Brain-Region-Specific Organoids Using Mini-bioreactors for Modeling ZIKV Exposure

Human iPSC-derived microglial cells protect neurons from neurodegeneration in long-term cultured adhesion brain organoids

Brain organoid models have greatly facilitated our understanding of human brain development and disease. However, key brain cell types, such as microglia, are lacking in most brain organoid models. Because microglia have been shown to play important roles in brain development and pathologies, attempts have been made to add microglia to brain organoids through co-culture. However, only short-term microglia-organoid co-cultures can be established, and it remains challenging to have long-lasting survival of microglia in organoids to mimic long-term residency of microglia in the brain. In this study, we developed an adhesion brain organoid (ABO) platform that allows prolonged culture of brain organoids (greater than a year). Moreover, the long-term (LT)-ABO system contains abundant astrocytes and can support prolonged survival and ramification of microglia. Furthermore, we showed that microglia in the LT-ABO could protect neurons from neurodegeneration by increasing synaptic density and reducing p-Tau level and cell death in the LT-ABO. Therefore, the microglia-containing LT-ABO platform generated in this study provides a promising human cellular model for studying neuron-glia and glia-glia interactions in brain development and the pathogenesis of neurodegenerative diseases such as Alzheimer's disease.

Modeling the Effect of Cannabinoid Exposure During Human Neurodevelopment Using Bidimensional and Tridimensional Cultures

Our knowledge about the consumption of cannabinoids during pregnancy lacks consistent evidence to determine whether it compromises neurodevelopment. Addressing this task is challenging and complex since pregnant women display multiple confounding factors that make it difficult to identify the real effect of cannabinoids' consumption. Recent studies shed light on this issue by using pluripotent stem cells of human origin, which can recapitulate human neurodevelopment. These revolutionary platforms allow studying how exogenous cannabinoids could alter human neurodevelopment without ethical concerns and confounding factors. Here, we review the information to date on the clinical studies about the impact of exogenous cannabinoid consumption on human brain development and how exogenous cannabinoids alter nervous system development in humans using cultured pluripotent stem cells as 2D and 3D platforms to recapitulate brain development.

Strategies to overcome the limitations of current organoid technology - engineered organoids

Organoids, as 3D in vitro models derived from stem cells, have unparalleled advantages over traditional cell and animal models for studying organogenesis, disease mechanisms, drug screening, and personalized diagnosis and treatment. Despite the tremendous progress made in organoid technology, the translational application of organoids still presents enormous challenges due to the complex structure and function of human organs. In this review, the limitations of the translational application of traditional organoid technologies are first described. Next, we explore ways to address many of the limitations of traditional organoid cultures by engineering various dimensions of organoid systems. Finally, we discuss future directions in the field, including potential roles in drug screening, simulated microphysiology system and personalized diagnosis and treatment. We hope that this review inspires future research into organoids and microphysiology system.

Advances in the Development and Application of Human Organoids: Techniques, Applications, and Future Perspectives

Organoids are three-dimensional (3D) cell cultures derived from human pluripotent stem cells or adult stem cells that recapitulate the cellular heterogeneity, structure, and function of human organs. These microstructures are invaluable for biomedical research due to their ability to closely mimic the complexity of native tissues while retaining human genetic material. This fidelity to native organ systems positions organoids as a powerful tool for advancing our understanding of human biology and for enhancing preclinical drug testing. Recent advancements have led to the successful development of a variety of organoid types, reflecting a broad range of human organs and tissues. This progress has expanded their application across several domains, including regenerative medicine, where organoids offer potential for tissue replacement and repair; disease modeling, which allows for the study of disease mechanisms and progression in a controlled environment; drug discovery and evaluation, where organoids provide a more accurate platform for testing drug efficacy and safety; and microecological research, where they contribute to understanding the interactions between microbes and host tissues. This review provides a comprehensive overview of the historical development of organoid technology, highlights the key achievements and ongoing challenges in the field, and discusses the current and emerging applications of organoids in both laboratory research and clinical practice.

Integrating 3D Bioprinting and Organoids to Better Recapitulate the Complexity of Cellular Microenvironments for Tissue Engineering

Organoids, with their capacity to mimic the structures and functions of human organs, have gained significant attention for simulating human pathophysiology and have been extensively investigated in the recent past. Additionally, 3D bioprinting, as an emerging bio-additive manufacturing technology, offers the potential for constructing heterogeneous cellular microenvironments, thereby promoting advancements in organoid research. In this review, the latest developments in 3D bioprinting technologies aimed at enhancing organoid engineering are introduced. The commonly used bioprinting methods and materials for organoids, with a particular emphasis on the potential advantages of combining 3D bioprinting with organoids are summarized. These advantages include achieving high cell concentrations to form large cellular aggregates, precise deposition of building blocks to create organoids with complex structures and functions, and automation and high throughput to ensure reproducibility and standardization in organoid culture. Furthermore, this review provides an overview of relevant studies from recent years and discusses the current limitations and prospects for future development.

Morphological diversification and functional maturation of human astrocytes in glia-enriched cortical organoid transplanted in mouse brain

Astrocytes, the most abundant glial cell type in the brain, are underrepresented in traditional cortical organoid models due to the delayed onset of cortical gliogenesis. Here we introduce a new glia-enriched cortical organoid model that exhibits accelerated astrogliogenesis. We demonstrated that induction of a gliogenic switch in a subset of progenitors enabled the rapid derivation of astroglial cells, which account for 25-31% of the cell population within 8-10 weeks of differentiation. Intracerebral transplantation of these organoids reliably generated a diverse repertoire of cortical neurons and anatomical subclasses of human astrocytes. Spatial transcriptome profiling identified layer-specific expression patterns among distinct subclasses of astrocytes within organoid transplants. Using an in vivo acute neuroinflammation model, we identified a subpopulation of astrocytes that rapidly activates pro-inflammatory pathways upon cytokine stimulation. Additionally, we demonstrated that CD38 signaling has a crucial role in mediating metabolic and mitochondrial stress in reactive astrocytes. This model provides a robust platform for investigating human astrocyte function.

Establishment of human cerebral organoid systems to model early neural development and assess the central neurotoxicity of environmental toxins

JOURNAL/nrgr/04.03/01300535-202501000-00032/figure1/v/2024-05-14T021156Z/r/image-tiff Human brain development is a complex process, and animal models often have significant limitations. To address this, researchers have developed pluripotent stem cell-derived three-dimensional structures, known as brain-like organoids, to more accurately model early human brain development and disease. To enable more consistent and intuitive reproduction of early brain development, in this study, we incorporated forebrain organoid culture technology into the traditional unguided method of brain organoid culture. This involved embedding organoids in matrigel for only 7 days during the rapid expansion phase of the neural epithelium and then removing them from the matrigel for further cultivation, resulting in a new type of human brain organoid system. This cerebral organoid system replicated the temporospatial characteristics of early human brain development, including neuroepithelium derivation, neural progenitor cell production and maintenance, neuron differentiation and migration, and cortical layer patterning and formation, providing more consistent and reproducible organoids for developmental modeling and toxicology testing. As a proof of concept, we applied the heavy metal cadmium to this newly improved organoid system to test whether it could be used to evaluate the neurotoxicity of environmental toxins. Brain organoids exposed to cadmium for 7 or 14 days manifested severe damage and abnormalities in their neurodevelopmental patterns, including bursts of cortical cell death and premature differentiation. Cadmium exposure caused progressive depletion of neural progenitor cells and loss of organoid integrity, accompanied by compensatory cell proliferation at ectopic locations. The convenience, flexibility, and controllability of this newly developed organoid platform make it a powerful and affordable alternative to animal models for use in neurodevelopmental, neurological, and neurotoxicological studies.

