[Type II collagen fragment capacity to induce collagen cleavage and hypertrophy of articular chondrocyte].

The objective of this study was to determine whether a peptide of type II collagen which can induce collagenase activity can also induce chondrocyte differentiation (hypertrophy) in articular cartilage. At high but naturally occurring concentrations (10 microM and up) the collagen peptide CB12-II induced an increase in the expressions of MMP-13 (24h) and cleavage of type II collagen by collagenase in the mid zone (day 4) and also in the superficial zone (day 6). Furthermore the peptide induced an increase in proliferation on day 1 in the mid and deep zones extending to the superficial zone by day 4. There was also upregulation of COL10A1 expression at day 4 and of type X staining in the mid zone extending to the superficial zone by day 6. Apoptopic cell death was increased by day 4 in the lower deep zone and also in the superficial zone at day 7. The increase in apoptosis in the deep zone was also seen in controls. Our results show that the induction of collagenase activity by cryptic peptide sequence of type II collagen is accompanied by chondrocyte hypertrophy and associated cellular and matrix changes. This induction occurs in the mid and superficial zones of previously healthy articular cartilage. This response of the chondrocyte to a cryptic sequence of denaturated type II collagen may play a role in naturally occurring hypertrophy in endochondral ossification and in the development of cartilage pathology in osteoarthritis.