Progress in application of adult endogenous neurogenesis in brain injury repair / 生理学报

Persistent neurogenesis exists in the subventricular zone (SVZ) of the ventricles and the subgranular zone (SGZ) of the dentate gyrus of the hippocampus in the adult mammalian brain. Adult endogenous neurogenesis not only plays an important role in the normal brain function, but also has important significance in the repair and treatment of brain injury or brain diseases. This article reviews the process of adult endogenous neurogenesis and its application in the repair of traumatic brain injury (TBI) or ischemic stroke, and discusses the strategies of activating adult endogenous neurogenesis to repair brain injury and its practical significance in promoting functional recovery after brain injury.

Cannabidiol prevents depressive-like behaviors through the modulation of neural stem cell differentiation / 医学前沿

Chronic stress impairs radial neural stem cell (rNSC) differentiation and adult hippocampal neurogenesis (AHN), whereas promoting AHN can increase stress resilience against depression. Therefore, investigating the mechanism of neural differentiation and AHN is of great importance for developing antidepressant drugs. The nonpsychoactive phytocannabinoid cannabidiol (CBD) has been shown to be effective against depression. However, whether CBD can modulate rNSC differentiation and hippocampal neurogenesis is unknown. Here, by using the chronic restraint stress (CRS) mouse model, we showed that hippocampal rNSCs mostly differentiated into astrocytes under stress conditions. Moreover, transcriptome analysis revealed that the FoxO signaling pathway was involved in the regulation of this process. The administration of CBD rescued depressive-like symptoms in CRS mice and prevented rNSCs overactivation and differentiation into astrocyte, which was partly mediated by the modulation of the FoxO signaling pathway. These results revealed a previously unknown neural mechanism for neural differentiation and AHN in depression and provided mechanistic insights into the antidepressive effects of CBD.

Environmental enrichment restores cognitive deficits induced by experimental childhood meningitis

Objective: To evaluate the influence of environmental enrichment (EE) on memory, cytokines, and brain-derived neurotrophic factor (BDNF) in the brain of adult rats subjected to experimental pneumococcal meningitis during infancy. Methods: On postnatal day 11, the animals received either artificial cerebrospinal fluid (CSF) or Streptococcus pneumoniae suspension intracisternally at 1 × 106 CFU/mL and remained with their mothers until age 21 days. Animals were divided into the following groups: control, control + EE, meningitis, and meningitis + EE. EE began at 21 days and continued until 60 days of age (adulthood). EE consisted of a large cage with three floors, ramps, running wheels, and objects of different shapes and textures. At 60 days, animals were randomized and subjected to habituation to the open-field task and the step-down inhibitory avoidance task. After the tasks, the hippocampus and CSF were isolated for analysis. Results: The meningitis group showed no difference in performance between training and test sessions of the open-field task, suggesting habituation memory impairment; in the meningitis + EE group, performance was significantly different, showing preservation of habituation memory. In the step-down inhibitory avoidance task, there were no differences in behavior between training and test sessions in the meningitis group, showing aversive memory impairment; conversely, differences were observed in the meningitis + EE group, demonstrating aversive memory preservation. In the two meningitis groups, IL-4, IL-10, and BDNF levels were increased in the hippocampus, and BDNF levels in the CSF. Conclusions: The data presented suggest that EE, a non-invasive therapy, enables recovery from memory deficits caused by neonatal meningitis. .

Alteraciones hipocampales y cambios cognitivos preceden al deposito de placas amiloides en un modelo murino de la enfermedad de Alzheimer

