Transcriptional reprogramming has an important role in kidney glomerular disease. Using in vivo murine models of podocyte injury, we studied the roles of the FOXC2 and WT1 transcription factors (TFs) in podocyte injury. Podocytes are a crucial cell type of glomeruli, the filtration units of each nephron. Podocyte injury is often the incipient event leading to chronic kidney disease. It is well established that the TFs FOXC2 and WT1 are required in podocytes to maintain the glomerular filtration barrier. Their role in the response to injury is less well understood. Here, we tested the hypothesis that FOXC2 and WT1 act together to mediate transcriptional reprogramming in response to podocyte injury. Similarly to that of WT1, genome-wide FOXC2 binding to target genes is dynamic during the course of injury, initially increasing, but late in injury there is a dramatic decrease in FOXC2 expression and in its binding to target genes. Podocyte-specific inactivation of FoxC2 or Wt1 in adult mice limits the transcriptional response to injury. Correlating FOXC2 and WT1 ChIP-seq analyses demonstrated that they co-bind many genes expressed in podocytes. Thus, reprogramming the transcriptome involves dynamic changes in the binding of FOXC2 and WT1 to their target genes during a reparative injury response.

Severe proteinopathies-such as retinitis pigmentosa, a form of inherited blindness-are driven by genetic mutations that overwhelm the quality control of the post-endoplasmic reticulum (post-ER) secretory pathway, causing toxic protein accumulation. Here, we identify a therapeutic node defined by a hetero-oligomeric cargo receptor complex consisting of TMED7, 2, 9, and 10. This "entrapment complex" anchors structurally and functionally diverse mutant clients within the early secretory pathway via TMED7 binding to the integral Golgi protein GRASP55. Disruption of the entrapment complex results in the clearance of accumulated protein cargoes. In vivo ablation of the entrapment node via inducible genetic deletion or via the small molecule BRD7635 reverses histopathological hallmarks and rescues functional deficits in clinically distinct proteinopathies of the kidney and the eye, including mitigating vision loss in a mouse model of retinitis pigmentosa.

The kidney glomerulus is a filtration barrier in which capillary loop architecture depends on epithelial-stromal interactions between podocytes and mesangial cells. Podocytes are terminally differentiated cells within the glomerulus that express YAP and TAZ. Here we test the hypotheses that YAP and TAZ are required in podocytes to maintain capillary loop architecture and that shifts in the integrin repertoire during podocyte injury affect transcriptional activity of YAP and TAZ. Loss of YAP in podocytes of adult mice renders them more sensitive to injury, whereas loss of both YAP and TAZ in podocytes rapidly compromises the filtration barrier. α3β1 and αvβ5 are two prominent integrins on murine podocytes. Podocyte injury or loss of α3β1 leads to increased abundance of αvβ5 and nuclear localization of YAP. In vitro, blockade of αvβ5 decreases nuclear YAP. Increased αv integrins are found in human kidney disease. Thus, our studies demonstrate the crucial regulatory interplay between cell adhesion and transcriptional regulation as an important determinant of human disease.

Introduction:Minimal change disease (MCD) is a common cause of nephrotic syndrome in children and adults. Immune dysregulation is a contributor, but the relative roles of individual components of the immune system in MCD pathogenesis remain unclear. Case Presentation:Here, we present 2 patients with defects in immune tolerance mechanisms that developed MCD associated with anti-nephrin antibodies. The first patient had a pathogenic deletion in FOXP3, leading to reduced regulatory T cells. Serum could not be obtained from this patient during the active phase of MCD to directly establish the presence of anti-nephrin antibodies. However, this patient demonstrated IgG dusting over podocyte cell bodies by immunofluorescence microscopy, as well as colocalization of IgG with nephrin in confocal microscopy. The second patient developed MCD in the context of immune checkpoint inhibitor treatment for metastatic carcinoma. Anti-nephrin antibodies were detected in this patient during active disease. The patient's kidney biopsy also showed evidence of binding of anti-nephrin antibodies within the glomeruli. Conclusion:These cases demonstrate that genetic and iatrogenic mechanisms of breakdown in peripheral tolerance can lead to MCD.