Time-Lapse Acquisition of Both Freely Secreted Proteome and Exosome Encapsulated Proteome in Live Organoids' Microenvironment

Proteomic communications in neighboring microenvironments during early organ development is a dynamic process that continuously reshapes human embryonic stem cells (hESCs) developmental fate. Such dynamic proteomic alteration in the microenvironment consists of both freely secreted proteome and exosome-encapsulated proteome. Simultaneous monitoring of the time-lapse shift of both proteomes with live organoids remains technically challenging. Here, a continuous organoid secretion/encapsulation proteome tandem LC-MS/MS (COSEP-LCM) is introduced, which permits time-lapse monitoring of proteomic alterations both in free secretion form and in exosome encapsulated form at live organoids' microenvironment. Continuous growth of human cerebral organoids (COs) and free-secretion/exosome-encapsulation proteomics acquisition with COSEP-LCM for 60 days is demonstrated. SERPINF1, F5, and EFNB1 are initially enriched inside exosomes as encapsulated excretion and then gradually enriched outside exosomes as freely secreted excretion, while C3 is initially enriched outside exosomes as freely secreted excretion and gradually enriched inside exosomes as encapsulated excretion. Such dynamic excretion pattern paradigm shift may imply critical developmental strategy evolution during early human cerebral development. COSEP-LCM offers a platform technique for continuous inside/outside exosome proteomics co-analysis in live organoids' microenvironment.

A multichannel microfluidic device for revealing the neurotoxic effects of Bisphenol S on cerebral organoids under low-dose constant exposure

Bisphenol S is a widely used plasticizer in manufacturing daily supplies, while little was known about its adverse effect on human health, especially on fetal brain development. Due to the complexity and subtlety of the brain, it remains challenging to reveal the hazardous effects of environmental pollution on human fetal brain development. Taking advantage of stem cell application, cerebral organoids generated from stem cells are becoming powerful tools for understanding brain development and drug toxicity testing models. Here, we developed a microfluidic chip for cerebral organoid culturing to reveal the neurotoxicity of low-dose constant BPS exposure on cerebral organoids. The organoids in our microfluidic system could be continuously cultured for 34 days and expressed all the essential properties of the cerebral organoids. Exposure to BPS was initiated from day 20 for concessive two weeks. The neurotoxic effects were evaluated by immunofluorescence staining and proteomics, and verified by quantitative real-time PCR. Our results indicated BPS exposure would inhibit neuron differentiation, hinder the Wnt signaling pathway, and cause alteration of signaling molecule expressions in brain regionalization. Even exposure to a low dose of BPS constantly might cause neurotoxicity during fetal brain development. Altogether, the multichannel microfluidic chip offers a general platform technique to reveal the effects of different hazardous chemicals on cerebral organoids.

Differential contributions of fetal mononuclear phagocytes to Zika virus neuroinvasion versus neuroprotection during congenital infection

Fetal immune cell functions during congenital infections are poorly understood. Zika virus (ZIKV) can vertically transmit from mother to fetus, causing nervous system infection and congenital ZIKV syndrome (CZS). We identified differential functional roles for fetal monocyte/macrophage cell types and microglia in ZIKV dissemination versus clearance using mouse models. Trafficking of ZIKV-infected primitive macrophages from the yolk sac allowed initial fetal virus inoculation, while recruited monocytes promoted non-productive neuroinflammation. Conversely, brain-resident differentiated microglia were protective, limiting infection and neuronal death. Single-cell RNA sequencing identified transcriptional profiles linked to the protective versus detrimental contributions of mononuclear phagocyte subsets. In human brain organoids, microglia also promoted neuroprotective transcriptional changes and infection clearance. Thus, microglia are protective before birth, contrasting with the disease-enhancing roles of primitive macrophages and monocytes. Differential modulation of myeloid cell phenotypes by genetically divergent ZIKVs underscores the potential of immune cells to regulate diverse outcomes during fetal infections.

Central nervous system vascularization in human embryos and neural organoids

In recent years, neural organoids derived from human pluripotent stem cells (hPSCs) have offered a transformative pre-clinical platform for understanding central nervous system (CNS) development, disease, drug effects, and toxicology. CNS vasculature plays an important role in all these scenarios; however, most published studies describe CNS organoids that lack a functional vasculature or demonstrate rudimentary incorporation of endothelial cells or blood vessel networks. Here, we review the existing knowledge of vascularization during the development of different CNS regions, including the brain, spinal cord, and retina, and compare it to vascularized CNS organoid models. We highlight several areas of contrast where further bioengineering innovation is needed and discuss potential applications of vascularized neural organoids in modeling human CNS development, physiology, and disease.

An Overview of Zika Virus and Zika Virus Induced Neuropathies

Flaviviruses pose a major public health concern across the globe. Among them, Zika virus (ZIKV) is an emerging and reemerging arthropod-borne flavivirus that has become a major international public health problem following multiple large outbreaks over the past two decades. The majority of infections caused by ZIKV exhibit mild symptoms. However, the virus has been found to be associated with a variety of congenital neural abnormalities, including microcephaly in children and Guillain-Barre syndrome in adults. The exact prediction of the potential of ZIKV transmission is still enigmatic and underlines the significance of routine detection of the virus in suspected areas. ZIKV transmission from mother to fetus (including fetal abnormalities), viral presence in immune-privileged areas, and sexual transmission demonstrate the challenges in understanding the factors governing viral persistence and pathogenesis. This review illustrates the transmission patterns, epidemiology, control strategies (through vaccines, antivirals, and vectors), oncolytic aspects, molecular insights into neuro-immunopathogenesis, and other neuropathies caused by ZIKV. Additionally, we summarize in vivo and in vitro models that could provide an important platform to study ZIKV pathogenesis and the underlying governing cellular and molecular mechanisms.

