A three-dimensional simulation of the dynamics of primary cilia in an oscillating flow

Abstract

Primary cilia at mammalian cells play a crucial role in mechanosensing of biological flows. Understanding the fluid-cilia interaction not only help to interpret the role of primary cilia as a flow sensor but also could shed light on the design of bio-inspired flow sensors. This study thus investigates the dynamics of primary cilia in an oscillating viscous flow via a three-dimensional simulation. In our simulations, a two-way fluid-structure interaction is considered using the immersed boundary-lattice Boltzmann method. To reproduce the experimentally observed ciliary basal rotations, the primary cilium is modelled as a slender filament whose basal end is connected to a nonlinear rotational spring. For the scenario considered, the primary cilium is observed to do an in-plane flapping motion which is symmetrical in term of the superimposed cilium profiles. For a cilium undergoes such a flapping motion, the flow-induced curvature (or tensile stress) at its lower part is found to synchronize better with the applied pressure gradient signal. Therefore, the lower part of primary cilia may be more responsible for detecting the real-time variations of the flow information. Our simulation results also suggest that the location of the maximal tensile stress is propagatable rather than staying at a fixed site, e.g., the base point, possibly due to the asynchronous deflection occurs at the cilium's different parts. The presence of primary cilia is also found to reduce the spatial-averaged wall shear stress (WSS) level and alter the oscillation characteristic of the WSS field by making the WSS less oscillatory in some regions.