RESUMO
Although Extreme Learning Machine (ELM) can learn thousands of times faster than traditional slow gradient algorithms for training neural networks, ELM fitting accuracy is limited. This paper develops Functional Extreme Learning Machine (FELM), which is a novel regression and classifier. It takes functional neurons as the basic computing units and uses functional equation-solving theory to guide the modeling process of functional extreme learning machines. The functional neuron function of FELM is not fixed, and its learning process refers to the process of estimating or adjusting the coefficients. It follows the spirit of extreme learning and solves the generalized inverse of the hidden layer neuron output matrix through the principle of minimum error, without iterating to obtain the optimal hidden layer coefficients. To verify the performance of the proposed FELM, it is compared with ELM, OP-ELM, SVM and LSSVM on several synthetic datasets, XOR problem, benchmark regression and classification datasets. The experimental results show that although the proposed FELM has the same learning speed as ELM, its generalization performance and stability are better than ELM.
RESUMO
Many neurons undergo apoptosis after ischemic stroke. In the brain, neurogenesis has the potential for neuronal replacement and can be activated by external conditions to repair the injury. Crocetin (CRO), naturally extracted from the plant saffron, acts as a neuroprotective agent for ischemic stroke. However, the underlying mechanism remains unknown. In this work, the effect of CRO on neural stem cell (NSC) behaviors and subventricular zone neurogenesis is investigated. Initially, NSCs are incubated with different concentrations of CRO to detect the cell proliferation and differentiation in vitro. Second, ischemic stroke induced rats are treated with CRO using nimodipine (NMDP) as a comparison. The behavioral functions, infarcted volume, and apoptotic Nissl bodies of rats are noticeably improved after CRO-treatment, comparable to those of NMDP. In addition, the increased regional cerebral blood flow and promoted neuronal differentiation are achieved by CRO-treatment. Brain tissue examination shows significantly increased neuronal regeneration in the focal ischemic injury area. Meanwhile, the length of neurites is prolonged, indicating that CRO could potentially promote neurite extension to enhance cell-cell communication. These findings demonstrate that CRO facilitated the neuronal differentiation of NSCs by activating subventricular zone neurogenesis in damaged cortex and striatum sites to repair ischemic stroke.
Assuntos
Isquemia Encefálica , AVC Isquêmico , Células-Tronco Neurais , Acidente Vascular Cerebral , Ratos , Animais , Neurônios/fisiologia , Neurogênese/fisiologia , Acidente Vascular Cerebral/terapiaRESUMO
Glial scars formed after brain injuries provide permissive cues for endogenous neural precursor/stem cells (eNP/SCs) to undergo astrogenesis rather than neurogenesis. Following brain injury, eNP/SCs from the subventricular zone leave their niche, migrate to the injured cortex, and differentiate into reactive astrocytes that contribute to glial scar formation. In vivo neuronal reprogramming, directly converting non-neuronal cells such as reactive astrocytes or NG2 glia into neurons, has greatly improved brain injury repair strategies. However, reprogramming carries a high risk of future clinical applications such as tumorigenicity, involving virus. In this study, we constructed a neural matrix to alter the adverse niche at the injured cortex, enabling eNP/SCs to differentiate into functional neurons. We found that the neural matrix functioned as a "glial trap" that largely concentrated and limited reactive astrocytes to the core of the lesion area, thus altering the adverse niche. The eNP/SCs migrated toward the injured cortex and differentiated into functional neurons. In addition, regenerated neurites extended across the boundary of the injured cortex. Mice treated with the neural matrix demonstrated significant behavioral recovery. For the first time, we induced eNP/SC-derived functional neurons in the cortex after brain injury without the use of viruses, microRNAs, or small molecules. Our novel strategy of applying this "glial trap" to obtain functional neurons in the injured cortex may provide a safer and more natural therapeutic alternative to reprogramming in future clinical applications.
Assuntos
Lesões Encefálicas Traumáticas/tratamento farmacológico , Reprogramação Celular/efeitos dos fármacos , Córtex Cerebral/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Animais , Lesões Encefálicas Traumáticas/metabolismo , Lesões Encefálicas Traumáticas/patologia , Fator Neurotrófico Derivado do Encéfalo/química , Fator Neurotrófico Derivado do Encéfalo/farmacologia , Diferenciação Celular/efeitos dos fármacos , Movimento Celular/efeitos dos fármacos , Córtex Cerebral/metabolismo , Córtex Cerebral/patologia , Quimiocina CXCL12/química , Quimiocina CXCL12/farmacologia , Condroitina ABC Liase/química , Condroitina ABC Liase/farmacologia , Modelos Animais de Doenças , Proteínas Imobilizadas/química , Proteínas Imobilizadas/farmacologia , Ventrículos Laterais/citologia , Ventrículos Laterais/fisiologia , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Transgênicos , Fator de Crescimento Neural/química , Fator de Crescimento Neural/farmacologia , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/fisiologia , Neurogênese/fisiologia , Neuroglia/citologia , Neuroglia/efeitos dos fármacos , Neuroglia/fisiologia , Neurônios/citologia , Neurônios/fisiologia , Bulbo Olfatório/citologia , Bulbo Olfatório/fisiologia , Teste de Desempenho do Rota-Rod , Nicho de Células-Tronco/efeitos dos fármacosRESUMO
Converting resident glia into functional and subtype-specific neurons in vivo by delivering reprogramming genes directly to the brain provides a step forward toward the possibility of treating brain injuries or diseases. To date, it has been possible to obtain GABAergic and glutamatergic neurons via in vivo conversion, but the precise phenotype of these cells has not yet been analyzed in detail. Here, we show that neurons reprogrammed using Ascl1, Lmx1a, and Nurr1 functionally mature and integrate into existing brain circuitry and that the majority of the reprogrammed neurons have properties of fast-spiking, parvalbumin-containing interneurons. When testing different combinations of genes for neural conversion with a focus on pro-neural genes and dopamine fate determinants, we found that functional neurons can be generated using different gene combinations and in different brain regions and that most of the reprogrammed neurons become interneurons, independently of the combination of reprogramming factors used.
