Antibrush Border Antibody Disease: A Case Series.

Antibrush border antibody (ABBA) disease is a rare cause of kidney disease characterized by progressive renal tubular injury associated with immune complex deposition along the basement membranes of the proximal tubule and circulating autoantibodies to brush border antigens. Several antigens have been identified as targets of autoantibodies in this disease, including low-density lipoprotein receptor related protein 2 (LRP2), cubilin, and amnionless proteins. We present 9 patients from 2 academic medical centers and describe the clinicopathologic characteristics and outcome data. All patients presented with acute kidney injury and proteinuria. Pathology confirmed immune complex deposition along proximal tubular basement membranes in all patients, but the majority (6/8) also showed segmental glomerular subepithelial immune complexes. Two of 3 patients treated with rituximab demonstrated stabilization of kidney function; 1 of these patients had mantle cell lymphoma. One patient with lung cancer showed stabilization of disease after treatment of the malignancy. The remaining patients progressed to end-stage kidney disease with either conservative therapy (3 patients) or immunosuppression with glucocorticoids (2 patients). This series highlights the poor prognosis of ABBA disease, but a potential benefit of anti-B cell therapy or treatment of an underlying malignancy in some cases.

Signaling crosstalk between tumor endothelial cells and immune cells in the microenvironment of solid tumors.

Tumor-associated endothelial cells (TECs) are crucial mediators of immune surveillance and immune escape in the tumor microenvironment (TME). TECs driven by angiogenic growth factors form an abnormal vasculature which deploys molecular machinery to selectively promote the function and recruitment of immunosuppressive cells while simultaneously blocking the entry and function of anti-tumor immune cells. TECs also utilize a similar set of signaling regulators to promote the metastasis of tumor cells. Meanwhile, the tumor-infiltrating immune cells further induce the TEC anergy by secreting pro-angiogenic factors and prevents further immune cell penetration into the TME. Understanding the complex interactions between TECs and immune cells will be needed to successfully treat cancer patients with combined therapy to achieve vasculature normalization while augmenting antitumor immunity. In this review, we will discuss what is known about the signaling crosstalk between TECs and tumor-infiltrating immune cells to reveal insights and strategies for therapeutic targeting.

Challenges and Opportunities for the Clinical Translation of Spatial Transcriptomics Technologies.

Background: The first spatially resolved transcriptomics platforms, GeoMx (Nanostring) and Visium (10x Genomics) were launched in 2019 and were recognized as the method of the year by Nature Methods in 2020. The subsequent refinement and expansion of these and other technologies to increase -plex, work with formalin-fixed paraffin-embedded tissue, and analyze protein in addition to gene expression have only added to their significance and impact on the biomedical sciences. In this perspective, we focus on two platforms for spatial transcriptomics, GeoMx and Visium, and how these platforms have been used to provide novel insight into kidney disease. The choice of platform will depend largely on experimental questions and design. The application of these technologies to clinically sourced biopsies presents the opportunity to identify specific tissue biomarkers that help define disease etiology and more precisely target therapeutic interventions in the future. Summary: In this review, we provide a description of the existing and emerging technologies that can be used to capture spatially resolved gene and protein expression data from tissue. These technologies have provided new insight into the spatial heterogeneity of diseases, how reactions to disease are distributed within a tissue, which cells are affected, and molecular pathways that predict disease and response to therapy. Key Message: The upcoming years will see intense use of spatial transcriptomics technologies to better define the pathophysiology of kidney diseases and develop novel diagnostic tests to guide personalized treatments for patients.

AA amyloidosis With Ig-Dominant Staining and Diagnostically Unusual Features.

