Mitigation of Checkpoint Inhibitor-Induced Autoimmune Hemolytic Anemia through Modulation of Purinergic Signaling.

Immune checkpoint inhibitors (ICPi) have revolutionized cancer immunotherapy but also can induce autoimmune hemolytic anemia (AIHA), a severe disease with high mortality. However, the cellular and molecular mechanism(s) of ICPi-AIHA are unclear, other than being initiated through decreased checkpoint inhibition. Herein, we report ICPi-AIHA in a novel mouse model that shows similar characteristics of known human ICPi-AIHA (e.g., autoantibodies, hemolysis, increased mortality). During ICPi-AIHA, there is the simultaneous reduction of two regulatory T cell populations (FoxP3+ and Tr1 Tregs) and an increase in inflammatory TH17 T cells. Moreover, a novel CD39+CD73-FoxP3-CD25- CD4+ T cell subset (i.e., CD39 single positive [CD39SP]) emerges, and early increases in CD39SP predict AIHA development; CD39 is an ectonuclease that breaks down ATP. Additionally, we found that boosting ATPase activity by injecting recombinant apyrase mitigates AIHA development and significant CD39SP reductions, both suggesting a functional role for CD39 and demonstrating a novel therapeutic approach. Importantly, CD39SP are detectable in multiple mouse models developing AIHA and in patients with AIHA, demonstrating applicability to idiopathic and secondary AIHA. Highlighting broader autoimmunity relevance, ICPi-treated NZB mice experienced accelerated onset and severity of lupus, including AIHA. Moreover, ICPi treatment of healthy B6 animals led to detectable CD39SP and development of autoantibodies against multiple autoantigens including those on red blood cells and platelets. Together, our findings elucidate cellular and molecular mechanisms of ICPi-AIHA, leading to novel diagnostic and therapeutic approaches with translational potential for use in humans being treated with ICPi.

Chronic kidney disease in a murine model of non-alcoholic steatohepatitis (NASH).

Clinical studies suggest that non-alcoholic steatohepatitis (NASH) is an independent risk factor for chronic kidney disease (CKD), but causality and mechanisms linking these two major diseases are lacking. To assess whether NASH can induce CKD, we have characterized kidney function, histological features, transcriptomic and lipidomic profiles in a well-validated murine NASH model. Mice with NASH progressively developed significant podocyte foot process effacement, proteinuria, glomerulosclerosis, tubular epithelial cell injury, lipid accumulation, and interstitial fibrosis. The progression of kidney fibrosis paralleled the severity of the histologic NASH-activity score. Significantly, we confirmed the causal link between NASH and CKD by orthotopic liver transplantation, which attenuated proteinuria, kidney dysfunction, and fibrosis compared with control sham operated mice. Transcriptomic analysis of mouse kidney cortices revealed differentially expressed genes that were highly enriched in mitochondrial dysfunction, lipid metabolic process, and insulin signaling pathways in NASH-induced CKD. Lipidomic analysis of kidney cortices further revealed that phospholipids and sphingolipids were the most significantly changed lipid species. Notably, we found similar kidney histological changes in human NASH and CKD. Thus, our results confirm a causative role of NASH in the development of CKD, reveal potential pathophysiologic mechanisms of NASH-induced kidney injury, and established a valuable model to study the pathogenesis of NASH-associated CKD. This is an important feature of fatty liver disease that has been largely overlooked but has clinical and prognostic importance.

Targeting WIP1 phosphatase promotes partial remission in experimental collapsing glomerulopathy.

