Objective: To elucidate the regulatory bio-mechanism of estrogen and local stress on the bone remodeling activities in vivo.
Methods: A Wistar rat experimental model was established to apply orthodontic activation during different stages of estrous cycle. In situ hybridization was used to detect the variation of the insulin-like growth factors (IGF) mRNA expression in the periodontal tissues. The data of each group was analyzed with SPSS 11.0 software package for Student-Newman-Keuls (S-N-K) test and one way ANOVA test.
Results: Both IGF-I mRNA and IGF-II mRNA level expressed in the periodontal tissues were increased by orthodontic activation during various stages of the estrous cycle. But a similar pattern emerged that the IGF-I mRNA level was the lowest in the estrous stage, whereas its level was the highest in the proestrus stage (P < 0.05). No rhythm of IGF-II mRNA expression found during the estrous cycle.
Conclusion: It was concluded that local mechanical stimulation directly enhanced the IGF expression. In contrast to the IGF-II, IGF-I was also influenced by the sex hormone rhythm during the estrous cycle.