Neuroprotective and reparative effects of carotid body grafts in a chronic MPTP model of Parkinson's disease

Extracellular matrix protein anosmin-1 overexpression alters dopaminergic phenotype in the CNS and the PNS with no pathogenic consequences in a MPTP model of Parkinson's disease

The development and survival of dopaminergic neurons are influenced by the fibroblast growth factor (FGF) pathway. Anosmin-1 (A1) is an extracellular matrix protein that acts as a major regulator of this signaling pathway, controlling FGF diffusion, and receptor interaction and shuttling. In particular, previous work showed that A1 overexpression results in more dopaminergic neurons in the olfactory bulb. Prompted by those intriguing results, in this study, we investigated the effects of A1 overexpression on different populations of catecholaminergic neurons in the central (CNS) and the peripheral nervous systems (PNS). We found that A1 overexpression increases the number of dopaminergic substantia nigra pars compacta (SNpc) neurons and alters the striosome/matrix organization of the striatum. Interestingly, these numerical and morphological changes in the nigrostriatal pathway of A1-mice did not confer an altered susceptibility to experimental MPTP-parkinsonism with respect to wild-type controls. Moreover, the study of the effects of A1 overexpression was extended to different dopaminergic tissues associated with the PNS, detecting a significant reduction in the number of dopaminergic chemosensitive carotid body glomus cells in A1-mice. Overall, our work shows that A1 regulates the development and survival of dopaminergic neurons in different nuclei of the mammalian nervous system.

Protection and Repair of the Nigrostriatal Pathway with Stem-Cell-Derived Carotid Body Glomus Cell Transplants in Chronic MPTP Parkinsonian Model

Antiparkinsonian carotid body (CB) cell therapy has been proven to be effective in rodent and nonhuman primate models of Parkinson’s disease (PD), exerting trophic protection and restoration of the dopaminergic nigrostriatal pathway. These neurotrophic actions are mediated through the release of high levels of glial-cell-line-derived neurotrophic factor (GDNF) by the CB transplant. Pilot clinical trials have also shown that CB autotransplantation can improve motor symptoms in PD patients, although its effectiveness is affected by the scarcity of the grafted tissue. Here, we analyzed the antiparkinsonian efficacy of in vitro-expanded CB dopaminergic glomus cells. Intrastriatal xenografts of rat CB neurospheres were shown to protect nigral neurons from degeneration in a chronic MPTP mouse PD model. In addition, grafts performed at the end of the neurotoxic treatment resulted in the repair of striatal dopaminergic terminals through axonal sprouting. Interestingly, both neuroprotective and reparative effects induced by in vitro-expanded CB cells were similar to those previously reported by the use of CB transplants. This action could be explained because stem-cell-derived CB neurospheres produce similar amounts of GDNF compared to native CB tissue. This study provides the first evidence that in vitro-expanded CB cells could be a clinical option for cell therapy in PD.

Aquaporin-4 Expression Switches from White to Gray Matter Regions during Postnatal Development of the Central Nervous System

Aquaporin-4 (AQP4) is the most abundant water channel in the central nervous system and plays a fundamental role in maintaining water homeostasis there. In adult mice, AQP4 is located mainly in ependymal cells, in the endfeet of perivascular astrocytes, and in the glia limitans. Meanwhile, its expression, location, and function throughout postnatal development remain largely unknown. Here, the expression of AQP4 mRNA was studied by in situ hybridization and RT-qPCR, and the localization and amount of protein was studied by immunofluorescence and western blotting, both in the brain and spinal cord. For this, wild-type mice of the C57BL/6 line, aged 1, 3, 7, 11, 20, and 60 days, and 18 months were used. The results showed a change in both the expression and location of AQP4 in postnatal development compared to those during adult life. In the early stages of postnatal development it appears in highly myelinated areas, such as the corpus callosum or cerebellum, and as the animal grows, it disappears from these areas, passing through the cortical regions of the forebrain and concentrating around the blood vessels. These findings suggest an unprecedented possible role for AQP4 in the early cell differentiation process, during the first days of life in the newborn animal, which will lead to myelination.