Introduction: Although serum amyloid A (AA) amyloid may occasionally show nonspecific staining by immunofluorescence (IF), the correct diagnosis can usually be determined by integrating pathologic features and clinical scenario, and using AA amyloid immunohistochemistry (IHC) and/or mass spectrometry. A recent mass spectrometry-based study described false-positive Ig IF staining in a subset of AA amyloid cases. Methods: We sought to delineate clinicopathologic features of AA amyloid with Ig-dominant staining by using a retrospective review. Results: AA amyloid with Ig-dominant staining was identified in 10 patients from 5 institutions, representing 1.2% to 4% of AA amyloid kidney biopsies. Evidence of a monoclonal protein was documented in 0% to 2.7% of patients with AA amyloid screened for inclusion, but 30% of those with Ig-dominant staining. The patient population had equal sex distribution and presented at median age of 68.5 years with nephrotic proteinuria and kidney impairment. Etiologies of AA amyloid included injection drug use (30%), autoimmune disease (20%), and chronic infection (10%); 40% had no identified clinical association. On biopsy, heavy chain (co)dominant staining by IF (in 80%), discordant distribution in Ig staining (in 20%), tubulointerstitial nephritis (in 30%), and/or crescents (in 10%) were present. Two of 3 patients with paraproteinemia had concordant heavy and/or light chain dominant staining within the AA amyloid. Two cases were initially misdiagnosed as Ig-associated amyloidosis. Conclusion: We describe the morphologic spectrum of AA amyloidosis with Ig-dominant staining which may have clinical, laboratory, and pathologic overlap with amyloid light chain (AL), amyloid heavy chain, and heavy and light chain (AHL) amyloidosis.

Multi-omic analysis of human kidney tissue identified medulla-specific gene expression patterns.

The kidney medulla is a specialized region with important homeostatic functions. It has been implicated in genetic and developmental disorders along with ischemic and drug-induced injuries. Despite its role in kidney function and disease, the medulla's baseline gene expression and epigenomic signatures have not been well described in the adult human kidney. Here we generated and analyzed gene expression (RNA-seq), chromatin accessibility (ATAC-seq), chromatin conformation (Hi-C) and spatial transcriptomic data from the adult human kidney cortex and medulla. Tissue samples were obtained from macroscopically dissected cortex and medulla of tumor-adjacent normal material in nephrectomy specimens from five male patients. We used these carefully annotated specimens to reassign incorrectly labeled samples in the larger public Genotype-Tissue Expression (GTEx) Project, and to extract meaningful medullary gene expression signatures. Using integrated analysis of gene expression, chromatin accessibility and conformation profiles, we found insights into medulla development and function and then validated this by spatial transcriptomics and immunohistochemistry. Thus, our datasets provide a valuable resource for functional annotation of variants from genome-wide association studies and are freely accessible through an epigenome browser portal.

Therapeutic targeting of tumor spheroids in a 3D microphysiological renal cell carcinoma-on-a-chip system.

Metastatic renal cell carcinoma (RCC) remains an incurable disease for most patients highlighting an urgent need for new treatments. However, the preclinical investigation of new therapies is limited by traditional two-dimensional (2D) cultures which do not recapitulate the properties of tumor cells within a collagen extracellular matrix (ECM), while human tumor xenografts are time-consuming, expensive and lack adaptive immune cells. We report a rapid and economical human microphysiological system ("RCC-on-a-chip") to investigate therapies targeting RCC spheroids in a 3D collagen ECM. We first demonstrate that culture of RCC cell lines A498 and RCC4 in a 3D collagen ECM more faithfully reproduces the gene expression program of primary RCC tumors compared to 2D culture. We next used bortezomib as a cytotoxin to develop automated quantification of dose-dependent tumor spheroid killing. We observed that viable RCC spheroids exhibited collective migration within the ECM and demonstrated that our 3D system can be used to identify compounds that inhibit spheroid collective migration without inducing cell death. Finally, we demonstrate the RCC-on-a-chip as a platform to model the trafficking of tumor-reactive T cells into the ECM and observed antigen-specific A498 spheroid killing by engineered human CD8+ T cells expressing an ROR1-specific chimeric antigen receptor. In summary, the phenotypic differences between the 3D versus 2D environments, rapid imaging-based readout, and the ability to carefully study the impact of individual variables with quantitative rigor will encourage adoption of the RCC-on-a-chip system for testing a wide range of emerging therapies for RCC.

Single cell atlas of kidney cancer endothelial cells reveals distinct expression profiles and phenotypes.

