Assessment of gelatinase expression and activity in articular cartilage.

Two methods for the assessment of the expression of gelatinases A and B, MMP-2 and MMP-9, in articular cartilage are described. Immunohistochemical analysis of tissue sections provides information about the precise localization of the enzymes within the tissue, pinpointing the cells that synthesize the proteinases, and zymography of cell/ tissue conditioned culture media allows a semi-quantitative assessment of the gelatinases and their activation status.

Matrix metalloproteinases are not essential for aggrecan turnover during normal skeletal growth and development.

The growth plate is a transitional region of cartilage and highly diversified chondrocytes that controls long bone formation. The composition of growth plate cartilage changes markedly from the epiphysis to the metaphysis, notably with the loss of type II collagen, concomitant with an increase in MMP-13; type X collagen; and the C-propeptide of type II collagen. In contrast, the fate of aggrecan in the growth plate is not clear: there is biosynthesis and loss of aggrecan from hypertrophic cartilage, but the mechanism of loss is unknown.