Regulation of Articular Cartilage Defects with OP-1 Treated Lyphilized Cartilage Allografts

Shin, Young Jin; Kim, Tae June

Abstract

Joint cartilage defects do nor heal and lead to post traumatic arthritis or degenerative joint diseases. The clinical problem is that so far, we have been unable to induce true cartilage healing and regeneration. Experimental attempts at repairing joint cartilage defects with various means have usually led to the formation of cartilage-like fibro-hyaline scars. We have recently shown that treatment of lyophilized allografts with recombinant osteoinductive protein-1 (OP-1 also known as BMP 7) induces the regeneration of articular cartilage over the head of lyophilized hemijoint allografts. A standardized 3 mm circular defect was created on the articular surface of the knee joint of 12 NZW rabbits. The defect was into carried as full thickness down to subchondral bone. In a blinded and randomized fashion, the rabbits were divided into four groups. In group l (n=4), the ulcer was left untreated; in group II (n=3), the ulcer was reconstructed with a 3 mm disk of lyophilized cartilage allograft; in group lll(n=2), the allograft used was pre-treated with low dose (20 pg) OP-1, and in group IV (n=3), the allograft used was pre-treated with high dose(100 pg) OP-1. The range of motion was normal in all groups. The gross appearance of the untreated defect was still depressed and appeared like a big crater. The lyophilized allograft has a level surface which was not smooth In high dose OP-1 group, the defect was healed much better than the lower dose treated OP-1 group. Under the histologic examination, untreated ulcer group never heals to the cartilage of around defect, a fissure always remains. Lyophilized allograft and low dose OP-1 treated lyophilized allograft groups seem to inhibit healing and there is fibrous scar in ulcer. In the high dose OP-1 treated lyophilized allograft group, new cartilage heals very well all around of the defect margin without fissure. The cartilage has a normal sequence of cellular maturation. In conclusion, in this study of full thickness joint cartilage defects, we confirmed finding in the literature that untreated defect heals with cartilage like tissue which does not fuse with the surrounding cartilage. We found that lyophilized allograft prevents healing of defect, while lyophilized allograft treated with high dose (100 pg) OP-1 seems to induce regeneration of articular cartilage that heals very well to the surrounding defect without any crack or fissure.