Transforming growth factor-beta 2 enhances the osteoinductive activity of a bovine bone-derived fraction containing bone morphogenetic protein-2 and 3.
We previously identified a novel glycoprotein in an osteoinductive fraction from bovine bone (Bentz et al.: Amino acid sequence of bovine osteoinductive factor. J. Biol. Chem. 265: 5024-5029, 1990). We now find that this fraction also contained small amounts of bone morphogenetic protein-2 and 3 (BMP-2 + 3) previously identified by others (see Wozney, J.M.: Bone morphogenetic proteins. Prog. Growth Factor Res. 1: 267-280, 1990). Separation of BMP-2 + 3 from the glycoprotein was achieved with a modified reversed phase-high pressure liquid chromatographic procedure. When assayed in the rat subcutis using a collagen-ceramic carrier, the osteoinductive activity was found in the subfraction containing BMP-2 + 3. This activity was potentiated and the ratio of cartilage to bone was increased by transforming growth factor-beta 2. The glycoprotein, originally called osteoinductive factor, has been renamed osteoglycin. In its precursor form, osteoglycin is a member of the leucine-rich family of proteins showing the characteristic 24-residue internal homology. Its biological function is unknown.