Restorative approaches in Parkinson's Disease: Which cell type wins the race?

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.

Impedance-based Real-time Monitoring of Neural Stem Cell Differentiation

We present here the first impedance-based characterization of the differentiation process of two human mesencephalic fetal neural stem lines. The two dopaminergic neural stem cell lines used in this study, Lund human mesencephalic (LUHMES) and human ventral mesencephalic (hVM1 Bcl-X_L), have been developed for the study of Parkinsonian pathogenesis and its treatment using cell replacement therapy. We show that if only relying on impedance magnitude analysis, which is by far the most usual approach in, e.g., cytotoxicity evaluation and drug screening applications, one may not be able to distinguish whether the neural stem cells in a population are proliferating or differentiating. However, the presented results highlight that equivalent circuit analysis can provide detailed information on cellular behavior, e.g. simultaneous changes in cell morphology, cell-cell contacts, and cell adhesion during formation of neural projections, which are the fundamental behavioral differences between proliferating and differentiating neural stem cells. Moreover, our work also demonstrates the sensitivity of impedance-based monitoring with capability to provide information on changes in cellular behavior in relation to proliferation and differentiation. For both of the studied cell lines, in already two days (one day after induction of differentiation) equivalent circuit analysis was able to show distinction between proliferation and differentiation conditions, which is significantly earlier than by microscopic imaging. This study demonstrates the potential of impedance-based monitoring as a technique of choice in the study of stem cell behavior, laying the foundation for screening assays to characterize stem cell lines and testing the efficacy epigenetic control.

Pyrolytic Carbon Nanograss Enhances Neurogenesis and Dopaminergic Differentiation of Human Midbrain Neural Stem Cells

Advancements in research on the interaction of human neural stem cells (hNSCs) with nanotopographies and biomaterials are enhancing the ability to influence cell migration, proliferation, gene expression, and tailored differentiation toward desired phenotypes. Here, the fabrication of pyrolytic carbon nanograss (CNG) nanotopographies is reported and demonstrated that these can be employed as cell substrates boosting hNSCs differentiation into dopaminergic neurons (DAn), a long-time pursued goal in regenerative medicine based on cell replacement. In the near future, such structures can play a crucial role in the near future for stem-cell based cell replacement therapy (CRT) and bio-implants for Parkinson's disease (PD). The unique combination of randomly distributed nanograss topographies and biocompatible pyrolytic carbon material is optimized to provide suitable mechano-material cues for hNSCs adhesion, division, and DAn differentiation of midbrain hNSCs. The results show that in the presence of the biocoating poly-L-lysine (PLL), the CNG enhances hNSCs neurogenesis up to 2.3-fold and DAn differentiation up to 3.5-fold. Moreover, for the first time, consistent evidence is provided, that CNGs without any PLL coating are not only supporting cell survival but also lead to significantly enhanced neurogenesis and promote hNSCs to acquire dopaminergic phenotype compared to PLL coated topographies.

LncRNA H19 diminishes dopaminergic neuron loss by mediating microRNA-301b-3p in Parkinson's disease via the HPRT1-mediated Wnt/β-catenin signaling pathway

Long non-coding RNAs (lncRNA) and microRNAs (miRNAs) are a subject of active investigation in neurodegenerative disorders including Parkinson's disease (PD). We hypothesized a regulatory role of lncRNA H19 with involvement of hypoxanthine phosphoribosyltransferase 1 (HPRT1) in dopaminergic neuron loss in PD model mice obtained by 6-hydroxydopamine (6-OHDA) lesions. We predicted the differentially expressed genes and related mechanisms by microarray analysis. We measured the expression of tyrosine hydroxylase (TH) and proneural genes in the substantia nigra of lesioned mice before and after treatment with lentiviral oe-HPRT1, agomir-miR-301b-3p and inhibition of the Wnt/β-catenin pathway. We also evaluated the relationship among lncRNA H19, HPRT1 and miR-301b-3p as well as the Wnt/β-catenin signaling pathway in these mice. The obtained results predicted and further confirmed a low level of HPRT1 in lesioned mice. We found low expression of lncRNA H19 and showed that its forced overexpression regulated HPRT1 by binding to miR-301b-3p. The overexpression of HPRT1 increased TH expression and inhibited dopaminergic neuron loss via activating the Wnt/β-catenin pathway, as reflected by increased expressions of Nurr-1, Pitx-3, Ngn-2 and NeuroD1. Thus, overexpressed lncRNA H19 protects against dopaminergic neuron loss in this PD model through activating the Wnt/β-catenin pathway via impairing miR-301b-3p-targeted inhibition of HPRT1 expression.

