Therapeutic potentials of human embryonic stem cells in Parkinson's disease

CRISPR/Cas9 assisted stem cell therapy in Parkinson's disease

Since its discovery in 2012, CRISPR Cas9 has been tried as a direct treatment approach to correct the causative gene mutation and establish animal models in neurodegenerative disorders. Since no strategy developed until now could completely cure Parkinson's disease (PD), neuroscientists aspire to use gene editing technology, especially CRISPR/Cas9, to induce a permanent correction in genetic PD patients expressing mutated genes. Over the years, our understanding of stem cell biology has improved. Scientists have developed personalized cell therapy using CRISPR/Cas9 to edit embryonic and patient-derived stem cells ex-vivo. This review details the importance of CRISPR/Cas9-based stem cell therapy in Parkinson's disease in developing PD disease models and developing therapeutic strategies after elucidating the possible pathophysiological mechanisms.

Role of Genes and Treatments for Parkinson’s Disease

Parkinson’s Disease (PD) is a complex neurodegenerative disorder that mainly results due to the loss of dopaminergic neurons in the substantia nigra of the midbrain. It is well known that dopamine is synthesized in substantia nigra and is transported to the striatumvianigrostriatal tract. Besides the sporadic forms of PD, there are also familial cases of PD and number of genes (both autosomal dominant as well as recessive) are responsible for PD. There is no permanent cure for PD and to date, L-dopa therapy is considered to be the best option besides having dopamine agonists. In the present review, we have described the genes responsible for PD, the role of dopamine, and treatment strategies adopted for controlling the progression of PD in humans.

Pluripotent stem cell-derived dopaminergic neurons as models of neurodegeneration

Researchers utilize a number of models of Parkinson’s disease ranging in complexity from immortalized cell lines to nonhuman primates. These models are used to investigate everything from the mechanisms underlying neurodegeneration, to drugs that may improve patient outcomes. Each model system has advantages and disadvantages, depending on their application. In this review, the authors assess the potential value of embryonic stem and induced-pluripotent stem cells as additions to the crowded Parkinson’s disease in vitro model landscape.

Mesenchymal autologous stem cells

The use of cell-based therapies for spinal cord injuries has recently gained prominence as a potential therapy or component of a combination strategy. Experimental and clinical studies have been performed using mesenchymal stem cell therapy to treat spinal cord injuries with encouraging results. However, there have been reports on the adverse effects of these stem cell-based therapies, especially in the context of tumor modulation. This article surveys the literature relevant to the potential of mesenchymal autologous stem cells for spinal cord injuries and their clinical implications.

Induced pluripotent stem cells and neurodegenerative diseases

Neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease and Amyotrophic Lateral Sclerosis, are characterized by idiopathic neuron loss in different regions of the central nervous system, which contributes to the relevant dysfunctions in the patients. The application of cell replacement therapy using human embryonic stem (hES) cells, though having attracted much attention, has been hampered by the intrinsic ethical problems. It has been demonstrated that adult somatic cells can be reprogrammed into the embryonic state, called induced pluripotent stem (iPS) cells. It is soon realized that iPS cells may be an alternative source for cell replacement therapy, because it raises no ethical problems and using patient-specific iPS cells for autologous transplantation will not lead to immunological rejection. What's more, certain types of neurons derived from patient-specific iPS cells may display disease-relevant phenotypes. Thus, patient-specific iPS cells can provide a unique opportunity to directly investigate the pathological properties of relevant neural cells in individual patient, and to study the vulnerability of neural cells to pathogenic factors in vitro, which may help reveal the pathogenesis of many neurodegenerative diseases. In this review, the recent development in cellular treatment of neurodegenerative diseases using iPS cells was summarized, and the potential value of iPS cells in the modeling of neurodegenerative disease was discussed.

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.

