Tissue engineering using hydroxyapatite fiber sheet as a scaffold for bone regeneration culturing mesenchymal stem cells, and application for posterolateral spine fusion as a bone graft

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According to the results of in vitro studies using MC3-T3 cells and bone marrow cells in 2002, hydroxyapatite fibers (HAF) might be useful either as a carrier of rhBMP-2 and a scaffold for bone regeneration to support 3D cell proliferation. In 2002, we have made posterolateral fusion model of rats. Using these models, in 2003, we made two studies, 1) to evaluate usefulness of HAF as a carrier of rhBMP-2 in vivo with future implication of clinical use for posterolateral spinal fusion surgery, 2) to evaluate the biological property and usufulness of hydroxyapatite fiber as a scaffold of osteoblast using rat osteoblastic cells in vivo. Experiment 1) Bilateral posterolateral fusion between L5 and 6 was performed to 14week old Wistar rats using HAF containing rhBMP-2 (5, 10, 16μg). Specimens were retrieved and spinal bone fusion was assessed after implantation. Experiment 2) Osteoblastic cells were isolated from skulls of 1day old wistar rats. Diameter of pores and porosity of HAFs used in … More this study were controlled to be 5μm and 95% (S0), 250μm and 99%(52000) respectively. 5×10^6 cells were seeded in each scaffolds. The subcultures were performed for 2weeks. Scaffolds with osteoblastic cells were implanted in the back of 4-week-old athymic mouse at the subcutaneous site. Specimens were retrieved after implantation. Bone formation was evaluated by pathologic findings. Result 1) Bone fusion was observed at 4 weeks in all specimens in the group of 15μg rhBMP-2. Result 2) Enchondral bone formation was found at all the cells cultured in the scaffolds implanted in vivo. S2000 scaffolds were porose and able to support 3D cell proloferation comparing with S0. They could introduce new bone formation inside the scaffolds in vivo. But they decreased in size due to their mechanical fragility. Thus we conclude that HAF is not only an acceptable material for delivering rhBMP-2 to a fusion site, thereby enhancing solid posterolateral spinal fusion, but also a scaffold for bone regeneration to support 3D cell proliferation. Less