EXPRESSION OF BIGLYCAN, DECORIN AND FIBROMODULIN IN THE HYPERTROPHIC PHASE OF EXPERIMENTAL OSTEOARTHRITIS

This study sought to assess the relative levels of the mRNAs of the co re proteins of the small proteoglycans (PGs) biglycan, decorin and fib romodulin in the hypertrophic phase of the early osteoarthritis (OA) t hat follows joint injury. Experimental OA was induced in eight dogs by transection of the anterior cruciate ligament. Articular cartilage wa s harvested from each joint, the total RNA was extracted and the conce ntration of DNA in the cartilage was measured. The relative levels of mRNA for biglycan, decorin and fibromodulin were assessed by northern blot analyses. An increase in cartilage mass with no increase in DNA c oncentration confirmed that the joints were in the hypertrophic phase that follows joint injury. The total RNA per microgram of DNA was incr eased 2.5 times. Compared with control cartilage, the mRNA levels in o steoarthritic cartilage, when normalized to the concentration of DNA, were increased 3.9 times for biglycan, 1.2 times for decorin and 2.4 t imes for fibromodulin. Because these small PGs affect collagen fibrill ogenesis in vitro, their discoordinate metabolism may contribute to th e abnormal collagen formation and deposition that occurs in OA and to the ultimate failure of the articular cartilage.