Immunosuppressant FK506 Induces Osteoporosis In Vivo : Evaluation of Trabecular Bone by Three-dimensional Micro-computed Tomography

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Evaluation of small bones with micro-computed tomography(micro-CT)used to be difficult, because of the relatively poor resolution. During the last several years, however, evaluation of bones in rats and other small animals has become possible, due to rapid advances in three-dimensional(3D)CT. Administration of immunosuppressive agents causes osteoporosis. The extent of osteoporosis and the reason for its occurrence, however, are not clearly understood. We artificially induced osteoporosis in rats by administering an immunosuppressive agent and then measured the bone trabeculae three-dimensionally using high-resolution micro-CT. We also conducted histological examination to observe where osteoporosis started during bone neogenesis and what caused it. We found markedly increased bone resorption and development of osteoporosis in the group given an immunosuppressive agent. Histologically, a marked decrease in sponge bone inferior to enchondral ossification was observed in the experimental group. At the same time, osteoclasts had increased where new bone sprouted, as a result of endochondral ossification. Given the above findings, we conclude that immunosuppressive agents may promote bone resorption and induce osteoporosis by inducing proliferation of osteoclasts.
硬組織再生生物学会の論文