Effects of Fluid Shear Stress on a Distinct Population of Vascular Smooth Muscle Cells

Vascular smooth muscle cells (SMCs) are a major cell type involved in vascular remodeling. The various developmental origins of SMCs such as neural crest and mesoderm result in heterogeneity of SMCs, which plays an important role in the development of vascular remodeling and diseases. Upon vascular injury, SMCs are exposed to blood flow and subjected to fluid shear stress. Previous studies have shown that fluid shear stress inhibits SMC proliferation. However, the effect of shear stress on the subpopulation of SMCs from specific developmental origin and vascular bed is not well understood. Here we investigated how shear stress regulates human aortic SMCs positive for neural crest markers. DNA microarray analysis showed that shear stress modulates the expression of genes involved in cell proliferation, matrix synthesis, cell signaling, transcription and cytoskeleton organization. Further studies demonstrated that shear stress induced SMC proliferation and cyclin D1, downregulated cell cycle inhibitor p21, and activated Akt pathway. Inhibition of PI-3 kinase blocked these shear stress-induced changes. These results suggest that SMCs with neural crest characteristics may respond to shear stress in a different manner. This finding has significant implications in the remodeling and diseases of blood vessels.