The Substantia Nigra Is Permissive and Gains Inductive Signals When Lesioned for Dopaminergic Differentiation of Embryonic Stem Cells

Transplantation of dopaminergic (DA) cells into the striatum can rescue from dopamine deficiency in a Parkinson's disease condition, but this is not a suitable procedure for regaining the full control of motor activity. The minimal condition toward recovering the nigrostriatal pathway is the proper innervation of transplanted DA neurons or their precursors from the substancia nigra pars compacta (SNpc) to their target areas. However, functional integration of transplanted cells would require first that the host SNpc is suitable for their survival and/or differentiation. We recently reported that the intact adult SNpc holds a strong neurogenic environment, but primed embryonic stem cells (ie, embryoid body cells, EBCs) could not derive into DA neurons. In this study, we transplanted into the intact or lesioned SNpc, EBCs derived from embryonic stem cells that were prompt to differentiate into DA neurons by the forced expression of Lmx1a in neural precursor cells (R1B5/NesE-Lmx1a). We observed that, 6 days posttransplantation (dpt), R1B5 or R1B5/NesE-Lmx1a EBCs gave rise to Nes⁺ and Dcx⁺ cells within the host SNpc, but a large number of Th⁺ cells derived only from EBCs exogenously expressing Lmx1a. In contrast, when transplantation was carried out into the 6-hydroxidopamine-lesioned SNpc, the emergence of Th⁺ cells from EBCs was independent of exogenous Lmx1a expression, although these cells were not found by 15 dpt. These results suggest that the adult SNpc is not only a permissive niche for initiation of DA differentiation of non-neuralized cells but also releases factors upon damage that promote the acquisition of DA characteristics by transplanted EBCs.

Wnt/β-Catenin Signaling Pathway Governs a Full Program for Dopaminergic Neuron Survival, Neurorescue and Regeneration in the MPTP Mouse Model of Parkinson's Disease

Wingless-type mouse mammary tumor virus (MMTV) integration site (Wnt) signaling is one of the most critical pathways in developing and adult tissues. In the brain, Wnt signaling contributes to different neurodevelopmental aspects ranging from differentiation to axonal extension, synapse formation, neurogenesis, and neuroprotection. Canonical Wnt signaling is mediated mainly by the multifunctional β-catenin protein which is a potent co-activator of transcription factors such as lymphoid enhancer factor (LEF) and T-cell factor (TCF). Accumulating evidence points to dysregulation of Wnt/β-catenin signaling in major neurodegenerative disorders. This review highlights a Wnt/β-catenin/glial connection in Parkinson's disease (PD), the most common movement disorder characterized by the selective death of midbrain dopaminergic (mDAergic) neuronal cell bodies in the subtantia nigra pars compacta (SNpc) and gliosis. Major findings of the last decade document that Wnt/β-catenin signaling in partnership with glial cells is critically involved in each step and at every level in the regulation of nigrostriatal DAergic neuronal health, protection, and regeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD, focusing on Wnt/β-catenin signaling to boost a full neurorestorative program in PD.

Redirection of neuroblast migration from the rostral migratory stream into a lesion in the prefrontal cortex of adult rats

Clinical treatment of structural brain damage today is largely limited to symptomatic approaches and the avoidance of secondary injury. However, neuronal precursor cells are constantly produced within specified regions of the mammalian brain throughout life. Here we evaluate the potential of the known chemoattractive properties of the glycoprotein laminin on neuroblasts to relocate the cells into damaged brain areas. Injection of a thin laminin tract, leading from the rostral migratory stream to an excitotoxic lesion within the medial prefrontal cortex of rats, enabled neuroblasts to migrate away from their physiological route towards the olfactory bulb into the lesion site. Once they reached the damaged tissue, they migrated further in a non-uniform orientation within the lesion. Furthermore, our data indicate that the process of diverted migration is still active 6 weeks after the treatment and that at least some of the neuroblasts are capable of maturing into adult neurons.

Intermittent, low dose carbon monoxide exposure enhances survival and dopaminergic differentiation of human neural stem cells

Exploratory studies using human fetal tissue have suggested that intrastriatal transplantation of dopaminergic neurons may become a future treatment for patients with Parkinson's disease. However, the use of human fetal tissue is compromised by ethical, regulatory and practical concerns. Human stem cells constitute an alternative source of cells for transplantation in Parkinson's disease, but efficient protocols for controlled dopaminergic differentiation need to be developed. Short-term, low-level carbon monoxide (CO) exposure has been shown to affect signaling in several tissues, resulting in both protection and generation of reactive oxygen species. The present study investigated the effect of CO produced by a novel CO-releasing molecule on dopaminergic differentiation of human neural stem cells. Short-term exposure to 25 ppm CO at days 0 and 4 significantly increased the relative content of β-tubulin III-immunoreactive immature neurons and tyrosine hydroxylase expressing catecholaminergic neurons, as assessed 6 days after differentiation. Also the number of microtubule associated protein 2-positive mature neurons had increased significantly. Moreover, the content of apoptotic cells (Caspase3) was reduced, whereas the expression of a cell proliferation marker (Ki67) was left unchanged. Increased expression of hypoxia inducible factor-1α and production of reactive oxygen species (ROS) in cultures exposed to CO may suggest a mechanism involving mitochondrial alterations and generation of ROS. In conclusion, the present procedure using controlled, short-term CO exposure allows efficient dopaminergic differentiation of human neural stem cells at low cost and may as such be useful for derivation of cells for experimental studies and future development of donor cells for transplantation in Parkinson's disease.

