Transcranial ultrasound stimulation applied in ischemic stroke rehabilitation: A review

Advances in Optogenetics and Thermogenetics for Control of Non-Neuronal Cells and Tissues in Biomedical Research

Optogenetics and chemogenetics are relatively new biomedical technologies that emerged 20 years ago and have been evolving rapidly since then. This has been made possible by the combined use of genetic engineering, optics, and electrophysiology. With the development of optogenetics and thermogenetics, the molecular tools for cellular control are continuously being optimized, studied, and modified, expanding both their applications and their biomedical uses. The most notable changes have occurred in the basic life sciences, especially in neurobiology and the activation of neurons to control behavior. Currently, these methods of activation have gone far beyond neurobiology and are being used in cardiovascular research, for potential cancer therapy, to control metabolism, etc. In this review, we provide brief information on the types of molecular tools for optogenetic and thermogenetic methods─microbial rhodopsins and proteins of the TRP superfamily─and also consider their applications in the field of activation of non-neuronal tissues and mammalian cells. We also consider the potential of these technologies and the prospects for the use of optogenetics and thermogenetics in biomedical research.

Enhanced Small Extracellular Vesicle Uptake by Activated Interneurons Improves Stroke Recovery in Mice

Neuronal circuitry remodelling, which comprises excitatory and inhibitory neurons, is critical for improving neurological outcomes after a stroke. Preclinical studies have shown that small extracellular vesicles (sEVs) have a therapeutic effect on stroke recovery. However, it is highly challenging to use sEVs to specifically target individual neuronal populations to enhance neuronal circuitry remodelling after stroke. In the present study, using a chemogenetic approach to specifically activate peri-infarct cortical interneurons in combination with the administration of sEVs derived from cerebral endothelial cells (CEC-sEVs), we showed that the CEC-sEVs were preferentially taken up by the activated neurons, leading to significant improvement of functional outcome after stroke, which was associated with augmentation of peri-infarct cortical axonal/dendritic outgrowth and of axonal remodelling of the corticospinal tract. The ultrastructural and Western blot analyses revealed that neurons with internalization of CEC-sEVs exhibited significantly reduced numbers of damaged mitochondria and proteins that mediate dysfunctional mitochondria, respectively. Together, these data indicate that the augmented uptake of CEC-sEVs by activated peri-infarct cortical interneurons facilitates neuronal circuitry remodelling and functional recovery after stroke, which has the potential to be a novel therapy for improving stroke recovery.

Advancing neurological disorders therapies: Organic nanoparticles as a key to blood-brain barrier penetration

The blood-brain barrier (BBB) plays a vital role in protecting the central nervous system (CNS) by preventing the entry of harmful pathogens from the bloodstream. However, this barrier also presents a significant obstacle when it comes to delivering drugs for the treatment of neurodegenerative diseases and brain cancer. Recent breakthroughs in nanotechnology have paved the way for the creation of a wide range of nanoparticles (NPs) that can serve as carriers for diagnosis and therapy. Regarding their promising properties, organic NPs have the potential to be used as effective carriers for drug delivery across the BBB based on recent advancements. These remarkable NPs have the ability to penetrate the BBB using various mechanisms. This review offers a comprehensive examination of the intricate structure and distinct properties of the BBB, emphasizing its crucial function in preserving brain balance and regulating the transport of ions and molecules. The disruption of the BBB in conditions such as stroke, Alzheimer's disease, and Parkinson's disease highlights the importance of developing creative approaches for delivering drugs. Through the encapsulation of therapeutic molecules and the precise targeting of transport processes in the brain vasculature, organic NP formulations present a hopeful strategy to improve drug transport across the BBB. We explore the changes in properties of the BBB in various pathological conditions and investigate the factors that affect the successful delivery of organic NPs into the brain. In addition, we explore the most promising delivery systems associated with NPs that have shown positive results in treating neurodegenerative and ischemic disorders. This review opens up new possibilities for nanotechnology-based therapies in cerebral diseases.

Transcranial ultrasound with electrical stimulation of the cerebello-parietal nucleus on cerebral blood flow and limb function in patients with stroke

OBJECTIVE

To investigate the efficacy of transcranial ultrasound stimulation (TUS) combined with Fastigial nucleus stimulation (FNS) on cerebral blood flow and limb function in patients in the acute phase of ischemic stroke.

METHODS

A total of 90 patients in the acute phase of ischemic stroke were randomly divided into an FNS, TUS, and TUS + FNS group (30 patients each), and all patients also received conventional treatment. The FNS group was treated with FNS alone. The TUS group was treated with TUS alone. The TUS + FNS group was treated with both TUS and FNS. The three groups were treated once a day for 6 days a week.

