Neural Stem And Progenitor Cells Proliferation Research Articles

Pleiotrophin ameliorates age-induced adult hippocampal neurogenesis decline and cognitive dysfunction

Cognitive impairment has been associated with an age-related decline in adult hippocampal neurogenesis (AHN). The molecular basis of declining neurogenesis in the aging hippocampus remains to be elucidated. Here, we show that pleiotrophin (PTN) expression is decreased with aging in neural stem and progenitor cells (NSPCs). Mice lacking PTN exhibit impaired AHN accompanied by poor learning and memory. Mechanistically, we find that PTN engages with protein tyrosine phosphatase receptor type Z1 (PTPRZ1) to promote NSPC proliferation and differentiation by activating AKT signaling. PTN overexpression or pharmacological activation of AKT signaling in aging mice restores AHN and alleviates relevant memory deficits. Importantly, we also find that PTN overexpression improves impaired neurogenesis in senescence-accelerated mouse prone 8 (SAMP8) mice. We further confirm that PTN is required for enriched environment-induced increases in AHN. These results corroborate the significance of AHN in aging and reveal a possible therapeutic intervention by targeting PTN.

MHC class I H2-Kb negatively regulates neural progenitor cell proliferation by inhibiting FGFR signaling.

Proteins of the major histocompatibility complex class I (MHC I), predominantly known for antigen presentation in the immune system, have recently been shown to be necessary for developmental neural refinement and adult synaptic plasticity. However, their roles in nonneuronal cell populations in the brain remain largely unexplored. Here, we identify classical MHC I molecule H2-Kb as a negative regulator of proliferation in neural stem and progenitor cells (NSPCs). Using genetic knockout mouse models and in vivo viral-mediated RNA interference (RNAi) and overexpression, we delineate a role for H2-Kb in negatively regulating NSPC proliferation and adult hippocampal neurogenesis. Transcriptomic analysis of H2-Kb knockout NSPCs, in combination with in vitro RNAi, overexpression, and pharmacological approaches, further revealed that H2-Kb inhibits cell proliferation by dampening signaling pathways downstream of fibroblast growth factor receptor 1 (Fgfr1). These findings identify H2-Kb as a critical regulator of cell proliferation through the modulation of growth factor signaling.

Poly (L-lactic acid) nanofibrous scaffolds support the proliferation and neural differentiation of mouse neural stem and progenitor cells.

The distribution and growth of cells on nanofibrous scaffolds seem to be an indispensable precondition in cell tissue engineering. The potential use of biomaterial scaffolds in neural stem cell therapy is increasingly attracting attention. In this study, we produced porous nanofibrous scaffolds fabricated from random poly-L-lactic acid (PLLA) to support neurogenic differentiation of neural stem and progenitor cells (NSPCs), isolated from the subventricular zone (SVZ) of the adult mouse brain. The viability and proliferation of the NSPCs on the nanofibrous PLLA scaffold were also tested by nuclear staining with 4, 6-diamidino-2-phenylindole dihydrochloride (DAPI), 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and scanning electron microscopy (SEM). To investigate the differentiation potential of NSPCs on the scaffolds, the cells were treated with a neurogenic differentiation medium, and immunostaining was done to detect neuronal and glial cells after 14 and 21days of cultivation. Furthermore, the morphology of differentiated cells on the scaffold was examined using SEM. The DAPI staining revealed the proliferation of NSPCs onto the surface of the nanofibrous PLLA scaffold. DAPI-positive cells were counted on days 2 and 5 after cultivation. The mean number of cells in each microscopic field was significantly (p<.05) increased (51±19 on day 2 compared to 77±25 cells on day 5). The results showed that the cell viability on PLLA scaffolds significantly increased compared to control groups. Moreover, cell viability was significantly increased 5days after culturing (262.3±50.2) as compared to 2days culture in Vitro (174.2±28.3, p<.05). Scanning electron micrographs also showed that the NSPCs adhered and differentiated on PLLA scaffolds. We found that the neural cell markers, microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP), were expressed in NSPCs seeded on random PLLA scaffolds after 21days of cultivation. These results suggest that the PLLA nano-scaffolds, due to their biocompatible property, are an appropriate structure for the proliferation, differentiation, and normal growth of NSPCs.

From stem and progenitor cells to neurons in the developing neocortex: key differences among hominids.

