Upregulation of collagen VIII following porcine coronary artery angioplasty is related to smooth muscle cell migration not angiogenesis

Type VIII collagen is upregulated after vessel injury, and this collagen ha s been implicated in both smooth muscle cell migration and angiogenesis. Th is study examines the temporal and spatial pattern of expression of type VI II collagen in porcine coronary vessels at specific time points after ballo on angioplasty. In situ hybridization studies demonstrated that collagen VIII messenger rib onucleic acid (mRNA) was markedly elevated in the neoadventitia at 3 days p ost-angioplasty. By 14 days, elevated collagen VIII message was seen mainly in the neointima and this expression decreased to background levels by 90 days. The distribution of collagen VIII protein, detected using immunohisto chemistry, was similar but the up-regulation lagged behind the mRNA increas e by a few days. Pre-treatment of sections with pepsin highlighted variatio ns in the organization and appearance of extracellular collagen VIII contai ning structures in both injured and normal vessels. New vessel formation wa s evident in the neoadventitia after 3 days, but there was no colocalizatio n of type VIII collagen immunostaining with that of von Willebrand factor ( a marker of endothelial cells) in the neoadventitia. These data show that u p-regulation of collagen VIII in the neoadventitia is an important early ma rker of the coronary arterial response to injury, and is not associated wit h new vessel formation.