RESULTS

The simplified Fugl-Meyer Assessment (FMA) and Barthel index scores (BI), and the peak systolic blood flow velocity (Vs) and the mean blood flow velocity (Vm) of the anterior cerebral artery, middle cerebral artery, and posterior cerebral artery, were significantly higher in all three groups compared with before treatment (P < 0.05). The scores for the TUS group were higher than for the FNS group (P < 0.05), and the scores of the TUS + FNS group were higher than the TUS and FNS groups, respectively (P < 0.05). The total effective rate was 63.3%, 70.0%, and 90.0% in the FNS, TUS, and TUS + FNS groups, respectively, and the difference between the three groups was statistically significant (P < 0.05).

CONCLUSION

The FNS and TUS treatments improved the function of and accelerated cerebral blood flow in patients with acute ischemic stroke to different degrees, and the combined use of both treatment types was overall more effective.

Advancements in ultrasound-mediated drug delivery for central nervous system disorders

INTRODUCTION

Central nervous system (CNS) disorders present major therapeutic challenges due to the presence of the blood - brain barrier (BBB) and disease heterogeneity. The BBB impedes most therapeutic agents, which restricts conventional treatments. Focused ultrasound (FUS) -assisted delivery offers a novel solution by temporarily disrupting the BBB and thereby enhancing drug delivery to the CNS.

AREAS COVERED

This review outlines the fundamental principles of FUS-assisted drug delivery technology, with an emphasis on its role in enhancing the spatial precision of therapeutic interventions and its molecular effects on the cellular composition of the BBB. Recent promising clinical studies are surveyed, and a comparative analysis of current US-assisted delivery system is provided. Additionally, the latest advancements and challenges of this technology are discussed.

EXPERT OPINION

FUS-mediated drug delivery shows promise, but the clinical translation of research findings is challenging. Key issues include safety, dosage optimization, and balancing efficacy with the risk of tissue damage. Continued research is crucial to address these challenges and bridge the gap between preclinical and clinical applications, and could transform treatments of CNS disorders.

Somatosensory integration in robot-assisted motor restoration post-stroke

Disruption of somatosensorimotor integration (SMI) after stroke is a significant obstacle to achieving precise motor restoration. Integrating somatosensory input into motor relearning to reconstruct SMI is critical during stroke rehabilitation. However, current robotic approaches focus primarily on precise control of repetitive movements and rarely effectively engage and modulate somatosensory responses, which impedes motor rehabilitation that relies on SMI. This article discusses how to effectively regulate somatosensory feedback from target muscles through peripheral and central neuromodulatory stimulations based on quantitatively measured somatosensory responses in real time during robot-assisted rehabilitation after stroke. Further development of standardized recording protocols and diagnostic databases of quantitative neuroimaging features in response to post-stroke somatosensory stimulations for real-time precise detection, and optimized combinations of peripheral somatosensory stimulations with robot assistance and central nervous neuromodulation are needed to enhance the recruitment of targeted ascending neuromuscular pathways in robot-assisted training, aiming to achieve precise muscle control and integrated somatosensorimotor functions, thereby improving long-term neurorehabilitation after stroke.

Progress in Noninvasive Low-Intensity Focused Ultrasound Neuromodulation

Low-intensity focused ultrasound represents groundbreaking medical advancements, characterized by its noninvasive feature, safety, precision, and broad neuromodulatory capabilities. This technology operates through mechanisms, for example, acoustic radiation force, cavitation, and thermal effects. Notably, with the evolution of medical technology, ultrasound neuromodulation has been gradually applied in treating central nervous system diseases, especially stroke. Furthermore, burgeoning research areas such as sonogenetics and nanotechnology show promising potential. Despite the benefit of low-intensity focused ultrasound the precise biophysical mechanism of ultrasound neuromodulation still need further exploration. This review discusses the recent and ongoing developments of low-intensity focused ultrasound for neurological regulation, covering the underlying rationale to current utility and the challenges that impede its further development and broader adoption of this promising alternative to noninvasive therapy.

Low-intensity pulsed ultrasound modulates disease progression in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the progressive loss of motor neurons in the brain and spinal cord, and there are no effective drug treatments. Low-intensity pulsed ultrasound (LIPUS) has garnered attention as a promising noninvasive neuromodulation method. In this study, we investigate its effects on the motor cortex and underlying mechanisms using the SOD1G93A mouse model of ALS. Our results show that LIPUS treatment delays disease onset and prolongs lifespan in ALS mice. LIPUS significantly increases cerebral blood flow in the motor cortex by preserving vascular endothelial cell integrity and increasing microvascular density, which may be mediated via the ion channel TRPV4. RNA sequencing analysis reveals that LIPUS substantially reduces the expression of genes associated with neuroinflammation. These findings suggest that LIPUS applied to the motor cortex may represent a potentially effective therapeutic tool for the treatment of ALS.