Single and local blockade of interleukin-6 signaling promotes neuronal differentiation from transplanted embryonic stem cell-derived neural precursor cells

Safe and efficient transplantation of embryonic stem (ES) cells to the brain requires that local inflammatory and immune responses to allogeneic grafts are inhibited. To investigate cytokines that affect graft cell survival and differentiation, we used stromal cell-derived inducing activity to induce the differentiation of neural progenitor cells (NPCs) from mouse ES cells and transplanted the NPCs into mouse brain. Examination of surrounding brain tissue revealed elevated expression levels of interleukin (IL)-1β, IL-4, and IL-6 in response to NPC transplantation. Among these, only IL-6 reduced neuronal differentiation and promoted glial differentiation in vitro. When we added anti-IL-6 receptor antibodies to NPCs during transplantation, this single and local blockade of IL-6 signaling reduced the accumulation of host-derived leukocytes, including microglia. Furthermore, it also promoted neuronal differentiation and reduced glial differentiation from the grafted NPCs to an extent similar to that with systemic and continuous administration of cyclosporine A. These results suggest that local administration of anti-IL-6 receptor antibodies with NPCs may promote neuronal differentiation during the treatment of neurological diseases with cell replacement therapy.

Cell-surface ultrastructural changes during the in vitro neuron-like differentiation of rat bone marrow-derived mesenchymal stem cells

The neuron-like differentiation of bone marrow-derived mesenchymal stem cells (BMMSCs) has been extensively studied. However, the alternations of the cell-surface ultrastructures and the membrane tension/reservoir of the cells during this differentiation process are poorly understood. Therefore, atomic force microscopy (AFM) was utilized in this study to observe the cell-surface ultrastructural changes among rat bone marrow-derived mesenchymal stem cells (rBMMSCs), partially differentiated cells, and fully differentiated neuron-like cells. By analyzing the stiffness of plasma membranes, lamellipodial extensions, average heights of small membrane protrusions and relatively larger uplifted structures, and peak-peak spacing among protrusions and/or uplifted structures, we found that the membrane reservoir may potentially decrease upon the differentiation from rBMMSCs to partially differentiated cells and to fully differentiated neuron-like cells. The results may help to better understanding the membrane tension of various types of cells and related biological processes, such as membrane traffic, cell adhesion, motility, differentiation, among others. The data also implies that AFM may be a useful tool for evaluating membrane reservoir by imaging cell-surface ultrastructures.

Repeated courses of granulocyte colony-stimulating factor in amyotrophic lateral sclerosis: clinical and biological results from a prospective multicenter study

Granulocyte colony-stimulating factor (G-CSF) induces a transient mobilization of hematopoietic progenitor cells from bone marrow to peripheral blood. Our aim was to evaluate safety of repeated courses of G-CSF in patients with amyotrophic lateral sclerosis (ALS), assessing disease progression and changes in chemokine and cytokine levels in serum and cerebrospinal fluid (CSF). Twenty-four ALS patients entered an open-label, multicenter trial in which four courses of G-CSF and mannitol were administered at 3-month intervals. Levels of G-CSF were increased after treatment in the serum and CSF. Few and transitory adverse events were observed. No significant reduction of the mean monthly decrease in ALSFRS-R score and forced vital capacity was observed. A significant reduction in CSF levels of monocyte chemoattractant protein-1 (MCP-1) and interleukin-17 (IL-17) was observed. G-CSF treatment was safe and feasible in a multicenter series of ALS patients. A decrease in the CSF levels of proinflammatory cytokines MCP-1 and IL-17 was found, indicating a G-CSF-induced central anti-inflammatory response.

Activin/nodal signaling and pluripotency

Maintenance of a pluripotent cell population during mammalian embryogenesis is crucial for the proper generation of extraembryonic and embryonic tissues to ensure intrauterine survival and fetal development. Pluripotent stem cells derived from early stage mammalian embryos are known as "embryonic stem cells." Such embryo-derived stem cells can proliferate indefinitely in vitro and give rise to derivatives of all three primary germ layers. Their potential for clinical and commercial applications has sparked great excitement within scientific and lay communities. Identification of the signaling pathways controlling stem cell pluripotency and differentiation provides knowledge-based approaches to manipulate stem cells for regenerative medicine. One of the signaling cascades that has been identified in the control of stem cell pluripotency and differentiation is the Activin/Nodal pathway. Here, we describe the differences among pluripotent cell types and discuss the latest findings on the molecular mechanisms involving Activin/Nodal signaling in controlling their pluripotency and differentiation.

