Novel bone graft model using bead-cell sheets composed of tricalcium phosphate beads and bone marrow cells

Cells on scaffold implanted in vivo need nutrient and oxygen carried on the blood stream. In this respect, many scaffolds consisting of porous ceramics cannot hold cells alive in the center of them. Therefore, osteogenesis and substitution of regenerated bone occur from the surface of graft, and the biodegradation speed is slow. To solve this problem of lack of blood stream, we developed a new bone graft sheet composed of human bone marrow stromal cells (HMSCs), and beta-tricalcium phosphate (beta-TCP) porous beads. In addition, by combining multilayered bead-cell sheets and collagen gel, we fabricated a bone graft having the space for entry of blood vessels, and implanted them subcutaneously in mice. After 3 weeks, blood vessels reaching to the focal area of graft were recognized, and near the surface of graft, osteogenesis was also observed. In conclusion, the bead-cell sheet would have good osteoconductivity, and the graft made of bead-cell sheets showed a new design concept of bone graft preparing the space for neovascularization.