Stem Cells In Adult Brain Research Articles

MR Imaging, MGMT Promoter Methylation Features and Prognostic Analysis of Subventricular Zone Contacting IDH Wild-type Glioblastoma.

As the largest concentration of neural stem cells in adult brain, the subventricular zone (SVZ) is considered to be a potential source of glioblastoma (GBM) occurrence in recent years. In this study, 116 patients with glioblastoma treated at PLA General Hospital were retrospectively reviewed. The features of SVZ contacting glioblastoma were analyzed in terms of MR imaging and MGMT promoter methylation. We also evaluated the prognostic value of SVZ contacting in GBM patients. GBM with SVZ involvement on MRI is more likely to grow across the midline (36.8% vs. 6.9%, P=0.002), more often multifocal lesion (35.6% vs. 6.9%, P=0.003) and have a lower proportion of MGMT promoter methylation (36.8% vs. 69.0%, P=0.003). The median overall survival and progression- free survival of patients in the SVZ contacting group were 12 months and 7 months, while 25 months and 17 months in the non-contacting group (P<0.001, respectively). There was no significant difference in overall survival (P=0.229) and progression-free survival (P=0.808) between patients with different SVZ contacting regions. Multivariate survival analysis indicated that patients with MRI SVZ involvement showed worse overall survival (HR=2.060, 95%CI 1.195-3.550，P=0.009) and progression- free survival (HR=3.021, 95%CI 1.788-5.104，P＜0.001). This study suggested that MRI SVZ involvement at diagnosis is an independent risk factor for overall survival and progression-free survival in IDH wild-type glioblastoma patients. Based on MR imaging, we also found that SVZ contacting glioblastomas had a larger proportion of crossing midline tumors and multifocal lesions. In addition, patients with SVZ contact in our research presented a lower proportion of MGMT promoter methylation.

Immune-stem cell crosstalk in the central nervous system: how oligodendrocyte progenitor cells interact with immune cells.

The interaction between immune and stem cells has proven essential for homeostasis and regeneration in a wide range of tissues. However, because the central nervous system was long considered an immune-privileged organ, its immune-stem cell axis was not deeply investigated until recently. Research has shown that oligodendrocyte progenitor cells (OPCs), a highly abundant population of adult brain stem cells, establish bidirectional interactions with the immune system. Here, we provide an overview of the interactions that OPCs have with tissue-resident and recruited immune cells, paying particular attention to the role they play in myelin regeneration and neuroinflammation. We highlight the described role of OPCs as key active players in neuroinflammation, overriding the previous concept that OPCs are mere recipients of immune signals. Understanding the mechanisms behind this bidirectional interaction holds great potential for the development of novel therapeutic approaches limiting neuroinflammation and promoting myelin repair. A better understanding of the central nervous system's immune-stem cell axis will also be key for tackling two important features shared across neurodegenerative diseases, neuroinflammation and myelin loss.

Lineage Tracing of Inducible Fluorescently-Labeled Stem Cells in the Adult Mouse Brain.

A telomerase reverse transcriptase (Tert) lineage-tracing mouse line was developed to investigate the behavior and fate of adult tissue stem cells, by crossing the 'Tet-On' system oTet-Cre mouse with a novel reverse tetracycline transactivator (rtTA) transgene linked to the Tert promoter, which we have demonstrated marks a novel population of adult brain stem cells. Here, administration of the tetracycline derivative doxycycline to mTert-rtTA::oTet-Cre mice will indelibly mark a population of cells that express a 4.4 kb fragment of the promoter region of the gene Tert. When combined the Rosa-mTmG reporter, mTert-rtTA::oTet-Cre::Rosa-mTmG mice will express membrane tdTomato (mTomato) until doxycycline treatment induces the replacement of mTomato expression with membrane EGFP (mGFP) in cells that also express Tert. Therefore, when these triple-transgenic lineage tracing mice receive doxycycline (the "pulse" period during which TERT expressing cells are marked), these cells will become indelibly marked mGFP+ cells, which can be tracked for any desirable amount of time after doxycycline removal (the "chase" period), even if Tert expression is subsequently lost. Brains are then perfusion-fixed and processed for immunofluorescence and other downstream applications in order to interpret changes to stem cell activation, proliferation, lineage commitment, migration to various brain niches, and differentiation to mature cell types. Using this system, any rtTA mouse can be mated to oTet-Cre and a Rosa reporter to conduct doxycycline-inducible "pulse-chase" lineagetracing experiments using markers of stem cells.

