Type I, II and X Collagen Gene Expression Pattern in Bone Formation Using rh-BMP2

Bone morphogenic protein (BMP) induces ectopic bone. In that process, there are some tissue-specific collagens (type I, II and X) in osteocartilagenous matrix. And these types of collagen are also observed in the process of ossification in condylar cartilage. We searched for the localization of collagen gene expression in ectopic bone induction using rh-BMP and condylar cartilage ossification. BMP-type I collagen complex were implanted into the subcutaneous tissue of the dorsal region of ICR mice. Then we made specimens 3 days, 1week, and 2weeks after implanting. For condylar cartilage, we pick out condylar region from ICR mice, and made specimens. The probes was made from mouse type I, II and X collagen cDNA segment (kikindly provided by Dr. Ninomiya of Okayama Universy). The process of ectopic bone induction using rh-BMP was the process through the intermediary of rapidly formed cartilagenoid tissue. And there are some difference of type I, II and X collagen gene expressions between the process using rh-BMP and that of condylar cartilage. Those gene expressions imply that the ectopic hard tissue formative cells induced in early stage will take on the characters of osteoblasts and chondrocytes, and that the cells in growing cell layer in cartilagenoid tissue can differentiate into both osteoblasts and chondrocytes.