BACKGROUND

Trans-sutural distraction osteogenesis (TSDO) involves the application of distraction force to facial sutures to stimulate osteogenesis. Gli1 cells in the cranial sutures play an important role in bone growth. However, whether Gli1 cells in facial sutures differentiate into bone under distraction force is unknown.

METHODS

4-week-old Gli1ER/Td and C57BL/6 mice were used to establish a TSDO model to explore osteogenesis of zygomaticomaxillary sutures. A Gli1 cell lineage tracing model was used to observe the distribution of Gli1 cells and explore the role of Gli1 cells in facial bone remodeling.

RESULTS

Distraction force promoted bone remodeling during TSDO. Fluorescence and two-photon scanning images revealed the distribution of Gli1 cells. Under distraction force, Gli1-lineage cells proliferated significantly and co-localized with Runx2 cells. Hedgehog signaling was upregulated in Gli1 cells. Inhibition of Hedgehog signaling suppresses the proliferation and osteogenesis of Gli1 cells induced by distraction force. Subsequently, the stem cell characteristics of Gli1 cells were identified. Cell-stretching experiments verified that mechanical force promoted the osteogenic differentiation of Gli1 cells through Hh signaling. Furthermore, immunofluorescence staining and RT-qPCR experiments demonstrated that the primary cilia in Gli1 cells exhibit Hedgehog-independent mechanosensitivity, which was required for the osteogenic differentiation induced by mechanical force.

CONCLUSIONS

Our study indicates that the primary cilia of Gli1 cells sense mechanical stimuli, mediate Hedgehog signaling activation, and promote the osteogenic differentiation of Gli1 cells in zygomaticomaxillary sutures.