Human-Mouse Chimeric Brain Models to Study Human Glial-Neuronal and Macroglial-Microglial Interactions

Human-mouse chimeric brain models, generated by transplanting human induced pluripotent stem cell (hiPSC)-derived neural cells, are valuable for studying the development and function of human neural cells in vivo. Understanding glial-glial and glial-neuronal interactions is essential for unraveling the complexities of brain function and developing treatments for neurological disorders. To explore these interactions between human neural cells in vivo, we co-engrafted hiPSC-derived neural progenitor cells together with primitive macrophage progenitors into the neonatal mouse brain. This approach creates human-mouse chimeric brains containing human microglia, macroglia (astroglia and oligodendroglia), and neurons. Using super-resolution imaging and 3D reconstruction techniques, we examine the dynamics between human neurons and glia, and observe human microglia pruning synapses of human neurons, and often engulfing neurons themselves. Single-cell RNA sequencing analysis of the chimeric brain uncovers a close recapitulation of the human glial progenitor cell population, along with a dynamic stage in astroglial development that mirrors the processes found in the human brain. Furthermore, cell-cell communication analysis highlights significant neuronal-glial and macroglial-microglial interactions, especially the interaction between adhesion molecules neurexins and neuroligins between neurons and astroglia, emphasizing their key role in synaptogenesis. We also observed interactions between microglia and astroglia mediated by SPP1, crucial for promoting microglia growth and astrogliosis, and the PTN-MK pathways, instrumental in homeostatic maintenance and development in macroglial progenitors. This innovative co-transplantation model opens up new avenues for exploring the complex pathophysiological mechanisms underlying human neurological diseases. It holds particular promise for studying disorders where glial-neuronal interactions and non-cell-autonomous effects play crucial roles.

Assessment of the level of apoptosis in differentiated pseudo-neuronal cells derived from neural stem cells under the influence of various inducers

Development and maintenance of the nervous system are governed by a scheduled cell death mechanism known as apoptosis. Very much how neurons survive and function depends on the degree of death in differentiating pseudo-neuronal cells produced from neural stem cells. Different inducers can affect the degree of death in these cells: hormones, medicines, growth factors, and others. Developing inventive therapies for neurodegenerative illnesses depends on a knowledge of how these inducers impact mortality in differentiated pseudo-neuronal cells. Using flow cytometry, Western blotting, and fluorescence microscopy among other techniques, the degree of death in many pseudo-neuronal cells is evaluated. Flow cytometry generates dead cell counts from measurements of cell size, granularity, and DNA content. Whereas fluorescence microscopy visualizes dead cells using fluorescent dyes or antibodies, Western blotting detects caspases and Bcl-2 family proteins. This review attempts to offer a thorough investigation of present studies on death in differentiated pseudo-neuronal cells produced from neural stem cells under the effect of different inducers. Through investigating how these inducers influence death, the review aims to provide information that might direct the next studies and support treatment plans for neurodegenerative diseases. With an eye toward inducers like retinoic acid, selegiline, cytokines, valproic acid, and small compounds, we examined research to evaluate death rates. The findings offer important new perspectives on the molecular processes guiding death in these cells. There is still a complete lack of understanding of how different factors affect the molecular processes that lead to death, so understanding these processes can contribute to new therapeutic approaches to treat neurodegenerative diseases.

A human forebrain organoid model reveals the essential function of GTF2IRD1-TTR-ERK axis for the neurodevelopmental deficits of Williams syndrome

Williams syndrome (WS; OMIM#194050) is a rare disorder, which is caused by the microdeletion of one copy of 25-27 genes, and WS patients display diverse neuronal deficits. Although remarkable progresses have been achieved, the mechanisms for these distinct deficits are still largely unknown. Here, we have shown that neural progenitor cells (NPCs) in WS forebrain organoids display abnormal proliferation and differentiation capabilities, and synapse formation. Genes with altered expression are related to neuronal development and neurogenesis. Single cell RNA-seq (scRNA-seq) data analysis revealed 13 clusters in healthy control and WS organoids. WS organoids show an aberrant generation of excitatory neurons. Mechanistically, the expression of transthyretin (TTR) are remarkably decreased in WS forebrain organoids. We have found that GTF2IRD1 encoded by one WS associated gene GTF2IRD1 binds to TTR promoter regions and regulates the expression of TTR. In addition, exogenous TTR can activate ERK signaling and rescue neurogenic deficits of WS forebrain organoids. Gtf2ird1-deficient mice display similar neurodevelopmental deficits as observed in WS organoids. Collectively, our study reveals critical function of GTF2IRD1 in regulating neurodevelopment of WS forebrain organoids and mice through regulating TTR-ERK pathway.

Advances in human cellular mechanistic understanding and drug discovery of brain organoids for neurodegenerative diseases

The prevalence of neurodegenerative diseases (NDs) is increasing rapidly as the aging population accelerates, and there are still no treatments to halt or reverse the progression of these diseases. While traditional 2D cultures and animal models fail to translate into effective therapies benefit patients, 3D cultured human brain organoids (hBOs) facilitate the use of non-invasive methods to capture patient data. The purpose of this study was to review the research and application of hBO in disease models and drug screening in NDs. The pluripotent stem cells are induced in multiple stages to form cerebral organoids, brain region-specific organoids and their derived brain cells, which exhibit complex brain-like structures and perform electrophysiological activities. The brain region-specific organoids and their derived neurons or glial cells contribute to the understanding of the pathogenesis of NDs and the efficient development of drugs, including Alzheimer's disease, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Glial-rich brain organoids facilitate the study of glial function and neuroinflammation, including astrocytes, microglia, and oligodendrocytes. Further research on the maturation enhancement, vascularization and multi-organoid assembly of hBO will help to enhance the research and application of NDs cellular models.

Advances in, and prospects of, 3D preclinical models for skin drug discovery

The skin has an important role in regulating homeostasis and protecting the body from endogenous and exogenous microenvironments. Although 3D models for drug discovery have been extensively studied, there is a growing demand for more advanced 3D skin models to enhance skin research. The use of these advanced skin models holds promise across domains such as cosmetics, skin disease treatments, and toxicity testing of new therapeutics. Recent advances include the development of skin-on-a-chip, spheroids, reconstructed skin, organoids, and computational approaches, including quantitative structure-activity relationship (QSAR) and quantitative structure-property relationship (QSPR) research. These innovations are bridging the gap between traditional 2D and advanced 3D models, moving progress from research to clinical applications. In this review, we highlight in vitro and computational skin models with advanced drug discovery for skin-related applications.

Meta-analysis of single-cell RNA sequencing co-expression in human neural organoids reveals their high variability in recapitulating primary tissue

Human neural organoids offer an exciting opportunity for studying inaccessible human-specific brain development; however, it remains unclear how precisely organoids recapitulate fetal/primary tissue biology. We characterize field-wide replicability and biological fidelity through a meta-analysis of single-cell RNA-sequencing data for first and second trimester human primary brain (2.95 million cells, 51 data sets) and neural organoids (1.59 million cells, 173 data sets). We quantify the degree primary tissue cell type marker expression and co-expression are recapitulated in organoids across 10 different protocol types. By quantifying gene-level preservation of primary tissue co-expression, we show neural organoids lie on a spectrum ranging from virtually no signal to co-expression indistinguishable from primary tissue, demonstrating a high degree of variability in biological fidelity among organoid systems. Our preserved co-expression framework provides cell type-specific measures of fidelity applicable to diverse neural organoids, offering a powerful tool for uncovering unifying axes of variation across heterogeneous neural organoid experiments.

