Neural stem cell systems: diversities and properties after transplantation in animal models of diseases

MiceDEGdb: a knowledge base on differentially expressed mouse genes as a model object in biomedical research

The fundamental understanding of many biological processes that unfold in a human body has become possible due to experimental studies on animal models. The backbone of modern biomedical research is the use of mouse models for studying important pathophysiological mechanisms, assessing new therapeutic approaches and making decisions on acceptance or rejection of new candidate medicines in preclinical trials. The use of mice is advantageous because they have small size, are easy to keep and to genetically modify. Mice make up more than 90 % of the rodents used for pharmaceutical research. We present the pilot version of MiceDEGdb, a knowledge base on the genes that are differentially expressed in the mouse used as a model object in biomedical research. MiceDEGdb is a collection of published data on gene expression in mouse strains used for studying age-related diseases, such as hypertension, periodontal disease, bone fragility, renal fibrosis, smooth muscle remodeling, heart failure and circadian rhythm disorder. The pilot release of MiceDEGdb contains 21,754 DEGs representing 9,769 unique Mus musculus genes the transcription levels whereof were found as being changed in 25 RNA-seq experiments involving eight tissues - gum, bone, kidney, right ventricle, aortic arch, hippocampus, skeletal muscle and uterus - in six genetic mouse strains (C57BL/6J, Ren1cCre|ZsGreen, B6.129S7(Cg)-Polgtm1Prol/J, BPN/3J, BPH/2J and Kunming) used as models of eight human diseases - all these data were based on information in 10 original articles. MiceDEGdb is novel in that it features a curated annotation of changes in the expression levels of mouse DEGs using independent biomedical publications about same-direction changes in the expression levels of human homologs in patients with one disease or the other. In its pilot release, MiceDEGdb documented 85,092 such annotations for 318 human genes in 895 diseases, as suggest to 912 scientific articles referenced by their PubMed ID. The information contained in MiceDEGdb may be of interest to geneticists, molecular biologists, bioinformatics scientists, clinicians, pharmacologists and genetic advisors in personalized medicine. MiceDEGdb is freely available at https://www.sysbio.ru/MiceDEGdb.

Transplantation of Bone Marrow-Derived Stem Cells: A Promising Therapy for Stroke

Stroke remains a major cause of death in the US and around the world. Over the last decade, stem cell therapy has been introduced as an experimental treatment for stroke. Transplantation of stem cells or progenitors into the injured site to replace the nonfunctional cells, and enhancement of proliferation or differentiation of endogenous stem or progenitor cells stand as the two major cell-based strategies. Potential sources of stem/progenitor cells for stroke include fetal neural stem cells, embryonic stem cells, neuroteratocarcinoma cells, umbilical cord blood-derived nonhematopoietic stem cells, and bone marrow-derived stem cells. The goal of this article is to provide an update on the preclinical use of bone marrow-derived stem cells with major emphasis on mesenchymal stem cells (MSCs) and multipotent adult progenitor cells (MAPCs) because they are currently most widely applied in experimental stroke studies and are now being phased into early clinical trials. The phenotypic features of MSCs and MAPCs, as well as their application in stroke, are described.

Neural Stem Cell Transplantation Promotes Functional Recovery from Traumatic Brain Injury via Brain Derived Neurotrophic Factor-Mediated Neuroplasticity

Traumatic brain injury (TBI) induces cognitive impairments, motor and behavioral deficits. Previous evidences have suggested that neural stem cell (NSC) transplantation could facilitate functional recovery from brain insults, but their underlying mechanisms remains to be elucidated. Here, we established TBI model by an electromagnetic-controlled cortical impact device in the rats. Then, 5 μl NSCs (5.0 × 10⁵/μl), derived from green fluorescent protein (GFP) transgenic mouse, was transplanted into the traumatic brain regions of rats at 24 h after injury. After differentiation of the NSCs was determined using immunohistochemistry, neurological severity scores (NSS) and rotarod test were conducted to detect the neurological behavior. Western blot and RT-PCR as well as ELASA were used to evaluate the expression of synaptophysin and brain-derived neurotrophic factor (BDNF). In order to elucidate the role of BDNF on the neural recovery after NSC transplantation, BDNF knockdown in NSC was performed and transplanted into the rats with TBI, and potential mechanism for BDNF knockdown in the NSC was analyzed using microassay analysis. Meanwhile, BDNF antibody blockade was conducted to further confirm the effect of BDNF on neural activity. As a result, an increasing neurological function improvement was seen in NSC transplanted rats, which was associated with the upregulation of synaptophysin and BDNF expression. Moreover, transplantation of BDNF knockdown NSCs and BDNF antibody block reduced not only the level of synaptophysin but also exacerbated neurological function deficits. Microassay analysis showed that 14 genes such as Wnt and Gsk3-β were downregulated after BDNF knockdown. The present data therefore showed that BDNF-mediated neuroplasticity underlie the mechanism of NSC transplantation for the treatment of TBI in adult rats.

Effect of Fingolimod on Neural Stem Cells: A Novel Mechanism and Broadened Application for Neural Repair

Inflammatory demyelination and axonal damage of the CNS are hallmarks of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Fingolimod (FTY720), the first FDA-approved oral medication for MS, suppresses acute disease but is less effective at the chronic stage, and whether it has a direct effect on neuroregeneration in MS and EAE remains unclear. Here we show that FTY720, at nanomolar concentrations, effectively protected survival of neural stem cells (NSCs) and enhanced their development into mature oligodendrocytes (OLGs) in vitro, primarily through the S1P3 and S1P5 receptors. In vivo, treatment with either FTY720 or NSCs alone had no effect on the secondary progressive stage of remitting-relapsing EAE, but a combination therapy with FTY720 and NSCs promoted significant recovery, including ameliorated clinical signs and CNS inflammatory demyelination, enhanced MBP synthesis and remyelination, inhibited axonal degeneration, and reduced astrogliosis. Moreover, FTY720 significantly improved incorporation and survival of transplanted NSCs in the CNS and drove their differentiation into more OLGs but fewer astrocytes, thus promoting remyelination and CNS repair processes in situ. Our data demonstrate a novel effect of FTY720 on NSC differentiation and remyelination, broadening its possible application to NSC-based therapy in the secondary progressive stage of MS.

