The NLRP3 Inflammasome Regulates Orthodontic Tooth Movement.

OBJECTIVE: The NLRP3 inflammasome is a damage sensor driving pyroptotic cell death during orthodontic tooth movement (OTM). Recent studies have revealed impaired one-week OTM in mice lacking NLRP3. However, the relevance of NLRP3 during long-term OTM remains unknown. MATERIALS AND METHODS: OTM was analysed after 7, 14 and 21 days of force application in mice lacking NLRP3 (NLRP3-/-), wild-type (WT) male and female littermates. Micro-computed tomography (μCT) was used to assess molar movement and bone quality. Tartrate-resistant acid phosphatase (TRAP) staining was used to visualise osteoclastic activity. RESULTS: We show here that after 2 weeks of force application, OTM was delayed in mice lacking NLRP3 compared to WT mice. Interestingly, OTM regained speed in NLRP3-/- mice catching up with the WT controls at day 21. Independent of NLRP3 expression, OTM caused alveolar bone loss compared to the untreated contralateral side. NLRP3-/- mice showed a diminished number of TRAP-positive osteoclasts than WT male mice 14 and 21 days after OTM induction. CONCLUSION: The results of this study suggest that NLRP3 is relevant during the early but not later stages of OTM.