Mechanosensing by Gli1+ cells contributes to the orthodontic force-induced bone remodelling

Objectives: Gli1⁺ cells have received extensive attention in tissue homeostasis and injury mobilization. The aim of this study was to investigate whether Gli1⁺ cells respond to force and contribute to bone remodelling.

Materials and methods: We established orthodontic tooth movement (OTM) model to assess the bone response for mechanical force. The transgenic mice were utilized to label and inhibit Gli1⁺ cells, respectively. Additionally, mice that conditional ablate Yes-associated protein (YAP) in Gli1⁺ cells were applied in the present study. The tooth movement and bone remodelling were analysed.

Results: We first found Gli1⁺ cells expressed in periodontal ligament (PDL). They were proliferated and differentiated into osteoblastic cells under tensile force. Next, both pharmacological and genetic Gli1 inhibition models were utilized to confirm that inhibition of Gli1⁺ cells led to arrest of bone remodelling. Furthermore, immunofluorescence staining identified classical mechanotransduction factor YAP expressed in Gli1⁺ cells and decreased after suppression of Gli1⁺ cells. Additionally, conditional ablation of YAP gene in Gli1⁺ cells inhibited the bone remodelling as well, suggesting Gli1⁺ cells are force-responsive cells.

Conclusions: Our findings highlighted that Gli1⁺ cells in PDL directly respond to orthodontic force and further mediate bone remodelling, thus providing novel functional evidence in the mechanism of bone remodelling and first uncovering the mechanical responsive property of Gli1⁺ cells.