• AAVS1 locus
• channelrhodopsin‐2
• forebrain organoids
• optogenetics

• National Research Foundation of Korea
• Samsung Science and Technology Foundation
• Samsung Electronics

• brain–computer interface
• electrode
• multimodal
• optogenetic

• Grant No.821RC531 Hainan Provincial Natural Science Foundation of China for High-level Talents
• 2022ZD0205201 STI2030-Major Projects
• No. T2122015 National Nature Science Foundation of China
• No.2019-I2M-5-014 CAMS Innovation Fund for Medical Sciences

• Cell therapy
• Demyelination
• Human brain
• Myelin
• Oligodendrocyte
• Oligodendrogenesis
• Remyelination
• Stroke
• iPS cells

• Humans
• Rats
• Adult
• Animals
• Induced Pluripotent Stem Cells
• Cell Differentiation/physiology
• Neurons
• Oligodendroglia/metabolism
• Axons/physiology
• Myelin Sheath/physiology

• Physical therapy
• aerobic exercise
• cell therapy
• neural stem cell
• neurorehabilitation
• stroke

• all-optical
• calcium imaging
• cell type specificity
• circuit dissection
• graft
• optogenetics
• spinal cord injury
• stroke

Neurogenesis is a key mechanism of brain development and plasticity, which is impaired in chronic neurodegeneration, including Parkinson’s disease. The accumulation of aberrant α-synuclein is one of the features of PD. Being secreted, this protein produces a prominent neurotoxic effect, alters synaptic plasticity, deregulates intercellular communication, and supports the development of neuroinflammation, thereby providing propagation of pathological events leading to the establishment of a PD-specific phenotype. Multidirectional and ambiguous effects of α-synuclein on adult neurogenesis suggest that impaired neurogenesis should be considered as a target for the prevention of cell loss and restoration of neurological functions. Thus, stimulation of endogenous neurogenesis or cell-replacement therapy with stem cell-derived differentiated neurons raises new hopes for the development of effective and safe technologies for treating PD neurodegeneration. Given the rapid development of optogenetics, it is not surprising that this method has already been repeatedly tested in manipulating neurogenesis in vivo and in vitro via targeting stem or progenitor cells. However, niche astrocytes could also serve as promising candidates for controlling neuronal differentiation and improving the functional integration of newly formed neurons within the brain tissue. In this review, we mainly focus on current approaches to assess neurogenesis and prospects in the application of optogenetic protocols to restore the neurogenesis in Parkinson’s disease.

• Parkinson′s disease
• astrocyte
• neural progenitor cell
• neural stem cell
• neurogenesis
• optogenetics
• α-synuclein

• animal models
• cartilage
• human induced pluripotent stem cells
• knee
• regeneration

• Adenovirus
• Hippocampus
• NRSF
• Organotypic
• REST

• ALS
• Amyotrophic lateral sclerosis
• Ca2+
• Cardiac muscle
• Cardiac pacemaker
• EC coupling
• ESC
• Microenvironment
• Myoblast
• Myocyte
• NSC
• Neural graft
• Neurogenesis
• Sarcomere
• Skeletal muscle
• Smooth muscle
• Spinal cord injury
• Stem cell
• T tubule
• iPSC

• Induced Pluripotent Stem Cells
• Muscle Cells
• Neural Stem Cells
• Neurons
• Optogenetics

• Channelrhodopsins
• Neural stem cell therapy
• Neurological disorders
• Optogenetics
• Transplant

The study of the pathomechanisms by which gene mutations lead to neurological diseases has benefit from several cellular and animal models. Recently, induced Pluripotent Stem Cell (iPSC) technologies have made possible the access to human neurons to study nervous system disease-related mechanisms, and are at the forefront of the research into neurological diseases. In this review, we will focalize upon genetic epilepsy, and summarize the most recent studies in which iPSC-based technologies were used to gain insight on the molecular bases of epilepsies. Moreover, we discuss the latest advancements in epilepsy cell modeling. At the two dimensional (2D) level, single-cell models of iPSC-derived neurons lead to a mature neuronal phenotype, and now allow a reliable investigation of synaptic transmission and plasticity. In addition, functional characterization of cerebral organoids enlightens neuronal network dynamics in a three-dimensional (3D) structure. Finally, we discuss the use of iPSCs as the cutting-edge technology for cell therapy in epilepsy.

