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Human iPSC-Derived Brain Cells, Organoids, and Organoids-on-Chips: Advancing Neurological Disease Modeling to Improve Clinical Outcome.
Neurological disorders are the leading cause of overall disease and disability worldwide, affecting more than 3.4 billion people globally and over 180 million Americans. Yet there are no curative treatments available for any of the cardinal neurological diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) and Huntington's disease (HD). Many compounds that demonstrate excellent activity in preclinical models fail in clinical trials. The most compelling reason for this failure is attributed to inherent limitations of rodent models that fail to replicate complex human biology. The transformation of patient-derived somatic cells into induced pluripotent stem cells (iPSCs) that can become functional human neurons is an emerging technology that is expected to revolutionize medical treatments and personal medicine. Here, we review the available evidence for the efficacy of iPSC-derived neurons, organoids, assembloids and organ-on-chip in models of AD, PD, ALS-FTD and HD. We focus on how these human-relevant iPSC-derived brain cells are crucial for understanding neurological disease pathogenesis and accelerating drug discovery. We also discuss the current limitations of this technology and how alternative models such as induced neurons (iNs) are generated by directly reprogramming fibroblasts that preserve age-associated epigenetic signatures and may serve as better models for neurological disorders.
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Ultrastructural changes in the central nervous system in experimental hypoglycemia.
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On the structure of coated vesicles.
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Long-Term Survival and Maturation of Transplanted Cerebral Organoids Derived from Human Induced Pluripotent Stem Cells.
Human cerebral organoids have emerged as a promising new therapeutic strategy for cell transplantation after brain injury. Researchers have explored the short-term survival and maturation of human cerebral organoids derived from human embryonic stem cells (hESCs) in animal models. However, the long-term survival and maturation of cerebral organoids derived from human induced pluripotent stem cells (hiPSCs) have not been studied in depth. In this study, we generated cerebral organoids from hiPSCs in a feeder-free culture system. Then, the cerebral organoids were digested into small clusters and transplanted into the frontal cerebral cortex of postnatal day 0 (P0) SCID mice. The long-term survival and maturation of the grafted cerebral organoids were evaluated at 12 months post-transplantation. Our results indicate that grafted cerebral organoids survive well and maintain their forebrain identity in vivo over a long period. The transplanted cerebral organoids showed reduced proliferative capacity, indicating a low risk of tumor formation. The majority of transplanted cells differentiated into cortical neuronal subtypes in different cortical layers in anatomical lamination at 12 months post-transplantation. In addition, a small population of grafted cerebral organoids matured into GABAergic neurons and gliocytes, including astrocytes, microglia and oligodendrocytes. Furthermore, the grafts formed synapses with the host cells and achieved vascularization in the host brain. Our study demonstrates the long-term survival and maturation of cerebral organoids derived from hiPSCs in vivo and provides evidence for the feasibility of cerebral organoids derived from hiPSCs as a potential cell transplantation therapy.
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Soman induces endoplasmic reticulum stress and apoptosis of cerebral organoids via the GRP78-ATF6-CHOP signaling pathway.
Soman is an organophosphorus compound that induces neurotoxicity. In addition to its direct toxic effects resulting from acetylcholine accumulation, neurotoxicity may also be exacerbated by inducing endoplasmic reticulum (ER) stress. In light of the current scarcity of appropriate in vitro assessment models, in the present study, we used cerebral organoids derived from human pluripotent stem cells, a new tool for investigating the mechanisms of neurotoxicity, to investigate soman-induced ER stress. The results demonstrated that soman significantly suppressed acetylcholinesterase activity and activated the GRP78-ATF6-CHOP (i.e. glucose-regulated protein 78-activating transcription factor 6-C/EBP homologous protein) ER stress cascade, driving apoptosis in cerebral organoids. Pharmacological inhibition of ER stress by pre-treating cerebral organoids with the ER stress inhibitor 4-phenylbutyric acid prior to soman exposure attenuated apoptotic signaling and downregulated GRP78, ATF6 and CHOP expression. Parallel in vivo validation utilized a rat model with subcutaneous soman exposure, focusing on hippocampal and striatal ER stress markers. Consistent with the in vitro findings, soman-exposed rats exhibited marked ER stress activation in brain regions critical for neurotoxicity. This study establishes ER stress as a key contributor to soman-induced neurotoxicity and highlights cerebral organoids as a physiologically relevant model for organophosphorus compound research. We propose ER stress modulation as a potential therapeutic strategy to mitigate neurotoxic outcomes.
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Generation of Human Brain Organoids for Mitochondrial Disease Modeling.
