Neural Grafts Research Articles

Scaffolds for Intracerebral Grafting of Neural Progenitor Cells After Cerebral Infarction: A Systematic Review.

ContextIntracerebral grafting of neural progenitor cells is a promising potential treatment to improve recovery after stroke, but the structural disruption and cavitation of brain tissue that occurs creates an unfavorable environment for graft cell survival. To overcome this obstacle, scaffold materials have been used as extracellular matrix to provide structural support for the transplanted cells. Many materials could potentially be used as scaffolds for this application.Evidence AcquisitionWe performed a systematic review to determine the available evidence supporting specific scaffolds for neural progenitor cell grafting after stroke. Articles were identified with a MeSH search on PubMed. Relevant references and “related articles” of selected manuscripts were also reviewed. Full original articles published prior to May 2013 presenting unique experimental data describing intracerebral grafting of neural progenitor cells in a scaffold after cerebral infarction were included in our study. All selected articles were reviewed thoroughly by the authors for relevant data.ResultsWe found reports of use of scaffolds composed of polyglycolic acid, poly [lactic-co-glycolic acid] particles (with and without VEGF), hyaluronan-heparin-collagen hydrogel, Matrigel, collagen and extracellular matrix derived from porcine brain and urinary bladder. While multiple beneficial effects were reported, the optimal scaffold is unclear as we found no direct comparisons.ConclusionsWe conclude that multiple scaffolds appear promising for neural progenitor cell grafting after stroke, but further research is needed to optimize this neurorestorative approach. Thus, we hope to provide a basic understanding of the state of scaffolds for neural progenitor cell grafting after stroke and to encourage further research. Based on the methods of the discussed studies, we propose a standardized set of outcomes that would best be used to evaluate and compare the effectiveness of a given scaffold.

Development of oriented nanofibrous silk guide for repair of nerve defects

ABSTRACTThe aim of this study was to produce a nanofibrous biodegradable silk nerve substrate. The woven and oriented artificial scaffolds were designed by electrospinning method, and were evaluated by microscopic, mechanical analyses, and cell culture assays with Schwann cells. Results of analyses were showed a good resilience and compliance with movement as a neural graft. Cellular experiments showed a better cell adhesion and growth on the oriented nanofibrous scaffolds compared to woven nanofiber ones. This neural conduit appears to have the right organization for testing in vivo nerve tissue engineering studies.

Magnetic Particle Imaging tracks the long-term fate of in vivo neural cell implants with high image contrast.

We demonstrate that Magnetic Particle Imaging (MPI) enables monitoring of cellular grafts with high contrast, sensitivity, and quantitativeness. MPI directly detects the intense magnetization of iron-oxide tracers using low-frequency magnetic fields. MPI is safe, noninvasive and offers superb sensitivity, with great promise for clinical translation and quantitative single-cell tracking. Here we report the first MPI cell tracking study, showing 200-cell detection in vitro and in vivo monitoring of human neural graft clearance over 87 days in rat brain.

Grading Facial Nerve Function Following Combined Static and Mimetic Surgical Techniques.

Objective To present a grading scale to assess the functional recovery of the facial nerve in patients who have undergone mimetic and static surgical techniques for facial reanimation. Study design This is a proposed new facial nerve grading system that will be demonstrated with specific case presentations. All patients underwent a variety of neural grafting, microvascular free-flap reconstruction, or surgical static procedures. Results The proposed facial nerve grading scale is one that has not been described previously in the literature and is applicable to a unique patient population. Its ease of use in this patient population will allow otolaryngologists to assess facial recovery accurately and quickly in cases where the facial nerve is not anatomically intact. Conclusion The proposed facial recovery grading scale provides an efficient means of grading facial recovery for a unique group of patients who previously could not be followed. The proposed scale is practical and easy to use in a clinical setting.

