Role of TGF-beta1 in bone matrix production in vascular smooth muscle cells induced by a high-phosphate environment.

Aims: We demonstrated a relationship between transforming growth factor-beta(1) (TGF-beta(1)) and production of bone matrix in vascular smooth muscle cells (VSMCs) induced by a high-phosphate environment.
Methods: Rat VSMCs were incubated in a high-phosphate (2.5 or 3.5 mM) or TGF-beta(1) (2 or 5 ng/ml) environment. TGF-beta(1) monoclonal neutralization antibody (50 microg/ml) was added to inhibit the TGF-beta(1) signal in high-phosphate medium. Production of TGF-beta(1) was analyzed by Western blot and real-time PCR. Core binding factor a1 (Cbfa1), osteopontin (OP), collagen type I (Col I) and osteocalcin (OC) was investigated by Western blot and immunofluorescence staining. Mineral deposition was assessed by von Kossa staining and o-cresolphthalein complexone method.
Results: VSMCs transformation induced by high phosphate occurs via an autocrine loop of TGF-beta(1). First, high phosphate stimulated the production of TGF-beta(1) in VSMCs. Second, TGF-beta(1) could induce increased expression of osteoblast-specific transcription factor Cbfa1 and osteogenic molecule in VSMCs. Third, the TGF-beta(1) neutralization antibody largely attenuated the upregulation of Cbfa1 and bone matrix in high-phosphate-stimulated cells. However, neutralization of TGF-beta(1) could not inhibit high-phosphate-induced VSMCs calcification, indicating that TGF-beta(1) was not necessary for the deposition of calcium.
Conclusion: TGF-beta(1) plays a crucial role in bone matrix production but not calcium deposition in VSMCs induced by a high-phosphate environment, and the blockade of TGF-beta(1) signaling may thus be a therapeutic strategy for use with vascular disease in a high-phosphate environment.
(Copyright 2010 S. Karger AG, Basel.)