Minimal change disease (MCD) is a major cause of adult-onset nephrotic syndrome, particularly in Japan where it affects 40% of patients compared with15% of patients world-wide.1 Its incidence is particularly high among the elderly and both the disease and corticosteroid therapy can be a major cause of morbidity in this population.

Diabetic kidney disease (DKD), the most common cause of kidney failure, is a frequent complication of diabetes and obesity, and yet to date, treatments to halt its progression are lacking. We analyze kidney single -cell transcriptomic profiles from DKD patients and two DKD mouse models at multiple time points along disease progression-high-fat diet (HFD)-fed mice aged to 90-100 weeks and BTBR ob/ob mice (a genetic model)-and report an expanding population of macrophages with high expression of triggering receptor expressed on myeloid cells 2 ( TREM2 ) in HFD-fed mice. TREM2 `"'` macrophages are enriched in obese and diabetic patients, in contrast to hypertensive patients or healthy controls in an independent validation cohort. Trem2 knockout mice on an HFD have worsening kidney filter damage and increased tubular epithelial cell injury, all signs of worsening DKD. Together, our studies suggest that strategies to enhance kidney TREM2 `"'` macrophages may provide therapeutic benefits for DKD.

Autosomal dominant tubulointerstitial kidney disease (ADTKD) represents a rare, yet clinically significant genetic disorder characterized by progressive kidney dysfunction. This condition arises from mutations in proteins crucial for maintaining normal kidney function, such as uromodulin (UMOD). Rare UMOD variants lead to the production of misfolded UMOD proteins, which initiate a cascade of events resulting in their aggregation, accumulation within renal tubules, and ultimately kidney dysfunction.

Minimal change disease and primary focal segmental glomerulosclerosis (FSGS) have similar clinical manifestations, both presenting with rapid-onset nephrotic syndrome and often amendable to treatment with high-dose glucocorticoids. Recently, antinephrin antibodies (Ab) have been reported to be present in a subset of patients with minimal change disease as well as in patients with primary FSGS with recurrent massive proteinuria after kidney transplantation.1-3 Infusion of antinephrin Ab in mice results in rapid-onset proteinuria and subsequent FSGS lesions.

The trafficking dynamics of uromodulin (UMOD), the most abundant protein in human urine, play a critical role in the pathogenesis of kidney disease. Monoallelic mutations in the UMOD gene cause autosomal dominant tubulointerstitial kidney disease (ADTKD-UMOD), an incurable genetic disorder that leads to kidney failure. The disease is caused by the intracellular entrapment of mutant UMOD in kidney epithelial cells, but the precise mechanisms mediating disrupted UMOD trafficking remain elusive. Here, we report that transmembrane Emp24 protein transport domain-containing (TMED) cargo receptors TMED2, TMED9, and TMED10 bind UMOD and regulate its trafficking along the secretory pathway. Pharmacological targeting of TMEDs in cells, in human kidney organoids derived from patients with ADTKD-UMOD, and in mutant-UMOD-knockin mice reduced intracellular accumulation of mutant UMOD and restored trafficking and localization of UMOD to the apical plasma membrane. In vivo, the TMED-targeted small molecule also mitigated ER stress and markers of kidney damage and fibrosis. Our work reveals TMED-targeting small molecules as a promising therapeutic strategy for kidney proteinopathies.

