Connective tissue changes in syngeneic aortal vein grafts in rats.

The supradiaphragmatic inferior vena cava was syngeneically transplanted into the infrarenal part of the abdominal aorta in rats of inbred strains. The initial histologic changes coincided with the changes usually seen in wound healing during the inflammatory phase and the phase of fibroplasia. Later the reparative process occurred predominantly in the luminal part of the vein wall, and was usually seen as intimal hyperplasia. In some grafts this process caused a narrowing of the lumen. In this particular experimental model the thickening of the intimal layer was mainly due to organization of fibrin layering thrombus. This was shown by detection of lamellar fibrin deposits and a high concentration of fibronectin in this layer. A large amount of fibronectin was detected in and around the proliferating fibroblasts and in thrombi. This explains the high concentration of fibronectin in the proliferating intimal layer of the graft.