Carotid Body and Cell Therapy

During the past decade, the carotid body (CB) has been considered an innovative therapeutic target for the treatment of certain cardiorespiratory and metabolic diseases most of which are sympathetically mediated. It has recently been revealed that CB stem cells provide new target sites for the development of promising cell-based therapies. Specifically, generation of CB progenitors in vitro which can differentiate into functionally active glomus cells may be a useful procedure to produce the cell mass required for replacement cell therapy. Due to their dopaminergic nature, adult glomus cells can be used for an intrastriatal grafting in neurodegenerative brain disorders including Parkinson's disease. The beneficial effect of throphic factors such as glial cell-derived neurotrophic factor synergistically released by the transplanted cells then enables the transplant to survive. Likewise, intracerebral administration of CB cell aggregates or dispersed cells has been tested for the treatment of an experimental model of stroke. The systematic clinical applicability of CB autotransplants following glomectomy in humans is under investigation. In such autotransplantation studies, cell aggregates from unilaterally resected CB might be used as autografts. In addition, stem cells could offer an opportunity for tissue expansion and might settle the issue of small number of glomus cells available for transplantation.

Insulin-like growth factor II prevents oxidative and neuronal damage in cellular and mice models of Parkinson's disease

Oxidative distress and mitochondrial dysfunction, are key factors involved in the pathophysiology of Parkinson's disease (PD). The pleiotropic hormone insulin-like growth factor II (IGF-II) has shown neuroprotective and antioxidant effects in some neurodegenerative diseases. In this work, we demonstrate the protective effect of IGF-II against the damage induced by 1-methyl-4-phenylpyridinium (MPP+) in neuronal dopaminergic cell cultures and a mouse model of progressive PD. In the neuronal model, IGF-II counteracts the oxidative distress produced by MPP + protecting dopaminergic neurons. Improved mitochondrial function, increased nuclear factor (erythroid-derived 2)-like2 (NRF2) nuclear translocation along with NRF2-dependent upregulation of antioxidative enzymes, and modulation of mammalian target of rapamycin (mTOR) signalling pathway were identified as mechanisms leading to neuroprotection and the survival of dopaminergic cells. The neuroprotective effect of IGF-II against MPP + -neurotoxicity on dopaminergic neurons depends on the specific IGF-II receptor (IGF-IIr). In the mouse model, IGF-II prevents behavioural dysfunction and dopaminergic nigrostriatal pathway degeneration and mitigates neuroinflammation induced by MPP+. Our work demonstrates that hampering oxidative stress and normalising mitochondrial function through the interaction of IGF-II with its specific IGF-IIr are neuroprotective in both neuronal and mouse models. Thus, the modulation of the IGF-II/IGF-IIr signalling pathway may be a useful therapeutic approach for the prevention and treatment of PD.

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IGF-II hampers oxidative damage and promotes survival in a cellular model of PD.

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IGF-II avoids mitochondrial damage in dopaminergic cells in a model of PD.

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IGF-II receptor mediates the neuroprotective effect of IGF-II in a cellular model of PD.

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IGF-II prevents nigrostriatal degeneration and inflammation in a mice model of PD.

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IGF-II prevents behavioural dysfunction in a mice model of PD.

Treatment and Prevention of Neurocristopathies

Neurocristopathies form a heterogeneous group of rare diseases caused by abnormal development of neural crest cells. Heterogeneity of neurocristopathies directly relates to the nature of these migratory and multipotent cells, which generate dozens of specialized cell types throughout the body. Neurocristopathies are thus characterized by congenital malformations of tissues/organs that otherwise appear to have very little in common, such as the craniofacial skeleton and enteric nervous system. Treatment options are currently very limited, mainly consisting of corrective surgeries. Yet, as reviewed here, analyses of normal and pathological neural crest development in model organisms have opened up the possibility for better treatment options involving cellular and molecular approaches. These approaches provide hope that some neurocristopathies might soon be curable or preventable.

