Measurements of endothelial cell-to-cell and cell-to-substrate gaps and micromechanical properties of endothelial cells during monocyte adhesion.

The interaction between monocytes and endothelial cells is considered to play a major role in the early stage of atherosclerosis, and the involved endothelial cell micromechanics may provide us with important aspects of atherogenesis. In the present study, we evaluated (i) the endothelial cell-to-cell and cell-to-substrate gaps with the electric cell-substrate impedance sensing system, which can detect the nanometer order changes of cell-to-cell and cell-to-substrate distances separately, and (ii) the endothelial cell micromechanical properties with an atomic force microscope after application of monocytes to endothelial cells. Application of monocytic THP-1 cells to IL-1beta-stimulated human umbilical vein endothelial cells immediately decreased the electrical resistance of the endothelial cell-to-substrate (increase of the cell-to-substrate gap), whereas the endothelial cell-to-cell resistance (cell-to-cell gap) did not change. The elastic modulus of the endothelial cells decreased after 2-h monocyte application, indicating an increase of endothelial cell deformability. In conclusion, the interaction of the monocytes to the endothelial cells reduced the adhesiveness to the substrate and increased the deformability of endothelial cells. These changes in the adhesiveness and the deformability may facilitate migration of monocytes, a key process of atherogenesis in the later stage.