Liu S Q, Yen M, Fung Y C
Institute for Biomedical Engineering, University of California at San Diego, La Jolla 92093-0412.
Proc Natl Acad Sci U S A. 1994 Sep 13;91(19):8782-6. doi: 10.1073/pnas.91.19.8782.
The stress in the endothelial cells induced by blood flow depends on the waviness of the blood-endothelium interface and the slopes at the junctions of neighboring cells in the direction of flow. The height and slope in the third dimension of the living endothelial cells cannot be measured by ordinary optical and electron microscopy. Here we show that interference microscopy meets the challenge. We measured the geometry of cultured confluent human vascular endothelial cells in a flow, and we found that in a normal section parallel to the flow, the absolute values of the surface slopes at the cell junctions were 0.70 +/- 0.02 (SE) and 0.80 +/- 0.02 (SE) at the leading and trailing edges of the cells, respectively, in a culture medium of osmolarity 310 mosM with a shear stress of approximately 1 N/m2. A reversal of the flow direction led to a reversal of the slope pattern. An increase in medium osmolarity above 310 mosM induced an initial decrease in the slopes followed by a return to normal, whereas a decrease in the osmolarity had a reversed effect. These results, in light of our previous theoretical analyses, show that tensile stress exists in the endothelial cell membrane, and that the mechanism of tension accumulation is a reality. The accumulation is not 100% because the membranes are not smooth at the cell junctions.
血流在内皮细胞中诱导产生的应力取决于血液 - 内皮界面的起伏程度以及相邻细胞在血流方向上连接处的斜率。活体内皮细胞三维空间中的高度和斜率无法通过普通光学显微镜和电子显微镜进行测量。在此我们表明干涉显微镜能够应对这一挑战。我们测量了流动状态下培养的汇合人血管内皮细胞的几何形状，发现在与血流平行的正常切片中，在渗透压为310 mosM且剪切应力约为1 N/m²的培养基中，细胞连接处表面斜率的绝对值在细胞前缘和后缘分别为0.70±0.02（标准误）和0.80±0.02（标准误）。血流方向的反转导致斜率模式的反转。培养基渗透压高于310 mosM时，斜率最初会降低，随后恢复正常，而渗透压降低则会产生相反的效果。根据我们之前的理论分析，这些结果表明内皮细胞膜中存在拉伸应力，并且张力积累机制是实际存在的。由于细胞膜在细胞连接处并不平滑，所以积累并非100%。
