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Biochemical studies on repair cartilage resurfacing experimental defects in the rabbit knee.
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1980
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Cartilage repair after penetrating wounds or drilling into subchondral bone can yield fibrous or hyaline tissue, and it is unclear whether the resulting cartilage is true articular cartilage or fibrocartilage. This study induced repair cartilage in rabbits to biochemically compare it with normal articular cartilage and evaluate its potential for authentic cartilage regeneration. Repair cartilage was induced in rabbits and radiochemical analysis revealed type II collagen as the predominant synthesis product after 3–4 weeks. Initially type I collagen dominated, but by 6–8 weeks type II became predominant while type I remained significant, and after six months the tissue had more collagen but less hexosamine, indicating a fibrous texture due to proteoglycan loss rather than collagen type change.
Wounds penetrating articular cartilage to bone heal with cartilage described variably as either fibrous or hyaline. In the present study, such repair cartilage was induced in the rabbit for biochemical comparison with normal articular cartilage. The main collagen in the repair tissue after three weeks was type I. By six to eight weeks, type II had become predominant and continued to be enriched up to one year; but type I still persisted as a significant constituent of the repair tissue even after a year, so the repair cartilage never fully resembled normal articular cartilage. From radiochemical analysis, type II was determined to be the major collagen synthesized by the repair tissue after three to four weeks. After six months, the repair cartilage contained more collagen and less hexosamine than control cartilage, suggesting that the fibrous texture that often developed was due to a loss of proteoglycans rather than to a change in the type of collagen. Clinical Relevance: Procedures capable of inducing the differentiation of authentic articular cartilage to resurface degenerated human joints would be invaluable. Surgical methods, such as drilling through to subchondral bone, are often attempted. It is not known, however, whether the cartilage that forms is true articular cartilage or, for example, fibrocartilage. The present experimental study in rabbits compared the properties of such repair cartilage with those of normal articular cartilage.