Fibroblast growth factor 1 inhibits podocyte senescence in mice with diabetic nephropathy

ObjectiveTo identify differentially expressed genes (DEGs) associated with diabetic nephropathy and explore their effects on glomerular podocyte senescence.MethodsRenal tissue transcriptome datasets (GSE142025 and GSE199838) were downloaded from the Gene Expression Omnibus (GEO) database, including 39 renal biopsy specimens from patients with diabetic nephropathy and 24 control specimens. The DESeq2 package in R was used to analyze the data, with P < 0.05 and |log₂ fold change| ≥ 1 as the criteria for DEG identification. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed on the identified DEGs. DEGs involved in senescence-related pathways were further screened and validated in the glomerular transcriptome dataset GSE96804. The expression of these genes was verified using a mouse model of diabetic nephropathy and high glucose-induced podocytes. Subsequently, the effects of fibroblast growth factor 1 (Fgf1) on high glucose-induced podocyte senescence and diabetic nephropathy were analyzed through Fgf1 overexpression and knockdown in mouse podocytes, as well as recombinant Fgf1 (rFgf1) treatment in vivo. RT-qPCR was used to verify DEG expression changes; Masson and PAS staining to detect renal fibrosis and glomerular pathology; Fgf1 and Nephrin immunofluorescence to detect Fgf1 expression in podocytes; SA-β-gal staining to detect podocyte senescence; p16 and Nephrin immunofluorescence to detect senescence-related protein expression; and Western blotting to detect protein expression levels.ResultsA total of 180 DEGs were identified (89 upregulated, 91 downregulated) in the 39 diabetic nephropathy and 24 control specimens from the GSE142025 and GSE199838 datasets. KEGG analysis showed significant enrichment of these genes in multiple senescence-related signaling pathways, including the MAPK, Rap1, FoxO, and p53 pathways. Validation in the glomerular dataset GSE96804 revealed that FGF1, GADD45B, NR4A1, SRF, and PARD6A were downregulated, and IKBKB was upregulated in the glomeruli of diabetic nephropathy patients, consistent with the previous datasets; the remaining five genes showed no significant changes. In the mouse model, Fgf1 expression was significantly downregulated in renal tissue, while Gadd45b, Nr4a1, Srf, and Ikbkb were upregulated; Pard6a showed no significant difference. In cell models, Fgf1 was downregulated under high glucose, while Ikbkb showed no significant change. Overexpression of Fgf1 in mouse podocytes suppressed the expression of senescence-related genes p21 and p16 and reduced the DNA damage marker γ-H2AX, whereas Fgf1 knockdown had the opposite effect. In vivo, rFgf1 treatment inhibited STZ-induced glomerular extracellular matrix accumulation, reduced glomerular SA-β-gal activity, and lowered the expression of p16, p21, and γ-H2AX in renal tissue and podocytes, thereby ameliorating podocyte senescence and diabetic nephropathy progression.ConclusionFgf1 is downregulated in renal tissue, glomeruli, and high glucose-induced podocytes in diabetic nephropathy, and Fgf1 alleviates the progression of diabetic nephropathy in mice by inhibiting glomerular podocyte senescence.