Possible alternative treatment for mandibular asymmetry by local unilateral IGF-1 injection into the mandibular condylar cavity: Experimental study in mice.

INTRODUCTION: The purpose of this study was to investigate whether a local unilateral IGF-1 injection into the mandibular condylar cavity can induce unilateral endochondral mandibular growth without any systemic adverse effects.

METHODS: Seventy-five 3-week-old male Jcl:ICR mice were used in this study. The mice were divided into 2 groups: control group (n = 22) and IGF-1 group (n = 53). In the IGF-1 group, human IGF-1 was injected into the right mandibular condylar cavity, and phosphate-buffered saline solution was injected into the left cavity, 3 times per week for 10 weeks.

RESULTS: There was no significant difference in body weight, serum human IGF-1 concentration, and soft tissue thickness of the cheeks including the masseter muscles between the 2 groups. Unilateral IGF-1 injection induced a lateral shift of the mandible to the contralateral side, and microcomputed tomogtraphy analysis showed that unilateral IGF-1 injection induced endochondral growth in the condyle. Col2, Ihh, and Runx2 were extensively upregulated by the local unilateral IGF-1 injection in real-time reverse transcription polymerase chain reaction analysis. Proliferation marker KI67, IGF-1 signaling molecule AKT1, and chondrogenic differentiation marker Col2 were strongly expressed in the IGF-1 injected condyle by immunohistochemistry. Vital labeling showed that the distance between the labels was increased in the IGF-1 injection group compared with that of the control group.

CONCLUSIONS: The results verified in this study indicated that local unilateral IGF-1 injection into the mandibular condylar cavity successfully induced unilateral endochondral mandibular growth in mice without any systemic adverse effects. Thus, local unilateral IGF-1 injection into the mandibular condylar cavity could be a useful alternative for mandibular asymmetry therapy during the growth period. However, additional experimental and clinical studies will be necessary to prove the real effect of this new therapy.