The mechanism by which sinusoidal electromagnetic irradiation inhibits heterotopic ossification / 中华物理医学与康复杂志

ABSTRACT

Objective:To observe electromagnetic field irradiation′s ability to inhibit heterotopic ossification (HO) and explore the mechanisms involved.Methods:A total of 72 male Sprague-Dawley rats were randomly divided into a control group, a model group and an observation group, each of 24. The rats in the model and observation groups were made to model HO by clamping and cutting the Achilles tendon, while among those in the control group the Achilles tendon was only exposed without clamping and cutting. The rats in the observation group were exposed to a 1mT electromagnetic field alternating sinusoidally at 50Hz (SEMF) twice a day for 2h each time. At 3 days, 14 days, 1 month and 3 months after the operation, Achilles tendon tissue was resected from 6 rats in each group for gross and histological examination and immunohistochemical staining. The protein content and gene expression were detected using western blotting or reverse transcription polymerase chain reaction. X-ray examination was performed at 1 and 3 months after the operation to observe any HO.Results:No significant changes were observed in the control group after the operation. Compared with the model group, HO in the observation group was significantly inhibited. The average expression of the MMP-9 gene in the model and observation groups was significantly higher than in the control group, and it increased with time. The average tissue metalloproteinase-1 (TIMP-1) gene expression was significantly lower, and it decreased with time. Compared with the model group, the average expression of MMP-9 in the observation group was significantly less, while that of TIMP-1 was significantly greater. Compared with the model group, there was also a significant increase in the expression of decapentaplegic homolog 7 (Smad7) protein and a significant decrease in the expression of phosporylated Smad3 protein at each time point.Conclusion:Applying 50Hz, 1mT SEMF has a definite effect in inhibiting HO, at least in rats. It may be related to promoting the expression of Smad7 and inhibiting the phosphorylation of Smad3, thus inhibiting the TGF-β/Smad signal transduction pathway and promoting the restoration of a dynamic balance of MMP-9 with TIMP-1.