Age-related differences in prostaglandin E2 synthesis by equine cartilage explants and synoviocytes

Time- and concentration-related actions of lipopolysaccharide (LPS) on the synthesis of prostaglandin E-2 (PGE(2)) were investigated in cartilage explants and synoviocytes harvested from 3 age groups of horses, all with clinically normal joint function: group A < 10 years; group B 11-20 years and group C > 20 years. Cartilage explants from group A horses were least and those from group C were most sensitive to LPS. Significant increases in PGE(2) concentration (P < 0.01) were obtained in group C horses in response to LPS concentrations of 1.0 mu g/mL (and higher) after exposure for 24, 36 and 48 h, whereas explants from group A horses failed to respond to LPS at concentrations up to 100 mu g/mL after exposure times up to 48 h. In contrast, synoviocytes from group A horses were most and those from group C horses were least sensitive to LPS stimulation. Synoviocytes from group A horses responded to LPS concentrations of 1 mu g/mL (and higher) with significantly increased concentrations of PGE(2) at 24 and 36 h. Significant but numerically smaller increases in PGE(2) concentration were induced by LPS in synoviocytes from groups B and C. As the effects of high PGE(2) concentrations are catabolic for cartilage, these observations suggest that both synoviocytes and chondrocytes might exert roles in the degenerative changes which occur in cartilage in horses with osteoarthritis.