Shear stress plays a role in differentiation and migration of adventitial fibroblasts

Rat aortic fibroblasts were cultured either subconfluent (<20%) or confluent (>80%). Western blotting was conducted to evaluate the amount of two phenotype markers of smooth muscle cells (SMCs), SM alpha-actin (alpha-SMA) and SM myosin heavy chain (SM-MHC). The results showed thatwere native fibroblasts and confluent fibroblasts were myofibroblasts. These two types of cell were then plated on slides. 8 dyn/cm² of shear stress was applied to fibroblasts for 6 h and myofibroblasts for 24 h, respectively. Using immunostaining we found that expressions of both alpha-SMA in fibroblasts and SM-MHC in myofibroblasts were significantly upregulated under shear by 2.3-fold and 2.2-fold, respectively, based on the increase of fluorescent intensity compared to static controls. These results indicate that shear stress can promote fibroblast differentiation into myofibroblast, and myofibroblast differentiation into SMC. In another experiment, SMCs, fibroblasts, and myofibroblasts were plated in Boyden chambers, and 13 dyn/cm² of shear was applied to the cells for 4 h. We found the migration of fibroblasts was enhanced by shear, whereas, the migration of both SMCs and myofibroblasts were suppressed. Taken together, we speculate that the interstitial flow shear stress might play an important role in phenotype modulation and migration of fibroblast and myofibroblast during neointima formation and vascular remodeling.