scholarly journals Adult Neurogenesis: A Story Ranging from Controversial New Neurogenic Areas and Human Adult Neurogenesis to Molecular Regulation

2021 ◽  
Vol 22 (21) ◽  
pp. 11489
Author(s):  
Perla Leal-Galicia ◽  
María Elena Chávez-Hernández ◽  
Florencia Mata ◽  
Jesús Mata-Luévanos ◽  
Luis Miguel Rodríguez-Serrano ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Molecular Mechanisms ◽  
Adult Brain ◽  
Human Adult ◽  
Open Questions ◽  
Division Process ◽  
Technical Issues ◽  
Functional Relevance ◽  
Local Circuitry ◽  
The Brain

The generation of new neurons in the adult brain is a currently accepted phenomenon. Over the past few decades, the subventricular zone and the hippocampal dentate gyrus have been described as the two main neurogenic niches. Neurogenic niches generate new neurons through an asymmetric division process involving several developmental steps. This process occurs throughout life in several species, including humans. These new neurons possess unique properties that contribute to the local circuitry. Despite several efforts, no other neurogenic zones have been observed in many years; the lack of observation is probably due to technical issues. However, in recent years, more brain niches have been described, once again breaking the current paradigms. Currently, a debate in the scientific community about new neurogenic areas of the brain, namely, human adult neurogenesis, is ongoing. Thus, several open questions regarding new neurogenic niches, as well as this phenomenon in adult humans, their functional relevance, and their mechanisms, remain to be answered. In this review, we discuss the literature and provide a compressive overview of the known neurogenic zones, traditional zones, and newly described zones. Additionally, we will review the regulatory roles of some molecular mechanisms, such as miRNAs, neurotrophic factors, and neurotrophins. We also join the debate on human adult neurogenesis, and we will identify similarities and differences in the literature and summarize the knowledge regarding these interesting topics.

scholarly journals Effects of Brain Size on Adult Neurogenesis in Shrews

2021 ◽  
Vol 22 (14) ◽  
pp. 7664
Author(s):  
Katarzyna Bartkowska ◽  
Krzysztof Turlejski ◽  
Beata Tepper ◽  
Leszek Rychlik ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Subventricular Zone ◽  
Molecular Mechanisms ◽  
Brain Size ◽  
Hippocampal Formation ◽  
Small Animals ◽  
Suncus Murinus ◽  
The Brain ◽  
Neomys Fodiens ◽  
Migratory Stream

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.

Adult Neurogenesis: Lessons from Crayfish and the Elephant in the Room

2016 ◽  
Vol 87 (3) ◽  
pp. 146-155 ◽  
Author(s):  
Barbara S. Beltz ◽  
Georg Brenneis ◽  
Jeanne L. Benton
Keyword(s):  
Stem Cells ◽  
Immune System ◽  
Neural Stem Cells ◽  
Adult Neurogenesis ◽  
Adult Brain ◽  
Neural Precursor ◽  
Neural Precursors ◽  
Neurogenic Niche ◽  
Fetal Microchimerism ◽  
The Brain

The 1st-generation neural precursors in the crustacean brain are functionally analogous to neural stem cells in mammals. Their slow cycling, migration of their progeny, and differentiation of their descendants into neurons over several weeks are features of the neural precursor lineage in crayfish that also characterize adult neurogenesis in mammals. However, the 1st-generation precursors in crayfish do not self-renew, contrasting with conventional wisdom that proposes the long-term self-renewal of adult neural stem cells. Nevertheless, the crayfish neurogenic niche, which contains a total of 200-300 cells, is never exhausted and neurons continue to be produced in the brain throughout the animal's life. The pool of neural precursors in the niche therefore cannot be a closed system, and must be replenished from an extrinsic source. Our in vitro and in vivo data show that cells originating in the innate immune system (but not other cell types) are attracted to and incorporated into the neurogenic niche, and that they express a niche-specific marker, glutamine synthetase. Further, labeled hemocytes that undergo adoptive transfer to recipient crayfish generate cells in neuronal clusters in the olfactory pathway of the adult brain. These hemocyte descendants express appropriate neurotransmitters and project to target areas typical of neurons in these regions. These studies indicate that under natural conditions, the immune system provides neural precursors supporting adult neurogenesis in the crayfish brain, challenging the canonical view that ectodermal tissues generating the embryonic nervous system are the sole source of neurons in the adult brain. However, these are not the first studies that directly implicate the immune system as a source of neural precursor cells. Several types of data in mammals, including adoptive transfers of bone marrow or stem cells as well as the presence of fetal microchimerism, suggest that there must be a population of cells that are able to access the brain and generate new neurons in these species.