Old and new challenges in Parkinson's disease therapeutics

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons and/or loss od neuronal projections, in several dopaminergic networks. Current treatments for idiopathic PD rely mainly on the use of pharmacologic agents to improve motor symptomatology of PD patients. Nevertheless, so far PD remains an incurable disease. Therefore, it is of utmost importance to establish new therapeutic strategies for PD treatment. Over the last 20 years, several molecular, gene and cell/stem-cell therapeutic approaches have been developed with the aim of counteracting or retarding PD progression. The scope of this review is to provide an overview of PD related therapies and major breakthroughs achieved within this field. In order to do so, this review will start by focusing on PD characterization and current treatment options covering thereafter molecular, gene and cell/stem cell-based therapies that are currently being studied in animal models of PD or have recently been tested in clinical trials. Among stem cell-based therapies, those using MSCs as possible disease modifying agents for PD therapy and, specifically, the MSCs secretome contribution to meet the clinical challenge of counteracting or retarding PD progression, will be more deeply explored.

Functional Rescue of Dopaminergic Neuron Loss in Parkinson's Disease Mice After Transplantation of Hematopoietic Stem and Progenitor Cells

Parkinson's disease is a common neurodegenerative disorder, which is due to the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and for which no definitive cure is currently available. Cellular functions in mouse and human tissues can be restored after fusion of bone marrow (BM)-derived cells with a variety of somatic cells. Here, after transplantation of hematopoietic stem and progenitor cells (HSPCs) in the SNpc of two different mouse models of Parkinson's disease, we significantly ameliorated the dopaminergic neuron loss and function. We show fusion of transplanted HSPCs with neurons and with glial cells in the ventral midbrain of Parkinson's disease mice. Interestingly, the hybrids can undergo reprogramming in vivo and survived up to 4 weeks after transplantation, while acquiring features of mature astroglia. These newly generated astroglia produced Wnt1 and were essential for functional rescue of the dopaminergic neurons. Our data suggest that glial-derived hybrids produced upon fusion of transplanted HSPCs in the SNpc can rescue the Parkinson's disease phenotype via a niche-mediated effect, and can be exploited as an efficient cell-therapy approach.

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Transplantation of HSPCs into the substantia nigra of PD mice ameliorates dopaminergic neuron loss and function.

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Hybrids generated after fusion of transplanted HSPCs undergo reprogramming in vivo and acquire features of mature astroglia.

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Newly generated astroglia produced Wnt1 and can functionally rescue the dopaminergic neuron loss.

A definitive therapy for Parkinson's disease is not available. Here, we transplanted hematopoietic stem and progenitor cells into the substantia nigra of brains of two different mouse models of Parkinson's disease. These transplanted cells fused with neurons and glial cells of the recipient mice. Four weeks after transplantation, the hybrids acquired features of mature astroglia, secreted Wnt1, and functionally ameliorated dopaminergic neuron loss. Current cell therapy approaches are being pursued in the striatum with the aim to increase dopamine levels. Here we show that the loss of dopaminergic neurons can be protected against by direct actions in the substantia nigra.

Differentiated Cells Derived from Fetal Neural Stem Cells Improve Motor Deficits in a Rat Model of Parkinson's Disease

Objective

Parkinson's disease (PD), which is one of the most common neurodegenerative disorders, is characterized by the loss of dopamine (DA) neurons in the substantia nigra in the midbrain. Experimental and clinical studies have shown that fetal neural stem cells (NSCs) have therapeutic effects in neurological disorders. The aim of this study was to examine whether cells that were differentiated from NSCs had therapeutic effects in a rat model of PD.

Methods

NSCs were isolated from 14-week-old embryos and induced to differentiate into neurons, DA neurons, and glial cells, and these cells were characterized by their expression of the following markers: βIII-tubulin and microtubule-associated protein 2 (neurons), tyrosine hydroxylase (DA neurons), and glial fibrillary acidic protein (glial cells). After a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was generated, the differentiated cells were transplanted into the striata of the 6-OHDA-lesioned PD rats.

Results

The motor behaviors of the PD rats were assessed by the number of apomorphine-induced rotation turns. The results showed that the NSCs differentiated in vitro into neurons and DA neurons with high efficiencies. After transplantation into the striata of the PD rats, the differentiated cells significantly improved the motor deficits of the transplanted PD rats compared to those of the control nontransplanted PD rats by decreasing the apomorphine-induced turn cycles as early as 4 weeks after transplantation. Immunofluorescence analyses showed that the differentiated DA neurons survived more than 16 weeks.

