Embryonic Development of the Central Nervous System

Differentiation of peripheral sensory neurons from iPSCs derived from stem cells from human exfoliated deciduous teeth (SHED)

Peripheral nervous system (PNS) sensory alterations are present in several pathologies and syndromes. The use of induced pluripotent stem cell (iPSC) technology is an important strategy to produce sensory neurons in patients who are accomplished in terms of sensory symptoms. The iPSC technology relies on manipulating signaling pathways to resemble what occurs in vivo, and the iPSCs are known to carry a transcriptional memory after reprogramming, which can affect the produced cell. To this date, protocols described for sensory neuron production start using iPSCs derived from skin fibroblasts, which have the same ontogenetic origin as the central nervous system (CNS). Since it is already known that the cells somehow resemble their origin even after cell reprogramming, PNS cells should be produced from cells derived from the neural crest. This work aimed to establish a protocol to differentiate sensory neurons derived from stem cells from human exfoliated deciduous teeth (SHED) with the same embryonic origin as the PNS. SHED-derived iPSCs were produced and submitted to peripheral sensory neuron (PSN) differentiation. Our protocol used the dual-SMAD inhibition method, followed by neuronal differentiation, using artificial neurotrophic factors and molecules produced by human keratinocytes. We successfully established the first protocol for differentiating neural crest and PNS cells from SHED-derived iPSCs, enabling future studies of PNS pathologies.

Modulatory Activity of the Endocannabinoid System in the Development and Proliferation of Cells in the CNS

The Endocannabinoid System (ECS, also known as Endocannabinoidome) plays a key role in the function of the Central Nervous System, though the participation of this system on the early development - specifically in neuroprotection and proliferation of nerve cells - has been poorly studied. Here, we collect and describe evidence regarding how cannabinoid receptors CB1R and CB2R regulate several cell markers related to proliferation. While CB1R participates in the modulation of neuronal and glial proliferation, CB2R is involved in the proliferation of glial cells. The endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) exert significant effects on nerve cell proliferation. AEA generated during embryogenesis induces major effects on the differentiation of neuronal progenitor cells, whereas 2-AG participates in modulating cell migration events rather than affecting the neural proliferation rate. However, although the ECS has been demonstrated to participate in neuroprotection, more characterization on its role in neuronal and glial proliferation and differentiation is needed, especially in brain areas with recognized high neurogenesis rates. This has encouraged scientists to elucidate and propose specific mechanisms related with these cell proliferation mechanisms to better understand some neurodegenerative disorders such as Parkinson, Huntington and Alzheimer diseases, in which neuronal loss and poor neurogenesis are crucial factors for their onset and progression. In this review, we collect and present recent evidence published pointing to an active role of the ECS in the development and proliferation of nerve cells.

The role of microRNAs in neurodegenerative diseases: a review

MicroRNAs (miRNAs) are non-coding RNAs which are essential post-transcriptional gene regulators in various neuronal degenerative diseases and playact a key role in these physiological progresses. Neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, multiple sclerosis, and, stroke, are seriously threats to the life and health of all human health and life kind. Recently, various studies have reported that some various miRNAs can regulate the development of neurodegenerative diseases as well as act as biomarkers to predict these neuronal diseases conditions. Endogenic miRNAs such as miR-9, the miR-29 family, miR-15, and the miR-34 family are generally dysregulated in animal and cell models. They are involved in regulating the physiological and biochemical processes in the nervous system by targeting regulating different molecular targets and influencing a variety of pathways. Additionally, exogenous miRNAs derived from homologous plants and defined as botanmin, such as miR2911 and miR168, can be taken up and transferred by other species to be and then act analogously to endogenic miRNAs to regulate the physiological and biochemical processes. This review summarizes the mechanism and principle of miRNAs in the treatment of some neurodegenerative diseases, as well as discusses several types of miRNAs which were the most commonly reported in diseases. These miRNAs could serve as a study provided some potential biomarkers in neurodegenerative diseases might be an ideal and/or therapeutic targets for neurodegenerative diseases. Finally, the role accounted of the prospective exogenous miRNAs involved in mammalian diseases is described.

Mechanical forces in avian embryo development

Research using avian embryos has led to major conceptual advances in developmental biology, virology, immunology, genetics and cell biology. The avian embryo has several significant advantages, including ready availability and ease of accessibility, rapid development with marked similarities to mammals and a high amenability to manipulation. As mechanical forces are increasingly recognised as key drivers of morphogenesis, this powerful model system is shedding new light on the mechanobiology of embryonic development. Here, we highlight progress in understanding how mechanical forces direct key morphogenetic processes in the early avian embryo. Recent advances in quantitative live imaging and modelling are elaborating upon traditional work using physical models and embryo manipulations to reveal cell dynamics and tissue forces in ever greater detail. The recent application of transgenic technologies further increases the strength of the avian model and is providing important insights about previously intractable developmental processes.

Structural and functional consequences of PAX6 mutations in the brain: Implications for aniridia

The paired-box 6 (PAX6) gene encodes a highly conserved transcription factor essential for the proper development of the eye and brain. Heterozygous loss-of-function mutations in PAX6 are causal for a condition known as aniridia in humans and the Small eye phenotype in mice. Aniridia is characterized by iris hypoplasia and other ocular abnormalities, but recent evidence of neuroanatomical, sensory, and cognitive impairments in this population has emerged, indicating brain-related phenotypes as a prevalent feature of the disorder. Determining the neurophysiological origins of brain-related phenotypes in this disorder presents a substantial challenge, as the majority of extra-ocular traits in aniridia demonstrate a high degree of heterogeneity. Here, we summarize and integrate findings from human and rodent model studies, which have focused on neuroanatomical and functional consequences of PAX6 mutations. We highlight novel findings from PAX6 central nervous system studies in adult mammals, and integrate these findings into what we know about PAX6's role in development of the central nervous system. This review presents the current literature in the field in order to inform clinical application, discusses what is needed in future studies, and highlights PAX6 as a lens through which to understand genetic disorders affecting the human nervous system.

Neural stem cell differentiation into mature neurons: Mechanisms of regulation and biotechnological applications

The abilities of stem cells to self-renew and form different mature cells expand the possibilities of applications in cell-based therapies such as tissue recomposition in regenerative medicine, drug screening, and treatment of neurodegenerative diseases. In addition to stem cells found in the embryo, various adult organs and tissues have niches of stem cells in an undifferentiated state. In the central nervous system of adult mammals, neurogenesis occurs in two regions: the subventricular zone and the dentate gyrus in the hippocampus. The generation of the different neural lines originates in adult neural stem cells that can self-renew or differentiate into astrocytes, oligodendrocytes, or neurons in response to specific stimuli. The regulation of the fate of neural stem cells is a finely controlled process relying on a complex regulatory network that extends from the epigenetic to the translational level and involves extracellular matrix components. Thus, a better understanding of the mechanisms underlying how the process of neurogenesis is induced, regulated, and maintained will provide elues for development of novel for strategies for neurodegenerative therapies. In this review, we focus on describing the mechanisms underlying the regulation of the neuronal differentiation process by transcription factors, microRNAs, and extracellular matrix components.