Nivolumab + Tacrolimus + Prednisone ± Ipilimumab for Kidney Transplant Recipients With Advanced Cutaneous Cancers.

PURPOSE: Cancer-related mortality rates among kidney transplant recipients (KTR) are high, but these patients have largely been excluded from trials of immune checkpoint inhibitors because of immunosuppression and risk of treatment-related allograft loss (TRAL). We conducted a prospective clinical trial testing nivolumab (NIVO) + tacrolimus (TACRO) + prednisone (PRED) ± ipilimumab (IPI) in KTR with advanced cutaneous cancers. METHODS: Adult KTR with advanced melanoma or basal, cutaneous squamous, or Merkel cell carcinomas were eligible. Immunosuppression was standardized to TACRO (serum trough 2-5 ng/mL) + PRED 5 mg once daily. Patients then received NIVO 480 mg IV once every 4 weeks. The primary composite end point was partial or complete (tumor) response (CR) or stable disease per RECIST v1.1 without allograft loss at 16W. Patients with progressive disease (PD) could receive IPI 1 mg/kg IV + NIVO 3 mg/kg once every 3 weeks × 4 followed by NIVO. Donor-derived cell-free DNA (dd-cfDNA) levels were measured approximately once every 2 weeks as a potential predictor of allograft rejection. RESULTS: Among eight evaluable patients, none met the trial's primary end point. All eight patients experienced PD on NIVO + TACRO + PRED; TRAL occurred in one patient. Six patients then received IPI + NIVO + TACRO + PRED. Best overall responses: two CR (one with TRAL) and four PD (one with TRAL). In total, 7 of 8 pre-NIVO tumor biopsies contained a paucity of infiltrating immune cells. In total, 2 of 5 on-NIVO biopsies demonstrated moderate immune infiltrates; both patients later experienced a CR to IPI + NIVO. In 2 of 3 patients with TRAL, dd-cfDNA elevations occurred 10 and 15 days before increases in serum creatinine. CONCLUSION: In most KTR with advanced skin cancer, TACRO + PRED provides insufficient allograft protection and compromises immune-mediated tumor regression after administration of NIVO ± IPI. Elevated dd-cfDNA levels can signal treatment-related allograft rejection earlier than rises in serum creatinine.

The Banff 2022 Kidney Meeting Work Plan: Data-driven refinement of the Banff Classification for renal allografts.

The XVIth Banff Meeting for Allograft Pathology was held in Banff, Alberta, Canada, from September 19 to 23, 2022, as a joint meeting with the Canadian Society of Transplantation. In addition to a key focus on the impact of microvascular inflammation and biopsy-based transcript analysis on the Banff Classification, further sessions were devoted to other aspects of kidney transplant pathology, in particular T cell-mediated rejection, activity and chronicity indices, digital pathology, xenotransplantation, clinical trials, and surrogate endpoints. Although the output of these sessions has not led to any changes in the classification, the key role of Banff Working Groups in phrasing unanswered questions, and coordinating and disseminating results of investigations addressing these unanswered questions was emphasized. This paper summarizes the key Banff Meeting 2022 sessions not covered in the Banff Kidney Meeting 2022 Report paper and also provides an update on other Banff Working Group activities relevant to kidney allografts.

Single Nucleus RNA Sequencing of Remnant Kidney Biopsies and Urine Cell RNA Sequencing Reveal Cell Specific Markers of Covid-19 Acute Kidney Injury.

