Serotype-based evaluation of an optogenetic construct in rat cortical astrocytes

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.

Impact of volume and expression time in an AAV-delivered channelrhodopsin

Optogenetics has revolutionised neuroscience research, but at the same time has brought a plethora of new variables to consider when designing an experiment with AAV-based targeted gene delivery. Some concerns have been raised regarding the impact of AAV injection volume and expression time in relation to longitudinal experimental designs. In this study, we investigated the efficiency of optically evoked post-synaptic responses in connection to two variables: the volume of the injected virus and the expression time of the virus. For this purpose, we expressed the blue-shifted ChR2, oChIEF, employing a widely used AAV vector delivery strategy. We found that the volume of the injected virus has a minimal impact on the efficiency of optically-evoked postsynaptic population responses. The expression time, on the other hand, has a pronounced effect, with a gradual reduction in the population responses beyond 4 weeks of expression. We strongly advise to monitor time-dependent expression profiles when planning or conducting long-term experiments that depend on successful and stable channelrhodopsin expression.

Optogenetically Engineered Neurons Differentiated from Human SH-SY5Y Cells Survived and Expressed ChR2 in 3D Hydrogel

The cases of brain degenerative disease will rise as the human population ages. Current treatments have a transient effect and lack an investigative system that is physiologically relevant for testing. There is evidence suggesting optogenetic stimulation is a potential strategy; however, an in vitro disease and optogenetic model requires a three-dimensional microenvironment. Alginate is a promising material for tissue and optogenetic engineering. Although it is bioinert, alginate hydrogel is transparent and therefore allows optical penetration for stimulation. In this study, alginate was functionalized with arginine-glycine-aspartate acid (RGD) to serve as a 3D platform for encapsulation of human SH-SY5Y cells, which were optogenetically modified and characterized. The RGD-alginate hydrogels were tested for swelling and degradation. Prior to encapsulation, the cells were assessed for neuronal expression and optical-stimulation response. The results showed that RGD-alginate possessed a consistent swelling ratio of 18% on day 7, and degradation remained between 3.7−5% throughout 14 days. Optogenetically modified SH-SY5Y cells were highly viable (>85%) after lentiviral transduction and neuronal differentiation. The cells demonstrated properties of functional neurons, developing beta III tubulin (TuJ1)-positive long neurites, forming neural networks, and expressing vGlut2. Action potentials were produced upon optical stimulation. The neurons derived from human SH-SY5Y cells were successfully genetically modified and encapsulated; they survived and expressed ChR2 in an RGD-alginate hydrogel system.

Multichannel Wireless Neurosensing System for battery-free monitoring of neuronal activity

Electrical activity recordings are critical for evaluating and understanding brain function. We present a novel wireless, implantable, and battery-free device, namely the Wireless Neurosensing System (WiNS), and for the first time, we evaluate multichannel recording capabilities in vivo. For a preliminary evaluation, we performed a benchtop experiment with emulated sinusoidal signals of varying amplitude and frequency, representative of neuronal activity. We later performed and analyzed electrocortical recordings in rats of evoked somatosensory activity in response to three paradigms: hind/fore limb and whisker stimulation. Wired recordings were used for comparison and validation of WiNS. We found that through the channel multiplexing element of WiNS, it is possible to perform multichannel recordings with a maximum sampling rate of ∼10 kHz for a total of eight channels. This sampling rate is appropriate for monitoring the full range of neuronal signals of interest, from low-frequency population recordings of electrocorticography and local field potentials to high-frequency individual neuronal spike recordings. These in vivo experiments demonstrated that the evoked neuronal activity recorded with WiNS is comparable to that recorded with a wired system under identical circumstances. Analysis of critical parameters for interpreting the somatosensory evoked activity showed no statistically significant difference between the parameters obtained by a wired system versus those obtained using WiNS. Therefore, WiNS can match the performance of more invasive recording systems. WiNS is a groundbreaking technology with potential applications throughout neuroscience as it offers a simple alternative to address the pitfalls of battery-powered neuronal implants.