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We sought to determine whether radiation to the colorectum had an impact on parameters of hippocampal neurogenesis and, if so, whether it could be modulated by a fiber-rich diet. Male C57BL/6J mice were fed a diet containing bioprocessed oat bran or a fiber-free diet, starting two weeks before colorectal irradiation with 4 fractions of 8 Gray or sham-irradiation. Diets were then continued for 1, 6 or 18 weeks, whereafter parameters of hippocampal neurogenesis were analyzed and correlated to serum cytokine levels. No statistically significant changes in neuronal markers or cell proliferation were found at one week post-irradiation. Six weeks post-irradiation there was a decreased cell proliferation in the subgranular zone that appeared slightly more pronounced in irradiated animals on a fiber-free diet and increased numbers of immature neurons per mm2 dentate gyrus in the irradiated mice, with a statistically significant increase in mice on a fiber-rich diet. Microglial abundancy was similar between all groups. 18 weeks post-irradiation, a fiber-free diet had reduced the number of immature neurons, whereas irradiation resulted in an increase. Despite this, the population of mature neurons was stable. Analysis of serum cytokines revealed a negative correlation between MIP1-α and the number of immature neurons one week after irradiation, regardless of diet. Our findings show that pelvic radiotherapy has the potential to cause a long-lasting impact on hippocampal neurogenesis, and dietary interventions may modulate this impact. More in-depth studies on the relationship between irradiation-induced intestinal injury and brain health are warranted. (Less)

Objective The purpose of the present study is to investigate whether angiopoietin-like 4 (ANGPTL4) can promote angiogenesis and neurogenesis following stroke, as well as to explore the potential underlying mechanisms. Methods ANGPTL4 (40 μg/kg) or a vehicle was administered via tail vein beginning 5 min prior to electrocoagulation-induced stroke in male C57/B6 J mice. Infarct volume was measured via Nissl staining at day 3 post-stroke. Angiogenesis, neurogenesis and activation of microglia were evaluated by immunofluorescence co-labelling bromodeoxyuridine (BrdU) with von Willebrand factor (vWF), doublecortin (DCX), neuronal nuclei (NeuN) and Iba1 at day 7 post-stroke. The levels of p-AKT, T-AKT, VEGF, MPO, Fas and FasL in the ipsilesional brain were detected by Western blot analysis at day 1 post-stroke. Results Compared with the Vehicle group, ANGPTL4 reduced infarct volume significantly at day 3 post-stroke. ANGPTL4 significantly increased the number of BrdU+, BrdU+/vWF+and BrdU+/DCX+ cells in the peri-infarct zone, subventricular zone and subgranular zone and inhibited BrdU+/Iba1+ cells in the peri-infarct zone at day 7 post-stroke. The level of p-AKT and the ratio of phospho-AKT to total-AKT in the ipsilesional brain were significantly elevated, the levels of MPO, Fas and FasL were significantly declined; however, there was no significant difference at day 1 post-stroke between the VEGF and total-AKT levels in both groups. Conclusions ANGPTL4 enhances angiogenesis and neurogenesis post-stroke by upregulating the phosphorylation of AKT, reduces neuronal death and inhibits inflammatory response, which resultes from the inhibition of FasL/Fas expression and its downstream pathway.

Despite the poor regenerative capacity of the adult central nervous system (CNS) in mammals, two distinct regions, subventricular zone (SVZ) and the subgranular zone (SGZ), continue to generate new functional neurons throughout life which integrate into the pre-existing neuronal circuitry. This process is not fixed but highly modulated, revealing many intrinsic and extrinsic mechanisms by which this performance can be optimized for a given environment. The capacity for self-renewal, proliferation, migration, and multi-lineage potency of neural stem cells (NSCs) underlines the necessity of controlling stem cell fate. In this context, the native and local microenvironment plays a critical role, and the application of this highly organized architecture in the CNS has been considered as a fundamental concept in the generation of new effective therapeutic strategies in tissue engineering approaches. The brain extracellular matrix (ECM) is composed of biomacromolecules, including glycosaminoglycans, proteoglycans, and glycoproteins that provide various biological actions through biophysical and biochemical signaling pathways. Herein, we review predominantly the structure and function of the mentioned ECM composition and their regulatory impact on multiple and diversity of biological functions, including neural regeneration, survival, migration, differentiation, and final destiny of NSCs.

Neurogenesis process in the chronic phase of ischemic stroke has become the focus of research on stroke treatment recently, mainly through the activation of related pathways to increase the differentiation of neural stem cells (NSCs) in the brain sub-ventricular zone (SVZ) and subgranular zone (SGZ) of hippocampal dentate gyrus (DG) areas into neurons, promoting neurogenesis. While there is still debate about the longevity of active adult neurogenesis in humans, the SVZ and SGZ have the capacity to upregulate neurogenesis in response to cerebral ischemia, which opens discussion about potential treatment strategies to harness this neuronal regenerative response. Wnt signaling pathway is one of the most important approaches potentially targeting on neurogenesis after cerebral ischemia, appropriate activation of which in NSCs may help to improve the sequelae of cerebral ischemia. Various therapeutic approaches are explored on preclinical stage to target endogenous neurogenesis induced by Wnt signaling after stroke onset. This article describes the composition of Wnt signaling pathway and the process of neurogenesis after cerebral ischemia, and emphatically introduces the recent studies on the mechanisms of this pathway for post-stroke neurogenesis and the therapeutic possibility of activating the pathway to improve neurogenesis after stroke.

Summary The primary cilium is the non-motile cilium present in most mammalian cell types and functions as an antenna for cells to sense signals. Ablating primary cilia in postnatal newborn neurons of the dentate gyrus (DG) results in both reduced dendritic arborization and synaptic strength, leading to hippocampal-dependent learning and memory deficits. Fragile X syndrome (FXS) is a common form of inheritance for intellectual disabilities with a high risk for autism spectrum disorders, and Fmr1 KO mice, a mouse model for FXS, demonstrate deficits in newborn neuron differentiation, dendritic morphology, and memory formation in the DG. Here, we found that the number of primary cilia in Fmr1 KO mice is reduced, specifically in the DG of the hippocampus. Moreover, this cilia loss was observed postnatally mainly in newborn neurons generated from the DG, implicating that these primary ciliary deficits may possibly contribute to the pathophysiology of FXS., Graphical Abstract, Highlights • Primary cilia are significantly reduced in the DG of Fmr1 KO mice • Fmr1 KO mice show age-dependent primary cilia deficits • Neuronal ciliogenesis defects are shown in the DG of Fmr1 KO mice • Primary cilia deficits are observed in newborn neurons from SGZ, but not from DNe, In this article, Lee and colleagues show that Fmr1 KO mice, a mouse model for fragile X syndrome, have primary cilia deficits in the dentate gyrus (DG) found specifically in newborn neurons originating from the subgranular zone (SGZ) of the DG, but not in other hippocampal brain regions or from neurons originating from the dentate neuroepithelium (DNe).

Summary Active neural stem cells (aNSCs) and quiescent neural stem cells (qNSCs) are two distinct subpopulations found in the adult hippocampal dentate gyrus (DG). However, to date, no cell surface marker has been established to identify and profile qNSCs in the adult hippocampus. Here, we identified expression of vascular cell adhesion molecule 1 (VCAM1) on the cell surface of NSCs, through which we identified a previously unrecognized subpopulation of NSCs in the adult mouse DG. Interestingly, most VCAM1-expressing NSCs were largely quiescent. By injecting virus into Ai14 reporter mice to conduct lineage tracing in the adult DG, we confirmed that VCAM1-expressing cells were multipotent and capable of generating neurons and astrocytes. Furthermore, depletion of Vcam1 during the embryonic or adult stage impaired spatial learning and memory in mice, accompanied by a reduced number of radial glial-like cells and proliferating NSCs in the subgranular zone of Vcam1 knockout mice., Graphical Abstract, Highlights • VCAM1 expresses on the cell surface of qNSCs in adult hippocampus • VCAM1+ cells were multipotent and capable of generating neurons and astrocytes • Loss of VCAM1+ cells impaired spatial learning and memory in mice., In this article, Hu and colleagues show that VCAM1 expresses on the cell surface of qNSCs in adult hippocampus. These VCAM1-expressing NSCs were multipotent and capable of generating neurons and astrocytes. Loss of VCAM1-expressing NSCs during the embryonic or adult stage impaired spatial memory in mice, which indicates that VCAM1+ NSCs in the SGZ were critical for spatial learning and memory.

