The role of cell cortex structures in mechanical stress signal transduction 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，在缝合处的成熟成骨细胞中，肌动蛋白在细胞皮层中积累。在成骨前细胞和成纤维细胞中，肌动蛋白表现为应力纤维样结构。在成纤维细胞中比在成骨前细胞中更厚。在拉应力作用3、6小时后，缝合线内的细胞沿拉应力方向被拉伸拉长。肌动蛋白-细胞骨架的形态变化与细胞形态的变化一致。拉伸应力缝合6小时时细胞肌动蛋白应力纤维样结构厚度和肌动蛋白细胞皮层厚度增加，3小时时无明显增加。钙粘蛋白是一种细胞黏附分子，在任何实验过程中沿成骨细胞皮层均可见到钙粘蛋白。另一方面，拉伸应激组成骨细胞中β-catenin和vinculin沿细胞皮层的免疫活性增强。

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 were 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 confocal laser scanning microscopy, with others being observed with TEM. The results show that in the mature osteoblasts in the suture, actin was accumulated in the cell cortex. In the preosteoblastic cells and fibroblastic cells, actin was observed as stress fiber-like structures. Those were thicker in fibroblastic cells than in the preosteoblastic cells. With the tensile stress for 3 or 6 hours, all the cells in the sutures were stretched and elongated in the direction of the tensile stress. Morphological change of actin-cytoskeleton was observed consistent with the change of the cell shape. Thickness of the actin stress fiber-like structure and actin cell cortex were increased in the cells of the tensile stressed suture for 6 hours, but they were not clearly increased in the 3 hour-stressed group. Cadherin, one of the cell adhesion molecules, was observed along the cell cortex of osteoblasts at any experimental time course. On the other hand, immunological activities of β-catenin and vinculin became intense along the cell cortex in the osteoblasts of the tensile stressed groups.