Acute kidney injury (AKI) in COVID-19 patients is associated with high mortality and morbidity. Critically ill COVID-19 patients are at twice the risk of in-hospital mortality compared to non-COVID AKI patients. We know little about the cell-specific mechanism in the kidney that contributes to worse clinical outcomes in these patients. New generation single cell technologies have the potential to provide insights into physiological states and molecular mechanisms in COVID-AKI. One of the key limitations is that these patients are severely ill posing significant risks in procuring additional biopsy tissue. We recently generated single nucleus RNA-sequencing data using COVID-AKI patient biopsy tissue as part of the human kidney atlas. Here we describe this approach in detail and report deeper comparative analysis of snRNAseq of 4 COVID-AKI, 4 reference, and 6 non-COVID-AKI biopsies. We also generated and analyzed urine transcriptomics data to find overlapping COVID-AKI-enriched genes and their corresponding cell types in the kidney from snRNA-seq data. We identified all major and minor cell types and states by using by using less than a few cubic millimeters of leftover tissue after pathological workup in our approach. Differential expression analysis of COVID-AKI biopsies showed pathways enriched in viral response, WNT signaling, kidney development, and cytokines in several nephron epithelial cells. COVID-AKI profiles showed a much higher proportion of altered TAL cells than non-COVID AKI and the reference samples. In addition to kidney injury and fibrosis markers indicating robust remodeling we found that, 17 genes overlap between urine cell COVID-AKI transcriptome and the snRNA-seq data from COVID-AKI biopsies. A key feature was that several of the distal nephron and collecting system cell types express these markers. Some of these markers have been previously observed in COVID-19 studies suggesting a common mechanism of injury and potentially the kidney as one of the sources of soluble factors with a potential role in disease progression. Translational Statement: The manuscript describes innovation, application and discovery that impact clinical care in kidney disease. First, the approach to maximize use of remnant frozen clinical biopsies to inform on clinically relevant molecular features can augment existing pathological workflow for any frozen tissue without much change in the protocol. Second, this approach is transformational in medical crises such as pandemics where mechanistic insights are needed to evaluate organ injury, targets for drug therapy and diagnostic and prognostic markers. Third, the cell type specific and soluble markers identified and validated can be used for diagnoses or prognoses in AKI due to different etiologies and in multiorgan injury.

Hyperspectral Raman Imaging for Automated Recognition of Human Renal Amyloid.

In the clinical setting, routine identification of the main types of tissue amyloid deposits, light-chain amyloid (AL) and serum amyloid A (AA), is based on histochemical staining; rarer types of amyloid require mass spectrometry analysis. Raman spectroscopic imaging is an analytical tool, which can be used to chemically map, and thus characterize, the molecular composition of fluid and solid tissue. In this proof-of-concept study, we tested the feasibility of applying Raman spectroscopy combined with artificial intelligence to detect and characterize amyloid deposits in unstained frozen tissue sections from kidney biopsies with pathologic diagnosis of AL and AA amyloidosis and control biopsies with no amyloidosis (NA). Raman hyperspectral images, mapped in a 2D grid-like fashion over the tissue sections, were obtained. Three machine learning-assisted analysis models of the hyperspectral images could accurately distinguish AL (types λ and κ), AA, and NA 93-100% of the time. Although very preliminary, these findings illustrate the potential of Raman spectroscopy as a technique to identify, and possibly, subtype renal amyloidosis.

Non-Perturbative Identification and Subtyping of Amyloidosis in Human Kidney Tissue with Raman Spectroscopy and Machine Learning.

Amyloids are proteins with characteristic beta-sheet secondary structures that display fibrillary ultrastructural configurations. They can result in pathologic lesions when deposited in human organs. Various types of amyloid protein can be routinely identified in human tissue specimens by special stains, immunolabeling, and electron microscopy, and, for certain forms of amyloidosis, mass spectrometry is required. In this study, we applied Raman spectroscopy to identify immunoglobulin light chain and amyloid A amyloidosis in human renal tissue biopsies and compared the results with a normal kidney biopsy as a control case. Raman spectra of amyloid fibrils within unstained, frozen, human kidney tissue demonstrated changes in conformation of protein secondary structures. By using t-distributed stochastic neighbor embedding (t-SNE) and density-based spatial clustering of applications with noise (DBSCAN), Raman spectroscopic data were accurately classified with respect to each amyloid type and deposition site. To the best of our knowledge, this is the first time Raman spectroscopy has been used for amyloid characterization of ex vivo human kidney tissue samples. Our approach, using Raman spectroscopy with machine learning algorithms, shows the potential for the identification of amyloid in pathologic lesions.

