COLLAGEN BIOSYNTHESIS BY NEOINTIMAL SMOOTH-MUSCLE CELLS CULTURED FROMRABBIT AORTIC EXPLANTS 15 WEEKS AFTER DEENDOTHELIALIZATION

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