Measurement of mechanical properties of vascular smooth muscle cells as a model of functional materials

血管平滑肌细胞不仅通过收缩舒张改变血管直径，而且通过产生胶原等细胞外基质重塑血管壁。它们的收缩特性和基质合成随着施加于它们的机械刺激而改变：例如，它们的收缩速度随着重复收缩而增加，当细胞保持收缩时，维持它们等距收缩所需的能量减少。因此，平滑肌细胞作为一种功能材料具有有趣的特性。在这项为期三年的研究中，我们在单个细胞水平上检测了血管平滑肌细胞的机械特性和收缩特性，以阐明它们与机械刺激的关系。第一年，我们发现从高血压大鼠胸主动脉分离的平滑肌细胞的弹性模量约为正常主动脉的一半。第2年，我们发现兔胸主动脉平滑肌细胞收缩时弹性模量增加了10倍。在去年，我们研究了细胞的拉伸性能与细胞内肌动蛋白丝的数量之间的关系：我们首先测量了从正常血压的大鼠胸主动脉（FSMCs）新鲜分离的平滑肌细胞和相同来源的培养细胞（通道4-9，CSMCs）的拉伸性能。然后，我们用罗丹明-phalloidin对细胞进行肌动蛋白丝染色，以了解FSMCs和CSMCs之间肌动蛋白丝数量的差异。FSMCs的初始弹性模量约为11 kPa (N=8)， CSMCs的初始弹性模量约为2.6 kPa （N=10）。FSMCs中肌动蛋白丝在胞浆中丰富，难以区分，而CSMCs中肌动蛋白丝分布稀疏，应力纤维明显，表明CSMCs中肌动蛋白丝数量减少。这种肌动蛋白丝数量的差异可能导致细胞力学性能的差异。在下一步的研究中，我们将定量分析肌动蛋白丝用量与力学性能之间的关系。少

Vascular smooth muscle cells not only change blood vessel diameter through their contraction and relaxation, but also remodel blood vessel wall by producing extracellular matrices such as collagen. Their contractile properties and matrix synthesis change in response to the mechanical stimuli applied to them : For example, their contractile velocity increases with repetitive contraction, and the energy necessary to maintain their isometric contraction decreases when the cells are kept contracted. Thus, the smooth muscle cells have interesting characteristics as a functional material. In this three-year study, we have examined the mechanical properties and the contractile properties of the vascular smooth muscle cells in a single cell level to clarify their relationship with the mechanical stimuli. In the first year, we found that the elastic modulus of the smooth muscle cells isolated from the hypertensive rat thoracic aorta was about one half of that of the normotensive aorta. In the s … More econd year, we found that the elastic modulus of the smooth muscle cells obtained from the rabbit thoracic aorta increased by the factor of 10 when they got contracted. In the last year, we examined the relationship between the tensile properties of the cell and the amount of their intracellular actin filament : We first measured the tensile properties of the smooth muscle cells freshly isolated from the normotensive rat thoracic aortas (FSMCs) and those of the cultured cells of the same origin (Passage 4-9, CSMCs). Then, we stained the cells with rhodamine-phalloidin for actin filaments to know the difference in the actin filament amount between the FSMCs and the CSMCs. The initial elastic modulus of the cells was about 11 kPa (N=8) for FSMCs and about 2.6 kPa (N=10) for CSMCs. The actin filaments in the FSMCs were abundant in the cytosol and it was hard to distinguish each filaments, while in the CSMCs, the filaments were sparsely distributed and stress fibers are clearly distinguishable, indicating that the decrease in the actin filament amount in the CSMCs. Such difference in the actin filament amount may cause the difference in the mechanical properties of the cells. We should analyze quantitatively the relationship between the actin filament amount and the mechanical properties in the next study. Less