Astrocytes contribute to the neuronal recovery promoted by high‐frequency repetitive magnetic stimulation in in vitro models of ischemia

Abstract

After decades of effort, there are no effective clinical treatments to induce the recovery of ischemia-injured tissues, and among the several strategies that have been explored, repetitive transcranial magnetic stimulation has proven to be one of the most promising, with beneficial effects in limb motor function, aphasia, hemispatial neglect, or dysphagia. Despite the clinical evidences, little is known about the mechanisms underlying those effects. The present study aimed to explore the cellular and molecular effects of high-frequency repetitive magnetic stimulation (HF-rMS) on an in vitro model of ischemia. Using primary cortical cultures exposed to oxygen and glucose deprivation followed by reperfusion, we observed that HF-rMS treatment prevents the ischemia-induced neuronal death by 21.2%, and the neurite degeneration triggered by ischemia. Our results also demonstrate that with this treatment there is an increase of 89.2% on the number cells expressing ERK1/2, of 20.1% on the number of cells expressing c-Fos, and a synaptogenic effect, through an increase of 62.9% in the number of synaptic puncta as well as of 49.4% in their intensity. Interestingly, our results indicate that astrocytes are crucial to the beneficial effects triggered by HF-rMS after ischemia, thus suggesting a direct effect of HF-rMS on these cells. The modulation of astrocytes with this non-invasive brain stimulation technique is a promising approach to promote the recovery of ischemia-induced injured tissues; however, it is essential to understand how these effects can be modulated in order to optimize the protocols and enhance the beneficial outcomes.

High‐frequency repetitive magnetic stimulation rescues ischemia‐injured neurons through modulation of glial‐derived neurotrophic factor present in the astrocyteʼs secretome

“…Furthermore, data from our group showed that applying a highfrequency repetitive magnetic stimulation (HF-rMS) protocol to cortical cultures subjected to ischemia reduced neuronal death, neurite degeneration, and increased synaptic plasticity. Interestingly, our data also showed that astrocytes are crucial to the beneficial effects observed, suggesting that HF-rMS may directly affect these glial cells (Roque et al, 2021).…”

“…Previous studies from our group demonstrated that astrocytes are crucial to the beneficial effects induced by HF-rMS after ischemia, thus raising the hypothesis that HF-rMS may modulate astrocyte activity (Roque et al, 2021). To evaluate HF-rMS impact on the release of mediators by astrocytes, neuron-enriched cultures were exposed to CM from astrocyte-enriched cultures (astrocyte-CM) and neuron-glial cultures (neuron glial-CM) for 24 h (see the experimental design on Figure S1).…”

“…We previously reported that HF-rMS prevented ischemia-induced neurite degeneration in neuron-glial cortical cultures subjected to OGD (Roque et al, 2021). To determine if those effects are triggered by mediators released to the medium in response to HF-rMS, we evaluated the number of neurites, their length, and F I G U R E 1 Effects of CM from astrocyte-enriched and from neuron-glial cultures exposed to OGD and treated with HF-rMS on the number of neurons expressing ERK1/2.…”

“…Cell cultures were subjected to a single HF-rMS session immediately after OGD. The rMS protocol used throughout the study was based on previous studies of our group (Roque et al, 2021). In each session, the figure-8 coil (MCF-B70) was placed over each culture dish, aligning the center of the plate with the center of the coil, thus maximizing magnetic field exposure.…”

Cyto-Neurology in Ischemia

“…It seems clear that the neuronal failure triggered by the ischemic cascade involves several cellular pathways and structures, raising the idea that to recover the penumbra neurons, strategies should be used that have an integrative approach by modulating several of the above-mentioned detrimental effects. Among the several brain-repair-based therapies that have been proposed, repetitive transcranial magnetic stimulation (rTMS) has shown promising results by preventing apoptosis, neurite rupture, and inflammation, as well as by increasing neuroprotection, neurogenesis, and synaptic plasticity in several animal [5] and cellular models [6]. Those effects are correlated with an improvement of neurological, motor, learning, memory, and cognitive deficits, as reviewed by Zong and colleagues 2022 [5].…”