scholarly journals A Common Language: How Neuroimmunological Cross Talk Regulates Adult Hippocampal Neurogenesis

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Odette Leiter ◽  
Gerd Kempermann ◽  
Tara L. Walker
Keyword(s):  
Immune System ◽  
Adult Neurogenesis ◽  
Immune Cells ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Adult Hippocampal Neurogenesis ◽  
Normal Brain ◽  
Intrinsic Cues ◽  
Normal Brain Function ◽  
The Brain

Immune regulation of the brain is generally studied in the context of injury or disease. Less is known about how the immune system regulates the brain during normal brain function. Recent work has redefined the field of neuroimmunology and, as long as their recruitment and activation are well regulated, immune cells are now known to have protective properties within the central nervous system in maintaining brain health. Adult neurogenesis, the process of new neuron generation in the adult brain, is highly plastic and regulated by diverse extrinsic and intrinsic cues. Emerging research has shown that immune cells and their secreted factors can influence adult neurogenesis, both under baseline conditions and during conditions known to change neurogenesis levels, such as aging and learning in an enriched environment. This review will discuss how, under nonpathological conditions, the immune system can interact with the neural stem cells to regulate adult neurogenesis with particular focus on the hippocampus—a region crucial for learning and memory.

scholarly journals Neural stem cells-from quiescence to differentiation and potential clinical uses

2021 ◽  
Vol 4 (1) ◽  
pp. 23-41
Author(s):  
Alexandra-Elena Dobranici ◽  
Sorina Dinescu ◽  
Marieta Costache
Keyword(s):  
Stem Cells ◽  
Neural Stem Cells ◽  
Molecular Mechanisms ◽  
Adult Brain ◽  
Quiescent State ◽  
Multipotent Stem Cells ◽  
Pathological Conditions ◽  
Mature Neurons ◽  
Direct Cell ◽  
The Brain

Specialised cells of the brain are generated from a population of multipotent stem cells found in the forming embryo and adult brain after birth, called neural stem cells. They reside in specific niches, usually in a quiescent, non-proliferating state that maintains their reservoir. Neural stem cells are kept inactive by various cues such as direct cell-cell contacts with neighbouring cells or by soluble molecules that trigger intracellular responses. They are activated in response to injuries, physical exercise, or hypoxia condition, through stimulation of signaling pathways that are usually correlated with increased proliferation and survival. Moreover, mature neurons play essential role in regulating the balance between active and quiescent state by realising inhibitory or activating neurotransmitters. Understanding molecular mechanisms underlying neuronal differentiation is of great importance in elucidating pathological conditions of the brain and treating neurodegenerative disorders that until now have no efficient therapies.

scholarly journals The critical role of cyclin D2 in adult neurogenesis

2004 ◽  
Vol 167 (2) ◽  
pp. 209-213 ◽  
Author(s):  
Anna Kowalczyk ◽  
Robert K. Filipkowski ◽  
Marcin Rylski ◽  
Grzegorz M. Wilczynski ◽  
Filip A. Konopacki ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Adult Neurogenesis ◽  
Molecular Mechanisms ◽  
Regulatory Gene ◽  
Critical Role ◽  
Brain Structures ◽  
Adult Brain ◽  
Cyclin D2 ◽  
Genetic Ablation ◽  
Neuronal Precursors

