Experimental osteoarthritic articular cartilage is enriched in guanidine soluble type VI collagen

Experimental osteoarthritis was surgically induced in the right knee joint of dogs; the left knee served as a control. Articular cartilage was extracted with 4 M guanidinium chloride, 0.05 M sodium acetate, pH 6.0, containing proteinase inhibitors and the proteins purified by associative CsCl density gradient centrifugation. Equal quantities of protein were electrophoresed in agarose-acrylamide gradient gels and the high molecular weight type VI collagen bands detected in immunoblots with a polyclonal antiserum. Type VI collagen bands between 185 and 220 kDa were evident in the pathological specimens of dogs sacrificed 3, 5, and 7 months after surgery and were either absent or only very weakly visible in the controls. These results demonstrate that experimental osteoarthritic cartilage is enriched in 4 M guanidine-soluble type VI collagen.