Regulation of neural stem cell in the human SVZ by trophic and morphogenic factors

The Subventricular Zone in Glioblastoma: Genesis, Maintenance, and Modeling

Glioblastoma (GBM) is a malignant tumor with a median survival rate of 15-16 months with standard care; however, cases of successful treatment offer hope that an enhanced understanding of the pathology will improve the prognosis. The cell of origin in GBM remains controversial. Recent evidence has implicated stem cells as cells of origin in many cancers. Neural stem/precursor cells (NSCs) are being evaluated as potential initiators of GBM tumorigenesis. The NSCs in the subventricular zone (SVZ) have demonstrated similar molecular profiles and share several distinctive characteristics to proliferative glioblastoma stem cells (GSCs) in GBM. Genomic and proteomic studies comparing the SVZ and GBM support the hypothesis that the tumor cells and SVZ cells are related. Animal models corroborate this connection, demonstrating migratory patterns from the SVZ to the tumor. Along with laboratory and animal research, clinical studies have demonstrated improved progression-free survival in patients with GBM after radiation to the ipsilateral SVZ. Additionally, key genetic mutations in GBM for the most part carry regulatory roles in the SVZ as well. An exciting avenue towards SVZ modeling and determining its role in gliomagenesis in the human context is human brain organoids. Here we comprehensively discuss and review the role of the SVZ in GBM genesis, maintenance, and modeling.

Injection of Stromal Cell-Derived Factor-1 (SDF-1) Nanoparticles After Traumatic Brain Injury Stimulates Recruitment of Neural Stem Cells

Traumatic brain injury (TBI) usually results from direct mechanical damage to the brain, which leads to degeneration and death of the central nervous system (CNS). The migration of neural stem/progenitor cells (NSCs) to brain is essential to various physiological and pathological processes of the CNS. Therefore, NSCs are considered as a promising alternative option for neurological diseases. SDF-1α is one of known chemokines whose receptor CXCR4 is detected in the CNS. We explored the efficacy of nanoparticles loaded with SDF-1 on TBI and analyzed its potential mechanism. After synthesis of SDF-1-loaded microspheres (MS) and -nanoparticles and establishment of animal model of TBI, 50 modeled mice were randomly injected with MS bovine serum albumin (BSA), MS SDF1, or SDF1-loaded nanoparticles and 10 TBI animals were taken as control group. After that, we observed the lesions and examined the characteristics of the nanoparticles and MS. Transwell assay and immunofluorescence were conducted to determine the migration and invasion upon treatments. Nanoparticles and MS encapsulated most of SDF-1, but MS released 100% SDF-1 and the nanoparticles alone released minority (25%) within 2 weeks. As only SDF-1 nanoparticles could induce NSCs to migrate to the injured area, this approach could enhance healing of the lesion with more NSCs around the lesion. Collectively, this study used particles to deliver SDF-1 to the central nervous system with nanoparticles having a longer-lasting release. Injection of nanoparticleloaded SDF-1 would retain the biological activity of SDF-1 and improve neuroblast migration, thereby improving the TBI condition. These findings show great prospect for nanoparticles application in brain injury.

Therapeutic Plasticity of Neural Stem Cells

Neural stem cells (NSCs) have garnered significant scientific and commercial interest in the last 15 years. Given their plasticity, defined as the ability to develop into different phenotypes inside and outside of the nervous system, with a capacity of almost unlimited self-renewal, of releasing trophic and immunomodulatory factors, and of exploiting temporal and spatial dynamics, NSCs have been proposed for (i) neurotoxicity testing; (ii) cellular therapies to treat CNS diseases; (iii) neural tissue engineering and repair; (iv) drug target validation and testing; (v) personalized medicine. Moreover, given the growing interest in developing cell-based therapies to target neurodegenerative diseases, recent progress in developing NSCs from human-induced pluripotent stem cells has produced an analog of endogenous NSCs. Herein, we will review the current understanding on emerging conceptual and technological topics in the neural stem cell field, such as deep characterization of the human compartment, single-cell spatial-temporal dynamics, reprogramming from somatic cells, and NSC manipulation and monitoring. Together, these aspects contribute to further disentangling NSC plasticity to better exploit the potential of those cells, which, in the future, might offer new strategies for brain therapies.