Silencing of Rho-GDIgamma by RNAi promotes the differentiation of neural stem cells

RNA interference (RNAi) technology is one of the main means in the study of stem cell differentiation. This study describes Rho-GDIgamma function during the differentiation of neural stem cells by using RNAi. Rho-GDIgamma belongs to the Rho-GDI protein family, which is expressed at high level throughout the brain. Although it exists in neuronal population, its physiological function is poorly understood. By using RNAi technology to downregulate expression of Rho-GDIgamma, we found distinct morphological changes in neural stem cell line C17.2. More important, RT-PCR confirmed that RNAi-mediated downregulation of Rho-GDIgamma decreased expression of Rho-GDIgamma-regulated genes RhoA and slightly increased expression of Rac1. Further, immunochemical staining indicated that downregulation of Rho-GDIgamma increased the tendency of C17.2 cells to differentiate. These data strongly suggest that Rho-GDIgamma plays a key role in the differentiation of neural stem cells.

Cell Therapy From Bench to Bedside Translation in CNS Neurorestoratology Era

Recent advances in cell biology, neural injury and repair, and the progress towards development of neurorestorative interventions are the basis for increased optimism. Based on the complexity of the processes of demyelination and remyelination, degeneration and regeneration, damage and repair, functional loss and recovery, it would be expected that effective therapeutic approaches will require a combination of strategies encompassing neuroplasticity, immunomodulation, neuroprotection, neurorepair, neuroreplacement, and neuromodulation. Cell-based restorative treatment has become a new trend, and increasing data worldwide have strongly proven that it has a pivotal therapeutic value in CNS disease. Moreover, functional neurorestoration has been achieved to a certain extent in the CNS clinically. Up to now, the cells successfully used in preclinical experiments and/or clinical trial/treatment include fetal/embryonic brain and spinal cord tissue, stem cells (embryonic stem cells, neural stem/progenitor cells, hematopoietic stem cells, adipose-derived adult stem/precursor cells, skin-derived precursor, induced pluripotent stem cells), glial cells (Schwann cells, oligodendrocyte, olfactory ensheathing cells, astrocytes, microglia, tanycytes), neuronal cells (various phenotypic neurons and Purkinje cells), mesenchymal stromal cells originating from bone marrow, umbilical cord, and umbilical cord blood, epithelial cells derived from the layer of retina and amnion, menstrual blood-derived stem cells, Sertoli cells, and active macrophages, etc. Proof-of-concept indicates that we have now entered a new era in neurorestoratology.

Endoplasmic reticulum stress induced by tunicamycin and antagonistic effect of Tiantai No.1 (1) on mesenchymal stem cells

OBJECTIVE

Changes of the internal and external cellular environments can induce calcium homeostasis disorder and unfolded protein aggregation in the endoplasmic reticulum (ER). This ER function disorder is called endoplasmic reticulum stress (ERS). Severe long-term ERS can trigger the ER apoptosis signaling pathway, resulting in cell apoptosis and organism injury. Recent researches revealed that ERS-induced cell death was involved in the neurocyte retrogradation in the progress of neuron degenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease and so on. Therefore, the protection effect of the traditional Chinese drug-Tiantai No. 1 (1) on the ERS injury of AD was investigated at the molecular gene level in this study with a view to explore the gene pharmacodynamic actions and mechanisms of this drug.

METHODS

Primarily cultured marrow mesenchymal stem cells (MSCs) of rats were treated by tunicamycin (TM) in order to induce ERS. RT-PCR, fluorescence immunocytochemistry and Western blot techniques were used to determine the mRNA and protein expression levels of the protective stress protein-ER molecular chaperones GRP78 and GRP94 (which would assist cells to resist cellular stress injury), and to determine the mRNA and protein expression levels of apoptosis promoting molecule Caspase-12 on the membrane of the ER, respectively.

RESULTS

Protein expression levels of GRP78 and GRP94 were significantly increased in the TM-induced MSCs, and the mRNA level of Caspase-12 was also remarkably increased in the TM-induced MSCs (P<0.05). All these proved that the ERS model was successfully established by TM in MSC. Meanwhile, the mRNA and protein levels of GRP78 and GRP94 were all significantly increased compared with the model group (P<0.05 or P<0.01) after MSCs were treated with Tiantai No.1 while the mRNA and protein expression levels of Caspase-12 were significantly decreased compared with the model group (P<0.05 or P<0.01). This effect showed a dose dependent manner.

CONCLUSION

Tiantai No.1 might attenuate the cell apoptosis induced by ERS injury, and thus protect the neurons against AD.

