Rationale and Design of a Phase 2, Double-blind, Placebo-Controlled, Randomized Trial Evaluating AMP Kinase-Activation by Metformin in Focal Segmental Glomerulosclerosis

Introduction

Focal segmental glomerulosclerosis (FSGS), the most common primary glomerular disease leading to end-stage kidney disease (ESKD), is characterized by podocyte injury and depletion, whereas minimal change disease (MCD) has better outcomes despite podocyte injury. Identifying mechanisms capable of preventing podocytopenia during injury could transform FSGS to an "MCD-like" state. Preclinical data have reported conversion of an MCD-like injury to one with podocytopenia and FSGS by inhibition of AMP-kinase (AMPK) in podocytes. Conversely, in FSGS, AMPK-activation using metformin (MF) mitigated podocytopenia and azotemia. Observational studies also support beneficial effects of MF on proteinuria and chronic kidney disease (CKD) outcomes in diabetes. A randomized controlled trial (RCT) to test MF in podocyte injury with FSGS has not yet been conducted.

Methods

We report the rationale and design of phase 2, double-blind, placebo-controlled RCT evaluating the efficacy and safety of MF as adjunctive therapy in FSGS. By randomizing 30 patients with biopsy-confirmed FSGS to MF or placebo (along with standard immunosuppression), we will study mechanistic biomarkers that correlate with podocyte injury or depletion and evaluate outcomes after 6 months. We specifically integrate novel urine, blood, and tissue markers as surrogates for FSGS progression along with unbiased profiling strategies.

Results and Conclusion

Our phase 2 trial will provide insight into the potential efficacy and safety of MF as adjunctive therapy in FSGS-a crucial step to developing a larger phase 3 study. The mechanistic assays here will guide the design of other FSGS trials and contribute to understanding AMPK activation as a potential therapeutic target in FSGS. By repurposing an inexpensive agent, our results will have implications for FSGS treatment in resource-poor settings.

A large-scale retrospective study enabled deep-learning based pathological assessment of frozen procurement kidney biopsies to predict graft loss and guide organ utilization

Lesion scores on procurement donor biopsies are commonly used to guide organ utilization for deceased-donor kidneys. However, frozen sections present challenges for histological scoring, leading to inter- and intra-observer variability and inappropriate discard. Therefore, we constructed deep-learning based models to recognize kidney tissue compartments in hematoxylin & eosin-stained sections from procurement needle biopsies performed nationwide in years 2011-2020. To do this, we extracted whole-slide abnormality features from 2431 kidneys and correlated with pathologists' scores and transplant outcomes. A Kidney Donor Quality Score (KDQS) was derived and used in combination with recipient demographic and peri-transplant characteristics to predict graft loss or assist organ utilization. The performance on wedge biopsies was additionally evaluated. Our model identified 96% and 91% of normal/sclerotic glomeruli respectively; 94% of arteries/arterial intimal fibrosis; 90% of tubules. Whole-slide features of Sclerotic Glomeruli (GS)%, Arterial Intimal Fibrosis (AIF)%, and Interstitial Space Abnormality (ISA)% demonstrated strong correlations with corresponding pathologists' scores of all 2431 kidneys, but had superior associations with post-transplant estimated glomerular filtration rates in 2033 and graft loss in 1560 kidneys. The combination of KDQS and other factors predicted one- and four-year graft loss in a discovery set of 520 kidneys and a validation set of 1040 kidneys. By using the composite KDQS of 398 discarded kidneys due to "biopsy findings", we suggest that if transplanted, 110 discarded kidneys could have had similar survival to that of other transplanted kidneys. Thus, our composite KDQS and survival prediction models may facilitate risk stratification and organ utilization while potentially reducing unnecessary organ discard.

Advancing mouse models for transplantation research

Mouse models have been instrumental in understanding mechanisms of transplant rejection and tolerance, but cross-study reproducibility and translation of experimental findings into effective clinical therapies are issues of concern. The Mouse Models in Transplantation symposium gathered scientists and physician-scientists involved in basic and clinical research in transplantation to discuss the strengths and limitations of mouse transplant models and strategies to enhance their utility. Participants recognized that increased procedure standardization, including the use of prespecified, defined endpoints, and statistical power analyses, would benefit the field. They also discussed the generation of new models that incorporate environmental and genetic variables affecting clinical outcomes as potentially important. If implemented, these strategies are expected to improve the reproducibility of mouse studies and increase their translation to clinical trials and, ideally, new Food and Drug Administration-approved drugs.

Profilin1 is required for prevention of mitotic catastrophe in murine and human glomerular diseases

The progression of proteinuric kidney diseases is associated with podocyte loss, but the mechanisms underlying this process remain unclear. Podocytes reenter the cell cycle to repair double-stranded DNA breaks. However, unsuccessful repair can result in podocytes crossing the G1/S checkpoint and undergoing abortive cytokinesis. In this study, we identified Pfn1 as indispensable in maintaining glomerular integrity - its tissue-specific loss in mouse podocytes resulted in severe proteinuria and kidney failure. Our results suggest that this phenotype is due to podocyte mitotic catastrophe (MC), characterized histologically and ultrastructurally by abundant multinucleated cells, irregular nuclei, and mitotic spindles. Podocyte cell cycle reentry was identified using FUCCI2aR mice, and we observed altered expression of cell-cycle associated proteins, such as p21, p53, cyclin B1, and cyclin D1. Podocyte-specific translating ribosome affinity purification and RNA-Seq revealed the downregulation of ribosomal RNA-processing 8 (Rrp8). Overexpression of Rrp8 in Pfn1-KO podocytes partially rescued the phenotype in vitro. Clinical and ultrastructural tomographic analysis of patients with diverse proteinuric kidney diseases further validated the presence of MC podocytes and reduction in podocyte PFN1 expression within kidney tissues. These results suggest that profilin1 is essential in regulating the podocyte cell cycle and its disruption leads to MC and subsequent podocyte loss.

Multiscale genetic architecture of donor-recipient differences reveals intronic LIMS1 mismatches associated with kidney transplant survival

Donor-recipient (D-R) mismatches outside of human leukocyte antigens (HLAs) contribute to kidney allograft loss, but the mechanisms remain unclear, specifically for intronic mismatches. We quantified non-HLA mismatches at variant-, gene-, and genome-wide scales from single nucleotide polymorphism (SNP) data of D-Rs from 2 well-phenotyped transplant cohorts: Genomics of Chronic Allograft Rejection (GoCAR; n = 385) and Clinical Trials in Organ Transplantation-01/17 (CTOT-01/17; n = 146). Unbiased gene-level screening in GoCAR uncovered the LIMS1 locus as the top-ranked gene where D-R mismatches associated with death-censored graft loss (DCGL). A previously unreported, intronic, LIMS1 haplotype of 30 SNPs independently associated with DCGL in both cohorts. Haplotype mismatches showed a dosage effect, and minor-allele introduction to major-allele-carrying recipients showed greater hazard of DCGL. The LIMS1 haplotype and the previously reported LIMS1 SNP rs893403 are expression quantitative trait loci (eQTL) in immune cells for GCC2 (not LIMS1), which encodes a protein involved in mannose-6-phosphase receptor (M6PR) recycling. Peripheral blood and T cell transcriptome analyses associated the GCC2 gene and LIMS1 SNPs with the TGF-β1/SMAD pathway, suggesting a regulatory effect. In vitro GCC2 modulation impacted M6PR-dependent regulation of active TGF-β1 and downstream signaling in T cells. Together, our data link LIMS1 locus D-R mismatches to DCGL via GCC2 eQTLs that modulate TGF-β1-dependent effects on T cells.