Neural Stem Cells of the Subventricular Zone as the Origin of Human Glioblastoma Stem Cells. Therapeutic Implications

Human glioblastoma is the most aggressive type of primary malignant brain tumors. Standard treatment includes surgical resection followed by radiation and chemotherapy but it only provides short-term benefits and the prognosis of these brain tumors is still very poor. Glioblastomas contain a population of glioma stem cells (GSCs), with self-renewal ability, which are partly responsible for the tumor resistance to therapy and for the tumor recurrence after treatment. The human adult subventricular zone contains astrocyte-like neural stem cells (NSCs) that are probably reminiscent of the radial glia present in embryonic brain development. There are numerous molecules involved in the biology of subventricular zone NSCs that are also instrumental in glioblastoma development. These include cytoskeletal proteins, telomerase, tumor suppressor proteins, transcription factors, and growth factors. Interestingly, genes encoding these molecules are frequently mutated in glioblastoma cells. Indeed, it has been recently shown that NSCs in the subventricular zone are a potential cell of origin that contains the driver mutations of human glioblastoma. In this review we will describe common features between GSCs and subventricular zone NSCs, and we will discuss the relevance of this important finding in terms of possible future therapeutic strategies.

The neurofilament derived-peptide NFL-TBS.40-63 enters in-vitro in human neural stem cells and increases their differentiation

Regenerative medicine is a promising approach to treat neurodegenerative diseases by replacing degenerating cells like neurons or oligodendrocytes. Targeting human neural stem cells directly in the brain is a big challenge in such a strategy. The neurofilament derived NFL-TBS.40-63 peptide has recently been introduced as a novel tool to target neural stem cells. Previous studies showed that this peptide can be internalized by rat neural stem cells in vitro and in vivo, which coincided with lower proliferation and self-renewal capacity and increase of differentiation. In this study, we analyzed the uptake and potential effects of the NFL-TBS.40-63 peptide on human neural stem cells isolated from human fetuses. We showed that the peptide inhibits proliferation and the ability to produce neurospheres in vitro, which is consistent with an increase in cell adhesion and differentiation. These results confirm that the peptide could be a promising molecule to target and manipulate human neural stem cells and thus could serve as a strategic tool for regenerative medicine.

Differentiation of circulating neural progenitor cells in vitro on fibrin-based composite -matrix involves Wnt- β-catenin-like signaling

Isolation of progenitors with regenerative potential and their in vitro induction to specific lineage may be necessary for effective cell transplantation outcome. Earlier, we standardized specific niche for derivation of neural progenitor cells (NPCs) from circulating mononuclear cells to neural like cells (NLC) in vitro, for applications in neural regeneration. The current study analysed the prospective involvement of signaling mechanism for in vitro lineage commitment of circulating NPCs. Preferred mechanism selected was Wnt-like signaling because this is one of the pathways implicated in the central nervous system (CNS) development and homeostasis. We sought to determine the activation of Wnt3a-specific genes in the standardized NPC culture system. To start with, it was found that when standardized NPC culture niche was supplemented with Wnt 3a protein, no additional morphological changes happen. Chemical inhibitors of the pathway retarded NPC to NLC conversion both in the absence and presence of supplemented Wnt-3a. In earlier studies, involvement of the niche constituents- fibronectin (FN), laminin (La) and fibrin (Fib)- for NPC growth and differentiation was established. In an attempt to study the role of these adhesive proteins by adding antibodies against FN, La & Fib together, molecular level signaling changes seen were comparable to that occur in response to Wnt3a chemical inhibitor. Therefore, induction of Wnt 3a-like signal from the matrix-dependent niche constituents may be implicated in the differentiation of NPC to NLC. The results substantiate the potential applications of the fibrin-based composite niche in neural engineering for regeneration.