Collapsing focal segmental glomerulosclerosis (FSGS), also known as collapsing glomerulopathy (CG), is the most aggressive variant of FSGS and is characterized by a rapid progression to kidney failure. Understanding CG pathogenesis represents a key step for the development of targeted therapies. Previous work implicated the telomerase protein component TERT in CG pathogenesis, as transgenic TERT expression in adult mice resulted in a CG resembling that seen in human primary CG and HIV-associated nephropathy (HIVAN). Here, we used the telomerase-induced mouse model of CG (i-TERTci mice) to identify mechanisms to inhibit CG pathogenesis. Inactivation of WIP1 phosphatase, a p53 target acting in a negative feedback loop, blocked disease initiation in i-TERTci mice. Repression of disease initiation upon WIP1 deficiency was associated with senescence enhancement and required transforming growth factor-ß functions. The efficacy of a pharmacologic treatment to reduce disease severity in both i-TERTci mice and in a mouse model of HIVAN (Tg26 mice) was then assessed. Pharmacologic inhibition of WIP1 enzymatic activity in either the telomerase mice with CG or in the Tg26 mice promoted partial remission of proteinuria and ameliorated kidney histopathologic features. Histological as well as high-throughput sequencing methods further showed that selective inhibition of WIP1 does not promote kidney fibrosis or inflammation. Thus, our findings suggest that targeting WIP1 may be an effective therapeutic strategy for patients with CG.

Podocyte density as a predictor of long-term kidney outcome in obesity-related glomerulopathy.

Glomerulomegaly and focal segmental glomerulosclerosis are histopathological hallmarks of obesity-related glomerulopathy (ORG). Podocyte injury and subsequent depletion are regarded as key processes in the development of these glomerular lesions in patients with ORG, but their impact on long-term kidney outcome is undetermined. Here, we correlated clinicopathological findings and podocyte depletion retrospectively in patients with ORG. Relative (podocyte density) and absolute (podocyte number per glomerulus) measures of podocyte depletion were estimated using model-based stereology in 46 patients with ORG. The combined endpoint of kidney outcomes was defined as a 30% decline in estimated glomerular filtration rate (eGFR) or kidney failure. Patients with lower podocyte density were predominantly male and had larger body surface area, greater proteinuria, fewer non-sclerotic glomeruli, larger glomeruli and higher single-nephron eGFR. During a median follow-up of 4.1 years, 18 (39%) patients reached endpoint. Kidney survival in patients with lower podocyte density was significantly worse than in patients with higher podocyte density. However, there was no difference in kidney survival between patient groups based on podocyte number per glomerulus. Cox hazard analysis showed that podocyte density, but not podocyte number per glomerulus, was associated with the kidney outcomes after adjustment for clinicopathological confounders. Thus, our study demonstrates that a relative depletion of podocytes better predicts long-term kidney outcomes than does absolute depletion of podocytes. Hence, the findings implicate mismatch between glomerular enlargement and podocyte number as a crucial determinant of disease progression in ORG.

Clinicopathologic Characteristics of Crystalglobulin-Induced Nephropathy: A Case Series.

RATIONALE & OBJECTIVE: Crystalglobulinemia is a rare syndrome characterized by intravascular crystallization of monoclonal immunoglobulins (MIg). Data on kidney involvement are limited to case reports. This series characterizes the clinicopathologic spectrum of crystalglobulin-induced nephropathy (CIN). STUDY DESIGN: Case series. SETTING & PARTICIPANTS: Nineteen CIN cases identified from the nephropathology archives of Mayo Clinic and Columbia University. CIN was defined by intravascular (extracellular) MIg crystals visible by light microscopy (LM) and electron microscopy (EM). RESULTS: Among the cases, 68% were male, and 65% were Caucasian (median age, 56 years). Most patients presented with severe acute kidney injury (AKI) (median creatinine, 3.5mg/dL), hematuria, and mild proteinuria (median, 1.1g/day). Common extrarenal manifestations were constitutional (67%), cutaneous (56%), and rheumatologic (50%). Fifty percent of cases had hypocomplementemia. The hematologic disorders were monoclonal gammopathy of renal significance (MGRS) (72%), lymphoma (17%), or myeloma (11%), with 65% of these disorders discovered concomitantly with CIN. All patients had MIg identified on serum protein electrophoresis/immunofixation (IgGκ in 65%). The serum free light chain ratio was outside the renal range in 40%, and bone marrow biopsy detected the responsible clone in 67%. On LM, crystals involved glomeruli (100%) and vessels (47%), often with an inflammatory reaction (89%) and fibrin (58%). All cases exhibited crystal substructures (mostly paracrystalline) by EM. Immunofluorescence on paraffin-embedded tissue was more sensitive than frozen tissue (92% vs 47%) for demonstrating the crystal composition (IgGκ in 63%). Follow-up observation (median, 20 months) was available in 16 patients. Eighty-one percent received steroids, 44% plasmapheresis, 38% hemodialysis, and 69% chemotherapy. Ninety-percent of patients who received clone-directed therapy achieved kidney recovery versus 20% of those who did not (P=0.02). LIMITATIONS: Retrospective design, small sample size. CONCLUSIONS: CIN is a rare cause of nephropathy associated with lymphoplasmacytic disorders (mostly MGRS) and typically presents with severe AKI and extrarenal manifestations. Diagnosis often requires immunofluorescence performed on paraffin-embedded kidney tissue. Prompt initiation of clone-directed therapy, coupled with corticosteroids and plasmapheresis, may lead to recovery of kidney function.