Growth Factors in the Carotid Body-An Update

The carotid body may undergo plasticity changes during development/ageing and in response to environmental (hypoxia and hyperoxia), metabolic, and inflammatory stimuli. The different cell types of the carotid body express a wide series of growth factors and corresponding receptors, which play a role in the modulation of carotid body function and plasticity. In particular, type I cells express nerve growth factor, brain-derived neurotrophic factor, neurotrophin 3, glial cell line-derived neurotrophic factor, ciliary neurotrophic factor, insulin-like-growth factor-I and -II, basic fibroblast growth factor, epidermal growth factor, transforming growth factor-α and -β, interleukin-1β and -6, tumor necrosis factor-α, vascular endothelial growth factor, and endothelin-1. Many specific growth factor receptors have been identified in type I cells, indicating autocrine/paracrine effects. Type II cells may also produce growth factors and express corresponding receptors. Future research will have to consider growth factors in further experimental models of cardiovascular, metabolic, and inflammatory diseases and in human (normal and pathologic) samples. From a methodological point of view, microarray and/or proteomic approaches would permit contemporary analyses of large groups of growth factors. The eventual identification of physical interactions between receptors of different growth factors and/or neuromodulators could also add insights regarding functional interactions between different trophic mechanisms.

Molecular targets for endogenous glial cell line-derived neurotrophic factor modulation in striatal parvalbumin interneurons

Administration of recombinant glial cell line-derived neurotrophic factor into the putamen has been tested in preclinical and clinical studies to evaluate its neuroprotective effects on the progressive dopaminergic neuronal degeneration that characterizes Parkinson’s disease. However, intracerebral glial cell line-derived neurotrophic factor infusion is a challenging therapeutic strategy, with numerous potential technical and medical limitations. Most of these limitations could be avoided if the production of endogenous glial cell line-derived neurotrophic factor could be increased. Glial cell line-derived neurotrophic factor is naturally produced in the striatum from where it exerts a trophic action on the nigrostriatal dopaminergic pathway. Most of striatal glial cell line-derived neurotrophic factor is synthesized by a subset of GABAergic interneurons characterized by the expression of parvalbumin. We sought to identify molecular targets specific to those neurons and which are putatively associated with glial cell line-derived neurotrophic factor synthesis. To this end, the transcriptomic differences between glial cell line-derived neurotrophic factor-positive parvalbumin neurons in the striatum and parvalbumin neurons located in the nearby cortex, which do not express glial cell line-derived neurotrophic factor, were analysed. Using mouse reporter models, we have defined the genomic signature of striatal parvalbumin interneurons obtained by fluorescence-activated cell sorting followed by microarray comparison. Short-listed genes were validated by additional histological and molecular analyses. These genes code for membrane receptors (Kit, Gpr83, Tacr1, Tacr3, Mc3r), cytosolic proteins (Pde3a, Crabp1, Rarres2, Moxd1) and a transcription factor (Lhx8). We also found the proto-oncogene cKit to be highly specific of parvalbumin interneurons in the non-human primate striatum, thus highlighting a conserved expression between species and suggesting that specific genes identified in mouse parvalbumin neurons could be putative targets in the human brain. Pharmacological stimulation of four G-protein-coupled receptors enriched in the striatal parvalbumin interneurons inhibited Gdnf expression presumably by decreasing cyclic adenosine monophosphate formation. Additional experiments with pharmacological modulators of adenylyl cyclase and protein kinase A indicated that this pathway is a relevant intracellular route to induce Gdnf gene activation. This preclinical study is an important step in the ongoing development of a specific pro-endo-glial cell line-derived neurotrophic factor pharmacological strategy to treat Parkinson’s disease.

Meta-analysis of mouse transcriptomic studies supports a context-dependent astrocyte reaction in acute CNS injury versus neurodegeneration

Background

Neuronal damage in acute CNS injuries and chronic neurodegenerative diseases is invariably accompanied by an astrocyte reaction in both mice and humans. However, whether and how the nature of the CNS insult—acute versus chronic—influences the astrocyte response, and whether astrocyte transcriptomic changes in these mouse models faithfully recapitulate the astrocyte reaction in human diseases remains to be elucidated. We hypothesized that astrocytes set off different transcriptomic programs in response to acute versus chronic insults, besides a shared “pan-injury” signature common to both types of conditions, and investigated the presence of these mouse astrocyte signatures in transcriptomic studies from human neurodegenerative diseases.

