Neuroprotection of Low-Frequency Repetitive Transcranial Magnetic Stimulation after Ischemic Stroke in Rats

High-frequency rTMS alleviates cognitive impairment and regulates synaptic plasticity in the hippocampus of rats with cerebral ischemia

Poststroke cognitive impairment (PSCI) is a common complication of stroke, but effective treatments are currently lacking. Repetitive transcranial magnetic stimulation (rTMS) is gradually being applied to treat PSCI, but there is limited evidence of its efficacy. To determine rTMS effects on PSCI, we constructed a transient middle cerebral artery occlusion (tMCAO) rat model. Rats were then grouped by random digital table method: the sham group (n = 10), tMCAO group (n = 10) and rTMS group (n = 10). The shuttle box and Morris water maze (MWM) tests were conducted to detect the cognitive functions of the rats. In addition, synaptic density and synaptic ultrastructural parameters, including the active zone length, synaptic cleft width, and postsynaptic density (PSD) thickness, were quantified and analyzed using an electron microscope. What's more, synaptic associated proteins, including PSD95, SYN, and BDNF were detected by western blot. According to the shuttle box and MWM tests, rTMS improved tMCAO rats' cognitive functions, including spatial learning and memory and decision-making abilities. Electron microscopy revealed that rTMS significantly increased the synaptic density, synaptic active zone length and PSD thickness and decreased the synaptic cleft width. The western blot results showed that the expression of PSD95, SYN, and BDNF was markedly increased after rTMS stimulation. Based on these results, we propose that 20 Hz rTMS can significantly alleviate cognitive impairment after stroke. The underlying mechanism might be modulating the synaptic plasticity and up-regulating the expression PSD95, SYN, and BDNF in the hippocampus.

Effect of high-frequency repetitive transcranial magnetic stimulation on swallowing function and pneumonia in poststroke dysphagia in rats

BACKGROUND

Post-stroke dysphagia (PSD) is a common symptom of stroke. Clinical complications of PSD include malnutrition and pneumonia. Clinical studies have shown that high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) can improve the swallowing function in stroke patients. However, few studies have elucidated the underlying molecular mechanisms.

METHODS

A PSD rat model was established using transient middle cerebral artery occlusion (tMCAO). Rats were randomly divided into sham-operated groups, PSD groups, PSD + sham-rTMS groups, PSD + 5 Hz-rTMS groups, PSD + 10 Hz-rTMS groups and PSD + 20 Hz-rTMS groups. Rats were weighed and videofluoroscopic swallowing studies were conducted. Pulmonary inflammation, levels of substance P (SP) and calcitonin gene-related peptide (CGRP) in the serum, lung, and nucleus tractus solitarius (NTS), brain-derived neurotrophic factor (BDNF) and 5-hydroxytryptamine (5HT) in NTS were evaluated.

RESULTS

Rats in the PSD group experienced weight loss, reduced bolus area and pharyngeal bolus speed, and increased pharyngeal transit time (PTT) and inter-swallow interval (ISI) on day 7 and day 14 after operation. Moreover, PSD rats showed pulmonary inflammation, reduced levels of SP in the lung and serum, increased levels of CGRP in the lung and NTS, reduced levels of BDNF and 5HT in the NTS. There was no significant difference between the PSD group and the PSD + sham-rTMS group in the results of weight and VFSS. Comparing with the PSD group, there significant increases in the bolus area, decreases in PTT of rats following 5 Hz rTMS intervention. HF-rTMS at 10 Hz significantly increased the weight, bolus area, pharyngeal bolus speed and decreased the PTT and ISI of rats. There were also significant increases in the bolus area (p < 0.01) and pharyngeal bolus speed, decreases in PTT and ISI of rats following 20 Hz rTMS intervention. Furthermore, compared with the PSD + 5 Hz-rTMS group, there were significant increases in the bolus area and pharyngeal bolus speed, decreases in ISI in the swallowing function of rats in the PSD + 10 Hz-rTMS group. Besides, compared with the PSD + 5 Hz-rTMS group, there were significant decreases in ISI in the swallowing function of rats in the PSD + 20 Hz-rTMS group. HF-rTMS at 10 Hz alleviated pulmonary inflammation, increased the levels of SP in the lung, serum, and NTS, CGRP in the serum and NTS, 5HT in the NTS of PSD rats.

