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Recipe for pituitary organoids.
Generation of a variety of organs and tissues from human pluripotent stem cells (hPSCs) has been attempted in vitro. We here present a simple and efficient method for induction of hypothalamic and pituitary tissues from hPSCs. On provision of exogenous agents important for early hypothalamus-pituitary organogenesis, including bone morphogenetic protein 4 and activators of sonic hedgehog, in three-dimensional culture, hPSCs spontaneously form spherical organoids with two distinct tissues, hypothalamus and adenohypophysis. The pituitary tissues derived from hPSCs not only secrete adenocorticotropic hormone, but also retain both positive and negative feedback mechanisms, recapitulating mature endocrine organs in vivo. Furthermore, the results of ectopic transplantation with mouse models of hypopituitarism suggest that these hypothalamus-pituitary organoids have potential as engraftment organs. In addition to their use in transplantation for patients with hypopituitarism they will allow establishment of disease models in vitro and enable research impossible in humans. Hypothalamus-pituitary organoids promise to be a powerful tool in regenerative medicine, drug discovery, and basic research into pituitary development.
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The ultrastructure of "brain death". II. Electron microscopy of feline cortex after complete ischemia.
Permanent, complete global cerebral ischemia was induced in cats by filling the cardiovascular system with a plasma substitute (37 degrees C). At variable intervals and up to 120 min thereafter, these feline brains were perfused with aldehydes and processed for electron microscopy. The resulting cellular alterations were homogeneous and uniform throughout the entire brain; they included early chromatin clumping, gradually increasing electron lucency of the cell sap, distention of endoplasmic reticulum and Golgi cisternae, transient mitochondrial condensation followed by swelling and appearance of flocculent densities, and dispersion of ribosomal rosettes. The marked contrast between the structural alterations in permanent, complete ischemia and incomplete cerebral ischemia, suggest differences in their pathogenesis. A basic determinant factor of the structural changes appears to be the volume of flow (serum, plasma, other) which is available at the time of the injury. This analysis of global cerebral ischemia provides some insight on the nature of cellular changes occurring shortly after somatic death.
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Simple modeling of familial Alzheimer's disease using human pluripotent stem cell-derived cerebral organoid technology.
BACKGROUND: Cerebral organoids (COs) are the most advanced in vitro models that resemble the human brain. The use of COs as a model for Alzheimer's disease (AD), as well as other brain diseases, has recently gained attention. This study aimed to develop a human AD CO model using normal human pluripotent stem cells (hPSCs) that recapitulates the pathological phenotypes of AD and to determine the usefulness of this model for drug screening. METHODS: We established AD hPSC lines from normal hPSCs by introducing genes that harbor familial AD mutations, and the COs were generated using these hPSC lines. The pathological features of AD, including extensive amyloid-β (Aβ) accumulation, tauopathy, and neurodegeneration, were analyzed using enzyme-linked immunosorbent assay, Amylo-Glo staining, thioflavin-S staining, immunohistochemistry, Bielschowsky's staining, and western blot analysis. RESULTS: The AD COs exhibited extensive Aβ accumulation. The levels of paired helical filament tau and neurofibrillary tangle-like silver deposits were highly increased in the AD COs. The number of cells immunoreactive for cleaved caspase-3 was significantly increased in the AD COs. In addition, treatment of AD COs with BACE1 inhibitor IV, a β-secretase inhibitor, and compound E, a γ-secretase inhibitor, significantly attenuated the AD pathological features. CONCLUSION: Our model effectively recapitulates AD pathology. Hence, it is a valuable platform for understanding the mechanisms underlying AD pathogenesis and can be used to test the efficacy of anti-AD drugs.
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16p11.2 deletion accelerates subpallial maturation and increases variability in human iPSC-derived ventral telencephalic organoids.
Inhibitory interneurons regulate cortical circuit activity, and their dysfunction has been implicated in autism spectrum disorder (ASD). 16p11.2 microdeletions are genetically linked to 1% of ASD cases. However, few studies investigate the effects of this microdeletion on interneuron development. Using ventral telencephalic organoids derived from human induced pluripotent stem cells, we have investigated the effect of this microdeletion on organoid size, progenitor proliferation and organisation into neural rosettes, ganglionic eminence marker expression at early developmental timepoints, and expression of the neuronal marker NEUN at later stages. At early stages, deletion organoids exhibited greater variations in size with concomitant increases in relative neural rosette area and the expression of the ventral telencephalic marker COUPTFII, with increased variability in these properties. Cell cycle analysis revealed an increase in total cell cycle length caused primarily by an elongated G1 phase, the duration of which also varied more than normal. At later stages, deletion organoids increased their NEUN expression. We propose that 16p11.2 microdeletions increase developmental variability and may contribute to ASD aetiology by lengthening the cell cycle of ventral progenitors, promoting premature differentiation into interneurons.
