcomes and a composite measure of suboptimal outcome (1-y allograft failure or estimated glomerular filtration rate [eGFR] <30 mL/min) were evaluated across KDPI intervals (KDPI quintiles and 5-point increments in the KDPI 81–100 cohort). The impact of increasing KDPI on allograft function (1-y eGFR) and a suboptimal outcome was explored using multivariable regression models, adjusting for potential confounding factors. Results. In 2923 donor kidneys eligible for analysis, median KDPI was 54 (interquartile range [IQR], 31–77), and Kidney Donor Risk Index was 1.39 (IQR, 1.03–1.67). The median 1-y eGFR was 52.74 mL/min (IQR, 40.79–66.41 mL/min). Compared with the first quintile reference group, progressive reductions in eGFR were observed with increasing KDPI and were maximal in the fifth quintile (adjusted β-coefficient: −27.43 mL/min; 95% confidence interval, –29.44 to –25.42; P < 0.001). A suboptimal outcome was observed in 359 recipients (12.3%). The adjusted odds for this outcome increased across quintiles from a baseline of odds ratio of 1.00 (first quintile) to odds ratio of 11.68 (95% confidence interval, 6.33-21.54, P < 0.001) in the fifth quintile cohort. Conclusions. Increases in donor KDPI were associated with higher probabilities of a suboptimal outcome and poorer baseline allograft function, particularly in the KDPI > 80 cohort. These findings may inform pretransplant discussions with potential recipients of high-KDPI allografts.