Background: Tumor endothelial cells (TECs) represent the primary interface between the tumor microenvironment and circulating immune cells, however their phenotypes are incompletely understood in highly vascularized clear cell renal cell carcinoma (ccRCC). Methods: We purified tumor and matched normal endothelial cells (NECs) from ccRCC specimens and performed single-cell RNA-sequencing to create a reference-quality atlas available as a searchable web resource for gene expression patterns. We established paired primary TECs and NECs cultures for ex vivo functional testing. Results: TECs from multiple donors shared a common phenotype with increased expression of pathways related to extracellular matrix regulation, cell-cell communication, and insulin-like growth factor signaling that was conserved in comparison to hepatocellular carcinoma associated TECs, suggesting convergent TEC phenotypes between unrelated tumors. Cultured TECs stably maintained a core program of differentially regulated genes, were inherently resistant to apoptosis after vascular endothelial growth factor removal and displayed increased adhesiveness to subsets of immune cells including regulatory T-cells. Conclusions: Our studies delineate unique functional and phenotypic properties of TECs, which may provide insights into their interactions with available and emerging therapies. Functional phenotypes of cultured TECs suggest potential mechanisms of resistance to both antiangiogenic and immune-based therapies.

Immunohistochemical Detection of 5T4 in Renal Cell Carcinoma.

5T4 (trophoblast glycoprotein encoded by TPBG ) is a cancer/testis antigen highly expressed in renal cell carcinoma (RCC) and many other cancers but rarely in normal tissues. Interest in developing 5T4 as a prognostic biomarker and direct targeting of 5T4 by emerging receptor-engineered cellular immunotherapies has been hampered by the lack of validated 5T4-specific reagents for immunohistochemistry (IHC). We tested 4 commercially available monoclonal antibodies (mAbs) for the detection of 5T4 in formalin-fixed, paraffin-embedded RCC and normal tissues. Using parental and TPBG -edited A498 cells, 3 mAbs showed 5T4 specificity. Further analyses focused on 2 mAbs with the most robust staining (MBS1750093, Ab134162). IHC on tissue microarrays incorporating 263 renal tumors showed high staining concordance of these 2 mAbs ranging from 0.80 in chromophobe RCC to 0.89 in advanced clear cell RCC (ccRCC). MBS1750093, the most sensitive, exhibited 2+/3+ staining in papillary RCC (92.2%) > advanced ccRCC (60.0%) > chromophobe RCC (43.6%) > localized ccRCC (39.6%) > oncocytoma (22.7%). RNA in situ hybridization also revealed high levels of TPBG RNA were present most frequently in papillary and advanced ccRCC. In advanced ccRCC, there was a trend towards higher 5T4 expression and regional or distant metastases. Normal organ controls showed no or weak staining with the exception of focal moderate staining in kidney glomeruli and distal tubules by IHC. These data identify mAbs suitable for detecting 5T4 in formalin-fixed, paraffin-embedded tissues and demonstrate both interpatient and histologic subtype heterogeneity. Our validated 5T4 IHC protocol will facilitate biomarker studies and support the therapeutic targeting of 5T4.

Integrated TCR repertoire analysis and single-cell transcriptomic profiling of tumor-infiltrating T cells in renal cell carcinoma identifies shared and tumor-restricted expanded clones with unique phenotypes.

Objective responses of metastatic renal cell carcinoma (RCC) associated with systemic immunotherapies suggest the potential for T-cell-mediated tumor clearance. Recent analyses associate clonally expanded T cells present in the tumor at diagnosis with responses to immune checkpoint inhibitors (ICIs). To identify and further characterize tumor-associated, clonally expanded T cells, we characterized the density, spatial distribution, T-cell receptor (TCR) repertoire, and transcriptome of tumor-infiltrating T cells from 14 renal tumors at the time of resection and compared them with T cells in peripheral blood and normal adjacent kidney. Multiplex immunohistochemistry revealed that T-cell density was higher in clear cell RCC (ccRCC) than in other renal tumor histologies with spatially nonuniform T-cell hotspots and exclusion zones. TCR repertoire analysis also revealed increased clonal expansion in ccRCC tumors compared with non-clear cell histologies or normal tissues. Expanded T-cell clones were most frequently CD8+ with some detectable in peripheral blood or normal kidney and others found exclusively within the tumor. Divergent expression profiles for chemokine receptors and ligands and the Ki67 proliferation marker distinguished tumor-restricted T-cell clones from those also present in blood suggesting a distinct phenotype for subsets of clonally expanded T cells that also differed for upregulated markers of T-cell activation and exhaustion. Thus, our single-cell level stratification of clonally expanded tumor infiltrating T-cell subpopulations provides a framework for further analysis. Future studies will address the spatial orientation of these clonal subsets within tumors and their association with treatment outcomes for ICIs or other therapeutic modalities.