Stochastic nanoroughness modulates neuron-astrocyte interactions and function via mechanosensing cation channels

Extracellular soluble signals are known to play a critical role in maintaining neuronal function and homeostasis in the CNS. However, the CNS is also composed of extracellular matrix macromolecules and glia support cells, and the contribution of the physical attributes of these components in maintenance and regulation of neuronal function is not well understood. Because these components possess well-defined topography, we theorize a role for topography in neuronal development and we demonstrate that survival and function of hippocampal neurons and differentiation of telencephalic neural stem cells is modulated by nanoroughness. At roughnesses corresponding to that of healthy astrocytes, hippocampal neurons dissociated and survived independent from astrocytes and showed superior functional traits (increased polarity and calcium flux). Furthermore, telencephalic neural stem cells differentiated into neurons even under exogenous signals that favor astrocytic differentiation. The decoupling of neurons from astrocytes seemed to be triggered by changes to astrocyte apical-surface topography in response to nanoroughness. Blocking signaling through mechanosensing cation channels using GsMTx4 negated the ability of neurons to sense the nanoroughness and promoted decoupling of neurons from astrocytes, thus providing direct evidence for the role of nanotopography in neuron-astrocyte interactions. We extrapolate the role of topography to neurodegenerative conditions and show that regions of amyloid plaque buildup in brain tissue of Alzheimer's patients are accompanied by detrimental changes in tissue roughness. These findings suggest a role for astrocyte and ECM-induced topographical changes in neuronal pathologies and provide new insights for developing therapeutic targets and engineering of neural biomaterials.

Diphenylhydantoin promotes proliferation in the subventricular zone and dentate gyrus

PROBLEM STATEMENT

Diphenylhydantoin (phenytoin) is an antiepileptic drug that generates hyperplasia in some tissue by stimulating Epidermal Growth Factor (EGFR) and Platelet-Derived Growth Factor beta (PDGFR-β) receptors and by increasing serum levels of basic fibroblast growth factor (bFGF, FGF2 or FGF-β). Neural stem cells in the adult brain have been isolated from three regions: the Subventricular Zone (SVZ) lining the lateral wall of the lateral ventricles, the Subgranular Zone (SGZ) in the dentate gyrus at the hippocampus and the Subgranular Zone (SZC) lining between the hippocampus and the corpus callosum. Neural stem cells actively respond to bFGF, PDGFR-β or EGF by increasing their proliferation, survival and differentiation. The aim of this study was to evaluate the effect of phenytoin on proliferation and apoptosis in the three neurogenic niches in the adult brain.

APPROACH

We orally administrated phenytoin with an oropharyngeal cannula for 30 days: 0 mg kg^-1 (controls), 1, 5, 10, 50 and 100 mg kg^-1. To label proliferative cells, three injections of 100 mg kg^-1 of BrdU was administrated every 12 h. Immunohistochemistry against BrdU or Caspase-3 active were performed to determine the number of proliferative or apoptotic cells.

RESULTS

Our results showed that phenytoin induces proliferation in the SVZ and the SGZ in a dose-dependent manner. No statistically significant effects on cell proliferation in the SCZ neither in the apoptosis rate at the SVZ, SGZ and SCZ were found.

CONCLUSION

These data indicate that phenytoin promotes a dose-dependent proliferation in the SVZ and SGZ of the adult brain. The clinical relevance of these findings remain to be elucidated.

Role of fibroblast growth factor receptors in astrocytic stem cells

There are two well-defined neurogenic regions in the adult brain, the subventricular zone (SVZ) lining the lateral wall of the lateral ventricles and, the subgranular zone (SGZ) in the dentate gyrus at the hippocampus. Within these neurogenic regions, there are neural stem cells with astrocytic characteristics, which actively respond to the basic fibroblast growth factor (bFGF, FGF2 or FGF-β) by increasing their proliferation, survival and differentiation, both in vivo and in vitro. FGF2 binds to fibroblast growth factor receptors 1 to 4 (FGFR1, FGFR2, FGFR3, FGFR4). Interestingly, these receptors are differentially expressed in neurogenic progenitors. During development, FGFR-1 and FGFR-2 drive oligodendrocytes and motor neuron specification. In particular, FGFR-1 determines oligodendroglial and neuronal cell fate, whereas FGFR-2 is related to oligodendrocyte specification. In the adult SVZ, FGF-2 promotes oligodendrogliogenesis and myelination. FGF-2 deficient mice show a reduction in the number of new neurons in the SGZ, which suggests that FGFR-1 is important for neuronal cell fate in the adult hippocampus. In human brain, FGF-2 appears to be an important component in the anti-depressive effect of drugs. In summary, FGF2 is an important modulator of the cell fate of neural precursor and, promotes oligodendrogenesis. In this review, we describe the expression pattern of FGFR2 and its role in neural precursors derived from the SVZ and the SGZ.