Nonpodocyte Roles of APOL1 Variants: An Evolving Paradigm

Since the seminal discovery of the trypanolytic, exonic variants in apolipoprotein L1 (APOL1) and their association with kidney disease in individuals of recent African ancestry, a wide body of research has emerged offering key insights into the mechanisms of disease. Importantly, the podocyte has become a focal point for our understanding of how risk genotype leads to disease, with activation of putative signaling pathways within the podocyte identified as playing a causal role in podocytopathy, FSGS, and progressive renal failure. However, the complete mechanism of genotype-to-phenotype progression remains incompletely understood in APOL1-risk individuals. An emerging body of evidence reports more than podocyte-intrinsic expression of APOL1 risk variants is needed for disease to manifest. This article reviews the seminal data and reports which placed the podocyte at the center of our understanding of APOL1-FSGS, as well as the evident shortcomings of this podocentric paradigm. We examine existing evidence for environmental and genetic factors that may influence disease, drawing from both clinical data and APOL1's fundamental role as an immune response gene. We also review the current body of data for APOL1's impact on nonpodocyte cells, including endothelial cells, the placenta, and immune cells in both a transplant and native setting. Finally, we discuss the implications of these emerging data and how the paradigm of disease might evolve as a result.

HCK induces macrophage activation to promote renal inflammation and fibrosis via suppression of autophagy

Renal inflammation and fibrosis are the common pathways leading to progressive chronic kidney disease (CKD). We previously identified hematopoietic cell kinase (HCK) as upregulated in human chronic allograft injury promoting kidney fibrosis; however, the cellular source and molecular mechanisms are unclear. Here, using immunostaining and single cell sequencing data, we show that HCK expression is highly enriched in pro-inflammatory macrophages in diseased kidneys. HCK-knockout (KO) or HCK-inhibitor decreases macrophage M1-like pro-inflammatory polarization, proliferation, and migration in RAW264.7 cells and bone marrow-derived macrophages (BMDM). We identify an interaction between HCK and ATG2A and CBL, two autophagy-related proteins, inhibiting autophagy flux in macrophages. In vivo, both global or myeloid cell specific HCK-KO attenuates renal inflammation and fibrosis with reduces macrophage numbers, pro-inflammatory polarization and migration into unilateral ureteral obstruction (UUO) kidneys and unilateral ischemia reperfusion injury (IRI) models. Finally, we developed a selective boron containing HCK inhibitor which can reduce macrophage pro-inflammatory activity, proliferation, and migration in vitro, and attenuate kidney fibrosis in the UUO mice. The current study elucidates mechanisms downstream of HCK regulating macrophage activation and polarization via autophagy in CKD and identifies that selective HCK inhibitors could be potentially developed as a new therapy for renal fibrosis.

Comparative evaluation of glomerular morphometric techniques reveals differential technical artifacts between focal segmental glomerulosclerosis and normal glomeruli

Morphometric estimates of mean or individual glomerular volume (MGV, IGV) have biological implications, over and above qualitative histologic data. However, morphometry is time-consuming and requires expertise limiting its utility in clinical cases. We evaluated MGV and IGV using plastic- and paraffin-embedded tissue from 10 control and 10 focal segmental glomerulosclerosis (FSGS) mice (aging and 5/6th nephrectomy models) using the gold standard Cavalieri (Cav) method versus the 2-profile and Weibel-Gomez (WG) methods and a novel 3-profile method. We compared accuracy, bias and precision, and quantified results obtained when sampling differing numbers of glomeruli. In both FSGS and controls, we identified an acceptable precision for MGV of 10-glomerular sampling versus 20-glomerular sampling using the Cav method, while 5-glomerular sampling was less precise. In plastic tissue, 2- or 3-profile MGVs showed greater concordance with MGV when using Cav, versus MGV with WG. IGV comparisons using the same glomeruli reported a consistent underestimation bias with both 2- or 3-profile methods versus the Cav method. FSGS glomeruli showed wider variations in bias estimation than controls. Our 3-profile method offered incremental benefit to the 2-profile method in both IGV and MGV estimation (improved correlation coefficient, Lin's concordance and reduced bias). In our control animals, we quantified a shrinkage artifact of 52% from tissue processed for paraffin-embedded versus plastic-embedded tissue. FSGS glomeruli showed overall reduced shrinkage albeit with variable artifact signifying periglomerular/glomerular fibrosis. A novel 3-profile method offers slightly improved concordance with reduced bias versus 2-profile. Our findings have implications for future studies using glomerular morphometry.

Allograft tissue under the microscope: only the beginning

PURPOSE OF REVIEW

To review novel modalities for interrogating a kidney allograft biopsy to complement the current Banff schema.

RECENT FINDINGS

Newer approaches of Artificial Intelligence (AI), Machine Learning (ML), digital pathology including Ex Vivo Microscopy, evaluation of the biopsy gene expression using bulk, single cell, and spatial transcriptomics and spatial proteomics are now available for tissue interrogation.

SUMMARY

Banff Schema of classification of allograft histology has standardized reporting of tissue pathology internationally greatly impacting clinical care and research. Inherent sampling error of biopsies, and lack of automated morphometric analysis with ordinal outputs limit its performance in prognostication of allograft health. Over the last decade, there has been an explosion of newer methods of evaluation of allograft tissue under the microscope. Digital pathology along with the application of AI and ML algorithms could revolutionize histopathological analyses. Novel molecular diagnostics such as spatially resolved single cell transcriptomics are identifying newer mechanisms underlying the pathologic diagnosis to delineate pathways of immunological activation, tissue injury, repair, and regeneration in allograft tissues. While these techniques are the future of tissue analysis, costs and complex logistics currently limit their clinical use.

Infliximab Induction Lacks Efficacy and Increases BK Virus Infection in Deceased Donor Kidney Transplant Recipients: Results of the CTOT-19 Trial

BACKGROUND

Ischemia-reperfusion (IR) of a kidney transplant (KTx) upregulates TNF α production that amplifies allograft inflammation and may negatively affect transplant outcomes.

METHODS

We tested the effects of blocking TNF peri-KTx via a randomized, double-blind, placebo-controlled, 15-center, phase 2 clinical trial. A total of 225 primary transplant recipients of deceased-donor kidneys (KTx; 38.2% Black/African American, 44% White) were randomized to receive intravenous infliximab (IFX) 3 mg/kg or saline placebo (PLBO) initiated before kidney reperfusion. All patients received rabbit anti-thymocyte globulin induction and maintenance immunosuppression (IS) with tacrolimus, mycophenolate mofetil, and prednisone. The primary end point was the difference between groups in mean 24-month eGFR.

RESULTS

There was no difference in the primary end point of 24-month eGFR between IFX (52.45 ml/min per 1.73 m 2 ; 95% CI, 48.38 to 56.52) versus PLBO (57.35 ml/min per 1.73 m 2 ; 95% CI, 53.18 to 61.52; P =0.1). There were no significant differences between groups in rates of delayed graft function, biopsy-proven acute rejection (BPAR), development of de novo donor-specific antibodies, or graft loss/death. Immunosuppression did not differ, and day 7 post-KTx plasma analyses showed approximately ten-fold lower TNF ( P <0.001) in IFX versus PLBO. BK viremia requiring IS change occurred more frequently in IFX (28.9%) versus PLBO (13.4%; P =0.004), with a strong trend toward higher rates of BKV nephropathy in IFX (13.3%) versus PLBO (4.9%; P =0.06).

CONCLUSIONS

IFX induction therapy does not benefit recipients of kidney transplants from deceased donors on this IS regimen. Because the intervention unexpectedly increased rates of BK virus infections, our findings underscore the complexities of targeting peritransplant inflammation as a strategy to improve KTx outcomes.Clinical Trial registry name and registration number:clinicaltrials.gov (NCT02495077).

Role of time from transplantation to biopsy in histologic ABMR: A single center report

BACKGROUND

Allograft biopsies with lesions of Antibody-Mediated Rejection (ABMR) with Microvascular Inflammation (MVI) have shown heterogeneous etiologies and outcomes.

METHODS

To examine factors associated with outcomes in biopsies that meet histologic ABMR criteria, we retrospectively evaluated for-cause biopsies at our center between 2011 and 2017. We included biopsies that met the diagnosis of ABMR by histology, along with simultaneous evaluation for anti-Human Leukocyte Antigen (HLA) donor-specific antibodies (DSA). We evaluated death-censored graft loss (DCGL) and used a principal component analysis (PCA) approach to identify key predictors of outcomes.

