Molecular Analysis of the Kidney From a Patient With COVID-19-Associated Collapsing Glomerulopathy

Abstract

Recent case reports suggest that coronavirus disease 2019 (COVID-19) is associated with collapsing glomerulopathy in African Americans with apolipoprotein L1 gene (APOL1) risk alleles; however, it is unclear whether disease pathogenesis is similar to HIV-associated nephropathy. RNA sequencing analysis of a kidney biopsy specimen from a patient with COVID-19-associated collapsing glomerulopathy and APOL1 risk alleles (G1/G1) revealed similar levels of APOL1 and angiotensin-converting enzyme 2 (ACE2) messenger RNA transcripts as compared with 12 control kidney samples downloaded from the GTEx (Genotype-Tissue Expression) Portal. Whole-genome sequencing of the COVID-19-associated collapsing glomerulopathy kidney sample identified 4 indel gene variants, 3 of which are of unknown significance with respect to chronic kidney disease and/or focal segmental glomerulosclerosis. Molecular profiling of the kidney demonstrated activation of COVID-19-associated cell injury pathways such as inflammation and coagulation. Evidence for direct severe acute respiratory syndrome coronavirus 2 infection of kidney cells was lacking, which is consistent with the findings of several recent studies. Interestingly, immunostaining of kidney biopsy sections revealed increased expression of phospho-STAT3 (signal transducer and activator of transcription 3) in both COVID-19-associated collapsing glomerulopathy and HIV-associated nephropathy as compared with control kidney tissue. Importantly, interleukin 6-induced activation of STAT3 may be a targetable mechanism driving COVID-19-associated acute kidney injury.

Keywords: APOL1; COVID-19; Collapsing glomerulopathy; FSGS; IL-6; STAT3.

Figure 1

Kidney biopsy of coronavirus disease 2019 (COVID-19)–associated collapsing glomerulopathy case. (A) Representative light microscopy shows collapse of glomerular tufts with hyperplasia of epithelial cells (hematoxylin-eosin; original magnification, ×400). (B) Another glomerulus shows collapse of capillary loops with proliferation of overlying epithelial cells (Jones methenamine silver stain; original magnification, ×200). (C) Tubules show widespread attenuation of epithelial cells with drop-out nuclei and sloughing of epithelial cells inside the lumen of tubules (arrows) (hematoxylin-eosin; original magnification, ×100). (D) Electron microscopy reveals diffuse effacement of foot processes (arrow) and hypertrophy of podocytes with tubulovillous transformation (Transmission electron microscopy [TEM]; original magnification, ×2,000). (E) In situ hybridization for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA is negative in COVID-19–associated collapsing glomerulopathy (original magnification, ×200). (F) In contrast, in situ hybridization is positive for SARS-CoV2 RNA in lung epithelia of another patient with COVID-19 infection (original magnification, ×200).

Figure 2

RNA sequencing analysis of the kidney cortex in coronavirus disease 2019 (COVID-19)–associated collapsing glomerulopathy. Differentially expressed genes with 1.5-fold–magnitude changes between expression profiles of 1 patient with COVID-19–associated collapsing glomerulopathy and data from 12 control healthy individuals downloaded from GTEx (Genotype-Tissue Expression) database were used for Gene Ontology (GO) term enrichment (GO) terms and pathway analysis by Fisher exact test with P <0.05. Upregulated genes were enriched for cell cycle, chromosome segregation, response to wounding, blood coagulation, and humoral immune response, whereas downregulated genes were enriched for ion transport, metabolic processes, and oxidation. Pathway analysis from both up- and downregulated genes showed enrichment of transmembrane transport, oxidation, and blood coagulation consistent with the GO terms analysis. Upregulated genes were enriched only for FOXM1 pathway, while genes related to renin-angiotensin system were downregulated.

Figure 3

Phospho-STAT3 (signal transducer and activator of transcription 3) expression in coronavirus disease 2019 (COVID-19)–associated collapsing glomerulopathy (CG) and HIV-associated nephropathy (HIVAN). Immunohistochemistry staining of kidney biopsy specimen reveals phospho-STAT3 expression is significantly increased in podocytes and proximal tubular cells in COVID-19–associated CG and HIVAN as compared with normal kidney tissue (scale bars, 50 μm).