title: Fibronectin and water content of articular cartilage explants after partial depletion of proteoglycans.
abstract: The aim of this study was to test the hypothesis that fibronectin in cartilage of osteoarthritic joints accumulates in increased quantities in response to a reduction in proteoglycan content in the matrix. We determined fibronectin content in an ELISA system, uptake of plasma 125I-fibronectin from the medium, and glycosaminoglycan content by a dye method. The proteoglycan content of canine articular cartilage was reduced by co-incubation of the cartilage with canine synovium, partially purified catabolin, or retinoic acid. Data suggested that proteoglycan loss alone was not sufficient to result in the increased fibronectin accumulation that has been reported in the deteriorating articular cartilage of osteoarthritic joints. Cartilage that lost as much as 75% of its proteoglycan content did not have increased fibronectin content and did not take up more fibronectin from the external medium. A related goal of this study was to evaluate the percentage of water in proteoglycan-depleted but disease-free cartilage, as the percentage of water is known to be elevated in osteoarthritic cartilage. Data indicated that the percentage of water in the depleted cartilage increased in proportion to the decrease in proteoglycan content, but the total amount of water in the cartilage did not increase; water content appeared to be unchanged. Under the conditions used, the proteoglycan content was reduced and the percentage of water was elevated, but fibronectin content was not increased. Thus, the cartilage incubated in vitro did not mimic osteoarthritic cartilage.
mesh_terms: D000818:Animals; D001834:Body Water / Q000032:analysis / Q000378:metabolism*; D002358:Cartilage, Articular / Q000032:analysis / Q000378:metabolism* / Q000473:pathology; D003470:Culture Media; D046508:Culture Techniques; D004285:Dogs; D000431:Ethanol; D005109:Extracellular Matrix / Q000378:metabolism; D005353:Fibronectins / Q000032:analysis / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000032:analysis / Q000378:metabolism; D007457:Iodine Radioisotopes; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D011509:Proteoglycans / Q000378:metabolism*; D013583:Synovial Membrane / Q000473:pathology; D014212:Tretinoin
chemical_list: D003470:Culture Media; D005353:Fibronectins; D006025:Glycosaminoglycans; D007457:Iodine Radioisotopes; D011509:Proteoglycans; D000431:Ethanol; D014212:Tretinoin