A Diverse Spectrum of Immune Complex- and Complement-Mediated Kidney Diseases Is Associated With Mantle Cell Lymphoma.

Introduction: There are limited reports on kidney biopsy findings in patients with mantle cell lymphoma (MCL). Methods: We initiated a multi-institutional, retrospective review of kidney biopsy findings in patients with active and treated MCL. Results: A total of 30 patients with MCL and kidney biopsies were identified, with a median age of 67 (range 48-87) years, 73% of whom were men. A total of 20 patients had active MCL at the time of biopsy, of whom 14 (70%) presented with acute kidney injury (AKI), proteinuria and/or hematuria, and biopsy findings potentially attributable to lymphoma. Of the 14, 11 had immune complex (IC) or complement-mediated (C3) disease including proliferative glomerulonephritis (GN) with monotypic Ig deposits (PGNMID [2]), C3GN, (2), secondary membranous nephropathy (MN [3]), tubular basement membrane (TBM) deposits (2), and modest lupus-like GN (2). Lymphomatous infiltration was present in 8 of the 20 patients, 5 with coincident IC or C3 lesions. A total of 6 patients with available follow-up were treated for MCL, all with clinical remission of GN (2 PGNMID, 2 C3GN, and 2 MN). Conclusion: MCL is associated with diverse monoclonal and polyclonal glomerular and extra-glomerular IC and C3 disease. For patients with active MCL and kidney dysfunction requiring biopsy, 70% had findings due or potentially due to lymphoma, including 55% with IC or C3 disease and 40% had lymphomatous kidney infiltration. IC and C3GN in the setting of active MCL was responsive to lymphoma-directed therapy.

Digital spatial profiling of collapsing glomerulopathy.

Collapsing glomerulopathy is a histologically distinct variant of focal and segmental glomerulosclerosis that presents with heavy proteinuria and portends a poor prognosis. Collapsing glomerulopathy can be triggered by viral infections such as HIV or SARS-CoV-2. Transcriptional profiling of collapsing glomerulopathy lesions is difficult since only a few glomeruli may exhibit this histology within a kidney biopsy and the mechanisms driving this heterogeneity are unknown. Therefore, we used recently developed digital spatial profiling (DSP) technology which permits quantification of mRNA at the level of individual glomeruli. Using DSP, we profiled 1,852 transcripts in glomeruli isolated from formalin fixed paraffin embedded sections from HIV or SARS-CoV-2-infected patients with biopsy-confirmed collapsing glomerulopathy and used normal biopsy sections as controls. Even though glomeruli with collapsing features appeared histologically similar across both groups of patients by light microscopy, the increased resolution of DSP uncovered intra- and inter-patient heterogeneity in glomerular transcriptional profiles that were missed in early laser capture microdissection studies of pooled glomeruli. Focused validation using immunohistochemistry and RNA in situ hybridization showed good concordance with DSP results. Thus, DSP represents a powerful method to dissect transcriptional programs of pathologically discernible kidney lesions.

Early Transplant Arteriopathy in Kidney Transplantation.

BACKGROUND: Early dysfunction of renal allografts may be associated with vascular injury, which raises the specter of active rejection processes that require medical intervention. In our practice, we have encountered patients who present with delayed graft function and demonstrate a unique pattern of endothelial cell injury that raises concern for rejection in their biopsy. Therefore, we sought to systematically determine the biopsy characteristics and outcome of these patients. METHODS: During a 17-year period at the University of Washington in Seattle, United States, we identified 24 cases of a distinct arterial vasculopathy presenting in the first year posttransplantation. This early transplant arteriopathy (ETA) is characterized by endothelial cell swelling and intimal edema but without the intimal arteritis that defines vascular rejection. RESULTS: Approximately 1% of transplant biopsies during the study period showed ETA, almost all of which were in deceased donor organs (96%), and most presented with delayed graft function (54%) or increased serum creatinine (38%) soon after transplantation (median 13 days; range, 5-139). In this study, 77% of patients were managed expectantly, with only 2 patients (7.6%) subsequently developing acute vascular rejection. Except for 1 patient who died, all patients had functioning allografts at 1 year follow-up. CONCLUSION: Recognizing ETA and distinguishing it from vascular rejection is important to prevent over-treatment because most patients appear to recover allograft function rapidly with expectant management.

