Neurospheres modified to produce glial cell line-derived neurotrophic factor increase the survival of transplanted dopamine neurons

Therapeutic hypothermia modulates the neurogenic response of the newborn piglet subventricular zone after hypoxia-ischemia

BACKGROUND

Neuroprotection combined with neuroregeneration may be critical for optimizing functional recovery in neonatal encephalopathy. To investigate the neurogenic response to hypoxia-ischemia (HI) followed by normothermia (38.5 °C) or three different hypothermic temperatures (35, 33.5, or 30 °C) in the subventricular zone (SVZ) of the neonatal piglet.

METHODS

Following transient cerebral HI and resuscitation, 28 newborn piglets were randomized to: normothermia or whole-body cooling to 35 °C, 33.5 °C, or 30 °C during 2-26 h (all n = 7). At 48 h, piglets were euthanized and SVZ obtained to evaluate its cellularity, pattern of cell death, radial glia length, doublecortin (DCX, neuroblasts) expression, and Ki67 (cell proliferation) and Ki67/Sox2 (neural stem/progenitor dividing) cell counts.

RESULTS

Normothermic piglets showed lower total (Ki67+) and neural stem/progenitor dividing (Ki67+Sox2+) cell counts when compared to hypothermic groups. Cooling to 33.5 °C obtained the highest values of SVZ cellularity, radial glia length processes, neuroblast chains area and DCX immunohistochemistry. Cooling to 30 °C, however, revealed decreased cellularity in the lateral SVZ and shorter radial glia processes when compared with 33.5 °C.

CONCLUSIONS

In a neonatal piglet model, hypothermia to 33.5 °C modulates the neurogenic response of the SVZ after HI, highlighting the potential beneficial effect of hypothermia to 33.5 °C on endogenous neurogenesis and the detrimental effect of overcooling beyond this threshold.

IMPACT

Neuroprotection combined with neuroregeneration may be critical for optimizing functional recovery in neonatal encephalopathy. Hypothermia may modulate neurogenesis in the subventricular zone (SVZ) of the neonatal hypoxic-ischemic piglet. Cooling to 33.5 °C obtained the highest values of SVZ cellularity, radial glia length processes, neuroblast chains area and doublecortin immunohistochemistry; cooling to 30 °C, however, revealed decreased cellularity and shorter radial glia processes. In a neonatal piglet model, therapeutic hypothermia (33.5 °C) modulates the neurogenic response of the SVZ after hypoxia-ischemia, highlighting also the detrimental effect of overcooling beyond this threshold.

The Endocannabinoid System as a Target for Neuroprotection/Neuroregeneration in Perinatal Hypoxic-Ischemic Brain Injury

The endocannabinoid (EC) system is a complex cell-signaling system that participates in a vast number of biological processes since the prenatal period, including the development of the nervous system, brain plasticity, and circuit repair. This neuromodulatory system is also involved in the response to endogenous and environmental insults, being of special relevance in the prevention and/or treatment of vascular disorders, such as stroke and neuroprotection after neonatal brain injury. Perinatal hypoxia-ischemia leading to neonatal encephalopathy is a devastating condition with no therapeutic approach apart from moderate hypothermia, which is effective only in some cases. This overview, therefore, gives a current description of the main components of the EC system (including cannabinoid receptors, ligands, and related enzymes), to later analyze the EC system as a target for neonatal neuroprotection with a special focus on its neurogenic potential after hypoxic-ischemic brain injury.

Neural Stem/Progenitor Cell Transplantation in Parkinson's Rodent Animals: A Meta-Analysis and Systematic Review

The effects of neural stem/progenitor cells (NSPCs) have been extensively evaluated by multiple studies in animal models of Parkinson's disease (PD), but the therapeutic efficacy was inconsistent. Here, we searched 4 databases (PubMed, Embase, Scopus, and Web of Science) and performed a meta-analysis to estimate the therapeutic effects of unmodified NSPCs on neurological deficits in rodent animal models of PD. Data on study quality score, behavioral outcomes (apomorphine or amphetamine-induced rotation and limb function), histological outcome (densitometry of TH+ staining in the SNpc), and cell therapy-related severe adverse events were extracted for meta-analysis and systematic review. Twenty-one studies with a median quality score of 6 (range from 4 to 9) in 11 were examined. Significant improvement was observed in the overall pooled standardized mean difference (SMD) between animals transplanted with NSPCs and with control medium (1.22 for apomorphine-induced rotation, P < .001; 1.50 for amphetamine-induced rotation, P < .001; 0.86 for limb function, P < .001; and -1.96 for the densitometry of TH+ staining, P < .001). Further subgroup analysis, animal gender, NSPCs source, NSPCs dosage, and pretreatment behavioral assessment were closely correlated with apomorphine-induced rotation and amphetamine-induced rotation. In conclusion, unmodified NSPCs therapy attenuated behavioral deficits and increased dopaminergic neurons in rodent PD models, supporting the consideration of early-stage clinical trial of NSPCs in patients with PD.

Stem cell transplantation and/or adenoviral glial cell line-derived neurotrophic factor promote functional recovery in hemiparkinsonian rats

BACKGROUND

Parkinson’s disease (PD) is a neurological disorder characterized by the progressive loss of midbrain dopamine (DA) neurons. Bone marrow mesenchymal stem cells (BMSCs) can differentiate into multiple cell types including neurons and glia. Transplantation of BMSCs is regarded as a potential approach for promoting neural regeneration. Glial cell line-derived neurotrophic factor (GDNF) can induce BMSC differentiation into neuron-like cells. This work evaluated the efficacy of nigral grafts of human BMSCs (hMSCs) and/or adenoviral (Ad) GDNF gene transfer in 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian rats.

AIM

To evaluate the efficacy of nigral grafts of hMSCs and/or Ad-GDNF gene transfer in 6-OHDA-lesioned hemiparkinsonian rats.

METHODS

We used immortalized hMSCs, which retain their potential for neuronal differentiation. hMSCs, preinduced hMSCs, or Ad-GDNF effectively enhanced neuronal connections in cultured neurons. In vivo, preinduced hMSCs and/or Ad-GDNF were injected into the substantia nigra (SN) after induction of a unilateral 6-OHDA lesion in the nigrostriatal pathway.

RESULTS

Hemiparkinsonian rats that received preinduced hMSC graft and/or Ad-GDNF showed significant recovery of apomorphine-induced rotational behavior and the number of nigral DA neurons. However, DA levels in the striatum were not restored by these therapeutic treatments. Grafted hMSCs might reconstitute a niche to support tissue repair rather than contribute to the generation of new neurons in the injured SN.

CONCLUSION

The results suggest that preinduced hMSC grafts exert a regenerative effect and may have the potential to improve clinical outcome.

Effect of the micro-immunotherapy medicine 2LPARK® on rat primary dopaminergic neurons after 6-OHDA injury: oxidative stress and survival evaluation in an in vitro model of Parkinson's disease

Background

Parkinson’s disease (PD) is a neurodegenerative disease characterized by motor impairments and resulting from progressive degenerative loss of midbrain dopaminergic (DAergic) neurons in the substantia nigra. Although the main cause of the loss of DAergic neurons is still unknown, various etiopathogenic mechanisms are distinguished, including release and accumulation of endogenous excitotoxic mediators along with the production of oxidative free radicals. Several neurotrophic and growth factors are known to increase DAergic neuronal survival and enhance antioxidant mechanisms. In this context, the micro-immunotherapy (MI) approach consists to regulate the immune system in order to protect DAergic neurons and control oxidative stress.

Purpose

The aim of the present study was to investigate the effect of the MI medicine (MIM), 2LPARK^® (Labo’Life), on oxidative stress and on the number of neurons positive for tyrosine hydroxylase (TH), in an in vitro model of PD.

