Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive technique that uses electromagnetic fields to stimulate the brain. rTMS can restore an impaired central nervous system and promote proliferation of neural stem/progenitor cells (NSPCs), but optimal stimulus parameters and mechanisms underlying these effects remain elusive. The purpose of this study is to investigate the effect of different rTMS stimulus parameters on proliferation and apoptosis of spinal cord-derived NSPCs, the expression of brain-derived neurotrophic factor (BDNF) after rTMS, and the potentially underlying pathways. NSPCs were isolated from mice spinal cord and stimulated by different frequencies (1/10/20 Hz), intensities (0.87/1.24/1.58 T), and number of pulses (400/800/1,500/3,000) once a day for five consecutive days. NSPC proliferation was analyzed by measuring the neurosphere diameter and Brdu staining, apoptosis was detected by cell death enzyme-linked immunosorbent assay (ELISA) and flow cytometry, and NSPC viability was assessed by cell counting kit-8 assay. We found that specific parameters of frequency (1/10/20 Hz), intensity (1.24/1.58 T), and number of pulses (800/1,500/3,000) promote proliferation and apoptosis (p < 0.05 for all), but 20 Hz, 1.58 T, and 1,500 pulses achieved the optimal response for the NSPC viability. In addition, rTMS significantly promoted the expression of BDNF at the mRNA and protein level, while also increasing Akt phosphorylation (Thr308 and Ser473; p < 0.05). Overall, we identified the most appropriate rTMS parameters for further studies on NSPCs in vitro and in vivo. Furthermore, the effect of magnetic stimulation on NSPC proliferation might be correlated to BDNF/Akt signaling pathway.
Highlights
Repetitive transcranial magnetic stimulation is a widely used noninvasive technique that uses electromagnetic fields to stimulate the brain
We aimed to explore the effect of Repetitive transcranial magnetic stimulation (rTMS) at different intensity, frequency, and number of pulses on spinal cord-derived neural stem/progenitor cells (NSPCs) apoptosis and proliferation, shedding light on potential underlying mechanisms
Both p-Akt (Thr308) and p-Akt (Ser473) were significantly upregulated in the rTMS group compared to the control, while no significant differences were observed in total Akt expression (Figures 6F,G). These results indicated that rTMS stimulation promoted the expression of brain-derived neurotrophic factor (BDNF), which is associated with the phosphorylation level of Akt
Summary
Repetitive transcranial magnetic stimulation (rTMS) is a widely used noninvasive technique that uses electromagnetic fields to stimulate the brain. RTMS has a direct effect on the excitability of regions functionally connected with rTMS Regulates Neural Stem/Progenitor Cells cortical and subcortical structures. RTMS has been reported to treat many neurological diseases including traumatic brain injury, spinal cord injury (SCI), neurodegenerative disorders, schizophrenia, and substance addiction (Tazoe and Perez, 2015; Benussi et al, 2018; Shin et al, 2018). The therapeutic effect induced by rTMS might be associated to several processes, such as increased neural stem and progenitor cell growth and neuronal differentiation, release of neurotrophic factors (e.g., brain-derived neurotrophic factor, BDNF), and regulation of neuronal excitability and cerebral blood flow (Lee et al, 2015). Numerous techniques were explored to promote the proliferation of NSPCs, including rTMS, but the most appropriate parameters were not clear (Guo et al, 2014)
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