Pathogenesis of coronavirus disease 2019-associated kidney injury.

PURPOSE OF REVIEW: The current review summarizes the pathologic findings in kidneys from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients who have had autopsies or undergone biopsy, and the pathogenic mechanisms implicated in coronavirus disease 2019 (COVID-19)-associated kidney diseases. RECENT FINDINGS: Direct infection of the kidney by SARS-CoV-2 is not common, and convincing morphologic evidence of substantive kidney infection by SARS-CoV-2 is lacking. Severe COVID-19-associated acute kidney injury is likely multifactorial and results from the physiologic disturbances and therapies used to treat this illness. COVID-19-associated collapsing glomerulopathy (COVAN) is seen almost exclusively in patients with apolipoprotein L1 high-risk genotypes with no evidence of direct infection of the kidney by SARS-CoV-2. SUMMARY: The prevailing evidence does not support substantive or persistent infection of kidneys in COVID-19 and indirect means of tissue injury are favored, although a 'hit and run' model cannot be excluded. COVAN frequently occurs in patients with mild respiratory systems, suggesting that innate and adaptive immune responses to SARS-CoV-2 infection may provide the second hit needed for the development of collapsing glomerulopathy in susceptible individuals.

Multicenter Clinicopathologic Correlation of Kidney Biopsies Performed in COVID-19 Patients Presenting With Acute Kidney Injury or Proteinuria.

RATIONALE & OBJECTIVE: Kidney biopsy data inform us about pathologic processes associated with infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We conducted a multicenter evaluation of kidney biopsy findings in living patients to identify various kidney disease pathology findings in patients with coronavirus disease 2019 (COVID-19) and their association with SARS-CoV-2 infection. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: We identified 14 native and 3 transplant kidney biopsies performed for cause in patients with documented recent or concurrent SARS-CoV-2 infection treated at 7 large hospital systems in the United States. OBSERVATIONS: Men and women were equally represented in this case series, with a higher proportion of Black (n=8) and Hispanic (n=5) patients. All 17 patients had SARS-CoV-2 infection confirmed by reverse transcriptase-polymerase chain reaction, but only 3 presented with severe COVID-19 symptoms. Acute kidney injury (n=15) and proteinuria (n=11) were the most common indications for biopsy and these symptoms developed concurrently or within 1 week of COVID-19 symptoms in all patients. Acute tubular injury (n=14), collapsing glomerulopathy (n=7), and endothelial injury/thrombotic microangiopathy (n=6) were the most common histologic findings. 2 of the 3 transplant recipients developed active antibody-mediated rejection weeks after COVID-19. 8 patients required dialysis, but others improved with conservative management. LIMITATIONS: Small study size and short clinical follow-up. CONCLUSIONS: Cases of even symptomatically mild COVID-19 were accompanied by acute kidney injury and/or heavy proteinuria that prompted a diagnostic kidney biopsy. Although acute tubular injury was seen among most of them, uncommon pathology such as collapsing glomerulopathy and acute endothelial injury were detected, and most of these patients progressed to irreversible kidney injury and dialysis.

Fibrillary Glomerulonephritis: Clinicopathologic Features and Atypical Cases from a Multi-Institutional Cohort.