In vitro neural differentiation of human embryonic stem cells using a low-density mouse embryonic fibroblast feeder protocol

Human embryonic stem cells (hESCs) have the capacity to self-renew and to differentiate into all components of the embryonic germ layers (ectoderm, mesoderm, endoderm) and subsequently all cell types that comprise human tissues. HESCs can potentially provide an extraordinary source of cells for tissue engineering and great insight into early embryonic development. Much attention has been given to the possibility that hESCs and their derivatives may someday play major roles in the study of the development, disease therapeutics, and repair of injuries to the central and peripheral nervous systems. This tantalizing promise will be realized only when we understand fundamental biological questions about stem cell growth and development into distinct tissue types. In vitro, differentiation of hESCs into neurons proceeds as a multistep process that in many ways recapitulates development of embryonic neurons. We have found in vitro conditions that promote differentiation of stem cells into neuronal precursor or neuronal progenitor cells. Specifically, we have investigated the ability of two federally approved hESC lines, HSF-6 and H7, to form embryonic and mature neuronal cells in culture. Undifferentiated hESCs stain positively for markers of undifferentiated/pluripotent hESCs including surface glycoproteins, SSEA-3 and 4, and transcription factors Oct-3/4 and Nanog. Using reduced numbers of mouse embryonic fibroblasts as feeder substrates, these markers of pluripotency are lost quickly and replaced by primarily neuroglial phenotypes with only a few cells representing other embryonic germ layer types remaining. Within the first 2 weeks of co-culture with reduced MEFs, the undifferentiated hESCs show progression from neuroectodermal to neural stem cell to maturing and migrating neurons to mature neurons in a stepwise fashion that is dependent on both the type of hESCs and the density of MEFs. In this chapter, we provide the methods for culturing pluripotent hESCs and MEFs, differentiating hESCs using reduced density MEFs, and phenotypic analyses of this culture system.

Neuroprotective effects of laminin and its KDI domain

Successful treatment of neurodegenerative diseases and CNS trauma are the most intractable problems in modern medicine. Numerous reports have shown the strong role that laminins have on the survival, regeneration and development of various types of cells, including neural cells. It would be desirable to take advantage of laminin activities for therapeutic purposes. However, there are at least ten laminin variants and the trimeric molecules are of the order of 800,000 molecular weight. Furthermore, human laminins are not available in quantity. Therefore, we and others have taken the approach of determining which domains of the laminin molecules are functional in the CNS, and whether short peptides from these regions exhibit biological activities with the intent of testing their potential for therapeutic use. Understanding the role of laminins and their small biologically active peptide domains, such as the KDI (lysine–aspartic acid–isoleucine) peptide from γ1 laminin, in neuronal development, CNS trauma (spinal cord injury and stroke) and neurodegenerative disorders (amyotrophic lateral sclerosis, Alzheimer’s disease and Parkinson’s disease) may help to develop clinically applicable methods to treat the presently untreatable CNS diseases and trauma even in the near future.

Multitracer assessment of dopamine function after transplantation of embryonic stem cell-derived neural stem cells in a primate model of Parkinson's disease

The ability of primate embryonic stem (ES) cells to differentiate into dopamine (DA)-synthesizing neurons has raised hopes of creating novel cell therapies for Parkinson's disease (PD). As the primary purpose of cell transplantation in PD is restoration of dopaminergic neurotransmission in the striatum, in vivo assessment of DA function after grafting is necessary to achieve better therapeutic effects. A chronic model of PD was produced in two cynomolgus monkeys (M-1 and M-2) by systemic administration of neurotoxin. Neural stem cells (NSCs) derived from cynomolgus ES cells were implanted unilaterally in the putamen. To evaluate DA-specific functions, we used multiple [(11)C]-labeled positron emission tomography (PET) tracers, including [beta-(11)C]L-3,4-dihydroxyphenylalanine (L-[beta-(11)C]DOPA, DA precursor ligand), [(11)C]-2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane ([(11)C]beta-CFT, DA transporter ligand) and [(11)C]raclopride (D(2) receptor ligand). At 12 weeks after grafting NSCs, PET demonstrated significantly increased uptake of L-[beta-(11)C]DOPA (M-1:41%, M-2:61%) and [(11)C]beta-CFT (M-1:31%, M-2:36%) uptake in the grafted putamen. In addition, methamphetamine challenge in M-2 induced reduced [(11)C]raclopride binding (16%) in the transplanted putamen, suggesting release of DA. These results show that transplantation of NSCs derived from cynomolgus monkey ES cells can restore DA function in the putamen of a primate model of PD. PET with multitracers is useful for functional studies in developing cell-based therapies against PD.