Neuro-peptide treatment with Cerebrolysin improves the survival of neural stem cell grafts in an APP transgenic model of Alzheimer disease

Neural stem cells (NSCs) have been considered as potential therapy in Alzheimer's disease (AD) but their use is hampered by the poor survival of grafted cells. Supply of neurotrophic factors to the grafted cells has been proposed as a way to augment survival of the stem cells. In this context, we investigated the utility of Cerebrolysin (CBL), a peptidergic mixture with neurotrophic-like properties, as an adjunct to stem cell therapy in an APP transgenic (tg) model of AD. We grafted murine NSCs into the hippocampus of non-tg and APP tg that were treated systemically with CBL and analyzed after 1, 3, 6 and 9months post grafting. Compared to vehicle-treated non-tg mice, in the vehicle-treated APP tg mice there was considerable reduction in the survival of the grafted NSCs. Whereas, CBL treatment enhanced the survival of NSCs in both non-tg and APP tg with the majority of the surviving NSCs remaining as neuroblasts. The NSCs of the CBL treated mice displayed reduced numbers of caspase-3 and TUNEL positive cells and increased brain derived neurotrophic factor (BDNF) and furin immunoreactivity. These results suggest that CBL might protect grafted NSCs and as such be a potential adjuvant therapy when combined with grafting.

Human neural stem cell intracerebral grafts show spontaneous early neuronal differentiation after several weeks

Human neural stem cells (hNSCs) hold great promise for the treatment of neurological diseases. Considerable progress has been made to induce neural differentiation in the cell culture in vitro and upon transplantation in vivo [2] in order to explore restoration of damaged neuronal circuits. However, in vivo conventional strategies are limited to post mortem analysis. Here, we apply our developed first fate mapping platform to monitor neuronal differentiation in vivo by magnetic resonance imaging, bioluminescence imaging, and fluorescence imaging. Ferritin, Luciferase and GFP under neuronal-specific promoters for immature and mature neurons, respectively, were used to generate transgenic hNSCs. Differentiation-linked imaging reporter expression was validated in vitro. The time profile of spontaneous neuronal maturation after transplantation into mouse brain cortex demonstrated early neuronal differentiation within 6 weeks. Fully mature neurons expressing synaptogenesis were observed only after three months or longer. Our trimodal fate mapping strategy represents a unique non-invasive tool to monitor the time course of neuronal differentiation of transplanted stem cells in vivo.

Induced pluripotent stem cell-derived neural stem cell therapies for spinal cord injury.

The greatest challenge to successful treatment of spinal cord injury is the limited regenerative capacity of the central nervous system and its inability to replace lost neurons and severed axons following injury. Neural stem cell grafts derived from fetal central nervous system tissue or embryonic stem cells have shown therapeutic promise by differentiation into neurons and glia that have the potential to form functional neuronal relays across injured spinal cord segments. However, implementation of fetal-derived or embryonic stem cell-derived neural stem cell therapies for patients with spinal cord injury raises ethical concerns. Induced pluripotent stem cells can be generated from adult somatic cells and differentiated into neural stem cells suitable for therapeutic use, thereby providing an ethical source of implantable cells that can be made in an autologous fashion to avoid problems of immune rejection. This review discusses the therapeutic potential of human induced pluripotent stem cell-derived neural stem cell transplantation for treatment of spinal cord injury, as well as addressing potential mechanisms, future perspectives and challenges.

Time course of spinal doublecortin expression in developing rat and porcine spinal cord: implication in in vivo neural precursor grafting studies.

