| Co-Investigator(Kenkyū-buntansha) |
AMIZUKA Norio Niigata University, School of Dentisty, Research, Associate, 歯学部, 助手 (30242431)
NAKAMURA Hiroaki Niigata University, School of Dentisty, Research, Associate, 歯学部, 助手 (50227930)
IRIE Kazuharu Niigata University, School of Dentisty, Research Associate, 歯学部, 助手 (70223352)
EJIRI Sadakazu Niigata University, School of Dentisty, Associate Professor, 歯学部, 助教授 (40160361)
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| Research Abstract |
[Studies on aging in bone tissue using new bone morphometrical methods] In order to establish the basic system for the research on aging phenomena in the jaw bone, we developed a new morphometrical method using confocal laser microscope and applied muCT on the bone morphometrical studies. From the results using the system, it is demonstrated that the bone loss occurred in mandibular condyle following estrogen deficiency and the condyle maintained the bone mass with dynamic structural alterations, due to regionally different reactivity against estrogen deficiency and the bone formative stimulus by occlusal force. [Histochemical studies on aging bones] With advancing age, the mandibular chondylar cartilage, which produced type II collagen fibers, became fibrocartilage-like tissue which produced type I collagen fibers. Hypertrophic chondrocytes in the condyle disappeared in the course of aging. Adipocytes were found prominently in the bone marrow of aged rat. From these results, it is sug
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gested that aging phenomena in bone tissue occurred through the control mechanisms in proliferation and differentiation of chondrocytes, osteoblasts and osteoclasts. [Molecular and cell biological studies on aging bones] Using the in situ hybridization method, we assessed the changing of the gene expression patterns in bone tissue with advancing age. In bones of OVX rats and PTHrP gene-knock out mice, gene expression patterns of osteonectin, ALPase, PTHrP, FGF and their receptor were suppressed in the course of aging. Gene expression patterns in bones with advancing age may change in association with the suppression of cell differentiation. [Inducing bone experiments] In order to prevent and recover the bone loss which occurred with aging, we assessed the effects of intermittent administration of PTH and implantation of BMP-2 pellets on mandibles of experimental animals. The preventive and therapeutic intermittent administrations of PTH in ovariectomized rats increased the bone formation in rat mandibular condyle without accelerating bone resorptive activity. When BMP-2 pellets were implanted into the extracted teeth cavities, proliferation of mesenchymal cells and differentiation of preosteoblasts into osteoblasts were induced and rapid bone formation occurred in the cavities. Furthermore, application of e-PTFE membrane after the implantation of BMP-2 pellets was effective to form the new bone into the designed bone shape. Less
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