Role of fibronectin in collagenous matrix-induced mesenchymal cell proliferation and differentiation in vivo

The importance of fibronectin in in vivo collagenous matrix-mesenchyme cell interaction was investigated using purified antibodies to rat plasma fibronectin. Subcutaneous implantation of demineralized bone matrix normally resulted in de novo local endochondral ossification. Local injections of the purified antibodies apparently inhibited collagenous matrix-mesenchyme cell interaction by inhibiting the action of endogenous fibronectin. Anti-fibronectin treatment resulted in reduced cell proliferation as assessed by [ 3H]thymidine incorporation (59%, reduction) and ornithine decarboxylase activity (66%, reduction); and chondrogenesis as measured by proteoglycan synthesis (43%, reduction). Neutralization of fibronectin's biological activity by antibodies also resulted in a qualitative change in the proteoglycan type synthesized. The physiological role of fibronectin in tissue morphogenesis appears to allow for initial extracellular matrix-cell attachment