IFT80 and TRPA1 cooperatively regulate bone formation by calcium signaling in response to mechanical stimuli

Intraflagellar transport 80 (IFT80) is vital for primary cilia which can sense and transduce mechanical signals. Mechanical stimuli expedite osteoblastic differentiation and bone formation in mesenchymal stem cells (MSCs). However, how IFT80 regulates mechanical transduction in MSCs remains unclear. To investigate the role of IFT80 in bone development and mechanical transduction, MSC-specific knock-out IFT80 (Prx1Cre; IFT80f/f) mice were generated. These mice exhibited significant skeletal abnormalities. The study further examined the effects of IFT80 deficiency on mechanical stimulation-induced osteoblastic differentiation and bone formation, as well as the underlying molecular mechanisms involving TRPA1 and calcium signaling pathways. In our study, Prx1Cre; IFT80f/f mice results in pronounced skeletal abnormalities including dwarfism, bone formation defect, malformations in the skull, limbs, and sternum, and abnormal joint structures. Furthermore, IFT80 deficiency in MSCs inhibits mechanical stimulation induced osteoblastic differentiation. Exercise training could not improve the bone formation in Prx1Cre; IFT80f/f mice. Mechanistically, IFT80 deficiency in MSCs downregulated the expression of transient receptor potential ankyrin 1 (TRPA1) and TRPA1-mediated Ca2+ influx, which further inhibited osteoblastic differentiation under mechanical stimulation by AKT and ERK signaling pathways. Finally, TRPA1 overexpression reversed impaired bone formation in Prx1Cre; IFT80f/f mice under exercise training. IFT80 and TRPA1 cooperatively regulate osteoblastic differentiation and bone formation in response to mechanical stimulation. These findings suggest that IFT80 and TRPA1 are critical for skeletal homeostasis and may serve as potential therapeutic targets for skeletal disorders.