Pluripotent stem cell-derived organoids: A brief history of curiosity-led discoveries

Organoids are quickly becoming an accepted model for understanding human biology and disease. Pluripotent stem cells (PSC) provide a starting point for many organs and enable modeling of the embryonic development and maturation of such organs. The foundation of PSC-derived organoids can be found in elegant developmental studies demonstrating the remarkable ability of immature cells to undergo histogenesis even when taken out of the embryo context. PSC-organoids are an evolution of earlier methods such as embryoid bodies, taken to a new level with finer control and in some cases going beyond tissue histogenesis to organ-like morphogenesis. But many of the discoveries that led to organoids were not necessarily planned, but rather the result of inquisitive minds with freedom to explore. Protecting such curiosity-led research through flexible funding will be important going forward if we are to see further ground-breaking discoveries.

Host circuit engagement of human cortical organoids transplanted in rodents

Human neural organoids represent promising models for studying neural function; however, organoids grown in vitro lack certain microenvironments and sensory inputs that are thought to be essential for maturation. The transplantation of patient-derived neural organoids into animal hosts helps overcome some of these limitations and offers an approach for neural organoid maturation and circuit integration. Here, we describe a method for transplanting human stem cell-derived cortical organoids (hCOs) into the somatosensory cortex of newborn rats. The differentiation of human induced pluripotent stem cells into hCOs occurs over 30-60 days, and the transplantation procedure itself requires ~0.5-1 hours per animal. The use of neonatal hosts provides a developmentally appropriate stage for circuit integration and allows the generation and experimental manipulation of a unit of human neural tissue within the cortex of a living animal host. After transplantation, animals can be maintained for hundreds of days, and transplanted hCO growth can be monitored by using brain magnetic resonance imaging. We describe the assessment of human neural circuit function in vivo by monitoring genetically encoded calcium responses and extracellular activity. To demonstrate human neuron-host functional integration, we also describe a procedure for engaging host neural circuits and for modulating animal behavior by using an optogenetic behavioral training paradigm. The transplanted human neurons can then undergo ex vivo characterization across modalities including dendritic morphology reconstruction, single-nucleus transcriptomics, optogenetic manipulation and electrophysiology. This approach may enable the discovery of cellular phenotypes from patient-derived cells and uncover mechanisms that contribute to human brain evolution from previously inaccessible developmental stages.

Brain organoid models for studying the function of iPSC-derived microglia in neurodegeneration and brain tumours

Microglia represent the main resident immune cells of the brain. The interplay between microglia and other cells in the central nervous system, such as neurons or other glial cells, influences the function and ability of microglia to respond to various stimuli. These cellular communications, when disrupted, can affect the structure and function of the brain, and the initiation and progression of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease, as well as the progression of other brain diseases like glioblastoma. Due to the difficult access to patient brain tissue and the differences reported in the murine models, the available models to study the role of microglia in disease progression are limited. Pluripotent stem cell technology has facilitated the generation of highly complex models, allowing the study of control and patient-derived microglia in vitro. Moreover, the ability to generate brain organoids that can mimic the 3D tissue environment and intercellular interactions in the brain provide powerful tools to study cellular pathways under homeostatic conditions and various disease pathologies. In this review, we summarise the most recent developments in modelling degenerative diseases and glioblastoma, with a focus on brain organoids with integrated microglia. We provide an overview of the most relevant research on intercellular interactions of microglia to evaluate their potential to study brain pathologies.

Polarization of organoids by bioengineered symmetry breaking

Symmetry breaking leading to axis formation and spatial patterning is crucial for achieving more accurate recapitulation of human development in organoids. While these processes can occur spontaneously by self-organizing capabilities of pluripotent stem cells, they can often result in variation in structure and composition of cell types within organoids. To address this limitation, bioengineering techniques that utilize geometric, topological and stiffness factors are increasingly employed to enhance control and consistency. Here, we review how spontaneous manners and engineering tools such as micropattern, microfluidics, biomaterials, etc. can facilitate the process of symmetry breaking leading to germ layer patterning and the formation of anteroposterior and dorsoventral axes in blastoids, gastruloids, neuruloids and neural organoids. Furthermore, brain assembloids, which are composed of multiple brain regions through fusion processes are discussed. The overview of organoid polarization in terms of patterning tools can offer valuable insights for enhancing the physiological relevance of organoid system.

Interplay Between Zika Virus-Induced Autophagy and Neural Stem Cell Fate Determination

The Zika virus (ZIKV) outbreaks and its co-relation with microcephaly have become a global health concern. It is primarily transmitted by a mosquito, but can also be transmitted from an infected mother to her fetus causing impairment in brain development, leading to microcephaly. However, the underlying molecular mechanism of ZIKV-induced microcephaly is poorly understood. In this study, we explored the role of ZIKV non-structural protein NS4A and NS4B in ZIKV pathogenesis in a well-characterized primary culture of human fetal neural stem cells (fNSCs). We observed that the co-transfection of NS4A and NS4B altered the neural stem cell fate by arresting proliferation and inducing premature neurogenesis. NS4A + NS4B transfection in fNSCs increased autophagy and dysregulated notch signaling. Further, it also altered the regulation of downstream genes controlling cell proliferation. Additionally, we reported that 3 methyl-adenine (3-MA), a potent autophagy inhibitor, attenuated the deleterious effects of NS4A and NS4B as evidenced by the rescue in Notch1 expression, enhanced proliferation, and reduced premature neurogenesis. Our attempts to understand the mechanism of autophagy induction indicate the involvement of mitochondrial fission and ROS. Collectively, our findings highlight the novel role of NS4A and NS4B in mediating NSC fate alteration through autophagy-mediated notch degradation. The study also helps to advance our understanding of ZIKV-induced neuropathogenesis and suggests autophagy as a potential target for anti-ZIKV therapeutic intervention.

Human stem cell models to unravel brain cancer

Pre-clinical animal models of human brain tumors have been invaluable tools for studying cancer pathogenesis and exploring novel treatment modalities. Such models recapitulate important aspects of the human disease such as the stem-progenitor-differentiated cell hierarchy. Although powerful, we argue that animal models are inherently limited in their ability to phenocopy certain important aspects of human brain tumor biology. We specifically highlight the inability of mouse models to generate certain forms aggressive pediatric medulloblastoma likely owing to cellular, anatomic, and genetic differences between the human and mouse brains. Additionally, we review some limitations of human brain tumor derived cell lines and outline why they are a sub-optimal system for purposes of pre-clinical modeling. Below, we present the case for human stem cell-based models of brain tumors, focusing mainly on glioblastoma and medulloblastoma. Drawing on several recently published studies, we review the exciting progress that has been made towards modeling human brain tumors using two-dimensional adherent stem cell cultures and three-dimensional organoids. We identify the important advances arrived at using these human stem cell-based models and suggest opportunities for future work in this direction. In this review article, we aim to highlight the utility and promises of human stem cell-based models of brain tumors as a complementary system to traditional transgenic animal and cell line systems.