Monocyte depletion early after stroke promotes neurogenesis from endogenous neural stem cells in adult brain

Ischemic stroke, caused by middle cerebral artery occlusion, leads to long-lasting formation of new striatal neurons from neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ) of adult rodents. Concomitantly with this neurogenic response, SVZ exhibits activation of resident microglia and infiltrating monocytes. Here we show that depletion of circulating monocytes, using the anti-CCR2 antibody MC-21 during the first week after stroke, enhances striatal neurogenesis at one week post-insult, most likely by increasing short-term survival of the newly formed neuroblasts in the SVZ and adjacent striatum. Blocking monocyte recruitment did not alter the volume of the ischemic lesion but gave rise to reduced astrocyte activation in SVZ and adjacent striatum, which could contribute to the improved neuroblast survival. A similar decrease of astrocyte activation was found in and around human induced pluripotent stem cell (iPSC)-derived NSPCs transplanted into striatum at one week after stroke in monocyte-depleted mice. However, there was no effect on neurogenesis in the graft as determined 8weeks after implantation. Our findings demonstrate, for the first time, that a specific cellular component of the early inflammatory reaction in SVZ and adjacent striatum following stroke, i.e., infiltrating monocytes, compromises the short-term neurogenic response neurogenesis from endogenous NSPCs.

Electrical Guidance of Human Stem Cells in the Rat Brain.

SummaryLimited migration of neural stem cells in adult brain is a roadblock for the use of stem cell therapies to treat brain diseases and injuries. Here, we report a strategy that mobilizes and guides migration of stem cells in the brain in vivo. We developed a safe stimulation paradigm to deliver directional currents in the brain. Tracking cells expressing GFP demonstrated electrical mobilization and guidance of migration of human neural stem cells, even against co-existing intrinsic cues in the rostral migration stream. Transplanted cells were observed at 3 weeks and 4 months after stimulation in areas guided by the stimulation currents, and with indications of differentiation. Electrical stimulation thus may provide a potential approach to facilitate brain stem cell therapies.

Characterization of TLX Expression in Neural Stem Cells and Progenitor Cells in Adult Brains

TLX has been shown to play an important role in regulating the self-renewal and proliferation of neural stem cells in adult brains. However, the cellular distribution of endogenous TLX protein in adult brains remains to be elucidated. In this study, we used immunostaining with a TLX-specific antibody to show that TLX is expressed in both neural stem cells and transit-amplifying neural progenitor cells in the subventricular zone (SVZ) of adult mouse brains. Then, using a double thymidine analog labeling approach, we showed that almost all of the self-renewing neural stem cells expressed TLX. Interestingly, most of the TLX-positive cells in the SVZ represented the thymidine analog-negative, relatively quiescent neural stem cell population. Using cell type markers and short-term BrdU labeling, we demonstrated that TLX was also expressed in the Mash1+ rapidly dividing type C cells. Furthermore, loss of TLX expression dramatically reduced BrdU label-retaining neural stem cells and the actively dividing neural progenitor cells in the SVZ, but substantially increased GFAP staining and extended GFAP processes. These results suggest that TLX is essential to maintain the self-renewing neural stem cells in the SVZ and that the GFAP+ cells in the SVZ lose neural stem cell property upon loss of TLX expression.Understanding the cellular distribution of TLX and its function in specific cell types may provide insights into the development of therapeutic tools for neurodegenerative diseases by targeting TLX in neural stem/progenitors cells.

