Biochemical and Morphological Studies of Steady State and Lipopolysaccaride Treated Bovine Articular Cartilage Explant Cultures

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Abstract
Explants of bovine articular cartilage were cultured for up to 50 days in 20% fetal calf serum in the presence or absence of the endotoxin lipopolysaccharide (LPS); or in various protocols involving different treatment times with LPS followed by recovery times in the absence of LPS. Cultures were measured in terms of rates of proteoglycan synthesis (incorporation of [35S]sulfate), proteoglycan contents and collagen contents. Histological sections were prepared for both light and electron microscopy. In fetal calf serum, the rates of synthesis and contents of proteoglycans per collagen remained constant, while for LPS treated cultures both parameters decreased. For recovery groups, the rates of proteoglycan synthesis increased during the time of recovery if the LPS treatment times were relatively short (2 weeks or less) and if the tissue was obtained from younger animals; net increase in proteoglycan contents occurred infrequently if at all during recovery protocols. Histological examinations revealed that chondrocytes in cultures maintained in fetal calf serum appeared normal with large stores of glycogen. In LPS treated cultures, chondrocytes were depleted of glycogen stores and contained numerous lipid droplets. In recovery cultures, chondrocytes replenished their glycogen contents, but the lipid droplets remained. For both LPS treated and recovery groups the extracellular matrix was depleted of proteoglycans with time in culture. The results provide further evidence for the ability of this explant culture system to maintain steady state metabolic parameters for proteoglycan metabolism over long time periods and for its utility to study reagents which regulate or perturb these parameters.