Transcranial Direct Current Stimulation to Ameliorate Post-Stroke Cognitive Impairment

Post-stroke cognitive impairment is a common and disabling condition with few effective therapeutic options. After stroke, neural reorganization and other neuroplastic processes occur in response to ischemic injury, which can result in clinical improvement through spontaneous recovery. Neuromodulation through transcranial direct current stimulation (tDCS) is a promising intervention to augment underlying neuroplasticity in order to improve cognitive function. This form of neuromodulation leverages mechanisms of neuroplasticity post-stroke to optimize neural reorganization and improve function. In this review, we summarize the current state of cognitive neurorehabilitation post-stroke, the practical features of tDCS, its uses in stroke-related cognitive impairment across cognitive domains, and special considerations for the use of tDCS in the post-stroke patient population.

An implantable piezoelectric ultrasound stimulator (ImPULS) for deep brain activation

Precise neurostimulation can revolutionize therapies for neurological disorders. Electrode-based stimulation devices face challenges in achieving precise and consistent targeting due to the immune response and the limited penetration of electrical fields. Ultrasound can aid in energy propagation, but transcranial ultrasound stimulation in the deep brain has limited spatial resolution caused by bone and tissue scattering. Here, we report an implantable piezoelectric ultrasound stimulator (ImPULS) that generates an ultrasonic focal pressure of 100 kPa to modulate the activity of neurons. ImPULS is a fully-encapsulated, flexible piezoelectric micromachined ultrasound transducer that incorporates a biocompatible piezoceramic, potassium sodium niobate [(K,Na)NbO3]. The absence of electrochemically active elements poses a new strategy for achieving long-term stability. We demonstrated that ImPULS can i) excite neurons in a mouse hippocampal slice ex vivo, ii) activate cells in the hippocampus of an anesthetized mouse to induce expression of activity-dependent gene c-Fos, and iii) stimulate dopaminergic neurons in the substantia nigra pars compacta to elicit time-locked modulation of nigrostriatal dopamine release. This work introduces a non-genetic ultrasound platform for spatially-localized neural stimulation and exploration of basic functions in the deep brain.

Shedding light on ultrasound in action: Optical and optoacoustic monitoring of ultrasound brain interventions

Monitoring brain responses to ultrasonic interventions is becoming an important pillar of a growing number of applications employing acoustic waves to actuate and cure the brain. Optical interrogation of living tissues provides a unique means for retrieving functional and molecular information related to brain activity and disease-specific biomarkers. The hybrid optoacoustic imaging methods have further enabled deep-tissue imaging with optical contrast at high spatial and temporal resolution. The marriage between light and sound thus brings together the highly complementary advantages of both modalities toward high precision interrogation, stimulation, and therapy of the brain with strong impact in the fields of ultrasound neuromodulation, gene and drug delivery, or noninvasive treatments of neurological and neurodegenerative disorders. In this review, we elaborate on current advances in optical and optoacoustic monitoring of ultrasound interventions. We describe the main principles and mechanisms underlying each method before diving into the corresponding biomedical applications. We identify areas of improvement as well as promising approaches with clinical translation potential.

Patient-specific modeling for guided rehabilitation of stroke patients: the BrainX3 use-case

BrainX3 is an interactive neuroinformatics platform that has been thoughtfully designed to support neuroscientists and clinicians with the visualization, analysis, and simulation of human neuroimaging, electrophysiological data, and brain models. The platform is intended to facilitate research and clinical use cases, with a focus on personalized medicine diagnostics, prognostics, and intervention decisions. BrainX3 is designed to provide an intuitive user experience and is equipped to handle different data types and 3D visualizations. To enhance patient-based analysis, and in keeping with the principles of personalized medicine, we propose a framework that can assist clinicians in identifying lesions and making patient-specific intervention decisions. To this end, we are developing an AI-based model for lesion identification, along with a mapping of tract information. By leveraging the patient's lesion information, we can gain valuable insights into the structural damage caused by the lesion. Furthermore, constraining whole-brain models with patient-specific disconnection masks can allow for the detection of mesoscale excitatory-inhibitory imbalances that cause disruptions in macroscale network properties. Finally, such information has the potential to guide neuromodulation approaches, assisting in the choice of candidate targets for stimulation techniques such as Transcranial Ultrasound Stimulation (TUS), which modulate E-I balance, potentiating cortical reorganization and the restoration of the dynamics and functionality disrupted due to the lesion.