Comparison of Condylar Remodelling After Mandibular Advancement in Mice With Normal Nasal Breathing and Unilateral Nasal Obstruction.

Abstract

Background: Normal nasal breathing is crucial for the harmonious growth of craniofacial bones, whereas obstructed nasal breathing not only hampers craniofacial growth but also induces chronic systemic hypoxia. This study compared the effects of mandibular advancement (MA) on condylar remodelling under normal nasal breathing (NNB) and unilateral nasal obstruction (UNO).

Methods: Forty 12-week-old male C57BL/6J mice were randomly divided into NNB, UNO, NNB + MA and UNO + MA groups. The UNO model was established by blocking the left nostril of the mice. The NNB mice underwent a sham operation, in which a plug was inserted and immediately removed. The MA model was established by periodically trimming the mandibular incisors of the mice. Femurs and mandibles were collected on day 31 for morphological, bone mass, histological, immunohistochemical and immunofluorescence analyses.

Results: Compared with the NNB + MA group, the mice in the UNO + MA group had no statistically significant differences in body weight, femoral length, femoral bone density, mandibular length, condylar length, mandibular angle and condylar bone density. However, the UNO + MA group exhibited an increase in condylar bone formation volume and thickening of the condylar cartilage layer, along with elevated expression of hypoxia-inducible factor (HIF)-1α, H-type vessels and Osterix⁺ cells within the subchondral bone of the condyle.

Conclusions: The increase in condylar bone formation in the UNO + MA group was significantly higher than that in the NNB + MA group. Mechanistically, the MA under UNO condition thickens the condylar cartilage layer and facilitates the upregulation of HIF-1α expression in the condylar subchondral bone, thereby promoting the coupling between H-type angiogenesis and osteogenesis.