Evaluation of the Modified Oxford Score in Recurrent IgA Nephropathy in North American Kidney Transplant Recipients: The Banff Recurrent Glomerulonephritis Working Group Report.

BACKGROUND: The modified Oxford classification mesangial and endocapillary hypercellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and the presence of crescents (MEST-C) of immunoglobulin A nephropathy (IgAN) was recently shown to be a predictor of graft failure in Asians with recurrent IgAN. We aimed to validate these findings in a cohort from North American centers participating in the Banff Recurrent Glomerulopathies Working Group. METHODS: We examined 171 transplant recipients with end-stage kidney disease because of IgAN; 100 of them with biopsy-proven recurrent IgAN (57 of them had complete MEST-C scores) and 71 with no recurrence. RESULTS: IgAN recurrence, which was associated with younger age at transplantation ( P = 0.012), strongly increased the risk of death-censored graft failure (adjusted hazard ratio, 5.10 [95% confidence interval (CI), 2.26-11.51]; P < 0.001). Higher MEST-C score sum was associated with death-censored graft failure (adjusted hazard ratio, 8.57 [95% CI, 1.23-59.85; P = 0.03] and 61.32 [95% CI, 4.82-779.89; P = 0.002] for score sums 2-3 and 4-5 versus 0, respectively), and so were the single components endocapillary hypercellularity, interstitial fibrosis/tubular atrophy, and crescents ( P < 0.05 each). Overall, most of the pooled adjusted hazard ratio estimates associated with each MEST-C component were consistent with those from the Asian cohort (heterogeneity I2 close to 0%, and P > 0.05). CONCLUSIONS: Our findings may validate the prognostic usefulness of the Oxford classification for recurrent IgAN and support the inclusion of the MEST-C score in allograft biopsies diagnostic reports.

Precision nephrology identified tumor necrosis factor activation variability in minimal change disease and focal segmental glomerulosclerosis.

The diagnosis of nephrotic syndrome relies on clinical presentation and descriptive patterns of injury on kidney biopsies, but not specific to underlying pathobiology. Consequently, there are variable rates of progression and response to therapy within diagnoses. Here, an unbiased transcriptomic-driven approach was used to identify molecular pathways which are shared by subgroups of patients with either minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). Kidney tissue transcriptomic profile-based clustering identified three patient subgroups with shared molecular signatures across independent, North American, European, and African cohorts. One subgroup had significantly greater disease progression (Hazard Ratio 5.2) which persisted after adjusting for diagnosis and clinical measures (Hazard Ratio 3.8). Inclusion in this subgroup was retained even when clustering was limited to those with less than 25% interstitial fibrosis. The molecular profile of this subgroup was largely consistent with tumor necrosis factor (TNF) pathway activation. Two TNF pathway urine markers were identified, tissue inhibitor of metalloproteinases-1 (TIMP-1) and monocyte chemoattractant protein-1 (MCP-1), that could be used to predict an individual's TNF pathway activation score. Kidney organoids and single-nucleus RNA-sequencing of participant kidney biopsies, validated TNF-dependent increases in pathway activation score, transcript and protein levels of TIMP-1 and MCP-1, in resident kidney cells. Thus, molecular profiling identified a subgroup of patients with either MCD or FSGS who shared kidney TNF pathway activation and poor outcomes. A clinical trial testing targeted therapies in patients selected using urinary markers of TNF pathway activation is ongoing.

Renal Involvement of CD20-Negative Intravascular Large B Cell Lymphoma with Neurological Manifestations.

The involvement of hematological tumors such as lymphoma in the kidneys is a well-recognized phenomenon. Some of the distinct reported pathological processes resulting in kidney dysfunction include minimal change disease, lymphocytic invasion of the parenchyma, immune complex disposition, immunotactoid glomerulopathy, membranous glomerulopathy, and acute tubular injury. We report a rare case of CD20-negative intravascular lymphoma found on a kidney biopsy in a male with primary angiitis of the central nervous system (CNS) who presented with acute kidney injury and proteinuria. After the initiation of rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone (R-CHOP), kidney function improved and proteinuria resolved.

