Immobilized recombinant human bone morphogenetic protein‐2 enhances the phosphorylation of receptor‐activated Smads

Abstract Bone morphogenetic protein (BMP)‐2 plays an important role in bone growth and regeneration; however, BMP‐2 is easily lost by diffusion through body fluid and has some inhibitory pathways. To address this problem, we previously immobilized recombinant human BMP‐2 (rhBMP‐2) on succinylated type I atelocollagen. Here, we examined the effect of immobilized rhBMP‐2 in vitro and vivo. In ST2, MC3T3‐E1, and C2C12 cells, alkaline phosphatase activity, which is a marker of osteoblast differentiation, was enhanced more by immobilized than nonimmobilized rhBMP‐2. In addition, the phosphorylation of receptor‐activated Smads, part of the signaling pathway activated by BMP‐2, was prolonged by immobilized rhBMP‐2 in these cells. Furthermore, implantation of immobilized rhBMP‐2 into the backs of rats promoted the formation of mature bone‐like structure. These results demonstrate that immobilized rhBMP‐2 has higher bioactivity than nonimmobilized rhBMP‐2, and, therefore, immobilization of rhBMP‐2 can prolong BMP signaling. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009