Methods

Rat primary mesencephalic DAergic neurons cultures were pre-treated for 1 hr with the MIM (10 μM and 10 mM), placebo (10 μM and 10 mM) or brain-derived neurotrophic factor (BDNF; 3.3 μM) and then intoxicated with 6-hydroxydopamine (6-OHDA; 20 μM) for 48 hrs. After incubation, cells were incubated 30 mins at 37°C with CellROX green reagent and number of labeled cells were quantified. Then, cells were fixed and incubated with anti-TH antibody and the number of TH⁺ neurons was evaluated.

Results

We showed that, contrary to placebo, MIM was able to reduce oxidative stress and protect DAergic neurons from 6-OHDA-induced cell death.

Conclusion

Our results demonstrate the in vitro efficacy of MIM on two essential mechanisms of PD and propose the MI approach as a new ally in the regulation of neuroinflammation and in the treatment of this degenerative disease.

Neurotrophic factors hold promise for the future of Parkinson's disease treatment: is there a light at the end of the tunnel?

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is characterized by a spectrum of clinicopathologic signs and a complex etiology. PD results from the degeneration of dopaminergic (DAergic) neurons in the substantia nigra. Current therapies for PD are only able to alleviate symptoms without stopping disease progression. In addition, the available therapeutic strategies do not have long-lasting effects. Furthermore, these therapies cause different ranges of adverse side effects. There is great interest in neurotrophic factors (NTFs) due to their ability to promote the survival of different neural cells. These factors are divided into four families: neurotrophins, neurokines, the glial cell line-derived NTF family of ligands, and the newly recognized cerebral DA NTF/mesencephalic astrocyte-derived NTF family. The protective and therapeutic effects of these factors on DAergic neurons make them suitable for the prevention of progressive cell loss in PD. Based on the above premise, we focus on the protective effects of NTFs, especially CDNF and MANF, on nigrostriatal DAergic neurons in PD.

Alterations of DNA Methylation at GDNF Gene Promoter in the Ventral Tegmental Area of Adult Depression-Like Rats Induced by Maternal Deprivation

Objective: To study the expression and DNA methylation of the Glial cell line-derived neurotrophic factor (GDNF) gene in the development of depression-like behaviors in rats experiencing maternal deprivation stress in early life. Methods: Newborn SD rats were randomly assigned to a normal control group (NOR) or maternal deprivation group (MD). An open field test (OPT), sucrose preference test (SPT), and a forced swimming test (FST) were used to evaluate rats' behaviors. Protein, mRNA, and methylation levels were measured by ELISA/Western blot, real-time PCR, and BiSulfte Amplicon sequencing PCR, respectively. Results: MD rats had significantly shorter total distance and more fecal pellets in OPT, a lower sucrose preference rate in SPT, and a longer immobility time in FST than NOR rats. Compared with NOR rats, MD rats showed a significantly higher plasma corticosterone (CORT) level. The levels of plasma dopamine (DA) and the GDNF were significantly lower in the MD rats than in NOR rats. In the ventral tegmental area (VTA) tissues, MD rats had a significantly higher level of methylation at the GDNF gene promoter than NOR rats. The expression of the GDNF mRNA and protein were significantly lower in MD rats than in NOR rats. The total distance was significantly correlated with plasma DA and GDNF, the DNA methylation level at the GDNF promoter and the GDNF mRNA level in the VTA. Fecal pellets showed a significant correlation with plasma CORT. The sucrose preference rate was significantly correlated with plasma DA, the DNA methylation level at the GDNF promoter and the GDNF mRNA level in the VTA. Immobility time showed a significant correlation with the plasma DA, the plasma GDNF and the GDNF mRNA level in the VTA. Conclusion: up-regulation of DNA methylation at the GDNF gene promotor and the subsequent down-regulation of the GDNF gene expression in the VTA, may be involved in the development of depression-like behaviors in rats experiencing MD in early life.

The Non-Survival Effects of Glial Cell Line-Derived Neurotrophic Factor on Neural Cells

Glial cell line-derived neurotrophic factor (GDNF) was first characterized as a survival-promoting molecule for dopaminergic neurons (DANs). Afterwards, other cells were also discovered to respond to GDNF not only as a survival factor but also as a protein supporting other cellular functions, such as proliferation, differentiation, maturation, neurite outgrowth and other phenomena that have been less studied than survival and are now more extendedly described here in this review article. During development, GDNF favors the commitment of neural precursors towards dopaminergic, motor, enteric and adrenal neurons; in addition, it enhances the axonal growth of some of these neurons. GDNF also induces the acquisition of a dopaminergic phenotype by increasing the expression of Tyrosine Hydroxylase (TH), Nurr1 and other proteins that confer this identity and promote further dendritic and electrical maturation. In motor neurons (MNs), GDNF not only promotes proliferation and maturation but also participates in regenerating damaged axons and modulates the neuromuscular junction (NMJ) at both presynaptic and postsynaptic levels. Moreover, GDNF modulates the rate of neuroblastoma (NB) and glioblastoma cancer cell proliferation. Additionally, the presence or absence of GDNF has been correlated with conditions such as depression, pain, muscular soreness, etc. Although, the precise role of GDNF is unknown, it extends beyond a survival effect. The understanding of the complete range of properties of this trophic molecule will allow us to investigate its broad mechanisms of action to accelerate and/or improve therapies for the aforementioned pathological conditions.

CNS Gene Therapy and a Nexus of Complexity: Systems and Biology at a Crossroads

Gene therapy is a potentially promising new treatment for neurodegenerative disorders such as Alzheimer's disease (AD), which has been difficult to treat with conventional therapeutics. Viral vector-mediated somatic gene therapy is a rapidly developing methodology for providing never before achieved capability to deliver specific genes to the CNS in a highly localized and controlled manner. With the advent and refinements of this technology one focus is directed to which genes are the most appropriate to select for specific disease indications. Nerve growth factor (NGF), a potent survival factor for critical cell populations that degenerate in AD, has been chosen already for clinical gene therapy trials in human AD patients. Much knowledge about the pathophysiological underpinnings of AD is still lacking to make clear which patients may benefit from a gene therapy approach. Moreover, a detailed understanding of sustained NGF action in the normal and diseased CNS needs to be resolved before conclusions can be drawn regarding the utility of NGF gene therapy. Systematic efforts to acquire this new knowledge should compel clinically and biologically sophisticated efforts to advance gene therapy for neurodegenerative diseases.

Efficient Early and Sustained Transduction of Human Fetal Mesencephalon Using Adeno-Associated Virus Type 2 Vectors

The success of transplantation of human fetal mesencephalic tissue into the putamen of patients with Parkinson's disease (PD) is still limited by the poor survival of the graft. In animal models of fetal transplantation for PD, antiapoptotic agents, such as growth factors or caspase inhibitors, or agents counteracting oxidative stress enhance the survival and reinnervation potential of the graft. Genetic modification of the transplant could allow a local and continuous delivery of these factors at physiologically relevant doses. The major challenge remains the development of strategies to achieve both early and sustained gene delivery in the absence of vector-mediated toxicity. We recently reported that E14 rat fetal mesencephalon could be efficiently tranduced by adeno-associated virus type 2 (AAV2) vectors and that gene expression was maintained until at least 3 months after transplantation in the adult rat striatum. Here we report that an AAV2 vector can mediate the expression of the EGFP reporter gene under the control of a CMV promoter in organotypic cultures of freshly explanted solid fragments of human fetal mesencephalic tissue as early as 3 days to at least 6 weeks postinfection. These results suggest that AAV2 vectors could be used to genetically modify the human fetal tissue prior to transplantation to Parkinson's patients to promote graft survival and integration.

