The present invention provides methods of repairing and regenerating cartilage tissue using a soluble morphogenic protein complex comprising (a) a morphogenic protein； and (b) a morphogenic protein pro region isolated from a morphogenic protein, or a conservative substitution variant or a fragment of said pro region, wherein said pro region or variant or fragment is noncovalently linked to the morphogenic protein, and wherein said complex is more soluble in an aqueous solvent than said morphogenic protein alone.