Conclusions

Our results showed that cells that were differentiated from NSCs had therapeutic effects in a rat PD model, which suggests that differentiated cells may be an effective treatment for patients with PD.

Wnt/β-catenin signaling is required to rescue midbrain dopaminergic progenitors and promote neurorepair in ageing mouse model of Parkinson's disease

Wnt/β-catenin signaling is required for specification and neurogenesis of midbrain dopaminergic (mDA) neurons, the pivotal neuronal population that degenerates in Parkinson's disease (PD), and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Wnt/β-catenin signaling plays a vital role in adult neurogenesis but whether it might engage DA neurogenesis/neurorepair in the affected PD brain is yet unresolved. Recently, the adult midbrain aqueduct periventricular regions (Aq-PVRs) were shown to harbor multipotent clonogenic neural stem/progenitor cells (mNPCs) with DA potential in vitro, but restrictive mechanisms in vivo are believed to limit their DA regenerative capacity. Using in vitro mNPC culture systems we herein demonstrate that aging is one most critical factor restricting mNPC neurogenic potential via dysregulation of Wnt/β-catenin signaling. Coculture paradigms between young/aged (Y/A) mNPCs and Y/A astrocytes identified glial age and a decline of glial-derived factors including Wnts as key determinants of impaired neurogenic potential, whereas Wnt activation regimens efficiently reversed the diminished proliferative, neuronal, and DA differentiation potential of A-mNPCs. Next, in vivo studies in wild (Wt) and transgenic β-catenin reporter mice uncovered Wnt/β-catenin signaling activation and remarkable astrocyte remodeling of Aq-PVR in response to MPTP-induced DA neuron death. Spatio-temporal analyses unveiled β-catenin signaling in predopaminergic (Nurr1(+)/TH(-)) and imperiled or rescuing DAT(+) neurons during MPTP-induced DA neuron injury and self-repair. Aging inhibited Wnt signaling, whereas β-catenin activation in situ with a specific GSK-3β antagonist promoted a significant degree of DA neurorestoration associated with reversal of motor deficit, with implications for neurorestorative approaches in PD.

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.

Development of stem cell-based therapy for Parkinson's disease

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders of aging, characterized by the degeneration of dopamine neurons (DA neurons) in the substantial nigra, leading to the advent of both motor symptoms and non-motor symptoms. Current treatments include electrical stimulation of the affected brain areas and dopamine replacement therapy. Even though both categories are effective in treating PD patients, the disease progression cannot be stopped. The research advance into cell therapies provides exciting potential for the treatment of PD. Current cell sources include neural stem cells (NSCs) from fetal brain tissues, human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs) and directly induced dopamine neurons (iDA neurons). Here, we evaluate the research progress in different cell sources with a focus on using iPSCs as a valuable source and propose key challenges for developing cells suitable for large-scale clinical applications in the treatment of PD.

Perivascular Mesenchymal Stem Cells From the Adult Human Brain Harbor No Instrinsic Neuroectodermal but High Mesodermal Differentiation Potential

Brain perivascular cells have recently been identified as a novel mesodermal cell type in the human brain. These cells reside in the perivascular niche and were shown to have mesodermal and, to a lesser extent, tissue-specific differentiation potential. Mesenchymal stem cells (MSCs) are widely proposed for use in cell therapy in many neurological disorders; therefore, it is of importance to better understand the "intrinsic" MSC population of the human brain. We systematically characterized adult human brain-derived pericytes during in vitro expansion and differentiation and compared these cells with fetal and adult human brain-derived neural stem cells (NSCs) and adult human bone marrow-derived MSCs. We found that adult human brain pericytes, which can be isolated from the hippocampus and from subcortical white matter, are-in contrast to adult human NSCs-easily expandable in monolayer cultures and show many similarities to human bone marrow-derived MSCs both regarding both surface marker expression and after whole transcriptome profile. Human brain pericytes showed a negligible propensity for neuroectodermal differentiation under various differentiation conditions but efficiently generated mesodermal progeny. Consequently, human brain pericytes resemble bone marrow-derived MSCs and might be very interesting for possible autologous and endogenous stem cell-based treatment strategies and cell therapeutic approaches for treating neurological diseases.

SIGNIFICANCE

Perivascular mesenchymal stem cells (MSCs) recently gained significant interest because of their appearance in many tissues including the human brain. MSCs were often reported as being beneficial after transplantation in the central nervous system in different neurological diseases; therefore, adult brain perivascular cells derived from human neural tissue were systematically characterized concerning neural stem cell and MSC marker expression, transcriptomics, and mesodermal and inherent neuroectodermal differentiation potential in vitro and in vivo after in utero transplantation. This study showed the lack of an innate neuronal but high mesodermal differentiation potential. Because of their relationship to mesenchymal stem cells, these adult brain perivascular mesodermal cells are of great interest for possible autologous therapeutic use.