A 2020 Banff Antibody-mediatedInjury Working Group examination of international practices for diagnosing antibody-mediated rejection in kidney transplantation - a cohort study.

The Banff antibody-mediated rejection (ABMR) classification is vulnerable to misinterpretation, but the reasons are unclear. To better understand this vulnerability, we evaluated how ABMR is diagnosed in practice. To do this, the Banff Antibody-Mediated Injury Workgroup electronically surveyed an international cohort of nephrologists/surgeons (n = 133) and renal pathologists (n = 99). Most providers (97%) responded that they use the Banff ABMR classification at least sometimes, but DSA information is often not readily available. Only 41.1% (55/133) of nephrologists/surgeons and 19.2% (19/99) of pathologists reported that they always have DSA results when the biopsy is available. Additionally, only 19.6% (26/133) of nephrologists/surgeons responded that non-HLA antibody or molecular transcripts are obtained when ABMR histologic features are present but DSA is undetected. Several respondents agreed that histologic features concerning for ABMR in the absence of DSA and/or C4d are not well accounted for in the current classification [31.3% (31/99) pathologists and 37.6% (50/133) nephrologist/surgeons]. The Banff ABMR classification appears widely accepted, but efforts to improve the accessibility of DSA information for the multidisciplinary care team are needed. Further clarity is also needed in Banff ABMR nomenclature to account for the spectrum of ABMR and for histologic features suspicious for ABMR when DSA is absent.

A prospective multicenter pilot study of HIV-positive deceased donor to HIV-positive recipient kidney transplantation: HOPE in action.

HIV-positive donor to HIV-positive recipient (HIV D+/R+) transplantation is permitted in the United States under the HIV Organ Policy Equity Act. To explore safety and the risk attributable to an HIV+ donor, we performed a prospective multicenter pilot study comparing HIV D+/R+ vs HIV-negative donor to HIV+ recipient (HIV D-/R+) kidney transplantation (KT). From 3/2016 to 7/2019 at 14 centers, there were 75 HIV+ KTs: 25 D+ and 50 D- (22 recipients from D- with false positive HIV tests). Median follow-up was 1.7 years. There were no deaths nor differences in 1-year graft survival (91% D+ vs 92% D-, P = .9), 1-year mean estimated glomerular filtration rate (63 mL/min D+ vs 57 mL/min D-, P = .31), HIV breakthrough (4% D+ vs 6% D-, P > .99), infectious hospitalizations (28% vs 26%, P = .85), or opportunistic infections (16% vs 12%, P = .72). One-year rejection was higher for D+ recipients (50% vs 29%, HR: 1.83, 95% CI 0.84-3.95, P = .13) but did not reach statistical significance; rejection was lower with lymphocyte-depleting induction (21% vs 44%, HR: 0.33, 95% CI 0.21-0.87, P = .03). In this multicenter pilot study directly comparing HIV D+/R+ with HIV D-/R+ KT, overall transplant and HIV outcomes were excellent; a trend toward higher rejection with D+ raises concerns that merit further investigation.

ANCA-associated pauci-immune necrotizing glomerulonephritis during the treatment with pembrolizumab.

Cancer immunotherapy is rapidly changing the treatment paradigm in oncology, and immune checkpoint inhibitors (ICPIs) have been used successfully in a variety of cancer types. Specific side effects termed immune-related adverse events (irAEs) have now been described in various organ systems, including the kidney. Renal complications have rarely been reported compared with other irAEs and mostly consist of acute interstitial nephritis. Only rare cases of ICPI-related glomerulonephritis have been described. Herein, we report the case of an adult patient treated with pembrolizumab (anti-PD-1) for squamous cell carcinoma (SCC), who developed infectious enterocolitis, and ANCA-related with diffuse necrotizing crescentic glomerulonephritis, both conditions potentially linked to treatment with pembrolizumab.