RESULTS

Out of the histologic ABMR cohort (n = 118), 70 were DSA-positive ABMR, while 48 had no DSA. DSA(+)ABMR were younger and more often female recipients. DSA(+)ABMR occurred significantly later post-transplant than DSA(-)ABMR suggesting time-dependence. DSA(+)ABMR had higher inflammatory scores (i,t), chronicity scores (ci, ct) and tended to have higher MVI scores. Immunodominance of DQ-DSA in DSA(+)ABMR was associated with higher i+t scores. Clinical/histologic factors significantly associated with DCGL after biopsy were inputted into the PCA. Principal component-1 (PC-1), which contributed 34.8% of the variance, significantly correlated with time from transplantation to biopsy, ci/ct scores and DCGL. In the PCA analyses, i, t scores, DQ-DSA, and creatinine at biopsy retained significant correlations with GL-associated PCs.

CONCLUSIONS

Time from transplantation to biopsy plays a major role in the prognosis of biopsies with histologic ABMR and MVI, likely due to ongoing chronic allograft injury over time.

Blood Transcriptomes of SARS-CoV-2-Infected Kidney Transplant Recipients Associated with Immune Insufficiency Proportionate to Severity

BACKGROUND

Among patients with COVID-19, kidney transplant recipients (KTRs) have poor outcomes compared with non-KTRs. To provide insight into management of immunosuppression during acute illness, we studied immune signatures from the peripheral blood during and after COVID-19 infection from a multicenter KTR cohort.

METHODS

We ascertained clinical data by chart review. A single sample of blood was collected for transcriptome analysis. Total RNA was poly-A selected and RNA was sequenced to evaluate transcriptome changes. We also measured cytokines and chemokines of serum samples collected during acute infection.

RESULTS

A total of 64 patients with COVID-19 in KTRs were enrolled, including 31 with acute COVID-19 (<4 weeks from diagnosis) and 33 with post-acute COVID-19 (>4 weeks postdiagnosis). In the blood transcriptome of acute cases, we identified genes in positive or negative association with COVID-19 severity scores. Functional enrichment analyses showed upregulation of neutrophil and innate immune pathways but downregulation of T cell and adaptive immune activation pathways. This finding was independent of lymphocyte count, despite reduced immunosuppressant use in most KTRs. Compared with acute cases, post-acute cases showed "normalization" of these enriched pathways after 4 weeks, suggesting recovery of adaptive immune system activation despite reinstitution of immunosuppression. Analysis of the non-KTR cohort with COVID-19 showed significant overlap with KTRs in these functions. Serum inflammatory cytokines followed an opposite trend (i.e., increased with disease severity), indicating that blood lymphocytes are not the primary source.

CONCLUSIONS

The blood transcriptome of KTRs affected by COVID-19 shows decreases in T cell and adaptive immune activation pathways during acute disease that, despite reduced immunosuppressant use, associate with severity. These pathways show recovery after acute illness.

Analysis of Cross-sectional and Longitudinal HLA and Anti-viral Responses After COVID Infection in Renal Allograft Recipients: Differences and Correlates

BACKGROUND

Characterization of anti-HLA versus anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) immune globulin isotypes in organ transplant recipients after coronavirus disease 2019 (COVID-19) infection has not been reported. We aimed to determine changes in anti-HLA antibodies in renal transplant patients with COVID-19 and compare the immunoglobulin and epitope-binding pattern versus anti-SARS-CoV-2 antibodies.

METHODS

This is a cross-sectional study of 46 kidney transplant recipients including 21 with longitudinal sampling. Using a semi-quantitative multiplex assay, we determined immunoglobulin (Ig) M, IgA, IgG, and IgG1-2-3-4 antibodies against Class I and Class II HLA, and 5 SARS-CoV-2 epitopes including the nucleocapsid protein and multiple regions of the spike protein.

RESULTS

Fourteen of 46 (30%) patients had donor-specific anti-HLA antibodies (donor-specific antibody [DSA]), 12 (26%) had non-DSA anti-HLA antibodies and 45 (98%) had anti-SARS-CoV-2 antibodies. Most DSAs targeted HLA-DQ (71%), with a dominant IgG isotype and IgG1 subtype prevalence (93%), and/or IgG3 (64%), followed by IgG2 (36%). Comparatively, there was a higher prevalence of IgA (85% versus 14%, P = 0.0001) and IgM (87%, versus 36%, P = 0.001) in the anti-SARS-CoV-2 antibody profile, when compared to DSAs, respectively. Anti-SARS-CoV-2 antibody profile was characterized by increased prevalence of IgM and IgA, when compared to DSAs. The median calculated panel reactive antibody before COVID-19 diagnosis (24%) tended to decrease after COVID-19 diagnosis (10%) but it was not statistically significant ( P = 0.1).

CONCLUSIONS

Anti-HLA antibody strength and calculated panel reactive antibody in kidney transplant recipients after COVID-19 do not significantly increase after infection. Although the IgG isotype was the dominant form in both HLA and SARS-CoV-2 antigens, the alloimmune response had a low IgA pattern, whereas anti-SARS-CoV-2 antibodies were high IgA/IgM.

Cellular recovery after prolonged warm ischaemia of the whole body

After cessation of blood flow or similar ischaemic exposures, deleterious molecular cascades commence in mammalian cells, eventually leading to their death^1,2. Yet with targeted interventions, these processes can be mitigated or reversed, even minutes or hours post mortem, as also reported in the isolated porcine brain using BrainEx technology³. To date, translating single-organ interventions to intact, whole-body applications remains hampered by circulatory and multisystem physiological challenges. Here we describe OrganEx, an adaptation of the BrainEx extracorporeal pulsatile-perfusion system and cytoprotective perfusate for porcine whole-body settings. After 1 h of warm ischaemia, OrganEx application preserved tissue integrity, decreased cell death and restored selected molecular and cellular processes across multiple vital organs. Commensurately, single-nucleus transcriptomic analysis revealed organ- and cell-type-specific gene expression patterns that are reflective of specific molecular and cellular repair processes. Our analysis comprises a comprehensive resource of cell-type-specific changes during defined ischaemic intervals and perfusion interventions spanning multiple organs, and it reveals an underappreciated potential for cellular recovery after prolonged whole-body warm ischaemia in a large mammal.

Donor–Recipient Non-HLA Variants, Mismatches and Renal Allograft Outcomes: Evolving Paradigms

Despite significant improvement in the rates of acute allograft rejection, proportionate improvements in kidney allograft longevity have not been realized, and are a source of intense research efforts. Emerging translational data and natural history studies suggest a role for anti-donor immune mechanisms in a majority of cases of allograft loss without patient death, even when overt evidence of acute rejection is not identified. At the level of the donor and recipient genome, differences in highly polymorphic HLA genes are routinely evaluated between donor and recipient pairs as part of organ allocation process, and utilized for patient-tailored induction and maintenance immunosuppression. However, a growing body of data have characterized specific variants in donor and recipient genes, outside of HLA loci, that induce phenotypic changes in donor organs or the recipient immune system, impacting transplant outcomes. Newer mechanisms for “mismatches” in these non-HLA loci have also been proposed during donor–recipient genome interactions with transplantation. Here, we review important recent data evaluating the role of non-HLA genetic loci and genome-wide donor-recipient mismatches in kidney allograft outcomes.

Blood transcriptomes of SARS-CoV-2 infected kidney transplant recipients demonstrate immune insufficiency

BACKGROUND

Kidney transplant recipients (KTRs) with COVID-19 have poor outcomes compared to non-KTRs. To provide insight into management of immunosuppression during acute illness, we studied immune signatures from the peripheral blood during and after COVID-19 infection from a multicenter KTR cohort.□.

METHODS

Clinical data were collected by chart review. PAXgene blood RNA was poly-A selected and RNA sequencing was performed to evaluate transcriptome changes.

RESULTS

A total of 64 cases of COVID-19 in KTRs were enrolled, including 31 acute cases (< 4 weeks from diagnosis) and 33 post-acute cases (>4 weeks). In the blood transcriptome of acute cases, we identified differentially expressed genes (DEGs) in positive or negative association COVID-19 severity scores. Functional enrichment analyses showed upregulation of neutrophil and innate immune pathways, but downregulation of T-cell and adaptive immune-activation pathways proportional to severity score. This finding was independent of lymphocyte count and despite reduction in immunosuppression (IS) in most KTRs. Comparison with post-acute cases showed "normalization" of these enriched pathways after >4 weeks, suggesting recovery of adaptive immune system activation despite reinstitution of IS. The latter analysis was adjusted for COVID-19 severity score and lymphocyte count. DEGs associated with worsening disease severity in a non-KTR cohort with COVID-19 (GSE152418) showed significant overlap with KTRs in these identified enriched pathways.