Phosphodiesterase 7 inhibition induces dopaminergic neurogenesis in hemiparkinsonian rats

Parkinson's disease is characterized by a loss of dopaminergic neurons in a specific brain region, the ventral midbrain. Parkinson's disease is diagnosed when approximately 50% of the dopaminergic neurons of the substantia nigra pars compacta (SNpc) have degenerated and the others are already affected by the disease. Thus, it is conceivable that all therapeutic strategies, aimed at neuroprotection, start too late. Therefore, an urgent medical need exists to discover new pharmacological targets and novel drugs with disease-modifying properties. In this regard, modulation of endogenous adult neurogenesis toward a dopaminergic phenotype might provide a new strategy to target Parkinson's disease by partially ameliorating the dopaminergic cell loss that occurs in this disorder. We have previously shown that a phosphodiesterase 7 (PDE7) inhibitor, S14, exerts potent neuroprotective and anti-inflammatory effects in different rodent models of Parkinson's disease, indicating that this compound could represent a novel therapeutic agent to stop the dopaminergic cell loss that occurs during the progression of the disease. In this report we show that, in addition to its neuroprotective effect, the PDE7 inhibitor S14 is also able to induce endogenous neuroregenerative processes toward a dopaminergic phenotype. We describe a population of actively dividing cells that give rise to new neurons in the SNpc of hemiparkinsonian rats after treatment with S14. In conclusion, our data identify S14 as a novel regulator of dopaminergic neuron generation.

SIGNIFICANCE

Parkinson's disease is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the ventral midbrain. Currently, no cure and no effective disease-modifying therapy are available for Parkinson's disease; therefore, an urgent medical need exists to discover new pharmacological targets and novel drugs for the treatment of this disorder. The present study reports that an inhibitor of the enzyme phosphodiesterase 7 (S14) induces proliferation in vitro and in vivo of neural stem cells, promoting its differentiation toward a dopaminergic phenotype and therefore enhancing dopaminergic neuron generation. Because this drug is also able to confer neuroprotection of these cells in animal models of Parkinson's disease, S14 holds great promise as a therapeutic new strategy for this disorder.

Magnetic resonance monitoring of superparamagnetic iron oxide (SPIO)-labeled stem cells transplanted into the inner ear

In the field of regenerative medicine, cell transplantation or cell-based therapies for inner ear defects are considered to be promising candidates for a therapeutic strategy. In this paper, we report on a study that examined the use of magnetic resonance imaging (MRI) to monitor stem cells transplanted into the cochlea labeled with superparamagnetic iron oxide (SPIO), a contrast agent commonly used with MRI. First, we demonstrated in vitro that stem cells efficiently took up SPIO particles. This was confirmed by Prussian blue staining and TEM. In MRI studies, T2 relaxation times of SPIO-labeled cells decreased in a dose-dependent manner. Next, we transplanted SPIO-labeled cells directly into the cochlea in vivo and then performed MRI 1h, 2 weeks, and 4 weeks after transplantation. The images were evaluated objectively by measuring signal intensity (SI). SI within the ears receiving transplants was significantly lower (P<0.05) than that of control sides at the 1-h assessment. This novel method will be helpful for evaluating stem cell therapies, which represents a new strategy for inner ear regeneration. To the best of our knowledge, this study is the first to demonstrate that local transplantation of labeled stem cells into the inner ear can be visualized in vivo via MRI.

Cell based therapies in Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder after Alzheimer’s disease. It is characterized by bradykinesia, hypokinesia/ akinesia, rigidity, tremor, and postural instability, caused by dopaminergic (DA) striatal denervation. The prevalence of PD increases from 50 years of age with steep rise after age 60 years. Current treatment of PD relies heavily on replacing lost dopamine either with its precursor L-dopa or dopamine agonists (ropinirole, pramipexole, bromocriptine, lisuride etc). Other pharmacological measures like catechol-O-methyltrasferase (COMT) inhibitors like entacopone, telcapone and monoamine oxidase B (MAO-B) inhibitors like selegiline and rasagiline are also useful, while L-dopa remains the gold standard in the treatment of PD. Emerging therapies are focusing on cell based therapeutics derived from various sources.

