Number Of Neural Progenitors Research Articles

Stable Adult Hippocampal Neurogenesis in Cannabinoid Receptor CB2 Deficient Mice

The G-protein coupled cannabinoid receptor 2 (CB2) has been implicated in the regulation of adult neurogenesis in the hippocampus. The contribution of CB2 towards basal levels of proliferation and the number of neural progenitors in the subgranular zone (SGZ) of the dentate gyrus, however, remain unclear. We stained hippocampal brain sections of 16- to 17-week-old wildtype and CB2-deficient mice, for neural progenitor and immature neuron markers doublecortin (DCX) and calretinin (CR) and for the proliferation marker Ki67 and quantified the number of positive cells in the SGZ. The quantification revealed that CB2 deficiency neither altered overall cell proliferation nor the size of the DCX+ or DCX and CR double-positive populations in the SGZ compared to control animals. The results indicate that CB2 might not contribute to basal levels of adult neurogenesis in four-month-old healthy mice. CB2 signaling might be more relevant in conditions where adult neurogenesis is dynamically regulated, such as neuroinflammation.

Bioluminescence imaging visualizes osteopontin-induced neurogenesis and neuroblast migration in the mouse brain after stroke

BackgroundOsteopontin (OPN), an acidic phosphoglycoprotein, is upregulated in the brain after cerebral ischemia. We previously reported that OPN supports migration, survival, and proliferation of neural stem cells (NSC) in primary cell culture, as well as their differentiation into neurons. We here analyzed the effects of OPN on neuroblasts in vivo in the context of cerebral ischemia.MethodsTransgenic mice expressing luciferase under the control of the neuroblast-specific doublecortin (DCX)-promoter, allowing visualization of neuroblasts in vivo using bioluminescence imaging (BLI), were injected with OPN intracerebroventricularly while control mice were injected with vehicle buffer. To assess the effects of OPN after ischemia, additional mice were subjected to photothrombosis and injected with either OPN or vehicle.ResultsOPN enhanced the migration of neuroblasts both in the healthy brain and after ischemia, as quantified by BLI in vivo. Moreover, the number of neural progenitors was increased following OPN treatment, with the maximum effect on the second day after OPN injection into the healthy brain, and 14 days after OPN injection following ischemia. After ischemia, OPN quantitatively promoted the endogenous, ischemia-induced neuroblast expansion, and additionally recruited progenitors from the contralateral hemisphere.ConclusionsOur results strongly suggest that OPN constitutes a promising substance for the targeted activation of neurogenesis in ischemic stroke.

The loss of the kinases SadA and SadB results in early neuronal apoptosis and a reduced number of progenitors.

The neurons that form the mammalian neocortex originate from progenitor cells in the ventricular (VZ) and subventricular zone (SVZ). Newborn neurons are multipolar but become bipolar during their migration from the germinal layers to the cortical plate (CP) by forming a leading process and an axon that extends in the intermediate zone (IZ). Once they settle in the CP, neurons assume a highly polarized morphology with a single axon and multiple dendrites. The AMPK-related kinases SadA and SadB are intrinsic factors that are essential for axon formation during neuronal development downstream of Lkb1. The knockout of both genes encoding Sad kinases (Sada and Sadb) results not only in a loss of axons but also a decrease in the size of the cortical plate. The defect in axon formation has been linked to a function of Sad kinases in the regulation of microtubule binding proteins. However, the causes for the reduced size of the cortical plate in the Sada-/-;Sadb-/- knockout remain to be analyzed in detail. Here we show that neuronal cell death is increased and the number of neural progenitors is decreased in the Sada-/-;Sadb-/- CP. The reduced number of progenitors is a non-cell autonomous defect since they do not express Sad kinases. These defects are restricted to the neocortex while the hippocampus remains unaffected.

Modeling the behavior of human induced pluripotent stem cells seeded on melt electrospun scaffolds

BackgroundHuman induced pluripotent stem cells (hiPSCs) can form any tissue found in the body, making them attractive for regenerative medicine applications. Seeding hiPSC aggregates into biomaterial scaffolds can control their differentiation into specific tissue types. Here we develop and analyze a mathematical model of hiPSC aggregate behavior when seeded on melt electrospun scaffolds with defined topography.ResultsWe used ordinary differential equations to model the different cellular populations (stem, progenitor, differentiated) present in our scaffolds based on experimental results and published literature. Our model successfully captures qualitative features of the cellular dynamics observed experimentally. We determined the optimal parameter sets to maximize specific cellular populations experimentally, showing that a physiologic oxygen level (∼ 5%) increases the number of neural progenitors and differentiated neurons compared to atmospheric oxygen levels (∼ 21%) and a scaffold porosity of ∼ 63% maximizes aggregate size.ConclusionsOur mathematical model determined the key factors controlling hiPSC behavior on melt electrospun scaffolds, enabling optimization of experimental parameters.

