The role of primary cilia in mechanical transmission of osteocyte based on a 3D finite element model

The primary cilium, as a mechanical receptor of osteocytes, participates in the regulation of osteocyte mechanosensitivity. However, how the length of osteocyte primary cilia changes with fluid shear stress (FSS) are unclear, and how the mechanical transmission within osteocytes altered by primary cilia is not well understood yet. Therefore, the ciliary length changes of osteocyte under 15 ​dyn/cm2 of FSS were experimentally detected, and then 3D finite element models of osteocyte primary cilia containing the basal body and axoneme were built. The results showed that (1) The ciliary length of the CON group, FSS 1h, and FSS 6h were 3.71 ​± ​1.34 ​μm, 3.79 ​± ​1.04 ​μm, and 1.24 ​± ​0.73 ​μm respectively, indicating the different durations of FSS might lead to the adaptive changes of cilium length. The calculations showed (2) when the ciliary length became shorter with the ciliary angle stayed the same, the deformation and stress of the cell membrane and membrane skeleton was increased. However, the deformation and stress of the cilia membrane, basal body, the rotation angles of basal body were decreased, and those of cytoplasm, cytoskeleton, actin cortex and nucleus were also decreased; (3) With the decrease of the ciliary angle, the deformation and stress of the cilia membrane, basal body, as well as the rotation angles of basal body were increased. Those of the cytoplasm, cytoskeleton, actin cortex, and nucleus were also increased except the cell membrane and membrane skeleton. The calculation results suggested the length and angle of the primary cilia, the deformation and stress of intracellular structures in osteocyte were altered with ciliary basal body, indicated the connection between the basal body and cytoskeleton may be a key factor that affected the mechanical transport in osteocytes across the cell membrane. This finally promoted the adaptive change of ciliary length under FSS.