CONCLUSION

Blood transcriptome of KTRs affected by COVID-19 shows decrease in T-cell and adaptive immune activation pathways during acute disease that associate with severity despite IS reduction and show recovery after acute illness.

SIGNIFICANCE STATEMENT

Kidney transplant recipients (KTRs) are reported to have worse outcomes with COVID-19, and empiric reduction of maintenance immunosuppression is pursued. Surprisingly, reported rates of acute rejection have been low despite reduced immunosuppression. We evaluated the peripheral blood transcriptome of 64 KTRs either during or after acute COVID-19. We identified transcriptomic signatures consistent with suppression of adaptive T-cell responses which significantly associated with disease severity and showed evidence of recovery after acute disease, even after adjustment for lymphocyte number. Our transcriptomic findings of immune-insufficiency during acute COVID-19 provide an explanation for the low rates of acute rejection in KTRs despite reduced immunosuppression. Our data support the approach of temporarily reducing T -cell-directed immunosuppression in KTRs with acute COVID-19.

Delayed Kinetics of IgG, but Not IgA, Antispike Antibodies in Transplant Recipients following SARS-CoV-2 Infection

BACKGROUND

Kidney transplant recipients are at increased risk of severe outcomes during COVID-19. Antibodies against the virus are thought to offer protection, but a thorough characterization of anti-SARS-CoV-2 immune globulin isotypes in kidney transplant recipients following SARS-CoV-2 infection has not been reported.

METHODS

We performed a cross-sectional study of 49 kidney transplant recipients and 42 immunocompetent controls at early (≤14 days) or late (>14 days) time points after documented SARS-CoV-2 infection. Using a validated semiquantitative Luminex-based multiplex assay, we determined the abundances of IgM, IgG, IgG1-4, and IgA antibodies against five distinct viral epitopes.

RESULTS

Kidney transplant recipients showed lower levels of total IgG antitrimeric spike (S), S1, S2, and receptor binding domain (RBD) but not nucleocapsid (NC) at early versus late time points after SARS-CoV-2 infection. Early levels of IgG antispike protein epitopes were also lower than in immunocompetent controls. Anti-SARS-CoV-2 antibodies were predominantly IgG1 and IgG3, with modest class switching to IgG2 or IgG4 in either cohort. Later levels of IgG antispike, S1, S2, RBD, and NC did not significantly differ between cohorts. There was no significant difference in the kinetics of either IgM or IgA antispike, S1, RBD, or S2 on the basis of timing after diagnosis or transplant status.

CONCLUSIONS

Kidney transplant recipients mount early anti-SARS-CoV-2 IgA and IgM responses, whereas IgG responses are delayed compared with immunocompetent individuals. These findings might explain the poor outcomes in transplant recipients with COVID-19.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/JASN/2021_11_23_briggsgriffin112321.mp3.

Deep learning identified pathological abnormalities predictive of graft loss in kidney transplant biopsies

Interstitial fibrosis, tubular atrophy, and inflammation are major contributors to kidney allograft failure. Here we sought an objective, quantitative pathological assessment of these lesions to improve predictive utility and constructed a deep-learning-based pipeline recognizing normal vs. abnormal kidney tissue compartments and mononuclear leukocyte infiltrates. Periodic acid- Schiff stained slides of transplant biopsies (60 training and 33 testing) were used to quantify pathological lesions specific for interstitium, tubules and mononuclear leukocyte infiltration. The pipeline was applied to the whole slide images from 789 transplant biopsies (478 baseline [pre-implantation] and 311 post-transplant 12-month protocol biopsies) in two independent cohorts (GoCAR: 404 patients, AUSCAD: 212 patients) of transplant recipients to correlate composite lesion features with graft loss. Our model accurately recognized kidney tissue compartments and mononuclear leukocytes. The digital features significantly correlated with revised Banff 2007 scores but were more sensitive to subtle pathological changes below the thresholds in the Banff scores. The Interstitial and Tubular Abnormality Score (ITAS) in baseline samples was highly predictive of one-year graft loss, while a Composite Damage Score in 12-month post-transplant protocol biopsies predicted later graft loss. ITASs and Composite Damage Scores outperformed Banff scores or clinical predictors with superior graft loss prediction accuracy. High/intermediate risk groups stratified by ITASs or Composite Damage Scores also demonstrated significantly higher incidence of estimated glomerular filtration rate decline and subsequent graft damage. Thus, our deep-learning approach accurately detected and quantified pathological lesions from baseline or post-transplant biopsies and demonstrated superior ability for prediction of post-transplant graft loss with potential application as a prevention, risk stratification or monitoring tool.

AMPK mediates regulation of glomerular volume and podocyte survival

Herein, we report that Shroom3 knockdown, via Fyn inhibition, induced albuminuria with foot process effacement (FPE) without focal segmental glomerulosclerosis (FSGS) or podocytopenia. Interestingly, knockdown mice had reduced podocyte volumes. Human minimal change disease (MCD), where podocyte Fyn inactivation was reported, also showed lower glomerular volumes than FSGS. We hypothesized that lower glomerular volume prevented the progression to podocytopenia. To test this hypothesis, we utilized unilateral and 5/6th nephrectomy models in Shroom3-KD mice. Knockdown mice exhibited less glomerular and podocyte hypertrophy after nephrectomy. FYN-knockdown podocytes had similar reductions in podocyte volume, implying that Fyn was downstream of Shroom3. Using SHROOM3 or FYN knockdown, we confirmed reduced podocyte protein content, along with significantly increased phosphorylated AMPK, a negative regulator of anabolism. AMPK activation resulted from increased cytoplasmic redistribution of LKB1 in podocytes. Inhibition of AMPK abolished the reduction in glomerular volume and induced podocytopenia in mice with FPE, suggesting a protective role for AMPK activation. In agreement with this, treatment of glomerular injury models with AMPK activators restricted glomerular volume, podocytopenia, and progression to FSGS. Glomerular transcriptomes from MCD biopsies also showed significant enrichment of Fyn inactivation and Ampk activation versus FSGS glomeruli. In summary, we demonstrated the important role of AMPK in glomerular volume regulation and podocyte survival. Our data suggest that AMPK activation adaptively regulates glomerular volume to prevent podocytopenia in the context of podocyte injury.

Recipient APOL1 risk alleles associate with death-censored renal allograft survival and rejection episodes

Apolipoprotein L1 (APOL1) risk-alleles in donor kidneys associate with graft loss but whether recipient risk-allele expression impacts transplant outcomes is unclear. To test whether recipient APOL1 risk-alleles independently correlate with transplant outcomes, we analyzed genome-wide SNP genotyping data of donors and recipients from two kidney transplant cohorts, Genomics of Chronic Allograft Rejection (GOCAR) and Clinical Trials in Organ Transplantation (CTOT1/17). We estimated genetic ancestry (quantified as proportion of African ancestry or pAFR) by ADMIXTURE and correlated APOL1 genotypes and pAFR with outcomes. In the GOCAR discovery set, we observed that the number of recipient APOL1 G1/G2 alleles (R-nAPOL1) associated with increased risk of death-censored allograft loss (DCAL), independent of ancestry (HR = 2.14; P = 0.006), and within the subgroup of African American and Hispanic (AA/H) recipients (HR = 2.36; P = 0.003). R-nAPOL1 also associated with increased risk of any T cell-mediated rejection (TCMR) event. These associations were validated in CTOT1/17. Ex vivo studies of peripheral blood mononuclear cells revealed unanticipated high APOL1 expression in activated CD4+/CD8+ T cells and natural killer cells. We detected enriched immune response gene pathways in risk-allele carriers vs. non-carriers on the kidney transplant waitlist and among healthy controls. Our findings demonstrate an immunomodulatory role for recipient APOL1 risk-alleles associating with TCMR and DCAL. This finding has broader implications for immune mediated injury to native kidneys.