Neural stem cell therapy for neurodegenerative disorders: The role of neurotrophic support

Neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease currently affect tens of millions of people worldwide. Unfortunately, as the world's population ages, the incidence of many of these diseases will continue to rise and is expected to more than double by 2050. Despite significant research and a growing understanding of disease pathogenesis, only a handful of therapies are currently available and all of them provide only transient benefits. Thus, there is an urgent need to develop novel disease-modifying therapies to prevent the development or slow the progression of these debilitating disorders. A growing number of pre-clinical studies have suggested that transplantation of neural stem cells (NSCs) could offer a promising new therapeutic approach for neurodegeneration. While much of the initial excitement about this strategy focused on the use of NSCs to replace degenerating neurons, more recent studies have implicated NSC-mediated changes in neurotrophins as a major mechanism of therapeutic efficacy. In this mini-review we will discuss recent work that examines the ability of NSCs to provide trophic support to disease-effected neuronal populations and synapses in models of neurodegeneration. We will then also discuss some of key challenges that remain before NSC-based therapies for neurodegenerative diseases can be translated toward potential clinical testing.

Traumatic Brain Injury Activation of the Adult Subventricular Zone Neurogenic Niche

Traumatic brain injury (TBI) is common in both civilian and military life, placing a large burden on survivors and society. However, with the recognition of neural stem cells in adult mammals, including humans, came the possibility to harness these cells for repair of damaged brain, whereas previously this was thought to be impossible. In this review, we focus on the rodent adult subventricular zone (SVZ), an important neurogenic niche within the mature brain in which neural stem cells continue to reside. We review how the SVZ is perturbed following various animal TBI models with regards to cell proliferation, emigration, survival, and differentiation, and we review specific molecules involved in these processes. Together, this information suggests next steps in attempting to translate knowledge from TBI animal models into human therapies for TBI.

Human neural progenitors differentiate into astrocytes and protect motor neurons in aging rats

Age-associated health decline presents a significant challenge to healthcare, although there are few animal models that can be used to test potential treatments. Here, we show that there is a significant reduction in both spinal cord motor neurons and motor function over time in the aging rat. One explanation for this motor neuron loss could be reduced support from surrounding aging astrocytes. Indeed, we have previously shown using in vitro models that aging rat astrocytes are less supportive to rat motor neuron function and survival over time. Here, we test whether rejuvenating the astrocyte niche can improve the survival of motor neurons in an aging spinal cord. We transplanted fetal-derived human neural progenitor cells (hNPCs) into the aging rat spinal cord and found that the cells survive and differentiate into astrocytes with a much higher efficiency than when transplanted into younger animals, suggesting that the aging environment stimulates astrocyte maturation. Importantly, the engrafted astrocytes were able to protect against motor neuron loss associated with aging, although this did not result in an increase in motor function based on behavioral assays. We also transplanted hNPCs genetically modified to secrete glial cell line-derived neurotrophic factor (GDNF) into the aging rat spinal cord, as this combination of cell and protein delivery can protect motor neurons in animal models of ALS. During aging, GDNF-expressing hNPCs protected motor neurons, though to the same extent as hNPCs alone, and again had no effect on motor function. We conclude that hNPCs can survive well in the aging spinal cord, protect motor neurons and mature faster into astrocytes when compared to transplantation into the young spinal cord. While there was no functional improvement, there were no functional deficits either, further supporting a good safety profile of hNPC transplantation even into the older patient population.

Tackling Cell Transplantation Anoikis: An Injectable, Shape Memory Cryogel Microcarrier Platform Material for Stem Cell and Neuronal Cell Growth

Highly macroporous semisynthetic cryogel microcarriers can be synthesized for culturing stem cells and neuronal type cells. Growth factors loaded to heparin-containing microcarriers show near zero-order release kinetics and cell-loaded microcarriers can be injected through a fine gauge cannula without negative effect on the cells. These carriers can be applied for cell transplantation applications.

In Vivo Tracking of Human Neural Progenitor Cells in the Rat Brain Using Magnetic Resonance Imaging Is Not Enhanced by Ferritin Expression

Rapid growth in the field of stem cell research has generated a lot of interest in their therapeutic use, especially in the treatment of neurodegenerative diseases. Specifically, human neural progenitor cells (hNPCs), unique in their capability to differentiate into cells of the neural lineage, have been widely investigated due to their ability to survive, thrive, and migrate toward injured tissues. Still, one of the major roadblocks for clinical applicability arises from the inability to monitor these cells following transplantation. Molecular imaging techniques, such as magnetic resonance imaging (MRI), have been explored to assess hNPC transplant location, migration, and survival. Here we investigated whether inducing hNPCs to overexpress ferritin (hNPCs(Fer)), an iron storage protein, is sufficient to track these cells long term in the rat striatum using MRI. We found that increased hypointensity on MRI images could establish hNPC(Fer) location. Unexpectedly, however, wild-type hNPC transplants were detected in a similar manner, which is likely due to increased iron accumulation following transplantation-induced damage. Hence, we labeled hNPCs with superparamagnetic iron oxide (SPIO) nanoparticles to further increase iron content in an attempt to enhance cell contrast in MRI. SPIO-labeling of hNPCs (hNPCs-SPIO) achieved increased hypointensity, with significantly greater area of decreased T2* compared to hNPC(Fer) (p < 0.0001) and all other controls used. However, none of the techniques could be used to determine graft rejection in vivo, which is imperative for understanding cell behavior following transplantation. We conclude that in order for cell survival to be monitored in preclinical and clinical settings, another molecular imaging technique must be employed, including perhaps multimodal imaging, which would utilize MRI along with another imaging modality.

Glial cell line-derived neurotrophic factor-secreting human neural progenitors show long-term survival, maturation into astrocytes, and no tumor formation following transplantation into the spinal cord of immunocompromised rats

Human neural progenitor cells (hNPCs) derived from the fetal cortex can be expanded in vitro and genetically modified through lentiviral transduction to secrete growth factors shown to have a neurotrophic effect in animal models of neurological disease. hNPCs survive and mature following transplantation into the central nervous system of large and small animals including the rat model of amyotrophic lateral sclerosis. Here we report that hNPCs engineered to express glial cell line-derived neurotrophic factor (GDNF) survive long-term (7.5 months) following transplantation into the spinal cord of athymic nude rats and continue to secrete GDNF. Cell proliferation declined while the number of astrocytes increased, suggesting final maturation of the cells over time in vivo. Together these data show that GDNF-producing hNPCs may be useful as a source of cells for long-term delivery of both astrocytes and GDNF to the damaged central nervous system.

Isolamento e cultivo de neurônios e neuroesferas de córtex cerebral aviar

Métodos de cultivo celular são convenientes na realização de análises funcionais de alterações/interações protéicas das células neuronais, auxiliando a decifrar o interactoma de proteínas chaves na neurogênese de doenças do Sistema Nervoso Central. Por esse motivo, culturas de neurônios e neuroesferas isolados do córtex cerebral aviar representam um modelo acessível para o estudo de diversas doenças neurológicas, tal como a epilepsia. A espécie aviar apresenta peculiaridades em seu proteoma neuronal, visto a presença de uma expressão diferenciada de proteínas chaves no metabolismo energético cerebral, algumas destas (VDAC1 e VDAC2) desempenham papel importante na compreensão do mecanismo da epilepsia refratária. A metodologia estabelecida no presente estudo obteve cultivo de neuroeferas, onde as células cresceram tipicamente em aglomerados atingindo, dentro de 7 dias, o diâmetro ideal de 100-200 µm. A diferenciação celular das neuroesferas foi obtida após a aderência destas às placas tratadas com poli-D-lisina, evidenciada pela migração de fibras do interior da neuroesfera. Ao contrário das neuroesferas, os neurônios em cultivo extenderam seus neuritos após 11 dias de isolamento. Tal modelo in vitro pode ser utilizado com sucesso na identificação das variáveis neuroproteômicas, propiciando uma avaliação global das alterações dinâmicas e suas interações protéicas. Tal modelo pode ter aplicações em estudos dos efeitos de indutores da morte celular e bloqueadores de canais de membrana mitocondriais em proteínas chaves do metabolismo energético cerebral.