Low-Level Proteinuria in Systemic Lupus Erythematosus.

INTRODUCTION: In patients with systemic lupus erythematosus (SLE) without concurrent active urinary sediment or unexplained acute kidney injury (AKI), current guidelines recommend performing a kidney biopsy in those with at least 500 mg/24-hour (European League Against Rheumatism/European Renal Association-European Dialysis and Transplant Association [EULAR/ERA-EDTA]) or 1000 mg/24-hour (American College of Rheumatology [ACR]) proteinuria. To evaluate the relevance of these indications, we studied histopathologic findings in patients with SLE with proteinuria below these cutoffs. METHODS: We retrospectively reviewed the clinical, laboratory and histological characteristics of patients with SLE with <1000 mg/24-hour proteinuria (or mg/g urinary protein-to-creatinine ratio [UPCR]) who underwent their first kidney biopsy between 2003 and 2018. RESULTS: We identified 87 patients with SLE with proteinuria less than 1000 mg/24-hour (or mg/g UPCR); 52 of 87 (60%) with isolated proteinuria, that is, without AKI or active urinary sediment (hematuria). Histologic evidence of lupus nephritis (LN) was present in 40 of 52 (76%). Of the 40 patients with LN, 12 had class I or II, 14 had class III or IV, 8 had class V, 6 had a combined proliferative and membranous LN. Non-lupus diagnoses included focal segmental glomerulosclerosis, acute interstitial nephritis, and others. Patient's age, low C3, low C4, and positivity for anti-double-stranded DNA (anti-dsDNA) antibodies predicted the histological diagnosis of LN on univariate logistic regression; however, a multivariate model including these parameters as independent covariates failed to predict LN. CONCLUSIONS: Patients with SLE with low-level proteinuria may have significant lupus- or non-lupus-related kidney disease with management implications. There was a significant burden of severe forms of LN. The presence of LN was not predicted by laboratory abnormalities. Based on our findings, we suggest current guidelines be revised to expand kidney biopsy indications to include isolated proteinuria of any grade.

BK Virus RNA in Renal Allograft Biopsies.

BK polyomavirus-associated nephropathy (BKpyVAN) remains a cause of graft loss in kidney transplant recipients on immunosuppressive therapy. Its diagnosis relies on the identification of BK virus (BKV) in the renal allograft biopsy by positive immunohistochemical (IHC) stain for the viral SV40 large T antigen, although in situ hybridization (ISH) for viral DNA is used in some centers. We examined tissue detection of BKV RNA by RNAscope, a novel, automated ISH test, in 61 allograft biopsies from 56 patients with BKpyVAN. We found good correlation between the estimate of BKV tissue load by RNAscope ISH and SV40 IHC (R2 = 0.65, p<0.0001). RNAscope ISH showed 88% sensitivity and 79% specificity and, as an alternative test, could confirm the presence of BKV tissue in presumed BKpyVAN and rule out BKV as the causative agent in JC virus nephropathy. We also used tissue BK viral load estimates by both RNAscope ISH and SV40 IHC to examine the relation between tissue and plasma BK levels and found significant correlation only between BK viremia and tissue BK measured by RNAscope ISH. Our findings suggest that the RNAscope ISH assay could be a reliable test for BKV detection in allograft biopsies.

Renal crystal-storing histiocytosis involving glomeruli - A comprehensive clinicopathologic analysis.

