Morphometrical, Histological and Ultrastructural Analyses of Bone Formation and Resorption Induced by Synthetic Octacalcium Phosphate in Mouse Bone Marrow

抄録

Objective: Octacalcium phosphate (OCP) is thought to be a precursor of the mineral crystals in biological apatite. Synthetic OCP has been shown to be converted into an apatite structure when implanted in murine calvarial bone, to enhance bone regeneration. This study was designed to investigate whether OCP implantation enhances the formation and resorption of new bone when implanted intramedullary in a mouse bone marrow.
Design: Histological and ultrastructural analyses of bone formation and resorption after 2, 4 and 6 weeks implantation was investigated. MicroCT analysis was also applied to detect the amount of newly formed bone mass after implantation.
Results: Massive bone formation on OCP was detected at 2 weeks. Then, the amount of bone was decreased gradually until 6weeks. At 4 and 6 weeks, many multinucleated giant cells, including tartrate-resistant acid phosphatase (TRAP)-positive cells, were detected on the newly formed bone and synthetic OCP. Ultrastructural study indicated that the multinucleated giant cells attached either to the bone and OCP surface were osteoclasts forming the clear zones and ruffled borders composed of finger-type and platetype cell processes. However, the ultrastructure of cell processes in ruffled borders showed the irregular shape. No representative cell processes were detected in the cells.
Conclusion: These results confirmed the active induction of bone formation and resorption on OCP and also suggested that the structure of ruffled border might be regulated by the target calcified materials.