Regulated expression of lentivirus-mediated GDNF in human bone marrow-derived mesenchymal stem cells and its neuroprotection on dopaminergic cells in vitro

Gene regulation remains one of the major challenges for gene therapy in clinical trials. In the present study, we first generated a binary tetracycline-on (Tet-On) system based on two lentivirus vectors, one expressing both human glial cell line-derived neurotrophic factor (hGDNF) and humanized recombinant green fluorescent protein (hrGFP) genes under second-generation tetracycline response element (TRE), and the other expressing the advanced reverse tetracycline-controlled transactivator--rtTA2S-M2 under a human minimal cytomegalovirus immediate early (CMV-IE) promoter. This system allows simultaneous expression of hGDNF and hrGFP genes in the presence of doxycycline (Dox). Human bone marrow-derived mesenchymal stem cells (hMSCs) were transduced with the binary Tet-On lentivirus vectors and characterized in vitro in the presence (On) or absence (Off) of Dox. The expression of hGDNF and hrGFP transgenes in transduced hMSCs was tightly regulated as determined by flow cytometry (FCM), GDNF enzyme-linked immunosorbent assay (ELISA) and quantitative real time-polymerase chain reaction (qRT-PCR). There was a dose-dependent regulation for hrGFP transgene expression. The levels of hGDNF protein in culture medium were correlated with the mean fluorescence intensity (MFI) units of hrGFP. The levels of transgene background expression were very low in the absence of Dox. The treatment of the conditioned medium from cultures of transduced hMSCs in the presence of Dox protected SH-SY5Y cells against 6-hydroxydopamine (6-OHDA) toxicity as determined by cell viability using 3, [4,5-dimethylthiazol-2-yl]-diphenyltetrazolium bromide (MTT) assay. The treatment of the conditioned medium was also found to improve the survival of dopaminergic (DA) neurons of ventral mesencephalic (VM) tissue in serum-free culture conditions as assessed by cell body area, the number of neurites and dendrite branching points, and proportion of tyrosine hydroxylase (TH)-immunoreactive (IR) cells. Our inducible lentivirus-mediated hGDNF gene delivery system may provide useful tools for basic research on gene therapy for chronic neurological disorders such as Parkinson's disease (PD).

Transplantation of novel human GDF5-expressing CHO cells is neuroprotective in models of Parkinson's disease

Growth/differentiation factor 5 (GDF5) is a neurotrophic factor that promotes the survival of midbrain dopaminergic neurons in vitro and in vivo and as such is potentially useful in the treatment of Parkinson's disease (PD). This study shows that a continuous supply of GDF5, produced by transplanted GDF5-overexpressing CHO cells in vivo, has neuroprotective and neurorestorative effects on midbrain dopaminergic neurons following 6-hydroxydopamine (6-OHDA)-induced lesions of the adult rat nigrostriatal pathway. It also increases the survival and improves the function of transplanted embryonic dopaminergic neurons in the 6-OHDA-lesioned rat model of PD. This study provides the first proof-of-principle that sustained delivery of GDF5 in vivo may be useful in the treatment of PD.

Comparison of ectopic gene expression methods in rat neural stem cells

Neural stem cells (NSCs) have the ability to proliferate and differentiate into various types of cells that compose the nervous system. To study functions of genes in stem cell biology, genes or siRNAs need to be transfected. However, it is difficult to transfect ectopic genes into NSCs. Thus to identify the suitable method to achieve high transfection efficiency, we compared lipid transfection, electroporation, nucleofection and retroviral transduction. Among the methods that we tested, we found that nucleofection and retroviral transduction showed significantly increased transfection efficiency. In addition, with retroviral transduction of Ngn2 that is known to induce neurogenesis in various types of cells, we observed facilitated final cell division in rat NSCs. These data suggest that nucleofection and retroviral transduction provide high efficiency of gene delivery system to study functions of genes in rat NSCs.

Cografting of carotid body cells improves the long-term survival, fiber outgrowth and functional effects of grafted dopaminergic neurons

AIMS

A major limiting factor for cell therapy in Parkinson's disease is that the survival of grafted dopaminergic neurons is very poor, which may be improved by administration of GDNF, for which the carotid body is a good source.

MATERIALS & METHODS

Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic neuroblasts with or without cell aggregates from the rat carotid body. At 1, 2 and 3 months after grafting, the rats were tested in the cylinder and the rotometer and killed 4 months after grafting.

RESULTS

We observed that the survival of dopaminergic neurons and graft-derived dopaminergic innervation were higher in rats that received mixed grafts. Both grafted groups showed complete recovery in the amphetamine-induced rotation test. However, rats with cografts performed significantly better in the cylinder test.

CONCLUSION

Cografting of carotid body cells may constitute a useful strategy for cell therapy in Parkinson's disease.

Feline neural progenitor cells II: use of novel plasmid vector and hybrid promoter to drive expression of glial cell line-derived neurotrophic factor transgene

Sustained transgene expression is required for the success of cell transplant-based gene therapy. Most widely used are lentiviral-based vectors which integrate into the host genome and thereby maintain sustained transgene expression. This requires integration into the nuclear genome, and potential risks include activation of oncogenes and inactivation of tumor suppressor genes. Plasmids have been used; however lack of sustained expression presents an additional challenge. Here we used the pCAG-PyF101-eGFP plasmid to deliver the human GDNF gene to cat neural progenitor cells (cNPCs). This vector consists of a CAGG composite promoter linked to the polyoma virus mutant enhancer PyF101. Expression of an episomal eGFP reporter and GDNF transgene were stably maintained by the cells, even following induction of differentiation. These genetically modified cells appear suitable for use in allogeneic models of cell-based delivery of GDNF in the cat and may find veterinary applications should such strategies prove clinically beneficial.

Neuron-specific gene transfer through retrograde transport of lentiviral vector pseudotyped with a novel type of fusion envelope glycoprotein

The lentiviral vector system is used extensively in gene therapy trials for various neurological and neurodegenerative disorders. The vector system permits efficient and sustained gene expression in many cell types through integration of the transgene into the host cell genome. However, there is a significant issue concerning the therapeutic use of lentiviral vectors, that transgene insertion may lead to tumorigenesis by altering the expression of proto-oncogenes adjacent to the integration sites. One useful approach for improving safety is to restrict vector transduction to neuronal cells. We have reported the use of human immunodeficiency virus type 1 (HIV-1)-based vectors for efficient retrograde transport by pseudotyping with rabies virus glycoprotein (RV-G) or fusion glycoprotein B type, in which the cytoplasmic domain of RV-G was substituted with the counterpart of vesicular stomatitis virus glycoprotein (VSV-G). Here we developed a novel vector system for neuron-specific retrograde gene transfer (termed NeuRet) by pseudotyping the HIV-1 vector with fusion glycoprotein C type (FuG-C), in which a short C-terminal segment of the extracellular domain and the transmembrane/cytoplasmic domains of RV-G were replaced with the corresponding regions of VSV-G. FuG-C pseudotyping caused efficient gene transfer, mainly through retrograde transport, into neuronal cells in diverse brain regions, whereas the pseudotyping resulted in less efficiency for the transduction of glial and neural stem/progenitor cells. Our NeuRet vector system achieves efficient retrograde gene delivery for therapeutic trials and improves their safety by greatly reducing the risk of gene transduction of dividing cells in the brain.

