Optogenetics for controlling seizure circuits for translational approaches

Optogenetic approaches for neural tissue regeneration: A review of basic optogenetic principles and target cells for therapy

Optogenetics has revolutionized the field of neuroscience by enabling precise control of neural activity through light-sensitive proteins known as opsins. This review article discusses the fundamental principles of optogenetics, including the activation of both excitatory and inhibitory opsins, as well as the development of optogenetic models that utilize recombinant viral vectors. A considerable portion of the article addresses the limitations of optogenetic tools and explores strategies to overcome these challenges. These strategies include the use of adeno-associated viruses, cell-specific promoters, modified opsins, and methodologies such as bioluminescent optogenetics. The application of viral recombinant vectors, particularly adeno-associated viruses, is emerging as a promising avenue for clinical use in delivering opsins to target cells. This trend indicates the potential for creating tools that offer greater flexibility and accuracy in opsin delivery. The adaptations of these viral vectors provide advantages in optogenetic studies by allowing for the restricted expression of opsins through cell-specific promoters and various viral serotypes. The article also examines different cellular targets for optogenetics, including neurons, astrocytes, microglia, and Schwann cells. Utilizing specific promoters for opsin expression in these cells is essential for achieving precise and efficient stimulation. Research has demonstrated that optogenetic stimulation of both neurons and glial cells-particularly the distinct phenotypes of microglia, astrocytes, and Schwann cells-can have therapeutic effects in neurological diseases. Glial cells are increasingly recognized as important targets for the treatment of these disorders. Furthermore, the article emphasizes the emerging field of bioluminescent optogenetics, which combines optogenetic principles with bioluminescent proteins to visualize and manipulate neural activity in real time. By integrating molecular genetics techniques with bioluminescence, researchers have developed methods to monitor neuronal activity efficiently and less invasively, enhancing our understanding of central nervous system function and the mechanisms of plasticity in neurological disorders beyond traditional neurobiological methods. Evidence has shown that optogenetic modulation can enhance motor axon regeneration, achieve complete sensory reinnervation, and accelerate the recovery of neuromuscular function. This approach also induces complex patterns of coordinated motor neuron activity and promotes neural reorganization. Optogenetic approaches hold immense potential for therapeutic interventions in the central nervous system. They enable precise control of neural circuits and may offer new treatments for neurological disorders, particularly spinal cord injuries, peripheral nerve injuries, and other neurodegenerative diseases.

Neural circuit mechanisms of epilepsy: Maintenance of homeostasis at the cellular, synaptic, and neurotransmitter levels

Epilepsy, a common neurological disorder, is characterized by recurrent seizures that can lead to cognitive, psychological, and neurobiological consequences. The pathogenesis of epilepsy involves neuronal dysfunction at the molecular, cellular, and neural circuit levels. Abnormal molecular signaling pathways or dysfunction of specific cell types can lead to epilepsy by disrupting the normal functioning of neural circuits. The continuous emergence of new technologies and the rapid advancement of existing ones have facilitated the discovery and comprehensive understanding of the neural circuit mechanisms underlying epilepsy. Therefore, this review aims to investigate the current understanding of the neural circuit mechanisms in epilepsy based on various technologies, including electroencephalography, magnetic resonance imaging, optogenetics, chemogenetics, deep brain stimulation, and brain-computer interfaces. Additionally, this review discusses these mechanisms from three perspectives: structural, synaptic, and transmitter circuits. The findings reveal that the neural circuit mechanisms of epilepsy encompass information transmission among different structures, interactions within the same structure, and the maintenance of homeostasis at the cellular, synaptic, and neurotransmitter levels. These findings offer new insights for investigating the pathophysiological mechanisms of epilepsy and enhancing its clinical diagnosis and treatment.

Recent progress and challenges in gene therapy for pharmacoresistant focal epilepsy

Pharmacoresistant focal epilepsy represents a major unmet need. Recent years have seen several gene therapy strategies validated mainly in rodent models of temporal lobe epilepsy, and some of these have been de-risked for clinical trials. This review considers some of the challenges in progressing from experimental models to the clinic. Among these are identifying promising promoter-transgene combinations, establishing safe and efficacious doses, achieving optimal delivery, and extrapolating across different aetiologies.

Channeling Seizure Control: Optogenetics in Human Brain Slices

Multimodal evaluation of network activity and optogenetic interventions in human hippocampal slices Andrews JP, Geng J, Voitiuk K, Elliott MAT, Shin D, Robbins A, Spaeth A, Wang A, Li L, Solis D, Keefe MG, Sevetson JL, Rivera de Jesús JA, Donohue KC, Larson HH, Ehrlich D, Auguste KI, Salama S, Sohal V, Sharf T, Haussler D, Cadwell CR, Schaffer DV, Chang EF, Teodorescu M, Nowakowski TJ. Nat Neurosci 27(12):2487–2499. Seizures are made up of the coordinated activity of networks of neurons, suggesting that control of neurons in the pathologic circuits of epilepsy could allow for control of the disease. Optogenetics has been effective at stopping seizure-like activity in nonhuman disease models by increasing inhibitory tone or decreasing excitation, although this effect has not been shown in human brain tissue. Many of the genetic means for achieving channel rhodopsin expression in nonhuman models are not possible in humans, and vector-mediated methods are susceptible to species-specific tropism that may affect translational potential. Here we demonstrate adeno-associated virus-mediated, optogenetic reductions in network firing rates of human hippocampal slices recorded on high-density microelectrode arrays under several hyperactivity-provoking conditions. This platform can serve to bridge the gap between human and animal studies by exploring genetic interventions on network activity in human brain tissue.