The production of new neurons continues in the adult mammalian brain because of the sustained proliferation and differentiation of neural stem cells (NSCs) in neurogenic regions. The subventricular zone (SVZ), lining the lateral ventricle, and the subgranular zone (SGZ), which is in the dentate gyrus (DG) of the hippocampus, are the central regions of neurogenesis in the brain. Neurogenesis brings great hope for repairing a damaged brain and motivates researchers to detect the controlling signals of this process. Neurogenesis is regulated by intracellular and extracellular mechanisms that are influenced by neurogenic microenvironments. Recent experimental evidence suggests that the cholinergic system and nicotinic acetylcholine receptors (nAChRs) can directly regulate postnatal neurogenesis via specific mechanisms in these regions. In this review, we outline the cholinergic projections to the neurogenic niches and explain how the cholinergic system may regulate the formation of new neurons. We also discuss the intrinsic signaling pathways by which this system affects neurogenesis.

The hippocampus is characterized by the presence of life-long neurogenesis. To elucidate the molecular mechanism regulating hippocampal neurogenesis, we studied the functions of the chemorepellent Draxin in neuronal proliferation and differentiation in the postnatal dentate gyrus. The present in vivo cell labeling and fate tracking analyses revealed enhanced differentiation of hippocampal neural stem and progenitor cells (hNSPCs) in the subgranular zone (SGZ) of Draxin-deficient mice. We observed a reduction in the number of BrdU-pulse labeled or Ki-67 immunopositive SGZ cells in the mutant mice. However, Draxin deficiency did not affect cell cycle duration of SGZ cells. In situ hybridization analysis indicated that the receptor component of the canonical Wnt pathway, Lrp6, is expressed in SGZ cells, including Nestin and Sox2 double-positive hNSPCs. Taken together with the previous finding that Draxin interacts physically with Lrp6, we postulate that Draxin plays a pivotal role in the regulation of Wnt-driven hNSPC differentiation to modulate the rate of neuronal differentiation in the progenitor population.

Stroke consists of an abrupt reduction of cerebral blood flow resulting in hypoxia that triggers an excitotoxicity, oxidative stress, and neuroinflammation. After the ischemic process, neural precursor cells present in the subventricular zone of the lateral ventricle and subgranular zone of the dentate gyrus proliferate and migrate towards the lesion, contributing to the brain repair. The neurogenesis is induced by signal transduction pathways, growth factors, attractive factors for neuroblasts, transcription factors, pro and anti-inflammatory mediators and specific neurotransmissions. However, this endogenous neurogenesis occurs slowly and does not allow a complete restoration of brain function. Despite that, understanding the mechanisms of neurogenesis could improve the therapeutic strategies for brain repair. This review presents the current knowledge about brain repair process after stroke and the perspectives regarding the development of promising therapies that aim to improve neurogenesis and its potential to form new neural networks.

Exposure to commonly used anesthetics is associated with widespread neuroapoptosis in neonatal animals. Vulnerability of developing hippocampal dentate gyrus granule cells to anesthetic neurotoxicity peaks approximately 2 weeks after cell birth, as measured by bromodeoxyuridine birth dating, regardless of the age of the animal. The present study examined whether the vulnerable window can be further characterized by utilizing a transgenic approach. Proopiomelanocortin enhanced green fluorescent protein (POMC-EGFP) mice (postnatal day 21) were exposed to 3% sevoflurane for 6 h. Following exposure, cleaved caspase 3, expression of EGFP and differential maturational markers were quantified and compared with unanesthetized littermates. Electrophysiological properties of EGFP+ and EGFP− cells in the subgranular zone and the inner half of the granule cell layer were recorded by whole-cell patch-clamp. We found that sevoflurane significantly increased apoptosis of POMC-EGFP+ granule cells that accounted for approximate 1/3 of all apoptotic cells in dentate gyrus. Apoptotic EGFP− granule cells more frequently expressed the immature neuronal marker calretinin (75.4% vs 45.0%, P

Adult neurogenesis in mammals is a tightly regulated process where neural stem cells (NSCs), especially in the subgranular zone (SGZ) of the hippocampal dentate gyrus, proliferate and differentiate into new neurons that form new circuits or integrate into old circuits involved in episodic memory, pattern discrimination, and emotional responses. Recent evidence suggests that changes in the hyaluronan (HA)-based extracellular matrix of the SGZ may regulate neurogenesis by controlling NSC proliferation and early steps in neuronal differentiation. These studies raise the intriguing possibility that perturbations in this matrix, including HA accumulation with aging, could impact adult neurogenesis and cognitive functions, and that alterations to this matrix could be beneficial following insults to the central nervous system that impact hippocampal functions.

Neural proliferation in the dentate gyrus (DG) is closely linked with learning and memory, but the transcriptional programming that drives adult proliferation remains incompletely understood. Our lab previously elucidated the critical role of the transcription factor ΔFosB in the dorsal hippocampus (dHPC) in learning and memory, and the FosB gene has been suggested to play a role in neuronal proliferation. However, the subregion-specific and potentially cell-autonomous role of dHPC ΔFosB in neurogenesis-dependent learning has not been studied. Here, we crossed neurotensin receptor-2 (NtsR2) Cre mice, which express Cre within the subgranular zone (SGZ) of dHPC DG, with floxed FosB mice to show that knockout of ΔFosB in hippocampal SGZ neurons reduces antidepressant-induced neurogenesis and impedes hippocampus-dependent learning in the novel object recognition task. Taken together, these data indicate that FosB gene expression in SGZ is necessary for both hippocampal neurogenesis and memory formation.

Valproic acid (VPA) is widely used in the treatment of epilepsy. However, VPA has been revealed to impair memory of both humans and animals. The adverse effects of VPA are associated with reductions in hippocampal neurogenesis and memory. There are neuroprotective properties exerted by melatonin. Therefore, we investigated the protective effects of melatonin against the reductions of memory and neurogenesis caused by VPA. Male Sprague–Dawley rats received VPA (300 mg/kg) twice a day for 14 days, or melatonin (8 mg/kg/day) for 14 days, or co-treatment with VPA and melatonin for either 14 days (preventive and recovery groups) or 28 days (throughout group). Novel object location and novel object recognition tests were used to assess spatial memory and non-spatial memory, respectively. Proliferation, survival, and immature neurons in the subgranular zone (SGZ) were examined using immunohistochemistry. Rats showed decreases in proliferation, survival, and immature neurons in the SGZ, which were related to impairments in spatial and non-spatial memory. These behavioral changes were prevented by co-administration with melatonin. In addition, the decreasing of the hippocampal neurogenesis was improved to control levels, which had received co-administration with melatonin (preventive, recovery, and throughout). It is noteworthy that rats receiving melatonin alone showed a significant diversity of proliferation, survival and immature neurons compared to the control rats. These findings suggest that melatonin is able to prevent the spatial and non-spatial memory impairments and a reduction in hippocampal neurogenesis simultaneously induced by VPA. Our results provide a feasible way to prevent this loss using melatonin.

The aim of the study was to evaluate the impact of second generation antiepileptic drug levetiracetam (LEV) with arachidonyl-2′-chloroethylamide (ACEA) on proliferating neural precursor cells in mouse brain. Additionally, we established the relationship between treatment with ACEA in combination with LEV and hippocampal neurogenesis in mouse brain. All experiments were performed on male CB57/BL mice injected i.p. with LEV (10 mg/kg), ACEA (10 mg/kg) and PMSF (30 mg/kg) for 10 days. Experiments were provided in two stages: stage 1- an acute response of proliferating neural precursor cells to ACEA and LEV administration (Ki-67 staining), stage 2 – a long term response to ACEA and LEV administration (BrDU, NeuN, GFAP staining). Results indicate that ACEA + PMSF and ACEA + PMSF + LEV significantly increased the total number of Ki-67 positive cells comparing to the control group. PMSF and LEV administered alone and in combination had no significant impact on cell proliferation compared to the control group. Results from neurogenesis study indicated that ACEA + PMSF administered alone and in combination with LEV increased the total number of BrDU cells compared to the control group, although LEV on its own decreased the number of BrDU cells. Moreover, the combination of ACEA + PMSF + LEV significantly increased the total number of newborn neurons compared to the control group. In turn, LEV significantly decreased the process of neurogenesis. Astrocytes were considerably reduced in all treated groups as compare to the control mice. These data provide substantial evidence that LEV administered chronically decreases the proliferation and differentiation of newly born cells while combination of LEV + ACEA significantly increases the level of newborn neurons in the dentate subgranular zone.