Expression of doublecortin (DCX), a 43-53 kDa microtubule binding protein, is frequently used as (i) an early neuronal marker to identify the stage of neuronal maturation of in vivo grafted neuronal precursors (NSCs), and (ii) a neuronal fate marker transiently expressed by immature neurons during development. Reliable identification of the origin of DCX-immunoreactive cells (i.e., host vs. graft) requires detailed spatial and temporal mapping of endogenous DCX expression at graft-targeted brain or spinal cord regions. Accordingly, in the present study, we analyzed (i) the time course of DCX expression in pre- and postnatal rat and porcine spinal cord, and (ii) the DCX expression in spinally grafted porcine-induced pluripotent stem cells (iPS)-derived NSCs and human embryonic stem cell (ES)-derived NSCs. In addition, complementary temporospatial GFAP expression study in porcine spinal cord was also performed. In 21-day-old rat fetuses, an intense DCX immunoreactivity distributed between the dorsal horn (DH) and ventral horn was seen and was still present in the DH neurons on postnatal day 20. In animals older than 8 weeks, no DCX immunoreactivity was seen at any spinal cord laminae. In contrast to rat, in porcine spinal cord (gestational period 113-114 days), DCX was only expressed during the pre-natal period (up to 100 days) but was no longer present in newborn piglets or in adult animals. Immunohistochemical analysis was confirmed with a comparable expression profile by western blot analysis. Contrary, the expression of porcine GFAP started within 70-80 days of the pre-natal period. Spinally grafted porcine iPS-NSCs and human ES-NSCs showed clear DCX expression at 3-4 weeks postgrafting. These data indicate that in spinal grafting studies which employ postnatal or adult porcine models, the expression of DCX can be used as a reliable marker of grafted neurons. In contrast, if grafted neurons are to be analyzed during the first 4 postnatal weeks in the rat spinal cord, additional markers or grafted cell-specific labeling techniques need to be employed to reliably identify grafted early postmitotic neurons and to differentiate the DCX expression from the neurons of the host.

A Radio-telemetric System to Monitor Cardiovascular Function in Rats with Spinal Cord Transection and Embryonic Neural Stem Cell Grafts

A Radio-telemetric System to Monitor Cardiovascular Function in Rats with Spinal Cord Transection and Embryonic Neural Stem Cell Grafts

A radio-telemetric system to monitor cardiovascular function in rats with spinal cord transection and embryonic neural stem cell grafts.

High thoracic or cervical spinal cord injury (SCI) can lead to cardiovascular dysfunction. To monitor cardiovascular parameters, we implanted a catheter connected to a radio transmitter into the femoral artery of rats that underwent a T4 spinal cord transection with or without grafting of embryonic brainstem-derived neural stem cells expressing green fluorescent protein. Compared to other methods such as cannula insertion or tail-cuff, telemetry is advantageous to continuously monitor blood pressure and heart rate in freely moving animals. It is also capable of long term multiple data acquisitions. In spinal cord injured rats, basal cardiovascular data under unrestrained condition and autonomic dysreflexia in response to colorectal distension were successfully recorded. In addition, cardiovascular parameters before and after SCI can be compared in the same rat if a transmitter is implanted before a spinal cord transection. One limitation of the described telemetry procedure is that implantation in the femoral artery may influence the blood supply to the ipsilateral hindlimb.

Survival of neural stem cell grafts in the lesioned spinal cord is enhanced by a combination of treadmill locomotor training via insulin-like growth factor-1 signaling.

Combining cell transplantation with activity-based rehabilitation is a promising therapeutic approach for spinal cord repair. The present study was designed to investigate potential interactions between the transplantation (TP) of neural stem cells (NSCs) obtained at embryonic day 14 and treadmill training (TMT) in promoting locomotor recovery and structural repair in rat contusive injury model. Combination of TMT with NSC TP at 1 week after injury synergistically improved locomotor function. We report here that combining TMT increased the survival of grafted NSCs by >3-fold and >5-fold at 3 and 9 weeks after injury, respectively. The number of surviving NSCs was significantly correlated with the extent of locomotor recovery. NSCs grafted into the injured spinal cord were under cellular stresses induced by reactive nitrogen or oxygen species, which were markedly attenuated by TMT. TMT increased the concentration of insulin-like growth factor-1 (IGF-1) in the CSF. Intrathecal infusion of neutralizing IGF-1 antibodies, but not antibodies against either BDNF or Neurotrophin-3 (NT-3), abolished the enhanced survival of NSC grafts by TMT. The combination of TP and TMT also resulted in tissue sparing, increased myelination, and restoration of serotonergic fiber innervation to the lumbar spinal cord to a larger extent than that induced by either TP or TMT alone. Therefore, we have discovered unanticipated beneficial effects of TMT in modulating the survival of grafted NSCs via IGF-1. Our study identifies a novel neurobiological basis for complementing NSC-based spinal cord repair with activity-based neurorehabilitative approaches.

