Vascular injury compared to ageing of normal rabbit aorta. Biochemical and histochemical studies on time-dependent alterations of vascular connective tissue.

Male albino rabbits of the Danish country strain, 5 months of age, were divided into two groups. One group of animals was killed 180 days after a single mechanical dilatation injury of the thoracic aorta. A second group of untreated controls was killed at ages of 150, 165, 180, 210, 330, and 450 days. Glycosaminoglycans, uptake of 35S-sulphate, collagen, uptake of 125I-albumin, and vascular histochemistry and morphology were analyzed in the thoracic aorta. In the injured aortae the dry weight and the total amounts of hexosamine, hyaluronic acid, chondroitin-4,6-sulphate, dermatan sulphate, heparan sulphate, and hydroxyproline were increased. The concentration of hyaluronic acid decreased, whereas the concentration of dermatan sulphate increased. The concentrations of chondroitin-4,6-sulphate and heparan sulphate were unchanged. The total uptake of 35S-sulphate into the sulphated proteoglycans as well as the uptake of 125I-albumin were increased. The light microscopical examination showed thickening of the intima, medial changes with fibrosis, accumulations of proteoglycans, calcifications, formation of cartilage, and ossified tissue with haematopoiesis. In the uninjured thoracic aorta the only significant change during ageing was an increase in the total amount of hyaluronic acid and a decrease of the 35S-sulphate incorporation into the chondroitin-4,6-sulphate in the aorta. No morphological or histochemical alterations were observed during ageing. Spontaneous lesions were observed in 2 out of 55 aortas. It may be concluded that injury and ageing are reflected quite differently in the thoracic aorta of the rabbits. The observations may be of relevance to the interpretation of the alterations in human arterial diseases involving processes of injury and repair as well as ageing.