Transplantation of RADA16-BDNF peptide scaffold with human umbilical cord mesenchymal stem cells forced with CXCR4 and activated astrocytes for repair of traumatic brain injury

Due to the poor self-regeneration of brain tissue, stem cell transplantation therapy is purported to enable the replacement of lost neurons after traumatic brain injury (TBI). The main challenge of brain regeneration is whether the transplanted cells can survive and carry out neuronal functions in the lesion area. The brain is a complex neuronal network consisting of various types of cells that significantly influence on each other, and the survival of the implanted stem cells in brain is critically influenced by the surrounding cells. Although stem cell-based therapy is developing rapidly, most previous studies just focus on apply single type of stem cells as cell source. Here, we found that co-culturing human umbilical cord mesenchymal stem cells (hUC-MSCs) directly with the activated astrocytes benefited to the proliferation and neuron differentiation of hUC-MSCs in vitro. In this study, hUC-MSCs and the activated astrocytes were seeded in RADA16-BDNF peptide scaffold (R-B-SPH scaffold), a specifical self-assembling peptide hydrogel, in which the environment promoted the differentiation of typical neuron-like cells with neurites extending in three-dimensional directions. Moreover, the results showed co-culture of hUC-MSCs and activated astrocytes promoted more BDNF secretion which may benefit to both neural differentiation of ectogenic hUC-MSCs and endogenic neurogenesis. In order to promote migration of the transplanted hUC-MSCs to the host brain, the hUC-MSCs were forced with CXC chemokine receptor 4 (CXCR4). We found that the moderate-sized lesion cavity, but not the large cavity caused by TBI was repaired via the transplantation of hUC-MSCs^CXCR4 and activated astrocytes embedded in R-B-SPH scaffolds. The functional neural repair for TBI demonstrated in this study is mainly due to the transplantation system of double cells, hUC-MSCs and activated astrocytes. We believe that this novel cell transplantation system offers a promising treatment option for cell replacement therapy for TBI.

STATEMENT OF SIGNIFICANCE

In this reach, we specifically linked RGIDKRHWNSQ, a functional peptide derived from BDNF, to the C-terminal of RADARADARADARADA (RADA16) to structure a functional self-assembling peptide hydrogel scaffold, RADA16-BDNF (R-B-SPH scaffold) for the better transplantation of the double cell unit. Also, the novel scaffold was used as cell-carrier for transplantation double cell unit (hUC-MSCs/astrocyte) for treating traumatic brain injury. The results of this study showing that R-B-SPH scaffold was pliancy and flexibility to fit the brain lesion cavity and promotes the outgrowth of axons and dendrites of the neurons derived from hUC-MSCs in vitro and in vivo, indicating the 3D R-B-SPH scaffold provided a suitable microenvironment for hUC-MSC survival, proliferation and differentiation. Also, our results showing the double-cells transplantation system (hUC-MSCs/astrocyte) may be a novel cell-based therapeutic strategy for neuroregeneration after TBI with potential value for clinical application.

Trimethyltin intoxication induces the migration of ventricular/subventricular zone cells to the injured murine hippocampus

Following the postnatal decline of cell proliferation in the mammalian central nervous system, the adult brain retains progenitor cells with stem cell-like properties in the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampus. Brain injury can stimulate proliferation and redirect the migration pattern of SVZ precursor cells to the injury site. Sublethal exposure to the neurotoxicant trimethyltin (TMT) causes dose-dependent necrosis and apoptosis in the hippocampus dentate gyrus and increases SGZ stem cell proliferation to generate new granule cells. To determine whether SVZ cells also contribute to the repopulation of the TMT-damaged dentate gyrus, 6-8 week old male C3H mice were injected with the carbocyanine dye spDiI and bromodeoxyuridine (80mg/kg; ip.) to label ventricular cells prior to TMT exposure. The presence of labeled cells in hippocampus was determined 7 and 28days after TMT exposure. No significant change in the number of BrdU(+) and spDiI(+) cells was observed in the dentate gyrus 7days after TMT treatment. However, 28days after TMT treatment there was a 3-4 fold increase in the number of spDiI-labeled cells in the hippocampal hilus and dentate gyrus. Few spDiI(+) cells stained positive for the mature phenotypic markers NeuN or GFAP, suggesting they may represent undifferentiated cells. A small percentage of migrating cells were BrdU(+)/spDiI(+), indicating some newly produced, SVZ- derived precursors migrated to the hippocampus. Taken together, these data suggest that TMT-induced injury of the hippocampus can stimulate the migration of ventricular zone-derived cells to injured dentate gyrus.

Derivation of Neural Stem Cells from Mouse Induced Pluripotent Stem Cells

Neural stem cells (NSCs) derived from induced pluripotent stem cells offer therapeutic tools for neurodegenerative diseases. This review focuses on embryoid body (EB)-mediated stem cell culture techniques used to derive NSCs from mouse induced pluripotent stem cells (iPSCs). Generation of healthy and stable NSCs from iPSCs heavily depends on standardized in vitro cell culture systems that mimic the embryonic environments utilized during neural development. Specifically, the neural induction and expansion methods after EB formation are described in this review.

Development of a novel imaging system for cell therapy in the brain

Introduction

Stem cells have been evaluated as a potential therapeutic approach for several neurological disorders of the central and peripheral nervous system as well as for traumatic brain and spinal cord injury. Currently, the lack of a reliable and safe method to accurately and non-invasively locate the site of implantation and track the migration of stem cells in vivo hampers the development of stem cell therapy and its clinical application.

In this report, we present data that demonstrate the feasibility of using the human sodium iodide symporter (hNIS) as a reporter gene for tracking neural stem cells (NSCs) after transplantation in the brain by using single-photon emission tomography/computed tomography (SPECT/CT) imaging.