Cell transplantation and gene therapy in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disorder affecting, in part, dopaminergic motor neurons of the ventral midbrain and their terminal projections that course to the striatum. Symptomatic strategies focused on dopamine replacement have proven effective at remediating some motor symptoms during the course of disease but ultimately fail to deliver long-term disease modification and lose effectiveness due to the emergence of side effects. Several strategies have been experimentally tested as alternatives for Parkinson's disease, including direct cell replacement and gene transfer through viral vectors. Cellular transplantation of dopamine-secreting cells was hypothesized as a substitute for pharmacotherapy to directly provide dopamine, whereas gene therapy has primarily focused on restoration of dopamine synthesis or neuroprotection and restoration of spared host dopaminergic circuitry through trophic factors as a means to enhance sustained controlled dopamine transmission. This seems now to have been verified in numerous studies in rodents and nonhuman primates, which have shown that grafts of fetal dopamine neurons or gene transfer through viral vector delivery can lead to improvements in biochemical and behavioral indices of dopamine deficiency. However, in clinical studies, the improvements in parkinsonism have been rather modest and variable and have been plagued by graft-induced dyskinesias. New developments in stem-cell transplantation and induced patient-derived cells have opened the doors for the advancement of cell-based therapeutics. In addition, viral-vector-derived therapies have been developed preclinically with excellent safety and efficacy profiles, showing promise in clinical trials thus far. Further progress and optimization of these therapies will be necessary to ensure safety and efficacy before widespread clinical use is deemed appropriate.

The transfection of multipotent neural precursor/stem cell transplant populations with magnetic nanoparticles

Multipotent neural precursor/stem cells (NPCs) are a major transplant population with key properties to promote repair in several neuropathological conditions. Magnetic nanoparticle (MNP)-based vector systems, in turn, offer a combination of key benefits for cell therapies including (i) safety (ii) delivery of therapeutic biomolecules (DNA/siRNA) enhanceable by 'magnetofection' approaches (iii) magnetic cell targeting of MNP-labelled cells to injury sites and (iv) non-invasive imaging of MNP-labelled transplant populations for cell tracking. However, the applications of the versatile MNP platform for NPC transplantation therapies have received limited attention so far. We have evaluated the potential of MNP vectors for gene transfer to NPCs using a neurosphere culture model system; we also assessed repeat transfection ("multifection") and repeat transfection plus applied magnetic field ("magneto-multifection") strategies [to enhance transfection efficiency]. We show for the first time that MNPs can safely mediate single/combinatorial gene delivery to NPCs. Multifection approaches significantly enhanced transfection with negligible toxicity; no adverse effects were observed on stem cell proliferation/differentiation. "Multifected" NPCs survived and differentiated in 3D neural tissue arrays post-transplantation. Our findings demonstrate that MNPs offer a simple and robust alternative to the viral vector systems currently used widely to transfect neural stem cells in neurobiology/neural transplantation research.

Real time imaging of human progenitor neurogenesis

Human neural progenitors are increasingly being employed in drug screens and emerging cell therapies targeted towards neurological disorders where neurogenesis is thought to play a key role including developmental disorders, Alzheimer’s disease, and depression. Key to the success of these applications is understanding the mechanisms by which neurons arise. Our understanding of development can provide some guidance but since little is known about the specifics of human neural development and the requirement that cultures be expanded in vitro prior to use, it is unclear whether neural progenitors obey the same developmental mechanisms that exist in vivo. In previous studies we have shown that progenitors derived from fetal cortex can be cultured for many weeks in vitro as undifferentiated neurospheres and then induced to undergo neurogenesis by removing mitogens and exposing them to supportive substrates. Here we use live time lapse imaging and immunocytochemical analysis to show that neural progenitors use developmental mechanisms to generate neurons. Cells with morphologies and marker profiles consistent with radial glia and recently described outer radial glia divide asymmetrically and symmetrically to generate multipolar intermediate progenitors, a portion of which express ASCL1. These multipolar intermediate progenitors subsequently divide symmetrically to produce CTIP2⁺ neurons. This 3-cell neurogenic scheme echoes observations in rodents in vivo and in human fetal slice cultures in vitro, providing evidence that hNPCs represent a renewable and robust in vitro assay system to explore mechanisms of human neurogenesis without the continual need for fresh primary human fetal tissue. Knowledge provided by this and future explorations of human neural progenitor neurogenesis will help maximize the safety and efficacy of new stem cell therapies by providing an understanding of how to generate physiologically-relevant cell types that maintain their identities when placed in diagnostic or transplantation environments.

Gene therapy in Parkinson's disease: rationale and current status

Parkinson's disease is the second most common age-related neurodegenerative disorder, typified by the progressive loss of substantia nigra pars compacta dopamine neurons and the consequent decrease in the neurotransmitter dopamine. Patients exhibit a range of clinical symptoms, with the most common affecting motor function and including resting tremor, rigidity, akinesia, bradykinesia and postural instability. Current pharmacological interventions are palliative and largely aimed at increasing dopamine levels through increased production and/or inhibition of metabolism of this key neurotransmitter. The gold standard for treatment of both familial and sporadic Parkinson's disease is the peripheral administration of the dopamine precursor, levodopa. However, many patients gradually develop levodopa-induced dyskinesias and motor fluctuations. In addition, dopamine enhancement therapies are most useful when a portion of the nigrostriatal pathway is intact. Consequently, as the number of substantia nigra dopamine neurons and striatal projections decrease, these treatments become less efficacious. Current translational research is focused on the development of novel disease-modifying therapies, including those utilizing gene therapeutic approaches. Herein we present an overview of current gene therapy clinical trials for Parkinson's disease. Employing either recombinant adeno-associated virus type 2 (rAAV2) or lentivirus vectors, these clinical trials are focused on three overarching approaches: augmentation of dopamine levels via increased neurotransmitter production; modulation of the neuronal phenotype; and neuroprotection. The first two therapies discussed in this article focus on increasing dopamine production via direct delivery of genes involved in neurotransmitter synthesis (amino acid decarboxylase, tyrosine hydroxylase and GTP [guanosine triphosphate] cyclohydrolase 1). In an attempt to bypass the degenerating nigrostriatal pathway, a third clinical trial utilizes rAAV2 to deliver glutamic acid decarboxylase to the subthalamic nucleus, converting a subset of excitatory neurons to GABA-producing cells. In contrast, the final clinical trial is aimed at protecting the degenerating nigrostriatum by striatal delivery of rAAV2 harbouring the neuroprotective gene, neurturin. Based on preclinical studies, this gene therapeutic approach is posited to slow disease progression by enhancing neuronal survival. In addition, we discuss the outcome of each clinical trial and discuss the potential rationale for the marginal yet incremental clinical advancements that have thus far been realized for Parkinson's disease gene therapy.

Neural progenitor cells attenuate inflammatory reactivity and neuronal loss in an animal model of inflamed AD brain

Background

Transplantation of neural progenitor cells (NPC) constitutes a putative therapeutic maneuver for use in treatment of neurodegenerative diseases. At present, effects of NPC transplantation in Alzheimer's disease (AD) brain are largely unknown and a primary objective of this work was to demonstrate possible efficacy of NPC administration in an animal model of AD. The benefits of transplantation could involve a spectrum of effects including replacement of endogenous neurons or by conferring neuroprotection with enhancement of neurotrophic factors or diminishing levels of neurotoxic agents. Since chronic inflammation is a characteristic property of AD brain, we considered that transplantation of NPC could have particular utility in inhibiting ongoing inflammatory reactivity. We have tested intrahippocampal transplantation of NPC for efficacy in attenuating inflammatory responses and for neuroprotection in beta-amyloid (Aβ_1-42) peptide-injected rat hippocampus.

