A Bigenic mouse model of FSGS reveals perturbed pathways in podocytes, mesangial cells and endothelial cells

Abstract

Short Title: Perturbed molecular pathways in bigenic mouse model of focal segmental glomerulosclerosis AbstractFocal segmental glomerulosclerosis is a major cause of end stage renal disease. Many patients prove unresponsive to available therapies. An improved understanding of the molecular basis of the disease process could provide insights leading to novel therapeutic approaches. In this study we carried out an RNA-seq analysis of the altered gene expression patterns of podocytes, mesangial cells and glomerular endothelial cells of the bigenic Cd2ap+/-, Fyn-/-mutant mouse model of FSGS. In the podocytes we observed upregulation of many genes related to the Tgf family/pathway, including Gdnf, Tgf1, Tgf2, Snai2, Vegfb, Bmp4, and Tnc. The mutant podocytes also showed upregulation of Acta2, a marker of smooth muscle and associated with myofibroblasts, which are implicated in driving fibrosis.GO analysis of the podocyte upregulated genes identified elevated protein kinase activity, increased expression of growth factors, and negative regulation of cell adhesion, perhaps related to the observed podocyte loss. Both podocytes and mesangial cells showed strong upregulation of aldehyde dehydrogenase genes involved in the synthesis of retinoic acid.Similarly, the Cd2ap+/-, Fyn-/-mesangial cells, as well as podocytes in other genetic models, and the glomeruli of human FSGS patients, all show upregulation of the serine protease Prss23, with the common thread suggesting important functionality. Another gene with strong upregulation in the Cd2ap+/-, Fyn-/-mutant mesangial cells as well as multiple other mutant mouse models of FSGS was thrombospondin, which activates the secreted inactive form of Tgf. The Cd2ap+/-, Fyn-/-mutant endothelial cells showed elevated expression of genes involved in cell proliferation, angioblast migration, angiogenesis, and neovasculature, all consistent with the formation of new blood vessels in the diseased glomerulus. The resulting global definition of the perturbed molecular pathways in the three major cell types of the mutant glomerulus provide deeper understanding of the molecular pathogenic pathways.

Global transcriptomic changes occur in aged mouse podocytes

“…The same analysis on bulk RNA-seq of fluorescenceactivated cell sorting-purified podocytes, mesangial cells, and podocytes from healthy mouse glomeruli 45 showed a similar podocyte autocrine signaling network, with age-associated declines in the VEGFA, WNT, and BMP pathways and laminin-integrin interactions (Supplementary Figure S7).…”

An Integrative in silico Study to Discover Key Drivers in Pathogenicity of Focal and Segmental Glomerulosclerosis

“…Based on a study conducted on the ECM proteome changes in a murine FSGS model, some of the BMP signaling inhibitors like sclerostin were among the downregulated genes in the models [41]. Elevated levels of the Bmp-2 gene were also shown in previous experiments analyzing the gene expression profiles of podocytes, mesangial cells, and endothelial cells of the Cd2ap and bigenic Cd2ap +/−, Fyn −/− mutant mouse models of FSGS [42, 43].…”

Deconvolution of Focal Segmental Glomerulosclerosis Pathophysiology Using Transcriptomics Techniques

“…Vice versa, gene expression from in vivo and in vitro studies can be correlated with published transcriptomics datasets in humans (Fig. 2) [16,18,20,31,[48][49][50]. For example, the gene expression signature of a transgenic rat model of FSGS based on podocyte-specific genetic mTORC1 inhibition correlated with gene expression of human FSGS patients [50].…”

“…Published transcriptomics datasets of kidney dis-Glomerular Dis 2021;1:265-276 DOI: 10.1159/000518404 ease, including FSGS are also easily accessible online, at different repositories or through the search engine and data mining tool "Nephroseq" (available at www.nephroseq.org, formerly known as "Nephromine" [47]). These datasets can be used to validate a candidate transcriptional biomarker or signature that was identified in in vivo or in vitro experiments [16,18,20,31,[48][49][50] or in an independent human FSGS cohort. Vice versa, these datasets can first be "mined" for potential disease targets or biomarkers, which could subsequently be studied in in vivo or in vitro models (typically FSGS mouse or rat models or cultured podocytes) or validated with transcriptomics or proteomics (e.g., immunohistochemistry) in independent cohorts to elucidate their role in disease pathophysiology [25].…”