Methods

NSCs were isolated from the hippocampus of adult rats (Hipp-NSCs) and transduced with a lentiviral vector containing the hNIS gene. Hipp-NSCs expressing the hNIS (NIS-Hipp-NSCs) were characterized in vitro and in vivo after transplantation in the rat brain and imaged by using technetium-99m (^99mTc) and a small rodent SPECT/CT apparatus. Comparisons were made between Hipp-NSCs and NIS-Hipp-NSCs, and statistical analysis was performed by using two-tailed Student’s t test.

Results

Our results show that the expression of the hNIS allows the repeated visualization of NSCs in vivo in the brain by using SPECT/CT imaging and does not affect the ability of Hipp-NSCs to generate neuronal and glial cells in vitro and in vivo.

Conclusions

These data support the use of the hNIS as a reporter gene for non-invasive imaging of NSCs in the brain. The repeated, non-invasive tracking of implanted cells will accelerate the development of effective stem cell therapies for traumatic brain injury and other types of central nervous system injury.

Apoptosis in glioma-bearing rats after neural stem cell transplantation

Abnormal activation of the Ras/Raf/Mek/Erk signaling cascade plays an important role in glioma. Inhibition of this aberrant activity could effectively hinder glioma cell proliferation and promote cell apoptosis. To investigate the mechanism of glioblastoma treatment by neural stem cell transplantation with respect to the Ras/Raf/Mek/Erk pathway, C6 glioma cells were prepared in suspension and then infused into the rat brain to establish a glioblastoma model. Neural stem cells isolated from fetal rats were then injected into the brain of this glioblastoma model. Results showed that Raf-1, Erk and Bcl-2 protein expression significantly increased, while Caspase-3 protein expression decreased. After transplantation of neural stem cells, Raf-1, Erk and Bcl-2 protein expression significantly decreased, while Caspase-3 protein expression significantly increased. Our findings indicate that transplantation of neural stem cells may promote apoptosis of glioma cells by inhibiting Ras/Raf/Mek/Erk signaling, and thus may represent a novel treatment approach for glioblastoma.

A novel bioactive peptide: assessing its activity over murine neural stem cells and its potential for neural tissue engineering

The design of biomimetic scaffolds suitable for cell-based therapies is a fundamental step for the regeneration of the damaged nervous system; indeed growing interest is focusing on the discovery of peptide sequences to modulate the fate of transplanted cells and, in particular, the differentiation outcome of multipotent neural stem cells. By applying the Phage Display technique to murine neural stem cells we isolated a peptide, KLPGWSG, present in proteins involved in both stem cell maintenance and differentiation. We show that KLPGWSG binds molecules expressed on the cell surface of murine adult neural stem cells, thus may potentially be involved in stem cell fate determination. Indeed we demonstrated that this peptide in solution enhances per se cell differentiation toward the neuronal phenotype. Hence, we synthesized two LDLK-12-based self-assembling peptides functionalized with KLPGWSG peptide (KLP and Ac-KLP) and characterized them via atomic force microscopy, rheometry and circular dichroism, obtaining nanostructured hydrogels supporting murine neural stem cells differentiation in vitro. Interestingly, we demonstrated that, when scaffold stiffness is comparable to that of the brain in vivo, the Ac-KLP SAP-based scaffold enhances the neuronal differentiation of neural stem cells. These evidences place both KLPGWSG and the functionalized self-assembling peptide Ac-KLP as promising candidates for, respectively, biomimetic studies and stem cell therapies for nervous regeneration.

[Stem cell-based treatment of neurologic diseases]

Therapeutic strategies based on stem cells are being increasingly used to treat a wide range of neurological diseases. Although these strategies were initially designed to replace dead cells in injured tissue, the potential of stem cells to migrate, secrete trophic factors, and immunomodulate allows their therapeutic use as a vehicle for gene therapy, as in Parkinson's disease, or as immunomodulators and neuroprotectors in diseases such as multiple sclerosis. This review will focus on current clinical and experimental evidence on the treatment of neurological disorders with strategies based on stem cells.

Olig1 function is required for remyelination potential of transplanted neural progenitor cells in a model of viral-induced demyelination

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) resulting in cumulative neurologic deficits associated with progressive myelin loss. We have previously shown that transplantation of neural progenitor cells (NPCs) into mice persistently infected with the JHM strain of mouse hepatitis virus (JHMV) results in enhanced differentiation into oligodendrocyte progenitor cells (OPCs) that is associated with remyelination and axonal sparing. The current study examines the contributions of the transcription factor Olig1 on NPC differentiation and remyelination. Under defined conditions, NPCs preferentially differentiate into oligodendroglia whereas NPCs isolated from Olig1-deficient (Olig1-/-) mice exhibit enhanced differentiation into astrocytes. Transplantation of Olig1-/- and Olig1+/+ NPCs into JHMV-infected mice resulted in similar cell survival, proliferation, and selective migration to areas of demyelination. However, only recipients of wild type NPCs exhibited extensive remyelination compared to mice receiving Olig1-/- NPCs. In vivo characterization of NPCs revealed that Olig1+/+ NPCs preferentially differentiated into NG2-positive OPCs and formed processes expressing myelin basic protein that encircled axons. In contrast, the majority of transplanted Olig1-/- NPCs differentiated into GFAP-positive cells consistent with the astrocyte lineage. These results indicate that exogenous NPCs contribute to improved clinical and histological outcome and this is associated with remyelination by this donor population. Further, these findings reveal that Olig1function is required for the remyelination potential of NPCs after transplant, through specification and/or maintenance of oligodendroglial identity.

