Author Correction: Tubular cell and keratinocyte single-cell transcriptomics applied to lupus nephritis reveal type I IFN and fibrosis relevant pathways

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Standardized definitions for hemodialysis vascular access

Vascular access dysfunction is one of the leading causes of morbidity and mortality among end-stage renal disease patients. Vascular access dysfunction exists in all three types of available accesses: arteriovenous fistulas, arteriovenous grafts, and tunneled catheters. To improve clinical research and outcomes in hemodialysis (HD) access dysfunction, the development of a multidisciplinary network of collaborative investigators with various areas of expertise, and common standards for terminology and classification in all vascular access types, is required. The North American Vascular Access Consortium (NAVAC) is a newly formed multidisciplinary and multicenter network of experts in the area of HD vascular access, who include nephrologists and interventional nephrologists from the United States and Canada with: (1) a primary clinical and research focus in HD vascular access dysfunction, (2) national and internationally recognized experts in vascular access, and (3) a history of productivity measured by peer-reviewed publications and funding among members of this consortium. The consortium's mission is to improve the quality and efficiency in vascular access research, and impact the research in the area of HD vascular access by conducting observational studies and randomized controlled trials. The purpose of the consortium's initial manuscript is to provide working and standard vascular access definitions relating to (1) epidemiology, (2) vascular access function, (3) vascular access patency, and (4) complications in vascular accesses relating to each of the vascular access types.

Variants in the Wilms' tumor gene are associated with focal segmental glomerulosclerosis in the African American population

Wilms' tumor gene (WT1) is important for nephrogenesis and gonadal growth. WT1 mutations cause Denys-Drash and Frasier syndromes, which are characterized by glomerular scarring. To test whether genetic variations in WT1 and WIT1 (gene immediately 5' to WT1) associate with focal segmental glomerulosclerosis (FSGS), patients with biopsy-proven idiopathic and HIV-1-associated FSGS were enrolled in a multicenter study. We genotyped SNP rs6508 located in WIT1 exon 1, three SNPs (rs2301250, rs2301252, rs2301254) in the promoter shared by WT1 and WIT1, rs2234590 in exon 6, rs2234591 in intron 6, rs16754 in exon 7, and rs1799937 in intron 9 of WT1. Cases (n = 218) and controls (n = 281) were compared in the African American population. Stratification by HIV-1 infection status showed that SNPs rs6508, rs2301254, and rs1799937 were significantly associated with FSGS [rs6508 odds ratio (OR) 1.82, P = 0.006; rs2301254 OR 1.65, P = 0.049; rs1799937 OR 1.91, P = 0.005] in the non-HIV-1 group and rs2234591 (OR 0.234, P = 0.011) in the HIV-1 group. Haplotype analyses in the population revealed that seven SNPs were associated with FSGS; five SNPs had the highest contingency score [-log10(P value) = 13.57] in the HIV-1 group. This association could not be explained by population substructure. We conclude that SNPs in WT1 and WIT1 genes are significantly associated with FSGS, suggesting that variants in these genes may mediate pathogenesis by altering WT1 function. Furthermore, HIV-1 infection status interacts with genetic variations in both genes to influence this phenotype. We speculate that nephropathy liability alleles in WT1 pathway genes cause podocyte dysfunction and glomerular scarring.

Podocyte cell cycle regulation and proliferation in collapsing glomerulopathies

BACKGROUND

Mature podocytes are growth-arrested because of the expression of cyclin-dependent kinase inhibitors. Under pathological conditions, podocytes may undergo mitosis, but not cell division. Exceptions to this rule are collapsing glomerulopathies (CGs), including HIV-associated nephropathy (HIVAN) and idiopathic CG, where podocytes undergo a dysregulation of their differentiated phenotype and proliferate.

METHODS

To shed light on the mechanism underlying podocyte proliferation in CG, we analyzed the expression of the proliferation marker Ki-67, cyclins (A, D1), cyclin-dependent kinase inhibitors (p27, p57), and podocyte differentiation marker synaptopodin in eight cases of HIVAN and two cases of idiopathic CG. Normal fetal and adult kidneys served as controls.

RESULTS

Both HIVAN and idiopathic CG showed a marked reduction in the expression of p27, p57, and cyclin D1 (absent in 69, 62, and 80% of all glomeruli, respectively). Cyclin A and Ki-67 were expressed in 11 and 29% of all glomeruli. Moreover, there was partial loss of synaptopodin and cyclin D1 expression in nonaffected glomeruli.

CONCLUSIONS

The loss of p27 and p57 leading to expression of cyclin A may account for the activation of podocyte proliferation in CG. Furthermore, the loss of cyclin D1 from histologically normal glomeruli suggests a possible role of cyclin D1 in mediating the dysregulation of the podocyte cell cycle in CG. These novel findings offer insight into the molecular regulation of mature podocyte differentiation. Podocyte proliferation in CG provides evidence in support of a previously underestimated plasticity of mature podocytes.

Vasodilator provocation of occult urinary tract hemorrhage

This case demonstrates the use of vasodilators to reactivate an intermittent urinary tract hemorrhage. The site of bleeding was demonstrated and treated with subselective embolization.