Cells therapy for Parkinson's disease--so close and so far away

One of the strategies of treating Parkinson's disease (PD) is the replacement of lost neurons in the substantia nigra with healthy dapamingergic cells. Potential sources for cells range from autologous grafts of dopamine secreting cells, fetal ventral mesencephalon tissue, to various stem cell types. Over the past quarter century, many experimental replacement therapies have been tried on PD animal models as well as human patients, yet none resulted in satisfactory outcomes that warrant wide applications. Recent progress in stem cell biology has shown that nuclear transfer embryonic stem cells (ntES) or induced pluripotent stem cells (iPS) derived cells can be used to successfully treat rodent PD models, thus solving the problem of immunorejection and paving the way for future autologous transplantations for treating PD. Meanwhile, however, post mortem analysis of patients who received fetal brain cell transplantation revealed that implanted cells are prone to degeneration just like endogenous neurons in the same pathological area, indicating long-term efficacy of cell therapy of PD needs to overcome the degenerating environment in the brain. A better understanding of neurodegeneration in the midbrain appeared to be a necessary step in developing new cell therapies in Parkinson's disease. It is likely that future cell replacement will focus on not only ameliorating symptoms of the disease but also trying to slow the progression of the disease by either neuroprotection or restoring the micro-environment in the midbrain.

A new perspective on the treatment of aromatic L-amino acid decarboxylase deficiency

The final step in production of the neurotransmitters dopamine and serotonin is catalyzed by aromatic l-amino acid decarboxylase (AADC). AADC deficiency is a debilitating genetic condition that results in a deficit in these neurotransmitters, and manifests in infancy as a severe movement disorder with developmental delay. Response to current treatments is often disappointing. We have reviewed the literature to look for improvements to the current treatment strategy and also for new directions for AADC deficiency treatment. There may be differences in the mode of action, side-effect risk and effectiveness between different dopamine agonists and monoamine oxidase inhibitors currently used for AADC deficiency treatment. The range of these drugs used requires re-evaluation as some may have greater efficacy than others. Pyridoxal 5'-phosphate, the AADC cofactor may stabilize AADC and could increase AADC activity. Pyridoxal 5'-phosphate could have advantages as a treatment instead of pyridoxine. Atypical neuroleptics and peripheral AADC inhibitors both increase AADC activity in vivo and could be a future direction for AADC deficiency treatment and related conditions. Parkinson's disease gene therapy to deliver and express the human AADC gene in striatum is being tested in humans. Consequently gene therapy for AADC deficiency could be a realistic aim however an animal model of AADC deficiency is important for further progression.

Impact of Magnetic Labeling on Human and Mouse Stem Cells and Their Long-Term Magnetic Resonance Tracking in a Rat Model of Parkinson Disease

Magnetic resonance imaging (MRI) of magnetically labeled stem cells has become a valuable tool in the understanding and evaluation of experimental stem cell–based therapies of degenerative central nervous system disorders. This comprehensive study assesses the impact of magnetic labeling of both human and rodent stem cell–containing populations on multiple biologic parameters as maintenance of stemness and oxidative stress levels. Cells were efficiently magnetically labeled with very small superparamagnetic iron oxide particles. Only under the condition of tailored labeling strategies can the impact of magnetic labeling on vitality, proliferation, pluripotency, and oxidative stress levels be minimized. In a rat model of Parkinson disease, magnetically labeled mouse embryonic stem cells were tracked by high-field MRI for 6 months. Significant interindividual differences concerning the spatial distribution of cells became evident. Histologically, transplanted green fluorescent protein–positive iron oxide–labeled cells were clearly identified. No significant increase in oxidative stress levels at the implantation site and no secondary uptake of magnetic label by host phagocytotic cells were observed. Our study strongly suggests that molecular MRI approaches must be carefully tailored to the respective cell population to exert minimal physiologic impact, ensuring the feasibility of this imaging approach for clinical applications.