Colloids as mobile substrates for the implantation and integration of differentiated neurons into the mammalian brain

Neuronal degeneration and the deterioration of neuronal communication lie at the origin of many neuronal disorders, and there have been major efforts to develop cell replacement therapies for treating such diseases. One challenge, however, is that differentiated cells are challenging to transplant due to their sensitivity both to being uprooted from their cell culture growth support and to shear forces inherent in the implantation process. Here, we describe an approach to address these problems. We demonstrate that rat hippocampal neurons can be grown on colloidal particles or beads, matured and even transfected in vitro, and subsequently transplanted while adhered to the beads into the young adult rat hippocampus. The transplanted cells have a 76% cell survival rate one week post-surgery. At this time, most transplanted neurons have left their beads and elaborated long processes, similar to the host neurons. Additionally, the transplanted cells distribute uniformly across the host hippocampus. Expression of a fluorescent protein and the light-gated glutamate receptor in the transplanted neurons enabled them to be driven to fire by remote optical control. At 1-2 weeks after transplantation, calcium imaging of host brain slice shows that optical excitation of the transplanted neurons elicits activity in nearby host neurons, indicating the formation of functional transplant-host synaptic connections. After 6 months, the transplanted cell survival and overall cell distribution remained unchanged, suggesting that cells are functionally integrated. This approach, which could be extended to other cell classes such as neural stem cells and other regions of the brain, offers promising prospects for neuronal circuit repair via transplantation of in vitro differentiated, genetically engineered neurons.

Neural stem cell gene therapy ameliorates pathology and function in a mouse model of globoid cell leukodystrophy

Murine neural stem cells (mNSCs), either naive or genetically modified to express supranormal levels of β-galactocerebrosidase (GALC), were transplanted into the brain of Twitcher mice, a murine model of globoid cell leukodystrophy, a severe sphingolipidosis. Cells engrafted long-term into the host cytoarchitecture, producing functional GALC. Levels of enzyme activity in brain and spinal cord tissues were enhanced when GALC-overexpressing NSC were used. Enzymatic correction correlated with reduced tissue storage, decreased activation of astroglia and microglia, delayed onset of symptoms, and longer lifespan. Mechanisms underlying the therapeutic effect of mNSC included widespread enzyme distribution, cross-correction of host cells, anti-inflammatory activity, and neuroprotection. Similar cell engraftment and metabolic correction were reproduced using human NSC. Thus, NSC gene therapy rapidly reconstitutes sustained and long-lasting enzyme activity in central nervous system tissues. Combining this approach with treatments targeting the systemic disease associated with leukodystrophies may provide significant therapeutic benefit. Stem Cells 2011;29:1559–1571

Predifferentiated brain-derived adult human progenitor cells migrate toward ischemia after transplantation to the adult rat brain

BACKGROUND

The adult human brain contains neural stem/progenitor cells (AHNPCs) that can survive transplantation into the adult rat brain, migrate toward a lesion, and display limited neuronal differentiation in vivo.

OBJECTIVE

To investigate the effect of manipulating AHNPCs before grafting by predifferentiation, ie, initiating neuronal differentiation before transplantation, and to determine whether this cell priming would affect their ability to migrate in vivo.

METHODS

AHNPCs were prepared from temporal lobe resections for epilepsy. Seven days after global brain ischemia, predifferentiated AHNPCs (exposed to basic fibroblast growth factor, heparin, and laminin) were transplanted to the left hippocampus. Four and 10 weeks after transplantation, brain sections were analyzed by immunohistochemistry.

RESULTS

Transplanted primed cells expressed committed neuronal markers at a much earlier stage compared with nonprimed AHNPCs and were found colabeled with human markers within the damaged CA1 region 4 weeks after grafting. Furthermore, predifferentiated AHNPCs migrated preferentially into an ischemic lesion, similar to their undifferentiated counterparts. The chemoattractant effect from the expression of stromal cell-derived factor-1α (SDF-1α) in ischemic CA1 on AHNPCs expressing CXC chemokine receptor 4 (CXCR4) may explain this preference in migration in vivo.

CONCLUSION

The plasticity of neural progenitors derived from the adult human brain may be greater than previously assumed in that manipulation before grafting may influence the phenotypes seen in vivo. The SDF-1α-CXCR4 axis is involved in the targeted migration toward an ischemic lesion in the adult rat brain, similar to previous reports on endogenous progenitors in rats and grafted fetal human neural progenitors.

Evaluation of bone marrow- and brain-derived neural stem cells in therapy of central nervous system autoimmunity

Adult subventricular zone (SVZ)-derived neural stem cells (NSCs) have therapeutic effects in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, SVZ precursor cells as a source of NSCs are not readily accessible for clinical application. In the present study, we demonstrate that NSCs derived from bone marrow (BM) cells exhibit comparable morphological properties as those derived from SVZ cells and possess a similar ability to differentiate into neurons, astrocytes, and oligodendrocytes both in vitro and in vivo. Importantly, both types of NSCs suppressed chronic experimental autoimmune encephalomyelitis to a comparable extent on transplantation. Mechanisms underlying the therapeutic effects of NSCs include immunomodulation in the periphery and the central nervous system (CNS), neuron/oligodendrocyte repopulation by transplanted cells, and enhanced endogenous remyelination and axonal recovery. Furthermore, we provide evidence for the trans-differentiation of transplanted BM-NSCs into neural cells in the CNS, while no fusion of these cells with host neural cells was detected. This is the first study that directly compares SVZ- versus BM-NSCs with regard to in vivo neural differentiation and anti-inflammatory and therapeutic effects on CNS inflammatory demyelination. Their virtually identical therapeutic potential, greater accessibility, and autologous properties make BM-NSCs a novel and highly applicable substitute for SVZ-NSCs in cell-based multiple sclerosis therapies.

Neuropathology of olfactory ensheathing cell transplantation into the brain of two amyotrophic lateral sclerosis (ALS) patients

Although a large number of amyotrophic lateral sclerosis (ALS) patients have undergone transplantation procedures with olfactory ensheathing cells (OECs) in the Bejing Hospital, to our knowledge, no post-mortem neuropathologic analyses have been performed. We examined the post-mortem brain of two Italian patients affected by ALS who underwent cellular transplantation in Beijing with their consent. Our aim was to assess the events following the graft procedure to possibly support the rationale of the treatment strategy. The neuropathologic findings were analyzed on the basis of the limited awareness of the experimental conditions and discussed in relation to the safety, efficacy and long-term outcome of the transplanted cells. Islands of quiescent, undifferentiated cells within the delivery track persisting for up to 12 months-24 months were found. Prominent glial and inflammatory reaction around the delivery track strongly supports the encasement of the graft. Evidence of axonal regeneration, neuronal differentiation and myelination was not seen. The surgical procedure of implantation was not compatible with a neurotrophic effect. The OEC transplantation did not modify the neuropathology of ALS in the two patients. In conclusion, the present neuropathologic analysis does not support a beneficial effect of fetal OEC implantation into the frontal lobes of ALS patients.

