Effect of bone matrix-derived growth factors on skull and tibia in the growing rat

Aberration in cranial skeletal morphology during growth due to metabolic bone diseases associated with hypocalcemia is related to abnormalities in cranial suture growth. It was found in previous experimental studies that a changed cranial growth pattern induced by hypocalcemia and secondary hyperparathyroidism was dependent on a decreased bone apposition in viscerocranial growth sites. Of interest was the observation that obliterative osteogenesis occurred with this disturbance. In vitro studies have shown that when bone resorption is stimulated by parathyroid hormone, mitogenic factors for bone cells are released from the matrix. The aim of the current study was to elucidate a possible local regulatory mechanism for bone growth especially with regard to cranial growth. Two groups of young rats were injected daily with 150 micrograms and 750 micrograms respectively of bone matrix-derived growth factor preparation (BMDGF) for 2 weeks. By using cephalometric analysis, the BMDGF administration was shown to alter skull morphology during growth. Since the high doses of BMDGF caused markedly more changes than the low dose, the overall effect on craniofacial growth seemed to be dose dependent. The high dose of BMDGF induced a decrease in cortical bone apposition found in this region, as well as in the diaphysis of the tibia. Also a change in position of the viscerocranium in relation to the cranial base was found in the BMDGF-treated rats: the flexure between the viscerocranium and the cranial base being greater compared with the normal skull. This change in relationship seemed to be related to the enhanced bone apposition found in the viscerocranial sutures of BMDGF-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)