Repair in arterial tissue. Morphological and biochemical changes in rabbit aorta after a single dilatation injury.

Male albino rabbits were subjected to a single mechanical dilatation of the descending thoracic aorta with a balloon catheter. The animals were killed 3, 6, 14, 30, and 60 days later. Between the sixth and the fourteenth days after injury, all the aortas which had been dilated developed severe, gross arteriosclerosis. Microscopic examination showed destruction and degeneration in the form of necrosis and calcification as well as regeneration and repair including new formation of cells, intercellular substance, and fibers. Biochemical and histochemical analyses revealed an early increase in hyaluronic acid and water followed by an increase in chondroitin-4, 6-sulfate and a later increase in heparan sulfate, dermatan sulfate, and collagen. These alterations were related to the focal lesions in the aortic wall. The permeability of the aorta to 12B I-albumin increased to a maximum 3 days after the dilatation, whereupon it decreased rapidly. The alterations were interpreted as nonspecific processes of repair in the vascular connective tissue. The pronounced dependence of the alterations on the time elapsed after injury must be considered in the study of vascular diseases where injury and repair may be involved. KEY WORDS arterial wall arteriosclerosis collagen connective tissue endothelial cells glycosaminoglycans hyaluronic acid chondroitin sulfates wound healing vascular permeability • Repair processes in the vascular wall have been proposed as characteristic features of various types of vascular diseases such as the connective tissue diseases and arteriosclerosis (1, 2). Proper evaluation and interpretation of biochemical and morphological alterations in human blood vessels are difficult because the duration of the alterations as well as the type and duration of processes preceding them are usually unknown. wall is constantly subjected to a mechanical strain caused by the blood flow and blood pressure. In previous studies, we observed that an increased mechanical strain may be one of the factors responsible for the development of aortic arteriosclerosis in rabbits subjected to systemic hypoxia and intravenous injections of catecholamines (3, 4). Although mechanical factors may also be important in the pathogenesis of human arteriosclerosis (5, 6), little is known about the type and the sequence of biochemical and histochemical alterations following mechanical injury of the arterial wall. The aim of the present study was to investigate the descending thoracic aorta of rabbits morphologically and biochemically at different time intervals after a single short-lasting mechanical dilatation. Aortic glycosami-noglycans, collagen, and aortic permeability to serum albumin were analyzed.