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Histofluorescence and ultrastructural evidence for catecholamine-containing sensory neurons bordering the interventricular foramen of the toad brain.
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An electron microscopic study of central nervous system sarcoidosis.
Although the fine structure of extraneural sarcoidosis is well documented, ultrastructural study of central nervous system (CNS) sarcoidosis has been limited. Electron microscopic (EM) examination of 3 biopsy cases of CNS sarcoid revealed a mixed cellular population of lymphocytes, epitheloid cells, and multinucleated giant cells. The epitheloid and multinucleated giant cells shared common ultrastructural features of nuclei and cytoplasm. In addition, they displayed similar specializations of the cell surface, including subplasmalemmal linear densities (SLD) and villous projections. These findings recapitulate those described in extraneural sarcoidosis and other granulomatous disorders. This supports the contention that the macrophages or epitheloid cells present in CNS lesions are derived from the same mononuclear phagocytic system as their systemic counterparts.
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Protocol for generating human cortical organoids enriched in outer radial glia by guided differentiation.
The generation of human pluripotent stem cell (hPSC)-derived brain organoids is continuously refined, enhancing their reproducibility and complexity. Here, we present a guided differentiation protocol for generating cortical forebrain organoids and cortico-pericyte (CP)assembloids composed of a robust outer radial glia (oRG) population and an expanded outer subventricular zone (oSVZ). We describe the steps to generate hPSC-derived cortical organoids (COs), cortical pericytes, and CP assembloids. Moreover, we outline the procedures to characterize the organoids by immunostaining and to perform single-cell dissociation. For complete details on the use and execution of this protocol, please refer to Walsh et al.1.
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Modeling neurodegenerative diseases with cerebral organoids and other three-dimensional culture systems: focus on Alzheimer's disease.
Many neurodegenerative diseases (NDs) such as Alzheimer's disease, Parkinson's disease, frontotemporal dementia, amyotrophic lateral sclerosis and Huntington's disease, are characterized by the progressive accumulation of abnormal proteinaceous assemblies in specific cell types and regions of the brain, leading to cellular dysfunction and brain damage. Although animal- and in vitro-based studies of NDs have provided the field with an extensive understanding of some of the mechanisms underlying these diseases, findings from these studies have not yielded substantial progress in identifying treatment options for patient populations. This necessitates the development of complementary model systems that are better suited to recapitulate human-specific features of ND pathogenesis. Three-dimensional (3D) culture systems, such as cerebral organoids generated from human induced pluripotent stem cells, hold significant potential to model NDs in a complex, tissue-like environment. In this review, we discuss the advantages of 3D culture systems and 3D modeling of NDs, especially AD and FTD. We also provide an overview of the challenges and limitations of the current 3D culture systems. Finally, we propose a few potential future directions in applying state-of-the-art technologies in 3D culture systems to understand the mechanisms of NDs and to accelerate drug discovery. Graphical abstract.
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The ciliary gene INPP5E confers dorsal telencephalic identity to human cortical organoids by negatively regulating Sonic hedgehog signaling.
Defects in primary cilia, cellular antennas that control multiple intracellular signaling pathways, underlie several neurodevelopmental disorders, but it remains unknown how cilia control essential steps in human brain formation. Here, we show that cilia are present on the apical surface of radial glial cells in human fetal forebrain. Interfering with cilia signaling in human organoids by mutating the INPP5E gene leads to the formation of ventral telencephalic cell types instead of cortical progenitors and neurons. INPP5E mutant organoids also show increased Sonic hedgehog (SHH) signaling, and cyclopamine treatment partially rescues this ventralization. In addition, ciliary expression of SMO, GLI2, GPR161, and several intraflagellar transport (IFT) proteins is increased. Overall, these findings establish the importance of primary cilia for dorsal and ventral patterning in human corticogenesis, indicate a tissue-specific role of INPP5E as a negative regulator of SHH signaling, and have implications for the emerging roles of cilia in the pathogenesis of neurodevelopmental disorders.
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Fine structure of the neural sheath, glia and neurons in the brain of the housefly, Musca domestica.
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Oxygen-induced brain vacuolation in Drosophila and a possible threshold for this response.
Wild type populations of Drosophila melanogaster were exposed to 21%, 33%, 45%, and 55% oxygen at normal atmospheric pressures. Individuals were selected randomly at 5-d intervals and inspected for vacuolation of the forebrain. Longevity of the populations was also measured. Flies in 21% and 33% oxygen had identical survivorship and even after 50 d showed little vacuolation. Flies maintained in 45% oxygen showed rapid mortality between 30-40 d and were found to have vacuolated forebrains. Populations treated in 55% oxygen declined rapidly in numbers between 20-30 d and showed severe vacuolation of the forebrain. It was considered important that normal longevity and normal aging of brain cells in 33% oxygen at standard pressure were found because similar partial pressures of pure oxygen were reported to significantly reduce longevity. It is suggested that, because insects are known to be tolerant to fairly extreme changes in total atmospheric pressure, a partial pressure of nitrogen as a diluent gas is the important factor in the toxic effects of a given pressure of oxygen. The study indicates that in a nitrogen/oxygen mix at 760 torr total pressure, the threshold to toxicity lies near, or just beyond, 300 torr oxygen. The authors indicate that preliminary findings in their current work show that if a small partial pressure of nitrogen is maintained, the total pressure can be reduced considerably without affecting this threshold level.
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Exploring the source of human brain fluids.
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Bystander neuronal progenitors in forebrain organoids promote protective antiviral responses.
Neurotropic viruses are the most common cause of infectious encephalitis and highly target neurons for infection. Our understanding of the intrinsic capacity of neuronal innate immune responses to mediate protective antiviral responses remains incomplete. Here, we evaluated the role of intercellular crosstalk in mediating intrinsic neuronal immunity and its contribution to limiting viral infection. We found that in the absence of viral antagonism, neurons transcriptionally induce robust interferon signaling and can effectively signal to uninfected bystander neurons. Yet, in two-dimensional cultures, this dynamic response did not restrict viral spread. Interestingly, this differed in the context of viral infection in three-dimensional forebrain organoids with complex neuronal subtypes and cellular organization, where we observed protective capacity. We showed antiviral crosstalk between infected neurons and bystander neural progenitors is mediated by type I interferon signaling. Using spatial transcriptomics, we then uncovered regions containing bystander neural progenitors that expressed distinct antiviral genes, revealing critical underpinnings of protective antiviral responses among neuronal subtypes. These findings underscore the importance of interneuronal communication in protective antiviral immunity in the brain and implicate key contributions to protective antiviral signaling.
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Comparison of the DNA's obtained from brain nuclei and mitochondria of mice and from the nuclei and kinetoplasts of Leishmania enriettii.