Search

In the abstract and the legend for Figure 1, the descriptions of the Olink Proteomics assays utilized were incorrect. The correct descriptions appear below. The HTML and PDF versions of [...]

Background: Podocyte foot process effacement is a key histologic finding in proteinuric kidney disease. We previously showed that 3-week old CD2AP-deficient mice have significant proteinuria, glomerular hypertrophy and mesangial expansion. The goal of this study is to use morphometry to establish the temporal sequence of podocyte foot process effacement, glomerular volume expansion and albuminuria in Cd2ap -/- mice by measuring these parameters at the 2-week time point. Methods: Wild-type mice age 14 ± 1 days with the Cd2ap gene (WT, N = 5) and mice deficient for Cd2ap (Cd2ap KO, N = 5) were generated. Kidneys were harvested and fixed in 2.5% glutaraldehyde and processed for examination by light and electron microscopy. An average of 415.2 (range 268-716) grid points were counted for all the glomeruli, and quantification of glomerular volume from each kidney. Urine was collected the day prior to sacrifice for urine albumin-to-creatinine ratio (ACR) measurements. Results: There was no difference in albuminuria [median (range) mg/g] between WT [212.2 (177.6-388.4) mg/g] vs. Cd2ap KO mice [203.3 (164.7-910.2) mg/g], P = 0.89; or glomerular volume 68,307[10,931] vs. 66,844[13,022] μm3, p = 0.92. The volume densities of glomerular components of the podocyte, capillary lumen and mesangium were not different for the two groups, P = 0.14, 0.14 and 0.17 respectively. However, foot process width was increased in Cd2ap KO 1128[286] vs. WT [374 ± 42] nm, P = 0.02. Conclusion: Here we show that while 2-week old WT and Cd2ap KO mice have similar levels of albuminuria, glomerular and mesangial volume, Cd2ap KO mice have more extensive podocyte foot process effacement. The data suggests that podocyte injury is the initiating event leading to mesangial expansion and albuminuria in this model.

BACKGROUND. Acute tubulointerstitial nephritis (AIN) is one of the few causes of acute kidney injury with diagnosis- specific treatment options. However, due to the need to obtain a kidney biopsy for histological confirmation, AIN diagnosis can be delayed, missed, or incorrectly assumed. Here, we identify and validate urinary CXCL9, an IFN-[gamma]-induced chemokine involved in lymphocyte chemotaxis, as a diagnostic biomarker for AIN. METHODS. In a prospectively enrolled cohort with pathologist-adjudicated histological diagnoses, termed the discovery cohort, we tested the association of 180 immune proteins measured by an aptamer- based assay with AIN and validated the top protein, CXCL9, using sandwich immunoassay. We externally validated these findings in 2 cohorts with biopsy- confirmed diagnoses, termed the validation cohorts, and examined mRNA expression differences in kidney tissue from patients with AIN and individuals in the control group. RESULTS. In aptamer-based assay, urinary CXCL9 was 7.6-fold higher in patients with AIN than in individuals in the control group (P = 1.23 * [10.sup.-5]). Urinary CXCL9 measured by sandwich immunoassay was associated with AIN in the discovery cohort (n = 204; 15% AIN) independently of currently available clinical tests for AIN (adjusted odds ratio for highest versus lowest quartile: 6.0 [1.8-20]). Similar findings were noted in external validation cohorts, where CXCL9 had an AUC of 0.94 (0.86-1.00) for AIN diagnosis. CXCL9 mRNA expression was 3.9-fold higher in kidney tissue from patients with AIN (n = 19) compared with individuals in the control group (n = 52; P = 5.8 * [10.sup.-6]). CONCLUSION. We identified CXCL9 as a diagnostic biomarker for AIN using aptamer- based urine proteomics, confirmed this association using sandwich immunoassays in discovery and external validation cohorts, and observed higher expression of this protein in kidney biopsies from patients with AIN. FUNDING. This study was supported by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) awards K23DK117065 (DGM), K08DK113281 (KM), R01DK128087 (DGM), R01DK126815 (DGM and LGC), R01DK126477 (KNC), UH3DK114866 (CRP, DGM, and FPW), R01DK130839 (MES), and P30DK079310 (the Yale O'Brien Center). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health., Introduction Sudden loss of kidney function, termed acute kidney injury (AKI), is common, affecting 1 in 5 hospitalized patients and is associated with adverse long-term outcomes, including chronic kidney disease, [...]

Podocyte loss is central to the progression of proteinuric kidney diseases leading to end-stage kidney disease (ESKD), requiring renal replacement therapy, such as dialysis. Despite modern tools and techniques, the 5-year mortality of some patients requiring dialysis remains at about 70% to 80%. Thus, there is a great unmet need for podocyte-specific treatments aimed at preventing podocyte loss and the ensuing development of ESKD. Here, we show that ablation of the podocyte death-promoting protein dendrin delays the onset of ESKD, thereby expanding the life span of mice lacking the adapter protein CD2AP. Ablation of dendrin delays onset and severity of proteinuria and podocyte loss. In addition, dendrin ablation ameliorates mesangial volume expansion and up-regulation of mesangial fibronectin expression, which is mediated by a podocyte-secreted factor. In conclusion, onset of ESKD and death can be markedly delayed by blocking the function of dendrin.

