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Genomewide transcriptional analysis of growth hormone-treated human podocytes

ABSTRACT: The growth hormone plays a significant role in normal renal function and overactive growth hormone signaling has been implicated in proteinuria in diabetes. Earlier studies from our group have shown that the glomerular podocytes, which play an essential role in renal filtration, express the growth hormone receptor, suggesting the direct action of growth hormone on these cells. Nevertheless, the precise mechanism and the downstream pathways that are induced by the excess growth hormone in these podocytes leading to diabetic nephropathy are not clearly established. To compressively understand the growth hormone’s effect on podocytes at transcript level we performed RNA-Sequencing. Conditionally immortalized human podocytes were employed in this study.

ORGANISM(S): Homo sapiens

PROVIDER: GSE140308 | GEO | 2020/08/28

REPOSITORIES: GEO

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Project description:Diabetic kidney disease is the major cause of end-stage kidney failure worldwide. Podocyte damage is one of the hallmarks of diabetic nephropathy, where the loss of the podocyte filtration barrier leads to proteinuria and progressive renal damage. Bradykinin (BK) is a vasoactive peptide that was shown to play an important role in the progression of renal damage. In this study, we aim to evaluate the changes in protein expression profiles of rat podocytes upon the treatment with BK by an advanced proteomics platform in conjunction with bioinformatics and pathway enrichment analysis. This analysis will help in discovering core effectors whose upstream and downstream protein profile can elucidate signaling mechanisms underlying BK’s modulation of the podocyte biology. Cultured immortalized rat podocytes were treated with BK at 10-7 M for 3 and 6 hours. Proteome profile was evaluated by LC-MS/MS analysis, and pathway enrichment analysis was performed on the resulting differential proteomic data. Proteomic analysis of podocytes treated by BK revealed 61 proteins that were differentially altered (up or downregulated) in response to BK treatment compared to unstimulated control podocytes. Pathway enrichment analysis suggested an inhibition of the cell death pathway and the involvement of elements of the cytoskeletal activity as well as activation of the inflammatory pathways. Of interest, one of the inflammatory proteins that were identified to be induced by BK treatment is Prostaglandin H Synthase-2 (PTGS-2, also known as COX-2). The upregulation of COX-2 by BK treatment was validated by western blot analysis. In addition, treatment of podocytes with BK significantly induced the production and release of PGE2 and this effect was inhibited by both COX-2 and MAPK inhibitors, demonstrating that the production of PGE2 by BK is mediated via a COX-2 and MAPK-dependent mechanisms. The findings of the present study provide a global understanding of the effector modulated proteome in response to BK treatment, and also reveal BK as an important modulator in the arachidonic acid metabolism pathway and a potential player in the progression of diabetic nephropathy.

Project description:Podocyte effacement and loss characterizes glomerulopathies such as diabetic nephropathy, lupus, and glomerular toxicity. Human primary podocyte-like epithelial cells cultured from urine (ECU) were characterized as a window to understand podocyte regeneration in these glomerulopathies. Cytokines TNF, and VEGF stimulated regrowth, whereas FGF-1 and IL1 inhibited growth, consistent with other podocyte or parietal epithelial cell models. Review of published micrographs indicated that podocyte foot processes in rodent kidneys interdigitated exclusively with foot processes from other cells, suggesting podocytes practice self-avoidance. In culture, ECU avoided close interactions with other cells arising from the same clone, until enough cells grew for the culture to become confluent. In contrast, ECU derived from multiple clones associated actively to form contiguous monolayers. Gene expression profiling of eight clonal ECU colonies using RNA sequencing revealed that each colony expressed a highly variable profile of the 53 Protocadherin genes. Variable combinations of the 53 Protocadherin PCDHA-, PCDHB-, and PCDHG- gene products are known to act homophilically to direct self-avoidance interactions in human neurons, so PCDH- genes are postulated to govern self-avoidance similarly in podocytes. Such protocadherin profiles could be considered cell names. Transcriptional profiles of ECUs suggest they may represent intermediate stages of Parietal Epithelial Cells (PECs) differentiating into podocytes. They further suggest that each podocyte practices self-avoidance, interdigitating selectively with other cells in the glomerulus. To enable further investigation of multi-clonal podocyte interactions, five podocyte clones were immortalized using temperature-sensitive SV40 Large T antigen. These results suggest that non-self interdigitation of new podocytes with remnant podocytes may facilitate replacement of dying podocytes and re-establishment of a functional filtration barrier.

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Genomewide transcriptional analysis of growth hormone-treated human podocytes

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