Collagen biosynthesis by neointimal smooth muscle cells cultured from rabbit aortic explants 15 weeks after de-endothelialization.

Extracellular matrix (ECM) accumulation in arterial neointima, developed in response to de-endothelialization, is a prolonged process. In this study, we examined the relationship between increased collagen accumulation and synthetic activity of neointimal smooth muscle cells (SMCs) derived from aortic explants fifteen weeks after balloon catheter injury. Freshly confluent SMCs, derived either from normal aorta or from aortic neointima, were used in this study. The newly synthesized collagen was analysed by measuring [3H]-proline incorporation; and the mRNA expression for two major types of collagen, collagen type I and type III, was studied by Northern blot analysis. Our results indicated a three fold increase in protein (collagen) synthesis by neointimal SMCs. At the same time, the steady-state mRNA for procollagen I and procollagen III was elevated five and three times, respectively. These data indicate that persistent synthesis contributes to collagen accumulation in the arterial neointima and both transcriptional and post-transcriptional regulation take part in this process.