Advancing insights into virus-induced neurodevelopmental disorders through human brain organoid modelling

Human neurodevelopment is a complex process vulnerable to disruptions, particularly during the prenatal period. Maternal viral infections represent a significant environmental factor contributing to a spectrum of congenital defects with profound and enduring impacts on affected offspring. The advent of induced pluripotent stem cell (iPSC)-derived three-dimensional (3D) human brain organoids has revolutionised our ability to model prenatal viral infections and associated neurodevelopmental disorders. Notably, human brain organoids provide a distinct advantage over traditional animal models, whose brain structures and developmental processes differ markedly from those of humans. These organoids offer a sophisticated platform for investigating viral pathogenesis, infection mechanisms and potential therapeutic interventions, as demonstrated by their pivotal role during the 2016 Zika virus outbreak. This review critically examines the utilisation of brain organoids in elucidating the mechanisms of TORCH viral infections, their impact on human brain development and contribution to associated neurodevelopmental disorders.

Accelerated production of human epithelial organoids in a miniaturized spinning bioreactor

Conventional static culture of organoids necessitates weekly manual passaging and results in nonhomogeneous exposure of organoids to nutrients, oxygen, and toxic metabolites. Here, we developed a miniaturized spinning bioreactor, RPMotion, specifically optimized for accelerated and cost-effective culture of epithelial organoids under homogeneous conditions. We established tissue-specific RPMotion settings and standard operating protocols for the expansion of human epithelial organoids derived from the liver, intestine, and pancreas. All organoid types proliferated faster in the bioreactor (5.2-fold, 3-fold, and 4-fold, respectively) compared to static culture while keeping their organ-specific phenotypes. We confirmed that the bioreactor is suitable for organoid establishment directly from biopsies and for long-term expansion of liver organoids. Furthermore, we showed that after accelerated expansion, liver organoids can be differentiated into hepatocyte-like cells in the RPMotion bioreactor. In conclusion, this miniaturized bioreactor enables work-, time-, and cost-efficient organoid culture, holding great promise for organoid-based fundamental and translational research and development.

Human pluripotent stem cell-derived models of the hippocampus

The hippocampus is a crucial structure of the brain, recognised for its roles in the formation of memory, and our ability to navigate the world. Despite its importance, clear understanding of how the human hippocampus develops and its contribution to disease is limited due to the inaccessible nature of the human brain. In this regard, the advent of human pluripotent stem cell (hPSC) technologies has enabled the study of human biology in an unprecedented manner, through the ability to model development and disease as both 2D monolayers and 3D organoids. In this review, we explore the existing efforts to derive the hippocampal lineage from hPSCs and evaluate the various aspects of the in vivo hippocampus that are replicated in vitro. In addition, we highlight key diseases that have been modelled using hPSC-derived cultures and offer our perspective on future directions for this emerging field.

Exposure to the antiretroviral drug dolutegravir impairs structure and neurogenesis in a forebrain organoid model of human embryonic cortical development

Introduction

For many therapeutic drugs, including antiretroviral drugs used to treat people living with HIV-1 (PLWH), we have little data on the potential effects on the developing human brain due to limited access to tissue and historical constraints on the inclusion of pregnant populations in clinical trials. Human induced pluripotent stem cells (iPSCs) offer a new avenue to gain insight on how drugs may impact human cell types representative of the developing central nervous system. To prevent vertical transmission of HIV and promote the health of pregnant PLWH, antiretroviral therapy must be initiated and/or maintained throughout pregnancy. However, many antiretroviral drugs are approved for widespread use following clinical testing only in non-pregnant populations and there may be limited information on potential teratogenicity until pregnancy outcomes are evaluated. The integrase strand transfer inhibitor dolutegravir (DTG) is a frontline antiretroviral drug that is effective in viral suppression of HIV but was previously reported to be associated with a slight increase in the risk for neural tube defects in one study, although this has not been replicated in other cohorts.

Methods

To directly investigate the potential impact of DTG on human cortical neurogenesis, we measured the effects of daily drug exposure on the early stages of corticogenesis in a human iPSC-based forebrain organoid model. We quantified organoid size and structure and analyzed gene and protein expression to evaluate the impact of several doses of DTG on organoid development.

Results

We observed deficits in organoid structure and impaired neurogenesis in DTG-treated organoids compared to vehicle-treated control organoids after 20 or 40 days in culture. Our highest dose of DTG (10 μM) resulted in significantly smaller organoids with a reduced density of neural rosette structures compared to vehicle-treated controls. Mechanistically, RNA-sequencing and immunohistological analysis suggests dysregulated amino acid transport and activation of the integrated stress response in the DTG-treated organoids, and functionally, a small molecule integrated stress response inhibitor (ISRIB) could partially rescue increased expression of proteins related to cell cycle regulation.

Discussion

Together, these results illustrate the potential for human iPSC-based strategies to reveal biological processes during neurogenesis that may be affected by therapeutic drugs and provide complementary data in relevant human cell types to augment preclinical investigations of drug safety during pregnancy.

Organoids and organoid extracellular vesicles-based disease treatment strategies

Organoids are "mini-organs" that self-organize and differentiate from stem cells under in vitro 3D culture conditions, mimicking the spatial structure and function of tissues in vivo. Extracellular vesicles (EVs) are nanoscale phospholipid bilayer vesicles secreted by living cells, rich in bioactive molecules, with excellent biocompatibility and low immunogenicity. Compared to EVs, organoid-derived EVs (OEVs) exhibit higher yield and enhanced biological functions. Organoids possess stem cell characteristics, and OEVs are capable of delivering active substances, making both highly promising for medical applications. In this review, we provide an overview of the fundamental biological principles of organoids and OEVs, and discuss their current applications in disease treatment. We then focus on the differences between OEVs and traditional EVs. Subsequently, we present methods for the engineering modification of OEVs. Finally, we critically summarize the advantages and challenges of organoids and OEVs. In conclusion, we believe that a deeper understanding of organoids and OEVs will provide innovative solutions to complex diseases.

Antiviral immunity within neural stem cells distinguishes Enterovirus-D68 strain differences in forebrain organoids

Neural stem cells have intact innate immune responses that protect them from virus infection and cell death. Yet, viruses can antagonize such responses to establish neuropathogenesis. Using a forebrain organoid model system at two developmental time points, we identified that neural stem cells, in particular radial glia, are basally primed to respond to virus infection by upregulating several antiviral interferon-stimulated genes. Infection of these organoids with a neuropathogenic Enterovirus-D68 strain, demonstrated the ability of this virus to impede immune activation by blocking interferon responses. Together, our data highlight immune gene signatures present in different types of neural stem cells and differential viral capacity to block neural-specific immune induction.