CONCLUSION

Compared with 5 Hz and 20 Hz rTMS, 10 Hz rTMS more effectively improved the swallowing function of rats with PSD. HF-rTMS at 10 Hz improved the swallowing function and alleviated pneumonia in PSD rats. The mechanism may be related to increased levels of SP in the lung, serum and NTS, levels of CGRP in the serum and NTS, 5HT in the NTS after HF-rTMS treatment.

TsMS combined with EA promotes functional recovery and axonal regeneration via mediating the miR-539-5p/Sema3A/PlexinA1 signalling axis in sciatic nerve-injured rats

Enhancing axonal regeneration is one of the most important processes in treating nerve injuries. Both magnetic and electrical stimulation have the effect of promoting nerve axon regeneration. But few study has investigated the effects of trans-spinal magnetic stimulation (TsMS) combined with electroacupuncture (EA) on nerve regeneration in rats with sciatic nerve injury. In this study, we compared the improvement of neurological function in rats with sciatic nerve crush injuries after 4 weeks of different interventions (EA, TsMS, or TsMS combined with EA). We further explored the morphological and molecular biological alterations following sciatic nerve injury by HE, Masson, RT-PCR, western blotting, immunofluorescence staining and small RNA transcriptome sequencing. The results showed that TsMS combined with EA treatment significantly promoted axonal regeneration, increased the survival rate of neurons, and suppressed denervation atrophy of the gastrocnemius muscle. Subsequent experiments suggested that the combination treatment may play an active role by mediating the miR-539-5p/Sema3A/PlexinA1 signaling axis.

A translational roadmap for transcranial magnetic and direct current stimulation in stroke rehabilitation: Consensus-based core recommendations from the third stroke recovery and rehabilitation roundtable

BACKGROUND AND AIMS

The purpose of this Third Stroke Recovery and Rehabilitation Roundtable (SRRR3) was to develop consensus recommendations to address outstanding barriers for the translation of preclinical and clinical research using the non-invasive brain stimulation (NIBS) techniques Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) and provide a roadmap for the integration of these techniques into clinical practice.

METHODS

International NIBS and stroke recovery experts (N = 18) contributed to the consensus process. Using a nominal group technique, recommendations were reached via a five-stage process, involving a thematic survey, two priority ranking surveys, a literature review and an in-person meeting.

RESULTS AND CONCLUSIONS

Results of our consensus process yielded five key evidence-based and feasibility barriers for the translation of preclinical and clinical NIBS research, which were formulated into five core consensus recommendations. Recommendations highlight an urgent need for (1) increased understanding of NIBS mechanisms, (2) improved methodological rigor in both preclinical and clinical NIBS studies, (3) standardization of outcome measures, (4) increased clinical relevance in preclinical animal models, and (5) greater optimization and individualization of NIBS protocols. To facilitate the implementation of these recommendations, the expert panel developed a new SRRR3 Unified NIBS Research Checklist. These recommendations represent a translational pathway for the use of NIBS in stroke rehabilitation research and practice.

A translational roadmap for transcranial magnetic and direct current stimulation in stroke rehabilitation: Consensus-based core recommendations from the third stroke recovery and rehabilitation roundtable

BACKGROUND AND AIMS

The purpose of this Third Stroke Recovery and Rehabilitation Roundtable (SRRR3) was to develop consensus recommendations to address outstanding barriers for the translation of preclinical and clinical research using the non-invasive brain stimulation (NIBS) techniques Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) and provide a roadmap for the integration of these techniques into clinical practice.

METHODS

International NIBS and stroke recovery experts (N = 18) contributed to the consensus process. Using a nominal group technique, recommendations were reached via a five-stage process, involving a thematic survey, two priority ranking surveys, a literature review and an in-person meeting.

RESULTS AND CONCLUSIONS

Results of our consensus process yielded five key evidence-based and feasibility barriers for the translation of preclinical and clinical NIBS research, which were formulated into five core consensus recommendations. Recommendations highlight an urgent need for (1) increased understanding of NIBS mechanisms, (2) improved methodological rigor in both preclinical and clinical NIBS studies, (3) standardization of outcome measures, (4) increased clinical relevance in preclinical animal models, and (5) greater optimization and individualization of NIBS protocols. To facilitate the implementation of these recommendations, the expert panel developed a new SRRR3 Unified NIBS Research Checklist. These recommendations represent a translational pathway for the use of NIBS in stroke rehabilitation research and practice.

