Effects of high-frequency repetitive transcranial magnetic stimulation on remyelination in a rat model of focal cerebral ischemia

Abstract

Objective To explore the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) on the motor function, proliferation and differentiation of oligodendrocyte precursor cells (OPC), and expression of oligodendrocyte transcription factor 1 (Olig1), myelin basic protein (MBP) and NG2 in the striatum of rats after focal cerebral ischemia. Methods Sixty-three adult male SPF Sprague-Dawley (SD) rats were randomly divided into model group, rTMS group, and sham group, with 21 rats in each group. Transient middle cerebral artery embolism (tMCAO) model was prepared by thread embolization in the model group and rTMS group. Subsequently, the model group recovered naturally without any intervention, while the rTMS group received high frequency rTMS treatment every 24 h for 10 d. Each group was further assigned into 7 rats at the time points of days 1, 3, and 10 postoperatively, and modified neurological severity score (mNSS) was used to evaluate the motor function of the rats. Then the brains of each group were taken out for further analyses. Immunohistochemical staining was performed to observe the expression of NG2 and MBP in the ischemic striatum to evaluate the proliferation of OPC and severity of myelin damage. Western blotting was adopted to detect the expression of Olig1, MBP, and NG2 in the ischemic striatum. Results rTMS treatment significantly reduced the mNSS of tMCAO rats, with lower score in the rTMS group than in the model group (P < 0.05); It also promoted the proliferation and differentiation of OPC in tMCAO rats, which presented as a higher level of NG2 in the rTMS group than in the model group on days 1, 3 and 10 postoperatively (P < 0.05), as well as a higher level of Olig1 on days 3 and 10 (P < 0.05). In addition, although MBP expression in the model group was consistently lower than that in the sham group (P < 0.05), the level was higher in the rTMS group than the model group on day 10 (P < 0.05), suggesting that rTMS also promoted the repair of myelin sheath after cerebral ischemia. Conclusion Application of high-frequency rTMS can promote OPC proliferation and myelin repair in the acute phase of post-ischemic stroke.

Keywords

• repetitive transcranial magnetic stimulation
• focal cerebral ischemia
• myelin
• oligodendrocyte precursor cells
• oligodendrocytes