Low-intensity ultrasound ameliorates brain organoid integration and rescues microcephaly deficits

Human brain organoids represent a remarkable platform for modelling neurological disorders and a promising brain repair approach. However, the effects of physical stimulation on their development and integration remain unclear. Here, we report that low-intensity ultrasound significantly increases neural progenitor cell proliferation and neuronal maturation in cortical organoids. Histological assays and single-cell gene expression analyses revealed that low-intensity ultrasound improves the neural development in cortical organoids. Following organoid grafts transplantation into the injured somatosensory cortices of adult mice, longitudinal electrophysiological recordings and histological assays revealed that ultrasound-treated organoid grafts undergo advanced maturation. They also exhibit enhanced pain-related gamma-band activity and more disseminated projections into the host brain than the untreated groups. Finally, low-intensity ultrasound ameliorates neuropathological deficits in a microcephaly brain organoid model. Hence, low-intensity ultrasound stimulation advances the development and integration of brain organoids, providing a strategy for treating neurodevelopmental disorders and repairing cortical damage.

Human brain organoid: trends, evolution, and remaining challenges

Advanced brain organoids provide promising platforms for deciphering the cellular and molecular processes of human neural development and diseases. Although various studies and reviews have described developments and advancements in brain organoids, few studies have comprehensively summarized and analyzed the global trends in this area of neuroscience. To identify and further facilitate the development of cerebral organoids, we utilized bibliometrics and visualization methods to analyze the global trends and evolution of brain organoids in the last 10 years. First, annual publications, countries/regions, organizations, journals, authors, co-citations, and keywords relating to brain organoids were identified. The hotspots in this field were also systematically identified. Subsequently, current applications for brain organoids in neuroscience, including human neural development, neural disorders, infectious diseases, regenerative medicine, drug discovery, and toxicity assessment studies, are comprehensively discussed. Towards that end, several considerations regarding the current challenges in brain organoid research and future strategies to advance neuroscience will be presented to further promote their application in neurological research.

Generation and characterization of cortical organoids from iPSC-derived dental pulp stem cells using traditional and innovative approaches

Cortical organoids derived from human induced pluripotent stem cells (hiPSCs) represent a powerful in vitro experimental system to investigate human brain development and disease, often inaccessible to direct experimentation. However, despite steady progress in organoid technology, several limitations remain, including high cost and variability, use of hiPSCs derived from tissues harvested invasively, unexplored three-dimensional (3D) structural features and neuronal connectivity. Here, using a cost-effective and reproducible protocol as well as conventional two-dimensional (2D) immunostaining, we show that cortical organoids generated from hiPSCs obtained by reprogramming stem cells from human exfoliated deciduous teeth (SHED) recapitulate key aspects of human corticogenesis, such as polarized organization of neural progenitor zones with the presence of outer radial glial stem cells, and differentiation of superficial- and deep-layer cortical neurons and glial cells. We also show that 3D bioprinting and magnetic resonance imaging of intact cortical organoids are alternative and complementary approaches to unravel critical features of the 3D architecture of organoids. Finally, extracellular electrical recordings in whole organoids showed functional neuronal networks. Together, our findings suggest that SHED-derived cortical organoids constitute an attractive model of human neurodevelopment, and support the notion that a combination of 2D and 3D techniques to analyze organoid structure and function may help improve this promising technology.

AAVS1-targeted, stable expression of ChR2 in human brain organoids for consistent optogenetic control

Self-organizing brain organoids provide a promising tool for studying human development and disease. Here we created human forebrain organoids with stable and homogeneous expression of channelrhodopsin-2 (ChR2) by generating AAVS1 safe harbor locus-targeted, ChR2 knocked-in human pluripotent stem cells (hPSCs), followed by the differentiation of these genetically engineered hPSCs into forebrain organoids. The resulting ChR2-expressing human forebrain organoids showed homogeneous cellular expression of ChR2 throughout entire regions without any structural and functional perturbations and displayed consistent and robust neural activation upon light stimulation, allowing for the non-virus mediated, spatiotemporal optogenetic control of neural activities. Furthermore, in the hybrid platform in which brain organoids are connected with spinal cord organoids and skeletal muscle spheroids, ChR2 knocked-in forebrain organoids induced strong and consistent muscle contraction upon brain-specific optogenetic stimulation. Our study thus provides a novel, non-virus mediated, preclinical human organoid system for light-inducible, consistent control of neural activities to study neural circuits and dynamics in normal and disease-specific human brains as well as neural connections between brain and other peripheral tissues.

Modeling common and rare genetic risk factors of neuropsychiatric disorders in human induced pluripotent stem cells

Recent genome-wide association studies (GWAS) and whole-exome sequencing of neuropsychiatric disorders, especially schizophrenia, have identified a plethora of common and rare disease risk variants/genes. Translating the mounting human genetic discoveries into novel disease biology and more tailored clinical treatments is tied to our ability to causally connect genetic risk variants to molecular and cellular phenotypes. When combined with the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) nuclease-mediated genome editing system, human induced pluripotent stem cell (hiPSC)-derived neural cultures (both 2D and 3D organoids) provide a promising tractable cellular model for bridging the gap between genetic findings and disease biology. In this review, we first conceptualize the advances in understanding the disease polygenicity and convergence from the past decade of iPSC modeling of different types of genetic risk factors of neuropsychiatric disorders. We then discuss the major cell types and cellular phenotypes that are most relevant to neuropsychiatric disorders in iPSC modeling. Finally, we critically review the limitations of iPSC modeling of neuropsychiatric disorders and outline the need for implementing and developing novel methods to scale up the number of iPSC lines and disease risk variants in a systematic manner. Sufficiently scaled-up iPSC modeling and a better functional interpretation of genetic risk variants, in combination with cutting-edge CRISPR/Cas9 gene editing and single-cell multi-omics methods, will enable the field to identify the specific and convergent molecular and cellular phenotypes in precision for neuropsychiatric disorders.

FGF8-mediated gene regulation affects regional identity in human cerebral organoids

The morphogen FGF8 establishes graded positional cues imparting regional cellular responses via modulation of early target genes. The roles of FGF signaling and its effector genes remain poorly characterized in human experimental models mimicking early fetal telencephalic development. We used hiPSC-derived cerebral organoids as an in vitro platform to investigate the effect of FGF8 signaling on neural identity and differentiation. We found that FGF8 treatment increases cellular heterogeneity, leading to distinct telencephalic and mesencephalic-like domains that co-develop in multi-regional organoids. Within telencephalic regions, FGF8 affects the anteroposterior and dorsoventral identity of neural progenitors and the balance between GABAergic and glutamatergic neurons, thus impacting spontaneous neuronal network activity. Moreover, FGF8 efficiently modulates key regulators responsible for several human neurodevelopmental disorders. Overall, our results show that FGF8 signaling is directly involved in both regional patterning and cellular diversity in human cerebral organoids and in modulating genes associated with normal and pathological neural development.

