A human ECM-1 polypeptide and DNA (RNA) encoding such polypeptide and a procedure for producing such polypeptide by recombinant techniques is disclosed. Also disclosed are methods for utilizing such polypeptide for stimulating the differentiation in growth of osteoblasts and osteoclasts, which may be used to promote the healing of bone fractures and de novo bone formation, for osteoporosis, for and to promote angiogenesis. Antagonists to the polypeptide of the present invention are also disclosed which may be utilized to treat osteodystrophy, osteohypertrophy, osteoma, osteoblastoma and cancers. Diagnostic assays for identifying mutations in nucleic acid sequence encoding a polypeptide of the present invention.