Methods

Spheres of neural progenitor cells were grown from dissociated telencephalon tissue of rat embryos. NPC were infected with lentiviral vector green fluorescent protein (GFP) with subsequent cell transplantation into rat hippocampus previously injected (3 d prior) with Aβ_1-42 peptide or PBS control. Immunohistochemical analysis was carried out (7 d post-NPC transplantation, 10 d post-peptide/PBS injection) for GFP, microgliosis (Iba-1 marker), astrogliosis (GFAP marker), neuron viability (MAP-2 marker) and levels of the proinflammatory cytokine, TNF-α.

Results

Successful infection of cultured NPC with lentiviral vector green fluorescent protein (GFP) was demonstrated prior to cell transplantation into rat hippocampus. In vivo, immunohistochemical staining showed migration of GFP-positive cells, in a region of dentate gyrus between Aβ_1-42/PBS injection site and NPC transplantation site, was increased ×2.8-fold with Aβ_1-42 compared to PBS injection. Double immunostaining in peptide-injected brain indicated GFP association with nestin and GFAP, but not MAP-2. Cell-specific immunostaining showed marked increases in microgliosis and astrogliosis in Aβ_1-42-injected brain (respective increases of ×4.3- and ×4.6-fold compared with PBS injection). NPC transplantation significantly reduced microgliosis (by 38%) but not astrogliosis in peptide-injected hippocampus. The proinflammatory cytokine TNF-α was elevated by 6.7-fold (peptide vs PBS injection) with NPC administration attenuating levels of TNF-α (by 40%). Peptide-injected brain demonstrated neuronal loss (MAP-2 staining reduced by 45% vs PBS injection) with NPC transplantation effective in conferring neuroprotection (26% recovery of neurons).

Conclusions

These findings indicate efficacy for NPC transplantation in an animal model of AD with effects consistent with cellular actions to attenuate inflammatory reactivity induced by intrahippocampal peptide injection.

Single-cell hydrogel encapsulation for enhanced survival of human marrow stromal cells

Inadequate extracellular matrix cues and subsequent apoptotic cell death are among crucial factors currently limiting cell viability and organ retention in cell-based therapeutic strategies for vascular regeneration. Here we describe the use of a single-cell hydrogel capsule to provide enhanced cell survival of adherent cells in transient suspension culture. Human marrow stromal cells (hMSCs) were singularly encapsulated in agarose capsules containing the immobilized matrix molecules, fibronectin and fibrinogen to ameliorate cell-matrix survival signals. MSCs in the enriched capsules demonstrated increased viability, greater metabolic activity and enhanced cell-cytoskeletal patterning. Increased cell viability resulted from the re-induction of cell-matrix interactions likely via integrin clustering and subsequent activation of the extracellular signal regulated MAPK (ERK)/mitogen activated protein kinase (MAPK) signaling cascade. Proof of principle in-vivo studies, investigating autologous MSC delivery into Fisher 344 rat hindlimb, depicted a significant increase in the number of engrafted cells using the single-cell encapsulation system. Incorporation of immobilized adhesion molecules compensates, at least in part, for the missing cell-matrix cues, thereby attenuating the initial anoikis stimuli and providing protection from subsequent apoptosis. Thus, this single-cell encapsulation strategy may markedly enhance therapeutic cell survival in targeted tissues.

Chromosome 7 and 19 trisomy in cultured human neural progenitor cells

Background

Stem cell expansion and differentiation is the foundation of emerging cell therapy technologies. The potential applications of human neural progenitor cells (hNPCs) are wide ranging, but a normal cytogenetic profile is important to avoid the risk of tumor formation in clinical trials. FDA approved clinical trials are being planned and conducted for hNPC transplantation into the brain or spinal cord for various neurodegenerative disorders. Although human embryonic stem cells (hESCs) are known to show recurrent chromosomal abnormalities involving 12 and 17, no studies have revealed chromosomal abnormalities in cultured hNPCs. Therefore, we investigated frequently occurring chromosomal abnormalities in 21 independent fetal-derived hNPC lines and the possible mechanisms triggering such aberrations.

Methods and Findings

While most hNPC lines were karyotypically normal, G-band karyotyping and fluorescent in situ hybridization (FISH) analyses revealed the emergence of trisomy 7 (hNPC⁺⁷) and trisomy 19 (hNPC⁺¹⁹), in 24% and 5% of the lines, respectively. Once detected, subsequent passaging revealed emerging dominance of trisomy hNPCs. DNA microarray and immunoblotting analyses demonstrate epidermal growth factor receptor (EGFR) overexpression in hNPC⁺⁷ and hNPC⁺¹⁹ cells. We observed greater levels of telomerase (hTERT), increased proliferation (Ki67), survival (TUNEL), and neurogenesis (β_III-tubulin) in hNPC⁺⁷ and hNPC⁺¹⁹, using respective immunocytochemical markers. However, the trisomy lines underwent replicative senescence after 50–60 population doublings and never showed neoplastic changes. Although hNPC⁺⁷ and hNPC⁺¹⁹ survived better after xenotransplantation into the rat striatum, they did not form malignant tumors. Finally, EGF deprivation triggered a selection of trisomy 7 cells in a diploid hNPC line.

Conclusions

We report that hNPCs are susceptible to accumulation of chromosome 7 and 19 trisomy in long-term cell culture. These results suggest that micro-environmental cues are powerful factors in the selection of specific hNPC aneuploidies, with trisomy of chromosome 7 being the most common. Given that a number of stem cell based clinical trials are being conducted or planned in USA and a recent report in PLoS Medicine showing the dangers of grafting an inordinate number of cells, these data substantiate the need for careful cytogenetic evaluation of hNPCs (fetal or hESC-derived) before their use in clinical or basic science applications.

Long-term multilayer adherent network (MAN) expansion, maintenance, and characterization, chemical and genetic manipulation, and transplantation of human fetal forebrain neural stem cells

Human neural stem/precursor cells (hNSC/hNPC) have been targeted for application in a variety of research models and as prospective candidates for cell-based therapeutic modalities in central nervous system (CNS) disorders. To this end, the successful derivation, expansion, and sustained maintenance of undifferentiated hNSC/hNPC in vitro, as artificial expandable neurogenic micro-niches, promises a diversity of applications as well as future potential for a variety of experimental paradigms modeling early human neurogenesis, neuronal migration, and neurogenetic disorders, and could also serve as a platform for small-molecule drug screening in the CNS. Furthermore, hNPC transplants provide an alternative substrate for cellular regeneration and restoration of damaged tissue in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Human somatic neural stem/progenitor cells (NSC/NPC) have been derived from a variety of cadaveric sources and proven engraftable in a cytoarchitecturally appropriate manner into the developing and adult rodent and monkey brain while maintaining both functional and migratory capabilities in pathological models of disease. In the following unit, we describe a new procedure that we have successfully employed to maintain operationally defined human somatic NSC/NPC from developing fetal, pre-term post-natal, and adult cadaveric forebrain. Specifically, we outline the detailed methodology for in vitro expansion, long-term maintenance, manipulation, and transplantation of these multipotent precursors.

