Polypeptide cartilage-inducing factors found in bone

A method for inducing cartilage and bone formation for repairing, replacing, and or augmenting cartilage and bone tissue in animals, which method comprises:

• administering to a mammal in need of bone repair, replacement, or augmentation a composition comprising a TGF-beta activating agent, a pharmaceutically acceptable excipient, and a polypeptide the (a) is found in mammalian bone, (b) is active in the TGF-beta assay, (c) is a co-factor for inducing cartilage formation in vivo, (d) is a dimer having an approximate molecular weight of 26,000 daltons as determined by SDS-PAGE, and (e) is substantially pure, wherein said polypeptide and activating agent are present in amounts sufficient to promote bone growth.

A method for treating osteoporosis or osteopetrosis, which comprises:

• systemically administering an effective amount of a composition comprising a TGF-beta activating agent, a pharmaceutically acceptable excipient, and a polypeptide that (a) is found in mammalian bone, (b) is active in the TGF-beta assay, (c) is a co-factor for inducing cartilage formation in vivo, (d) is a dimer having an approximate molecular weight of 26,000 daltons as determined by SDS-PAGE, and (e) is substantially pure, wherein said polypeptide and activating agent are present in amounts sufficient to promote bone growth.