Early Intervention with Electrical Stimulation Reduces Neural Damage After Stroke in Non-human Primates

Ischemic stroke is a neurological condition that results in significant mortality and long-term disability for adults, creating huge health burdens worldwide. For stroke patients, acute intervention offers the most critical therapeutic opportunity as it can reduce irreversible tissue injury and improve functional outcomes. However, currently available treatments within the acute window are highly limited. Although emerging neuromodulation therapies have been tested for chronic stroke patients, acute stimulation is rarely studied due to the risk of causing adverse effects related to ischemia-induced electrical instability. To address this gap, we combined electrophysiology and histology tools to investigate the effects of acute electrical stimulation on ischemic neural damage in non-human primates. Specifically, we induced photothrombotic lesions in the monkey sensorimotor cortex while collecting electrocorticography (ECoG) signals through a customized neural interface. Gamma activity in ECoG was used as an electrophysiological marker to track the effects of stimulation on neural activation. Meanwhile, histological analysis including Nissl, cFos, and microglial staining was performed to evaluate the tissue response to ischemic injury. Comparing stimulated monkeys to controls, we found that theta-burst stimulation administered directly adjacent to the ischemic infarct at 1 hour post-stroke briefly inhibits peri-infarct neuronal activation as reflected by decreased ECoG gamma power and cFos expression. Meanwhile, lower microglial activation and smaller lesion volumes were observed in animals receiving post-stroke stimulation. Together, these results suggest that acute electrical stimulation can be used safely and effectively as an early stroke intervention to reduce excitotoxicity and inflammation, thus mitigating neural damage and enhancing stroke outcomes.

Determining the Optimal Stimulation Sessions for TMS-Induced Recovery of Upper Extremity Motor Function Post Stroke: A Randomized Controlled Trial

To find out the optimal treatment sessions of repetitive transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) for upper extremity dysfunction after stroke during the 6-week treatment and to explore its mechanism using motor-evoked potentials (MEPs) and resting-state functional magnetic resonance imaging (rs-fMRI), 72 participants with upper extremity motor dysfunction after ischemic stroke were randomly divided into the control group, 10-session, 20-session, and 30-session rTMS groups. Low-frequency (1 Hz) rTMS over the contralesional M1 was applied in all rTMS groups. The motor function of the upper extremity was assessed before and after treatment. In addition, MEPs and rs-fMRI data were analyzed to detect its effect on brain reorganization. After 6 weeks of treatment, there were significant differences in the Fugl-Meyer Assessment of the upper extremity and the Wolf Motor Function Test scores between the 10-session group and the 30-session group and between the 20- and 30-session groups and the control group, while there was no significant difference between the 20-session group and the 30-session group. Meanwhile, no significant difference was found between the 10-session group and the control group. The 20-session group of rTMS decreased the excitability of the contralesional corticospinal tract represented by the amplitudes of MEPs and enhanced the functional connectivity of the ipsilesional M1 or premotor cortex with the the precentral gyrus, postcentral gyrus, and cingulate gyrus, etc. In conclusion, the 20-session of rTMS protocol is the optimal treatment sessions of TMS for upper extremity dysfunction after stroke during the 6-week treatment. The potential mechanism is related to its influence on the excitability of the corticospinal tract and the remodeling of corticomotor functional networks.

Functional material-mediated wireless physical stimulation for neuro-modulation and regeneration

Nerve injuries and neurological diseases remain intractable clinical challenges. Despite the advantages of stem cell therapy in treating neurological disorders, uncontrollable cell fates and loss of cell function in vivo are still challenging. Recently, increasing attention has been given to the roles of external physical signals, such as electricity and ultrasound, in regulating stem cell fate as well as activating or inhibiting neuronal activity, which provides new insights for the treatment of neurological disorders. However, direct physical stimulations in vivo are short in accuracy and safety. Functional materials that can absorb energy from a specific physical field exerted in a wireless way and then release another localized physical signal hold great advantages in mediating noninvasive or minimally invasive accurate indirect physical stimulations to promote the therapeutic effect on neurological disorders. In this review, the mechanism by which various physical signals regulate stem cell fate and neuronal activity is summarized. Based on these concepts, the approaches of using functional materials to mediate indirect wireless physical stimulation for neuro-modulation and regeneration are systematically reviewed. We expect that this review will contribute to developing wireless platforms for neural stimulation as an assistance for the treatment of neurological diseases and injuries.