Assuntos
Potenciais de Ação , Reprogramação Celular , Interneurônios/metabolismo , Neuroglia/metabolismo , Parvalbuminas/metabolismo , Animais , Diferenciação Celular , Denervação , Dopamina/metabolismo , Regulação da Expressão Gênica , Camundongos , Neostriado/citologia , Fenótipo , Fatores de TempoRESUMO
Direct lineage reprogramming, including with small molecules, has emerged as a promising approach for generating desired cell types. We recently found that during chemical induction of induced pluripotent stem cells (iPSCs) from mouse fibroblasts, cells pass through an extra-embryonic endoderm (XEN)-like state. Here, we show that these chemically induced XEN-like cells can also be induced to directly reprogram into functional neurons, bypassing the pluripotent state. The induced neurons possess neuron-specific expression profiles, form functional synapses in culture, and further mature after transplantation into the adult mouse brain. Using similar principles, we were also able to induce hepatocyte-like cells from the XEN-like cells. Cells in the induced XEN-like state were readily expandable over at least 20 passages and retained genome stability and lineage specification potential. Our study therefore establishes a multifunctional route for chemical lineage reprogramming and may provide a platform for generating a diverse range of cell types via application of this expandable XEN-like state.
Assuntos
Reprogramação Celular , Endoderma/citologia , Membranas Extraembrionárias/citologia , Fibroblastos/metabolismo , Envelhecimento , Animais , Animais Recém-Nascidos , Encéfalo/citologia , Diferenciação Celular , Linhagem da Célula , Sobrevivência Celular , Células Cultivadas , Feminino , Perfilação da Expressão Gênica , Instabilidade Genômica , Proteínas de Fluorescência Verde/metabolismo , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Masculino , Camundongos , Neurônios/citologia , Neurônios/metabolismo , Neurônios/transplante , Transcrição GênicaRESUMO
Because neurons are difficult to obtain from humans, generating functional neurons from human induced pluripotent stem cells (hiPSCs) is important for establishing physiological or disease-relevant screening systems for drug discovery. To examine the culture conditions leading to efficient differentiation of functional neural cells, we investigated the effects of oxygen stress (2% or 20% O2) and differentiation medium (DMEM/F12:Neurobasal-based [DN] or commercial [PhoenixSongs Biologicals; PS]) on the expression of genes related to neural differentiation, glutamate receptor function, and the formation of networks of neurons differentiated from hiPSCs (201B7) via long-term self-renewing neuroepithelial-like stem (lt-NES) cells. Expression of genes related to neural differentiation occurred more quickly in PS and/or 2% O2 than in DN and/or 20% O2, resulting in high responsiveness of neural cells to glutamate, N-methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), and ( S)-3,5-dihydroxyphenylglycine (an agonist for mGluR1/5), as revealed by calcium imaging assays. NMDA receptors, AMPA receptors, mGluR1, and mGluR5 were functionally validated by using the specific antagonists MK-801, NBQX, JNJ16259685, and 2-methyl-6-(phenylethynyl)-pyridine, respectively. Multielectrode array analysis showed that spontaneous firing occurred earlier in cells cultured in 2% O2 than in 20% O2. Optimization of O2 tension and culture medium for neural differentiation of hiPSCs can efficiently generate physiologically relevant cells for screening systems.
Assuntos
Técnicas de Cultura de Células/métodos , Diferenciação Celular/efeitos dos fármacos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Neurais/citologia , Meios de Cultivo Condicionados/farmacologia , Maleato de Dizocilpina/química , Humanos , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , N-Metilaspartato/química , Células-Tronco Neurais/efeitos dos fármacos , Neurônios/citologia , Neurônios/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Oxigênio/metabolismo , Consumo de Oxigênio/genéticaRESUMO
We used FM imaging to identify neurons that receive sensory feedback from the body wall in a circuit for octopamine (OA)-evoked rhythmic locomotion in the earthworm, Eisenia fetida. We visualized synapses in which postsynaptic neurons receive the sensory feedback, by using FM1-43 dye to label the synapses of both motor and sensory pathways that are associated with locomotion, then clearing the motor pathway synapse labeling, and finally identifying the target synapses by distinguishing physiologically functional synapses through destaining using a high-K(+) solution. A pair of synaptic regions associated with the sensory feedback was found to be located two or three cell body-widths away from the midline, between the anterior parts of the roots of the second lateral nerves (LNs) at the segmental ganglia (SGs). Using conventional intracellular recording and dye loading of the cell bodies surrounding these synaptic regions, we identified a pair of bilateral neurons with cell bodies larger than those of other cells in these regions, and named them "Oscillatory firing neurons Projecting to Peripheral nerves" (OPPs). These had a bipolar shape and projected neurites to the ipsilateral first and third LNs, fired rhythmically, and had a burst timing synchronized with the motor pattern bursts from the ipsilateral first LNs. Current injection into an OPP caused firing in the ipsilateral first LNs, supporting the hypothesis that OPPs functionally project to the peripheral nerves. OPPs also sent neurites to the adjacent anterior and posterior SGs, suggesting connections with the adjacent segments. We conclude that FM imaging can be used to identify neurons involved in specific functions, and that OPPs are the first neurons to be associated with OA-induced locomotion in the earthworm.