Existen múltiples evidencias de alteraciones neuronales y gliales en etapas avanzadas de la enfemedad de Alzheimer con abundantes depósitos cerebrales de beta amiloide, aunque hay pocos datos de cambios tempranos que podrían contribuir al desarrollo de la enfermedad. Evaluamos alteraciones morfológicas neuronales y gliales, y cambios cognitivos y emocionales tempranos en ratones transgénicos PDAPP-J20 (Tg), portadores del gen humano de APP (amyloid precursor protein) mutado, a los 5 meses de edad, aún sin depósitos amiloides en el hipocampo y con niveles bajos de péptidos amiloides cerebrales. Mediante inmunohistoquímica para NeuN, los Tg presentaron menor número de neuronas piramidales y granulares en el hipocampo, junto con un menor volumen de la estructura, en comparación con los controles no transgénicos. La neurogénesis se encontró afectada, evidenciada por reducido número de neuronas DCX+ en el giro dentado. En la región CA3, hubo una menor densidad de sinaptofisina sugiriendo alteraciones sinápticas entre neuronas granulares y piramidales, sin cambios en la densidad de espinas dendríticas en CA1. Utilizando microscopía confocal, observamos una disminución del número de astrocitos GFAP+ con una reducción de la complejidad celular, sugiriendo atrofia glial. Se detectó un déficit cognitivo (reconocimiento de localización novedosa de un objeto) y un aumento de la ansiedad (campo abierto) en los Tg, con aumento en los núcleos c-Fos+ en amígdala, evidenciando el papel de la emocionalidad en los inicios de la enfermedad. El estudio de las alteraciones iniciales en la enfermedad amiloide podría contribuir al desarrollo de métodos de diagnóstico temprano y de terapéutica preventiva.

Although there is strong evidence about neuronal and glial disturbances at advanced stages of Alzheimer’s disease, less attention has been directed to early, pre-amyloid changes that could contribute to the progression of the disease. We evaluated neuronal and glial morphological changes and behavioral disturbances in PDAPP-J20 transgenic (Tg) mice, carrying mutated human APP gene (amyloid precursor protein), at 5 months of age, before brain amyloid deposition occurs. Using NeuN immunohistochemistry we found decreased numbers of pyramidal and granular neurons in the hippocampus associated with a reduction of hippocampal volume in Tg mice compared with controls. Neurogenesis was impaired, evidenced by means of DCX immunohistochemistry in the dentate gyrus. In the CA3 region we found a decreased density of synaptophysin, suggesting synaptic disturbance, but no changes were found in CA1 synaptic spine density. Using confocal microscopy we observed decreased number and cell complexity of GFAP+ astrocytes, indicating potential glial atrophy. Cognitive impairment (novel location recognition test) and increased anxiety (open field) were detected in Tg mice, associated with more c-Fos+ nuclei in the amygdala, possibly indicating a role for emotionality in early stages of the disease. The study of early alterations in the course of amyloid pathology could contribute to the development of diagnostic and preventive strategies.

Neurorestoration Induced by Mesenchymal Stem Cells: Potential Therapeutic Mechanisms for Clinical Trials

Stem cells are emerging as therapeutic candidates in a variety of diseases because of their multipotent capacities. Among these, mesenchymal stem cells (MSCs) derived from bone marrow, umbilical cord blood or adipose tissue, comprise a population of cells that exhibit extensive proliferative potential and retain the ability to differentiate into multiple tissue-specific lineage cells including osteoblasts, chondrocytes, and adipocytes. MSCs have also been shown to enhance neurological recovery, although the therapeutic effects seem to be derived from an indirect paracrine effect rather than direct cell replacement. MSCs secrete neurotrophic factors, promote endogenous neurogenesis and angiogenesis, encourage synaptic connection and remyelination of damaged axons, decrease apoptosis, and regulate inflammation primarily through paracrine actions. Accordingly, MSCs may prevail as a promising cell source for cell-based therapy in neurological diseases.

Fast neutron irradiation deteriorates hippocampus-related memory ability in adult mice

Object recognition memory and contextual fear conditioning task performance in adult C57BL/6 mice exposed to cranial fast neutron irradiation (0.8 Gy) were examined to evaluate hippocampus-related behavioral dysfunction following acute exposure to relatively low doses of fast neutrons. In addition, hippocampal neurogenesis changes in adult murine brain after cranial irradiation were analyzed using the neurogenesis immunohistochemical markers Ki-67 and doublecortin (DCX). In the object recognition memory test and contextual fear conditioning, mice trained 1 and 7 days after irradiation displayed significant memory deficits compared to the sham-irradiated controls. The number of Ki-67- and DCX-positive cells decreased significantly 24 h post-irradiation. These results indicate that acute exposure of the adult mouse brain to a relatively low dose of fast neutrons interrupts hippocampal functions, including learning and memory, possibly by inhibiting neurogenesis.

