Effect of low intensity pulsed ultrasound on expression of TGF-β1 and Smads during dentin injury and repair / 中南大学学报(医学版)

ABSTRACT

Objective:To explore the effect of low intensity pulsed ultrasound (LIPUS) on TGF-β1/Smad 2,3 signal pathway during the dentin injury and repair.Methods:Among 25 Sprague-Dawley rats,5 rats served as a blank control group without treatment.The remaining 20 rats received modified caries preparation inbilateral maxillary first molars to establish a model of dentin-pulp injury and repair.The right maxillary first molars served as a LIPUS group,which received LIPUS irradiation (frequency1.5 MHz,pulse width200 μs,pulse repetition frequency1 kHz,spatial averaged temporal averaged intensity30 mW/cm2,20 min/d),and the left maxillary first molars served as a cavity-prepared group,which received fake LIPUS irradiation.The rats were sacrificed at 1,3,5,7 and 14 days after LIPUS irradiation.Immunohistochemical staining and Image-pro plus 6.0 were applied to detect the expression and distribution of transforming growth factor-beta1 (TGF-β1) and small mothers against decapentaplegic 2/3(Smad 2 and Smad 3).Results:Immunohistochemical staining showed that the expression of TGF-β1 and Smad 2,3were low innormal pulp,but they were increased in different degree after dentin injury.The result of image analysis showed that the expression of TGF-β1 in the cavity-prepared group gradually increased at the first day and peaked at day 5,and then it returned to normal level at day 14.However,the expression of TGF-β 1 in the LIPUS group were significantly higher than that in the cavity-prepared group at day 3 and 5 (bothP＜0.05).The expressions of Smad 2,3 in both the LIPUS group and the cavity-prepared group were consistently increased all the way, but the expressions in the LIPUS group were higher compared with that in the cavity-prepared group (P＜0.05).Conclusion:The TGF-β1/Smad 2,3 signal pathway can be activated during the dentin injury and repair.LIPUS can up-regulate the expression of TGF-β1 and Smad 2,3 in the early period,which may take part in the dentin-pulp complex injury and repair process.