Objective-Recent studies have illustrated that mesenchymal stem cells possess the potential to differentiate along an endothelial lineage, but the effect of shear on mesenchymal differentiation is unknown. Thus, we developed an in vitro shear stress system to examine the relationship between shear stress and the endothelial differentiation of a murine embryonic mesenchymal progenitor cell line, C3H/10T1/2. Methods and Results-The parallel plate system of fluid shear stress was used. Shear stress significantly induced expression of mature endothelial cell-specific markers in CH3H/10T1/2 cells such as CD31, von Willebrand factor, and vascular endothelial-cadherin at both the mRNA and protein levels with real-time polymerase chain reaction and immunofluorescence analyses, respectively. In addition, shear-induced augmentation of functional markers of the mature endothelial phenotype such as uptake of acetylated low-density lipoproteins and formation of capillary-like structures on Matrigel. Furthermore, shear stress significantly upregulated angiogenic growth factors while downregulating growth factors associated with smooth muscle cell differentiation. T he blood vessel wall is inherently subjected to and affected by the pulsatile hemodynamic stimulus of blood flow within the vascular lumen, and biomechanical forces intrinsically present as a result of this hemodynamic flow are believed to play an important role in vascular development, remodeling, and lesion formation. In particular, cells lining the vascular lumen are constantly subjected to shear stress, a frictional force at the apical endothelial surface exerted by blood flow. 1,2 Shear stress has been recognized as an important modulator of endothelial phenotype, morphology, gene expression, and, especially, differentiation. 3,4 See page 1761
Conclusions-ThisThe ability to influence or control endothelial cell differentiation would have implications for vasculogenesis (neovascularization), understanding the pathogenic physiology behind atherosclerotic lesion formation, use in vascular healing or repair, and use in tissue engineering applications; thus, recent studies have demonstrated the utility of shear stress in provoking endothelial progenitor cell (EPC) differentiation. 4,5 However, these studies have generally used a fairly heterogeneous starting precursor population. Furthermore, the overall small number of EPCs in circulation and the need for ex vivo expansion before use suggests that the EPC may not be the best progenitor for functional application. 6 Recent studies have illustrated that mesenchymal stem cells (MSCs) also possess the potential to differentiate along an endothelial lineage. 7,8 For example, Oswald et al demonstrated endothelial differentiation when MSCs were cultivated in 2% FCS and 50 ng/mL vascular endothelial growth factor (VEGF). 7 Additionally, other studies have revealed the contribution of MSCs to the formation of new vessels and improvements in cardiac function. 9,10 Thus, MSCs may hold the potential to differentiate along end...