Department of Cell Signaling, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
Department of Orthodontic Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
Sci Rep. 2019 Mar 20;9(1):4404. doi: 10.1038/s41598-019-40463-3.
Bone undergoes a constant reconstruction process of resorption and formation called bone remodeling, so that it can endure mechanical loading. During food ingestion, masticatory muscles generate the required masticatory force. The magnitude of applied masticatory force has long been believed to be closely correlated with the shape of the jawbone. However, both the mechanism underlying this correlation and evidence of causation remain largely to be determined. Here, we established a novel mouse model of increased mastication in which mice were fed with a hard diet (HD) to elicit greater masticatory force. A novel in silico computer simulation indicated that the masticatory load onto the jawbone leads to the typical bone profile seen in the individuals with strong masticatory force, which was confirmed by in vivo micro-computed tomography (micro-CT) analyses. Mechanistically, increased mastication induced Insulin-like growth factor (IGF)-1 and suppressed sclerostin in osteocytes. IGF-1 enhanced osteoblastogenesis of the cells derived from tendon. Together, these findings indicate that the osteocytes balance the cytokine expression upon the mechanical loading of increased mastication, in order to enhance bone formation. This bone formation leads to morphological change in the jawbone, so that the bone adapts to the mechanical environment to which it is exposed.
骨骼经历一个不断的吸收和形成的重建过程，称为骨重建，以使它能够承受机械加载。在进食过程中，咀嚼肌产生所需的咀嚼力。施加的咀嚼力的大小长期以来一直被认为与颌骨的形状密切相关。然而，这种相关性的潜在机制和因果关系的证据仍在很大程度上有待确定。在这里，我们建立了一个新的磨牙增加的小鼠模型，其中用硬饮食（HD）喂养小鼠以产生更大的咀嚼力。一种新的计算机模拟表明，咀嚼负荷作用于颌骨导致了在具有强大咀嚼力的个体中看到的典型骨轮廓，这通过体内微计算机断层扫描（micro-CT）分析得到了证实。从机制上讲，增加的咀嚼引起胰岛素样生长因子（IGF）-1 的增加和破骨细胞中骨硬化蛋白的抑制。IGF-1 增强了来自肌腱的细胞的成骨细胞生成。总之，这些发现表明，成骨细胞在增加的咀嚼力的机械加载下平衡细胞因子的表达，以增强骨形成。这种骨形成导致颌骨的形态变化，从而使骨骼适应其暴露的机械环境。