Typical and atypical stem cells in the brain, vitamin C effect and neuropathology

Stem cells are considered a valuable cellular resource for tissue replacement therapies in most brain disorders. Stem cells have the ability to self-replicate and differentiate into numerous cell types, including neurons, oligodendrocytes and astrocytes. As a result, stem cells have been considered the "holy grail" of modern medical neuroscience. Despite their tremendous therapeutic potential, little is known about the mechanisms that regulate their differentiation. In this review, we analyze stem cells in embryonic and adult brains, and illustrate the differentiation pathways that give origin to most brain cells. We also evaluate the emergent role of the well known anti-oxidant, vitamin C, in stem cell differentiation. We believe that a complete understanding of all molecular players, including vitamin C, in stem cell differentiation will positively impact on the use of stem cell transplantation for neurodegenerative diseases.

Immunohistochemical study on the effect of soft diet and omega 3-fortified soft diet on neurogenesis in the rat dentate gyrus and the subventricular zone

Adult brain neurogenesis persists in the subventricular zone [SVZ] and in the subgranular zone [SGZ] of the dentate gyrus. Modulation of neurogenesis by diet is a mechanism by which nutrition affects memory, learning, and mood. To study the effect of the soft diet with or without omega 3 fatty acids on neurogenesis. Thirty weaned male albino rats [3 weeks] were divided into three groups. Group 1 [control group] were fed on hard diets, group 2 were fed on soft diets, and group 3 were fed on soft diets plus omega 3 fatty acids for 3 months. Nerve cell proliferation in the SVZ and the SGZ was detected immunohistochemically using thymidine analog bromodeoxyuridine [BrdU]. The results were statistically analyzed. In the dentate gyrus, there was a significant increase in the number of BrdU-positive cells in groups 1 and 3 compared with group 2. Meanwhile in the SVZ, there was a significant increase in the number of BrdU-positive cells in group 3 compared with group 1. In group 1, the newly formed cells in the SGZ reached the granular cell layer of the dentate gyrus. The newly formed cells in the SVZ reached the olfactory bulb [OB] after 2 weeks but failed to survive for 4 weeks in the OB. In group 2, few newly formed cells reached the granular cell layer of the dentate gyrus, but they failed to reach the OB. In group 3, the newly formed cells reached their destination in the granular cell layer of the dentate gyrus and the OB. In the OB, the cells succeeded to survive for 4 weeks and were incorporated among the granular cells of OB. Hard diet and omega 3-fortified soft diet had a stimulatory effect on the process of neurogenesis in the dentate gyrus. Meanwhile in the SVZ, fortified soft diet had more stimulatory effect on proliferation and improvement of the survival rate of the newly formed cells than the hard diet

Neurochemical phenotype and birthdating of specific cell populations in the chick retina

The chick embryo is one of the most traditional models in developing neuroscience and its visual system has been one of the most exhaustively studied. The retina has been used as a model for studying the development of the nervous system. Here, we describe the morphological features that characterize each stage of the retina development and studies of the neurogenesis period of some specific neurochemical subpopulations of retinal cells by using a combination of immunohistochemistry and autoradiography of tritiated-thymidine. It could be concluded that the proliferation period of dopaminergic, GABAergic, cholinoceptive and GABAceptive cells does not follow a common rule of the neurogenesis. In addition, some specific neurochemical cell groups can have a restrict proliferation period when compared to the total cell population.

