Low-molecular-weight peptides in bone extracts that stimulate osteoblast mitogenesis

Although a majority of regulatory peptides elaborated by neuroendocrine cells are small, i.e., less than 50-60 residues, no low-molecular-weight, bone-derived mitogenic peptides have been described. We have size-fractionated extracts of neonatal mouse calvaria, a rapidly forming bone, and assayed for osteoblast proliferation. Mitogenic peptides with estimated sizes of 1,600, 1,050, and 770 daltons were detected. Their protein nature was demonstrated by the reduction in mitogenic activity following protease treatment. Fibroblast mitogenesis was not stimulated by any of the peptides. These data indicate that there are mitogenic peptides in bone smaller than any previously described locally-derived bone cell growth factor.