BACKGROUND AND OBJECTIVES: Fibrillary GN has been defined as an immune complex-mediated GN with amyloid-like fibrils larger than amyloid which are IgG positive and Congo red negative. With discovery of DNAJB9 as a highly sensitive and specific marker for fibrillary GN, the specificity of the morphologic criteria for establishing the diagnosis of fibrillary GN has come into question. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We sought to (1) determine anatomic characteristics that best define fibrillary GN and (2) identify clinical and pathologic features that predict outcomes. RESULTS: We retrospectively reviewed kidney biopsies from patients diagnosed with fibrillary GN or suspected fibrillary GN between 1997 and 2017 (n=266, 65% female, median age 61). Approximately 11% of kidney biopsies had one or more unusual feature including monotypic deposits, Congo red positivity, or unusual fibril diameter. Fibrillary GN as a possible monoclonal gammopathy of renal significance represented <1% of cases. Immunostaining for DNAJB9 confirmed fibrillary GN in 100% of cases diagnosed as fibrillary GN and 79% of atypical cases diagnosed as possible fibrillary GN. At a median time of 24 months (interquartile range, 8-46 months) after biopsy (n=100), 53% of patients reached the combined primary outcome of ESKD or death, 18% had CKD, and 18% had partial remission. On multivariable analysis, male sex (adjusted hazard ratio [aHR], 3.82; 95% confidence interval [95% CI], 1.97 to 7.37) and eGFR were the most significant predictors of primary outcome (aHR of 8.02 if eGFR <30 ml/min per 1.73 m2 [95% CI, 1.85 to 34.75]; aHR of 6.44 if eGFR 30 to <45 ml/min per 1.73 m2 [95% CI, 1.38 to 29.99]). Immunosuppressive therapy with rituximab was significantly associated with stabilization of disease progression. CONCLUSIONS: Detection of DNAJB9 is a useful diagnostic tool for diagnosing atypical forms of fibrillary GN. The outcomes for fibrillary GN are poor and progression to ESKD is influenced predominantly by the degree of kidney insufficiency at the time of diagnosis and male sex. Rituximab may help preserve kidney function for select patients with fibrillary GN. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_11_04_CJN03870319.mp3.

Integrated epigenomic profiling reveals endogenous retrovirus reactivation in renal cell carcinoma.

BACKGROUND: Transcriptional dysregulation drives cancer formation but the underlying mechanisms are still poorly understood. Renal cell carcinoma (RCC) is the most common malignant kidney tumor which canonically activates the hypoxia-inducible transcription factor (HIF) pathway. Despite intensive study, novel therapeutic strategies to target RCC have been difficult to develop. Since the RCC epigenome is relatively understudied, we sought to elucidate key mechanisms underpinning the tumor phenotype and its clinical behavior. METHODS: We performed genome-wide chromatin accessibility (DNase-seq) and transcriptome profiling (RNA-seq) on paired tumor/normal samples from 3 patients undergoing nephrectomy for removal of RCC. We incorporated publicly available data on HIF binding (ChIP-seq) in a RCC cell line. We performed integrated analyses of these high-resolution, genome-scale datasets together with larger transcriptomic data available through The Cancer Genome Atlas (TCGA). FINDINGS: Though HIF transcription factors play a cardinal role in RCC oncogenesis, we found that numerous transcription factors with a RCC-selective expression pattern also demonstrated evidence of HIF binding near their gene body. Examination of chromatin accessibility profiles revealed that some of these transcription factors influenced the tumor's regulatory landscape, notably the stem cell transcription factor POU5F1 (OCT4). Elevated POU5F1 transcript levels were correlated with advanced tumor stage and poorer overall survival in RCC patients. Unexpectedly, we discovered a HIF-pathway-responsive promoter embedded within a endogenous retroviral long terminal repeat (LTR) element at the transcriptional start site of the PSOR1C3 long non-coding RNA gene upstream of POU5F1. RNA transcripts are induced from this promoter and read through PSOR1C3 into POU5F1 producing a novel POU5F1 transcript isoform. Rather than being unique to the POU5F1 locus, we found that HIF binds to several other transcriptionally active LTR elements genome-wide correlating with broad gene expression changes in RCC. INTERPRETATION: Integrated transcriptomic and epigenomic analysis of matched tumor and normal tissues from even a small number of primary patient samples revealed remarkably convergent shared regulatory landscapes. Several transcription factors appear to act downstream of HIF including the potent stem cell transcription factor POU5F1. Dysregulated expression of POU5F1 is part of a larger pattern of gene expression changes in RCC that may be induced by HIF-dependent reactivation of dormant promoters embedded within endogenous retroviral LTRs.

IgA-dominant glomerulonephritis with a membranoproliferative pattern of injury.