Methods

We performed a meta-analysis of 15 published astrocyte transcriptomic datasets from mouse models of acute injury (n = 6) and chronic neurodegeneration (n = 9) and identified pan-injury, acute, and chronic signatures, with both upregulated (UP) and downregulated (DOWN) genes. Next, we investigated these signatures in 7 transcriptomic datasets from various human neurodegenerative diseases.

Results

In mouse models, the number of UP/DOWN genes per signature was 64/21 for pan-injury and 109/79 for acute injury, whereas only 13/27 for chronic neurodegeneration. The pan-injury-UP signature was represented by the classic cytoskeletal hallmarks of astrocyte reaction (Gfap and Vim), plus extracellular matrix (i.e., Cd44, Lgals1, Lgals3, Timp1), and immune response (i.e., C3, Serping1, Fas, Stat1, Stat2, Stat3). The acute injury-UP signature was enriched in protein synthesis and degradation (both ubiquitin-proteasome and autophagy systems), intracellular trafficking, and anti-oxidant defense genes, whereas the acute injury-DOWN signature included genes that regulate chromatin structure and transcriptional activity, many of which are transcriptional repressors. The chronic neurodegeneration-UP signature was further enriched in astrocyte-secreted extracellular matrix proteins (Lama4, Cyr61, Thbs4), while the DOWN signature included relevant genes such as Agl (glycogenolysis), S1pr1 (immune modulation), and Sod2 (anti-oxidant). Only the pan-injury-UP mouse signature was clearly present in some human neurodegenerative transcriptomic datasets.

Conclusions

Acute and chronic CNS injuries lead to distinct astrocyte gene expression programs beyond their common astrocyte reaction signature. However, caution should be taken when extrapolating astrocyte transcriptomic findings from mouse models to human diseases.

The Aqueous Extract from Ceratonia siliqua Leaves Protects Against 6-hydroxydopamine in Zebrafish: Understanding the Underlying Mechanism

Ceratonia siliqua L. is a Mediterranean medicinal plant traditionally cultivated for its ethnopharmacological benefits, such as antidiarrheal, antidiabetic, enhance acetylcholine, antioxidant, antiatherosclerotic, and for its possible anti-neurodegenerative potential. The aim of the present study was to evaluate the chemical composition, as well as the cognitive-enhancing, anxiolytic, and antioxidant activities of the aqueous extract from C. siliqua (CsAE) leaves against 6-hydroxydopamine (6-OHDA) zebrafish Parkinson’s disease (PD) model. CsAE (0.1, 0.3, and 1 mg/L) was administered by immersion to zebrafish (Danio rerio) for eight consecutive days and one hour before each behavioral test of each day, while 6-OHDA (250 µM) treatment was supplied one day before the novel tank diving test (NTT). Qualitative and quantitative analyses were performed by the ultra-high-performance liquid chromatography (UHPLC) analysis. The memory performance was evaluated through the NTT and Y-maze tests. Additionally, the in vitro and in vivo antioxidant status and acetylcholinesterase (AChE) activity was also assessed. Our finds demonstrated that CsAE presented positive antioxidant and anti-AChE activities, which contributed to the improvement of cognitive function in the 6-OHDA zebrafish PD model.

