Proteoglycan synthesis by fibroblasts from different regions of bovine tendon cultured in alginate beads

The ability of cell shape to modulate proteoglycan synthesis in tendon fibr oblasts was investigated by placing freshly isolated tendon fibroblasts and chondrocytes into primary culture either as adherent cells on a polystyren e substratum or as rounded cells in alginate beads. Chondrocytes and cells from the compressed region of adult tendon synthesized predominantly large proteoglycan when maintained either as dense monolayers;, where actin stres s fibers in the cytoskeleton were prominent, or in alginate beads, where ac tin fibers could not be detected. After three rounds of proliferation as el ongated adherent cells the synthesis of large proteoglycan was greatly redu ced, i.e. the chondrocytic cells underwent 'dedifferentiation', Cells from the tensional region of adult tendon synthesized predominantly small proteo glycan when in primary culture as a monolayer, after proliferation on a fla t substratum. or as round cells in alginate beads. Fibroblasts from the ten sional region of newborn tendon showed no tendency toward increased synthes is of large proteoglycan when maintained as round cells in alginate beads f or 7 weeks. In tendon there appears to be a mechanically induced developmen tal transition from fibroblastic to chondrocytic cells. However, neither th e change to a rounded cell shape nor the lack of organized cytoskeletal act in fibers was sufficient to induce chondrocyte-like proteoglycan synthesis in differentiated tendon fibroblasts in culture. (C) 1998 Elsevier Science Inc. All rights reserved.