Possible roles of adhesion complex and cytoskeleton as a mechano-receptor in osteoblasts.

拉伸应力（TS）已被证明可以刺激小鼠颅骨缝合线的成骨。为了阐明粘附复合物和细胞骨架在这一机制中的作用，我们研究了这种应激缝合细胞的形态学变化。将TS应用于培养新生小鼠颅骨缝合。其中一些用Alexa phalloidin染色，用共聚焦激光扫描显微镜观察其肌动蛋白纤维，另一些用透射电镜观察。结果表明，在颅骨缝线的成骨层中，TS引起肌动蛋白纤维形态学改变，主要发生在骨边缘的成骨细胞，以及位于缝线中心的细胞。此外，我们之前证明了TS诱导蛋白质的产生，以及α-适应蛋白C基因在加载开始后的表达。原位杂交和免疫组织化学分析显示，α-适应蛋白C的诱导主要发生在缝合线的成纤维细胞中，提示其在ts诱导成骨细胞分化之前发生。与此结果一致的是，TS显著增加了未分化成纤维细胞的包被凹坑和包被囊泡的数量，而在颅骨周围的成骨细胞中则没有。这些结果表明，TS加速成骨细胞分化和成骨，可能是通过诱导α-适应蛋白C的表达和随后受体介导的内吞作用的激活。

Tensile stress(TS) has been shown, to stimulate osteogenesis in the cranial suture of mouse calvaria. In order to clarify the role of the adhesion complex and cytoskeleton in this mechanism, the morphological changes in such stressed suture cells was investigated.TS was applied to the cranial suture of neonatal mouse calvaria in culture. Some were stained with Alexa phalloidin and their actin fibers observed with con focal laser scanning microscopy, with others being observed with TEM. The results show that in the osteogenic layers of the cranial suture, TS causes actin-fiber morphological change, principally in the osteoblasts located at the bone edge, as well as in the cells located in the center of the suture.Furthermore, we previously demonstrated that TS induced protein production, as well as the gene expression of α-adaptin C following the initiation of loading. In situ hybridization and immunohistochemical analysis revealed that the induction of α-adaptin C mostly occurred in fibroblastic cells in the sutures, suggesting that it precedes TS-induced osteoblast differentiation. Consistent with this result, TS significantly increased the number of coated pits and coated vesicles in the undifferentiated fibroblastic cells but not in the osteoblastic cells around calvarial bones. These results, taken together, suggest that TS accelerates osteoblast differentiation and osteogenesis, possibly through the induction of the α-adaptin C expression and consequent activation of receptor-mediated endocytosis.