Adult neurogenesis (i.e., proliferation and differentiation of neuronal precursors in the adult brain) is responsible for adding new neurons in the dentate gyrus of the hippocampus and in the olfactory bulb. We describe herein that adult mice mutated in the cell cycle regulatory gene Ccnd2, encoding cyclin D2, lack newly born neurons in both of these brain structures. In contrast, genetic ablation of cyclin D1 does not affect adult neurogenesis. Furthermore, we show that cyclin D2 is the only D-type cyclin (out of D1, D2, and D3) expressed in dividing cells derived from neuronal precursors present in the adult hippocampus. In contrast, all three cyclin D mRNAs are present in the cultures derived from 5-day-old hippocampi, when developmental neurogenesis in the dentate gyrus takes place. Thus, our results reveal the existence of molecular mechanisms discriminating adult versus developmental neurogeneses.

scholarly journals Brain-Derived Neurotrophic Factor and Its Potential Therapeutic Role in Stroke Comorbidities

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Wei Liu ◽  
Xiaohui Wang ◽  
Margaret O’Connor ◽  
Guan Wang ◽  
Fang Han
Keyword(s):  
Neurotrophic Factor ◽  
Molecular Mechanisms ◽  
Brain Derived Neurotrophic Factor ◽  
Therapeutic Strategies ◽  
Adult Brain ◽  
Human Society ◽  
Potential Therapeutic Role ◽  
To Receive ◽  
The Brain ◽  
Global Population

With the rise in the aging global population, stroke comorbidities have become a serious health threat and a tremendous economic burden on human society. Current therapeutic strategies mainly focus on protecting neurons from cytotoxic damage at the acute phase upon stroke onset, which not only is a difficult way to ameliorate stroke symptoms but also presents a challenge for the patients to receive effective treatment in time. The brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain, which possesses a remarkable capability to repair brain damage. Recent promising preclinical outcomes have made BDNF a popular late-stage target in the development of novel stroke treatments. In this review, we aim to summarize the latest progress in the understanding of the cellular/molecular mechanisms underlying stroke pathogenesis, current strategies and difficulties in drug development, the mechanism of BDNF action in poststroke neurorehabilitation and neuroplasticity, and recent updates in novel therapeutic methods.

scholarly journals Protective Effect of Antioxidants on Neuronal Dysfunction and Plasticity in Huntington’s Disease

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Thirunavukkarasu Velusamy ◽  
Archana S. Panneerselvam ◽  
Meera Purushottam ◽  
Muthuswamy Anusuyadevi ◽  
Pramod Kumar Pal ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Adult Neurogenesis ◽  
Adult Brain ◽  
Great Promise ◽  
Contributing Factors ◽  
Neurologic Disorders ◽  
Supportive Role ◽  
The Brain

Huntington’s disease (HD) is characterised by movement disorders, cognitive impairments, and psychiatric problems. The abnormal generation of reactive oxygen species and the resulting oxidative stress-induced mitochondrial damage in neurons upon CAG mutations in theHTTgene have been hypothesized as the contributing factors of neurodegeneration in HD. The potential use of antioxidants against free radical toxicity has been an emerging field in the management of ageing and many neurodegenerative disorders. Neural stem cells derived adult neurogenesis represents the regenerative capacity of the adult brain. The process of adult neurogenesis has been implicated in the cognitive functions of the brain and is highly modulated positively by different factors including antioxidants. The supportive role of antioxidants to reduce the severity of HD via promoting the functional neurogenesis and neuroprotection in the pathological adult brain has great promise. This review comprehends the recent studies describing the therapeutic roles of antioxidants in HD and other neurologic disorders and highlights the scope of using antioxidants to promote adult neurogenesis in HD. It also advocates a new line of research to delineate the mechanisms by which antioxidants promote adult neurogenesis in HD.

