Effect of mast cell chymase of rat skin on intercellular matrix: a histochemical study

The effects of purified mast cell chymase of rat skin on intercellular matrix were studied histochemically using cartilage as a model. The enzyme effectively releases proteoglycans from neonatal human costal cartilage. An analysis of the primary site of proteolytic attack by chymase in the matrix was attempted. The results suggest that components containing the more acidic radicals (e.g. sulphates) are hydrolyzed first. After a prolonged attack, the matrix loses most of its staining with Toluidine Blue and Alcian Blue, and staining of collagen is increased. The hydrolyzed regions of cartilage in Alcian Blue-stained sections exhibited a purple interference colour in polarized light. A similar interference colour appeared after incubating sections of rat skin with chymase. The mast cell chymase presumably promotes diffusion of plasma to the site of injury by the direct breakdown of connective tissue ground substance.