Regulation of Vascular Smooth Muscle Cell Turnover by Endothelial Cell-secreted MicroRNA-126: Role of Shear Stress
Rationale: Endothelial microRNA-126 (miR-126) modulates vascular development and angiogenesis. However, its role in the regulation of smooth muscle cell (SMC) function is unknown.
Objective: To elucidate the role of miR-126 secreted by endothelial cells (ECs) in regulating SMC turnover in vitro and in vivo, as well as the effects of shear stress (SS) on the regulation.
Methods and Results: Co-culture of SMCs with ECs or treatment of SMCs with conditioned media from static EC monoculture (EC-CM) increased SMC miR-126 level and SMC turnover; these effects were abolished by inhibition of endothelial miR-126 and by the application of laminar SS (LSS) to ECs. SMC miR-126 did not increase when treated with EC-CM from ECs subjected to inhibition of miR biogenesis, nor with CM from sheared ECs. Depletion of extracellular/secreted vesicles in EC-CM did not affect the increase of SMC miR-126 by EC-CM. Biotinylated miR-126 or FLAG-tagged Ago2 transfected into ECs were detected in the co-cultured or EC-CM treated SMCs, indicating a direct EC-to-SMC transmission of miR-126 and Ago2. Endothelial miR-126 represses FOXO3, BCL2, and IRS1 mRNAs in the co-cultured SMCs, suggesting the functional roles of the transmitted miR-126. Systemic depletion of miR-126 in mice inhibited neointimal lesion formation of carotid arteries induced by cessation of blood flow. Administration of EC-CM or miR-126 mitigated the inhibitory effect.
Conclusions: Endothelial miR-126 acts as a key intercellular mediator to increase SMC turnover, and its release is reduced by atheroprotective LSS.
- Received September 4, 2012.
- Revision received April 16, 2013.
- Accepted April 19, 2013.