Effects of FGF receptor peptide agonists on animal behavior under normal and pathological conditions

Hexafins are recently identified low-molecular-weight peptide agonists of the fibroblast growth factor receptor (FGFR), derived from the beta6-beta7 loop region of various FGFs. Synthetic hexafin peptides have been shown to bind to and induce tyrosine phosphorylation of FGFR1, stimulate neurite outgrowth, and promote neuronal survival in vitro. Thus, the pronounced biological activities of hexafins in vitro make them attractive compounds for pharmacological studies in vivo. The present study investigated the effects of subcutaneous administration of hexafin1 and hexafin2 (peptides derived from FGF1 and FGF2, respectively) on social memory, exploratory activity, and anxiety-like behavior in adult rats. Treatment with hexafin1 and hexafin2 resulted in prolonged retention of social memory. Furthermore, rats treated with hexafin2 exhibited decreased anxiety-like behavior in the elevated plus maze. Employing an R6/2 mouse model of Huntington's disease (HD), we found that although hexafin2 did not affect the progression of motor symptoms, it alleviated deficits in activity related to social behavior, including sociability and social novelty. Thus, hexafin2 may have therapeutic potential for the treatment of HD.

Embryonic stem cells promote motor recovery and affect inflammatory cell infiltration in spinal cord injured mice

The purpose of this study was to determine the fate and the effects of undifferentiated embryonic stem cells (ESCs) in mice after contusive lesion of the spinal cord (SCI). Reproducible traumatic lesion to the cord was performed at T8 level by means of the Infinite Horizon Device, and was followed by intravenous injection of one million of undifferentiated ESCs through the tail vein within 2 h from the lesion. The ESCs-treated animals showed a significant improvement of the recovery of motor function 28 days after lesion, with an average score of 4.61+/-0.13 points of the Basso Mouse Scale (n=14), when compared to the average score of vehicle treated mice, 3.58+/-0.23 (n=10). The number of identified ESCs found at the lesion site was 0.6% of the injected cells at 1 week after transplantation, and further reduced to 0.04% at 1 month. It is, thus, apparent that the promoted hind-limb recovery cannot be correlated to a substitution of the lost tissue performed by the exogenous ESC. The extensive evaluation of production of several neuroprotective and inflammatory cytokines did not reveal any effect by ESC-treatment, but unexpectedly the number of invading macrophages and neutrophils was greatly reduced. This may explain the improved preservation of lesion site ventral myelin, at both 1 week (29+/-11%) and 1 month (106+/-14%) after injury. No teratoma formation was observed, although an inappropriate colonization of the sacral cord by differentiated nestin- and beta-tubulin III-positive ESCs was detected.

Systemic neurotransplantation--a problem-oriented systematic review

Systemic neurotransplantation (SNT) was introduced in the laboratory in 2000 and currently it is being widely examined in animal models of neurological disorders. The aim of this systematic review was to evaluate the current state of knowledge in the field of experimental SNT and the premise for the introduction of clinical trials. PubMed was searched and 60 articles utilizing an SNT approach were found and subjected to analysis. The time window for cell transplantation was addressed in only two studies, with contradictory results. Immunosuppression was applied in 25% of studies. No study addressed the justification for immunosuppression. Bone marrow was the most frequent source of grafted cells, followed by cord blood and then by cells of embryonic origin. Studies investigating dose-dependency revealed no satisfactory results with transplantation of less than 10(6) cells/animal; the efficient dose most frequently ranged from 10(6)-10(7) cells/animal (mice and rats). The behavioral effects of cell transplantation were assessed in 75% of all studies; significant improvement was achieved in 95% of them. Morphological effect was evaluated in half of the studies; significant positive effect was achieved in 73% of them. Experimental attempts to elucidate the mechanisms mediating cell-dependent effect were not undertaken in half of the studies. In the other half, the most frequent mechanisms were growth factors, neurogenesis and immunomodulation. SNT still seems to be at the very initial stage of development. Many critical factors have not been sufficiently addressed in laboratory studies and they must be clarified before the introduction of clinical trials.

Neural stem cells: mechanisms of fate specification and nuclear reprogramming in regenerative medicine

Recently, intense interest in the potential use of neural stem cells (NSC) in the clinical therapy of brain disease and injury has resulted in rapid progress in research on the properties of NSC, their innate and directed differentiation potential and the induced reprogramming of differentiated somatic cells to revert to a pluripotent NSC-like state. The aim of this review is to give an overview of our current operational definitions of the NSC lineage, the growing understanding of extrinsic and intrinsic mechanisms, including heritable but reversible epigenetic chromatin modifications that regulate the maintenance and differentiation of NSC in vivo, and to emphasize ground-breaking efforts of cellular reprogramming with the view to generating patient-specific stem cells for cell replacement therapy. This is set against a summary of current practical procedures for the isolation, research and application of NSC, and of the state of the art in NSC-based regenerative medicine of the nervous system. Both provide the backdrop for the translation of recent findings into innovative clinical applications, with the hope of increasing the safety, efficiency and ethical acceptability of NSC-based therapies in the near future.

