Primary cilia on endothelial cells : component of the shear stress sensor localized to athero-prone flow areas

Abstract

Blood-flow-induced shear stress plays an important role in cardiovascular development and disease. How endothelial cells sense shear stress remains to be elucidated. We postulated that the primary cilium is a component of the endothelial shear sensor. This luminal cell protrusion contains microtubules and is connected to the microtubular cytoskeleton. We identified cilia on endothelial cells of the embryonic heart in areas of low or oscillatory shear stress. This shear-related distribution is reminiscent of the distribution of atherosclerotic lesions in the adult arterial system, as lesions develop at sites of low or oscillating shear (athero-prone flow). Ciliated endothelial cells are exclusively present at these atherosclerotic predilection sites in adult mice. Athero-prone (oscillatory) but not athero-protective (steady or pulsatile) flow induces ciliation of cultured endothelial cells. Moreover, the endothelial shear response is dependent on the microtubular cytoskeleton and primary cilia sensitise the endothelium for shear. Taken together, these data demonstrate that primary cilia are induced by athero-prone flow and that ciliated cells are more sensitive to shear stress. We conclude that the endothelial biosensor for shear stress is the microtubular cytoskeleton and that the attached primary cilium functions as a signal amplifier in areas subjected to athero-prone flow.