Reactive oxygen species (ROS) modulate the growth of neural stem/precursor cells (NS/PCs) and participate in hippocampus-associated learning and memory. However, the origin of these regulatory ROS in NS/PCs is not fully understood. In the present study, we found that Nox4, a ROS-producing NADPH oxidase family protein, is expressed in primary cultured NS/PCs and in those of the adult mouse brain. Nox inhibitors VAS 2870 and GKT137831 or Nox4 deletion attenuated bFGF-induced proliferation of cultured NS/PCs, while lentivirus-mediated Nox4 overexpression increased the production of H2O2, the phosphorylation of Akt, and the proliferation of cultured NS/PCs. Nox4 did not significantly affect the potential of cultured NS/PCs to differentiate into neurons or astrocytes. The histological and functional development of the hippocampus appeared normal in Nox4-/- mice. Although pathological and functional damages in the hippocampus induced by the neurotoxin trimethyltin were not significantly different between wild-type and Nox4-/- mice, the post-injury reactive proliferation of NS/PCs and neurogenesis in the subgranular zone (SGZ) of the dentate gyrus were significantly impaired in Nox4-/- animals. Restoration from the trimethyltin-induced impairment in recognition and spatial working memory was also significantly attenuated in Nox4-/- mice. Collectively, our findings suggest that Nox4 participates in NS/PC proliferation and neurogenesis in the hippocampus following injury, thereby helping to restore memory function.

Mounting evidence in the literature suggests that RNA-RNA binding protein aggregations can disturb neuronal homeostasis and lead to symptoms associated with normal aging as well as dementia. The specific ablation of cyclin A2 in adult neurons results in neuronal polyribosome aggregations and learning and memory deficits. Detailed histologic and ultrastructural assays of aged mice revealed that post-mitotic hippocampal pyramidal neurons maintain cyclin A2 expression and that proliferative cells in the dentate subgranular zone express cyclin A2. Cyclin A2 loss early during neural development inhibited hippocampal development through canonical/cell-cycle mechanisms, including prolonged cell cycle timing in embryonic hippocampal progenitor cells. However, in mature neurons, cyclin A2 colocalized with dendritic rRNA. Cyclin A2 ablation in adult hippocampus resulted in decreased synaptic density in the hippocampus as well as in accumulation of rRNA granules in dendrite shafts. We conclude that cyclin A2 functions in a noncanonical/non-cell cycle regulatory role to maintain adult pyramidal neuron ribostasis.

Traumatic brain injury is an important cause of mortality and morbidity all over the world. After the initial injury there is a cascade of cellular and molecular events that ultimately lead to cell death. Therapies aim not only to counteract these mechanisms but also to replenish the lost cell population in order to achieve a better recovery. The adult mammal brain in not as plastic as the postnatal, but it has at least two neurogenic regions that maintains physiological functions in the brain; the subgranular zone of the dentate gyrus of the hippocampus, which produces neurons that integrate locally, and the subventricular zone (SVZ) of the lateral ventricles, that produces neuroblasts that migrate through the rostral migratory stream (RMS) to the olfactory bulbs. Brain injuries, as well as neurodegenerative diseases, induce the SVZ to respond by increasing cell proliferation and migration to the injured areas. Here we report that SVZ cells migrate to the injured cortex after traumatic brain injury in mice, and that the physiological RMS migration is not impaired. We also show that Prokineticin 2 (PROK2), a chemokine important for the olfactory bulb neurogenesis by promoting the directional migration of neuroblasts, is induced in the injured cortex. Using PROK2 receptor antagonist and recombinant PROK2 we show for the first time that PROK2 can directionally attract SVZ cells in vitro and in vivo. The data we present here links one more element of the inflammatory process, PROK2 secreted by microglia, to the attempt to regenerate an acutely injured mammalian cortex.AbbreviationsSGZsubgranular zoneSVZsubventricular zoneRMSrostral migratory streamPROK2Prokineticin 2

HIF-1α is a hypoxia-inducible protein that regulates many cellular processes, including neural stem cell maintenance. Previous work demonstrated constitutive stabilization of HIF-1α in neural stem cells (NSCs) of the adult mouse subventricular zone (SVZ) and hippocampal subgranular zone (SGZ). Genetic inactivation of NSC-encoded HIF-1α in the adult SVZ results in gradual loss of NSCs, but whether HIF-1α is required for the maintenance of SGZ hippocampal progenitors and adult hippocampal neurogenesis has not been determined. Here we tested the hypothesis that HIF-1α plays an essential role in the maintenance of adult hippocampal neurogenesis using Nestin-CreER(T2)/R26R-YFP/Hif1a(fl/fl) triple transgenic mice, in which HIF-1α was genetically inactivated in nestin(+) hippocampal progenitors and their downstream progeny following tamoxifen exposure. We found that disruption of HIF-1α gene expression resulted in a marked 50% reduction of adult-generated dentate granule cells (DGCs) that was highly correlated with impaired hippocampal function, as assessed using two behavioral assays of pattern discrimination. These behavioral tests included the A-B contextual fear-conditioning task and the trial-unique, delayed nonmatching-to-location (TUNL) touch-screen operant chamber task. Our findings identify HIF-1α as a novel regulator of adult hippocampal neurogenesis under non-pathological conditions, and underscore the importance of neurogenesis for pattern discrimination learning.

Adult hippocampal neurogenesis is implicated in antidepressant action in rodents and primates, yet relationships to human major depression (MDD) and antidepressant effects are unclear. In postmortem human hippocampus, we found doublecortin (DCX) protein and mRNA+ cells co-expressing neuronal but not astroglial or microglial markers. We defined neuroblasts as DCX+ cells located in the subgranular zone that co-expressed neuron-specific beta-tubulin (TUJ1) or lacked co-expression with neuronal nuclear marker (NeuN). Untreated MDD, regardless of clinical state, had fewer DCX-positive cells and neuroblasts in the rostral dentate gyrus compared with non-psychiatric controls. High-functioning, but not low-functioning, antidepressant-treated MDD, exhibited more DCX/TUJ1+ neuroblasts than untreated MDD. Groups did not differ in number of immature neurons, defined as DCX/NeuN+ cells in the inner granule cell layer. Deficient neuroblasts may be linked to hippocampal-dependent cognitive deficits in MDD. Similar neuroblast number between controls and higher-functioning antidepressant treated subjects warrants evaluation of neuroblasts as a treatment target.

Adult mammalian neural stem cells are unique because of their properties, such as differentiation capacity, self-renewal, quiescence, and also because they exist in specific niches, which are the subventricular zone (SVZ) and subgranular zone (SGZ) - the dentate gyrus of the hippocampus. SVZ is situated along the ependymal cell layer, dividing the ventricular area and subventricular zone. There are several sources of neural stem cells such as human embryonic stem cells, human fetal brain-derived neural stem/progenitor cells, human induced pluripotent stem cells, direct reprogrammed astrocytes. Stem cell sciences are a promising tool for research purposes as well as therapy. Induced pluripotent stem cells appear to be very useful for human neuron studies, allowing the creation of defined neuron populations, particularly for neurodevelopmental and neurodegenerative diseases as well as ischemic events. Neural stem cell sciences have a promising future in terms of stem cell therapy as well as research. There is, however, still a great need for further research to overcome obstacles.

Cilia are essential for sensory and motile functions across species. In humans, ciliary dysfunction causes "ciliopathies", which show severe developmental abnormalities in various tissues. Several missense mutations in intestinal cell kinase (ICK) gene lead to endocrine-cerebro-osteodysplasia syndrome or short rib-polydactyly syndrome, lethal recessive developmental ciliopathies. We and others previously reported that Ick-deficient mice exhibit neonatal lethality with developmental defects. Mechanistically, Ick regulates intraflagellar transport and cilia length at ciliary tips. Although Ick plays important roles during mammalian development, roles of Ick at the adult stage are poorly understood. In the current study, we investigated the Ick gene expression in adult mouse tissues. RT-PCR analysis showed that Ick is ubiquitously expressed, with enrichment in the retina, brain, lung, intestine, and reproductive system. In the adult brain, we found that Ick expression is enriched in the walls of the lateral ventricle, in the rostral migratory stream of the olfactory bulb, and in the subgranular zone of the hippocampal dentate gyrus by in situ hybridization analysis. We also observed that Ick staining pattern is similar to pachytene spermatocyte to spermatid markers in the mature testis and to an intestinal stem cell marker in the adult small intestine. These results suggest that Ick is expressed in proliferating regions in the adult mouse brain, testis, and intestine.

