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Found: 5 473
Page 253 of 548-
Neural Tube Organoids: A Novel System to Study Developmental Timing.
The neural tube (NT) is a transient structure formed during embryogenesis which develops into the brain and spinal cord. While mouse models have been commonly used in place of human embryos to study NT development, species-specific differences limit their applicability. One major difference is developmental timing, with NT formation from the neural plate in 16 days in humans compared to 4 days in mice, as well as differences in the time taken to form neuronal subtypes and complete neurogenesis. Neural tube organoids (NTOs) represent a new way to study NT development in vitro. While mouse and human NTOs have been shown to recapitulate the major developmental events of NT formation; it is unknown whether species-specific developmental timing, also termed allochrony, is also recapitulated. This review summarises current research using both mouse and human NTOs and compares developmental timing events in order to assess if allochrony is maintained in organoids.
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Neutralizing antibodies with neurotropic factor treatment maintain neurodevelopmental gene expression upon exposure to human cytomegalovirus.
Human cytomegalovirus (HCMV) infection is the leading cause of non-heritable birth defects worldwide. HCMV readily infects the early progenitor cell population of the developing brain, and we have found that infection leads to significantly downregulated expression of key neurodevelopmental transcripts. Currently, there are no approved therapies to prevent or mitigate the effects of congenital HCMV infection. Therefore, we used human-induced pluripotent stem cell-derived organoids and neural progenitor cells to elucidate the glycoproteins and receptors used in the viral entry process and whether antibody neutralization was sufficient to block viral entry and prevent disruption of neurodevelopmental gene expression. We found that blocking viral entry alone was insufficient to maintain the expression of key neurodevelopmental genes, but neutralization combined with neurotrophic factor treatment provided robust protection. Together, these studies offer novel insight into mechanisms of HCMV infection in neural tissues, which may aid future therapeutic development.
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Astrocytic characteristics of oligodendroglioma. Fine structural and immunohistochemical studies of two cases.
Two oligodendrogliomas were studied by light and electron microscopy. Additionally, an immunohistochemical study for glial fibrillary acidic protein (GFAP) was carried out. Some tumor cells exhibited glial filaments and perivascular end-feet, as on the one hand is characteristic of astrocytes, and glycogen granules and zonulae adherents which on the other hand are often seen in astrocytes but rarely in oligodendrocytes. Tumor cells with or without astrocytic characteristics showed the common fine structures and appeared to be on the same cell line. Our fine structural and immunohistochemical findings suggest that oligodendroglioma cells are of an astrocytic nature.
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The role of clathrin-coated vesicles in acrosome formation.
Ultrastructural and cytochemical observations are presented which suggest that coated vesicles originating from the trans (distal) aspect of the rat spermatid Golgi apparatus transport lysosomal enzymes from the Golgi to the developing acrosome. Using an affinity purified antibody against the clathrin coats of pig brain coated vesicles, immunofluorescence and immuno-electron microscopic studies were carried out on frozen sections of rat seminiferous tubules. The results showed a specific labelling of the Golgi-acrosome region which corresponded precisely with the location of the coated vesicles in Epon sections. We conclude tht a least some of the coated vesicles in this region have clathrin coats.
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Modulation of Endoplasmic Reticulum Stress via CEBPB: A Potential Molecular Link to Therapeutic Action in Substance Use Disorders.
AIMS: Opioid use disorder remains a major public health crisis in the United States, driven largely by rising overdose deaths from synthetic opioids, such as fentanyl. Emerging population-level evidence suggests that GLP-1 receptor agonists (GLP-1RAs) may reduce overdose risk. However, their underlying molecular mechanisms are not well understood. We investigated the transcriptional effects of fentanyl and GLP-1RAs using human induced pluripotent stem cell (iPSC)-derived forebrain organoids and neurons. METHODS: Organoids were treated with fentanyl, liraglutide, or exenatide, followed by RNA sequencing. We extended these analyses to iPSC-derived neurons exposed to additional therapeutic candidates, including the anticonvulsants topiramate and gabapentin, and the metabolic modulator β-hydroxybutyrate. All compounds were tested at clinically relevant concentrations, and transcriptomic and functional genomic assays were performed. RESULTS: Across models and drug classes, we identified modulation of endoplasmic reticulum (ER) stress signaling as a shared molecular mechanism. Fentanyl and GLP-1RAs consistently downregulated ER stress-related genes, with TRIB3 as the most strongly suppressed target. We further identified CEBPB as a key upstream regulator and confirmed reduced CEBPB DNA-binding activity in ER stress-related genes. CONCLUSION: These findings highlight ER stress modulation as a convergent pathway with potential therapeutic relevance for substance use disorders.
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Generating human neural diversity with a multiplexed morphogen screen in organoids.