• cerebral organoid
• disease modeling
• epilepsy
• induced pluripotent stem cells
• neuronal excitability
• transplantation

• Animals
• Cell- and Tissue-Based Therapy
• Epilepsy/genetics
• Epilepsy/therapy
• Humans
• Induced Pluripotent Stem Cells/cytology
• Mice
• Models, Biological
• Neural Stem Cells/cytology
• Organoids/cytology
• Single-Cell Analysis

Optogenetically engineered human neural progenitors (hNPs) are viewed as promising tools in regenerative neuroscience because they allow the testing of the ability of hNPs to integrate within nervous system of an appropriate host not only structurally, but also functionally based on the responses of their differentiated progenies to light. Here, we transduced H9 embryonic stem cell-derived hNPs with a lentivirus harboring human channelrhodopsin (hChR2) and differentiated them into a forebrain lineage. We extensively characterized the fate and optogenetic functionality of hChR2-hNPs in vitro with electrophysiology and immunocytochemistry. We also explored whether the in vivo phenotype of ChR2-hNPs conforms to in vitro observations by grafting them into the frontal neocortex of rodents and analyzing their survival and neuronal differentiation. Human ChR2-hNPs acquired neuronal phenotypes (TUJ1, MAP2, SMI-312, and synapsin 1 immunoreactivity) in vitro after an average of 70 days of coculturing with CD1 astrocytes and progressively displayed both inhibitory and excitatory neurotransmitter signatures by immunocytochemistry and whole-cell patch clamp recording. Three months after transplantation into motor cortex of naïve or injured mice, 60–70% of hChR2-hNPs at the transplantation site expressed TUJ1 and had neuronal cytologies, whereas 60% of cells also expressed ChR2. Transplant-derived neurons extended axons through major commissural and descending tracts and issued synaptophysin⁺ terminals in the claustrum, endopiriform area, and corresponding insular and piriform cortices. There was no apparent difference in engraftment, differentiation, or connectivity patterns between injured and sham subjects. Same trends were observed in a second rodent host, i.e. rat, where we employed longer survival times and found that the majority of grafted hChR2-hNPs differentiated into GABAergic neurons that established dense terminal fields and innervated mostly dendritic profiles in host cortical neurons. In physiological experiments, human ChR2⁺ neurons in culture generated spontaneous action potentials (APs) 100–170 days into differentiation and their firing activity was consistently driven by optical stimulation. Stimulation generated glutamatergic and GABAergic postsynaptic activity in neighboring ChR2^- cells, evidence that hChR2-hNP-derived neurons had established functional synaptic connections with other neurons in culture. Light stimulation of hChR2-hNP transplants in vivo generated complicated results, in part because of the variable response of the transplants themselves. Our findings show that we can successfully derive hNPs with optogenetic properties that are fully transferrable to their differentiated neuronal progenies. We also show that these progenies have substantial neurotransmitter plasticity in vitro, whereas in vivo they mostly differentiate into inhibitory GABAergic neurons. Furthermore, neurons derived from hNPs have the capacity of establishing functional synapses with postsynaptic neurons in vitro, but this outcome is technically challenging to explore in vivo. We propose that optogenetically endowed hNPs hold great promise as tools to explore de novo circuit formation in the brain and, in the future, perhaps launch a new generation of neuromodulatory therapies.

• Animals
• Astrocytes/cytology
• Astrocytes/radiation effects
• Axons/metabolism
• Axons/radiation effects
• Cell Differentiation/radiation effects
• Cell Lineage/radiation effects
• Cell Survival/radiation effects
• Channelrhodopsins/metabolism
• Human Embryonic Stem Cells/cytology
• Human Embryonic Stem Cells/radiation effects
• Humans
• Lentivirus/metabolism
• Light
• Mice, Nude
• Motor Cortex/metabolism
• Neural Stem Cells/cytology
• Neural Stem Cells/radiation effects
• Neuronal Plasticity/radiation effects
• Neurons/cytology
• Neurons/radiation effects
• Neurotransmitter Agents/metabolism
• Optogenetics
• Phenotype
• Photic Stimulation
• Rats, Nude
• Synaptic Transmission/radiation effects

• R01 DC006476 NIDCD NIH HHS
• R01 DC012957 NIDCD NIH HHS
• MSCRF TEDCO
• EMBO
• Hearing Health Foundation
• NIDCD
• The Cordelia Corporation, the John Mitchell, Jr. Trust, the David M. Rubenstein Fund for Hearing Research