An evaluation of recent advancements in biological sensory organ-inspired neuromorphically tuned biomimetic devices

In the field of neuroscience, significant progress has been made regarding how the brain processes information. Unlike computer processors, the brain comprises neurons and synapses instead of memory blocks and transistors. Despite advancements in artificial neural networks, a complete understanding concerning brain functions remains elusive. For example, to achieve more accurate neuron replication, we must better understand signal transmission during synaptic processes, neural network tunability, and the creation of nanodevices featuring neurons and synapses. This study discusses the latest algorithms utilized in neuromorphic systems, the production of synaptic devices, differences between single and multisensory gadgets, recent advances in multisensory devices, and the promising research opportunities available in this field. We also explored the ability of an artificial synaptic device to mimic biological neural systems across diverse applications. Despite existing challenges, neuroscience-based computing technology holds promise for attracting scientists seeking to enhance solutions and augment the capabilities of neuromorphic devices, thereby fostering future breakthroughs in algorithms and the widespread application of cutting-edge technologies.

Dynamic culture of cerebral organoids using a pillar/perfusion plate for the assessment of developmental neurotoxicity

Despite the potential toxicity of commercial chemicals to the development of the nervous system (known as developmental neurotoxicity or DNT), conventionalin vitrocell models have primarily been employed for the assessment of acute neuronal toxicity. On the other hand, animal models used for the assessment of DNT are not physiologically relevant due to the heterogenic difference between humans and animals. In addition, animal models are low-throughput, time-consuming, expensive, and ethically questionable. Recently, human brain organoids have emerged as a promising alternative to assess the detrimental effects of chemicals on the developing brain. However, conventional organoid culture systems have several technical limitations including low throughput, lack of reproducibility, insufficient maturity of organoids, and the formation of the necrotic core due to limited diffusion of nutrients and oxygen. To address these issues and establish predictive DNT models, cerebral organoids were differentiated in a dynamic condition in a unique pillar/perfusion plate, which were exposed to test compounds to evaluate DNT potential. The pillar/perfusion plate facilitated uniform, dynamic culture of cerebral organoids with improved proliferation and maturity by rapid, bidirectional flow generated on a digital rocker. Day 9 cerebral organoids in the pillar/perfusion plate were exposed to ascorbic acid (DNT negative) and methylmercury (DNT positive) in a dynamic condition for 1 and 3 weeks, and changes in organoid morphology and neural gene expression were measured to determine DNT potential. As expected, ascorbic acid did not induce any changes in organoid morphology and neural gene expression. However, exposure of day 9 cerebral organoids to methylmercury resulted in significant changes in organoid morphology and neural gene expression. Interestingly, methylmercury did not induce adverse changes in cerebral organoids in a static condition, thus highlighting the importance of dynamic organoid culture in DNT assessment.

Neuronal lineage tracing from progenitors in human cortical organoids reveals mechanisms of neuronal production, diversity, and disease

The contribution of progenitor subtypes to generating the billions of neurons produced during human cortical neurogenesis is not well understood. We developed the cortical organoid lineage-tracing (COR-LT) system for human cortical organoids. Differential fluorescent reporter activation in distinct progenitor cells leads to permanent reporter expression, enabling the progenitor cell lineage of neurons to be determined. Surprisingly, nearly all excitatory neurons produced in cortical organoids were generated indirectly from intermediate progenitor cells. Additionally, neurons of different progenitor lineages were transcriptionally distinct. Isogenic lines made from an autistic individual with and without a likely pathogenic CTNNB1 variant demonstrated that the variant substantially altered the proportion of neurons derived from specific progenitor cell lineages, as well as the lineage-specific transcriptional profiles of these neurons, suggesting a pathogenic mechanism for this mutation. These results suggest individual progenitor subtypes play roles in generating the diverse neurons of the human cerebral cortex.

Human midbrain organoids: a powerful tool for advanced Parkinson's disease modeling and therapy exploration

Parkinson's disease (PD) is a neurodegenerative disorder marked by the loss of dopaminergic neurons in the substantia nigra. Despite progress, the pathogenesis remains unclear. Human midbrain organoids (hMLOs) have emerged as a promising model for studying PD, drug screening, and potential treatments. This review discusses the development of hMLOs, their application in PD research, and current challenges in organoid construction, highlighting possible optimization strategies.

Microglia regulate GABAergic neurogenesis in prenatal human brain through IGF1

GABAergic neurons are an essential cellular component of neural circuits. Their abundance and diversity have enlarged significantly in the human brain, contributing to the expanded cognitive capacity of humans. However, the developmental mechanism of the extended production of GABAergic neurons in the human brain remains elusive. Here, we use single-cell transcriptomics, bioinformatics, and histological analyses to uncover microglial regulation of the sustained proliferation of GABAergic progenitors and neuroblasts in the human medial ganglionic eminence (hMGE). We show that insulin-like growth factor 1 (IGF1) and its receptor IGR1R as the top ligand-receptor pair underlying microglia-progenitor communication in the prenatal human brain. Using our newly developed neuroimmune hMGE organoids, which mimics hMGE cytoarchitecture and developmental trajectory, we demonstrate that microglia-derived IGF1 promotes progenitor proliferation and the production of GABAergic neurons. Conversely, IGF1-neutralizing antibodies and IGF1 knockout human embryonic stem cells (hESC)-induced microglia (iMG) completely abolished iMG-mediated progenitor proliferation. Together, these findings reveal a previously unappreciated role of microglia-derived IGF1 in promoting proliferation of neural progenitors and the development of GABAergic neurons.

ZMYND11 Functions in Bimodal Regulation of Latent Genes and Brain-like Splicing to Safeguard Corticogenesis

Despite the litany of pathogenic variants linked to neurodevelopmental disorders (NDD) including autism (ASD) and intellectual disability 1,2 , our understanding of the underlying mechanisms caused by risk genes remain unclear. Here, we leveraged a human pluripotent stem cell model to uncover the neurodevelopmental consequences of mutations in ZMYND11 , a newly implicated risk gene 3,4 . ZMYND11, known for its tumor suppressor function, encodes a histone-reader that recognizes sites of transcriptional elongation and acts as a co-repressor 5,6 . Our findings reveal that ZMYND11-deficient cortical neural stem cells showed upregulation of latent developmental pathways, impairing progenitor and neuron production. In addition to its role on histones, ZMYND11 controls a brain-specific isoform switch involving the splicing regulator RBFOX2. Extending our findings to other chromatin-related ASD risk factors revealed similar developmental pathway activation and splicing dysregulation, partially rescuable through ZMYND11's regulatory functions.