Comparing the biology of humans to that of other primates, and notably other hominids, is a useful path to learn more about what makes us human. Some of the most interesting differences among hominids are closely related to brain development and function, for example behaviour and cognition. This makes it particularly interesting to compare the hominid neural cells of the neocortex, a part of the brain that plays central roles in those processes. However, well-preserved tissue from great apes is usually extremely difficult to obtain. A variety of new alternative tools, for example brain organoids, are now beginning to make it possible to search for such differences and analyse their potential biological and biomedical meaning. Here, we present an overview of recent findings from comparisons of the neural stem and progenitor cells (NSPCs) and neurons of hominids. In addition to differences in proliferation and differentiation of NSPCs, and maturation of neurons, we highlight that the regulation of the timing of these processes is emerging as a general foundational difference in the development of the neocortex of hominids.

The corepressor CtBP2 is required for proper development of the mouse cerebral cortex

The development of the cerebral cortex depends on numerous parameters, including extracellular cues and microenvironmental factors that also affect gene expression. C-Terminal Binding Proteins (CtBPs) 1 and 2 are transcriptional co-repressors which have been shown to be critically involved in embryonic development. CtBPs are oxygen sensing molecules, and we have previously demonstrated an important role for CtBP1 in integrating oxygen levels and BMP-signaling to influence neural progenitor fate choice. In turn, CtBP2 has been associated with neurodevelopment and neurological disease, and we have shown that CtBP2 acetylation and dimerization, required for proper transcriptional activity, are regulated by microenvironmental oxygen levels. Yet, the putative function of CtBP2 in mammalian cortical development and neurogenesis in vivo is still largely unknown. Here we show that CtBP2 was widely expressed by neural stem and progenitor cells (NSPCs) as well as neurons during cortical development in mice. By using in utero electroporation of siRNA to reduce the levels of CtBP2 mRNA and protein in the developing mouse brain, we found that the NSPC proliferation and migration were largely perturbed, while glial differentiation under these conditions remained unchanged. Our study provides evidence that CtBP2 is required for the maintenance and migration of the NSPCs during mouse cortical development.

Possible role of EphA4 and VEGFR2 interactions in neural stem and progenitor cell differentiation.

Neural stem and progenitor cells (NSPCs) are important pluripotent stem cells, which have potential applications for cell replacement therapy. Ephrin receptors (Ephs) and angiogenic growth factor receptors have a major impact on the proliferation and differentiation of NSPCs. Potential interactions between EphA4 and vascular endothelial growth factor (VEGF) receptor (VEGFR) 2, and their roles in NSPC differentiation in vitro remain unknown. In the present study, mouse embryonic NSPCs were treated with ephrin-A1 or VEGF165 alone as well as with combination treatment (ephrin-A1 + VEGF165). Immunoprecipitation and immunoblot assays demonstrated that wild-type EphA4, but not the EphA4 kinase-dead mutant, interacted with VEGFR2 when overexpressed in 293T cells. This interaction was inhibited by dominant-negative EphA4. The percentage of β-tubulin III (Tuj1)+, but not glial fibrillary acid protein (GFAP)+ cells, was increased in the ephrin-A1 + VEGF165 combination group as compared to the VEGF165 alone group in mouse embryonic NSPCs. VEGF165-induced neuronal differentiation was potentiated by ephrin-A1 in NSPCs in vitro and ephrin-A1- or VEGF165-stimulated EphA4 and VEGFR2 interactions may mediate the signaling pathway.

A chromatin modulator sustains self-renewal and enables differentiation of postnatal neural stem and progenitor cells.

It remains unknown whether H3K4 methylation, an epigenetic modification associated with gene activation, regulates fate determination of the postnatal neural stem and progenitor cells (NSPCs). By inactivating the Dpy30 subunit of the major H3K4 methyltransferase complexes in specific regions of mouse brain, we demonstrate a crucial role of efficient H3K4 methylation in maintaining both the self-renewal and differentiation capacity of postnatal NSPCs. Dpy30 deficiency disrupts development of hippocampus and especially the dentate gyrus and subventricular zone, the major regions for postnatal NSC activities. Dpy30 is indispensable for sustaining the self-renewal and proliferation of NSPCs in a cell-intrinsic manner and also enables the differentiation of mouse and human neural progenitor cells to neuronal and glial lineages. Dpy30 directly regulates H3K4 methylation and the induction of several genes critical in neurogenesis. These findings link a prominent epigenetic mechanism of gene expression to the fundamental properties of NSPCs and may have implications in neurodevelopmental disorders.

