Differences in morphology, cytoskeletal architecture and protease production between zone II tendon and synovial fibroblasts in vitro

Fibroblast migration is an integral component of the processes resulting in the formation of restrictive adhesions in the injured tendon, especially in Zone II. Pre-requisites for cell migration are an intact cytoskeleton and an ability to biochemically degrade the extra-cellular matrix. The relative characteristics of fibroblasts from the fibro-osseus sheath (SC), the tissue surrounding the tendon in Zone II, and the endotenon (TC) with respect to morphology, cytoskeletal structure and ability to produce matrix metalloproteinases (MMP's) 2 and 9 were compared in vitro. It was found that SCs were larger in size and demonstrated greater amounts of intra-cellular alpha-smooth muscle actin (alpha-SMA) and intra-membranous vinculin. Filamentous actin (F-actin) fibres in SCs were more densely packed and concentrated, resulting in stress fibres. The SCs also produce greater amounts of MMP-2 and MMP-9 compared to TCs. These observations imply that SCs play an active role in adhesion formation and should be specifically targeted to inhibit or treat tendon adhesions.