Immunohistochemical observations of cellular differentiation and proliferation in endochondral bone formation from grafted periosteum: expression and localization of BMP-2 and-4 in the grafted periosteum

Purpose: To clarify the involvement of bone morphogenetic proteins (BMPs) in the proliferation and differentiation of osteo/chondrogenic cells during the process of bone formation from grafted periosteum. Material and Methods: Tibial periosteum of young Japanese white rabbits was grafted into suprahyoid muscles and removed after 7, 9, 14 or 21 days. BMP-2, -4, proliferative cell nucleus antigen (PCNA) immunoreaction and Alcian blue staining in grafted periosteum was then sought microscopically. Results: PCNA positive cells in the grafted periosteum expressed BMP-2 at 7 days. These cells differentiated into chondroblasts that expressed BMP-2 and Alcian blue at 9 days. After 14 days, cartilage formation was seen, and BMP-2 and -4 expressions were observed in mature and hypertrophic chondrocytes. Endochondral ossification was observed at 21 days and osteoblasts showed both BMP-2 and 4 expression. Conclusion: Both BMP-2 and -4 appear to play regulatory roles in the process of endochondral ossification from grafted periosteum, due to their involvement in the proliferation and differentiation into chondrogenic and osteogenic cells. (C) 2003 European Association for Cranio-Maxiflofacial Surgery.