Abatacept (cytotoxic T-lymphocyte-associated antigen 4-immunoglobulin fusion protein [CTLA-4-Ig]) is a costimulatory inhibitor that targets B7-1 (CD80). The present report describes five patients who had focal segmental glomerulosclerosis (FSGS) (four with recurrent FSGS after transplantation and one with primary FSGS) and proteinuria with B7-1 immunostaining of podocytes in kidney-biopsy specimens. Abatacept induced partial or complete remissions of proteinuria in these patients, suggesting that B7-1 may be a useful biomarker for the treatment of some glomerulopathies. Our data indicate that abatacept may stabilize β1-integrin activation in podocytes and reduce proteinuria in patients with B7-1-positive glomerular disease.

Dachshund homolog 1 (DACH1), a key cell-fate determinant, regulates transcription by DNA sequence-specific binding. We identified diminished Dach1 expression in a large-scale screen for mutations that convert injury-resistant podocytes into injury-susceptible podocytes. In diabetic kidney disease (DKD) patients, podocyte DACH1 expression levels are diminished, a condition that strongly correlates with poor clinical outcomes. Global Dach1 KO mice manifest renal hypoplasia and die perinatally. Podocyte-specific Dach1 KO mice, however, maintain normal glomerular architecture at baseline, but rapidly exhibit podocyte injury after diabetes onset. Furthermore, podocyte-specific augmentation of DACH1 expression in mice protects from DKD. Combined RNA sequencing and in silico promoter analysis reveal conversely overlapping glomerular transcriptomic signatures between podocyte-specific Dach1 and Pax transactivation-domain interacting protein (Ptip) KO mice, with upregulated genes possessing higher-than-expected numbers of promoter Dach7-binding sites. PTIP, an essential component of the activating histone H3 lysine 4 trimethylation (H3K4Me3) complex, interacts with DACH1 and is recruited by DACH1 to its promoter-binding sites. DACH1-PTIP recruitment represses transcription and reduces promoter H3K4Me3 levels. DACH1 knockdown in podocytes combined with hyperglycemia triggers target gene upregulation and increases promoter H3K4Me3. These findings reveal that in DKD, diminished DACH1 expression enhances podocyte injury vulnerability via epigenetic derepression of its target genes., Introduction Dachshund homolog 1 (DACH1) was originally identified as an essential member of the retinal determination gene network (RDGN), a fundamental signal that governs cell fate during development. That DACH1 [...]

Injury to the specialized epithelial cells of the glomerulus (podocytes) underlies the pathogenesis of all forms of proteinuric kidney disease; however, the specific genetic changes that mediate podocyte dysfunction after injury are not fully understood. Here, we performed a large-scale insertional mutagenic screen of injury-resistant podocytes isolated from mice and found that increased expression of the gene Rap1gap, encoding a RAP1 activation inhibitor, ameliorated podocyte injury resistance. Furthermore, injured podocytes in murine models of disease and kidney biopsies from glomerulosclerosis patients exhibited increased RAP1GAP, resulting in diminished glomerular RAP1 activation. In mouse models, podocyte-specific inactivation of Rap1a and Rap1b induced massive glomerulosclerosis and premature death. Podocyte-specific Rap1a and Rap1b haploinsufficiency also resulted in severe podocyte damage, including features of podocyte detachment. Over-expression of RAP1GAP in cultured podocytes induced loss of activated [beta]1 integrin, which was similarly observed in kidney biopsies from patients. Furthermore, preventing elevation of RAP1GAP levels in injured podocytes maintained [beta]1 integrin-mediated adhesion and prevented cellular detachment. Taken together, our findings suggest that increased podocyte expression of RAP1GAP contributes directly to podocyte dysfunction by a mechanism that involves loss of RAP1-mediated activation of [beta]1 integrin., Introduction Podocytes, the terminally differentiated visceral epithelial cells of the glomerulus, are responsible for forming and regulating the kidney filtration barrier. These cells have a remarkably complex cellular morphology, extending [...]

A crucial reckoning was initiated when the COVID-19 pandemic began to expose and intensify long-standing racial/ethnic health inequities, all while various sectors of society pursued racial justice reform. As a result, there has been a contextual shift towards broader recognition of systemic racism, and not race, as the shared foundational driver of both societal maladies. This confluence of issues is of particular relevance to Black populations disproportionately affected by the pandemic and racial injustice. In response, institutions have initiated diversity, equity, and inclusion (DEI) efforts as a way forward. This article considers how the dual pandemic climate of COVID-19-related health inequities and the racial justice movement could exacerbate the "time and effort tax" on Black faculty to engage in DEI efforts in academia and biomedicine. We discuss the impact of this "tax" on career advancement and well-being, and introduce an operational framework for considering the interconnected influence of systemic racism, the dual pandemics, and DEI work on the experience of Black faculty. If not meaningfully addressed, the "time and effort tax" could contribute to Black and other underrepresented minority faculty leaving academia and biomedicine – consequently, the very diversity, equity, and inclusion work meant to increase representation could decrease it. [ABSTRACT FROM AUTHOR]