AQP1 and AQP4 Contribution to Cerebrospinal Fluid Homeostasis

Aquaporin 1 (AQP1), expressed in epithelial cells of the choroid plexus, and aquaporin 4 (AQP4) present in ependymal cells and glia limitants have been proposed to play a significant role in cerebrospinal fluid (CSF) production and homeostasis. However, the specific contribution of each water channel to these functions remains unknown, being a subject of debate during the last years. Here, we analyzed in detail how AQP1 and AQP4 participate in different aspects of the CSF homeostasis such as the load and drainage of ventricles, and further explored if these proteins play a role in the ventricular compliance. To do that, we carried out records of intraventricular pressure and CSF outflow, and evaluated ventricular volume by magnetic resonance imaging in AQP1^−/−, AQP4^−/−, double AQP1^−/−-AQP4^−/− knock out and wild type mice controls. The analysis performed clearly showed that both AQPs have a significant participation in the CSF production, and additionally revealed that the double AQP1-AQP4 mutation alters the CSF drainage and the ventricular compliance. The data reported here indicate a significant extra-choroidal CSF formation mediated by AQP4, supporting the idea of an important and constant CSF production/absorption process, sustained by efflux/influx of water between brain capillaries and interstitial fluid. Moreover, our results suggest the participation of AQPs in structural functions also related with CSF homeostasis such as the distensibility capacity of the ventricular system.

Combined effects of aquaporin-4 and hypoxia produce age-related hydrocephalus

Aquaporin-4, present in ependymal cells, in glia limiting and abundantly in pericapillary astrocyte foot processes, and aquaporin-1, expressed in choroid plexus epithelial cells, play an important role in cerebrospinal fluid production and may be involved in the pathophysiology of age-dependent hydrocephalus. The finding that brain aquaporins expression is regulated by low oxygen tension led us to investigate how hypoxia and elevated levels of cerebral aquaporins may result in an increase in cerebrospinal fluid production that could be associated with a hydrocephalic condition. Here we have explored, in young and aged mice exposed to hypoxia, whether aquaporin-4 and aquaporin-1 participate in the development of age-related hydrocephalus. Choroid plexus, striatum, cortex and ependymal tissue were analyzed separately both for mRNA and protein levels of aquaporins. Furthermore, parameters such as total ventricular volume, intraventricular pressure, cerebrospinal fluid outflow rate, ventricular compliance and cognitive function were studied in wild type, aquaporin-1 and aquaporin-4 knock-out animals subjected to hypoxia or normoxia. Our data demonstrate that hypoxia is involved in the development of age-related hydrocephalus by a process that depends on aquaporin-4 channels as a main route for cerebrospinal fluid movement. Significant increases in aquaporin-4 expression that occur over the course of animal aging, together with a reduced cerebrospinal fluid outflow rate and ventricular compliance, contribute to produce more severe hydrocephalus related to hypoxic events in aged mice, with a notable impairment in cognitive function. These results indicate that physiological events and/or pathological conditions presenting with cerebral hypoxia/ischemia contribute to the development of chronic adult hydrocephalus.

Long-term immunosuppression for CNS mouse xenotransplantation: Effects on nigrostriatal neurodegeneration and neuroprotective carotid body cell therapy

BACKGROUND

The use of long-term immunosuppressive treatments on neural transplantation has been controversial during the last decades. Although nowadays there is a consensus about the necessity of maintaining a permanent state of immunosuppression to preserve the survival of cerebral grafts, little is known about the effects that chronic immunosuppression produces both on the neurodegenerative process and on transplants function.

METHODS

Here, we establish a new immunosuppressive protocol, based on the discontinuous administration of CsA (15 mg/kg; s.c.) and prednisone (20 mg/kg; s.c.), to produce long-term immunosuppression in mice. Using this treatment, we analyse the effects that long-term immunosuppression induces in a chronic 1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine (MPTP) model of parkinsonism and on the neuroprotective and neurorestorative anti-parkinsonian actions exerted by rat carotid body (CB) xenografts.

RESULTS

This protocol preserves the survival of rat CB xenotransplants maintaining the general wellness of the grafted mice. Although permanent immunosuppression does not prevent the MPTP-induced cell death of nigral neurons and the consequent degeneration of dopaminergic striatal innervation, allowing for its use as Parkinson's disease (PD) model, it reduces the microglial activation and slightly declines the striatal damage. Moreover, we reported that chronic administration of immunosuppressant drugs does not alter the neuroprotective and restorative anti-parkinsonian actions of rat CB xenografts into parkinsonian mice.