Gene and cell delivery to the degenerated striatum: status of preclinical efforts in primate models

Significant progress has been achieved in developing restorative neurosurgical strategies for movement disorders on the basis of preclinical gene and cell therapy experiments in primates. Because of the unique similarities between human and primate anatomy and physiology, experiments in primate models are the critical step in translating these innovative neurosurgical treatment concepts into successful human applications. To clarify progress toward this goal, we have examined recent preclinical data regarding the delivery of gene and cell therapy to the lesioned primate striatum. Improved behavioral outcomes after in vivo gene transduction, achieved by brain delivery of adeno-associated vectors, have resulted in the initiation of ongoing clinical trials. Cell transplantation experiments are transitioning from the grafting of fetal tissue, which has met with mixed clinical success, to the grafting of expanded neural stem cells, for which preliminary results in primates are encouraging. Careful attention to the surgical delivery parameters for these agents in primate studies, along with the ability to realistically model imaging and behavioral outcomes in these animals, is essential for optimizing the restoration of function for patients. The authors review data obtained from primate models that form the basis for ongoing clinical trials to consider how new preclinical models should be developed to answer questions that arise from experimental clinical data.

Behavior of hippocampal stem/progenitor cells following grafting into the injured aged hippocampus

Multipotent neural stem/progenitor cells (NSCs) from the embryonic hippocampus are potentially useful as donor cells to repopulate the degenerated regions of the aged hippocampus after stroke, epilepsy, or Alzheimer's disease. However, the efficacy of the NSC grafting strategy for repairing the injured aged hippocampus is unknown. To address this issue, we expanded FGF-2-responsive NSCs from the hippocampus of embryonic day 14 green fluorescent protein-expressing transgenic mice as neurospheres in vitro and grafted them into the hippocampus of 24-month-old F344 rats 4 days after CA3 region injury. Engraftment, migration, and neuronal/glial differentiation of cells derived from NSCs were analyzed 1 month after grafting. Differentiation of neurospheres in culture dishes or after placement on organotypic hippocampal slice cultures demonstrated that these cells had the ability to generate considerable numbers of neurons, astrocytes, and oligodendrocytes. Following grafting into the injured aged hippocampus, cells derived from neurospheres survived and dispersed, but exhibited no directed migration into degenerated or intact hippocampal cell layers. Phenotypic analyses of graft-derived cells revealed neuronal differentiation in 3%-5% of cells, astrocytic differentiation in 28% of cells, and oligodendrocytic differentiation in 6%-10% cells. The results demonstrate for the first time that NSCs derived from the fetal hippocampus survive and give rise to all three CNS phenotypes following transplantation into the injured aged hippocampus. However, grafted NSCs do not exhibit directed migration into lesioned areas or widespread neuronal differentiation, suggesting that direct grafting of primitive NSCs is not adequate for repair of the injured aged brain without priming the microenvironment.

Setting the conditions for efficient, robust and reproducible generation of functionally active neurons from adult subventricular zone-derived neural stem cells

Although new culture conditions enable homogeneous and long-term propagation of radial glia-like neural stem (NS) cells in monolayer and serum-free conditions, the efficiency of the conversion of NS cells into terminally differentiated, functionally mature neurons is relatively limited and poorly characterized. We demonstrate that NS cells derived from adult mouse subventricular zone robustly develop properties of mature neurons when exposed to an optimized neuronal differentiation protocol. A high degree of cell viability was preserved. At 22 days in vitro, most cells (65%) were microtubule-associated protein 2(+) and coexpressed gamma-aminobutyric acid (GABA), GAD67, calbindin and parvalbumin. Nearly all neurons exhibited sodium, potassium and calcium currents, and 70% of them fired action potentials. These neurons expressed functional GABA(A) receptors, whereas activable kainate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartic acid receptors were present in approximately 80, 30 and 2% of cells, respectively. Antigenic and functional properties were efficiently and reliably reproduced across experiments and cell passages (up to 68). This is the first report showing a consistent and reproducible generation of large amounts of neurons from long-term passaged adult neural stem cells. Remarkably, the neuronal progeny carries a defined set of antigenic, biochemical and functional characteristics that make this system suitable for studies of NS cell biology as well as for genetic and chemical screenings.

Reduction of brain injury in neonatal hypoxic-ischemic rats by intracerebroventricular injection of neural stem/progenitor cells together with chondroitinase ABC

Perinatal hypoxia-ischemia (HI) remains a critical issue. Cell transplantation therapy could be a potent treatment for many neurodegenerative diseases, but limited works on this kind of therapy have been reported for perinatal HI. In this study, the therapeutic effect of transplantation with neural stem/ progenitor cells (NSPCs) and chondrotinase ABC (ChABC) in a neonatal HI rat model is evaluated. Histological studies showed that the unaffected area of the brain in animals treated with NSPCs together with ChABC was significantly larger than that in the animals treated with vehicle or NSPCs alone. The wet weight of the brain that received the combined treatment was also significantly higher than those of the vehicle and their individual treatments. These results indicate that intracerebroventricular injection of NSPCs with ChABC reduces brain injury in a rat neonatal HI model.

Sertraline slows disease progression and increases neurogenesis in N171-82Q mouse model of Huntington's disease

Huntington's disease (HD) is an inherited progressive neurodegenerative disorder resulting from CAG repeat expansion in the gene that encodes for the protein huntingtin. To identify neuroprotective compound (s) that can slow down disease progression and can be administered long term with few side effects in Huntington's disease, we investigated the effect of sertraline, a selective serotonin reuptake inhibitor (SSRI) which has been shown to upregulate BDNF levels in rodent brains. We report here that in HD mice sertraline increased BDNF levels, preserved chaperone protein HSP70 and Bcl-2 levels in brains, attenuated the progression of brain atrophy and behavioral abnormalities and thereby increased survival. Sertraline also enhanced neurogenesis, which appeared to be responsible for mediating the beneficial effects of sertraline in HD mice. Additionally, the effective levels of sertraline are comparable to the safe levels achievable in humans. The findings suggest that sertraline is a potential candidate for treatment of HD patients.

