Orthodontic force alters Piezo/TRP channel expression in trigeminal ganglion and trigeminal mesencephalic nucleus neurons innervating the periodontal ligament.

Mechanical stimulation to periodontal ligament (PDL) by orthodontic force is received by the peripheral mechanoreceptors of trigeminal ganglion (TG) neurons and/or trigeminal mesencephalic nucleus (MesV) neurons, which are the primary sensory neurons. In this study, we examined changes in the expression of mechanosensitive plasma membrane proteins in TG and MesV neurons innervating the PDL labeled with cholera toxin B subunit (CTB) in response to orthodontic force as a sustained mechanical stimulation of molar tooth in nine-week-old Wistar rats. We also evaluated changes in body weight and food intake in non-orthodontic force-treated and orthodontic force-treated rats. In CTB-positive TG neurons innervating the PDL, we observed significantly higher expression levels of ion channels involved in mechanical sensing. Notably, in CTB-labeled MesV neurons, we observed that the expression level of Piezo2 channels was significantly higher in the group subjected to orthodontic force than in those not subjected to orthodontic force. Body weight did not change after 3 days of orthodontic force application, but food intake decreased. These results suggest that continuous mechanical stimulation by orthodontic force increases the mechanosensitive response in the PDL during proprioception via Piezo2-positive MesV neuron activation.