Differential roles of Na V 1.2 and Na V 1.6 in neocortical pyramidal cell excitability

Mature neocortical pyramidal cells functionally express two sodium channel (Na V ) isoforms: Na V 1.2 and Na V 1.6. These isoforms are differentially localized to pyramidal cell compartments, and as such are thought to contribute to different aspects of neuronal excitability. But determining their precise roles in pyramidal cell excitability has been hampered by a lack of tools that allow for selective, acute block of each isoform individually. Here, we leveraged aryl sulfonamide-based molecule (ASC) inhibitors of Na V channels that exhibit state-dependent block of both Na V 1.2 and Na V 1.6, along with knock-in mice with changes in Na V 1.2 or Na V 1.6 structure that prevents ASC binding. This allowed for acute, potent, and reversible block of individual isoforms that permitted dissection of the unique contributions of Na V 1.2 and Na V 1.6 in pyramidal cell excitability. Remarkably, block of each isoform had contrasting-and in some situations, opposing-effects on neuronal action potential output, with Na V 1.6 block decreasing and Na V 1.2 block increasing output. Thus, Na V isoforms have unique roles in regulating different aspects of pyramidal cell excitability, and our work may help guide development of therapeutics designed to temper hyperexcitability through selective Na V isoform blockade.

Advancing Neuroscience and Therapy: Insights into Genetic and Non-Genetic Neuromodulation Approaches

Neuromodulation stands as a cutting-edge approach in the fields of neuroscience and therapeutic intervention typically involving the regulation of neural activity through physical and chemical stimuli. The purpose of this review is to provide an overview and evaluation of different neuromodulation techniques, anticipating a clearer understanding of the future developmental trajectories and the challenges faced within the domain of neuromodulation that can be achieved. This review categorizes neuromodulation techniques into genetic neuromodulation methods (including optogenetics, chemogenetics, sonogenetics, and magnetogenetics) and non-genetic neuromodulation methods (including deep brain stimulation, transcranial magnetic stimulation, transcranial direct current stimulation, transcranial ultrasound stimulation, photobiomodulation therapy, infrared neuromodulation, electromagnetic stimulation, sensory stimulation therapy, and multi-physical-factor stimulation techniques). By systematically evaluating the principles, mechanisms, advantages, limitations, and efficacy in modulating neuronal activity and the potential applications in interventions of neurological disorders of these neuromodulation techniques, a comprehensive picture is gradually emerging regarding the advantages and challenges of neuromodulation techniques, their developmental trajectory, and their potential clinical applications. This review highlights significant advancements in applying these techniques to treat neurological and psychiatric disorders. Genetic methods, such as sonogenetics and magnetogenetics, have demonstrated high specificity and temporal precision in targeting neuronal populations, while non-genetic methods, such as transcranial magnetic stimulation and photobiomodulation therapy, offer noninvasive and versatile clinical intervention options. The transformative potential of these neuromodulation techniques in neuroscience research and clinical practice is underscored, emphasizing the need for integration and innovation in technologies, the optimization of delivery methods, the improvement of mediums, and the evaluation of toxicity to fully harness their therapeutic potential.

Multimodal evaluation of network activity and optogenetic interventions in human hippocampal slices

Seizures are made up of the coordinated activity of networks of neurons, suggesting that control of neurons in the pathologic circuits of epilepsy could allow for control of the disease. Optogenetics has been effective at stopping seizure-like activity in non-human disease models by increasing inhibitory tone or decreasing excitation, although this effect has not been shown in human brain tissue. Many of the genetic means for achieving channelrhodopsin expression in non-human models are not possible in humans, and vector-mediated methods are susceptible to species-specific tropism that may affect translational potential. Here we demonstrate adeno-associated virus-mediated, optogenetic reductions in network firing rates of human hippocampal slices recorded on high-density microelectrode arrays under several hyperactivity-provoking conditions. This platform can serve to bridge the gap between human and animal studies by exploring genetic interventions on network activity in human brain tissue.