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Temporal mapping of radiation-induced neural injury and mitigation in human cortical organoids.
BACKGROUND: Radiation therapy is a standard-of-care oncological treatment for central nervous system (CNS) malignancies. However, as survival outcomes improve, radiation-induced injury to normal brain tissue has increased in clinical significance. CNS radiation injury is a delayed, multifactorial process characterized by impaired neurogenesis, reactive gliosis, and persistent functional deficits. Mechanistic exploration and development of effective radiation mitigators have been limited by the lack of scalable, human-relevant models. METHODS: Mature human iPSC-derived cortical organoids were exposed to single-dose or clinically relevant fractionated radiation (5 × 2 Gy). DNA damage, apoptosis, and growth dynamics were assessed longitudinally. Structural organization, synaptic integrity, and neuroinflammatory responses were evaluated by immunofluorescence and real-time PCR. Transcriptomic profiling was performed at 72 hours and 2 weeks after fractionated radiation to capture acute and delayed effects. Two candidate radiation mitigators, NSPP and amisulpride, were tested for their therapeutic effects within the organoid system. RESULTS: Cortical organoids exhibited partial recovery following single doses up to 4 Gy or fractioned irradiation. Transcriptomic analyses revealed that radiation not only reduced overall cell viability but also reshaped lineage trajectories, characterized by depletion of neural stem/progenitor populations, loss of neuronal identity, enhanced gliogenesis, increased inflammatory cytokines, and disrupted cortical layering and synaptic integrity. Treatment with NSPP or amisulpride attenuated injury-associated transcriptional and structural alterations. CONCLUSION: Human cortical organoids recapitulate key features of radiation-induced neural injury, recovery, and therapeutic modulation, providing a robust, scalable, and human-relevant platform for studying CNS radiation biology and preclinical screening of candidate radiation mitigators.
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Light- and chemical-induced ciliary signaling governs dorsal/ventral regionalization of human telencephalic organoids.
Neural stem/progenitor cells (NPCs) have primary cilia, which are critical organelles for Sonic hedgehog signaling. However, little is known about the components of primary cilia in NPCs and whether manipulating signaling in the cilia is sufficient to alter dorsal/ventral regional identity. Using a human telencephalic organoid model, we perform comprehensive proteomic profiling of NPC cilia and find enrichment in GTPase signaling. Deletion of the ciliary GTPase ARL13B reduces ciliary localization of GPR161, an orphan G protein-coupled receptor 161 that negatively regulates Sonic hedgehog, resulting in ventralization of NPCs. GPR161 deletion also induces ventralization. To investigate whether manipulation of ciliary signaling is sufficient to restore dorsal identity in this context, we optogenetically elevate ciliary cAMP, rescuing dorsal fate in GPR161 KO organoids. Furthermore, chemogenetic induction of GPR161 removal from cilia is sufficient to increase ventral NPCs. These data indicate that ciliary signaling functions as a critical switch regulating dorsal/ventral fate decisions.
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Alpha-synuclein pathology is associated with astrocyte senescence in a midbrain organoid model of familial Parkinson's disease.
Parkinson's disease (PD) is a complex, progressive neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta in the midbrain. Despite extensive research efforts, the molecular and cellular changes that precede neurodegeneration in PD are poorly understood. To address this, here we describe the use of patient specific human midbrain organoids harboring the SNCA triplication to investigate mechanisms underlying dopaminergic degeneration. Our midbrain organoid model recapitulates key pathological hallmarks of PD, including the aggregation of α-synuclein and the progressive loss of dopaminergic neurons. We found that these pathological hallmarks are associated with an increase in senescence associated cellular phenotypes in astrocytes including nuclear lamina defects, the presence of senescence associated heterochromatin foci, and the upregulation of cell cycle arrest genes. These results suggest a role of pathological α-synuclein in inducing astrosenescence which may, in turn, increase the vulnerability of dopaminergic neurons to degeneration.