Previous studies have indicated that sleep deprivation negatively affects hippocampal neurogenesis, which may explain the reason for the relation between sleep loss and depression. Increasing evidence indicates that the hippocampus is anatomically and functionally segregated along a dorsolateral (cognitive function)/ventromedial (control for mood and stress response) axis. Thus, the present study was conducted to elucidate regional differences in the adverse effects of sleep deprivation on hippocampal neurogenesis. Male Sprague-Dawley rats were subjected to sleep deprivation using the "platform on the water" method for 24- or 72-h. Quantification of hippocampal cell proliferation and immature newborn neurons was stereologically estimated using immunostaining with Ki-67 and doublecortin (DCX), respectively, by optical fractionator method. A consecutive three days of sleep deprivation significantly reduced the density of Ki-67- and DCX-immunopositive cells both in the dorsal and ventral hippocampal subgranular zone and the decrease in DCX-labeled cells was more pronounced in the ventral hippocampus than in dorsal region. Our results indicate that prolonged sleep deprivation decreases hippocampal cell proliferation and neurogenesis in both the dorsal and ventral dentate gyrus. Future studies will be needed to clarify the impact of sleep deprivation-induced decreases in hippocampal neurogenesis on the development of depression.

Prenatal inflammation is associated with poor neurobehavioral outcomes in exposed offspring. A common route of exposure for the fetus is intrauterine infection, which is often associated with preterm birth. Hippocampal development may be particularly vulnerable to an inflammatory insult during pregnancy as this region remains highly neurogenic both prenatally and postnatally. These studies sought to determine if intrauterine inflammation specifically altered hippocampal neurogenesis and migration of newly produced granule neurons during the early postnatal period. Microglial and astroglial cell populations known to play a role in the regulation of postnatal neurogenesis were also examined. We show that intrauterine inflammation significantly reduced hippocampal neurogenesis between postnatal days 7 (P7) and P14 as well as decreased granule cell density at P28. Ectopic migration of granule cells was observed in LPS-exposed mice at P14, but not at P28. Intrauterine inflammation had no effect on hippocampal astrocyte or microglia density or on apoptosis rate at the postnatal time points examined. Thus, exposure to intrauterine inflammation disrupts early postnatal neurogenesis and leads to aberrant migration of newly born granule cells.

This study investigated the pattern of adult neurogenesis throughout the brains of three prosimian primate species using immunohistochemical techniques for endogenous markers of this neural process. Two species, Galago demidoff and Perodicticus potto, were obtained from wild populations in the primary rainforest of central Africa, while one species, Lemur catta, was captive-bred. Two brains from each species, perfusion-fixed with 4% paraformaldehyde, were sectioned (50 µm section thickness) in sagittal and coronal planes. Using Ki-67 and doublecortin (DCX) antibodies, proliferating cells and immature neurons were identified in the two canonical neurogenic sites of mammals, the subventricular zone of the lateral ventricle (SVZ) giving rise to the rostral migratory stream (RMS), and the subgranular zone of the dentate gyrus of the hippocampus. In addition a temporal migratory stream (TMS), emerging from the temporal horn of the lateral ventricle to supply the piriform cortex and adjacent brain regions with new neurons, was also evident in the three prosimian species. While no Ki-67-immunoreactive cells were observed in the cerebellum, DCX-immunopositive cells were observed in the cerebellar cortex of all three species. These findings are discussed in a phylogenetic context.

The subgranular zone of the dentate gyrus represents a niche in which radial glia (RG)-like cells generate new neurons throughout postnatal life in the mammalian brain. Previous data showed that RG-like cells are coupled through gap junction channels, primarily formed by connexin43 (Cx43) and Cx30, and that the expression of these proteins is required for adult neurogenesis in the hippocampus. However, their individual function and underlying mechanisms remain unclear. Here we demonstrate that Cx43, but not Cx30, is crucial for adult neurogenesis. To assess whether Cx43-dependent intercellular coupling between RG-like cells or rather channel-independent interactions of the protein regulate neurogenesis, mice bearing a Cx43 point mutation (Cx43G138R) in RG-like cells and protoplasmic astrocytes cells were employed, which was expected to cause channel closure without affecting the trafficking of the protein to the membrane. We confirmed the disruption of coupling between RG-like cells and astrocytes in the hippocampus of Cx43G138R mice. Proliferative activity and neurogenesis in the DG were significantly decreased in the mutant mouse line, indicating that functional Cx43 channels are essential for proper adult neurogenesis. The fate of proliferating cells in the DG was not affected by Cx43 mutation as revealed by 5-bromo-2-deoxyuridine (BrdU) incorporation assays. Together, these findings suggest that adult neurogenesis in the hippocampus does not require Cx30 but channel-dependent functions of Cx43.

Levetiracetam (LEV), a second-generation antiepileptic drug, is commonly prescribed to treat certain types of seizures. Few studies have investigated the effects of LEV on hippocampal neurogenesis and its related mechanisms. In the present study, we investigated the effects of LEV on cell proliferation and neuronal differentiation in the mouse hippocampal dentate gyrus (DG). We here demonstrate a dose-dependent increase in Ki-67-immunoreactive cells in the subgranular zone of the DG in LEV-treated mice, and doublecortin-immunoreactive cells were also significantly increased in the hippocampal DG of mice treated with LEV. The above results indicate that LEV could improve cell proliferation and neuroblast differentiation in the hippocampus. In addition, we also found that LEV treatment improved superoxide dismutase (SOD)2, catalase and Gpx-1 levels and increased phosphatidylinositol 3-kinase (PI3K) and phosphorylated Akt protein levels in the hippocampus. Further investigation of the molecular mechanisms underlying these effects revealed that PC12 cell was blocked by a pharmacological inhibitor of PI3K (LY294002), and that LEV treatment rapidly activated PI3K/Akt and SOD2, catalase and Gpx-1. In brief, our results indicate that LEV enhanced cell proliferation and neuroblast differentiation by increasing the expression of antioxidants and PI3K and the level of phosphorylated Akt in the mouse hippocampus.

Background Bao Yuan Capsule (BYC) is a patented Chinese medicinal formula for health promotion but its application for ischemic stroke remains unknown. In this study, we proposed the hypothesis that BYC could promote neurogenesis and neurological functional recovery through promoting mitochondrial function and activating PI3K/Akt signaling pathway. Methods We firstly performed chemical identification studies by using QIT-TOF-MS technology. Then, we investigated the effects of BYC (1 g/kg, 2 g/kg, 4 g/kg per day) on improving the recovery of the neurological functions in transient middle cerebral artery occlusion (MCAO) ischemic mice. Results We tentatively characterized 36 compounds from the BYC extractions. At dosage of 4 g/kg, BYC effectively improved locomotor ability, attenuated anxiety-like behaviors, and enhanced the exploring behaviors, learning and memory capability in the transient MCAO ischemic mice. BYC treatment promoted neural stem cell differentiations in the subventricular zone (SVZ) and subgranular zone (SGZ) of the MCAO mice. BYC also up-regulated the expression of Aconitase 2 (ACO2), Succinate dehydrogenase complex, subunit A (SDHA), phosphorylation of AMP-activated protein kinase (p-AMPK), protein kinase B (p-Akt) and glycogen synthase kinase 3β (p-GSK3β) in the hippocampus of the MCAO mice. BYC (200 µg/ml) significantly improved the mitochondrial functions in cultured mouse multipotent neural stem like C17.2 cells. BYC treatment also promoted neuronal differentiations in the C17.2 cells under oxygen-glucose deprivation (OGD) condition. The neurogenetic effects were abolished by co-treatments of ATP synthesis inhibitor oligomycin and PI3K/Akt inhibitor wortmannin. Moreover, Akt phosphorylation was dramatically reduced by oligomycin. Conclusion BYC could promote neurogenesis and neurological functional recovery in post ischemic brains by regulating the mitochondrial functions and Akt signaling pathway.

