Vascular smooth muscle cells' response to mechanical stimuli

Abstract

Vascular smooth muscle cells (VSMCs), embedded in arterial media, are normally shielded from direct shear force of flowing blood and are exposed to blood flow after the vascular injury. Because of the importance of intercellular Ca^<2+> in regulating vascular tone and functions, we investigated the effect of fluid flow shear stress on the concentration of intercellular Ca^<2+> of human aortic smooth muscle cells (HASMCs). To address the effect of fluid flow shear stress on intercellular Ca^<2+> concentration, confluent HASMCs were grown on Petri dishes, loaded with aequorin, a Ca^<2+>-activated photoprotein, and the dish was placed in a homemade luminometer chamber after a physiological level of shear stress was imposed on the surface of HASMCs. The luminometer chamber housed inside a highly sensitive photomultiplier tube (PMT) and detected light emission in response to intercellular Ca^<2+> concentration transient. In the presence of 2.0mM extracellular Ca^<2+> shear stress of 16ynes/(cm)^2 induction for 1 minute on the surface of HASMCs elicited a sharp increase followed by plateau elevation of lesser magnitude in the concentration of intercellular Ca^<2+>. Addition of thapsigargin (50nM), an intercellular Ca^<2+>-store blocker, also elicited a peak increase in the Ca^<2+> concentration. Taken together, results suggest that influx of Ca^<2+> through ion channels contributes to the rise in cytosolic Ca^<2+> concentration in response to fluid flow shear stress.