Aging Alters Functional Properties Of Cell-Matrix Adhesions In Vascular Smooth Muscle Cells

Vascular smooth muscle (VSM) cell mechanical properties and their ability to adapt to external mechanical signals directly contribute to maintain vascular contractility. Aging is associated with an impaired ability of VSM cells to develop contractile tension. This study aims to investigate aging effects on integrin-mediated adhesion to the matrix in VSM cells isolated from soleus muscle feed arteries from young (4 mo) and old (24 mo) Fischer 344 rats. Total internal reflection fluorescence imaging of young and old fixed VSM cells stained with specific antibodies for vinculin, pFAK397, integrins α5 and β3 showed that morphology of cell-matrix adhesions is age-dependent. Young cells presented well-defined streak-like adhesions rich in vinculin distributed all over the basal cell area, while old cells presented smaller adhesions distributed mostly toward the cell edges. Quantitative analysis of fluorescence images showed that the protein area for both pFAK and vinculin was two-fold lower in old cells compared with young cells. In addition, integrin α5 localization at cell-matrix adhesions decreased in old cells, while no change was found in integrin β3 localization at peripheral adhesions. Moreover, atomic force microscopy functional measurements of integrin α5β1 binding to fibronectin show that both adhesion force to the matrix and adhesion probability were increased in old cells. Taken together, these data suggest that aging is associated with a reduction in proteins essential for VSM cell adhesion, while the increase in integrin α5β1 binding to the matrix is most likely a compensatory mechanism to maintain cell-matrix attachment in aged cells.