The potential of alternate sources of cells for neural grafting in Parkinson's and Huntington's disease.

Cell-based therapies for Parkinson's and Huntington's disease have provided mixed clinical outcomes and one of the reasons underlying this is the use of primary fetal tissue as the source of grafted cells. An alternate source of cells, such as stem cells, could overcome many of the issues associated with primary fetal tissue and would help bring forward cell replacement therapy as a reliable and effective treatment for these two neurodegenerative disorders. This review will discuss which stem cells are likely to go to clinic in the next generation of cells, based on trials for Parkinson's and Huntington's disease.

Survival and Integration of Neurons Derived from Human Embryonic Stem Cells in MPTP-Lesioned Primates

A human embryonic stem cell (HESC) line, H1, was studied after differentiation to a dopaminergic phenotype in vitro in order to carry out in vivo studies in Parkinsonian monkeys. To identify morphological characteristics of transplanted donor cells, HESCs were transfected with a GFP lentiviral vector. Gene expression studies were performed at each step of a neural rosette-based dopaminergic differentiation protocol by RT-PCR. In vitro immunofluorescence revealed that >90% of the differentiated cells exhibited a neuronal phenotype by β-III-tubulin immunocytochemistry, with 17% of the cells coexpressing tyrosine hydroxylase prior to implantation. Biochemical analyses demonstrated dopamine release in culture in response to potassium chloride-induced membrane depolarization, suggesting that the cells synthesized and released dopamine. These characterized, HESC-derived neurons were then implanted into the striatum and midbrain of MPTP (1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine)-exposed monkeys that were triple immunosuppressed. Here we demonstrate robust survival of transplanted HESC-derived neurons after 6 weeks, as well as morphological features consistent with polarization, organization, and extension of processes that integrated into the host striatum. Expression of the dopaminergic marker tyrosine hydroxylase was not maintained in HESC-derived neural grafts in either the striatum or substantia nigra, despite a neuronal morphology and expression of β-III-tubulin. These results suggest that dopamine neuronal cells derived from neuroectoderm in vitro will not maintain the correct midbrain phenotype in vivo in nonhuman primates, contrasted with recent studies showing dopamine neuronal survival using an alternative floorplate method.

Promotion of Survival and Differentiation of Neural Stem Cells with Fibrin and Growth Factor Cocktails after Severe Spinal Cord Injury

Neural stem cells (NSCs) can self-renew and differentiate into neurons and glia. Transplanted NSCs can replace lost neurons and glia after spinal cord injury (SCI), and can form functional relays to re-connect spinal cord segments above and below a lesion. Previous studies grafting neural stem cells have been limited by incomplete graft survival within the spinal cord lesion cavity. Further, tracking of graft cell survival, differentiation, and process extension had not been optimized. Finally, in previous studies, cultured rat NSCs were typically reported to differentiate into glia when grafted to the injured spinal cord, rather than neurons, unless fate was driven to a specific cell type. To address these issues, we developed new methods to improve the survival, integration and differentiation of NSCs to sites of even severe SCI. NSCs were freshly isolated from embryonic day 14 spinal cord (E14) from a stable transgenic Fischer 344 rat line expressing green fluorescent protein (GFP) and were embedded into a fibrin matrix containing growth factors; this formulation aimed to retain grafted cells in the lesion cavity and support cell survival. NSCs in the fibrin/growth factor cocktail were implanted two weeks after thoracic level-3 (T3) complete spinal cord transections, thereby avoiding peak periods of inflammation. Resulting grafts completely filled the lesion cavity and differentiated into both neurons, which extended axons into the host spinal cord over remarkably long distances, and glia. Grafts of cultured human NSCs expressing GFP resulted in similar findings. Thus, methods are defined for improving neural stem cell grafting, survival and analysis of in vivo findings.

Promotion of survival and differentiation of neural stem cells with fibrin and growth factor cocktails after severe spinal cord injury.