IL-9: a novel pro-podocyte survival cytokine in FSGS

Progressive focal segmental glomerulosclerosis, characterized by podocyte loss, is often refractory to treatment and leads to progressive proteinuric chronic kidney disease. Interleukin-9 (IL-9) is reported to play important roles in innate and adaptive immunity in extrarenal inflammatory diseases. By using an IL-9 knockout mouse model, Xiong et al. demonstrate IL-9 as a novel pro-podocyte survival cytokine in the adriamycin nephropathy model of focal segmental glomerulosclerosis. Sequential in vitro and in vivo data corroborate a direct protective role, rather than an immunologic role, for IL-9 on podocyte survival. This commentary highlights these novel data and discusses the necessary steps for developing IL-9 as a potential novel therapeutic for focal segmental glomerulosclerosis.

Podocyte Autophagy in Homeostasis and Disease

Autophagy is a protective mechanism that removes dysfunctional components and provides nutrition for cells. Podocytes are terminally differentiated specialized epithelial cells that wrap around the capillaries of the glomerular filtration barrier and show high autophagy level at the baseline. Here, we provide an overview of cellular autophagy and its regulation in homeostasis with specific reference to podocytes. We discuss recent data that have focused on the functional role and regulation of autophagy during podocyte injury in experimental and clinical glomerular diseases. A thorough understanding of podocyte autophagy could shed novel insights into podocyte survival mechanisms with injury and offer potential targets for novel therapeutics for glomerular disease.

Chronic transplant glomerulopathy: New insights into pathogenesis

There have been recent significant advances in short-term outcomes in renal transplantation, however, long-term allograft survival remains a challenge. With reported incidences as high of 74.5% of chronic graft loss in patients with biopsies showing transplant glomerulopathy (TG), this syndrome represents an important factor for chronic allograft complications. In this review we show an overview of the novel mechanistic insights into pathogenesis of TG, as well as a brief description of the pathology, diagnosis and newer prognostic indices within TG diagnosis. These data raise intriguing roles for cell-mediated immunity and podocyte stress in TG as well as reinforce previous associations of TG with ABMR. We also delve into management strategies for TG and report the paucity of existing clinical trial data for this prevalent condition in renal transplants.

Influence of patient characteristics and immunosuppressant management on mortality in kidney transplant recipients hospitalized with coronavirus disease 2019 (COVID-19)

The influence of patient characteristics and immunosuppression management on COVID-19 outcomes in kidney transplant recipients (KTRs) remains uncertain. We performed a single-center, retrospective review of all adult KTRs admitted to the hospital with confirmed COVID-19 between 03/15/2020 and 05/15/2020. Patients were followed from the date of admission up to 1 month following hospital discharge or study conclusion (06/15/2020). Baseline characteristics, laboratory parameters, and immunosuppression were compared between survivors and patients who died to identify predictors of mortality. 38 KTRs with a mean baseline eGFR of 52.5 ml/min/1.73 m² were hospitalized during the review period. Maintenance immunosuppression included tacrolimus (84.2%), mycophenolate (89.5%), and corticosteroids (81.6%) in the majority of patients. Eleven patients (28.9%) died during the hospitalization. Older age (OR = 2.05; 1.04-4.04), peak D-dimer (OR = 1.20; 1.04-1.39), and peak white blood cell count (OR = 1.11; 1.02-1.21) were all associated with mortality among KTRs hospitalized for COVID-19. Increased mortality was also observed among KTRs with concomitant HIV infection (87.5% vs. 36.1%; p < .01). Conversely, immunosuppression intensity and degree of reduction following COVID-19 diagnosis were not associated with either survival or acute allograft rejection. Our findings potentially support a strategy of individualization of immunosuppression targets based on patient-specific risk factors, rather than universal immunosuppression reduction for KTRs at risk from COVID-19.

Evidence of potent humoral immune activity in COVID-19-infected kidney transplant recipients

Whether kidney transplant recipients are capable of mounting an effective anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) adaptive immune response despite chronic immunosuppression is unknown and has important implications for therapy. Herein, we analyzed peripheral blood cell surface and intracellular cytokine phenotyping by flow cytometry along with serum antibody testing in 18 kidney transplant recipients with active coronavirus disease 2019 (COVID-19) infection and 36 matched, transplanted controls without COVID-19. We observed significantly fewer total lymphocytes and fewer circulating memory CD4⁺ and CD8⁺ T cells in the COVID-19 subjects. We also showed fewer anergic and senescent CD8⁺ T cells in COVID-19 individuals, but no differences in exhausted CD8⁺ T cells, nor in any of these CD4⁺ T cell subsets between groups. We also observed greater frequencies of activated B cells in the COVID-19 patients. Sixteen of 18 COVID-19 subjects tested for anti-SARS-CoV-2 serum antibodies showed positive immunoglobulin M or immunoglobulin G titers. Additional analyses showed no significant correlation among immune phenotypes and degrees of COVID-19 disease severity. Our findings indicate that immunosuppressed kidney transplant recipients admitted to the hospital with acute COVID-19 infection can mount SARS-CoV-2-reactive adaptive immune responses. The findings raise the possibility that empiric reductions in immunosuppressive therapy for all kidney transplant recipients with active COVID-19 may not be required.

4D flow MRI for the assessment of renal transplant dysfunction: initial results

OBJECTIVES

(1) Determine inter-observer reproducibility and test-retest repeatability of 4D flow parameters in renal allograft vessels; (2) determine if 4D flow measurements in the renal artery (RA) and renal vein (RV) can distinguish between functional and dysfunctional allografts; (3) correlate haemodynamic parameters with estimated glomerular filtration rate (eGFR), perfusion measured with dynamic contrast-enhanced MRI (DCE-MRI) and histopathology.

METHODS

Twenty-five prospectively recruited renal transplant patients (stable function/chronic renal allograft dysfunction, 12/13) underwent 4D flow MRI at 1.5 T. 4D flow coronal oblique acquisitions were performed in the transplant renal artery (RA) (velocity encoding parameter, VENC = 120 cm/s) and renal vein (RV) (VENC = 45 cm/s). Test-retest repeatability (n = 3) and inter-observer reproducibility (n = 10) were assessed by Cohen's kappa, coefficient of variation (CoV) and Bland-Altman statistics. Haemodynamic parameters were compared between patients and correlated to the estimated glomerular filtration rate, DCE-MRI parameters (n = 10) and histopathology from allograft biopsies (n = 15).

RESULTS

For inter-observer reproducibility, kappa was > 0.99 and 0.62 and CoV of flow was 12.6% and 7.8% for RA and RV, respectively. For test-retest repeatability, kappa was > 0.99 and 0.5 and CoV of flow was 27.3% and 59.4%, for RA and RV, respectively. RA (p = 0.039) and RV (p = 0.019) flow were both significantly reduced in dysfunctional allografts. Both identified chronic allograft dysfunction with good diagnostic performance (RA: AUC = 0.76, p = 0.036; RV: AUC = 0.8, p = 0.018). RA flow correlated negatively with histopathologic interstitial fibrosis score ci (ρ = - 0.6, p = 0.03).

CONCLUSIONS

4D flow parameters had better repeatability in the RA than in the RV. RA and RV flow can identify chronic renal allograft dysfunction, with RA flow correlating with histopathologic interstitial fibrosis score.

KEY POINTS

• Inter-observer reproducibility of 4D flow measurements was acceptable in both the transplant renal artery and vein, but test-retest repeatability was better in the renal artery than in the renal vein. • Blood flow measurements obtained with 4D flow MRI in the renal artery and renal vein are significantly reduced in dysfunctional renal transplants. • Renal transplant artery flow correlated negatively with histopathologic interstitial fibrosis score.

