ABSTRACT
Mechanical forces are essential to life at the microscale — from tethering at the junctions between cells that compose a tissue to externally applied loads arising in the cellular environment. Consider the perturbations from acoustic sounds that affect the mechanosensors on auditory hair cells in the inner ear, the contractile forces that a dividing cell imparts on itself in order to split into two daughter cells during cytokinesis, or the bone and muscle loss that occurs from the reduced loads in microgravity [1,2]. Mechanical forces are particularly important in the cardiovascular and musculoskeletal systems [3]. Increased shear stress in the blood flow leads to the dilation and restructuring of blood vessels [4]. The immune response of leukocytes requires that they adhere to and transmigrate through the endothelial barrier of blood vessels [5]. The forces required between leukocytes and endothelium, and between neighboring endothelial cells, in order to execute such complex events have become an important avenue of research [6,7]. Arterial hypertension causes the underlying vessel walls to constrict, preventing local aneurysms and vessel failure [3]. Longterm exposure to such hypertension leads to increased thickening and stiffing of the vessel walls causing vessel stenosis. In the skeletal system, exercise-induced compressive forces increase bone and cartilage mass and strength while subnormal stresses, from bedrest, immobilization, or space travel, results in decreased bone mass [2]. Despite the clear demonstration that mechanical forces are an essential factor in the daily life of many cells and tissues, the underlying question remains to understand how these forces exert their effects.
