Interstitial HIF1A induces an estimated glomerular filtration rate decline through potentiating renal fibrosis in diabetic nephropathy

Aims: This study aimed to identify interstitial molecules that were responsible for the deterioration of the esiantimated glomerular filtration rate (eGFR) in diabetic nephropathy (DN). Materials and methods: Weighted gene co-expression network analysis (WGCNA) was used to link the tubulointerstitial gene expression profile of DN to eGFR values. The relationship of eGFR with each sub-domain regulator in the network was analyzed with the linear regression model. Gene sets enrichment analysis (GSEA) was applied to detect the molecular changes mostly relating to the essential regulators. Key findings: Four co-expression modules were found strongly correlating with eGFR values. Genes from these modules were over-represented in fibrosis-related biological processes (extracellular matrix (ECM) organization and cell adhesion) and pathways (integrin signaling and ECM-receptor interaction). Of sub-domains in the gene interaction network, the expression of hypoxia-inducible factor 1A (HIF1A) was most negatively correlated with eGFR (R-2 = 0.417, P = 0.026). The positive correlations between HIF1A and its target genes were found, indicating an enhanced transcriptional activity of HIF1A. We also found that HIF1A positively correlated with CCAAT enhancer binding protein delta (CEBPD) (r = 0.731, P = 0.011), an activator of HIF1A transcription. Moreover, GSEA showed that samples with high HIF1A expression were enriched with fibrosis associated signaling, like ECM-receptor interaction and cell adhesion. Intriguingly, vascular epithelial growth factor A (VEGFA) expression decreased while HIF1A increased (R-2 = 0.733, P = 0.001), suggesting VEGFA loss may exacerbate hypoxia and stimulate HIF1A induction. Significance: The present study suggested that interstitial HIF1A may be involved in renal interstitial fibrosis in DN.