Collapsing glomerulopathy is likely a major contributing factor for worse allograft survival in patients receiving kidney transplants from black donors.

Although a few registry-based studies have shown associations between receiving kidney allografts from Black donors and shorter allograft survival, detailed, large, single-center studies accounting for common confounding factors are lacking. Furthermore, pathologic alterations underlying this potential disparity have not been systematically studied. We performed a retrospective clinical-pathological study of kidney transplant recipients who received kidney allografts from either Black (n = 407) or White (n = 1,494) donors at Columbia University Irving Medical Center from 2005 to 2018, with median follow-up of 4.5 years post-transplantation. Black donor race was independently associated with allograft failure (adjusted HR = 1.34, p = 0.02) and recipients of kidney allografts from Black donors had a higher incidence of collapsing glomerulopathy [7.4% vs. 1.9%, OR = 4.17, p < 0.001]. When causes of allograft failure were examined, only allograft failure following development of collapsing glomerulopathy was more frequent in recipients of allografts from Black donors [15% vs. 5%, OR = 3.16, p = 0.004]. Notably, when patients who developed collapsing glomerulopathy were excluded from analysis, receiving kidney allografts from Black donors was not independently associated with allograft failure (adjusted HR = 1.24, p = 0.10). These findings revealed that, compared with recipients of kidney allografts from White donors, recipients of kidneys from Black donors have modestly shorter allograft survival and a higher probability of developing collapsing glomerulopathy, which negatively impacts allograft outcome. Identification of collapsing glomerulopathy risk factors may help decrease this complication and improve allograft survival, which optimally may reduce racial disparities post-transplantation.

Kidney Dysfunction and Pathology in the Setting of Hemophagocytic Lymphohistiocytosis.

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a clinicopathologic syndrome produced by dysregulated activation of the immune system. Acute kidney injury (AKI) and proteinuria have been infrequently described in the setting of HLH, and investigations of underlying histopathologic changes in the kidney are limited. Methods: To characterize kidney pathology in HLH, a retrospective review of 30 patients' clinical and laboratory data, and kidney tissue was performed (18 from autopsy, and 12 biopsied patients). Results: HLH was associated with infection (83%), autoimmune disease (37%), and malignancy (20%), including 30% with concurrent autoimmune disease and infection. Nephrological presentations included subnephrotic range proteinuria (63%), AKI (63%), hematuria (33%), chronic kidney disease (CKD, 20%), nephrotic range proteinuria (13%), and nephrotic syndrome (7%); and 40% of patients required hemodialysis (HD). Among the 12 patients who underwent kidney biopsy, 6 subsequently showed improved kidney function and the remainder had progressive CKD with most progressing to end-stage kidney disease. Autopsy patients had a median terminal admission of 1 month, and 33% of the biopsied patients died (ranging from 0.3-5 months post-biopsy). Variable pathologies were identified, including acute tubular injury (ATI, 43%), lupus nephritis (LN, 23%), collapsing glomerulopathy (17%), thrombotic microangiopathy (TMA, 17%), and cortical necrosis (10%). Most autopsied patients had significant kidney pathology other than ATI that likely contributed to kidney function decline. A majority of patients with HLH exhibited kidney dysfunction that likely contributed to the poor prognosis. Conclusion: Kidney dysfunction in HLH should not be assumed to be solely attributable to ATI, and in certain scenarios a kidney biopsy may be warranted.