Early effects of α7nAChR regulation on maxillary expansion in mice : A study on osteogenesis and inflammatory factors.

Purpose: We aimed to investigate early effects of regulating alpha‑7 nicotinic acetylcholine receptor (α7nAChR) agonists and antagonists on maxillary expansion in mice.

Methods: We allocated 36 six-week-old male C57BL/6J mice into three group: 1) expansion alone, 2) expansion plus the α7nAChR-specific agonist 3‑(2,4-dimethoxybenzylidene)-anabaseine dihydrochloride (GTS-21), and 3) expansion plus alpha-bungarotoxin (α-BTX), a competitive antagonist of α7nAChR. The groups were daily injected with saline, GTS-21 (4 mg/kg/day) or α‑BTX (1 mg/kg/day), respectively, from days 0-7. In addition, a mouse model of maxillary expansion was established. Masson's trichrome staining was used to observe morphological changes and immunohistochemistry was performed to analyze α7nAChR, interleukin (IL)-1β, IL‑6, tumor necrosis factor (TNF)-α, runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN) expression in the midpalatal suture. Microcomputed tomography was used to measure midpalatal suture and palatal basal bone widths. We assessed the normal distribution of our data using the Kolmogorov-Smirnoff test and evaluated the homogeneity of variance by Levene's test, followed by a two-way ANOVA and Bonferroni tests at a significance level of P < 0.05.

Results: In the GTS-21+expansion group, osteogenesis was more active in the middle palatine suture. New bone was calcified and deposited in the suture and we observed decreased IL-1β, IL‑6, and TNF‑α expression (P < 0.05). In the α‑BTX+expansion group, we observed increased proinflammatory cytokine and decreased RUNX2 and OCN expression and increased midpalatal suture and palatal basal bone widths (P < 0.05).

Conclusion: Using α7nAChR agonists and antagonists to regulate the cholinergic anti-inflammatory pathway, the secretion of inflammatory factors and osteoblast markers during maxillary expansion were altered, indicating the potential for clinical modulation of maxillary palatal suture expansion.