Expression and regulation of bone morphogenetic protein antagonists in vascular smooth muscle cells

Background

Vascular smooth muscle cell (VSMC) proliferation is crucial to the development of vascular diseases such as atherosclerosis and post-PTCA restenosis. Angiotensin II and platelet-derived growth factor play an important role in this phenomenon through direct action on VSMC or by modulating other growth factors. Bone morphogenetic proteins (BMPs) are members of the transforming growth factor beta superfamily and participate in signaling pathways linked to VSMC proliferation, hypertrophy and extracellular matrix production. BMPs exhibit an antiproliferative effect on VSMC and are inhibited by a family of antagonists (BMP-antag) that includes the proteins Gremlin, Dan and Cerberus. BMP-antag would thus facilitate cell proliferation by blocking an antimitotic pathway.

Aim

The purpose of the present study is to characterize the expression patterns of BMP-antag in VSMC, and their regulation by well-known growth factors.

Methods

Rat primary VSMC were cultured, RNA isolated and cDNA prepared by means of commercially available kits. BMP-antag mRNA levels were determined through quantitative realtime polymerase chain reaction. Angiotensin II (300 nM) or platelet-derived growth factor (2 ng/ml) were added, and their effects evaluated following 3, 6 and 12 hours as described elsewhere.

Results

We detected for the first time the constitutive expression of three members (Gremlin, Dan and Cerberus) of the BMP-antag family in cultured rat VSMC. In addition, our preliminary data demonstrate that Gremlin expression was significantly upregulated by angiotensin II (3 hours, 3.1 ×; 6 hours, 1.4 ×; 12 hours, 2.4 ×; n = 4) and platelet-derived growth factor (3 hours, 2.2 ×; n = 4).

Conclusions

Taken together, our results suggest that the BMP-antag family of genes may have a relevant role in the development of phenotypic alterations involved in the pathophysiology of vascular diseases. Additional studies are underway to better define the regulation of these genes in vitro as well as their expression profile in vivo.