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Lineage recording in human cerebral organoids.
Induced pluripotent stem cell (iPSC)-derived organoids provide models to study human organ development. Single-cell transcriptomics enable highly resolved descriptions of cell states within these systems; however, approaches are needed to directly measure lineage relationships. Here we establish iTracer, a lineage recorder that combines reporter barcodes with inducible CRISPR-Cas9 scarring and is compatible with single-cell and spatial transcriptomics. We apply iTracer to explore clonality and lineage dynamics during cerebral organoid development and identify a time window of fate restriction as well as variation in neurogenic dynamics between progenitor neuron families. We also establish long-term four-dimensional light-sheet microscopy for spatial lineage recording in cerebral organoids and confirm regional clonality in the developing neuroepithelium. We incorporate gene perturbation (iTracer-perturb) and assess the effect of mosaic TSC2 mutations on cerebral organoid development. Our data shed light on how lineages and fates are established during cerebral organoid formation. More broadly, our techniques can be adapted in any iPSC-derived culture system to dissect lineage alterations during normal or perturbed development.
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Integrated 3D human cerebral organoids and paediatric patient serum analysis reveals mechanisms and biomarkers of anaesthetic-induced neurotoxicity.
BACKGROUND: General anaesthetics are essential for paediatric surgery but have been associated with neuronal injury and long-term cognitive deficits, thereby raising concerns over neurodevelopmental safety. However, the molecular mechanisms underlying anaesthetic-induced developmental neurotoxicity remain poorly understood. METHODS: Human cerebral organoids derived from induced pluripotent stem cells were exposed to propofol (1-6 h; single or repeated exposures). In parallel, serum samples were collected from paediatric patients (age: <4 yr; n=10 per group) undergoing short (<1 h) or prolonged (>3 h) anaesthetic procedures. Organoid pathology and mitochondrial function were assessed using chemical assays, electron microscopy, and immunoblotting. Genome-wide profiling of 18 855 coding RNAs (mRNAs) and 27 427 long noncoding RNAs (lncRNAs) was performed by microarray analysis. RESULTS: Propofol exposure increased apoptosis (1.9 [0.3] vs 1.0 [0.1]; P=0.0173) and autophagy (0.78 [0.12] vs 0.45 [0.09]; P=0.028) in organoids, and dysregulated 553 mRNAs and 792 lncRNAs linked to synaptic function, mitochondrial activity, and inflammation. ATP production (P=0.045), and expression of CKMT1B (P=0.002) and synaptic markers PSD95 and c-Fos were reduced. Serum from children exposed to prolonged anaesthesia showed elevated neuronal injury markers and 33 overlapping dysregulated RNAs (21 mRNAs, 12 lncRNAs), including CKMT1B. Bioinformatics revealed enrichment of these dysregulated lncRNA-mRNA networks in pathways related to cell injury, neurodevelopment, and cognition. CONCLUSIONS: This study establishes a human-relevant model of anaesthetic-induced developmental neurotoxicity by integrating human organoids with clinical serum profiling. Propofol exposure led to mitochondrial dysfunction and disruption of coding RNA and lncRNA networks involved in neuronal development and injury. Concordant gene signatures (e.g. CKMT1B) across models highlight their potential as translational biomarkers and therapeutic targets.
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Integrated transcriptome and proteome analysis reveals posttranscriptional regulation of ribosomal genes in human brain organoids.
During development of the human cerebral cortex, multipotent neural progenitors generate excitatory neurons and glial cells. Investigations of the transcriptome and epigenome have revealed important gene regulatory networks underlying this crucial developmental event. However, the posttranscriptional control of gene expression and protein abundance during human corticogenesis remains poorly understood. We addressed this issue by using human telencephalic brain organoids grown using a dual reporter cell line to isolate neural progenitors and neurons and performed cell class and developmental stage-specific transcriptome and proteome analysis. Integrating the two datasets revealed modules of gene expression during human corticogenesis. Investigation of one such module uncovered mTOR-mediated regulation of translation of the 5'TOP element-enriched translation machinery in early progenitor cells. We show that in early progenitors partial inhibition of the translation of ribosomal genes prevents precocious translation of differentiation markers. Overall, our multiomics approach proposes novel posttranscriptional regulatory mechanisms crucial for the fidelity of cortical development.