Cyclosporine A-Mediated IL-6 Expression Promotes Neural Induction in Pluripotent Stem Cells.

Differentiation of pluripotent stem cells (PSCs) to neural lineages has gathered huge attention in both basic research and regenerative medicine. The major hurdle lies in the efficiency of differentiation and identification of small molecules that facilitate neurogenesis would partly circumvent this limitation. The small molecule Cyclosporine A (CsA), a commonly used immunosuppressive drug, has been shown to enhance in vivo neurogenesis. To extend the information to in vitro neurogenesis, we examined the effect of CsA on neural differentiation of PSCs. We found CsA to increase the expression of neural progenitor genes during early neural differentiation. Gene silencing approach revealed CsA-mediated neural induction to be dependent on blocking the Ca2+-activated phosphatase calcineurin (Cn) signaling. Similar observation with FK506, an independent inhibitor of Cn, further strengthened the necessity of blocking Cn for enhanced neurogenesis. Surprisingly, mechanistic insight revealed Cn-inhibitiondependent upregulation of IL-6 protein to be necessary for CsA-mediated neurogenesis. Together, these findings provide a comprehensive understanding of the role of CsA in neurogenesis, thus suggesting a method for obtaining large numbers of neural progenitors from PSCs for possible transplantation.

Brain size is controlled by the mammalian target of rapamycin (mTOR) in mice

The number of neurons in the brain is mostly determined by neural progenitor proliferation and neurogenesis during embryonic development. Increase in postnatal brain size is largely dependent on cellular volume changes. The mammalian target of rapamycin (mTOR) signaling has been associated with cell proliferation and size determination in a variety of cell types. The role of mTOR signaling in neural development has been increasingly pursued due to its association with neurodevelopmental disorders and cancers. Surprisingly, however, there has been lack of in vivo genetic evidence that defines mTOR functions in neural progenitors during progenitor self-renewal and subsequent brain formation. Here, we discuss our recent evidence that mTOR signaling is required for the establishment of normal brain size during development. Mice lacking mTOR show smaller brain and reduced numbers of neural progenitors and neurons. Additionally, mTOR interacts with the Wnt signaling pathway in the control of neural progenitors. Our study establishes the mTOR signal as a key regulator of an evolutionarily conserved cascade that is responsible for vertebrate brain size.

Effects of the flavonoid hesperidin in cerebral cortical progenitors in vitro: indirect action through astrocytes

Flavonoids are polyphenolic compounds that are integral components of the human diet, universally present as constituents of fruits and vegetables as well as plant-derived foods and beverages such as oil, tea, and red wine. The biological activities of flavonoids cover a very broad spectrum, from anticancer and antibacterial activities to inhibition of bone reabsorption and modulation of inflammatory response. Although emerging evidence has suggested that flavonoids might have an impact on brain pathology and aging, their role as a mediator in interactions between neurons and glial cells has been poorly explored. In the present work, we have performed a screening of flavonoid actions by analyzing the effects of hesperidin, quercetin and rutin on murine cerebral cortex astrocytes and neural progenitors. Treatment of astrocytes with flavonoids did not interfere with cell viability and proliferation. However a culture of neural progenitors with conditioned medium from hesperidin treated-astrocyte (H-CM) yielded produced a 41% and 25% increase in the number of neural progenitors and post-mitotic neurons, respectively. The H-CM effect was mainly due to modulation of neuronal progenitor survival. Pools of astrocyte and oligodendrocyte progenitors were not affected by H-CM (hesperidin), Q-CM (quercetin) and R-CM (rutin). Q-CM and R-CM did not increase neuronal population. These results suggest that H-CM might be composed by a new factor that could modulate neuroglial interactions during central nervous system development and opens the possibility for using flavonoids as new therapeutic strategies for neurodegenerative diseases.

Sonic Hedgehog Is Required for Progenitor Cell Maintenance in Telencephalic Stem Cell Niches

To directly test the requirement for hedgehog signaling in the telencephalon from early neurogenesis, we examined conditional null alleles of both the Sonic hedgehog and Smoothened genes. While the removal of Shh signaling in these animals resulted in only minor patterning abnormalities, the number of neural progenitors in both the postnatal subventricular zone and hippocampus was dramatically reduced. In the subventricular zone, this was partially attributable to a marked increase in programmed cell death. Consistent with Hedgehog signaling being required for the maintenance of stem cell niches in the adult brain, progenitors from the subventricular zone of floxed Smo animals formed significantly fewer neurospheres. The loss of hedgehog signaling also resulted in abnormalities in the dentate gyrus and olfactory bulb. Furthermore, stimulation of the hedgehog pathway in the mature brain resulted in elevated proliferation in telencephalic progenitors. These results suggest that hedgehog signaling is required to maintain progenitor cells in the postnatal telencephalon.