Drinking alcohol during pregnancy may cause fetal alcohol spectrum disorder. The present study investigated the effects of maternal oral ethanol (EtOH) exposure (0, 10, or 12.5 % in drinking water) from gestational day 6 until day 21 post-delivery (weaning) on postnatal hippocampal neurogenesis at weaning and in adulthood on postnatal day 77 in rat offspring. At weaning, type-3 neural progenitor cells (NPCs) were decreased in the subgranular zone (SGZ), accompanied by Chrnb2 downregulation and Grin2b upregulation in the dentate gyrus (DG). These results suggested suppression of CHRNB2-mediated cholinergic signaling in γ-aminobutyric acid (GABA)ergic interneurons in the DG hilus and increased glutamatergic signaling through the NR2B subtype of N-methyl- d -aspartate (NMDA) receptors, resulting in NPC reduction. In contrast, upregulation of Chrna7 may increase CHRNA7-mediated cholinergic signaling in immature granule cells, and upregulation of Ntrk2 may cause an increase in somatostatin-immunoreactive (+) GABAergic interneurons, suggesting a compensatory response against NPC reduction. Promotion of SGZ cell proliferation increased type-2a NPCs. Moreover, an increase in calbindin- d -29 K+ interneurons and upregulation of Reln, Drd2, Tgfb2, Il18, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor subunit genes might participate in this compensatory response. In adulthood, reduction of FOS+ cells and downregulation of Fos and Arc suggested suppression of granule cell synaptic plasticity, reflecting upregulation of Tnf and downregulation of Cntf, Ntrk2, and AMPA-type glutamate receptor genes. In the DG hilus, gliosis and hyper-ramified microglia, accompanying upregulation of C3, appeared at weaning, suggesting contribution to suppressed synaptic plasticity in adulthood. M1 microglia increased throughout adulthood, suggesting sustained neuroinflammation. These results indicate that maternal EtOH exposure temporarily disrupts hippocampal neurogenesis and later suppresses synaptic plasticity. Induction of neuroinflammation might initially ameliorate neurogenesis (as evident by upregulation of Tgfb2 and Il18) but later suppress synaptic plasticity (as evident by upregulation of C3 at weaning and Tnf in adulthood).

Adult neurogenesis is the process of producing new neurons from neural stem cells (NSCs) for integration into the brain circuitry. Neurogenesis occurs throughout life in the ventricular-subventricular zone (V-SVZ) of the lateral ventricle and the subgranular zone (SGZ) of the hippocampal dentate gyrus. However, during aging, NSCs and their progenitors exhibit reduced proliferation and neuron production, which is thought to contribute to age-related cognitive impairment and reduced plasticity that is necessary for some types of brain repair. In this review, we describe NSCs and their niches during tissue homeostasis and how they undergo age-associated remodeling and dysfunction. We also discuss some of the functional ramifications in the brain from NSC aging. Finally, we discuss some recent insights from interventions in NSC aging that could eventually translate into therapies for healthy brain aging.

Restoration of learning and memory deficits following traumatic brain injury (TBI) is attributed, in part, to enhanced neural stem/progenitor cell (NSPCs) function. Recent findings suggest gap junction (GJ)-associated connexin 43 (Cx43) plays a key role in the cell cycle regulation and function of NSPCs and is modulated following TBI. Here, we demonstrate that Cx43 is up-regulated in the dentate gyrus following TBI and is expressed on vimentin-positive cells in the subgranular zone. To test the role of Cx43 on NSPCs, we exposed primary cultures to the alpha-connexin Carboxyl Terminal (alpha CT1) peptide which selectively modulates GJ-associated Cx43. Treatment with alpha CT1 substantially reduced proliferation and increased caspase 3/7 expression on NSPCs in a dose-dependent manner. alpha CT1 exposure also reduced overall expression of Cx43 and phospho (p)-Serine368. These findings demonstrate that Cx43 positively regulates adult NPSCs; the modulation of which may influence changes in the dentate gyrus following TBI. VT's Institute of Critical Technology and Science; Virginia Maryland College of Veterinary Medicine; [R01 NS096281]; [NS096281]; [R15 NS081623] The authors would like to thank VT-IMSD Programs for student support (K.M.G.). This work was supported by R01 NS096281 (MHT), diversity supplement NS096281 (MHT, KG), R15 NS081623 (MHT) and VT's Institute of Critical Technology and Science. We recognize the Virginia Maryland College of Veterinary Medicine for student and financial support. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or any other funding agency.

Rats of OXYS strain are characterized by genetically defined accelerated senescence. Ceftriaxone (CEF) exerts neuroprotective effects by decreasing the excitotoxicity and activation of antioxidant system. Here, we studied the effects of CEF (50 or 100 mg/kg/day, i.p., 36 days) on cognitive and neuronal deficits in 5-month-old OXYS rats. Chronic CEF administration in a dose of 100 mg/kg partially inhibited impairments of movement and restored the deficit in the novel object recognition in OXYS rats. Neuromorphologically, control OXYS rats exhibited a lowered neuronal density in the hippocampal CA1 area and there was a tendency to decrease in the substantia nigra pars compacta compared to Wistar controls. Both doses of CEF increased the density of pyramidal neurons in the CA1 area in OXYS rats. Control OXYS rats demonstrated a tendency to lower tyrosine hydroxylase (TH) immunoreactivity in the striatum compared with Wistar rats, while CEF treatment at a dose of 50 mg/kg significantly augmented this parameter. In control OXYS rats, the levels of neurogenesis in the subgranular zone of the dentate gyrus of the hippocampus were significantly higher than in Wistar rats indicating compensatory processes that probably prevented the further induction of neurogenesis by CEF. Restoration of the recognition function and neuronal density in the CA1 area in OXYS rats after CEF treatment might be related to activation of the mechanisms that provide survival of newborn and mature neurons. The data suggested CEF as a promising pharmacological tool for the prevention of cognitive decline at accelerated aging.

Summary BACE1 is validated as Alzheimer's β-secretase and a therapeutic target for Alzheimer's disease. In examining BACE1-null mice, we discovered that BACE1 deficiency develops abnormal clusters of immature neurons, forming doublecortin-positive neuroblasts, in the developing dentate gyrus, mainly in the subpial zone (SPZ). Such clusters were rarely observed in wild-type SPZ and not reported in other mouse models. To understand their origins and fates, we examined how neuroblasts in BACE1-null SPZ mature and migrate during early postnatal development. We show that such neuroblasts are destined to form Prox1-positive granule cells in the dentate granule cell layer, and mainly mature to form excitatory neurons, but not inhibitory neurons. Mechanistically, higher levels of reelin potentially contribute to abnormal neurogenesis and timely migration in BACE1-null SPZ. Altogether, we demonstrate that BACE1 is a critical regulator in forming the dentate granule cell layer through timely maturation and migration of SPZ neuroblasts., Graphical Abstract, Highlights • BACE1 deficiency causes abnormal neuronal clusters retained in the mouse SPZ • Mis-migrated neural progenitor cells in the SPZ are destined to form granule cells • Such neural progenitor cells form excitatory neurons but not inhibitor neurons • Elevated levels of reelin contribute to abnormal neuronal maturation and migration, In this article, Yan and colleagues show that BACE1 is required for the proper formation of the granule cell layer. BACE1 deficiency in mice induces retention of clustered doublecortin-positive neuroblasts in the subpial zone (SPZ) and marginal zone (MZ). Upregulation of reelin in Cajal-Retzius cells likely causes timely migration of neuroblasts in SPZ/MZ to form Prox1-positive granule cells.

Ketamine is commonly used for anesthesia in pediatric patients. Recent studies indicated that ketamine exposure in the developing brain can induce neuroapoptosis and disturb normal neurogenesis, which will result in long-lasting cognitive impairment. Minocycline exerts neuroprotection against a wide range of toxic insults in neurodegenerative disease models. In the present study, we investigated whether the disturbed neurogenesis and behavioral deficits after ketamine neonatal exposure could be alleviated by minocycline. Postnatal day (PND)7 Sprague–Dawley rat pups randomly received either normal saline, ketamine, or minocycline 30 min prior to ketamine administration, respectively. The rats were decapitated at PND14 for the detection of neurogenesis in the subventricular zone (SVZ) and subgranular zone (SGZ) of the hippocampus by immunostaining. The protein expression of p-Akt, p-GSK-3β in the SVZ and SGZ at 12 h after anesthesia, PND10 and PND14 were assessed by western blotting analysis. At PND 42-47, spatial learning and memory abilities were measured by the Morris water maze in all groups. Our data showed that ketamine exposure in neonatal rats resulted in neurogenetic damage and persistent cognitive deficits, and that pretreatment with minocycline eliminated the brain development damage and improved the behavioral function in adult rats. Moreover, the protection of minocycline is associated with the PI3K/Akt signaling pathway.

