The effect of mechanical strain on hyaluronan metabolism in embryonic fibrocartilage cells

The development of the synovial joint cavity between the cartilage anlagen of the long bones is thought to be mediated by differential matrix synthesi s at the developing articular surfaces. In addition, many studies have show n that removal of movement-induced mechanical stimuli from developing diart hrodial joints prevents cavity formation or produces a secondary fusion of previously cavitated joints. Herein, we describe an inductive influence of mechanical strain on hyaluronan metabolism and the expression of hyaluronan -binding proteins in cultured cells isolated from the articular surface of the distal tibial condyles of 18-day chick embryos. The effect of 10 min of mechanical strain on hyaluronan release into culture media, intracellular uridine diphospho-glucose dehydrogenase activity tan enzyme required for hy aluronan saccharide precursor production), cell surface hyaluronan-binding protein expression and HA synthase mRNA expression were analysed up to 24 h later. Six hours after the application of strain, there was a significant increase in the accumulation of hyaluronan released into tissue culture med ia by strained fibrocartilage cells compared with controls, an effect still detectable after 24 h. Strained cells also showed increased activity for u ridine diphospho-glucose dehydrogenase and expressed higher levels of the h yaluronan-binding protein CD44 at 24 h. In addition, at 24 h mRNA for HA sy nthase 2 was expressed in all samples whereas mRNA for HA synthase 3 was on ly expressed in strained cells. These results further highlight the role fo r movement-induced stimuli in differential extracellular matrix metabolism during joint development and also show that strain may facilitate different ial HA synthase gene expression. (C) 1999 Elsevier Science B.V./Internation al Society of Matrix Biology. All rights reserved.