The applicant seeks to investigate molecular changes that occur in the extracellular matrix of cartilage in aging and in osteoarthritis (OA) that are associated with the degeneration of cartilage. Specifically, we seek to identify molecular damage to athe triple helix of type Ii collagen (ordinarily caused by collagenases) that is thought to occur in ageing and occurs in IA. Since type II collagen containing fibrils provide the tensile properties of cartilage and its molecular integrity, an understanding of how these events occur could lead to new therapeutic means of presenting these changes that lead to loss of joint function. We will examine aging human knee articular cartilages from autopsy and OA cartilages at arthroplasty, and those from the talus (ankle) (autopsy only). Cartilage degeneration is commonly observed in the knee and rarely in the ankle. New immunochemical methods, assays and immunolocalization methods developed in the applicant's laboratory will be used to detect and measure type II collagen a chain denaturation and cleavage at specific sites of the triple helix of human type II collagen in situ. This cleavage will be released to cleavage of isolated human type II collagen produced by the three collagenases, MMP-1, 8 and 13. Also, in situ type II collagen damage will be related to local mRNA expression and protein contents of these three human collagenases that may be present and cause this damage to type II collagen. The relationship of these proteinases to chondrocyte hypertrophy (marked by production of type X collagen) will be examined by in situ hybridization and immunochemical methods. Comparisons will be made of early focal aging lesions with adjacent cartilages and of defined sites in aging and OA cartilages. These studies will provide evidence for whether aging and OA are two distinct degenerative process or whether they are part of a continuing degenerative process, whereby OA represents a clinical progression of an aging process.