Immunoglobulin A (IgA)-dominant membranoproliferative glomerulonephritis (MPGN) is a descriptive term for renal biopsies in which differential diagnoses of unusual IgA nephropathy (IgAN), infection-related GN, or other etiologies are considered. We sought to understand clinical and pathologic features of this finding. Native kidney biopsies with IgA-dominant immune deposits and diffuse MPGN features without significant exudative features or subepithelial deposits were retrospectively reviewed. Two groups (n = 27, 33 biopsies) were identified: patients with chronic liver disease and those without. Patients without chronic liver disease (n = 15) were men (73%, age 40) who presented with nephrotic-range proteinuria, hematuria, renal insufficiency, negative serologic studies, and no history of infection. At a median interval of 3 years, 11 had available follow-up information. Three (27%) progressed to end-stage renal disease. One had recurrent IgA-dominant GN in the renal allograft less than 1 year posttransplant. Four of 5 patients with repeat biopsies had persistent IgA-dominant MPGN. Patients with chronic liver disease (n = 12) had similar biopsy findings, but 42% had concurrent infections, some occult. At a median interval of 7 weeks, 8 patients (80% of those with follow-up) had died and 2 were dialysis dependent. In conclusion, IgA-dominant MPGN was seen in 2 clinical cohorts in this study. In patients without chronic liver disease, this appears to represent either a unique clinicopathologic entity with a poorer prognosis than IgAN or an aggressive variant of IgAN. Patients with chronic liver disease often have underlying infection, and regardless of treatment, die within 1 year because of complex medical conditions.

A 3D Human Renal Cell Carcinoma-on-a-Chip for the Study of Tumor Angiogenesis.

Tractable human tissue-engineered 3D models of cancer that enable fine control of tumor growth, metabolism, and reciprocal interactions between different cell types in the tumor microenvironment promise to accelerate cancer research and pharmacologic testing. Progress to date mostly reflects the use of immortalized cancer cell lines, and progression to primary patient-derived tumor cells is needed to realize the full potential of these platforms. For the first time, we report endothelial sprouting induced by primary patient tumor cells in a 3D microfluidic system. Specifically, we have combined primary human clear cell renal cell carcinoma (ccRCC) cells from six independent donors with human endothelial cells in a vascularized, flow-directed, 3D culture system ("ccRCC-on-a-chip"). The upregulation of key angiogenic factors in primary human ccRCC cells, which exhibited unique patterns of donor variation, was further enhanced when they were cultured in 3D clusters. When embedded in the matrix surrounding engineered human vessels, these ccRCC tumor clusters drove potent endothelial cell sprouting under continuous flow, thus recapitulating the critical angiogenic signaling axis between human ccRCC cells and endothelial cells. Importantly, this phenotype was driven by a primary tumor cell-derived biochemical gradient of angiogenic growth factor accumulation that was subject to pharmacological blockade. Our novel 3D system represents a vascularized tumor model that is easy to image and quantify and is fully tunable in terms of input cells, perfusate, and matrices. We envision that this ccRCC-on-a-chip will be valuable for mechanistic studies, for studying tumor-vascular cell interactions, and for developing novel and personalized antitumor therapies.

B cell-derived IL-4 acts on podocytes to induce proteinuria and foot process effacement.

The efficacy of B cell depletion therapies in diseases such as nephrotic syndrome and rheumatoid arthritis suggests a broader role in B cells in human disease than previously recognized. In some of these diseases, such as the minimal change disease subtype of nephrotic syndrome, pathogenic antibodies and immune complexes are not involved. We hypothesized that B cells, activated in the kidney, might produce cytokines capable of directly inducing cell injury and proteinuria. To directly test our hypothesis, we targeted a model antigen to the kidney glomerulus and showed that transfer of antigen-specific B cells could induce glomerular injury and proteinuria. This effect was mediated by IL-4, as transfer of IL-4-deficient B cells did not induce proteinuria. Overexpression of IL-4 in mice was sufficient to induce kidney injury and proteinuria and could be attenuated by JAK kinase inhibitors. Since IL-4 is a specific activator of STAT6, we analyzed kidney biopsies and demonstrated STAT6 activation in up to 1 of 3 of minimal change disease patients, suggesting IL-4 or IL-13 exposure in these patients. These data suggest that the role of B cells in nephrotic syndrome could be mediated by cytokines.