VEGF evokes reactive astroglia to convert into neuronal cells by affecting the biological function of MeCP2 in adult rat brain after cerebral ischemia

Although astroglia-like cells, which act as stem cells in adult brain, reside in a few restricted stem cell niches, they can acquire or reactivate stem cell potential as part of reactive gliosis and be elicited to generate neurons following brain injury. However, it is still unclear how reactive astroglia retain their specific attributes and convert into neurons by repressing cellular properties characteristic of other lineages. In this study, we not only demonstrated that VEGF promoted reactive astroglia to differentiate into Doublecortin (DCX)-expressing neuronal cells in adult rat striatum after cerebral ischemia, but also uncovered the molecular pathways possibly involved in this process. We showed that MeCP2 became newly phosphorylated at a specific amino acid residue, Serine 292 (S292) following cerebral ischemia, which was able to alter its spatial distribution and affect its bio-functions. MeCP2 S292 phosphorylation mediated its translocation from nucleus to cytoplasm and deprived of its ability to bind to the lineage specific gene promoters (such as Gfap, Nestin and Dcx), leading to a relief of transcriptional repression and allowing for gene activation. Morphological results showed that reactive astroglia with weak immunoreactivity of MeCP2 will have high probability to become DCX-expressing cells. Furthermore, VEGF act as an instructive signal and induced reactive astroglia toward a neuronal fate possibly by strengthening MeCP2 phosphorylation and activating lineage specific gene expression. Our findings added an important new facet to the growing list of pleiotropic effects of VEGF in mammalian brain and suggested that MeCP2 is highly relevant to the differentiation plasticity of reactive astroglia in the ischemic rat striatum.

Survival and Neuronal Differentiation of Mesenchymal Stem Cells Transplanted into the Rodent Brain Are Dependent upon Microenvironment

The successful integration of stem cells in adult brain has become a central issue in modern neuroscience. In this study we sought to test the hypothesis that survival and neurodifferentiation of mesenchymal stem cells (MSCs) may be dependent upon microenvironmental conditions according to the site of implant in the brain. MSCs were isolated from adult rats and labeled with enhanced-green fluorescent protein (eGFP) lentivirus. A cell suspension was implanted stereotactically into the brain of 50 young rats, into one neurogenic area (hippocampus), and into another nonneurogenic area (striatum). Animals were sacrificed 6 or 12 weeks after surgery, and brains were stained for mature neuronal markers. Cells coexpressing NeuN (neuronal specific nuclear protein) and GFP (green fluorescent protein) were counted stereologically at both targets. The isolated cell population was able to generate neurons positive for microtubule-associated protein 2 (MAP2), neuronal-specific nuclear protein (NeuN), and neurofilament 200 (NF200) in vitro. Electrophysiology confirmed expression of voltage-gated ionic channels. Once implanted into the hippocampus, cells survived for up to 12 weeks, migrated away from the graft, and gave rise to mature neurons able to synthesize neurotransmitters. By contrast, massive cell degeneration was seen in the striatum, with no significant migration. Induction of neuronal differentiation with increased cyclic adenosine monophosphate in the culture medium before implantation favored differentiation in vivo. Our data demonstrated that survival and differentiation of MSCs is strongly dependent upon a permissive microenvironment. Identification of the pro-neurogenic factors present in the hippocampus could subsequently allow for the integration of stem cells into nonpermissive areas of the central nervous system.

Recent advancements in stem cell and gene therapies for neurological disorders and intractable epilepsy

The potential applications of stem cell therapies for treating neurological disorders are enormous. Many laboratories are focusing on stem cell treatments for CNS diseases, including spinal cord injury, Amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease, multiple sclerosis, stroke, traumatic brain injury, and epilepsy. Among the many stem cell types under testing for neurological treatments, the most common are fetal and adult brain stem cells, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells. An expanding toolbox of molecular probes is now available to allow analyses of neural stem cell fates prior to and after transplantation. Concomitantly, protocols are being developed to direct the fates of stem cell-derived neural progenitors, and also to screen stem cells for tumorigenicity and aneuploidy. The rapid progress in the field suggests that novel stem cell and gene therapies for neurological disorders are in the pipeline.

