Extraction and characterization of the tissue forms of collagen types II and IX from bovine vitreous

We report for the first time that, after centrifugation of adult bovine vitreous, the hyaluronan-rich supernatant contains collagens which can be isolated in their intact forms by precipitation with 4.5 M NaCl. This precipitate constituted approx. 4% of the total vitreous collagen and comprised collagen types IX and II (in the approximate ratio of 4:1) with negligible amounts of type-V/XI collagen. Type-II collagen was present partly in a pro-alpha 1(II) form, suggesting that there is active synthesis of type-II collagen into the matrix of adult bovine vitreous. Type-IX collagen was purified (2-2.5 mg/l of vitreous) and its glycosaminoglycan chain composition was analysed. Bovine vitreous type-IX collagen always possessed a glycosaminoglycan chain of comparatively low M(r) that was predominantly 4-sulphated, with chondroitin 6-sulphate representing a more minor component. By contrast, chick vitreous has been shown to contain type-IX collagen which always possesses a high-M(r) chondroitin sulphate chain that is predominantly 6-sulphated. The functional significance of these different glycosaminoglycan chain lengths and sulphation patterns is discussed.