Ann Rehabil Med.  2022 Oct;46(5):228-236. 10.5535/arm.22040.

Low-Frequency Repetitive Transcranial Magnetic Stimulation in the Early Subacute Phase of Stroke Enhances Angiogenic Mechanisms in Rats

• Lee Y
• Oh BM
• Park SH
• Han TR

• KMID: 2535740
• DOI: http://doi.org/10.5535/arm.22040

Abstract

Objective
To characterize the repetitive transcranial magnetic stimulation (rTMS) induced changes in angiogenic mechanisms across different brain regions.
Methods
Seventy-nine adult male Sprague-Dawley rats were subjected to a middle cerebral artery occlusion (day 0) and then treated with 1-Hz, 20-Hz, or sham stimulation of their lesioned hemispheres for 2 weeks. The stimulation intensity was set to 100% of the motor threshold. The neurological function was assessed on days 3, 10, and 17. The infarct volume and angiogenesis were measured by histology, immunohistochemistry, Western blot, and real-time polymerase chain reaction (PCR) assays. Brain tissue was harvested from the ischemic core (IC), ischemic border zone (BZ), and contralateral homologous cortex (CH).
Results
Optical density of angiopoietin1 and synaptophysin in the IC was significantly greater in the low-frequency group than in the sham group (p=0.03 and p=0.03, respectively). The 1-Hz rTMS significantly increased the level of Akt phosphorylation in the BZ (p<0.05 vs. 20 Hz). Endothelial nitric oxide synthase phosphorylation was increased in the IC (p<0.05 vs. 20 Hz), BZ (p<0.05 vs. 20 Hz), and CH (p<0.05 vs. 20 Hz and p<0.05 vs. sham). Real-time PCR demonstrated that low-frequency stimulation significantly increased the transcriptional activity of the TIE2 gene in the IC (p<0.05).
Conclusion
Low-frequency rTMS of the ipsilesional hemisphere in the early subacute phase of stroke promotes the expression of angiogenic factors and related genes in the brain, particularly in the injured area.

Keyword

Transcranial magnetic stimulation; Recovery of function; Stroke; Angiogenesis modulating agents; Neuronal plasticity

Figure

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  Fig. 1 Experimental design. MCAO, middle cerebral artery occlusion; rTMS, repetitive transcranial magnetic stimulation; PCR, polymerase chain reaction.

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  Fig. 2 Neurological function tests. There were no significant differences in (A) Garcia’s motor behavior score, (B) Rotarod test, and (C) modified foot fault test across the treatment groups at days 3, 10, or 17. Error bars represent the standard error of the mean.

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  Fig. 3 Estimation of the infarct volume. Representative hematoxylin- and eosin-stained coronal section of the brain tissue are provided for (A) the sham, (B) 20 Hz, and (C) 1 Hz groups. The calculated volumes were similar across all three groups.

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  Fig. 4 Optical densities of (A) angiopoietin 1 and (B) synaptophysin in the ischemic core, border zone, and contralateral homologous cortices. *p<0.05.

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  Fig. 5 Results of Western blotting on phospho-Akt and phospho-eNOS. (A) Akt phosphorylation was significantly increased in the border zone in the low-frequency stimulation group compared to the high-frequency stimulation group. (B) Note the enhanced eNOS phosphorylation in the stimulated cortex with the low-frequency stimulation compared to the high-frequency stimulation (left). Interestingly, the Western blot demonstrates significantly higher levels of eNOS phosphorylation in the low-frequency group than in the sham and high-frequency stimulation groups in the contralateral cortex (right). *p<0.01.

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  Fig. 6 Expression of VEGFA, ANGPT1, and TEK in the ischemic core. Expression of TEK was significantly increased in the low-frequency stimulation group than that in the sham stimulation group. *p<0.05.

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