Key driver genes as potential therapeutic targets in renal allograft rejection

Acute rejection (AR) in renal transplantation is an established risk factor for reduced allograft survival. Molecules with regulatory control among immune pathways of AR that are inadequately suppressed, despite standard-of-care immunosuppression, could serve as important targets for therapeutic manipulation to prevent rejection. Here, an integrative, network-based computational strategy incorporating gene expression and genotype data of human renal allograft biopsy tissue was applied, to identify the master regulators - the key driver genes (KDGs) - within dysregulated AR pathways. A 982-meta-gene signature with differential expression in AR versus non-AR was identified from a meta-analysis of microarray data from 735 human kidney allograft biopsy samples across 7 data sets. Fourteen KDGs were derived from this signature. Interrogation of 2 publicly available databases identified compounds with predicted efficacy against individual KDGs or a key driver-based gene set, respectively, which could be repurposed for AR prevention. Minocycline, a tetracycline antibiotic, was chosen for experimental validation in a murine cardiac allograft model of AR. Minocycline attenuated the inflammatory profile of AR compared with controls and when coadministered with immunosuppression prolonged graft survival. This study demonstrates that a network-based strategy, using expression and genotype data to predict KDGs, assists target prioritization for therapeutics in renal allograft rejection.

Acute Kidney Injury in Hospitalized Patients with COVID-19

IMPORTANCE

Preliminary reports indicate that acute kidney injury (AKI) is common in coronavirus disease (COVID)-19 patients and is associated with worse outcomes. AKI in hospitalized COVID-19 patients in the United States is not well-described.

OBJECTIVE

To provide information about frequency, outcomes and recovery associated with AKI and dialysis in hospitalized COVID-19 patients.

DESIGN

Observational, retrospective study.

SETTING

Admitted to hospital between February 27 and April 15, 2020.

PARTICIPANTS

Patients aged ≥18 years with laboratory confirmed COVID-19 Exposures: AKI (peak serum creatinine increase of 0.3 mg/dL or 50% above baseline). Main Outcomes and Measures: Frequency of AKI and dialysis requirement, AKI recovery, and adjusted odds ratios (aOR) with mortality. We also trained and tested a machine learning model for predicting dialysis requirement with independent validation.

RESULTS

A total of 3,235 hospitalized patients were diagnosed with COVID-19. AKI occurred in 1406 (46%) patients overall and 280 (20%) with AKI required renal replacement therapy. The incidence of AKI (admission plus new cases) in patients admitted to the intensive care unit was 68% (553 of 815). In the entire cohort, the proportion with stages 1, 2, and 3 AKI were 35%, 20%, 45%, respectively. In those needing intensive care, the respective proportions were 20%, 17%, 63%, and 34% received acute renal replacement therapy. Independent predictors of severe AKI were chronic kidney disease, systolic blood pressure, and potassium at baseline. In-hospital mortality in patients with AKI was 41% overall and 52% in intensive care. The aOR for mortality associated with AKI was 9.6 (95% CI 7.4-12.3) overall and 20.9 (95% CI 11.7-37.3) in patients receiving intensive care. 56% of patients with AKI who were discharged alive recovered kidney function back to baseline. The area under the curve (AUC) for the machine learned predictive model using baseline features for dialysis requirement was 0.79 in a validation test.

CONCLUSIONS AND RELEVANCE

AKI is common in patients hospitalized with COVID-19, associated with worse mortality, and the majority of patients that survive do not recover kidney function. A machine-learned model using admission features had good performance for dialysis prediction and could be used for resource allocation.

APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO): Design and Rationale

INTRODUCTION

Much of the higher risk for end-stage kidney disease (ESKD) in African American individuals relates to ancestry-specific variation in the apolipoprotein L1 gene (APOL1). Relative to kidneys from European American deceased-donors, kidneys from African American deceased-donors have shorter allograft survival and African American living-kidney donors more often develop ESKD. The National Institutes of Health (NIH)-sponsored APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO) is prospectively assessing kidney allograft survival from donors with recent African ancestry based on donor and recipient APOL1 genotypes.

METHODS

APOLLO will evaluate outcomes from 2614 deceased kidney donor-recipient pairs, as well as additional living-kidney donor-recipient pairs and unpaired deceased-donor kidneys.

RESULTS

The United Network for Organ Sharing (UNOS), Association of Organ Procurement Organizations, American Society of Transplantation, American Society for Histocompatibility and Immunogenetics, and nearly all U.S. kidney transplant programs, organ procurement organizations (OPOs), and histocompatibility laboratories are participating in this observational study. APOLLO employs a central institutional review board (cIRB) and maintains voluntary partnerships with OPOs and histocompatibility laboratories. A Community Advisory Council composed of African American individuals with a personal or family history of kidney disease has advised the NIH Project Office and Steering Committee since inception. UNOS is providing data for outcome analyses.

CONCLUSION

This article describes unique aspects of the protocol, design, and performance of APOLLO. Results will guide use of APOL1 genotypic data to improve the assessment of quality in deceased-donor kidneys and could increase numbers of transplanted kidneys, reduce rates of discard, and improve the safety of living-kidney donation.

Non-HLA donor-recipient mismatches in kidney transplantation-A stone left unturned

In kidney transplantation, short-term allograft survival has improved due to improvements in acute rejection episodes without corresponding improvements in long-term survival. Although current organ allocation algorithms take into account human leukocyte antigen (HLA) matching to reduce antidonor alloimmune responses, it is likely that genomic variation at non-HLA loci (ie, non-HLA donor-recipient [D-R] pair mismatches) play a role in the "non-self" responses and ultimately affect long-term allograft survival. Existing data from both animal models and human studies suggest an association between non-HLA D-R mismatches and kidney allograft outcomes. In this minireview, we examine existing and emerging data and discuss putative mechanisms on the role of non-HLA D-R mismatches on long-term allograft outcomes in kidney transplantation.

Multiparametric magnetic resonance imaging shows promising results to assess renal transplant dysfunction with fibrosis

Here we assessed the diagnostic value of a quantitative multiparametric magnetic resonance imaging (mpMRI) protocol for evaluation of renal allograft dysfunction with fibrosis. Twenty-seven renal transplant patients, including 15 with stable functional allografts (eGFR mean 71.5 ml/min/1.73m²), and 12 with chronic dysfunction/established fibrosis (eGFR mean 30.1 ml/min/1.73m²), were enrolled in this prospective single-center study. Sixteen of the patients had renal biopsy (mean 150 days) before the MRI. All patients underwent mpMRI at 1.5T including intravoxel-incoherent motion diffusion-weighted imaging, diffusion tensor imaging, blood oxygen level dependent (BOLD R₂*) and T₁ quantification. True diffusion D, pseudodiffusion D*, perfusion fraction PF, apparent diffusion coefficient (ADC), fractional anisotropy (FA), R₂* and T₁ were calculated for cortex and medulla. ΔT₁ was calculated as (100x(T₁ Cortex-T₁ Medulla)/T₁ Cortex). Test-retest repeatability and inter-observer reproducibility were assessed in four and ten patients, respectively. mpMRI parameters had substantial test-retest and interobserver repeatability (coefficient of variation under 15%), except for medullary PF and D* (coefficient of variation over 25%). Cortical ADC, D, medullary ADC and ΔT₁ were all significantly decreased, while cortical T₁ was significantly elevated in fibrotic allografts. Cortical T₁ showed positive correlation to the Banff fibrosis and tubular atrophy scores. The combination of ΔT₁ and cortical ADC had excellent cross-validated diagnostic performance for detection of chronic dysfunction with fibrosis. Cortical ADC and T₁ had good performance for predicting eGFR decline at 18 months (4 or more ml/min/1.73m²/year). Thus, the combination of cortical ADC and T₁ measurements shows promising results for the non-invasive assessment of renal allograft histology and outcomes.

Disruption of MAGI2-RapGEF2-Rap1 signaling contributes to podocyte dysfunction in congenital nephrotic syndrome caused by mutations in MAGI2

The essential role of membrane associated guanylate kinase 2 (MAGI2) in podocytes is indicated by the phenotypes of severe glomerulosclerosis of both MAGI2 knockout mice and in patients with congenital nephrotic syndrome (CNS) caused by mutations in MAGI2. Here, we show that MAGI2 forms a complex with the Rap1 guanine nucleotide exchange factor, RapGEF2, and that this complex is lost when expressing MAGI2 CNS variants. Co-expression of RapGEF2 with wild-type MAGI2, but not MAGI2 CNS variants, enhanced activation of the small GTPase Rap1, a central signaling node in podocytes. In mice, podocyte-specific RapGEF2 deletion resulted in spontaneous glomerulosclerosis, with qualitative glomerular features comparable to MAGI2 knockout mice. Knockdown of RapGEF2 or MAGI2 in human podocytes caused similar reductions in levels of Rap1 activation and Rap1-mediated downstream signaling. Furthermore, human podocytes expressing MAGI2 CNS variants show severe abnormalities of cellular morphology and dramatic loss of actin cytoskeletal organization, features completely rescued by pharmacological activation of Rap1 via a non-MAGI2 dependent upstream pathway. Finally, immunostaining of kidney sections from patients with congenital nephrotic syndrome and MAGI2 mutations showed reduced podocyte Rap1-mediated signaling. Thus, MAGI2-RapGEF2-Rap1 signaling is essential for normal podocyte function. Hence, disruption of this pathway is an important cause of the renal phenotype induced by MAGI2 CNS mutations.

