Proteoglycan synthesis by cells cultured from regions of the rabbit flexor tendon.

Rabbit flexor tendons have two distinct biomechanical regions: a compressional region which is characterized by chondrocyte-like cells and abundant matrix, and a tensional region which has a typical tendon morphology with elongated cells, sparse matrix and parallel bundles of collagen fibers. Tissue culture of these regions yields two distinct populations of cells. The compressional cells in vitro synthesize high molecular weight chondroitin sulfate proteoglycan, while the tensional cells synthesize a dermatan sulfate rich, low molecular weight proteoglycan. Immunohistochemical localization utilizing monoclonal antibodies confirms the localization of chondroitin sulfate and keratan sulfate in the compressional regions and its absence in tensional areas. These observations indicate that adult flexor tendon cells in culture continue to express their region-specific phenotypes.