• cell reprogramming
• cell therapy
• computational modeling
• disease modeling
• electrophysiology
• multielectrode arrays
• neural networks
• neuroengineering

• cerebral organoid
• human tissue
• optogenetics
• stem cell

• Huntington's disease
• Parkinson's disease
• neurodevelopmental diseases
• organoids
• synaptopathy

• Brain injuries
• High-throughput screening
• Lab-on-a-chip
• Neurodegenerative diseases
• Regenerative medicine
• Stem cells

• Basal ganglia
• Cell-based therapy
• Epilepsy
• GABA
• Interneuron
• Pentylenetetrazole
• Pharmacoresistance
• Seizures
• Substantia nigra
• Transplantation

• archaerhodopsin
• cell type specificity
• channelrhodopsin
• halorhodopsin
• intersectional genetics
• neuronal circuitry
• parvalbumin
• seizures

• R00 NS087110 NINDS NIH HHS
• R01 NS104071 NINDS NIH HHS
• R03 NS098015 NINDS NIH HHS
• T32 GM008471 NIGMS NIH HHS

Animal models of neurodevelopmental disorders have provided invaluable insights into the molecular-, cellular-, and circuit-level defects associated with a plethora of genetic disruptions. In many cases, these deficits have been linked to changes in disease-relevant behaviors, but very few of these findings have been translated to treatments for human disease. This may be due to significant species differences and the difficulty in modeling disorders that involve deletion or duplication of multiple genes. The identification of primary underlying pathophysiology in these models is confounded by the accumulation of secondary disease phenotypes in the mature nervous system, as well as potential compensatory mechanisms. The discovery of induced pluripotent stem cell technology now provides a tool to accurately model complex genetic neurogenetic disorders. Using this technique, patient-specific cell lines can be generated and differentiated into specific subtypes of neurons that can be used to identify primary cellular and molecular phenotypes. It is clear that impairments in synaptic structure and function are a common pathophysiology across neurodevelopmental disorders, and electrophysiological analysis at the earliest stages of neuronal development is critical for identifying changes in activity and excitability that can contribute to synaptic dysfunction and identify targets for disease-modifying therapies.

• autism spectrum disorders
• electrophysiology
• induced pluripotent stem cells
• neurodevelopmental disorders
• synaptic transmission

• Cerebral ischemia
• Embryonic neural stem/progenitor cell
• Excitatory transmission
• Maturation of neuronal excitability
• Organotypic hippocampal slice
• Stem cell differentiation

The capability of generating neural precursor cells with distinct types of regional identity in vitro has recently opened new opportunities for cell replacement in animal models of neurodegenerative diseases. By manipulating Wnt and BMP signaling, we steered the differentiation of mouse embryonic stem cells (ESCs) toward isocortical or hippocampal molecular identity. These two types of cells showed different degrees of axonal outgrowth and targeted different regions when co-transplanted in healthy or lesioned isocortex or in hippocampus. In hippocampus, only precursor cells with hippocampal molecular identity were able to extend projections, contacting CA3. Conversely, isocortical-like cells were capable of extending long-range axonal projections only when transplanted in motor cortex, sending fibers toward both intra- and extra-cortical targets. Ischemic damage induced by photothrombosis greatly enhanced the capability of isocortical-like cells to extend far-reaching projections. Our results indicate that neural precursors generated by ESCs carry intrinsic signals specifying axonal extension in different environments.

•

Wnt signaling induces hippocampal fate in neuralized mouse ESCs

• WNT signaling
• axonal extension
• axonal projection
• cell replacement
• hippocampus
• isocortex
• mouse embryonic stem cells
• neuronal identity
• stroke
• transplantation

• Animals
• Axons/physiology
• Cell Differentiation/physiology
• Cells, Cultured
• Hippocampus/physiology
• Mice
• Motor Cortex/physiology
• Mouse Embryonic Stem Cells/physiology
• Neocortex/physiology
• Neurogenesis/physiology
• Neurons/physiology
• Transplantation/methods

• Neural development
• Neural stem cells
• Neuronal diversity
• Pluripotent stem cells
• Single-cell analysis

