Mechanical stretch leads to increased caveolin-1 content and mineralization potential in extracellular vesicles from vascular smooth muscle cells.

BACKGROUND: Hypertension-induced mechanical stress on vascular smooth muscle cells (VSMCs) is a known risk factor for vascular remodeling, including vascular calcification. Caveolin-1 (Cav-1), an integral structural component of plasma membrane invaginations, is a mechanosensitive protein that is required for the formation of calcifying extracellular vesicles (EVs). However, the role of mechanics in Cav-1-induced EV formation from VSMCs has not been reported.

RESULTS: Exposure of VSMCs to 10% mechanical stretch (0.5 Hz) for 72 h resulted in Cav-1 translocation into non-caveolar regions of the plasma membrane and subsequent redistribution of Cav-1 from the VSMCs into EVs. Inhibition of Rho-A kinase (ROCK) in mechanically-stimulated VSMCs exacerbated the liberation of Cav-1 positive EVs from the cells, suggesting a potential involvement of actin stress fibers in this process. The mineralization potential of EVs was measured by incubating the EVs in a high phosphate solution and measuring light scattered by the minerals at 340 nm. EVs released from stretched VSMCs showed higher mineralization potential than the EVs released from non-stretched VSMCs. Culturing VSMCs in pro-calcific media and exposure to mechanical stretch increased tissue non-specific alkaline phosphatase (ALP), an important enzyme in vascular calcification, activity in EVs released from the cells, with cyclic stretch further elevating EV ALP activity compared to non-stretched cells.

CONCLUSION: Our data demonstrate that mechanical stretch alters Cav-1 trafficking and EV release, and the released EVs have elevated mineralization potential.