The effect of acute irradiation with 5Gy or fractionated exposure with 0.5Gy continuously for 10days (a total dose of 5Gy) was evaluated in an immature BALB/c mouse model. Radioprotective effect of ursolic acid (at 25mg/kg/daily administered 1h after acute or each of fractionated irradiations, and continuously for 30days) was also investigated. We found that both acute and fractionated irradiation at a total dose of 5Gy did not induce any mortality within 30days after exposure to postnatal day 26 (P26) BALB/c mice, but reduced animal weigh gain in the first few weeks. At 90days after irradiation, the weight of animals with acute irradiation was still significantly lower than the control group; no significant difference though was observed for those fractionatedly exposed mice compared to the control group. Behavioral tests indicated that acute irradiation at 5Gy induced deficits in learning and memory in the contextual fear conditioning test. The memory for novel object recognition was also impaired. Similar changes were not observed in mice with fractionated irradiation. Immunohistochemical study demonstrated clearly that acute and fractionated irradiations induced impairment of neurogenesis in the subgranular zone (SGZ) of the dentate gyrus although fractionated exposure induced much lesser loss of newly generated neurons. Ursolic acid administered at 25mg/kg/daily for 30days after irradiation greatly improved acute irradiation-induced deficits in contextual learning and memory and in novel object recognition memory although it exacerbated radiation-induced reduction of neurogenesis in SGZ.

Ischemic stroke is a devastating condition with few therapeutic interventions available. The neuroprotective compound P7C3-A20 inhibits mature neuronal cell death while also increasing the net magnitude of postnatal neurogenesis in models of neurodegeneration and acute injury. P7C3 compounds enhance flux of nicotinamide adenine dinucleotide (NAD) in mammalian cells, a proposed therapeutic approach to treating cerebral ischemia. The effectiveness of P7C3-A20 treatment on chronic histopathological and behavioral outcomes and neurogenesis after ischemic stroke has not previously been established. Here, a transient middle cerebral artery occlusion in rats was followed by twice daily injection of P7C3-A20 or vehicle for 7days. P7C3-A20-treated rats performed significantly better than vehicle-treated controls in sensorimotor cylinder and grid-walk tasks, and in a chronic test of spatial learning and memory. These behavioral improvements with P7C3-A20 treatment were correlated with significantly decreased cortical and hippocampal atrophy, and associated with increased neurogenesis in the subventricular zone and hippocampal dentate gyrus subgranular zone. Furthermore, cerebral ischemia significantly reduced NAD in the cortex but P7C3-A20 treatment restored NAD to sham levels. Thus, P7C3-A20 treatment mitigates neurodegeneration and augments repair in the brain after focal ischemia, which translates into chronic behavioral improvement. This suggests a new therapeutic approach of using P7C3 compounds to safely augment NAD and thereby promote two independent processes critical to protecting the brain from ischemic stroke: mature neuron survival and postnatal neurogenesis throughout the post-ischemic brain.

Adult neurogenesis in the hippocampal subgranular zone (SGZ) is involved in learning and memory throughout life but declines with aging. Mice lacking the CD44 transmembrane receptor for the glycosaminoglycan hyaluronan (HA) demonstrate a number of neurological disturbances including hippocampal memory deficits, implicating CD44 in the processes underlying hippocampal memory encoding, storage, or retrieval. Here, we found that HA and CD44 play important roles in regulating adult neurogenesis, and we provide evidence that HA contributes to age-related reductions in neural stem cell (NSC) expansion and differentiation in the hippocampus. CD44-expressing NSCs isolated from the mouse SGZ are self-renewing and capable of differentiating into neurons, astrocytes, and oligodendrocytes. Mice lacking CD44 demonstrate increases in NSC proliferation in the SGZ. This increased proliferation is also observed in NSCs grown in vitro, suggesting that CD44 functions to regulate NSC proliferation in a cell-autonomous manner. HA is synthesized by NSCs and increases in the SGZ with aging. Treating wild type but not CD44-null NSCs with HA inhibits NSC proliferation. HA digestion in wild type NSC cultures or in the SGZ induces increased NSC proliferation, and CD44-null as well as HA-disrupted wild type NSCs demonstrate delayed neuronal differentiation. HA therefore signals through CD44 to regulate NSC quiescence and differentiation, and HA accumulation in the SGZ may contribute to reductions in neurogenesis that are linked to age-related decline in spatial memory.

Myricitrin (MYR) is a natural flavonoid that inhibits nitric oxide (NO) transmission and has an atypical antipsychotic-like profile in animal models. Considering that several NO inhibitors exert antidepressant-like effects, the present study evaluated the antidepressant-like effect of MYR (3–30 mg/kg) in the tail suspension test (TST). Because of the putative relationship between adult neurogenesis and antidepressant activity, we also assessed cell proliferation, survival, and differentiation in adult neurogenic niches, including the subgranular zone (SGZ) and subventricular zone (SVZ). Similar to the positive control imipramine (IMI; 10 mg/kg), repeated treatment with 10 mg/kg MIR but not acute treatment reduced immobility time in the TST, indicating an antidepressant-like effect. No effect on general motor activity was observed. Myricitrin also facilitated cell proliferation in the SGZ of the hippocampal dentate gyrus and SVZ. In the SGZ, MYR increased the number of doublecortin- and 5-bromo-2′-deoxyuridine/neuronal nuclei-positive cells. Our results suggest that MYR facilitates hippocampal neurogenesis, which might contribute to its antidepressant-like effect and atypical antipsychotic-like profile.

Adult hippocampal neurogenesis involves proliferation, survival, differentiation and integration of newborn neurons into pre-existing neuronal networks. Although its functional significance in the central nervous system (CNS) has not comprehensively elucidated, adult neurogenesis has been attributed a role in cognition, learning and memory. There is a growing body of evidence that CNS resident as well as peripheral immune cells participate in regulating hippocampal adult neurogenesis. Microglial cells are closely associated with neural stem/progenitor cell (NSPC) in the neurogenic niche engaged in a bidirectional communication with neurons, which may be important for adult neurogenesis. Microglial and neuronal crosstalk is mediated in part by CX3CL1/CX3CR1 signaling and a disruption in this pathway has been associated with impaired neurogenesis. It has been also reported that microglial neuroprotective or neurotoxic effects in adult neurogenesis occur in a context-dependent manner. Apart from microglia other brain resident and peripheral immune cells including pericytes, perivascular macrophages, mast cells and T-cells also modulate this phenomenon. It is worth mentioning that under some physiological circumstances such as normal aging there is a significant decrease in hippocampal neurogenesis. A role for innate and adaptive immune system in adult neurogenesis has been also reported during aging. Here, we review the current evidence regarding neuro-immune interactions in the regulation of neurogenesis under distinct conditions, including aging.

Episodes of cerebral hypoxia/ischemia increase the risk of dementia, which is associated with impaired learning and memory. Previous studies in rodent models of dementia indicated a favorable effect of the hypoxia-inducible factor (HIF) targets VEGF (vascular endothelial growth factor) and erythropoietin (Epo). In the present study we thus investigated whether activation of the entire adaptive HIF pathway in neurons by cell-specific deletion of the HIF suppressor prolyl-4-hydroxylase 2 (PHD2) improves cognitive abilities in young (3months) and old (18-28months) mice suffering from chronic brain hypoperfusion. Mice underwent permanent occlusion of the left common carotid artery, and cognitive function was assessed using the Morris water navigation task. Under conditions of both normal and decreased brain perfusion, neuronal PHD2 deficiency resulted in improved and faster spatial learning in young mice, which was preserved to some extent also in old animals. The loss of PHD2 in neurons resulted in enhanced hippocampal mRNA and protein levels of Epo and VEGF, but did not alter local microvascular density, dendritic spine morphology, or expression of synaptic plasticity-related genes in the hippocampus. Instead, better cognitive function in PHD2 deficient animals was accompanied by an increased number of neuronal precursor cells along the subgranular zone of the dentate gyrus. Overall, our current pre-clinical findings indicate an important role for the endogenous oxygen sensing machinery, encompassing PHDs, HIFs and HIF target genes, for proper cognitive function. Thus, pharmacological compounds affecting the PHD-HIF axis might well be suited to treat cognitive dysfunction and neurodegenerative processes.