Notch1 promotes mouse spinal neural stem and progenitor cells proliferation via p-p38-pax6 induced cyclin D1 activation

Neural stem and progenitor cells (NSPCs) are important for nerve regeneration after spinal cord injury (SCI). Their proliferation, however, is limited. In this study, we investigated the role of Notch1 signaling in NSPC proliferation using adult mouse spinal cord derived NSPCs. We observed that Notch1 promoted proliferation of NSPCs and that Notch1 overexpression led to an expansion of cells in the S-phase and increased cyclin D1 expression. When investigating the functional relationship between Notch1, p-p38 and Pax6, we found that Notch1 suppressed p-p38 while promoting Pax6 expression. Functional inhibition of p38 with SB202190 led to increased Pax6 expression and to proliferation, as determined by BrdU. Furthermore, we confirmed that Pax6 induced proliferation in adult mouse spinal cord derived NSPCs. In conclusion, we demonstrate that Notch1 promotes the proliferation of mouse spinal NSPCs via a p-p38-pax6-cyclin D1 signaling pathway. This pathway constitutes a promising new therapeutic target for SCI treatment.

Neural progenitor cells and their role in the development and evolutionary expansion of the neocortex.

The evolutionary expansion of the mammalian brain, notably the neocortex, provides a platform for the higher cognitive abilities that characterize humans. Cortical expansion is accompanied by increased folding of the pial surface, which gives rise to a gyrencephalic (folded) rather than lissencephalic (unfolded) neocortex. This expansion reflects the prolonged and increased proliferation of neural stem and progenitor cells (NPCs). Distinct classes of NPCs can be distinguished based on either cell biological criteria (apical progenitors [APs], basal progenitors [BPs]) or lineage (primary progenitors and secondary progenitors). Cortical expansion in development and evolution is linked to an increased abundance and proliferative capacity of BPs, notably basal radial glial cells, a recently characterized type of secondary progenitor derived from apical radial glial cells, the primary progenitors. To gain insight into the molecular basis underlying the prolonged and increased proliferation of NPCs and in particular BPs, comparative genomic and transcriptomic approaches, mostly for human versus mouse, have been employed and applied to specific NPC types and subpopulations. These have revealed two principal sets of molecular changes. One concerns differences in the expression of common genes between species with different degrees of cortical expansion. The other comprises human-specific genes or genomic regulatory sequences. Various systems that allow functional testing of these genomic and gene expression differences between species have emerged, including transient and stable transgenesis, genome editing, cerebral organoids, and organotypic slice cultures. These provide future avenues for uncovering the molecular basis of cortical expansion. WIREs Dev Biol 2017, 6:e256. doi: 10.1002/wdev.256 For further resources related to this article, please visit the WIREs website.

Evolution of the mammalian dentate gyrus.

The dentate gyrus (DG), a part of the hippocampal formation, has important functions in learning, memory, and adult neurogenesis. Compared with homologous areas in sauropsids (birds and reptiles), the mammalian DG is larger and exhibits qualitatively different phenotypes: 1) folded (C- or V-shaped) granule neuron layer, concave toward the hilus and delimited by a hippocampal fissure; 2) nonperiventricular adult neurogenesis; and 3) prolonged ontogeny, involving extensive abventricular (basal) migration and proliferation of neural stem and progenitor cells (NSPCs). Although gaps remain, available data indicate that these DG traits are present in all orders of mammals, including monotremes and marsupials. The exception is Cetacea (whales, dolphins, and porpoises), in which DG size, convolution, and adult neurogenesis have undergone evolutionary regression. Parsimony suggests that increased growth and convolution of the DG arose in stem mammals concurrently with nonperiventricular adult hippocampal neurogenesis and basal migration of NSPCs during development. These traits could all result from an evolutionary change that enhanced radial migration of NSPCs out of the periventricular zones, possibly by epithelial-mesenchymal transition, to colonize and maintain nonperiventricular proliferative niches. In turn, increased NSPC migration and clonal expansion might be a consequence of growth in the cortical hem (medial patterning center), which produces morphogens such as Wnt3a, generates Cajal-Retzius neurons, and is regulated by Lhx2. Finally, correlations between DG convolution and neocortical gyrification (or capacity for gyrification) suggest that enhanced abventricular migration and proliferation of NSPCs played a transformative role in growth and folding of neocortex as well as archicortex.