Crystal-storing histiocytosis (CSH) is a rare manifestation of monoclonal gammopathy in which histiocytes containing monoclonal proteins in their cytoplasm are found in various organs of the body including the kidney. Within the kidney, these monoclonal crystal-laden histiocytes have been described to occur in the interstitium (most commonly) or in the glomerular mesangium. CSH within glomerular capillary loops has rarely been reported. We describe three cases of CSH primarily affecting the glomerular capillaries and review the literature of CSH in general. Twenty cases of CSH involving the kidney are present in the literature; three describe CSH in glomeruli, only one of which showed histiocytes predominantly in glomerular capillary loops, while 15 had predominantly or solely interstitial CSH. Most cases involve IgG kappa crystals with only one case involving lambda light chain. Patients with CSH predominantly involving the glomerular capillaries showed a trend toward lower serum creatinine and proteinuria at presentation, and several patients with CSH lacked a definitive diagnosis of a monoclonal gammopathy at the time of diagnosis, emphasizing the role that kidney biopsy and particularly electron microscopy play in diagnosis of this entity.

Biomarkers of Chronic Renal Tubulointerstitial Injury.

Progression of renal parenchyma injury is characterized by increasing interstitial fibrosis and tubular atrophy, irrespective of the cause. Histopathologic assessment of renal tissue obtained by biopsy remains the gold standard for determining the presence and extent of tubulointerstitial scarring. Discovery of robust non-invasive means for capturing a snapshot and for longitudinal monitoring of parenchymal deterioration has been the focus of intense multimodal effort by investigators within the renal community and beyond. Research in this field has included the use of in vitro and in vivo experimental models and has fostered the development and evaluation of tissue and biofluid assays for novel analytes with potential translation to the diagnosis and prognosis of kidney disease. Here, we examine recent advances in the search of "biomarkers" for detection of renal tubulointerstitial scarring and prediction of renal outcome in human renal disease.

Microvascular inflammation in renal allograft biopsies assessed by endothelial and leukocyte co-immunostain: a retrospective study on reproducibility and clinical/prognostic correlates.

The most prominent histologic lesion in antibody-mediated rejection is microvascular inflammation (MVI); however, its recognition and scoring can be challenging and poorly reproducible between pathologists. We developed a dual immunohistochemical (IHC)-stain (anti-CD34/anti-CD45 for endothelium/leukocytes) as ancillary tool to improve on the semi-quantitative Banff scores and allow quantification of MVI. We examined the relationship between CD34-CD45 IHC-based quantitative MVI score (the inflamed peritubular capillary ratio, iptcr) and renal-graft failure or donor-specific antibodies (DSA) strength at the time of biopsy. Quantitative iptcr score was significantly associated with renal graft failure (hazard ratio 1.81, per 1 SD-unit [0.13 points] of iptcr-increase; P = 0.026) and predicted the presence and strength of DSA (ordinal odds ratio: 2.42; P = 0.005; 75 biopsies/60 kidney transplant recipients; 30 HLA- and/or ABO-incompatible). Next, we assessed inter-pathologist agreement for ptc score and ptc extent (focal/diffuse) using CD34-CD45 IHC as compared to conventional stain. Compared to conventional stain, CD34-CD45 IHC significantly increased inter-pathologist agreement on ptc score severity and extent (κ-coefficient from 0.52-0.80 and 0.46-0.68, respectively, P < 0.001). Our findings show that CD34-CD45 IHC improves reproducibility of MVI scoring and facilitates MVI quantification and introduction of a dual anti-CD34/CD45 has the potential to improve recognition of MVI ahead of DSA results.

Beyond the microscope: interpreting renal biopsy findings in the era of precision medicine.

As rapid progress in science and biotechnology is affecting the practice of renal medicine, increasingly precise diagnostic assessment is needed to select the most effective therapeutic approach for individual patients. The kidney biopsy remains the gold standard for the diagnosis of renal disease, but the field of renal pathology is evolving, classification of renal parenchyma lesions and histopathological diagnostic criteria are undergoing more validation and updates, and new technologies and assays are sought to improve efficiency and accuracy of the diagnostic process. How new knowledge and scientific advances may potentially affect renal pathology is discussed.

Reproducibility and Feasibility of Strategies for Morphologic Assessment of Renal Biopsies Using the Nephrotic Syndrome Study Network Digital Pathology Scoring System.

