Collagenase-solubilized lipoprotein--glycosaminoglycan complexes of human aortic fibrous plaque lesions.

The interaction of lipoproteins and arterial connective tissue macromolecules was studied using human atherosclerotic plaque tissues. After extraction with 0.15 M NaCl, the tissues were repeatedly digested with collagenase followed by elastase. The collagenase-solubilized lipoprotein--GAG complexes were isolated by gel-filtration and ultracentrifugation and analyzed for lipids, GAG and protein. While extraction by 0.15 M NaCl released only about 13% of the total cholesterol from the tissues, subsequent digestions by collagenase and elastase yielded 60% and 17% cholesterol, respectively. Both 0.15 M NaCl and collagenase treatment released equal amounts of GAG and accounted for 84% of the total GAG. Immunologically, lipoproteins resembled serum apoB-containing lipoproteins. Bio-Gel A-50m column chromatography of collagenase-extracted materials gave a single peak which contained lipoproteins of 1.006 and 1.063 floating densities, GAG and hydroxyproline. Hyaluronic acid (HA) and chondroitin 6-sulfate were identified; HA was the major GAG. Although the precise nature of the interaction of arterial connective tissue components with lipoproteins is not completely understood, isolation of such complexes indicates the importance of these macromolecules in sequestration of lipoproteins.