Aging of in vivo cartilage cell.

It can be seen from our results that, in aged cartilage: (1) pepsin solubility of collagen increases; (2) the number of aldimine cross-links of insoluble collagen increases; and (3) the type of collagen changes. Quantitative and qualitative changes of glycosaminoglycan cannot be recognized, and cellularity does not change after 20 years of age, or maturation. Only molecular research on cartilage collagen, which accounts for 60 to 70% of the organic matrix in cartilage, can show the changes in metabolic behavior of cartilage cells that are associated with aging.