LIPUS accelerates bone regeneration via HDAC6-mediated ciliogenesis.

Delayed fracture union and nonunion are common complications of fracture encountered, while Low-intensity pulsed ultrasound (LIPUS) can stimulate bone regeneration. Still, the underlying mechanism of LIPUS on bone regeneration has been poorly understood, which resulted in varied outcomes in the clinic. Therefore, figuring out the mechanism of LIPUS on bone regeneration can lay the foundation for better use of LIPUS in clinical bone regenerative therapies. In this study, we created transgenic mice to reveal the relationship between the periosteal cells' fate and the number of ciliated cells under the LIPUS stimulation. In vitro, we isolated the periosteal cell and aim to figure out the relationship between LIPUS and HDAC6-mediated ciliogenesis and find out a potential target for LIPUS-based bone regeneration strategies. The results showed that LIPUS promoted femoral bone defect regeneration and enhanced osteogenic differentiation of Prrx1+ cells. However, these pro-effects were significantly weakened when the Prrx1+ cell's primary cilia were knocked down. Besides, LIPUS stimulated the formation of Prrx1+ cells' primary cilia in the bone defect microenvironment. In vitro, the results supported that LIPUS enhanced the osteogenic differentiation of Prrx1+ cells through HDAC6-mediated ciliogenesis. In conclusion, λ LIPUS could promote the osteogenic differentiation of Prrx1+ cells to stimulate bone regeneration and inhibit the expression of HDAC6 to increase the prevalence of primary cilia in Prrx1+ cells. LIPUS could enhance the osteogenic differentiation of Prrx1+ cells mainly through HDAC6-mediated ciliogenesis.