Experimental studies on the pathogenesis of ochronotic arthropathy

Publisher Website
Google Scholar
Abstract
Lapine adult and fetal articular chondrocytes in monolayer culture were employed as an experimental model for studying the effects of homogentisic acid on chondrocyte morphology, proliferation and synthesis of proteoglycans. Concentrations of homogentisic acid in the range from 0.1 to 100 μg/ml were investigated and a cytotoxic effect was detected with concentrations of 5 μg/ml and above. Thus, with adult articular chondrocytes this effect was seen between 36 and 48 h of subculture with 5 μg/ml or more of homogentisic acid present from the beginning of subculture. In fetal articular chondrocyte cultures a concentration of 1 μg/ml elicited a statistically significant reduction (13%) in cell proliferation without altering sulphated macromolecular synthesis. Experiments with3H-thymidine autoradiography to measure the pulse labelling index (LI) in fetal chondrocytes in vitro showed that the 5 μg/ml concentration of homogentisic acid present for 21 h from the beginning of subculture gave a LI of 2%, compared with 25% for controls. Thus, homogentisic acid can reduce chondrocyte proliferative capacity before morphological alterations can be detected by light microscopy. No significant alterations in the synthesis of proteoglycans were detected at concentrations below the cytotoxic level. The homogentisic acid-induced cytotoxicity and reduction of proliferation in chondrocytes represents a possible pathway by which cartilage is damaged in ochronotic arthropathy.