Background: The administration of modified immune cells (MIC) prior to kidney transplantation led to specific immunosuppression against the allogeneic donor and a significant increase in regulatory B lymphocytes (Breg) (Morath et al., J Clin Invest 2020). We now wanted to investigate how this approach affects the clinical course of treated patients. Method(s): Clinical results of ten patients from a phase I clinical trial who had received MIC infusions before kidney transplantation were compared to results of 15 matched standard-risk recipients. Follow-up was until year five after surgery. Result(s): The 10 MIC patients had an excellent clinical course with stable kidney graft function and showed no donor-specific human leukocyte antigen antibodies (DSA) or acute rejections during follow-up. In contrast, 1 of 15 controls died and 5 of 15 controls developed DSA (log rank P = 0.046) (Figure 1 A, B). While the number of patients with a non-opportunistic infection did not differ significantly between groups (P = 0.36), opportunistic infections were reported more frequently in controls (log rank P = 0.033) (Figure 1 C). Compared to controls, MIC patients were found to have a trend towards a higher COVID-19 anti-S1 IgG index after vaccination with a median of 53 vs. 2 (P = 0.16). Importantly, the four MIC patients who had received the highest MIC cell dose 7 days before surgery and were on low immunosuppression during follow-up, continued to show absent anti-donor T lymphocyte reactivity in vitro and high CD19+CD24hiCD38hi transitional Breg as well as CD19+CD24hiCD27+ memory Breg. Conclusion(s): MIC infusions together with reduced conventional immunosuppression were associated with lower de novo DSA development and lower rates of opportunistic infections. In the future, MIC infusions could contribute to graft protection while reducing the side effects of immunosuppressive therapy. (Figure Presented).

Background Failure of the glomerular filtration barrier, primarily by loss of slit diaphragm architecture, underlies nephrotic syndrome in minimal change disease. The etiology remains unknown. The efficacy of B cell-targeted therapies in some patients, together with the known proteinuric effect of anti-nephrin antibodies in rodent models, prompted us to hypothesize that nephrin autoantibodies may be present in patients with minimal change disease. Methods We evaluated sera from patients with minimal change disease, enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) cohort and from our own institutions, for circulating nephrin autoantibodies by indirect ELISA and by immunoprecipitation of full-length nephrin from human glomerular extract or a recombinant purified extracellular domain of human nephrin. We also evaluated renal biopsies from our institutions for podocyte-associated punctate IgG colocalizing with nephrin by immunofluorescence. Results In two independent patient cohorts, we identified circulating nephrin autoantibodies during active disease that were significantly reduced or absent during treatment response in a subset of patients with minimal change disease. We correlated the presence of these autoantibodies with podocyte-associated punctate IgG in renal biopsies from our institutions. We also identified a patient with steroid-dependent childhood minimal change disease that progressed to end stage kidney disease; she developed a massive post-transplant recurrence of proteinuria that was associated with high pretransplant circulating nephrin autoantibodies.Conclusions Our discovery of nephrin autoantibodies in a subset of adults and children with minimal change disease aligns with published animal studies and provides further support for an autoimmune etiology. We propose a new molecular classification of nephrin autoantibody minimal change disease to serve as a framework for instigation of precision therapeutics for these patients.

High-resolution spatial transcriptomics enables mapping of RNA expression directly from intact tissue sections; however, its utility for the elucidation of disease processes and therapeutically actionable pathways remains unexplored. We applied Slide-seqV2 to mouse and human kidneys, in healthy and distinct disease paradigms. First, we established the feasibility of Slide-seqV2 in tissue from nine distinct human kidneys, which revealed a cell neighborhood centered around a population of LYVE1+ macrophages. Second, in a mouse model of diabetic kidney disease, we detected changes in the cellular organization of the spatially restricted kidney filter and blood-flow-regulating apparatus. Third, in a mouse model of a toxic proteinopathy, we identified previously unknown, disease-specific cell neighborhoods centered around macrophages. In a spatially restricted subpopulation of epithelial cells, we discovered perturbations in 77 genes associated with the unfolded protein response. Our studies illustrate and experimentally validate the utility of Slide-seqV2 for the discovery of disease-specific cell neighborhoods.

Dysfunction of podocytes, cells critical for glomerular filtration, underlies proteinuria and kidney failure. Genetic forms of proteinuric kidney disease can be caused by mutations in several podocyte genes, including nephrin, a critical component of the kidney filter. In contrast, the etiology of acquired acute-onset nephrotic syndrome has remained elusive. Here we identify autoantibodies against nephrin in serum and glomeruli of a subset of adults and children with non-congenital acute nephrotic syndrome. Our findings align with published experimental animal studies and elucidate a novel autoimmune phenomenon in proteinuric kidney disease interfering with glomerular filter integrity.