Neural stem cells (NSCs) can self-renew and differentiate into neurons and glia. Transplanted NSCs can replace lost neurons and glia after spinal cord injury (SCI), and can form functional relays to re-connect spinal cord segments above and below a lesion. Previous studies grafting neural stem cells have been limited by incomplete graft survival within the spinal cord lesion cavity. Further, tracking of graft cell survival, differentiation, and process extension had not been optimized. Finally, in previous studies, cultured rat NSCs were typically reported to differentiate into glia when grafted to the injured spinal cord, rather than neurons, unless fate was driven to a specific cell type. To address these issues, we developed new methods to improve the survival, integration and differentiation of NSCs to sites of even severe SCI. NSCs were freshly isolated from embryonic day 14 spinal cord (E14) from a stable transgenic Fischer 344 rat line expressing green fluorescent protein (GFP) and were embedded into a fibrin matrix containing growth factors; this formulation aimed to retain grafted cells in the lesion cavity and support cell survival. NSCs in the fibrin/growth factor cocktail were implanted two weeks after thoracic level-3 (T3) complete spinal cord transections, thereby avoiding peak periods of inflammation. Resulting grafts completely filled the lesion cavity and differentiated into both neurons, which extended axons into the host spinal cord over remarkably long distances, and glia. Grafts of cultured human NSCs expressing GFP resulted in similar findings. Thus, methods are defined for improving neural stem cell grafting, survival and analysis of in vivo findings.

Neurodegenerative disorders: the Glia way forward.

The realization that inflammation can affect the brain is not a new one, and many diseases of the CNS, such as multiple sclerosis (MS), have been shown to clearly respond to agents that target the immune system at one level or another. However, it is only more recently that the immune system has been shown to play a role in the normal development and homeostasis of the brain as well as contributing to disorders that have traditionally been thought of as being purely neurodegenerative in nature, such as Huntington's (HD) or Alzheimer's disease (AD). In this special issue of Frontiers in Neuropharmacology, we have sought to bring together experts in this new emerging area of neurobiology. The best place to start in this special issue is with the paper by McGeer and McGeer (2011) as they lay out the history of the field and the skepticism that it has generated en route, and which still exists today. Indeed, many neurologists and neurobiologists still argue that any inflammatory or glial response in neurodegenerative disorders is simply a secondary phenomenon of no pathogenic or therapeutic relevance. However, evidence has accumulated in favor of it having a role and part of this relates to our ability to better image the microglial responses in patients with neurodegenerative disorders of the brain and Politis et al. (2012) explore this in their review on PET and TSPO radioligands. A number of our papers summarize the role of microglia in ongoing CNS activities. Ekdahl (2012), for example, discusses how microglia may regulate adult neurogenesis in the healthy and diseased brain possibly through direct synaptic contacts. This is taken on by Streit and Xue (2012) who put forward the theory that the loss of the normal neuroprotective function of microglial, as a result of aging, leads to disease states, especially AD. Neher et al. (2012), on the other hand, discuss how microglia can directly phagocytose apparently healthy neurons as well as those in the diseased brain and by so doing are primary players in the cell loss seen in neurodegenerative disorders. This is explored in more detail by Phani et al. (2012) in Amyotrophic Lateral Sclerosis (ALS); Solito and Sastre (2012) in AD; and Huang and Halliday (2012) for Parkinson's disease (PD). Finally in the first of our two reviews, we discuss how the astrocytic and microglial responses are different in a range of new experimental therapies for neurodegenerative disorders. These therapies include chronic deep brain stimulation, which induces a variable astro- and microglial response and in some cases even a collagenous band at the electrode tip. In contrast, growth factor infusions and gene therapies produce much less of a glial response whilst neural grafts vary in the intensity of response they provoke, in part as a function of disease state. The significance of these different responses (the type and magnitude) remains unknown, but what is emerging from these studies is the complex interplay that exists between glial cells and neurons and how astrocytes, in particular, can influence the activity of large neural and blood networks (Cicchetti and Barker, 2014). These new observations will likely help explain the variance seen in clinical trials using these agents in a range of neurodegenerative disorders. In our second review we summarize the major findings of the papers that make up this special edition and how we can build on this work as we move forward into a new therapeutic era, which includes the use of a whole new range of immune modulating therapies (Barker and Cicchetti, 2012).