Zinc is a central actor in regulating stem cell proliferation and neurogenesis in the adult brain. High levels of vesicular zinc are found in the presynaptic terminals. It has been demonstrated that high levels of vesicular zinc are localized in the presynaptic terminals of the granule cells of the dentate gyrus (DG) and that neurogenesis occurs in the subgranular zone (SGZ). Furthermore, zinc chelation reduces hippocampal neurogenesis in pathological conditions such as hypoglycemia, epilepsy and traumatic brain injury. Here we test the effects of zinc plus cyclo-(His-Pro) (CHP) treatment on neurogenesis in the adult SGZ. In order to increase brain zinc, Sprague-Dawley (SD) rats, aged 5weeks, were given zinc plus CHP (ZC, 27mg/kg) orally available once per day for 2weeks. BrdU was intraperitoneally injected 2 times per day for 4 consecutive days starting 1week after initial ZC treatment. Neurogenesis was analyzed by BrdU, Ki67 and doublecortin (DCX) immunostaining. The number of progenitor cells and immature neurons were significantly increased in the DG following 2weeks of ZC treatment. Hippocampal vesicular zinc content was evaluated with TSQ staining. Vesicular TSQ fluorescent intensity was seen to increase in the mossy fiber area at 2weeks after ZC treatment. The present study demonstrates that zinc supplementation by ZC treatment increases hippocampal neurogenesis and levels of vesicular zinc. These findings provide evidence in support of the essential role of zinc in modulating hippocampal neurogenesis.

6-Propyl-2-thiouracil (PTU)-induced hypothyroidism disrupts neuronal/glial development. This study sought to identify the sensitive immunohistochemical parameters of developmental neurotoxicity (DNT) following PTU-exposure, as well as their responses in a 28-day toxicity study in adults. In the developmental exposure study, pregnant rats were treated with 0, 1, 3, and 10ppm PTU in drinking water from gestational day 6 to postnatal day (PND) 21 and pups were examined on PNDs 21 and 77. In the adult-stage exposure study, 5-week-old male rats were treated with 0, 0.1 and 10mg PTU/kg by oral gavage for 28 days. In the developmental exposure study on PND 21, there were fewer GFAP+, PAX6+, and DCX+ cells in the subgranular zone (SGZ) of the hippocampal dentate gyrus at ≥3 or 10ppm. Regarding synaptic plasticity-related molecules, there were fewer EPHA4+ and ARC+ cells in the dentate granule cell layer. Regarding GABAergic interneuron subpopulations, there were more RELN+, CALB2+, and SST+ cells and fewer PVALB+ cells in the dentate hilus. There were also differences in the numbers of RELN+, PVALB+, CALB2+, and NPY+ cells in the cerebral cortex, and RELN+, PVALB+, and SST+ cells in the cerebellar cortex. Most of these changes were sustained until PND 77. Following adult-stage exposure (10mg/kg), there were fewer SGZ DCX+ cells, but more RELN+ and SST+ cells in the dentate hilus. Results suggest that GABAergic interneuron populations in cortical tissues, hippocampal neurogenesis, and synaptic plasticity are sensitive to PTU-induced DNT during development. In contrast, only hippocampal neurogenesis was sensitive to adult-stage exposure.

Both developmental and postpubertal cuprizone (CPZ) exposure impairs hippocampal neurogenesis in rats. We previously found that developmental CPZ exposure alters the expression of genes related to neurogenesis, myelination, and synaptic transmission in specific brain regions of offspring. Here, we examined neuronal and glial toxicity profiles in response to postpubertal CPZ exposure by using expression microarray analysis in the hippocampal dentate gyrus, corpus callosum, cerebral cortex, and cerebellar vermis of 5-week-old male rats exposed to 0, 120, and 600mg/kg CPZ for 28days. Genes showing transcript upregulation were subjected to immunohistochemical analysis. We found transcript expression alterations at 600mg/kg for genes related to synaptic transmission, Ache and Prima1, and cell cycle regulation, Tfap4 and Cdkn1a, in the dentate gyrus, which showed aberrant neurogenesis in the subgranular zone. This dose downregulated myelination-related genes in multiple brain regions, whereas KLOTHO+ oligodendrocyte density was decreased only in the corpus callosum. The corpus callosum showed an increase in transcript levels for inflammatory response-related genes and in the number of CD68+ microglia, MT+ astrocytes, and TUNEL+ apoptotic cells. These results suggest that postpubertal CPZ exposure targets synaptic transmission and cell cycle regulation to affect neurogenesis in the dentate gyrus. CPZ suppressed myelination in multiple brain regions and KLOTHO-mediated oligodendrocyte maturation only in the corpus callosum. The increased number of CD68+ microglia, MT+ astrocytes, and TUNEL+ apoptotic cells in the corpus callosum may be involved in the induction of KLOTHO+ oligodendrocyte death and be a protective mechanism against myelin damage following CPZ exposure.

Several lines of evidence have consistently indicated that physical exercise has antidepressant effects by improving hippocampal function, although the signaling pathways underpinning these responses are not well established. Therefore, this study investigated the role of mechanistic target of rapamycin complex 1 (mTORC1) and fibronectin type III domain-containing protein 5 (FNDC5)/irisin signaling in the antidepressant-like effect of physical exercise. We showed that physical exercise (treadmill running - 45 min/day/5 days/week for 4 weeks) produced an antidepressant-like effect as indicated by a reduction on the immobility time in mice subjected to the forced swimming test (FST) without altering locomotor activity in the open field test (OFT). Rapamycin (a selective mTORC1 inhibitor, 0.2 nmol/site, i.c.v.) administration completely abolished the antidepressant-like effect of physical exercise in the FST, suggesting that mTORC1 activation plays a role for its behavioral effect. Accordingly, physical exercise increased the number of phosphorylated mTORC1 (Ser2448)-positive cells in the entire and ventral subgranular zone of the hippocampal dentate gyrus. Physical exercise was also effective in augmenting the hippocampal FNDC5/irisin immunocontent, but rapamycin administration did not alter this effect. Our results reinforce the notion that physical exercise exerts an antidepressant-like effect and identifies the mTORC1-mediated signaling pathway as a target for its behavioral effects. This study provides additional evidence that physical exercise increases hippocampal FNDC5/irisin immunocontent, but this effect seems to be independent on hippocampal mTORC1 activation. Altogether the results contribute to elucidate possible molecular targets implicated in the antidepressant effects of physical exercise and highlight the role of mTORC1 signaling for its behavioral response.

Koumine (KM) is a major alkaloid monomer in the traditional Chinese medicine herb Gelsemium elegans Benth that has exhibited therapeutic potential in clinical applications. However, the pharmacological toxicological mechanism of this drug has not been fully explored. The purpose of this study was to evaluate the impacts of KM administration at a therapeutic dose in offspring. On gestational day 0, mice were injected with KM once daily for 4 consecutive days. Male and female offspring were subjected to behavioral tests and neuropathological analyses from postnatal day 60. Prenatal KM exposure resulted in cognitive and memory impairments in the Morris water maze, Y-maze test, and novel object recognition test. The open field test and elevated plus maze test indicated that prenatal KM exposure induced anxiety-like behavior in offspring. Electrophysiological experiments demonstrated that KM exposure inhibited hippocampal long-term potentiation. Immunostaining for neurogenesis markers DCX and BrdU demonstrated that KM suppressed adult neurogenesis in the subgranular zone of the dentate gyrus. In addition, prenatal KM exposure induced a significant reduction in dendritic spine density in hippocampal neurons. Synaptic formation-related proteins were decreased in the KM group based on western blot. No sex differences in the effects of KM were observed. Collectively, our results indicate that prenatal KA exposure has detrimental neural effects on offspring. This study provides a preliminary preclinical toxicological assessment of the safety of KM use during pregnancy.

Objective Neurocognitive functioning (NCF) is an important component of quality of life (QoL) in glioma patients. The neurocognitive toxicity from irradiation of brain tumours may be related to damage to neural progenitor cells (NPC). The aim of our study was to assess the NCF in illiterate glioma patients. Methods This was a prospective study done in glioma patients admitted for adjuvant treatment. Illiterate and semiliterate post op glioma patients with ECOG PS ≤ 3 were included. Neurocognitive assessment was done using Addenbrooke's Cognitive Examination (ACE-III) questionnaire prior to the start of RT and at 6month and 12 month follow up. The scores were correlated to the doses to sub ventricular zone (SVZ) and sub granular zone (SGZ) regions. Results 20 patients were recruited.16 patients were illiterate and four patients were semiliterate. Median of the mean dose to the SVZ I/L (ipsilateral) was 48.5 Gy and SGZ I/L was 39.5 Gy. In patients who received ≤49 Gy mean dose to SVZ I/L, there was statistically significant improvement in memory, fluency, language and total ACE scores at six months. In patients with SGZ I/L mean dose ≤40 Gy, there was improvement in memory, language, and total ACE score at six months. Similar trend continued at 12 months follow up. Conclusions NCF assessment by ACE III questionnaire is a useful tool even in illiterate patients. Lower RT doses to the ipsilateral SVZ and SGZ showed significant improvement in total ACE scores at 6 months and improvement in specific domains at 6 and 12 months.