Novel and immortalization-based protocols for the generation of neural CNS stem cell lines for gene therapy approaches

Transplantation of neural cells engineered to produce growth factors or molecules with antitumor effects have the potential of grafted cells to be used as vectors for protein delivery in animal models of diseases. In this context, neural stem cells (NSCs), since their identification, have been considered an attractive subject for therapeutic applications to the damaged brain. NSCs have been shown to include attributes important for potential successful ex vivo gene therapy approaches: they show extensive in vitro expansion and, in some cases, a particular tropism toward pathological brain areas. Clearly, the challenges for future clinical development of this approach are in the definition of the most appropriate stem cells for a given application, what genes or chemicals can be delivered, and what diseases are suitable targets. Ideally, NSC lines should be homogeneous and well characterized in terms of their in vitro stability and grafting capacity. We discuss two possible approaches to produce homogeneous and stable progenitor and NSC lines that exploit an oncogene-based immortalization, or, in the second case, a novel protocol for growth factor expansion of stem cells with radial glia-like features. Furthermore, we describe the use of retroviral particles for genetic engineering.

Developing cell transplantation for temporal lobe epilepsy

Mesial temporal lobe epilepsy (MTLE) is presumed to develop progressively as a consequence of synaptic reorganization and neuronal loss, although the exact etiology of seizure development is unknown. Nearly 30% of patients with MTLE have disabling seizures despite pharmacological treatment, and the majority of these patients are recommended for resection. The authors review cell transplantation as an alternative approach to the treatment of epilepsy. Recent work in animal models shows that grafted neuronal precursors that differentiate into inhibitory interneurons can increase the level of local inhibition. Grafts of these inhibitory neurons could help restore equilibrium in MTLE. Developing a sound transplantation strategy involves careful consideration of the etiology of MTLE and the expected functional role of transplanted cells. These issues are reviewed, with a focus on those factors most likely to influence clinically applicable results.

Autologous transplants of Adipose-Derived Adult Stromal (ADAS) cells afford dopaminergic neuroprotection in a model of Parkinson's disease

Adult adipose contains stromal progenitor cells with neurogenic potential. However, the stability of neuronal phenotypes adopted by Adipose-Derived Adult Stromal (ADAS) cells and whether terminal neuronal differentiation is required for their consideration as alternatives in cell replacement strategies to treat neurological disorders is largely unknown. We investigated whether in vitro neural induction of ADAS cells determined their ability to neuroprotect or restore function in a lesioned dopaminergic pathway. In vitro-expanded naïve or differentiated ADAS cells were autologously transplanted into substantia nigra 1 week after an intrastriatal 6-hydroxydopamine injection. Neurochemical and behavioral measures demonstrated neuroprotective effects of both ADAS grafts against 6-hydroxydopamine-induced dopaminergic neuron death, suggesting that pre-transplantation differentiation of the cells does not determine their ability to survive or neuroprotect in vivo. Therefore, we investigated whether equivalent protection by naïve and neurally-induced ADAS grafts resulted from robust in situ differentiation of both graft types into dopaminergic fates. Immunohistological analyses revealed that ADAS cells did not adopt dopaminergic cell fates in situ, consistent with the limited ability of these cells to undergo terminal differentiation into electrically active neurons in vitro. Moreover, re-exposure of neurally-differentiated ADAS cells to serum-containing medium in vitro confirmed ADAS cell phenotypic instability (plasticity). Lastly, given that gene expression analyses of in vitro-expanded ADAS cells revealed that both naïve and differentiated ADAS cells express potent dopaminergic survival factors, ADAS transplants may have exerted neuroprotective effects by production of trophic factors at the lesion site. ADAS cells may be ideal for ex vivo gene transfer therapies in Parkinson's disease treatment.

Migration of transplanted neural progenitor cells in a ferret model of cortical dysplasia

Although altered gene expression clearly causes failure of the neocortex to form properly, many causes of neocortical dysplasia arise from environmental or unknown factors. Our lab studies a model of cortical dysplasia induced by injection of methylazoxymethanol (MAM) into pregnant ferrets on embryonic day 33 (E33), which shares many features of neocortical dysplasia in humans. E33 MAM treatment results in characteristic deficits that include dramatic reduction of layer 4 in somatosensory cortex, widespread termination of thalamic afferents, and altered distribution of GABAergic elements. We determined the ability of immature cells to migrate into MAM-treated cortex using ferret neural progenitor cells obtained at E27 and E33 and mouse neural progenitor cells obtained at E14. When these cells were transplanted into organotypic cultures obtained from normal and E33 MAM-treated ferret cortex prepared on postnatal day 0 (P0), all progenitor cells migrated similarly in both hosts, preferentially residing in the upper cortical plate. The site of transplantation was significant, however, so that injections into the ventricular zone were more likely to reach the cortical plate than transplants into the intermediate zone. When similar cells were transplanted into ferret kits, approximately P7-P9, and allowed to survive for 2-4 weeks, the donor cells migrated differently and also reached distinct destinations in normal and MAM-treated hosts. MAM-treated cortex was more permissive to invasion by donor cells as they migrated to widespread aspects of the cortex, whereas transplants in normal host cortex were more restricted. E27 neural progenitor cells populated more cortical layers than later born E33 neural progenitor cells, suggesting that the fate of transplanted cells is governed by a combination of extrinsic and intrinsic factors.

Transplantation of rat neural stem cells reduces stereotypic behaviors in rats after intrastriatal microinfusion of Tourette syndrome sera

Tourette syndrome (TS) is a heterogenous neuropsychiatric disorder. In most cases, tics are self-limited or can be treated by behavioral or pharmacological therapy. However, for some individuals, tics can cause lifelong impairment and life-threatening symptoms, which are intractable to traditional treatment. Neural stem cell (NSC) is a potential tool to treat certain neurological diseases. In this study, we proposed to use neural stem cell transplantation as a novel therapy to treat TS and discussed its efficacy. Wistar rats were microinfused with TS sera into the striatum followed by the transplantation of NSCs or vehicle at the infusion site. The sera of the TS patients were identified to have enriched antineural antibodies. Prior to grafting, rat embryonic NSCs were co-cultured with 5-bromodeoxyuridine (Brdu) for 24 h. Stereotypic behaviors were counted at 1, 7, 14 and 21 days after transplantation of NSCs. Morphological analyses revealed that NSCs survived and differentiated into neurons and astrocytes in the striatum 3 weeks after grafting. To sum it up, rat embryonic neural stem cell grafts survived and differentiated in the striatum of TS rat may help relieve stereotypic behaviors of the host. Our results suggest that transplantation of NSCs intrastriatum may have therapeutic potential for TS.