Neurotrophic factors in neurodegenerative disorders : potential for therapy

Finding an effective therapy to treat chronic neurodegenerative disorders still represents an unmet and elusive goal, mainly because so many pathogenic variables come into play in these diseases. Recent emphasis has been placed on the role of neurotrophic factors in the aetiology of such disorders because of their role in the survival of different cell phenotypes under various adverse conditions, including neurodegeneration.This review summarizes the current status and the efforts to treat neurodegenerative disorders by the exogenous administration of neurotrophic factors in an attempt to replenish trophic supply, the paucity of which may contribute to the development of the illness. Although promising results have been seen in animal models, this approach still meets disparate and often insurmountable problems in clinical settings, presumably related to the unique nature of the human being.

Future of cell and gene therapies for Parkinson's disease

The experimental field of restorative neurology continues to advance with implantation of cells or transfer of genes to treat patients with neurological disease. Both strategies have generated a consensus that demonstrates their capacity for structural and molecular brain modification in the adult brain. However, both approaches have yet to successfully address the complexities to make such novel therapeutic modalities work in the clinic. Prior experimental cell transplantation to patients with PD utilized dissected pieces of fetal midbrain tissue, containing mixtures of cells and neuronal types, as donor cells. Stem cell and progenitor cell biology provide new opportunities for selection and development of large batches of specific therapeutic cells. This may allow for cell composition analysis and dosing to optimize the benefit to an individual patient. The biotechnology used for cell and gene therapy for treatment of neurological disease may eventually be as advanced as today's pharmaceutical drug-related design processes. Current gene therapy phase 1 safety trials for PD include the delivery of a growth factor (neurturin via the glial cell line-derived neurotrophic factor receptor) and a transmitter enzyme (glutamic acid decarboxylase and aromatic acid decarboxylase). Many new insights from cell biological and molecular studies provide opportunities to selectively express or suppress factors relevant to neuroprotection and improved function of neurons involved in PD. Future gene and cell therapies are likely to coexist with classic pharmacological therapies because their use can be tailored to individual patients' underlying disease process and need for neuroprotective or restorative interventions.

alpha-Synuclein: a therapeutic target for Parkinson's disease?

Parkinson's disease is a progressive age-related neurodegenerative disease with invariant loss of substantia nigra dopamine neurons and striatal projections. This disorder is well known for the associated motoric symptoms including resting tremor and the inability to initiate movement. However, it is now apparent that Parkinson's disease is a multisystem disorder with patients exhibiting symptoms derived from peripheral nervous system and extra-nigral dysfunctions in addition to the prototypical nigrostriatal damage. Although the etiology for sporadic Parkinson's disease is unknown, information gleaned from both familial forms of the disease and animal models places misfolded alpha-synuclein at the forefront. The disease is currently without a cure and most therapies target the motoric symptoms relying on increasing dopamine tone. In this review, the role of alpha-synuclein in disease pathogenesis and as a potential therapeutic target focusing on toxic conformers of this protein is considered. The addition of protofibrillar/oligomer-directed neurotherapeutics to the existing armamentarium may extend the symptom-free stage of Parkinson's disease as well as alleviate pathogenesis.

Long-term transgene expression in mouse neural progenitor cells modified with phiC31 integrase

Stem cells can potentially be utilized in combined gene/cell therapies for neural diseases. We examined the ability of the non-viral phiC31 integrase system to promote stable transgene expression in mouse neural progenitor cells (mNPCs). phiC31 integrase catalyzes the sequence-specific integration of attB-containing plasmids into pseudo attP sites in mammalian genomes, to produce long-term transgene expression. We achieved gene transfer by co-nucleofection of a plasmid carrying the luciferase marker gene and an attB site and a plasmid expressing integrase in mNPCs that had been generated in a neurosphere preparation. Luciferase expression was quantified in live cells for 8 weeks, revealing persistence of gene expression. Sequence-specific integration at a preferred pseudo attP site in the mouse genome was detected by using PCR. Furthermore, sustained transgene expression was demonstrated in genetically modified NPCs that were cultured in conditions that promoted either growth or differentiation into neurons and astrocytes. Our results demonstrate that the phiC31 integrase system produces stable transgene expression in adult mNPCs and their progeny and may be useful in strategies for combating neurodegenerative disorders.

Emerging restorative treatments for Parkinson's disease

Several exciting approaches for restorative therapy in Parkinson's disease have emerged over the past two decades. This review initially describes experimental and clinical data regarding growth factor administration. We focus on glial cell line-derived neurotrophic factor (GDNF), particularly its role in neuroprotection and in regeneration in Parkinson's disease. Thereafter, we discuss the challenges currently facing cell transplantation in Parkinson's disease and briefly consider the possibility to continue testing intrastriatal transplantation of fetal dopaminergic progenitors clinically. We also give a more detailed overview of the developmental biology of dopaminergic neurons and the potential of certain stem cells, i.e. neural and embryonic stem cells, to differentiate into dopaminergic neurons. Finally, we discuss adult neurogenesis as a potential tool for restoring lost dopamine neurons in patients suffering from Parkinson's disease.

GDNF-Secreting Human Neural Progenitor Cells Increase Tyrosine Hydroxylase and VMAT2 Expression in MPTP-Treated Cynomolgus Monkeys

Human neural progenitor cells (hNPCs) have been proposed as a potential source of cells for ex vivo gene therapy. In this pilot study, three 5-year-old female cynomolgus monkeys received a single intracarotid infusion of MPTP, followed 1 week later by MRI-guided stereotaxic intrastriatal and intranigral injections of male hNPCs transgenic for GDNF. Immunosupression with oral cyclosporine (30–40 mg/kg) began 48 h before hNPC transplants and continued throughout the study. We monitored the animals using a clinical rating scale (CRS). Three months postsurgery, we euthanized the animals by transcardiac perfusion, then retrieved and processed their brains for morphological analysis. Our findings include the following. 1) hNPCs survived and produced GDNF in all animals 3 months postsurgery. 2) hNPCs remained in the areas of injection as observed by GDNF immunostaining and in situ hybridization for the human Y chromosome. 3) A “halo” of GDNF expression was observed diffusing from the center of the graft out into the surrounding area. 4) We observed increased TH- and VMAT2-positive fibers in areas of GDNF delivery in two of the three animals. The two animals with TH- and VMAT2-positive fibers also showed reductions in their CRS scores. 5) Some GFAP-positive perivascular cuffing was found in transplanted areas. 6) General blood chemistry and necropsies did not reveal any abnormalities. Therefore, we conclude that hNPCs releasing GDNF may be a possible alternative for intracerebral trophic factor delivery in Parkinson's disease.

The neurosphere assay, a method under scrutiny

OBJECTIVES

The aim of this review is to provide an overview of the fundamental features of the neurosphere assay (NSA), which was initially described in 1992, and has since been used not only to detect the presence of stem cells in embryonic and adult mammalian neural tissues, but also to study their characteristics in vitro. Implicit in this review is a detailed examination of the limitations of the NSA, and how this assay is most accurately and appropriately used. Finally we will point out criteria that should be challenged to design alternative ways to overcome the limits of this assay.

METHODS

NSA is used to isolate putative neural stem cells (NSCs) from the central nervous system (CNS) and to demonstrate the critical stem cell attributes of proliferation, extensive self-renewal and the ability to give rise to a large number of differentiated and functional progeny. Nevertheless, the capability of neural progenitor cells to form neurospheres precludes its utilisation to accurately quantify bona fide stem cell frequency based simply on neurosphere numbers. New culture conditions are needed to be able to distinguish the activity of progenitor cells from stem cells.

CONCLUSION

A commonly used, and arguably misused, methodology, the NSA has provided a wealth of information on precursor activity of cells derived from the embryonic through to the aged CNS. Importantly, the NSA has contributed to the demise of the 'no new neurogenesis' dogma, and the beginning of a new era of CNS regenerative medicine. Nevertheless, the interpretations arising from the utilisation of the NSA need to take into consideration its limits, so as not to be used beyond its specificity and sensitivity.

