Calcium phosphate crystals promotes vascular calcification through BMP-2/Smad signaling / 中华肾脏病杂志

ABSTRACT

Objective To investigate the role of BMP-2/Smad signaling pathway in the osteogenic differentiation of human aortic smooth muscle cells (HASMCs) caused by hyperphosphatemia -induced calcium phosphate (CaP) crystals.Methods High-phosphate medium was incubated at 37℃ for 3 days.CaP crystals and supernatant were isolated by ultracentrifugation.Scanning electron microscope and energy dispersive X-ray spectroscopy were performed for analysis of physicochemical characteristics of CaP crystals.HASMCs were cultured in vitro,and divided into high-phosphate,control,crystals and supernatant groups.Calcification was visualized by Alizarin red staining.Calcium loads in cells were quantified by o-cresolphthalein complexone method.Protein expression of bone morphogenetic protein-2 (BMP-2),Runt-related transcription factor 2 (RUNX2),osteopontin (OPN),phospho-Smad1/5/9 (p-Smad1/5/9) were quantified by Western blotting.After knockdowns of BMP-2 and Smad1 with small hairpin RNA (shRNA) interfering respectively in HASMCs,protein expressions were measured by Western blotting.Results High-phosphate medium induced the formation of CaP crystals.Compared with the cells in control group,CaP crystals significantly induced HASMCs calcification,increased calcium loads and up-regulated the levels of BMP-2,RUNX2 and OPN proteins (all P ＜ 0.05).After the addition of CaP crystals into HASMCs,the level of p-Smad 1/5/9 protein peaked at 30 min (P ＜ 0.05).After BMP-2 was knocked down in HASMCs,the expression of p-Smad1 caused by CaP crystals was blocked completely,and the expressions of RUNX2 and OPN caused by CaP crystals were reduced significantly (all P ＜ 0.05).After Smad1 was knocked down in HASMCs,the expressions of RUNX2 and OPN caused by CaP crystals were decreased significantly (all P ＜ 0.05).Conclusions Hyperphosphatemia-induced CaP crystals promoted osteogenic differentiation of HASMCs through the BMP-2/Smad signaling pathway.