Bone morphogenetic protein-induced muscle- and synovium-derived cartilage differentiation in vitro.

Muscle- and synovium-derived mesenchymal-type cells differentiated into cartilage in response to a coating of partially purified rabbit bone morphogenetic protein (BMP) on a substratum of plastic. Observed by means of phase contrast microscopy, light microscope histochemistry, and electron microscopy, the sequence of events on a BMP-coated plastic substratum is the same as that observed on a substratum of bone matrix. The plastic eliminates the possibility of any endogenous allogeneic matrix-derived BMP contaminating the system. The differentiation of cartilage from synoviocytes and subsynovial cells resembles the pathologic process occurring in human chondromatosis.