Neurogenesis-An Overview

2021 ◽  
Author(s):  
Blossom Samuel Affia
Keyword(s):  
Stem Cells ◽  
Neural Stem Cells ◽  
Adult Neurogenesis ◽  
Adult Brain ◽  
Long Time ◽  
The One ◽  
The Brain ◽  
Different Parts

Neurogenesis is a phenomenon that involves the formation of new neurons in the brain by neural stem cells (NSCs). Investigators have confirmed that neurogenesis occurs in discrete parts of the adult brain as opposed to the embryos [1]. However, this was not the case long time back. Researchers have always been interested in learning if humans or other large organisms could show regenerative properties like the one seen in specific small organisms which can regrow different parts of their own bodies [2]. If possible, this would lead to a new avenue in therapeutics as more scientists would try to stimulate regeneration to deal with injury or any harmful stimuli. Like mentioned previously, researchers were not convinced with this approach and deemed that there is no possibility of adult neurogenesis [3].

scholarly journals Adult Neurogenesis in the Drosophila Brain: The Evidence and the Void

2020 ◽  
Vol 21 (18) ◽  
pp. 6653
Author(s):  
Guiyi Li ◽  
Alicia Hidalgo
Keyword(s):  
Adult Neurogenesis ◽  
Genetic Manipulation ◽  
Brain Plasticity ◽  
Fruit Fly ◽  
Cell Number ◽  
Adult Brain ◽  
Proliferating Cells ◽  
Drosophila Brain ◽  
The Central Nervous System ◽  
The Brain

Establishing the existence and extent of neurogenesis in the adult brain throughout the animals including humans, would transform our understanding of how the brain works, and how to tackle brain damage and disease. Obtaining convincing, indisputable experimental evidence has generally been challenging. Here, we revise the state of this question in the fruit-fly Drosophila. The developmental neuroblasts that make the central nervous system and brain are eliminated, either through apoptosis or cell cycle exit, before the adult fly ecloses. Despite this, there is growing evidence that cell proliferation can take place in the adult brain. This occurs preferentially at, but not restricted to, a critical period. Adult proliferating cells can give rise to both glial cells and neurons. Neuronal activity, injury and genetic manipulation in the adult can increase the incidence of both gliogenesis and neurogenesis, and cell number. Most likely, adult glio- and neuro-genesis promote structural brain plasticity and homeostasis. However, a definitive visualisation of mitosis in the adult brain is still lacking, and the elusive adult progenitor cells are yet to be identified. Resolving these voids is important for the fundamental understanding of any brain. Given its powerful genetics, Drosophila can expedite discovery into mammalian adult neurogenesis in the healthy and diseased brain.

Neuroimaging and neurogenesis of depression

2011 ◽  
Vol 26 (S2) ◽  
pp. 2051-2051
Author(s):  
T. Frodl
Keyword(s):  
Molecular Mechanisms ◽  
Antidepressant Treatment ◽  
Structure And Function ◽  
Adult Brain ◽  
Brain Structure And Function ◽  
And Function ◽  
Fixed Structure ◽  
Neuroplastic Change ◽  
The Brain

IntroductionUntil only a few years ago, the adult brain was considered to be an organ with a fixed structure, unable to remodel or repair itself. Today, neuroscientists and neurobiologists use the term “neuroplasticity” to indicate an ability of some nervous system regions to change their structure, eventually altering their overall functionality.AimThe presentation reviews the implication for the conceptualization of and investigation of depression arising from neuroplastic change and neurogenesis in the brain.ResultsAnimal experimental and human studies have shown the effects of stress and depression to affect brain structure and function, e.g. of the hippocampus. Exercise, learning and antidepressant treatment was shown to have beneficial neuroplastic effects.DiscussionLong-term interventions should also target the molecular mechanisms linked with neuroplastic adaptive dysfunctions in the brain. Possibilities how psychotherapy and pharmacotherapy could achieve this aim will be discussed.

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