Glycosaminoglycan distribution in rabbit aortic wall following balloon catheter deendothelialization. An ultrastructural study

Abstract

The glycosaminoglycan (GAG), content of rabbit aortic wall was assayed morphometrically using ruthenium red-stained sections viewed by transmission electron microscopy. Two types of ruthenium red-positive granules were identified in the intercellular matrix. Large granules (20 to 50 nm. in diameter) with interconnecting fibrils were removed by digestion of the tissue with testicular hyaluronidase or chondroitinase ABC. Smaller granules (20 nm). were localized mainly in endothelial basement membrane and were resistant to digestion by these enzymes. Both types of granules were removed from the tissue by the action of nitrous acid. At intervals of 11 to 17 weeks after a single balloon deendothelialization of the aortas of normolipemic rabbits, there were significantly more granules of both types in areas where endothelium had regenerated over the neointima than in areas not covered by endothelium. Lipid also accumulated preferentially in the endothelium-covered neointima. Compared to normal aortas, there is an increase in the large granule content in the reendothelialized areas and a decrease in both large and small granule content in the nonendothelialized areas. It is suggested that GAG may trap low density lipoproteins. The low GAG content of the nonendothelialized neointima may account for the low lipid content; additionally, the lack of endothelial cover may allow diffusion of GAG out of these areas carrying low density lipoprotein into the blood stream in the form of GAG-low density lipoprotein complexes or low density lipoprotein removal may be facilitated by high density lipoprotein.