Reveal Anisotropic Elasticity of Endothelium Under Fluidic Shear Stress

Endothelium lining interior surface of blood vessels experiences various physical stimulations in vivo . Its physical properties, especially elasticity, play important roles in regulating physiological functions of vascular systems. In this paper, an integrated approach is developed to characterize anisotropic elasticity of the endothelium under physiological-level fluidic shear stress. A pressure sensor-embedded microfluidic device is developed to provide fluidic shear stress on the perfusion-cultured endothelium, and to measure transverse in-plane elasticities in the directions parallel and perpendicular to the flow direction. Biological atomic force microscopy (Bio-AFM) is further exploited to measure vertical elasticity of the endothelium in its out-of-plane direction. The results show that the transverse elasticity of the endothelium in the direction parallel to the perfusion culture flow direction is more than twice as that in the direction perpendicular to the flow direction. Moreover, the transverse elasticities of the endothelium are estimated to be approximately 200 times larger than the vertical one. The results indicate effects of fluidic shear stress on the transverse elasticity anisotropy of the endothelium, and difference between the elasticities in transverse and vertical directions. The quantitative measurement of the endothelium anisotropic elasticity in different directions at the tissue level under the shear stress provides biologists insightful information for the advanced vascular system studies from biophysical viewpoints.