Alterations in collagen subtype III and IV protein in experimental venous bypass grafting

To examine changes in collagen III and IV protein during the development of intimal hyperplasia in experimental vein grafts.

Sixteen New Zealand White rabbits underwent reversed, jugular vein, interposition grafting of the carotid artery. Vessels were harvested 3, 7 or 28 days after operation and subjected to immunohistochemical examination and gelatinase assays.

In control vein, collagen IV was expressed around adventitial blood vessels and throughout the endothelium. Compared with its presence in control veins, collagen IV protein was decreased in the endothelium in all 3-day vein grafts and undetectable in the endothelium and intima in 7-day vein grafts, but was present in the endothelium and intimal hyperplasia in 28-day vein grafts. In contrast, collagen III was absent from the endothelium of control vein and 3-day vein grafts, was present at low levels in the intima of 7-day vein grafts, but was absent from the endothelium and intimal hyperplasia in 28-day vein grafts. In 3-day vein grafts, areas of collagen IV loss colocalized to areas of leukocyte infiltration. Protein extracts from 3-day vein grafts contained a 72 kDa gelatinase.

The presence and alterations of collagen protein in veins and vein grafts are subtype specific. Collagen III does not appear to be a normal component of intimal hyperplasia in vein grafts. The decrease in collagen IV protein in the endothelium of veins may be a component of the endothelial changes that follow bypass grafting, mediated by leukocytes, the induction of gelatinase activity, or both.