Metabolic control of adult neural stem cell activity by Fasn-dependent lipogenesis

Mechanisms controlling the proliferative activity of neural stem and progenitor cells (NSPCs) have a pivotal role to ensure life-long neurogenesis in the mammalian brain. How metabolic programs are coupled with NSPC activity remains unknown. Here we show that fatty acid synthase (Fasn), the key enzyme of de novo lipogenesis, is highly active in adult NSPCs and that conditional deletion of Fasn in mouse NSPCs impairs adult neurogenesis. The rate of de novo lipid synthesis and subsequent proliferation of NSPCs is regulated by Spot14, a gene previously implicated in lipid metabolism, that we found to be selectively expressed in low proliferating adult NSPCs. Spot14 reduces the availability of malonyl-CoA, which is an essential substrate for Fasn to fuel lipogenesis. Thus, we identify here a functional coupling between the regulation of lipid metabolism and adult NSPC proliferation.

Evidence for and against regional differences in neural stem and progenitor cells of the CNS: Figure 1.

Neural stem and progenitor cells (NSCs) give rise to the cellular diversity of the CNS. There is evidence both for and against differences in these cells based on the region of the brain in which they reside. Primary brain tumors mimic many aspects of NSC behavior. Recent data suggest that some of the variability in glioma biology may be, in part, a reflection of regional differences in the NSCs from which they arise. In this issue of Genes & Development, Lee and colleagues (pp. 2317-2329) examine how NF1 regulates NSC proliferation and glial differentiation in the brainstem and cortex of the postnatal mouse brain.

Pannexin 2 Is Expressed by Postnatal Hippocampal Neural Progenitors and Modulates Neuronal Commitment

The pannexins (Panx1, -2, and -3) are a mammalian family of putative single membrane channels discovered through homology to invertebrate gap junction-forming proteins, the innexins. Because connexin gap junction proteins are known regulators of neural stem and progenitor cell proliferation, migration, and specification, we asked whether pannexins, specifically Panx2, play a similar role in the postnatal hippocampus. We show that Panx2 protein is differentially expressed by multipotential progenitor cells and mature neurons. Both in vivo and in vitro, Type I and IIa stem-like neural progenitor cells express an S-palmitoylated Panx2 species localizing to Golgi and endoplasmic reticulum membranes. Protein expression is down-regulated during neurogenesis in neuronally committed Type IIb and III progenitor cells and immature neurons. Panx2 is re-expressed by neurons following maturation. Protein expressed by mature neurons is not palmitoylated and localizes to the plasma membrane. To assess the impact of Panx2 on neuronal differentiation, we used short hairpin RNA to suppress Panx2 expression in Neuro2a cells. Knockdown significantly accelerated the rate of neuronal differentiation. Neuritic extension and the expression of antigenic markers of mature neurons occurred earlier in stable lines expressing Panx2 short hairpin RNA than in controls. Together, these findings describe an endogenous post-translational regulation of Panx2, specific to early neural progenitor cells, and demonstrate that this expression plays a role in modulating the timing of their commitment to a neuronal lineage.

Smad7 Regulates the Adult Neural Stem/Progenitor Cell Pool in a Transforming Growth Factor β- and Bone Morphogenetic Protein-Independent Manner

Members of the transforming growth factor beta (TGF-beta) family of proteins modulate the proliferation, differentiation, and survival of many different cell types. Neural stem and progenitor cells (NPCs) in the adult brain are inhibited in their proliferation by TGF-beta and by bone morphogenetic proteins (BMPs). Here, we investigated neurogenesis in a hypomorphic mouse model for the TGF-beta and BMP inhibitor Smad7, with the hypothesis that NPC proliferation might be reduced due to increased TGF-beta and BMP signaling. Unexpectedly, we found enhanced NPC proliferation as well as an increased number of label-retaining cells in vivo. The enhanced proliferation potential of mutant cells was retained in vitro in neurosphere cultures. We observed a higher sphere-forming capacity as well as faster growth and cell cycle progression. Use of specific inhibitors revealed that these effects were independent of TGF-beta and BMP signaling. The enhanced proliferation might be at least partially mediated by elevated signaling via epidermal growth factor (EGF) receptor, as mutant cells showed higher expression and activation levels of the EGF receptor. Conversely, an EGF receptor inhibitor reduced the proliferation of these cells. Our data indicate that endogenous Smad7 regulates neural stem/progenitor cell proliferation in a TGF-beta- and BMP-independent manner.