A review of cell-type specific circuit mechanisms underlying epilepsy

Epilepsy is a prevalent neurological disorder, yet its underlying mechanisms remain incompletely understood. Accumulated studies have indicated that epilepsy is characterized by abnormal neural circuits. Understanding the circuit mechanisms is crucial for comprehending the pathogenesis of epilepsy. With advances in tracing and modulating tools for neural circuits, some epileptic circuits have been uncovered. This comprehensive review focuses on the circuit mechanisms underlying epilepsy in various neuronal subtypes, elucidating their distinct roles. Epileptic seizures are primarily characterized by the hyperactivity of glutamatergic neurons and inhibition of GABAergic neurons. However, specific activated GABAergic neurons and suppressed glutamatergic neurons exacerbate epilepsy through preferentially regulating the activity of GABAergic neurons within epileptic circuits. Distinct subtypes of GABAergic neurons contribute differently to epileptic activities, potentially due to their diverse connection patterns. Moreover, identical GABAergic neurons may assume distinct roles in different stages of epilepsy. Both GABAergic neurons and glutamatergic neurons with long-range projecting fibers innervate multiple nuclei; nevertheless, not all of these circuits contribute to epileptic activities. Epileptic circuits originating from the same nuclei may display diverse contributions to epileptic activities, and certain glutamatergic circuits from the same nuclei may even exert opposing effects on epilepsy. Neuromodulatory neurons, including cholinergic, serotonergic, dopaminergic, and noradrenergic neurons, are also implicated in epilepsy, although the underlying circuit mechanisms remain poorly understood. These studies suggest that epileptic nuclei establish intricate connections through cell-type-specific circuits and play pivotal roles in epilepsy. However, there are still limitations in knowledge and methods, and further understanding of epileptic circuits is crucial, particularly in the context of refractory epilepsy.

Opticool: Cutting-edge transgenic optical tools

Only a few short decades have passed since the sequencing of GFP, yet the modern repertoire of transgenically encoded optical tools implies an exponential proliferation of ever improving constructions to interrogate the subcellular environment. A myriad of tags for labeling proteins, RNA, or DNA have arisen in the last few decades, facilitating unprecedented visualization of subcellular components and processes. Development of a broad array of modern genetically encoded sensors allows real-time, in vivo detection of molecule levels, pH, forces, enzyme activity, and other subcellular and extracellular phenomena in ever expanding contexts. Optogenetic, genetically encoded optically controlled manipulation systems have gained traction in the biological research community and facilitate single-cell, real-time modulation of protein function in vivo in ever broadening, novel applications. While this field continues to explosively expand, references are needed to assist scientists seeking to use and improve these transgenic devices in new and exciting ways to interrogate development and disease. In this review, we endeavor to highlight the state and trajectory of the field of in vivo transgenic optical tools.

Intravital photoacoustic brain stimulation with high-precision

Significance

Neural regulation at high precision vitally contributes to propelling fundamental understanding in the field of neuroscience and providing innovative clinical treatment options. Recently, photoacoustic brain stimulation has emerged as a cutting-edge method for precise neuromodulation and shows great potential for clinical application.

Aim

The goal of this perspective is to outline the advancements in photoacoustic brain stimulation in recent years. And, we also provide an outlook delineating several prospective paths through which this burgeoning approach may be substantively refined for augmented capability and wider implementations.

Approach

First, the mechanisms of photoacoustic generation as well as the potential mechanisms of photoacoustic brain stimulation are provided and discussed. Then, the state-of-the-art achievements corresponding to this technology are reviewed. Finally, future directions for photoacoustic technology in neuromodulation are provided.

Results

Intensive research endeavors have prompted substantial advancements in photoacoustic brain stimulation, illuminating the unique advantages of this modality for noninvasive and high-precision neuromodulation via a nongenetic way. It is envisaged that further technology optimization and randomized prospective clinical trials will enable a wide acceptance of photoacoustic brain stimulation in clinical practice.

Conclusions

The innovative practice of photoacoustic technology serves as a multifaceted neuromodulation approach, possessing noninvasive, high-accuracy, and nongenetic characteristics. It has a great potential that could considerably enhance not only the fundamental underpinnings of neuroscience research but also its practical implementations in a clinical setting.

A Comprehensive Review of Emerging Trends and Innovative Therapies in Epilepsy Management

Epilepsy is a complex neurological disorder affecting millions worldwide, with a substantial number of patients facing drug-resistant epilepsy. This comprehensive review explores innovative therapies for epilepsy management, focusing on their principles, clinical evidence, and potential applications. Traditional antiseizure medications (ASMs) form the cornerstone of epilepsy treatment, but their limitations necessitate alternative approaches. The review delves into cutting-edge therapies such as responsive neurostimulation (RNS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS), highlighting their mechanisms of action and promising clinical outcomes. Additionally, the potential of gene therapies and optogenetics in epilepsy research is discussed, revealing groundbreaking findings that shed light on seizure mechanisms. Insights into cannabidiol (CBD) and the ketogenic diet as adjunctive therapies further broaden the spectrum of epilepsy management. Challenges in achieving seizure control with traditional therapies, including treatment resistance and individual variability, are addressed. The importance of staying updated with emerging trends in epilepsy management is emphasized, along with the hope for improved therapeutic options. Future research directions, such as combining therapies, AI applications, and non-invasive optogenetics, hold promise for personalized and effective epilepsy treatment. As the field advances, collaboration among researchers of natural and synthetic biochemistry, clinicians from different streams and various forms of medicine, and patients will drive progress toward better seizure control and a higher quality of life for individuals living with epilepsy.