Adult subventricular zone neural stem cells as a potential source of dopaminergic replacement neurons

Clinical trials engrafting human fetal ventral mesencephalic tissue have demonstrated, in principle, that cell replacement therapy provides substantial long-lasting improvement of motor impairments generated by Parkinson's Disease (PD). The use of fetal tissue is not practical for widespread clinical implementation of this therapy, but stem cells are a promising alternative source for obtaining replacement cells. The ideal stem cell source has yet to be established and, in this review, we discuss the potential of neural stem cells in the adult subventricular zone (SVZ) as an autologous source of replacement cells. We identify three key challenges for further developing this potential source of replacement cells: (1) improving survival of transplanted cells, (2) suppressing glial progenitor proliferation and survival, and (3) developing methods to efficiently produce dopaminergic neurons. Subventricular neural stem cells naturally produce a dopaminergic interneuron phenotype that has an apparent lack of vulnerability to PD-mediated degeneration. We also discuss whether olfactory bulb dopaminergic neurons derived from adult SVZ neural stem cells are a suitable source for cell replacement strategies.

The pharmacology of regenerative medicine

Regenerative medicine is a rapidly evolving multidisciplinary, translational research enterprise whose explicit purpose is to advance technologies for the repair and replacement of damaged cells, tissues, and organs. Scientific progress in the field has been steady and expectations for its robust clinical application continue to rise. The major thesis of this review is that the pharmacological sciences will contribute critically to the accelerated translational progress and clinical utility of regenerative medicine technologies. In 2007, we coined the phrase "regenerative pharmacology" to describe the enormous possibilities that could occur at the interface between pharmacology, regenerative medicine, and tissue engineering. The operational definition of regenerative pharmacology is "the application of pharmacological sciences to accelerate, optimize, and characterize (either in vitro or in vivo) the development, maturation, and function of bioengineered and regenerating tissues." As such, regenerative pharmacology seeks to cure disease through restoration of tissue/organ function. This strategy is distinct from standard pharmacotherapy, which is often limited to the amelioration of symptoms. Our goal here is to get pharmacologists more involved in this field of research by exposing them to the tools, opportunities, challenges, and interdisciplinary expertise that will be required to ensure awareness and galvanize involvement. To this end, we illustrate ways in which the pharmacological sciences can drive future innovations in regenerative medicine and tissue engineering and thus help to revolutionize the discovery of curative therapeutics. Hopefully, the broad foundational knowledge provided herein will spark sustained conversations among experts in diverse fields of scientific research to the benefit of all.

Cell based therapy in Parkinsonism

Parkinson's disease (PD) is a synucleinopathy-induced chronic progressive neurodegenerative disorder, worldwide affecting about 5 million humans. As of yet, actual therapies are symptomatic, and neuroprotective strategies are an unmet need. Due to their capability to transdifferentiate, to immune modulate and to increase neuroplasticity by producing neurotrophic factors, adult stem cells (ASC) might fill this gap. Preclinical research in 6-hydroxydopamine (6-OHDA) and/or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) lesioned animals established persistent improvements of motor behavior after ASC-treatment. Histological/histochemical measurements in these animals evidenced an intracerebral applied ASC-induced increase of Tyrosine Hydroxylase-positive (TH+) cells with increased striatal dopamine levels, suggesting cell rescue. Likewise, clinical experience with subventricular applied ASCs in PD patients, although limited, is encouraging, evidencing neurorescue especially during the early phase of the disease. In multiple system atrophy (MSA) or progressive supranuclear palsy (PSP) patients, though, only marginal reduced progression of natural progression could be established after subventricular or intravasal ASC implantations.

AAV2-neurturin (CERE-120) for Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is a common and chronic movement disorder with no therapy yet proven to alter the underlying advancing pathology. Gene delivery of trophic factors, which have shown disease modifying potential in preclinical PD models, are now being evaluated in early clinical trials.

AREAS COVERED

This review discusses early experiences with glial-derived neurotrophic factor in PD, the initial studies using AAV2-neurturin in PD patients, the lessons learned from these studies and the future directions of this therapy.

EXPERT OPINION

Gene therapy has emerged as a potential breakthrough in the treatment of PD and early clinical trials using AAV2-neurturin, a trophic factor that has shown the ability to protect dopaminergic degeneration in preclinical PD models, are underway. While trophic protection of dopamine neurons would be a significant breakthrough, PD remains a widespread disorder that involves neurodegeneration across multiple cellular types. We believe that these initial studies with AAV2-neurturin are significant steps toward the realization of gene delivery of trophic factors as a viable therapy, though the ultimate goal must be that of comprehensive neurorestoration.

Composite Brains: Toward a Systems Theory of Neural Reconstruction

The results of uncontrolled, open-label clinical trials indicate that reconstructive cellular therapies have the capacity to produce meaningful functional improvements in patients with brain disorders. However, the transplantation of fetal cells has not progressed to viable best practice treatment for any brain disorder. A conceptual approach, referred to as the Repair Model, has served as a useful heuristic for initiating research in the field and guiding the development of new practices. Analysis of evidence for the treatment of Parkinson's disease indicates that recovery following neural grafting is a complex process influenced by factors beyond the replacement of neurons. An alternative approach, the Composite Brain Model, is outlined to address limitations of the Repair Model. A hierarchical, open-system model is proposed, which aims to track the interactions between the grafted cells, the host brain, and the environment. The Composite Brain Model emphasizes the importance of the interactions between the patient, their physical and social environment, and the provision of rehabilitation during recovery. It is proposed that the Composite Brain Model is useful in providing an alternative perspective for research, theory building, and practice.

