Figure 5.

Stimulation of a BMP-2/MSX2-directed osteoblastic differentiation program by NaH₂PO₄/NaHPO₄ through induction of osterix. Basal levels of gene expression in hVSMC cultured in DMEM as described in the Concise Methods section and detected by RT-PCR (insets) were set as a reference value of 1 (□, group A). Fold induction by high phosphorus [2 mM NaH₂PO₄/(Na)₂HPO₄] culture media (▪, group B) and 2 mM phosphorus plus 10 ng/ml BMP-7 (□, group C) was determined. An osteoblastic transcriptional program directed by BMP-2/MSX2 was present in hVSMC cultures as demonstrated by the presence of osteocalcin (A), BMP-2 (B), MSX2 (C), and RUNX2 (D) gene transcription. (E) Osterix was only weakly expressed in basal culture conditions. Phosphorus stimulated transcription of osterix. BMP-7 inhibited osterix and osteocalcin expression. Data were normalized to the expression level in basal culture conditions and expressed as fold induction (mean ± SEM; n = 3).