LTBP2 transcriptionally activated by HIF-1α contributes to vascular calcification

Vascular calcification is a major cardiovascular risk factor in chronic kidney disease (CKD), driven by vascular smooth muscle cell (VSMC) osteogenic differentiation. Latent transforming growth factor-beta binding protein 2 (LTBP2) has been implicated in fibrotic processes, but its role in VC remains unclear. This study aims to investigate the role of LTBP2 in vascular calcification and to elucidate the underlying molecular mechanisms.

In vitro vascular calcification was induced in VSMCs cultured in calcification medium. An in vivo model of CKD-associated vascular calcification was established in mice via 5/6 nephrectomy combined with a high-phosphate diet. Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were performed to confirm direct binding of HIF-1α to LTBP2 promoter. Calcification was assessed by Alizarin red staining and quantitative calcium content analysis. Protein and mRNA levels of LTBP2, HIF-1α, BMP-2, RUNX2, and fetuin-A were measured by Western blot, immunofluorescence staining, and RT-qPCR.

LTBP2 expression was significantly increased during vascular calcification in both cellular and animal models. Knockdown of LTBP2 attenuated osteogenic differentiation and calcification of VSMCs, whereas LTBP2 overexpression exacerbated these effects. Moreover, LTBP2 depletion effectively mitigated vascular calcification in CKD mice. Mechanistically, HIF-1α was found to directly bind to LTBP2 promoter and transcriptionally upregulate its expression. Furthermore, HIF-1α/LTBP2 axis mediated osteogenic differentiation and calcification of VSMCs.

LTBP2, transcriptionally activated by HIF-1α, promotes VSMC osteogenic differentiation and accelerates vascular calcification progression, suggesting LTBP2 may serve as a potential therapeutic target for vascular calcification treatment in CKD.