Objective--Overexpression of decorin reduces neointimal thickening in balloon-injured carotid arteries of rats by decreasing the volume of neointimal extracellular matrix (ECM). We examined the hypothesis that decorin regulates ECM volume by stimulating cell-mediated contraction of collagen-rich ECMs.

Methods and Results--Rat arterial smooth muscle cells (ASMCs) transduced with bovine decorin cDNA by retroviral transfection (LDSN) exhibited enhanced contraction of collagen gels in vitro when compared with vector-only transduced (LXSN) cells. Addition of recombinant decorin to LXSN or LDSN cells did not stimulate contraction of collagen gels. Enhanced contraction of collagen by LDSN cells was unaffected by the metalloproteinase inhibitor GM6001. LDSN cells exhibited increased expression of type I collagen mRNA when compared with that of LXSN cells. Correspondingly, collagen gel contraction by LDSN cells was reduced by inhibition of collagen synthesis by 3,4-L-dehydroproline (L-DHP). Antibodies to 11-integrin, but not to 21-integrin, blocked collagen contraction by both LXSN and LDSN cells. However, LXSN and LDSN cells expressed similar levels of 1- and 1-integrin mRNAs.

Conclusions--Decorin synthesized de novo by ASMCs increases type I collagen synthesis and enhances contraction of collagen gels. Regulated synthesis of decorin may be a useful therapeutic approach to reduce ECM volume in vascular disease.