Conotoxins that confer therapeutic possibilities

Cone snails produce a distinctive repertoire of venom peptides that are used both as a defense mechanism and also to facilitate the immobilization and digestion of prey. These peptides target a wide variety of voltage- and ligand-gated ion channels, which make them an invaluable resource for studying the properties of these ion channels in normal and diseased states, as well as being a collection of compounds of potential pharmacological use in their own right. Examples include the United States Food and Drug Administration (FDA) approved pharmaceutical drug, Ziconotide (Prialt^®; Elan Pharmaceuticals, Inc.) that is the synthetic equivalent of the naturally occurring ω-conotoxin MVIIA, whilst several other conotoxins are currently being used as standard research tools and screened as potential therapeutic drugs in pre-clinical or clinical trials. These developments highlight the importance of driving conotoxin-related research. A PubMed query from 1 January 2007 to 31 August 2011 combined with hand-curation of the retrieved articles allowed for the collation of 98 recently identified conotoxins with therapeutic potential which are selectively discussed in this review. Protein sequence similarity analysis tentatively assigned uncharacterized conotoxins to predicted functional classes. Furthermore, conotoxin therapeutic potential for neurodegenerative disorders (NDD) was also inferred.

Differentiated human midbrain-derived neural progenitor cells express excitatory strychnine-sensitive glycine receptors containing α2β subunits

BACKGROUND

Human fetal midbrain-derived neural progenitor cells (NPCs) may deliver a tissue source for drug screening and regenerative cell therapy to treat Parkinson's disease. While glutamate and GABA(A) receptors play an important role in neurogenesis, the involvement of glycine receptors during human neurogenesis and dopaminergic differentiation as well as their molecular and functional characteristics in NPCs are largely unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Here we investigated NPCs in respect to their glycine receptor function and subunit expression using electrophysiology, calcium imaging, immunocytochemistry, and quantitative real-time PCR. Whole-cell recordings demonstrate the ability of NPCs to express functional strychnine-sensitive glycine receptors after differentiation for 3 weeks in vitro. Pharmacological and molecular analyses indicate a predominance of glycine receptor heteromers containing α2β subunits. Intracellular calcium measurements of differentiated NPCs suggest that glycine evokes depolarisations mediated by strychnine-sensitive glycine receptors and not by D-serine-sensitive excitatory glycine receptors. Culturing NPCs with additional glycine, the glycine-receptor antagonist strychnine, or the Na(+)-K(+)-Cl(-) co-transporter 1 (NKCC1)-inhibitor bumetanide did not significantly influence cell proliferation and differentiation in vitro.

CONCLUSIONS/SIGNIFICANCE

These data indicate that NPCs derived from human fetal midbrain tissue acquire essential glycine receptor properties during neuronal maturation. However, glycine receptors seem to have a limited functional impact on neurogenesis and dopaminergic differentiation of NPCs in vitro.

Intrathecal application of autologous bone marrow cell preparations in Parkinsonian syndromes

BACKGROUND

A growing number of patients is treated with intrathecal application of autologous bone marrow cells (aBMCs), but clinical data are completely lacking in movement disorders. We provide first clinical data on efficacy and safety of this highly experimental treatment approach in parkinsonian syndromes.

METHODS

Retrospective data collection from patients with parkinsonism who spontaneously sought cell treatment. The application procedure was neither recommended nor performed by the authors.

RESULTS

We report 17 patients with parkinsonian syndromes (Parkinson's disease [PD], n = 7; multiple system atrophy [MSA], n = 7; various, n = 3) who received intrathecal application of aBMCs. We did not observe any changes in motor function, activities of daily living, global clinical impression, or antiparkinsonian medication after a median observation period of 10 months. Two patients reported a worsening of parkinsonian symptoms, but the intervention was otherwise safe and well-tolerated.

CONCLUSIONS

Intrathecal application of aBMCs in uncontrolled conditions produces no clinical benefit in parkinsonian syndromes.

Stem cell therapy ameliorates bladder dysfunction in an animal model of Parkinson disease

PURPOSE

Different cell based therapies have been tested, focusing on motor function. We evaluated the effect of human amniotic fluid stem cells and bone marrow derived mesenchymal stem cells (ALLCELLS, Emeryville, California) on bladder dysfunction in a rat model of Parkinson disease.