CONCLUSIONS

This new immunosuppressive protocol provides a new murine model to assay the long-term effects of cerebral xenografts and offer a pharmacological alternative to the commonly used genetic immunodeficient mice, allowing the use of genetically modified mice as hosts. In addition, it will permit the experimental analysis of the effects produced by human CB xenografts in the chronic PD murine model, with the final aim of using CB allografts as an option of cell therapy in PD patients.

Synaptic Regulator α-Synuclein in Dopaminergic Fibers Is Essentially Required for the Maintenance of Subependymal Neural Stem Cells

Synaptic protein α-synuclein (α-SYN) modulates neurotransmission in a complex and poorly understood manner and aggregates in the cytoplasm of degenerating neurons in Parkinson's disease. Here, we report that α-SYN present in dopaminergic nigral afferents is essential for the normal cycling and maintenance of neural stem cells (NSCs) in the brain subependymal zone of adult male and female mice. We also show that premature senescence of adult NSCs into non-neurogenic astrocytes in mice lacking α-SYN resembles the effects of dopaminergic fiber degeneration resulting from chronic exposure to 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine or intranigral inoculation of aggregated toxic α-SYN. Interestingly, NSC loss in α-SYN-deficient mice can be prevented by viral delivery of human α-SYN into their sustantia nigra or by treatment with l-DOPA, suggesting that α-SYN regulates dopamine availability to NSCs. Our data indicate that α-SYN, present in dopaminergic nerve terminals supplying the subependymal zone, acts as a niche component to sustain the neurogenic potential of adult NSCs and identify α-SYN and DA as potential targets to ameliorate neurogenic defects in the aging and diseased brain.SIGNIFICANCE STATEMENT We report an essential role for the protein α-synuclein present in dopaminergic nigral afferents in the regulation of adult neural stem cell maintenance, identifying the first synaptic regulator with an implication in stem cell niche biology. Although the exact role of α-synuclein in neural transmission is not completely clear, our results indicate that it is required for stemness and the preservation of neurogenic potential in concert with dopamine.

Neuroprotective Surgical Strategies in Parkinson's Disease: Role of Preclinical Data

Although there have been many pharmacological agents considered to be neuroprotective therapy in Parkinson's disease (PD) patients, neurosurgical approaches aimed to neuroprotect or restore the degenerative nigrostriatal system have rarely been the focus of in depth reviews. Here, we explore the neuroprotective strategies involving invasive surgical approaches (NSI) using neurotoxic models 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which have led to clinical trials. We focus on several NSI approaches, namely deep brain stimulation of the subthalamic nucleus, glial neurotrophic derived factor (GDNF) administration and cell grafting methods. Although most of these interventions have produced positive results in preclinical animal models, either from behavioral or histological studies, they have generally failed to pass randomized clinical trials to validate each approach. We argue that NSI are promising approaches for neurorestoration in PD, but preclinical studies should be planned carefully in order not only to detect benefits but also to detect potential adverse effects. Further, clinical trials should be designed to be able to detect and disentangle neuroprotection from symptomatic effects. In summary, our review study evaluates the pertinence of preclinical models to study NSI for PD and how this affects their efficacy when translated into clinical trials.

Immunization with α-synuclein/Grp94 reshapes peripheral immunity and suppresses microgliosis in a chronic Parkinsonism model

Neuroinflammation mediated by chronically activated microglia, largely caused by abnormal accumulation of misfolded α-synuclein (αSyn) protein, is known to contribute to the pathophysiology of Parkinson's disease (PD). In this work, based on the immunomodulatory activities displayed by particular heat-shock proteins (HSPs), we tested a novel vaccination strategy that used a combination of αSyn and Grp94 (HSPC4 or Gp96) chaperone and a murine PD model. We used two different procedures, first, the adoptive transfer of splenocytes from αSyn/Grp94-immunized mice to recipient animals, and second, direct immunization with αSyn/Grp94, to study the effects in a chronic mouse MPTP-model of parkinsonism. We found that both approaches promoted a distinct profile in the peripheral system-supported by humoral and cellular immunity-consisting of a Th1-shifted αSyn-specific response accompanied by an immune-regulatory/Th2-skewed general phenotype. Remarkably, this mixed profile sustained by αSyn/Grp94 immunization led to strong suppression of microglial activation in the substantia nigra and striatum, pointing to a newly described positive effect of anti-αSyn Th1-responses in the context of PD. This strategy is the first to target αSyn and report the suppression of PD-associated microgliosis. Overall, we show that the αSyn/Grp94 combination supports a distinct and long-lasting immune profile in the peripheral system, which has an impact at the CNS level by suppressing chronic microglial activation in an MPTP model of PD. Furthermore, our study demonstrates that reshaping peripheral immunity by vaccination with appropriate misfolding protein/HSP combinations could be highly beneficial as a treatment for neurodegenerative misfolding diseases.

