Effects of cyclic strain on rat tail tenocytes.

Cyclical mechanical strain is considered an important component in flexor tendon cell activation to prevent adhesions and enhance the healing process after tissue injury or surgery, but the biochemical events associated with this remain unclear. To address this, we examined the effects of cyclic tension on the expression of hyaluronic acid, an important lubricant and signal transducer in tendon, on its receptor (CD44), and on total glycosaminoglycan content in rat tail derived tendon fibroblasts in vitro. Tenocytes were plated on fibronectin coated silastic membranes and the cultures were held static or subjected to vacuum induced deformation for a period of 5 min once every 8 h as a model of cyclic mechanical stress. After 24 h medium and cell layers were collected for analyses by product specific ELISA, Western blot, and colorimetric dye-binding assays. Strained tenocytes produced a nearly two-fold increase in hyaluronic acid and a greater than 60% increase in CD44, but had an insignificant effect on total glycosaminoglycan content. Our results predict that high levels of strain may therefore rapidly enhance the expression of hyaluronic acid and cause, albeit still unresolved, downstream effects on CD44 activation, to influence tendon cell activity and enhance the process of tendon repair.