Context Testing reproducibility is critical for the development of methodologies for morphologic assessment. Our previous study using the descriptor-based Nephrotic Syndrome Study Network Digital Pathology Scoring System (NDPSS) on glomerular images revealed variable reproducibility. Objective To test reproducibility and feasibility of alternative scoring strategies for digital morphologic assessment of glomeruli and explore use of alternative agreement statistics. Design The original NDPSS was modified (NDPSS1 and NDPSS2) to evaluate (1) independent scoring of each individual biopsy level, (2) use of continuous measures, (3) groupings of individual descriptors into classes and subclasses prior to scoring, and (4) indication of pathologists' confidence/uncertainty for any given score. Three and 5 pathologists scored 157 and 79 glomeruli using the NDPSS1 and NDPSS2, respectively. Agreement was tested using conventional (Cohen κ) and alternative (Gwet agreement coefficient 1 [AC1]) agreement statistics and compared with previously published data (original NDPSS). Results Overall, pathologists' uncertainty was low, favoring application of the Gwet AC1. Greater agreement was achieved using the Gwet AC1 compared with the Cohen κ across all scoring methodologies. Mean (standard deviation) differences in agreement estimates using the NDPSS1 and NDPSS2 compared with the single-level original NDPSS were -0.09 (0.17) and -0.17 (0.17), respectively. Using the Gwet AC1, 79% of the original NDPSS descriptors had good or excellent agreement. Pathologist feedback indicated the NDPSS1 and NDPSS2 were time-consuming. Conclusions The NDPSS1 and NDPSS2 increased pathologists' scoring burden without improving reproducibility. Use of alternative agreement statistics was strongly supported. We suggest using the original NDPSS on whole slide images for glomerular morphology assessment and for guiding future automated technologies.

Interstitial fibrosis scored on whole-slide digital imaging of kidney biopsies is a predictor of outcome in proteinuric glomerulopathies.

Background: Interstitial fibrosis (IF), tubular atrophy (TA) and interstitial inflammation (II) are known determinants of progression of renal disease. Standardized quantification of these features could add value to current classification of glomerulopathies. Methods: We studied 315 participants in the Nephrotic Syndrome Study Network (NEPTUNE) study, including biopsy-proven minimal change disease (MCD = 98), focal segmental glomerulosclerosis (FSGS = 121), membranous nephropathy (MN = 59) and IgA nephropathy (IgAN = 37). Cortical IF, TA and II were quantified (%) on digitized whole-slide biopsy images, by five pathologists with high inter-reader agreement (intra-class correlation coefficient >0.8). Tubulointerstitial messenger RNA expression was measured in a subset of patients. Multivariable Cox proportional hazards models were fit to assess association of IF with the composite of 40% decline in estimated glomerular filtration rate (eGFR) and end-stage renal disease (ESRD) and separately as well, and with complete remission (CR) of proteinuria. Results: IF was highly correlated with TA (P < 0.001) and II (P < 0.001). Median IF varied by diagnosis: FSGS 17, IgAN 21, MN 7, MCD 1 (P < 0.001). IF was strongly correlated with baseline eGFR (P < 0.001) and proteinuria (P = 0.002). After adjusting for clinical pathologic diagnosis, age, race, global glomerulosclerosis, baseline proteinuria, eGFR and medications, each 10% increase in IF was associated with a hazard ratio of 1.29 (P < 0.03) for ESRD/40% eGFR decline, but was not significantly associated with CR. A total of 981 genes were significantly correlated with IF (|r| > 0.4, false discovery rate (FDR) < 0.01), including upstream regulators such as tumor necrosis factor, interferon gamma (IFN-gamma), and transforming growth factor beta 1 (TGF-B1), and signaling pathways for antigen presentation and hepatic fibrosis. Conclusions: The degree of IF is associated with risk of eGFR decline across different types of proteinuric glomerulopathy, correlates with inflammatory and fibrotic gene expression, and may have predictive value in assessing risk of progression.