Neural crest stem cells and their potential therapeutic applications

The neural crest (NC) is a remarkable transient structure generated during early vertebrate development. The neural crest progenitors have extensive migratory capacity and multipotency, harboring stem cell-like characteristics such as self-renewal. They can differentiate into a variety of cell types from craniofacial skeletal tissues to the trunk peripheral nervous system (PNS). Multiple regulators such as signaling factors, transcription factors, and migration machinery components are expressed at different stages of NC development. Gain- and loss-of-function studies in various vertebrate species revealed epistatic relationships of these molecules that could be assembled into a gene regulatory network defining the processes of NC induction, specification, migration, and differentiation. These basic developmental studies led to the subsequent establishment and molecular validation of neural crest stem cells (NCSCs) derived by various strategies. We provide here an overview of the isolation and characterization of NCSCs from embryonic, fetal, and adult tissues; the experimental strategies for the derivation of NCSCs from embryonic stem cells, induced pluripotent stem cells, and skin fibroblasts; and recent developments in the use of patient-derived NCSCs for modeling and treating neurocristopathies. We discuss future research on further refinement of the culture conditions required for the differentiation of pluripotent stem cells into axial-specific NC progenitors and their derivatives, developing non-viral approaches for the generation of induced NC cells (NCCs), and using a genomic editing approach to correct genetic mutations in patient-derived NCSCs for transplantation therapy. These future endeavors should facilitate the therapeutic applications of NCSCs in the clinical setting.

Gene Expression Profiling Supports the Neural Crest Origin of Adult Rodent Carotid Body Stem Cells and Identifies CD10 as a Marker for Mesectoderm-Committed Progenitors

Neural stem cells (NSCs) are promising tools for understanding nervous system plasticity and repair, but their use is hampered by the lack of markers suitable for their prospective isolation and characterization. The carotid body (CB) contains a population of peripheral NSCs, which support organ growth during acclimatization to hypoxia. We have set up CB neurosphere (NS) cultures enriched in differentiated neuronal (glomus) cells versus undifferentiated progenitors to investigate molecular hallmarks of cell classes within the CB stem cell (CBSC) niche. Microarray gene expression analysis in NS is compatible with CBSCs being neural crest derived-multipotent progenitor cells able to sustain CB growth upon exposure to hypoxia. Moreover, we have identified CD10 as a marker suitable for isolation of a population of CB mesectoderm-committed progenitor cells. CD10 + cells are resting in normoxia, and during hypoxia they are activated to proliferate and to eventually complete maturation into mesectodermal cells, thus participating in the angiogenesis necessary for CB growth. Our results shed light into the molecular and cellular mechanisms involved in CBSC fate choice, favoring a potential use of these cells for cell therapy. Stem Cells 2016;34:1637-1650.

Therapeutic potentials of human adipose-derived stem cells on the mouse model of Parkinson's disease

The treatment of Parkinson's disease (PD) using stem cells has long been the focus of many researchers, but the ideal therapeutic strategy has not yet been developed. The consistency and high reliability of the experimental results confirmed by animal models are considered to be a critical factor in the stability of stem cell transplantation for PD. Therefore, the aim of this study was to investigate the preventive and therapeutic potential of human adipose-derived stem cells (hASC) for PD and was to identify the related factors to this therapeutic effect. The hASC were intravenously injected into the tail vein of a PD mouse model induced by 6-hydroxydopamine. Consequently, the behavioral performances were significantly improved at 3 weeks after the injection of hASC. Additionally, dopaminergic neurons were rescued, the number of structure-modified mitochondria was decreased, and mitochondrial complex I activity was restored in the brains of the hASC-injected PD mouse model. Overall, this study underscores that intravenously transplanted hASC may have therapeutic potential for PD by recovering mitochondrial functions.

