CCAAT/Enhancer-Binding Protein β (C/EBPβ) Regulates Calcium Deposition in Smooth Muscle Cells

Calcium deposition in vascular smooth muscle cells (VSMCs), a form of ectopic ossification in blood vessels, can result in rigidity of the vasculature and an increase in cardiac events. Here, we report that CCAAT/enhancer-binding protein beta (C/EBPβ) potentiates calcium deposition in VSMCs and mouse aorta induced by inorganic phosphate (Pi) or vitamin D₃. Based on cDNA microarray and RNA sequencing data of Pi-treated rat VSMCs, C/EBPβ was found to be upregulated and thus selected for further evaluation. Quantitative RT-PCR and Western blot analysis confirmed that C/EBPβ was upregulated in Pi-treated A10 cells, a rat VSMC line, as well as vitamin D₃-treated mouse aorta. The overexpression of C/EBPβ in A10 cells increased bone runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and osteopontin (OPN) mRNA in the presence of Pi, as well as potentiating the Pi-induced increase in calcium contents. The Runx2 expression was increased by C/EBPβ through Runx2 P2 promotor. Our results suggest that a Pi-induced increase in C/EBPβ is a critical step in vascular calcification.