Engineering human midbrain organoid microphysiological systems to model prenatal PFOS exposure

Perfluorooctane sulfonate (PFOS), a class of synthetic chemicals detected in various environmental compartments, has been associated with dysfunctions of the human central nervous system (CNS). However, the underlying neurotoxicology of PFOS exposure is largely understudied due to the lack of relevant human models. Here, we report bioengineered human midbrain organoid microphysiological systems (hMO-MPSs) to recapitulate the response of a fetal human brain to multiple concurrent PFOS exposure conditions. Each hMO-MPS consists of an hMO on a fully 3D printed holder device with a perfusable organoid adhesion layer for enhancing air-liquid interface culturing. Leveraging the unique, simply-fabricated holder devices, hMO-MPSs are scalable, easy to use, and compatible with conventional well-plates, and allow easy transfer onto a multiple-electrode array (MEA) system for plug-and-play measurement of neural activity. Interestingly, the neural activity of hMO-MPSs initially increased and subsequently decreased by exposure to a concentration range of 0, 30, 100, to 300 μM of PFOS. Furthermore, PFOS exposure impaired neural development and promoted neuroinflammation in the engineered hMO-MPSs. Along with PFOS, our platform is broadly applicable for studies toxicology of various other environmental pollutants.

Nanoplastics exposure-induced mitochondrial dysfunction contributes to disrupted stem cell differentiation in human cerebral organoids

Nanoplastics are ubiquitous in our daily lives, raising concerns about their potential impact on the human brain. Many studies reported that nanoplastics permeate the blood-brain barrier and influence cellular processes in mouse models. However, the neurotoxic effects of ingesting nanoplastics on human brain remain poorly understood. Here, we treated cerebral organoids with polystyrene nanoplastics to model the effects of nanoplastic exposure on human brain. Importantly, we found that mitochondria might be the significant organelles affected by polystyrene nanoplastics using immunostaing and RNA-seq analysis. Subsequently, we observed the increased cell death and decreased cell differentiation in our cerebral organoids. In conclusion, our findings shed insights on the mechanisms underlying the toxicity of nanoplastics on human brain organoids, providing an evaluation system in detection potential environmental toxicity on human brain.

Integrative analysis of molecular pathways and morphological anomalies associated with congenital Zika syndrome

Congenital Zika syndrome (CZS) comprises a set of clinical manifestations that can be presented by neonates born to mothers infected by the Zika virus (ZIKV). CZS-associated phenotypes include neurological, skeletal, and systemic alterations and long-term developmental sequelae. One of the most frequently reported clinical conditions is microcephaly characterized by a reduction in head circumference and cognitive complications. Nevertheless, the associations among the diverse signaling pathways underlying CZS phenotypes remain to be elucidated. To shed light on CZS, we have extensively reviewed the morphological anomalies resulting from ZIKV infection, as well as genes and proteins of interest obtained from the published literature. With this list of genes or proteins, we performed computational analyses to explore the cellular processes, molecular mechanisms, and molecular pathways related to ZIKV infection. Therefore, in this review, we comprehensively describe the morphological abnormalities caused by congenital ZIKV infection and, through the analysis noted above, propose common molecular pathways altered by ZIKV that could explain both central nervous system and craniofacial skeletal alterations.

Progress and potential of brain organoids in epilepsy research

Epilepsies are disorders of the brain characterised by an imbalance in electrical activity, linked to a disruption in the excitation and inhibition of neurons. Progress in the epilepsy research field has been hindered by the lack of an appropriate model, with traditionally used 2D primary cell culture assays and animal models having a number of limitations which inhibit their ability to recapitulate the developing brain and the mechanisms behind epileptogenesis. As a result, the mechanisms behind the pathogenesis of epilepsy are largely unknown. Brain organoids are 3D aggregates of neural tissue formed in vitro and have been shown to recapitulate the gene expression patterns of the brain during development, and can successfully model a range of epilepsies and drug responses. They thus present themselves as a novel tool to advance studies into epileptogenesis. In this review, we discuss the formation of brain organoids, their recent application in studying genetic epilepsies, hyperexcitability dynamics and oxygen glucose deprivation as a hyperexcitability agent, their use as an epilepsy drug testing and development platform, as well as the limitations of their use in epilepsy research and how these can be mitigated.

Organoid intelligence for developmental neurotoxicity testing

The increasing prevalence of neurodevelopmental disorders has highlighted the need for improved testing methods to determine developmental neurotoxicity (DNT) hazard for thousands of chemicals. This paper proposes the integration of organoid intelligence (OI); leveraging brain organoids to study neuroplasticity in vitro, into the DNT testing paradigm. OI brings a new approach to measure the impacts of xenobiotics on plasticity mechanisms - a critical biological process that is not adequately covered in current DNT in vitro assays. Finally, the integration of artificial intelligence (AI) techniques will further facilitate the analysis of complex brain organoid data to study these plasticity mechanisms.

Cannabinoids and Genetic Epilepsy Models: A Review with Focus on CDKL5 Deficiency Disorder

Pediatric genetic epilepsies, such as CDKL5 Deficiency Disorder (CDD), are severely debilitating, with early-onset seizures occurring more than ten times daily in extreme cases. Existing antiseizure drugs frequently prove ineffective, which significantly impacts child development and diminishes the quality of life for patients and caregivers. The relaxation of cannabis legislation has increased research into potential therapeutic properties of phytocannabinoids such as cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC). CBD's antiseizure properties have shown promise, particularly in treating drug-resistant genetic epilepsies associated with Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS), and Tuberous Sclerosis Complex (TSC). However, specific research on CDD remains limited. Much of the current evidence relies on anecdotal reports of artisanal products lacking accurate data on cannabinoid composition. Utilizing model systems like patient-derived iPSC neurons and brain organoids allows precise dosing and comprehensive exploration of cannabinoids' pharmacodynamics. This review explores the potential of CBD, THC, and other trace cannabinoids in treating CDD and focusing on clinical trials and preclinical models to elucidate the cannabinoid's potential mechanisms of action in disrupted CDD pathways and strengthen the case for further research into their potential as anti-epileptic drugs for CDD. This review offers an updated perspective on cannabinoid's therapeutic potential for CDD.

Generation of human region-specific brain organoids with medullary spinal trigeminal nuclei

Brain organoids with nucleus-specific identities provide unique platforms for studying human brain development and diseases at a finer resolution. Despite its essential role in vital body functions, the medulla of the hindbrain has seen a lack of in vitro models, let alone models resembling specific medullary nuclei, including the crucial spinal trigeminal nucleus (SpV) that relays peripheral sensory signals to the thalamus. Here, we report a method to differentiate human pluripotent stem cells into region-specific brain organoids resembling the dorsal domain of the medullary hindbrain. Importantly, organoids specifically recapitulated the development of the SpV derived from the dorsal medulla. We also developed an organoid system to create the trigeminothalamic projections between the SpV and the thalamus by fusing these organoids, namely human medullary SpV-like organoids (hmSpVOs), with organoids representing the thalamus (hThOs). Our study provides a platform for understanding SpV development, nucleus-based circuit organization, and related disorders in the human brain.