The recognition of internal and external sources of stimuli, the self from non-self, seems to be an intrinsic property to the adequate functioning of the immune system and the nervous system, both complex network systems that have evolved to safeguard the self biological identity of the organism. The mammalian brain development relies on dynamic and adaptive processes that are now well described. However, the rules dictating this highly constrained developmental process remain elusive. Here we hypothesize that there is a cellular basis for brain selfhood, based on the analogy of the global mechanisms that drive the self/non-self recognition and instruction by the immune system. In utero education within the thymus by multi-step selection processes discard overly low and high affinity T-lymphocytes to self stimuli, thus avoiding expendable or autoreactive responses that might lead to harmful autoimmunity. We argue that the self principle is one of the chief determinants of neocortical brain neurogenesis. According to our hypothesis, early-life education on self at the subcortical plate of the neocortex by selection processes might participate in the striking specificity of neuronal repertoire and assure efficiency and self tolerance. Potential implications of this hypothesis in self-reactive neurological pathologies are discussed, particularly involving consciousness-associated pathophysiological conditions, i.e., epilepsy and schizophrenia, for which we coined the term autophrenity.

• cortical neuron diversity
• education
• neocortex
• programmed cell death
• self-tolerance
• thymus

• Stoppini
• brainstem
• engraftment
• integration
• interaction
• neural stem cells
• neuroprotection
• organotypic culture
• roller drum
• striatum
• transplantation

• Muscle
• Neural network
• Rehabilitation
• Reorganization
• Stroke

• functional integration
• stem cells
• stroke
• synapses
• transplantation

The capacity for induced pluripotent stem (iPS) cells to be differentiated into a wide range of neural cell types makes them an attractive donor source for autologous neural transplantation therapies aimed at brain repair. Translation to the in vivo setting has been difficult, however, with mixed results in a wide variety of preclinical models of brain injury and limited information on the basic in vivo properties of neural grafts generated from human iPS cells. Here we have generated a human iPS cell line constitutively expressing green fluorescent protein as a basis to identify and characterize grafts resulting from transplantation of neural progenitors into the adult rat brain. The results show that the grafts contain a mix of neural cell types, at various stages of differentiation, including neurons that establish extensive patterns of axonal growth and progressively develop functional properties over the course of 1 year after implantation. These findings form an important basis for the design and interpretation of preclinical studies using human stem cells for functional circuit re‐construction in animal models of brain injury. Stem Cells Translational Medicine2017;6:1547–1556

• Connectivity
• Electrophysiology
• Forebrain
• Grafting
• Regeneration

• clinical treatments
• closed-loop systems
• epilepsy
• microcircuits
• optogenetics

Optogenetics is one of the most powerful tools in neuroscience, allowing for selective control of specific neuronal populations in the brain of experimental animals, including mammals. We report, for the first time, the application of optogenetic tools to human brain tissue providing a proof-of-concept for the use of optogenetics in neuromodulation of human cortical and hippocampal neurons as a possible tool to explore network mechanisms and develop future therapeutic strategies.

Articular cartilage repair techniques are challenging. Human embryonic stem cells and induced pluripotent stem cells (iPSCs) theoretically provide an unlimited number of specialized cells which could be used in articular cartilage repair. However thus far chondrocytes from iPSCs have been created primarily by viral transfection and with the use of cocultured feeder cells. In addition chondrocytes derived from iPSCs have usually been formed in condensed cell bodies (resembling embryoid bodies) that then require dissolution with consequent substantial loss of cell viability and phenotype. All of these current techniques used to derive chondrocytes from iPSCs are problematic but solutions to these problems are on the horizon. These solutions will make iPSCs a viable alternative for articular cartilage repair in the near future.

• Induced pluripotent stem cells
• Articular cartilage
• Cartilage repair
• Stem cells

• Organotypic hippocampal slice cultures
• Stoke
• Traumatic brain injury

In order to understand and find therapeutic strategies for neurological disorders, disease models that recapitulate the connectivity and circuitry of patients’ brain are needed. Owing to many limitations of animal disease models, in vitro neuronal models using patient-derived stem cells are currently being developed. However, prior to employing neurons as a model in a dish, they need to be evaluated for their electrophysiological properties, including both passive and active membrane properties, dynamics of neurotransmitter release, and capacity to undergo synaptic plasticity. In this review, we survey recent attempts to study these issues in human induced pluripotent stem cell-derived neurons. Although progress has been made, there are still many hurdles to overcome before human induced pluripotent stem cell-derived neurons can fully recapitulate all of the above physiological properties of adult mature neurons. Moreover, proper integration of neurons into pre-existing circuitry still needs to be achieved. Nevertheless, in vitro neuronal stem cell-derived models hold great promise for clinical application in neurological diseases in the future.

• Cell replacement
• Embryonic stem
• Induced pluripotent
• Integration
• Regeneration
• Transplantation