Transplantation of foetal neural stem cells into the rat hippocampus during trimethyltin-induced neurodegeneration

The present study investigates the survival and fate of neural stem cells/progenitor cells (NSC/NPCs) homografted into the hippocampus of rats treated with trimethyltin (TMT), a potent neurotoxicant considered a useful tool to obtain a well characterized model of neurodegeneration, to evaluate their possible role in the reparative mechanisms that accompany neurodegenerative events. NSC/NPCs expressing eGFP by lentivirus-mediated infection were stereotaxically grafted into the hippocampus of TMT-treated animals and controls. Two weeks after transplantation surviving NSC/NPCs were detectable in 60% of TMT-treated animals and 30% of controls, while 30 days after transplantation only 40% of TMT-treated animals showed surviving grafted cells, which were undetectable in controls. At both times investigated, while grafted NSC/NPCs differentiated into neurons or astrocytes could be observed in addition to undifferentiated NSC/NPCs, we did not find evidence of structural integration of grafted cells into the main site of hippocampal lesion leading to appreciable repair.

Isolation and characterization of murine neural stem/progenitor cells based on Prominin-1 expression

The identification of strategies for the isolation of neural stem cells (NSCs) has important implications for the understanding of their biology and the development of therapeutic applications. It has been previously described that human neural stem and progenitor cells (NSPCs) can be isolated from the central nervous system (CNS) using antibodies to prominin (CD133) and fluorescence-activated cell sorting (FACS). Although this antigen displayed an identical membrane topology in several human and murine tissues there was uncertainty as to the relationship between human and mouse prominin because of the low level of amino acid identity. Here we show that prominin expression can be used to identify and isolate also murine NSPCs from the developing or adult brain. Prominin is co-expressed with known neural stem markers like SOX 1-2, Musashi and Nestin. Moreover, neurosphere-forming cells with multipotency and self-renewal capacity reside within the prominin-positive fraction. Transplantation experiments show that CD133-positive cells give rise to neurons and glial cells in vivo, and that many neurons display appropriate phenotypic characteristics of the recipient tissues. The demonstration that CD133 is a stem cell antigen for murine NSPCs as it is for human NSPCs is useful for the investigation of mammal neurogenesis and development of preclinical tests of NSPCs transplantation in mouse analogues of human diseases.

Differential development of neuronal physiological responsiveness in two human neural stem cell lines

BACKGROUND

Neural stem cells (NSCs) are powerful research tools for the design and discovery of new approaches to neurodegenerative disease. Overexpression of the myc family transcription factors in human primary cells from developing cortex and mesencephalon has produced two stable multipotential NSC lines (ReNcell VM and CX) that can be continuously expanded in monolayer culture.

RESULTS

In the undifferentiated state, both ReNcell VM and CX are nestin positive and have resting membrane potentials of around -60 mV but do not display any voltage-activated conductances. As initially hypothesized, using standard methods (stdD) for differentiation, both cell lines can form neurons, astrocytes and oligodendrocytes according to immunohistological characteristics. However it became clear that this was not true for electrophysiological features which designate neurons, such as the firing of action potentials. We have thus developed a new differentiation protocol, designated 'pre-aggregation differentiation' (preD) which appears to favor development of electrophysiologically functional neurons and to lead to an increase in dopaminergic neurons in the ReNcell VM line. In contrast, the protocol used had little effect on the differentiation of ReNcell CX in which dopaminergic differentiation was not observed. Moreover, after a week of differentiation with the preD protocol, 100% of ReNcell VM featured TTX-sensitive Na+-channels and fired action potentials, compared to 25% after stdD. Currents via other voltage-gated channels did not appear to depend on the differentiation protocol. ReNcell CX did not display the same electrophysiological properties as the VM line, generating voltage-dependant K+ currents but no Na+ currents or action potentials under either stdD or preD differentiation.

CONCLUSION

These data demonstrate that overexpression of myc in NSCs can be used to generate electrophysiologically active neurons in culture. Development of a functional neuronal phenotype may be dependent on parameters of isolation and differentiation of the cell lines, indicating that not all human NSCs are functionally equivalent.

Epigenetic signatures of stem-cell identity

Pluripotent stem cells, similar to more restricted stem cells, are able to both self-renew and generate differentiated progeny. Although this dual functionality has been much studied, the search for molecular signatures of 'stemness' and pluripotency is only now beginning to gather momentum. While the focus of much of this work has been on the transcriptional features of embryonic stem cells, recent studies have indicated the importance of unique epigenetic profiles that keep key developmental genes 'poised' in a repressed but activatable state. Determining how these epigenetic features relate to the transcriptional signatures of ES cells, and whether they are also important in other types of stem cell, is a key challenge for the future.

Merging fields: stem cells in neurogenesis, transplantation, and disease modeling

Traditionally, applied stem cell research has been segregating into strategies aiming at endogenous repair and cell transplantation. Recent advances in both fields have unraveled unexpected potential for synergy between these disparate fields. The increasing dissection of the step-wise integration of adult-born neurons into an established brain circuitry provides a highly informative blueprint for the functional incorporation of grafted neurons into a host brain. On the other hand, in vitro recapitulation of developmental differentiation cascades permits the de novo generation of various neural cell types from pluripotent embryonic stem (ES) cells. Advanced tools in stem cell engineering enable not only genetic selection and instruction of disease-specific donor cells for neural replacement but also the exploitation of stem cells as transgenic cellular model systems for human diseases. In a comparative approach we here illuminate the functional integration of neurons derived from endogenous and transplanted stem cells, the evolving technologies for advanced stem cell engineering and the impact of cloned and mutated stem cells on disease modeling.