Direct bone induction in the subperiosteal space of rat calvaria with demineralized bone allografts

In order to clarify the understanding of bone induction with crude bone morphogenetic protein (BMP)-containing allografts in subperiosteal conditions, chondrogenesis and osteogenesis were histologically evaluated following the implantation of the demineralized bone (DB) in the subperiosteal space of calvaria of 30 Wistar rats. On the forehead of the rat, DB particles were placed onto the denuded calvarial bone and covered by the skin-periosteum flap without any perforations of the marrow space of the calvaria. Sintered hydroxylapatite particles (HA) were also placed as a control. In the DB group, new bone formation on the surface of calvaria was achieved between 2 and 8 weeks after the operation. However, no chondrogenesis was seen throughout the experimental period. In the HA implantation group, fibrous tissue encapsulation of HA particles was generally seen. These results suggest that DB containing crude BMP might have the capacity for direct osteoblast induction from undifferentiated mesenchymal progenitor cells in vivo in specific situations, that is, in a subperiosteal space of uninjured rat calvaria.