Insulin-mediated ciliary remodeling in the choroid plexus epithelium.

The choroid plexus (ChP) epithelium plays a crucial role in cerebrospinal fluid production and brain homeostasis. ChP is mainly composed of multiciliated epithelial cells that exhibit a noncanonical ciliary organization whose function is still debated. Insulin signaling is known to be important for central nervous system function, but its role in ChP function and ciliary organization has not been elucidated yet. To investigate how prolonged insulin exposure modulates ChP cells, we treated primary murine choroid plexus epithelial cells (pCPECs) with insulin for up to six days and used a combination of immunohistochemistry, RT-qPCR, RNA fluorescence in situ hybridization, single cell analysis and Western Blot to explore underlying molecular mechanisms. We demonstrated that prolonged insulin treatment significantly increased the percentage of multiciliated clustered pCPECs and their axoneme length. Prolonged insulin treatment selectively induced translocation of IFT20, a key component of the intraflagellar transport system, to the ciliary axoneme by increasing the cytoplasmatic surface area covered by IFT20. To note, the expression of insulin receptors (IRs) in ex vivo ChP epithelial cells started during late embryogenesis and localized predominantly to the apical membrane, but not in the cilium. Our study suggests that insulin signaling may promote ciliary remodeling in choroid plexus epithelial cells, most likely by modulating intraflagellar transport dynamics involving IFT20. These findings reveal a novel role of insulin signaling in ChP cilia organization and function, with potential implications for cerebrospinal fluid (CSF) regulation and neurodevelopmental processes.