Outcomes of renal transplantation in patients with previous hematologic malignancies

Recommendations regarding the appropriateness of renal transplantation in patients with prior hematologic malignancies are limited. Given the lack of available data, studies are needed to assess which of these patients will maximally benefit from renal transplantation. This study was undertaken to describe the incidence of new or recurrent malignancy as well as patient and allograft survival, acute rejection, and serious infections in patients with prior hematologic malignancies receiving renal transplantation. This was a single center retrospective review of all adult patients with a previous hematologic malignancy who received a living or deceased renal transplantation between January 2009 and January 2016. Eight renal transplantation recipients with prior hematologic malignancies were identified and followed for a minimum of 3 years. Six patients received prior chemotherapy and five had a prior hematopoietic stem cell transplant. Median time from remission to transplant was 2.6 years. Three-year patient and allograft survival were 87% and 75%, respectively. Three patients were diagnosed with new cancers within 3 years post-renal transplantation; one of which died from cancer-related complications with a functioning allograft. There was concern for recurrent hematologic malignancies in two patients based on serologic studies, but, both of these patients were alive with functioning allografts at 3-year follow-up. Our experience suggests that renal transplantation can be successfully performed in select patients with prior hematologic malignancy but with a significant risk for de novo malignancy post-transplant, which may be associated with an overall poor prognosis. Decisions regarding renal transplantation candidacy should be made based on risk stratification and multidisciplinary discussions with patients, hematologists, and transplant providers.

A Peripheral Blood Gene Expression Signature to Diagnose Subclinical Acute Rejection

BACKGROUND

In kidney transplant recipients, surveillance biopsies can reveal, despite stable graft function, histologic features of acute rejection and borderline changes that are associated with undesirable graft outcomes. Noninvasive biomarkers of subclinical acute rejection are needed to avoid the risks and costs associated with repeated biopsies.

METHODS

We examined subclinical histologic and functional changes in kidney transplant recipients from the prospective Genomics of Chronic Allograft Rejection (GoCAR) study who underwent surveillance biopsies over 2 years, identifying those with subclinical or borderline acute cellular rejection (ACR) at 3 months (ACR-3) post-transplant. We performed RNA sequencing on whole blood collected from 88 individuals at the time of 3-month surveillance biopsy to identify transcripts associated with ACR-3, developed a novel sequencing-based targeted expression assay, and validated this gene signature in an independent cohort.

RESULTS

Study participants with ACR-3 had significantly higher risk than those without ACR-3 of subsequent clinical acute rejection at 12 and 24 months, faster decline in graft function, and decreased graft survival in adjusted Cox analysis. We identified a 17-gene signature in peripheral blood that accurately diagnosed ACR-3, and validated it using microarray expression profiles of blood samples from 65 transplant recipients in the GoCAR cohort and three public microarray datasets. In an independent cohort of 110 transplant recipients, tests of the targeted expression assay on the basis of the 17-gene set showed that it identified individuals at higher risk of ongoing acute rejection and future graft loss.

CONCLUSIONS

Our targeted expression assay enabled noninvasive diagnosis of subclinical acute rejection and inflammation in the graft and may represent a useful tool to risk-stratify kidney transplant recipients.

Pretransplant transcriptomic signature in peripheral blood predicts early acute rejection

Commonly available clinical parameters fail to predict early acute cellular rejection (EAR, occurring within 6 months after transplant), a major risk factor for graft loss after kidney transplantation. We performed whole-blood RNA sequencing at the time of transplant in 235 kidney transplant recipients enrolled in a prospective cohort study (Genomics of Chronic Allograft Rejection [GoCAR]) and evaluated the relationship of pretransplant transcriptomic profiles with EAR. EAR was associated with downregulation of NK and CD8+ T cell gene signatures in pretransplant blood. We identified a 23-gene set that predicted EAR in the discovery (n = 81, and AUC = 0.80) and validation (n = 74, and AUC = 0.74) sets. Exclusion of recipients with 5 or 6 HLA donor mismatches increased the AUC to 0.89. The risk score derived from the gene set was also significantly associated with acute cellular rejection after 6 months, antibody-mediated rejection and/or de novo donor-specific antibodies, and graft loss in a cohort of 154 patients, combining the validation set and additional GoCAR patients with surveillance biopsies between 6 and 24 months (n = 80) posttransplant. This 23-gene set is a potentially important new tool for determination of the recipient's immunological risk before kidney transplantation, and facilitation of an individualized approach to immunosuppressive therapy.

APOL1 high-risk genotypes and renal transplantation

The discovery of apolipoprotein L1 (APOL1) gene variants and its association with kidney disease in African-Americans represent a significant breakthrough in understanding the genetic basis of ancestry-based differences in a public health problem. The role these variants play in renal transplantation is still incompletely understood. This article reviews the epidemiologic data and current reports of APOL1 variant pathogenesis in transplantation. We examine existing data on outcomes in APOL1 high-risk kidneys, high-risk APOL1 recipients, live donors with high-risk mutations and non-renal transplantation of high-risk APOL1 organs. We discuss the rapidly evolving role and potential pros and cons of APOL1 genotyping of donors and recipients in transplantation. Finally, we highlight the ongoing nationwide National Institutes of Health-sponsored "APOL1 Long-term Kidney Transplantation Outcomes (APOLLO)" study, which will quantify outcomes and "second hits" in pertinent to APOL1 high-risk variants in renal transplantation.

Analysis of Biomarkers Within the Initial 2 Years Posttransplant and 5-Year Kidney Transplant Outcomes: Results From Clinical Trials in Organ Transplantation-17

BACKGROUND

An early posttransplant biomarker/surrogate marker for kidney allograft loss has the potential to guide targeted interventions. Previously published findings, including results from the Clinical Trials in Organ Transplantation (CTOT)-01 study, showed that elevated urinary chemokine CXCL9 levels and elevated frequencies of donor-reactive interferon gamma (IFNγ)-producing T cells by enzyme-linked immunosorbent spot (ELISPOT) assay associated with acute cellular rejection within the first year and with lower 1-year posttransplant estimated glomerular filtration rate (eGFR). How well these biomarkers correlate with late outcomes, including graft loss, is unclear.

METHODS

In CTOT-17, we obtained 5-year outcomes in the CTOT-01 cohort and correlated them with (a) biomarker results and (b) changes in eGFR (Chronic Kidney Disease Epidemiology Collaboration formula) over the initial 2 years posttransplant using univariable analysis and multivariable logistic regression.

RESULTS

Graft loss occurred in 14 (7.6%) of 184 subjects 2 to 5 years posttransplant. Neither IFNγ ELISPOTs nor urinary CXCL9 were informative. In contrast, a 40% or greater decline in eGFR from 6 months to 2 years posttransplant independently correlated with 13-fold odds of 5-year graft loss (adjusted odds ratio, 13.1; 95% confidence interval, 3.0-56.6), a result that was validated in the independent Genomics of Chronic Allograft Rejection cohort (n = 165; adjusted odds ratio, 11.2).

CONCLUSIONS

We conclude that although pretransplant and early posttransplant ELISPOT and chemokine measurements associate with outcomes within 2 years posttransplant, changes in eGFR between 3 or 6 months and 24 months are better surrogates for 5-year outcomes, including graft loss.