O embrião de galinha é um dos mais tradicionais modelosde estudos da neurociência do desenvolvimento e seu sistema visual tem sido um dos mais exaustivamente estudado. Aretina tem sido utilizada como modelo para estudar o desenvolvimento do sistema nervoso. Aqui, nós descrevemos as características morfológicas que caracterizam cada estádio da retina em desenvolvimento e os estudos do período de neurogênese de algumas subpopulações de células neuroquímicamente específicas da retina usando uma combinação de imunohistoquímica e autoradiografia de timidina-tritiada. Conclui-se que o período de proliferação das células dopaminérgicas, GABAérgicas, colinoceptivas e GABAceptivas não segue uma regra comum. Além disso, alguns grupos celulares neuroquimicamente distintos podem ter um período de proliferaçãomais restrito quando comparado ao da população total destas células.

Rat Dlx5 is expressed in the subventricular zone and promotes neuronal differentiation

The molecular mechanisms and potential clinical applications of neural precursor cells have recently been the subject of intensive study. Dlx5, a homeobox transcription factor related to the distal-less gene in Drosophila, was shown to play an important role during forebrain development. The subventricular zone (SVZ) in the adult brain harbors the largest abundance of neural precursors. The anterior SVZ (SVZa) contains the most representative neural precursors in the SVZ. Further research is necessary to elucidate how Dlx5-related genes regulate the differentiation of SVZa neural precursors. Here, we employed immunohistochemistry and molecular biology techniques to study the expression of Dlx5 and related homeobox genes Er81 and Islet1 in neonatal rat brain and in in vitro cultured SVZa neural precursors. Our results show that Dlx5 and Er81 are also highly expressed in the SVZa, rostral migratory stream, and olfactory bulb. Islet1 is only expressed in the striatum. In cultured SVZa neural precursors, Dlx5 mRNA expression gradually decreased with subsequent cell passages and was completely lost by passage four. We also transfected a Dlx5 recombinant plasmid and found that Dlx5 overexpression promoted neuronal differentiation of in vitro cultured SVZa neural precursors. Taken together, our data suggest that Dlx5 plays an important role during neuronal differentiation.

Neurogenesis induced by seizures in the dentate gyrus is not related to mossy fiber sprouting but is age dependent in developing rats / A neurogênese induzida por crises no giro denteado não está relacionada ao brotamento de fibras musgosas, mas é dependente da idade, em ratos durante o desenvolvimento

Neurogenesis in the dentate gyrus (DG) has attracted attention since abnormal supragranular mossy fiber sprouting occurs in the same region, in temporal lobe epilepsy. Thus, we submitted developing rats to pilocarpine-induced status epilepticus (SE) to study the relationship between neurogenesis and mossy fiber sprouting. Groups were submitted to SE at: I-P9, II-P7, P8 and P9, III-P17 e IV-P21. Neurogenesis was quantified using BrdU protocol and confirmed through double staining, using neuronal pentraxin. Other animals were monitored by video system until P120 and their brain was studied (Timm and Nissl staining). The neurogenesis at P17 (p=0.007) and P21 (p=0.006) were increased. However, only P21 group showed recurrent seizures and the mossy fiber sprouting in the same region, during adult life, while P17 did not. Thus, our results suggest that neurogenesis is not related to mossy fiber sprouting neither to recurrent spontaneous seizures in pilocarpine model.

A neurogênese no giro dentado tem atraído atenção já que ela ocorre na mesma região do hipocampo que o brotamento das fibras musgosas, na epilepsia do lobo temporal. Assim, submetemos ratos em desenvolvimento ao status epilepticus induzido (SE) por pilocarpine. Grupos foram submetidos em I-P9, II-P7, P8, P9; III-P17 e IV-P21. A neurogênese foi observada usando o protocolo do BrdU e confirmada por dupla marcação com pentraxina neuronal. Outros animais foram monitorados até P120 e seus cérebros analisados (Nissl e Timm). A neurogênese nos grupos P17 (p=0,007) e P21 (p=0,006) aumentaram. Entretanto, o P21 apresentou crises espontâneas e brotamento de fibras musgosas, na mesma região onde ocorreu a neurogênese, enquanto o grupo P17 apresentou somente aumento na neurogênese. Assim, nossos resultados sugerem que o fenômeno da neurogênese não está relacionado com o brotamento de fibras musgosas nem com o aparecimento de crises espontâneas e recorrentes no modelo da pilocarpina.