Molecular and Magnetic Resonance Imaging of Human Embryonic Stem Cell–Derived Neural Stem Cell Grafts in Ischemic Rat Brain

Real-time imaging of transplanted stem cells is essential for understanding their interactions in vivo with host environments, for tracking cell fate and function and for successful delivery and safety monitoring in the clinical setting. In this study, we used bioluminescence (BLI) and magnetic resonance imaging (MRI) to visualize the fate of grafted human embryonic stem cell (hESC)-derived human neural stem cells (hNSCs) in stroke-damaged rat brain. The hNSCs were genetically engineered with a lentiviral vector carrying a double fusion (DF) reporter gene that stably expressed enhanced green fluorescence protein (eGFP) and firefly luciferase (fLuc) reporter genes. The hNSCs were self-renewable, multipotent, and expressed markers for neural stem cells. Cell survival was tracked noninvasively by MRI and BLI for 2 months after transplantation and confirmed histologically. Electrophysiological recording from grafted GFP(+) cells and immuno-electronmicroscopy demonstrated connectivity. Grafted hNSCs differentiated into neurons, into oligodendrocytes in stroke regions undergoing remyelination and into astrocytes extending processes toward stroke-damaged vasculatures. Our data suggest that the combination of BLI and MRI modalities provides reliable real-time monitoring of cell fate.

Persistent Production of Neurons from Adult Brain Stem Cells During Recovery after Stroke

Neural stem cells in the subventricular zone of adult rodents produce new striatal neurons that may replace those that have died after stroke; however, the neurogenic response has been considered acute and transient, yielding only small numbers of neurons. In contrast, we show herein that striatal neuroblasts are generated without decline at least for 4 months after stroke in adult rats. Neuroblasts formed early or late after stroke either differentiate into mature neurons, which survive for several months, or die through caspase-mediated apoptosis. The directed migration of the new neurons toward the ischemic damage is regulated by stromal cell-derived factor-1alpha and its receptor CXCR4. These results show that endogenous neural stem cells continuously supply the injured adult brain with new neurons, which suggests novel self-repair strategies to improve recovery after stroke.

PEDF: bridging neurovascular interactions in the stem cell niche

Stem cells are defined by their ability to self-renew. Adult brain stem cells divide slowly, and it is unclear how their division is regulated. A new study identifies PEDF as a growth factor that promotes adult stem cell self-renewal.

Region-specific generation of functional neurons from naive embryonic stem cells in adult brain.

Embryonic stem (ES) cells are multipotent progenitors with unlimited developmental potential, and in vitro differentiated ES cell-derived neuronal progenitors can develop into functional neurons when transplanted in the central nervous system. As the capacity of naive primary ES cells to integrate in the adult brain and the role of host neural tissue therein are yet largely unknown, we grafted low densities of undifferentiated mouse ES (mES) cells in adult mouse brain regions associated with neurodegenerative disorders; and we demonstrate that ES cell-derived neurons undergo gradual integration in recipient tissue and acquire morphological and electrophysiological properties indistinguishable from those of host neurons. Only some brain areas permitted survival of mES-derived neural progenitors and formed instructive environments for neuronal differentiation and functional integration of naive mES cells. Hence, region-specific presence of microenvironmental cues and their pivotal involvement in controlling ES cell integration in adult brain stress the importance of recipient tissue characteristics in formulating cell replacement strategies for neurodegenerative disorders.

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Analysis of glycosphingolipid composition of a neural progenitor cell line

Continuous neurogenesis from neural stem cells in adult brain suggests the possibility that these newly generated neural tissue may be capable of repair of the neurodegeneration associated with genetic disorders, trauma, and aging. Glycosphingolipids (GSLs) play important roles in cellular growth, differentiation and cell signalling; however, little is known about the GSL composition in neural progenitor and/or stem cells. In order to characterize the GSL composition in neural stem cells, we studied the multipotential C17.2 cell line that was generated after myc‐transformation of isolated from neonatal mouse cerebellar neural progenitor cells. The developmental potential of C17.2 cells is similar to the endogenous neural stem cells, i.e. they are capable of self‐renewal and differentiation into neurons and glia (Snyder et al. Cell68, 33–51, 1992). HPTLC analysis of the total lipid fractions isolated undifferentiated C17.2 cells revealed that the major GSL expressed in these cells were glucosylceramide, GM3, GM2, GM1, and GD1a. Histochemical staining for GM1 using cholera toxin B subunit revealed punctate staining on the plasma membrane, suggesting GM1 at the plasma membrane, maybe clustered into microdomain‐like structures. Our results indicate that the undifferentiated C17.2 neural stem cell line is unique in expression of a‐series gangliosides. These gangliosides may prove to be useful markers for these cells.Acknowledgements: Supported by an NIH grant NS11853 and a grant from the Children's Medical Research Foundation.