Surgical management of Parkinson's disease: update and review

SUMMARY

Although medical therapy is still the mainstay of treatment for Parkinson's disease, the development of surgical precision and decreased morbidity have made stereotatic lesioning and deep brain stimulation more popular. Neurosurgical ablations include pallidotomy, thalamotomy, and, more recently, subthalamotomy. Because of concern over the high risk of side-effects resulting from bilateral ablative procedure, alternative approaches have been explored.With improved deep brain stimulation (DBS) technology, DBS has been successfully applied in the internal globus pallidus, ventral intermediate nucleus and subthalamic nucleus for Parkinson's disease. In addition, recent surgical approaches including biological neurorestorative technologies - surgical therapies with transplantation, gene therapy, and growth factor are all being discussed in this review. Although a great deal of work remains to be done for researchers, advances in surgical therapies for the treatment of Parkinson's disease are moving forward at an unprecedented pace, and, not surprisingly, would give PD patients more choices and hope.

Induction of A9 dopaminergic neurons from neural stem cells improves motor function in an animal model of Parkinson's disease

Neural stem cells (NSCs) are widely endorsed as a cell source for replacement strategies in neurodegenerative disease. However, their usefulness is currently limited by the inability to induce specific neurotransmitter phenotypes in these cells. In order to direct dopaminergic neuronal fate, we overexpressed Pitx3 in NSCs that were then exposed to E11 developing ventral mesencephalon (VM) in explant culture. This resulted in a significant potentiation of dopaminergic differentiation of the cells. When transplanted into the 6-hydroxydopamine lesioned Parkinsonian rats, these cografts of VM and Pitx3 overexpressing NSCs resulted in a significant restitution of motor function. In addition, there were greater numbers of Girk2 positive A9 neurons in the periphery of the transplants that were NSC derived. This demonstrates that given the correct signals, NSCs can be induced to become dopaminergic neurons that can differentiate into the correct nigrastriatal phenotype required for the treatment of Parkinson's disease.

Comparison of the therapeutic potential of adult and embryonic neural precursor cells in a rat model of Parkinson disease

Object

The therapeutic effects of adult and embryonic neural precursor cells (NPCs) were evaluated and their therapeutic potential compared in a rat model of Parkinson disease.

Methods

Adult NPCs were obtained from the subventricular zone and embryonic NPCs were taken from the ganglionic eminence of 14-day-old embryos. Each NPC type was cultured with epidermal growth factor. The in vitro neuronal differentiation rate of adult NPCs was approximately equivalent to that of embryonic NPCs after two passages. Next, the NPCs were transfected with either green fluorescent protein or glial cell line–derived neurotrophic factor (GDNF) by adenoviral infection and transplanted into the striata in a rat model of Parkinson disease (PD) induced by unilateral intrastriatal injection of 6-hydroxydopamine. An amphetamine-induced rotation test was used to evaluate rat behavioral improvement, and immunohistochemical analysis was performed to compare grafted cell survival, differentiation, and host tissue changes.

Results

The rats with GDNF-transfected NPCs had significantly fewer amphetamine-induced rotations and less histological damage. Except for the proportion of surviving grafted cells, there were no significant differences between adult and embryonic NPCs.

Conclusions

Adult and embryonic NPCs have a comparable therapeutic potential in a rat model of PD.

Adult neural stem and progenitor cells modified to secrete GDNF can protect, migrate and integrate after intracerebral transplantation in rats with transient forebrain ischemia

Adult neural stem and progenitor cells (NSPCs) are important autologous transplantation tools in regenerative medicine, as they can secrete factors that protect the ischemic brain. We investigated whether adult NSPCs genetically modified to secrete more glial cell line-derived neurotrophic factor (GDNF) could protect against transient ischemia in rats. NSPCs were harvested from the subventricular zone of adult Wistar rats and cultured for 3 weeks in the presence of epidermal growth factor. The NSPCs were treated with fibre-mutant Arg-Gly-Asp adenovirus containing the GDNF gene (NSPC-GDNF) or enhanced green fluorescent protein (EGFP) gene (NSPC-EGFP; control group). In one experiment, cultured cells were transplanted into the right ischemic boundary zone of Wistar rat brains. One week later, animals underwent 90 min of intraluminal right middle cerebral artery occlusion followed by magnetic resonance imaging and behavioural tests. The NSPC-GDNF group had higher behavioural scores and lesser infarct volume than did controls at 1, 7 and 28 days postocclusion. In the second experiment, we transplanted NSPCs 3 h after ischemic insult. Compared to controls, rats receiving NSPC-GDNF had decreased infarct volume and better behavioural assessments at 7 days post-transplant. Animals were killed on day 7 and brains were collected for GDNF ELISA and morphological assessment. Compared to controls, more GDNF was secreted, more NSPC-GDNF cells migrated toward the ischemic core and more NSPC-GDNF cells expressed immature neuronal marker. Moreover, the NSPC-GDNF group showed more effective inhibition of microglial invasion and apoptosis. These findings suggest that NSPC-GDNF may be useful in treatment of cerebral ischemia.

Neural tissue-spheres: A microexplant culture method for propagation of precursor cells from the rat forebrain subventricular zone

By combining new and established protocols we have developed a procedure for isolation and propagation of neural precursor cells from the forebrain subventricular zone (SVZ) of newborn rats. Small tissue blocks of the SVZ were dissected and propagated en bloc as free-floating neural tissue-spheres (NTS) in EGF and FGF2 containing medium. The spheres were cut into quarters when passaged every 10-15th day, avoiding mechanical or enzymatic dissociation in order to minimize cellular trauma and preserve intercellular contacts. For analysis of regional differences within the forebrain SVZ, NTS were derived from three rostro-caudal levels of the lateral ventricles (anterior, intermediate and posterior) and propagated separately. Explants from all three levels produced proliferating NTS, but "anterior" NTS in general grew to smaller sizes than "intermediate" and "posterior" NTS. Posterior NTS moreover maintained their neurogenic potential throughout 77 days of propagation, while the ability of anterior NTS to generate neurons severely declined from day 40. The present procedure describes isolation and long-term expansion of forebrain SVZ tissue with potential preservation of the endogenous cellular content, thus allowing experimental studies of neural precursor cells and their niche.

Pharmacologically active microcarriers releasing glial cell line – derived neurotrophic factor: Survival and differentiation of embryonic dopaminergic neurons after grafting in hemiparkinsonian rats

To improve the outcome of foetal dopaminergic cell transplantation for the treatment of Parkinson's disease, pharmacologically active microcarriers (PAM) were developed. PAM are able to convey cells on their surface and release a growth factor to improve cell survival, differentiation and integration after brain implantation. Lysozyme-releasing PAM were first produced and characterized. They served as a model system for the development of glial cell line-derived neurotrophic factor (GDNF)-releasing PAM conveying foetal ventral mesencephalic (FVM) cells. The effects of the intrastriatal implantation of this system were studied in hemiparkinsonian rats during a 6-week period. This study reports on the degradation of coated and non-coated PAM and the release of lysozyme and of biologically active GDNF for 42 days. Unloaded and GDNF-loaded PAM conveying FVM cells allowed a high improvement of the grafted cell survival and of fibre outgrowth, when compared to the cells transplanted alone. The animals receiving the PAM showed an earlier improvement in amphetamine-induced rotational behaviour compared to animals receiving FVM cells only; behaviour that appears to be more regular and stable with the GDNF-releasing PAM. The use of PAM to convey foetal cells is thus an efficient strategy for cell therapy in neurodegenerative diseases, as it allows improvement of cell survival and fibre outgrowth inducing a rapid recovery of behaviour using only low amounts of cells.