Long-term iTBS Improves Neural Functional Recovery by Reducing the Inflammatory Response and Inhibiting Neuronal Apoptosis Via miR-34c-5p/p53/Bax Signaling Pathway in Cerebral Ischemic Rats

To investigate intermittent theta-burst stimulation (iTBS) effect on ischemic stroke and the underlying mechanism of neurorehabilitation, we developed an ischemia/reperfusion (I/R) injury model in Sprague-Dawley (SD) rats using the middle cerebral artery occlusion/reperfusion (MCAO/r) method. Next, using different behavioral studies, we compared the improvement of the whole organism with and without iTBS administration for 28 days. We further explored the morphological and molecular biological alterations associated with neuronal apoptosis and neuroinflammation by TTC staining, HE staining, Nissl staining, immunofluorescence staining, ELISA, small RNA sequencing, RT-PCR, and western blot assays. The results showed that iTBS significantly protected against neurological deficits and neurological damage induced by cerebral I/R injury. iTBS also significantly decreased brain infarct volume and increased the number of surviving neurons after 28 days. Additionally, it was observed that iTBS decreased synaptic loss, suppressed activation of astrocytes and M1-polarized microglia, and simultaneously promoted M2-polarized microglial activation. Furthermore, iTBS intervention inhibited neuronal apoptosis and exerted a positive impact on the neuronal microenvironment by reducing neuroinflammation in cerebral I/R injured rats. To further investigate the iTBS mechanism, this study was conducted using small RNA transcriptome sequencing of various groups of peri-infarcted tissues. Bioinformatics analysis and RT-PCR discovered the possible involvement of miR-34c-5p in the mechanism of action. The target genes prediction and detection of dual-luciferase reporter genes confirmed that miR-34c-5p could inhibit neuronal apoptosis in cerebral I/R injured rats by regulating the p53/Bax signaling pathway. We also confirmed by RT-PCR and western blotting that miR-34c-5p inhibited Bax expression. In conclusion, our study supports that iTBS is vital in inhibiting neuronal apoptosis in cerebral I/R injured rats by mediating the miR-34c-5p involvement in regulating the p53/Bax signaling pathway.

Effects of Repetitive Transcranial Magnetic Stimulation on Pallidum GABAergic Neurons and Motor Function in Rat Models of Kernicterus

Kernicterus is a serious complication of hyperbilirubinemia, caused by neuronal injury due to excessive unconjugated bilirubin (UCB) in specific brain areas. This injury induced by this accumulation in the globus pallidus can induce severe motor dysfunction. Repetitive transcranial magnetic stimulation (rTMS) has shown neuroprotective effects in various neurological diseases. This study aimed to investigate the effects of rTMS on pallidal nerve damage and motor dysfunction in a rat model of kernicterus. Rats were divided into a sham group (n = 16), a model group (bilirubin with sham rTMS; n = 16) and an rTMS group (bilirubin with rTMS; n = 16). High-frequency rTMS (10 Hz) was applied starting from 24 h postmodeling for 7 days. The rotarod test, western blotting and immunohistochemical staining were performed to measure motor function and protein expression levels. The rTMS mitigated the negative effects of UCB on the general health of kernicterus-model rats and improved their growth and development. Furthermore, the rTMS alleviated UCB-induced motor dysfunction and increased the expression of GABAergic neuronal marker GAD67 in the globus pallidus. Notably, it also inhibited apoptosis-related protein caspase-3 activation. In conclusion, rTMS could alleviate motor dysfunction by inhibiting apoptosis and increasing globus pallidus GAD67 in kernicterus rat models, indicating that it may be a promising treatment for kernicterus.

Cerebral Hemodynamic Changes during Unaffected Handgrip Exercises in Stroke Patients: An fNIRS Study

This study aimed to assess the effect of the altered strength of the sound limb on the hemodynamics in the affected brain of stroke patients. We recruited 20 stroke patients to detect changes in the HbO concentrations in the bilateral prefrontal cortex (PFC), sensorimotor cortex (SMC), and occipital lobe (OL). We performed functional near-infrared spectroscopy (fNIRS) to detect changes in oxyhemoglobin (HbO) concentrations in regions of interest (ROIs) in the bilateral cerebral hemispheres of stroke patients while they performed 20%, 50%, and 80% maximal voluntary contraction (MVC) levels of handgrip tasks with the unaffected hands. The results suggest that when patients performed handgrip tasks with 50% of the MVC force, SMC in the affected cerebral hemisphere was strongly activated and the change in the HbO concentration was similar to that of the handgrip with 80% of MVC. When the force was 50% of MVC, the SMC in the affected hemisphere showed a more proportional activation than that at 80% MVC. Overall, this research suggests that stroke patients with a poor upper limb function should perform motor training with their sound hands at 50% of the MVC grip task to activate the ipsilesional hemisphere.