MATERIAL AND METHODS

A nigrostriatal lesion was induced by 6-hydroxydopamine in 96 athymic nude female rats divided into 3 treatment groups. After 2 weeks the groups were injected with human amniotic fluid stem cells, bone marrow derived mesenchymal stem cells and vehicle for sham treatment, respectively. At 3, 7, 14 and 28 days the bladder function of 8 rats per group was analyzed by conscious cystometry. Brains were extracted for immunostaining.

RESULTS

The nigrostriatal lesion caused bladder dysfunction, which was consistent in sham treated animals throughout the study. Several cystometric parameters improved 14 days after human amniotic fluid stem cell or bone marrow derived mesenchymal stem cell injection, concomitant with the presence of human stem cells in the brain. At 14 days only a few cells were observed in a more caudal and lateral position. At 28 days the functional improvement subsided and human stem cells were no longer seen. Human stem cell injection improved the survival of dopaminergic neurons until 14 days. Human stem cells expressed superoxide dismutase-2 and seemed to modulate the expression of interleukin-6 and glial cell-derived neurotrophic factor by host cells.

CONCLUSIONS

Cell therapy with human amniotic fluid stem cells and bone marrow derived mesenchymal stem cells temporarily ameliorated bladder dysfunction in a Parkinson disease model. In contrast to integration, cells may act on the injured environment via cell signaling.

Cell replacement therapy for Parkinson's disease: how close are we to the clinic?

Cell replacement therapy (CRT) offers great promise as the future of regenerative medicine in Parkinson´s disease (PD). Three decades of experiments have accumulated a wealth of knowledge regarding the replacement of dying neurons by new and healthy dopaminergic neurons transplanted into the brains of animal models and affected patients. The first clinical trials provided the proof of principle for CRT in PD. In these experiments, intrastriatal transplantation of human embryonic mesencephalic tissue reinnervated the striatum, restored dopamine levels and showed motor improvements. Sequential controlled studies highlighted several problems that should be addressed prior to the wide application of CRT for PD patients. Moreover, owing to ethical and practical problems, embryonic stem cells require replacement by better-suited stem cells. Several obstacles remain to be surpassed, including identifying the best source of stem cells for A9 dopaminergic neuron generation, eliminating the risk of tumor formation and the development of graft-induced dyskinesias, and standardizing dopaminergic cell production in order to enable clinical application. In this article, we present an update on CRT for PD, reviewing the research milestones, various stem cells used and tailored differentiation methods, and analyze the information gained from the clinical trials.

Bone marrow-derived mesenchymal stem cells as immunosuppressants in liver transplantation: a review of current data

This article provides an overview of the current knowledge relating to the potential use of bone marrow-derived mesenchymal stem cells (BM-MSCs) acting as immunosuppressants after liver transplantation. Clinical use of BM-MSCs in liver transplantation remains experimental, as there is uncertainty as to their mechanism of action, conflicting studies in animal models, and the possibility of their cellular fusion with hepatocytes leading to potentially genetically unstable hepatocytes. These obstacles, to their underuse, have been decreasing, and BM-MSCs have elicited great interest for possible use in solid organ transplantation. Bone marrow-derived-MSCs, when transplanted systemically, might positively influence grafted organ outcome through cell-cell contact or the secretion of soluble factors that are immunomodulatory. Thus, the use of BM-MSCs to modulate organ rejection may directly or indirectly influence the survival properties of transplanted livers.

The surgical management of Parkinson’s disease

SUMMARY Parkinson’s disease (PD) is one of the most frequently encountered neurodegenerative disorders in terms of worldwide prevalence. Although medications are typically effective at treating motor symptoms in early to moderately advanced stages, the efficacy of these agents often wanes as the disease progresses. With long-term pharmacologic therapy, many PD patients will also experience motor fluctuations, dyskinesias and unpredictable wearing off of the therapeutic benefit. Deep brain stimulation, the preferred surgical treatment for PD, often improves many of these complications. New surgical options are currently under clinical investigation for advanced PD patients including gene and cell-based therapies.

Modulation of the generation of dopaminergic neurons from human neural stem cells by Bcl-X(L): mechanisms of action

Understanding the developmental mechanisms governing dopaminergic neuron generation and maintenance is crucial for the development of neuronal replacement therapeutic procedures, like in Parkinson's disease (PD), but also for research aimed at drug screening and pharmacology. In the present chapter, we review the present situation using stem cells of different origins (pluripotent and multipotent) and summarize current manipulations of stem cells for the enhancement of dopaminergic neuron generation, focusing on the actions of Bcl-X(L). Bcl-X(L) not only enhances dopaminergic neuron survival but also augments the expression of key developmental and maintenance genes, and, through the lengthening of the cell cycle early during differentiation, regulates cell fate decisions, producing a net enhancement of neurogenesis. The relevance of these findings is discussed in the context of basic neurogenesis and also for the development of efficient cell therapy in PD.