Department of Orthodontics, Hokkaido University Graduate School of Dental Medicine, Kita-ku, Sapporo 060-8586, Japan.
Int J Mol Med. 2011 Jul;28(1):73-9. doi: 10.3892/ijmm.2011.675. Epub 2011 Apr 13.
The effects of mechanical stress release on osteoclastogenesis may be as important as those of mechanical stress application. However, the direct effects of mechanical stress on the behavior of osteoclasts has not been thoroughly investigated and there is limited information on the results of the release from mechanical stress. In this study, the effects of mechanical stress application and its release on osteoclast differentiation were examined. The number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts derived from RAW264.7 cells were measured and the expression of osteoclast differentiation genes, which was altered in response to the release from mechanical stress according to the Flexercell tension system was evaluated by real-time PCR. Osteoclast differentiation and fusion were suppressed by mechanical stress application and were rapidly induced after mechanical stress release. The mRNA expression of the osteoclast specific genes, TRAP, matrix metalloproteinase-9 (MMP-9), cathepsin-K (cath-k), calcitonin receptor (CTR), ATPase H+ transporting vacuolar proton pump member I (ATP6i), chloride channel-7 (ClC7) and dendritic cell-specific transmembrane protein (DC-STAMP) was decreased with mechanical stress application, and increased up to 48 h after the release from it. These alterations in gene mRNA expression were associated with the number of osteoclasts and large osteoclasts. Inducible nitric oxide synthetase (iNOS) mRNA was increased with mechanical stress and decreased after its release. Nitric oxide (NO) production was increased with mechanical stress. Nuclear factor of activated T cells cytoplasmic (NFATc) family mRNAs were not altered with mechanical stress, but were up-regulated up to 48 h after the release from it. These findings indicate that the suppression of osteoclast differentiation and fusion induced by mechanical stress is the result of NO increase via iNOS, and that the promotion of osteoclast differentiation and fusion after the release from mechanical stress is related to the NFATc family genes, whose expression remained constant during mechanical stress but was up-regulated after the release from mechanical stress.
机械应力释放对破骨细胞生成的影响可能与机械应力施加同样重要。然而，机械应力对破骨细胞行为的直接影响尚未得到彻底研究，关于机械应力释放的结果信息有限。在这项研究中，研究了机械应力施加及其释放对破骨细胞分化的影响。通过抗酒石酸酸性磷酸酶（TRAP）染色来测量源自 RAW264.7 细胞的多核破骨细胞的数量，并通过实时 PCR 评估 Flexercell 张力系统释放机械应力后，破骨细胞分化基因的表达变化。机械应力施加会抑制破骨细胞分化和融合，而机械应力释放后则会迅速诱导其分化和融合。破骨细胞特异性基因 TRAP、基质金属蛋白酶-9（MMP-9）、组织蛋白酶-K（cath-k）、降钙素受体（CTR）、ATP 酶 H+转运液泡质子泵成员 I（ATP6i）、氯离子通道-7（ClC7）和树突状细胞特异性跨膜蛋白（DC-STAMP）的 mRNA 表达随着机械应力施加而降低，而在其释放后 48 小时内增加。这些基因 mRNA 表达的变化与破骨细胞数量和大型破骨细胞有关。诱导型一氧化氮合酶（iNOS）mRNA 随着机械应力的增加而增加，而在其释放后减少。一氧化氮（NO）的产生随着机械应力的增加而增加。核因子活化 T 细胞胞浆（NFATc）家族的 mRNA 不受机械应力的影响，但在其释放后 48 小时内被上调。这些发现表明，机械应力诱导的破骨细胞分化和融合的抑制是通过 iNOS 增加 NO 的结果，而机械应力释放后促进破骨细胞分化和融合与 NFATc 家族基因有关，这些基因在机械应力期间表达保持不变，但在机械应力释放后上调。