GDNF-based therapies, GDNF-producing interneurons, and trophic support of the dopaminergic nigrostriatal pathway. Implications for Parkinson's disease

The glial cell line-derived neurotrophic factor (GDNF) is a well-established trophic agent for dopaminergic (DA) neurons in vitro and in vivo. GDNF is necessary for maintenance of neuronal morphological and neurochemical phenotype and protects DA neurons from toxic damage. Numerous studies on animal models of Parkinson’s disease (PD) have reported beneficial effects of GDNF on nigrostriatal DA neuron survival. However, translation of these observations to the clinical setting has been hampered so far by side effects associated with the chronic continuous intra-striatal infusion of recombinant GDNF. In addition, double blind and placebo-controlled clinical trials have not reported any clinically relevant effect of GDNF on PD patients. In the past few years, experiments with conditional Gdnf knockout mice have suggested that GDNF is necessary for maintenance of DA neurons in adulthood. In parallel, new methodologies for exogenous GDNF delivery have been developed. Recently, it has been shown that a small population of scattered, electrically interconnected, parvalbumin positive (PV+) GABAergic interneurons is responsible for most of the GDNF produced in the rodent striatum. In addition, cholinergic striatal interneurons appear to be also involved in the modulation of striatal GDNF. In this review, we summarize current knowledge on brain GDNF delivery, homeostasis, and its effects on nigrostriatal DA neurons. Special attention is paid to the therapeutic potential of endogenous GDNF stimulation in PD.

Neurotrophic Properties, Chemosensory Responses and Neurogenic Niche of the Human Carotid Body

The carotid body (CB) is a polymodal chemoreceptor that triggers the hyperventilatory response to hypoxia necessary for the maintenance of O(2) homeostasis essential for the survival of organs such as the brain or heart. Glomus cells, the sensory elements in the CB, are also sensitive to hypercapnia, acidosis and, although less generally accepted, hypoglycemia. Current knowledge on CB function is mainly based on studies performed on lower mammals, but the information on the human CB is scant. Here we describe the structure, neurotrophic properties, and cellular responses to hypoxia and hypoglycemia of CBs dissected from human cadavers. The adult CB parenchyma contains clusters of chemosensitive glomus (type I) and sustentacular (type II) cells as well as nestin-positive progenitor cells. This organ also expresses high levels of the dopaminotrophic glial cell line-derived neurotrophic factor (GDNF). GDNF production and the number of progenitor and glomus cells were preserved in the CBs of human subjects of advanced age. As reported for other mammalian species, glomus cells responded to hypoxia by external Ca(2+)-dependent increase of cytosolic [Ca(2+)] and quantal catecholamine release. Human glomus cells are also responsive to hypoglycemia and together the two stimuli, hypoxia and hypoglycemia, can potentiate each other's effects. The chemo-sensory responses of glomus cells are also preserved at an advanced age. Interestingly, a neurogenic niche similar to that recently described in rodents is also preserved in the adult human CB. These new data on the cellular and molecular physiology of the CB pave the way for future pathophysiological studies involving this organ in humans.

Direct confocal acquisition of fluorescence from X-gal staining on thick tissue sections

X-gal staining is a common procedure used in the histochemical monitoring of gene expression by light microscopy. However, this procedure does not permit the direct confocal acquisition of images, thus preventing the identification of labelled cells on the depth (Z) axis of tissue sections and leading sometimes to erroneous conclusions in co-localization and gene expression studies. Here we report a technique, based on X-gal fluorescence emission and mathematically-based optical correction, to obtain high quality fluorescence confocal images. This method, combined with immunofluorescence, makes it possible to unequivocally identify X-gal-labelled cells in tissue sections, emerging as a valuable tool in gene expression and cell tracing analysis.