Mechano-Sensing and shear stress-shielding by endothelial primary cilia:structure,composition,and function

Primary cilium is an antenna-like and non-motile structure protruding from the apical surface of most mammalian cells including endothelial cells lining the inner side of all the blood vessels in our body.Although it has been over a century since primary cilia were discovered,the investigation about their mechano-sensing and other roles in maintaining normal functions of cardiovascular system has just started in recent years.This focused review aims to give an update about the current literature for the role of endothelial primary cilia in blood flow mechanosensing and shear stress-shielding.To do this,we first summarized the characteristic features of endothelial primary cilia in terms of structure,dimension,molecular composition,and mechanical properties(e.g.,bending rigidity),which are the dominant factors for their functions in mechano-sensing and transduction,as well as vascular protection from the blood flow-induced wall shear stress.We also described the experimental techniques and mathematical models for determining the dimension and mechanical properties of the primary cilium.Then we reviewed the molecular mechanisms underlying mechano-sensing and transduction by endothelial primary cilia and the mathematical model prediction for their roles in redistribution and reduction of wall shear stresses.Finally,we briefly discussed the common cardiovascular diseases,e.g.,atherosclerosis,hypertension,and aneurysm,due to defects and malfunction of endothelial primary cilia and suggested potential targets for therapeutic treatments.