Effects of unilateral nasal obstruction on mandibular condyle in mice of different ages: An exploration based on H-type angiogenesis coupling osteogenesis

Nasal obstruction leads to a hypoxia condition throughout the entire body. In this study, the unilateral nasal obstruction (UNO) mouse model was established by blocking the left nostril of mice. The aim of this study was to investigate the effects of UNO-induced hypoxia on mandibular condyle in juvenile (3-week-old), adolescent (6-week-old) and adult (12-week-old) male C57BL/6J mice from the perspective of H-type angiogenesis coupling osteogenesis. Firstly, UNO exerted a significant inhibitory effect on weight gain in mice of all ages. However, only in adolescent mice did UNO have an obvious detrimental effect on femoral bone mass accrual. Subsequently, micro-computed tomography (CT) analysis of mandibular condylar bone mass revealed that UNO significantly retarded condylar head volume gain but increased condylar head trabecular number (Tb.N) in juvenile and adolescent mice. Furthermore, UNO promoted the ratio of proliferative layer to cartilage layer in condylar cartilage and facilitated the chondrocyte-to-osteoblast transformation in juvenile and adolescent mice. Moreover, although UNO enhanced the positive expression of hypoxia-inducible factor (HIF)-1α in the condylar subchondral bone of mice in all ages, an increase in H-type vessels and Osterix⁺ cells was only detected in juvenile and adolescent mice. In summary, on the one hand, in terms of condylar morphology, UNO has a negative effect on condylar growth, hindering the increase in condylar head volume in juvenile and adolescent mice. However, on the other hand, in terms of condylar microstructure, UNO has a positive effect on condylar osteogenesis, promoting the increase of condylar Tb.N, chondrocyte-to-osteoblast transformation, HIF-1α expression, H-type angiogenesis and Osterix⁺ cells in juvenile and adolescent mice. Although the changes in condylar morphology and microstructure caused by UNO have not yet been fully elucidated, these findings improve our current understanding of the effects of UNO on condylar bone homeostasis.