Bilateral intermittent nasal obstruction in adolescent rats leads to the growth defects of mandibular condyle  Publication date: October 2019 Source: Archives of Oral Biology, Volume 106 Author(s): Xiaoling Wang, Huijun Sun, Yanfei Zhu, Yanmei Tang, Xiaochen Xue, Ping Nie, Min Zhu, Bing Wang Abstract Objective This study aimed to evaluate the effects of nasal obstruction on mandibular growth, especially condyle, in adolescent rats and explore the possible mechanism with a focus on mesenchymal stem cells (MSCs) from condylar tissues. Design 4-week-old male Sprague–Dawley rats were randomly divided into bilateral intermittent nasal obstruction (i.e. mouth-breathing, MB) and nasal-breathing (NB) groups. Self-made plugs were used to obstruct the nasal cavity in the MB group for 4 weeks, from 8:00 a.m. to 4:00 p.m. every day. The body weights were recorded. Three-dimensional computed tomography (3D-CT) scanning of the craniomaxillary region was performed after 2 and 4 weeks of nasal obstruction. Other rats were sacrificed, and MSCs were isolated from condylar tissues and cultured in vitro for examining the cell proliferation and expression of chondrogenic marker genes. Results Significant decreases in body weight were observed in the MB group compared with the NB group during 4 weeks of nasal obstruction. All mandibular parameters in the sagittal, vertical, and transverse dimensions (except bi-condylar width) measured via 3D-CT were significantly smaller in the MB group. No significant difference was found in the proliferative ability of cultured MSCs derived from condylar tissues between the two groups. However, the expression of chondrogenic marker genes Acan, Col2a1 and Sox9 was significantly lower in the MB group-derived MSCs, using Cell Counting Kit-8 and quantitative polymerase chain reaction. Conclusion The findings suggested that mouth breathing forced by nasal obstruction lead to developmental defects in the mandibular condyle, which might be related to the reduced cartilage differentiation of condylar MSCs.