Transplantation of GABA-producing cells for seizure control in models of temporal lobe epilepsy

A high percentage of patients with temporal lobe epilepsy (TLE) are refractory to conventional pharmacotherapy. The progressive neurodegenerative processes associated with a lifetime of uncontrolled seizures mandate the development of alternative approaches to treat this disease. Transplantation of inhibitory cells has been suggested as a potential therapeutic strategy to achieve seizure suppression in humans with intractable TLE. Preclinical investigations over 20 years have demonstrated that multiple cell types from several sources can produce anticonvulsant, and antiepileptogenic, effects in animal models of TLE. Transplanting GABA-producing cells, in particular, has been shown to reduce seizures in several well-established models. This review addresses experimentation using different sources of transplantable GABAergic cells, highlighting progress with fetal tissue, neural cell lines, and stem cells. Regardless of the source of the GABAergic cells used in seizure studies, common challenges have emerged. Several variables influence the anticonvulsant potential of GABA-producing cells. For example, tissue availability, graft survival, immunogenicity, tumorigenicity, and varying levels of cell migration, differentiation, and integration into functional circuits and the microenvironment provided by sclerotic tissue all contribute to the efficacy of transplanted cells. The challenge of understanding how all of these variables work in concert, in a disease process that has no well-established etiology, suggests that there is still much basic research to be done before rational cell-based therapies can be developed for TLE.

Neural progenitors derived from human embryonic stem cells are targeted by allogeneic T and natural killer cells

Neural progenitor cells (NPC) of foetal origin or derived from human embryonic stem cells (HESC) have the potential to differentiate into mature neurons after transplantation into the central nervous system, opening the possibility of cell therapy for neurodegenerative disorders. In most cases, the transplanted NPC are genetically unrelated to the recipient, leading to potential rejection of the transplanted cells. Very few data provide reliable information as to the potential immune response of allogeneic neural progenitors derived from HESC. In this study, we analyzed in vitro the allogeneic immune response of T lymphocytes and natural killer (NK) cells to NPC derived from HESC or of foetal origin. We demonstrate that NPC induce T-cell stimulation and a strong NK cytotoxic response. NK-cell activity is unrelated to MHC-I expression but driven by the activating NKG2D receptor. Cyclosporine and dexamethasone previously used in clinical studies with foetal NPC did not only fail to prevent NK alloreactivity but strongly inhibited the terminal maturation from NPC into mature neurons. We conclude that allogenic transplantation of NPC in the central nervous system will most likely require an immunosuppressive regimen targeting allogenic T and NK cells, whereas possible interference with the differentiation of NPC needs to be carefully evaluated.

Human embryonic stem cells and lung regeneration

Human embryonic stem cells are pluripotent cells derived from the inner cell mass of preimplantation stage embryos. Their unique potential to give rise to all differentiated cell types has generated great interest in stem cell research and the potential that it may have in developmental biology, medicine and pharmacology. The main focus of stem cell research has been on cell therapy for pathological conditions with no current methods of treatment, such as neurodegenerative diseases, cardiac pathology, retinal dysfunction and lung and liver disease. The overall aim is to develop methods of application either of pure cell populations or of whole tissue parts to the diseased organ under investigation. In the field of pulmonary research, studies using human embryonic stem cells have succeeded in generating enriched cultures of type II pneumocytes in vitro. On account of their potential of indefinite proliferation in vitro, embryonic stem cells could be a source of an unlimited supply of cells available for transplantation and for use in gene therapy. Uncovering the ability to generate such cell types will expand our understanding of biological processes to such a degree that disease understanding and management could change dramatically.

Experimental therapeutics for dystonia

Dystonia is a neurological syndrome characterized by excessive involuntary muscle contractions leading to twisting movements and unnatural postures. It has many different clinical manifestations, and many different causes. More than 3 million people worldwide suffer from dystonia, yet there are few broadly effective treatments. In the past decade, progress in research has advanced our understanding of the pathogenesis of dystonia to a point where drug discovery efforts are now feasible. Several strategies can be used to develop novel therapeutics for dystonia. Existing therapies have only modest efficacy, but may be refined and improved to increase benefits while reducing side effects. Identifying rational targets for drug intervention based on the pathogenesis of dystonia is another strategy. The surge in both basic and clinical research discoveries has provided insights at all levels, including etiological, physiological and nosological, to enable such a targeted approach. The empirical approach to drug discovery, whereby compounds are identified using a nonmechanistic strategy, is complementary to the rational approach. With the recent development of multiple animal models of dystonia, it is now possible to develop assays and perform drug screens on vast numbers of compounds. This multifaceted approach to drug discovery in dystonia will likely provide lead compounds that can then be translated for clinical use.