Morphogens choreograph the generation of remarkable cellular diversity in the developing nervous system. Differentiation of stem cells in vitro often relies upon the combinatorial modulation of these signaling pathways. However, the lack of a systematic approach to understand morphogen-directed differentiation has precluded the generation of many neural cell populations, and the general principles of regional specification and maturation remain incomplete. Here, we developed an arrayed screen of 14 morphogen modulators in human neural organoids cultured for over 70 days. Deconvolution of single-cell-multiplexed RNA sequencing data revealed design principles of brain region specification. We tuned neural subtype diversity to generate a tachykinin 3 (TAC3)-expressing striatal interneuron type within assembloids. To circumvent limitations of in vitro neuronal maturation, we used a neonatal rat transplantation strategy that enabled human Purkinje neurons to develop their hallmark complex dendritic branching. This comprehensive platform yields insights into the factors influencing stem cell-derived neural diversification and maturation.
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KRIT1 heterozygous mutations are sufficient to induce a pathological phenotype in patient-derived iPSC models of cerebral cavernous malformation.
Cerebral cavernous malformation (CCM) is a neurovascular disease distinguished by clusters of leaky, mulberry-like blood vessels. KRIT1 bi-allelic loss-of-function mutations in endothelial cells are known to trigger brain cavernomas; however, human preclinical models are needed to unveil the importance of germline KRIT1 heterozygous mutations in CCM pathogenesis. We generated three induced pluripotent stem cells (iPSCs) from patients with CCM with hereditary KRIT1 heterozygous mutations. Patient-derived vascularized organoids exhibited intricate and abnormal vascular structures with cavernoma-like morphology, and iPSC-derived endothelial cells displayed phenotypic abnormalities at the junctional and transcriptional levels. Upon injection into brain explants, CCM endothelial cells integrated into the normal vasculature and created vascular anomalies. Lastly, transcriptional analysis showed that the endothelial progenitor marker paternally expressed gene 3 (PEG3) was highly expressed in iPSC-derived CCM endothelial cells, and this was further confirmed in familial and sporadic cavernoma biopsies. Overall, our study sheds light on the molecular consequence of KRIT1 heterozygous mutations in endothelial cells and the potential implications in cavernoma pathogenesis.
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Collagen and derivatives-based materials as substrates for the establishment of glioblastoma organoids.
Glioblastoma (GBM) is a common primary brain malignancy known for its ability to invade the brain, resistance to chemotherapy and radiotherapy, tendency to recur frequently, and unfavorable prognosis. Attempts have been undertaken to create 2D and 3D models, such as glioblastoma organoids (GBOs), to recapitulate the glioma microenvironment, explore tumor biology, and develop efficient therapies. However, these models have limitations and are unable to fully recapitulate the complex networks formed by the glioma microenvironment that promote tumor cell growth, invasion, treatment resistance, and immune escape. Therefore, it is necessary to develop advanced experimental models that could better simulate clinical physiology. Here, we review recent advances in natural biomaterials (mainly focus on collagen and its derivatives)-based GBO models, as in vitro experimental platforms to simulate GBM tumor biology and response to tested drugs. Special attention will be given to 3D models that use collagen, gelatin, further modified derivatives, and composite biomaterials (e.g., with other natural or synthetic polymers) as substrates. Application of these collagen/derivatives-constructed GBOs incorporate the physical as well as chemical characteristics of the GBM microenvironment. A perspective on future research is given in terms of current issues. Generally, natural materials based on collagen/derivatives (monomers or composites) are expected to enrich the toolbox of GBO modeling substrates and potentially help to overcome the limitations of existing models.
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Altered energy metabolism in Fatal Familial Insomnia cerebral organoids is associated with astrogliosis and neuronal dysfunction.
Fatal familial insomnia (FFI) is a rare neurodegenerative disease caused by a dominantly inherited single amino acid substitution (D178N) within the prion protein (PrP). No in vitro human brain tissue model for this disease has previously been available. Consequently, how this mutation exerts its damaging effect on brain cells is still unknown. Using CRISPR-Cas9 engineered induced pluripotent stem cells, we made D178N cerebral organoids and compared these with isotype control organoids. We found that, in the absence of other hallmarks of FFI, the D178N organoids exhibited astrogliosis with cellular oxidative stress. Abnormal post-translational processing of PrP was evident but no tissue deposition or propagation of mis-folded PrP isoforms were observed. Neuronal electrophysiological function was compromised and levels of neurotransmitters, particularly acetylcholine and GABA, altered. Underlying these dysfunctions were changes in cellular energy homeostasis, with substantially increased glycolytic and Krebs cycle intermediates, and greater mitochondrial activity. This increased energy demand in D178N organoids was associated with increased mitophagy and depletion of lipid droplets, in turn resulting in shifts of cellular lipid composition. Using a double mutation (178NN) we could confirm that most changes were caused by the presence of the mutation rather than interaction with PrP molecules lacking the mutation. Our data strongly suggests that shifting biosynthetic intermediates and oxidative stress, caused by an imbalance of energy supply and demand, results in astrogliosis with compromised neuronal activity in FFI organoids. They further support that many of the disease associated changes are due to a corruption of PrP function and do not require propagation of PrP mis-folding.
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Ultrastructure of the asexual apparatus in Mycotypha (Mucorales).
The development of the asexual apparatus of Mycotypha africana and Mycotypha poitrasii observed by means of scanning electron microscopy is reported. Using ultrathin sections and freeze-fracture replicas, sporangiole structure is described. Sporangiospore structure is compared with that of other members of the Thamnidiaceae.