SHROOM3-FYN Interaction Regulates Nephrin Phosphorylation and Affects Albuminuria in Allografts

BACKGROUND

We previously showed that the presence of a CKD-associated locus in SHROOM3 in a donor kidney results in increased expression of SHROOM3 (an F-actin-binding protein important for epithelial morphogenesis, via rho-kinase [ROCK] binding); this facilitates TGF-b signaling and allograft fibrosis. However, other evidence suggests Shroom3 may have a protective role in glomerular development.

METHODS

We used human data, Shroom3 knockdown podocytes, and inducible shRNA-mediated knockdown mice to study the role of Shroom3 in adult glomeruli.

RESULTS

Expression data from the Nephroseq database showed glomerular and nonglomerular SHROOM3 had opposing associations with renal function in CKD biopsy samples. In human allografts, homozygosity at rs17319721, the SHROOM3 locus linked with lower GFR, was associated with reduced albuminuria by 2 years after transplant. Although our previous data showed reduced renal fibrosis with tubular Shroom3 knockdown, this study found that glomerular but not tubular Shroom3 knockdown induced albuminuria. Electron microscopy revealed diffuse foot process effacement, and glomerular RNA-sequencing showed enrichment of tyrosine kinase signaling and podocyte actin cytoskeleton pathways in knockdown mice. Screening SHROOM3-interacting proteins identified FYN (a src-kinase) as a candidate.We confirmed the interaction of endogenous SHROOM3 with FYN in human podocytes via a critical Src homology 3-binding domain, distinct from its ROCK-binding domain. Shroom3-Fyn interaction was required in vitro and in vivo for activation of Fyn kinase and downstream nephrin phosphorylation in podocytes. SHROOM3 knockdown altered podocyte morphology, cytoskeleton, adhesion, and migration.

CONCLUSIONS

We demonstrate a novel mechanism that may explain SHROOM3's dichotomous associations in glomerular versus nonglomerular compartments in CKD.

Analysis of OPTN/UNOS registry suggests the number of HLA matches and not mismatches is a stronger independent predictor of kidney transplant survival

HLA matching and mismatching, while inversely related, are not exact opposites. Here we determined the independent effects of HLA matching and mismatching on outcomes in deceased donor kidney transplant recipients. The United Network for Organ Sharing database (1995-2012) was utilized and analyzed for delayed graft function, one-year acute rejection, and death-censored graft survival using combined multivariable models including HLA matching and mismatching. Sensitivity analyses were performed using the subgroup of deceased donor kidney transplant patients after 2003 with more uniform HLA nomenclature and resampling analyses using bootstrapping on complete data available from 96,236 recipients. Individually, both HLA matching and mismatching showed significant associations with graft survival. Adjusting the model to take into account both matching and mismatching simultaneously, the degree of HLA mismatching lost significance while matching continued to have a significant prediction for delayed graft function, the one-year acute rejection rate, and graft survival. Sensitivity analyses and bootstrapping showed similar results for all studied outcomes. Thus, analysis of this large cohort demonstrates the apparent greater association of HLA matching over HLA mismatching on both early allograft events as well as graft survival. Future analyses should preferentially utilize HLA matching as a covariate over mismatching for accurately reflecting impact on graft outcomes.

Abstract P322: Interaction of Shroom3 With Fyn Impacts Phosphorylation of Nephrin Causing Proteinuria With Foot Process Effacement

In the translational GoCAR study, we identified that a CKD-associated SHROOM3-SNP, and tubular Shroom3 expression correlated with the development of fibrosis in renal allografts. We showed that SHROOM3 facilitated TGF-B signaling suggesting its potential role as a therapeutic target. However, recent data suggest a protective role for SHROOM3 in proteinuria and glomerular development. To study the role of SHROOM3 in adult glomeruli, we used doxycycline-inducible (DOX), shRNA-mediated SHROOM3 knockdown, Podocin- and tubular-specific (PAX8)-RTTA mice, comparing these to non-transgenic DOX-fed littermates. After 2wks of DOX, adult Podo-RTTA mice developed significant albuminuria compared to littermates. Albuminuria was reversible on DOX-withdrawal, and reappeared on re-initiation. No podocyte loss [WT1 stain] was seen in these mice(8-wks DOX). EM revealed >50% foot process effacement. PAX8-RTTA mice did not show proteinuria. Glomerular RNA- seq identifed intracellular signaling/Small GTPAse signaling/integrin signaling/ actin-cytoskeleton among downregulated Gene-ontology terms in knockdown mice vs Controls. To identify protein interacting partners of SHROOM3, we performed mass spectrometry on protein lysates of 293-T cells overexpressing SHROOM3 immunoprecipitated (IP) with either anti-V5, -SHROOM3 or IgG. Among 491 unique interactions, we confirmed SHROOM3 as the top ranking protein. Interestingly, FYN - a src-kinase - was a top ranking candidate. Podocyte FYN is crucial for NPHS1-phosphorylation, and FYN-deficient mice show identical proteinuria phenotype. In human podocytes, we confirmed the interaction of endogenous SHROOM3 and FYN by IP. Glomerular protein extracts of Shroom3-knockdown mice showed decreased phosphorylation of FYN, and NPHS1. In human allografts from GoCAR, we identifed a corresponding reduced albuminuria (>1year post-transplant) associated with homozygosity of the risk allele in the donor. In summary, Podocyte-specific SHROOM3 knockdown causes a reversible proteinuria phenotype in adult mice, by interacting with FYN, a mechanism distinct from its effect on renal fibrosis in allografts.

Temporal trends of dialysis requiring acute kidney injury after orthotopic cardiac and liver transplant hospitalizations

Background

The epidemiology and outcomes of acute kidney injury (AKI) in prevalent non-renal solid organ transplant recipients is unknown.

Methods

We assessed the epidemiology of trends in acute kidney injury (AKI) in orthotopic cardiac and liver transplant recipients in the United States. We used the Nationwide Inpatient Sample to evaluate the yearly incidence trends (2002 to 2013) of the primary outcome, defined as AKI requiring dialysis (AKI-D) in hospitalizations after cardiac and liver transplantation. We also evaluated the trend and impact of AKI-D on hospital mortality and adverse discharge using adjusted odds ratios (aOR).

Results

The proportion of hospitalizations with AKI (9.7 to 32.7% in cardiac and 8.5 to 28.1% in liver transplant hospitalizations; p_trend<0.01) and AKI-D (1.63 to 2.33% in cardiac and 1.32 to 2.65% in liver transplant hospitalizations; p_trend<0.01) increased from 2002-2013. This increase in AKI-D was explained by changes in race and increase in age and comorbidity burden of transplant hospitalizations. AKI-D was associated with increased odds of in hospital mortality (aOR 2.85; 95% CI 2.11-3.80 in cardiac and aOR 2.00; 95% CI 1.55-2.59 in liver transplant hospitalizations) and adverse discharge [discharge other than home] (aOR 1.97; 95% CI 1.53-2.55 in cardiac and 1.91; 95% CI 1.57-2.30 in liver transplant hospitalizations).

Conclusions

This study highlights the growing burden of AKI-D in non-renal solid organ transplant recipients and its devastating impact, and emphasizes the need to develop strategies to reduce the risk of AKI to improve health outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0657-8) contains supplementary material, which is available to authorized users.

Early conversion to belatacept after renal transplantation

Belatacept is a non-nephrotoxic immunosuppressive agent, which may make it the ideal agent for patients with delayed or slow graft function on calcineurin inhibitors. There are limited data on conversion of patients to belatacept within 6 months of transplantation. Between January 2012 and December 2015, 16 patients were converted to belatacept for delayed or poor graft function (eGFR<30 mL/min/1.73 m² , MDRD); three were HIV positive. Conversion protocols were analyzed in patients ≤4 months and 4-6 months post-transplantation. Mean serum creatinine levels after belatacept conversion were compared with preconversion levels. Patient survival was 100%, and graft survival was 88%. The mean creatinine fell from 3.9±1.82 mg/dL prebelatacept conversion to 2.1±1.1 mg/dL at 6 months and 1.9±0.47 mg/dL (median 1.8 mg/dL) at 12 months postconversion. There was no significant increased risk of rejection, infection, or malignancy. HIV parameters remained largely stable. Early conversion to belatacept in patients with DGF or slow graft function is safe and efficacious, in a single-center nonrandomized retrospective analysis.