Objective Adult neurogenesis in the subgranular zone and subventricular zone is generally accepted, but its existence in other brain areas is still controversial. Circumventricular organs, such as the area postrema (AP) have recently been described as potential neurogenic niches in the adult brain. The AP is the major site of action of the satiating hormone amylin. Amylin has been shown to promote the formation of neuronal projections originating from the AP in neonatal rodents but the role of amylin in adult neurogenesis remains unknown. Methods To test this, we first performed an RNA-sequencing of the AP of adult rats acutely injected with either amylin (20 μg/kg), amylin plus the amylin receptor antagonist AC187 (500 μg/kg) or vehicle. Second, animals were subcutaneously equipped with minipumps releasing either amylin (50 μg/kg/day) or vehicle for 3 weeks to assess cell proliferation and differentiation with the 5′-bromo-2-deoxyuridine (BrdU) technique. Results Acute amylin injections affected genes involved in pathways and processes that control adult neurogenesis. Amylin consistently upregulated NeuroD1 transcript and protein in the adult AP, and this effect was blocked by the co-administration of AC187. Further, chronic amylin treatment increased the number of newly proliferated AP-cells and significantly promoted their differentiation into neurons rather than astrocytes. Conclusion Our findings revealed a novel role of the satiating hormone amylin in promoting neurogenesis in the AP of adult rats., Highlights • Acute amylin affected genes involved in pathways and processes that drive neurogenesis. • Chronic amylin increased the number of newly proliferating cells in the AP of adult rats. • Chronic amylin determined neuronal fate over astrocytes in the AP of adult rats.

Although previous research has demonstrated that traumatic brain injury (TBI) accelerates the proliferation of neural stem cells in dentate gyrus of the hippocampus, most of these newborn cells undergo apoptosis in a traumatic microenvironment. Thus, promoting the long-term survival of newborn cells during neurogenesis is a compelling goal for the treatment of TBI. In this study, we investigated whether mild hypothermia (MHT) therapy, which mitigates the multiple secondary injury cascades of TBI, enhances the survival of newborn cells. SD rats were subjected to unilateral fluid percussion injury and received MHT therapy for 4 h (33.5 °C). Bromodeoxyuridine (BrdU) was administered to label the mitotic cells. Spatial learning and memory were evaluated with the Morris water maze test. Brain sections were immunostained with antibodies against BrdU, DCX (a neuroblast marker) or NeuN (a mature neuron marker). The apoptosis levels in the dentate gyrus were examined with antibodies against the apoptotic proteins FAS, FASL, Bcl-2 and cleaved caspase 3. The results indicated that MHT could significantly prevent TBI-induced cognitive impairments. At 1 week after injury, the density of BrdU-immunoreactive cells significantly increased in both TBI and TBI + MHT rats. At 4 weeks after injury, the density of BrdU-positive cells further increased in TBI + MHT rats, whereas the density declined in the TBI rats. The density of DCX-positive cells in SGZ of the hippocampus at 1 week after injury in the TBI + MHT rats was significantly greater than in the TBI rats. Moreover, the density of NeuN-positive cells in the subgranular zone at 4 weeks after injury and in the granule cell layer at 7 weeks after injury was significantly increased in the TBI + MHT rats. The TBI + MHT rats displayed a lower level of apoptosis in the dentate gyrus compared with the TBI rats. These data indicate that TBI could only facilitate a burst of proliferation and short-term survival of newborn cells, whereas TBI + MHT could facilitate long-term survival and maturation of newborn cells through diminishing pro-apoptotic microenvironment. These results suggest that MHT-mediated neurogenesis may have an important therapeutic potential for the endogenous repair of TBI.

Thrombin-activated protease-activated receptor (PAR)-1 regulates the proliferation of neural cells following brain injury. To elucidate the involvement of PAR-1 in the neurogenesis that occurs in the adult hippocampus, we examined whether PAR-1 regulated the proliferation of neural stem/progenitor cells (NPCs) derived from the murine hippocampal dentate gyrus. NPC cultures expressed PAR-1 protein and mRNA encoding all subtypes of PAR. Direct exposure of the cells to thrombin dramatically attenuated the cell proliferation without causing cell damage. This thrombin-induced attenuation was almost completely abolished by the PAR antagonist RWJ 56110, as well as by dabigatran and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), which are selective and non-selective thrombin inhibitors, respectively. Expectedly, the PAR-1 agonist peptide (AP) SFLLR-NH2 also attenuated the cell proliferation. The cell proliferation was not affected by the PAR-1 negative control peptide RLLFT-NH2, which is an inactive peptide for PAR-1. Independently, we determined the effect of in vivo treatment with AEBSF or AP on hippocampal neurogenesis in the adult mouse. The administration of AEBSF, but not that of AP, significantly increased the number of newly-generated cells in the hippocampal subgranular zone. These data suggest that PAR-1 negatively regulated adult neurogenesis in the hippocampus by inhibiting the proliferative activity of the NPCs.

Following the postnatal decline of cell proliferation in the mammalian central nervous system, the adult brain retains progenitor cells with stem cell-like properties in the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampus. Brain injury can stimulate proliferation and redirect the migration pattern of SVZ precursor cells to the injury site. Sublethal exposure to the neurotoxicant trimethyltin (TMT) causes dose-dependent necrosis and apoptosis in the hippocampus dentate gyrus and increases SGZ stem cell proliferation to generate new granule cells. To determine whether SVZ cells also contribute to the repopulation of the TMT-damaged dentate gyrus, 6-8 week old male C3H mice were injected with the carbocyanine dye spDiI and bromodeoxyuridine (80mg/kg; ip.) to label ventricular cells prior to TMT exposure. The presence of labeled cells in hippocampus was determined 7 and 28days after TMT exposure. No significant change in the number of BrdU(+) and spDiI(+) cells was observed in the dentate gyrus 7days after TMT treatment. However, 28days after TMT treatment there was a 3-4 fold increase in the number of spDiI-labeled cells in the hippocampal hilus and dentate gyrus. Few spDiI(+) cells stained positive for the mature phenotypic markers NeuN or GFAP, suggesting they may represent undifferentiated cells. A small percentage of migrating cells were BrdU(+)/spDiI(+), indicating some newly produced, SVZ- derived precursors migrated to the hippocampus. Taken together, these data suggest that TMT-induced injury of the hippocampus can stimulate the migration of ventricular zone-derived cells to injured dentate gyrus.

Melatonin is involved in the regulation of hippocampal neuronal development during adulthood. Emerging evidence indicates that exogenous melatonin acts during different events of the neurogenic process and exerts antidepressant-like behavior in rodents. Thus, melatonin might act through different mechanism, including acting as an antioxidant, interacting with intracellular proteins and/or activating membrane receptors. The melatonin membrane receptors (MMRs; Mt1/Mt2) are distributed throughout the hippocampus with an interesting localization in the hippocampal neurogenic microenvironment (niche), suggesting the involvement of these receptors in the beneficial effects of melatonin on hippocampal neurogenesis and behavior. In this study, we analyzed the participation of MMRs in the baseline neurogenesis in C57BL/6 mice. To this end, we used a pharmacological approach, administering luzindole (10 mg/kg) for 14 days. We observed a decrease in the absolute number of doublecortin-positive cells (49%) without changes in either the dendrite complexity of mature doublecortin-cells or the number of apoptotic cells (TUNEL). However, after the chronic administration of luzindole, cell proliferation (Ki67) significantly decreased (36%) with increasing (>100%) number of neural stem cells (NSCs; GFAP + /Sox2 + ) in the subgranular zone of the dentate gyrus of the hippocampus. In addition, luzindole did not affect hopelessness-like behavior in the forced swim test (FST) or changes in the novelty suppressed feeding test (NST) after 14 days of treatment either neuronal activation in the dentate gyrus after FST. These results suggest that the MMRs are involved in the effects of endogenous melatonin to mediate the transition from NSCs and proliferative cells to the following developmental stages implicated in the hippocampal neurogenic process of adult female C57BL/6 mice.