Mitochondrial diseases represent the largest class of inborn errors of metabolism and are currently incurable. These diseases cause neurodevelopmental defects whose underlying mechanisms remain to be elucidated. A major roadblock is the lack of effective models recapitulating the early-onset neuronal impairment seen in the patients. Advances in the technology of induced pluripotent stem cells (iPSCs) enable the generation of three-dimensional (3D) brain organoids that can be used to investigate the impact of diseases on the development and organization of the nervous system. Researchers, including these authors, have recently introduced human brain organoids to model mitochondrial disorders. This paper reports a detailed protocol for the robust generation of human iPSC-derived brain organoids and their use in mitochondrial bioenergetic profiling and imaging analyses. These experiments will allow the use of brain organoids to investigate metabolic and developmental dysfunctions and may provide crucial information to dissect the neuronal pathology of mitochondrial diseases.
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Specification of positional identity in forebrain organoids.
Human brain organoids generated with current technologies recapitulate histological features of the human brain, but they lack a reproducible topographic organization. During development, spatial topography is determined by gradients of signaling molecules released from discrete signaling centers. We hypothesized that introduction of a signaling center into forebrain organoids would specify the positional identity of neural tissue in a distance-dependent manner. Here, we present a system to trigger a Sonic Hedgehog (SHH) protein gradient in developing forebrain organoids that enables ordered self-organization along dorso-ventral and antero-posterior positional axes. SHH-patterned forebrain organoids establish major forebrain subdivisions that are positioned with in vivo-like topography. Consistent with its behavior in vivo, SHH exhibits long-range signaling activity in organoids. Finally, we use SHH-patterned cerebral organoids as a tool to study the role of cholesterol metabolism in SHH signaling. Together, this work identifies inductive signaling as an effective organizing strategy to recapitulate in vivo-like topography in human brain organoids.
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Generation of Standardized and Reproducible Forebrain-type Cerebral Organoids from Human Induced Pluripotent Stem Cells.
The human cortex is highly expanded and exhibits a complex structure with specific functional areas, providing higher brain function, such as cognition. Efforts to study human cerebral cortex development have been limited by the availability of model systems. Translating results from rodent studies to the human system is restricted by species differences and studies on human primary tissues are hampered by a lack of tissue availability as well as ethical concerns. Recent development in human pluripotent stem cell (PSC) technology include the generation of three-dimensional (3D) self-organizing organotypic culture systems, which mimic to a certain extent human-specific brain development in vitro. Currently, various protocols are available for the generation of either whole brain or brain-region specific organoids. The method for the generation of homogeneous and reproducible forebrain-type organoids from induced PSC (iPSC), which we previously established and describe here, combines the intrinsic ability of PSC to self-organize with guided differentiation towards the anterior neuroectodermal lineage and matrix embedding to support the formation of a continuous neuroepithelium. More specifically, this protocol involves: (1) the generation of iPSC aggregates, including the conversion of iPSC colonies to a confluent monolayer culture; (2) the induction of anterior neuroectoderm; (3) the embedding of neuroectodermal aggregates in a matrix scaffold; (4) the generation of forebrain-type organoids from neuroectodermal aggregates; and (5) the fixation and validation of forebrain-type organoids. As such, this protocol provides an easily applicable system for the generation of standardized and reproducible iPSC-derived cortical tissue structures in vitro.
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Organoids, Assembloids, and Novel Biotechnology: Steps Forward in Developmental and Disease-Related Neuroscience.
In neuroscience research, the efforts to find the model through which we can mimic the in vivo microenvironment of a developing or defective brain have been everlasting. While model organisms are used for over a hundred years, many more methods have been introduced with immortalized or primary cell lines and later induced pluripotent stem cells and organoids to be some of these. As the use of organoids becomes more and more common by many laboratories in biology and neuroscience in particular, it is crucial to deeper understand the challenges and possible pitfalls of their application in research, many of which can be surpassed with the support of state-of-the art bioengineering solutions. In this review, after a brief chronicle of the path to the discovery of organoids, we focus on the latest approaches to study neuroscience related topics with organoids, such as the use of assembloids, CRISPR technology, patch-clamp and optogenetics techniques and discuss how modern 3-dimensional biomaterials, miniaturized bioreactors and microfluidic chips can help to overcome the disadvantages of their use.
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Controlled-environment platform for electrophysiology recordings on organoids with Neuropixels 2.0.
We present a custom recording platform that enables electrophysiological recordings with Neuropixels 2.0 from human brain and heart organoids by maintaining a stable, physiological environment of 5% CO2, 37 °C, and 95% relative humidity. The platform combines a modular positioning system with real-time camera guidance for precise probe alignment. We validated the system by recording consistent bursting activity in brain organoids over a 110-min period and in heart organoids for up to 11 h.