Roles of cell confluency and fluid shear in 3-dimensional intracellular forces in endothelial cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 109; no. 28; pp. 11110 - 11115
• Main Authors: Hur, Sung Sik, del Álamo, Juan C, Park, Joon Seok, Li, Yi-Shuan, Nguyen, Hong A, Teng, Dayu, Wang, Kuei-Chun, Flores, Leona, Alonso-Latorre, Baldomero, Lasheras, Juan C, Chien, Shu
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 10-07-2012; National Acad Sciences
• Series: From the Cover
• Subjects: Animals; atherogenesis; Atherosclerosis; Biological Sciences; Cell adhesion; Cell Communication; Cell lines; Cell motility; Cells; Cells, Cultured - cytology; Cytoskeleton; Deformation; Endothelial cells; Endothelial Cells - cytology; extracellular matrix; Extracellular Matrix - metabolism; Finite Element Analysis; Fluid shear; Fluorescence Resonance Energy Transfer; Humans; Imaging, Three-Dimensional; Intercellular junctions; Mechanical stress; Microscopy; Microscopy, Atomic Force - methods; Microscopy, Confocal - methods; Models, Biological; Models, Statistical; Oscillometry - methods; Physical Sciences; Proteins; Shear Strength; Shear stress; translation (genetics)
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1207326109

We use a novel 3D inter-/intracellular force microscopy technique based on 3D traction force microscopy to measure the cell–cell junctional and intracellular tensions in subconfluent and confluent vascular endothelial cell (EC) monolayers under static and shear flow conditions. We found that z-direction cell–cell junctional tensions are higher in confluent EC monolayers than those in subconfluent ECs, which cannot be revealed in the previous 2D methods. Under static conditions, subconfluent cells are under spatially non-uniform tensions, whereas cells in confluent monolayers are under uniform tensions. The shear modulations of EC cytoskeletal remodeling, extracellular matrix (ECM) adhesions, and cell–cell junctions lead to significant changes in intracellular tensions. When a confluent monolayer is subjected to flow shear stresses with a high forward component comparable to that seen in the straight part of the arterial system, the intracellular and junction tensions preferentially increase along the flow direction over time, which may be related to the relocation of adherens junction proteins. The increases in intracellular tensions are shown to be a result of chemo-mechanical responses of the ECs under flow shear rather than a direct result of mechanical loading. In contrast, the intracellular tensions do not show a preferential orientation under oscillatory flow with a very low mean shear. These differences in the directionality and magnitude of intracellular tensions may modulate translation and transcription of ECs under different flow patterns, thus affecting their susceptibility for atherogenesis.