| Co-Investigator(Kenkyū-buntansha) |
SATO Takuya Meikai University, School of Dentistry, Division of Oral Anatomy, Department of Human, Development and Fostering, Senior Assistant Professor, 歯学部, 講師 (00316689)
MASUHARA Masaaki Meikai University, School of Dentistry, Division of Oral Anatomy, Department of Human, Development and Fostering, Assistant Professor, 歯学部, 助教 (70372901)
|
|---|
| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
|
|---|
| Research Abstract |
Background : Mechanical loading applied to the skeleton is crucial to the development and maintenance of bone integrity and architecture. A decrease in the mechanical loading due to prolonged immobilization or weightlessness in space reduces the bone formation rate, resulting in bone loss. On the other hand, an increase in mechanical loading causes a gain in bone density. Thus, bone tissue is sensitive to mechanical stimulation. Mechanical loading on bone generates extracellular matrix deformation and fluid flow, and the mechanical stimuli are translated to mechanical signals such as mechanical strain and fluid shear stress, respectively. Evidence obtained from in vitro studies indicates that osteocytes embedded in the lacunae/canaliculi system and osteoblasts and bone cells lining the bone surface are mechanosensors that detect load-derived mechanical stimuli. By these bone-forming cells, the mechanical stimuli are translated into cellular signaling factors. However, normal bone metab
… More
olism is achieved by bone remodeling on balance between bone-forming cells and bone-resorbing cells. To date, the effect of fluid shear stress on osteoblasts has been extensively investigated ; however, the action on osteoclasts responsible for bone resorption remains to be elucidated. Therefore, the aim of this study is to elucidate the effect of fluid shear stress on osteoclastogenesis and osteoclast function directly or indirectly via osteoblasts.Methods : We isolated osteoblastic cells from mouse calvaria, and loaded fluid shear stress on these cells with a single flow-through system. In the case of study on osteoclast formation, we employed in vitro culture system of M-CSF dependent bone marrow cells-derived osteoclast progenitors for osteoclast formation dependent on RANKL. Results and Discussion : Isolated mouse calvalia-derived osteoblasts were capable of forming nodules and calcifing in a long-term culture. When the osteoblasts were exposed to fluid shear stress, expression of Cox-2 and RANKL mRNAs was increased as early as 2h after the start of exposure. In addition, gene expression of OPG, a soluble decoy receptor of RANKL, was also increased by the fluid shear stress in the cells ; however, the increase was less than that of RANKL expression. Conditioned medium obtained from the culture of shear stress-loading osteoblasts increased osteoclast formation induced by low concentration of RANKL, whereas the conditioned medium from the stress-unloading osteoblasts did not stimulated the formation. Short-term shear stress loading was sufficient for induction of RANKL gene expression, and the induction maintained even after freeing the loading. The shear stress-induced RANKL expression was dependent on the activation of Erk, but independent of prostaglangin induced by the shear stress. Finally, fluid shear stress directly stimulated the osteoclast formation from osteoclast precursors that were treated with M-CSF and low doses of RANKL. Taken together, fluid shear stress stimulates osteoclastogenesis directly or indirectly via inducing RANKL expression in osteoblasts. Less
|
