#1211 IGFBP-5/TGF-β1-mediated cell crosstalk between endothelia and tubular epithelia promotes renal fibrosis

Background and Aims Renal fibrosis is a common pathophysiological characteristic of chronic kidney disease (CKD) for which there is no effective treatment. The mechanism of renal fibrosis is complicated and remains unclear. Our previous study revealed that Insulin-like growth factor binding protein 5 (IGFBP-5) induces glycolytic activation in ECs and ultimately aggravates renal inflammation in diabetic kidney disease (DKD). This study aims to discover the relationship between IGFBP-5 and renal fibrosis. Method HK-2 and HUVEC cells were included in this study. UUO and ANN model were obstructed by Wild-type, IGFBP-5−/− and IGFBP-5flox/flox, cre mice. IGFBP-5, TGF-β and fibrosis makers were detected to explore the mechanism of IGFBP-5 in fibrosis. Results We found that the serum IGFBP-5 levels were significantly increased in CKD, that IGFBP-5 was dominantly localized in vascular endothelial cells (ECs) of kidney tissue, and that IGFBP-5 deficiency relieved renal fibrosis in CKD model mice. In vitro experiments indicated that IGFBP-5 exacerbated the fibrosis phenotypic alteration of tubular epithelial cells (TECs) by the TGF-β1/p-Smad3 signaling pathway. In turn, TGF-β1 could facilitate the synthesis of IGFBP-5 in ECs. The crosstalk between TECs and ECs mediated by IGFBP-5 and TGF-β1 was confirmed in a coculture system and endothelial-specific IGFBP-5-deficient mice. Conclusion Renal fibrosis is exacerbated by TEC-EC cellular crosstalk through the feedback loop consisting of IGFBP-5 and TGF-β1. These findings suggest that IGFBP-5 may be a new pathogenic factor in renal fibrosis and a potential new therapeutic target in CKD.