Efficient Specification of Interneurons from Human Pluripotent Stem Cells by Dorsoventral and Rostrocaudal Modulation

GABAergic interneurons regulate cortical neural networks by providing inhibitory inputs, and their malfunction, resulting in failure to intricately regulate neural circuit balance, is implicated in brain diseases such as Schizophrenia, Autism, and Epilepsy. During early development, GABAergic interneuron progenitors arise from the ventral telencephalic area such as medial ganglionic eminence (MGE) and caudal ganglionic eminence (CGE) by the actions of secreted signaling molecules from nearby organizers, and migrate to their target sites where they form local synaptic connections. In this study, using combinatorial and temporal modulation of developmentally relevant dorsoventral and rostrocaudal signaling pathways (SHH, Wnt, and FGF8), we efficiently generated MGE cells from multiple human pluripotent stem cells. Most importantly, modulation of FGF8/FGF19 signaling efficiently directed MGE versus CGE differentiation. Human MGE cells spontaneously differentiated into Lhx6-expressing GABAergic interneurons and showed migratory properties. These human MGE-derived neurons generated GABA, fired action potentials, and displayed robust GABAergic postsynaptic activity. Transplantation into rodent brains results in well-contained neural grafts enriched with GABAergic interneurons that migrate in the host and mature to express somatostatin or parvalbumin. Thus, we propose that signaling modulation recapitulating normal developmental patterns efficiently generate human GABAergic interneurons. This strategy represents a novel tool in regenerative medicine, developmental studies, disease modeling, bioassay, and drug screening.

Design of Oriented Porous PHBV Scaffold as a Neural Guide

The aim of this study was to produce an oriented biodegradable poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nerve guide. Oriented porous micropatterned artificial nerve guide designed onto the micro-patterned silicon wafers, then their surfaces modified with to oxygen plasma for cell attachment increasing. Afterwards, the neural guides were evaluated by microscopic, structural, physical, and mechanical analyses, and cell culture assays with Schwann cells. Results of structural, physical, and mechanical analyses showed a good resilience and compliance with movement as a neural graft. Cellular experiments showed a better cell adhesion, growth, and proliferation inside the plasma-modified neural guides compared to un-modified ones, also Schwann cells were well attached on plasma-modified surface. This neural guide appears to have the right organization for testing in vivo nerve tissue engineering studies.

Notch Signaling-Mediated Neural Lineage Selection Facilitates Intrastriatal Transplantation Therapy for Ischemic Stroke by Promoting Endogenous Regeneration in the Hippocampus

Acquisition of highly efficient neural differentiation based on understanding of initial lineage commitment of human embryonic stem (hES) cells remains a challenge. This study describes a simple three-stage protocol to induce hES cells into neural lineage cells using a 2-week coculture with murine bone marrow stromal cell (BMSC) PA6 followed by a 2-week propagation culture in PA6-conditioned medium and an additional 2-week selection culture in chemically defined neurobasal medium. This protocol generated a relatively high yield of neural lineage cells without mesodermal and endodermal lineage cell contamination. Notably, we demonstrated that PA6 coculture can significantly enhance the expression level of Notch signaling components and promote neural lineage entry of hES cell derivatives. Manipulation of Notch signaling can boost or suppress neural differentiation of hES cell derivatives, suggesting that Notch signaling may underlie the PA6-mediated neural induction. In vivo studies demonstrated that derived neural cells could improve the cognitive function of ischemic stroke rats. Intrastriatal human neural cell grafts were noted to migrate to damaged cerebral regions, enhance basic fibroblast growth factor production in the hippocampus, and restore the pyramidal neuron density and morphology in the hippocampal CA1 region, although only a small number of human donor cells were present in the hippocampus, suggesting that donor cells can boost hippocampal reconstruction by promoting the endogenous regeneration process. These findings demonstrate a pivotal role for Notch in hES cell fate determination and that manipulation of Notch signaling is therefore likely to be a key factor in taking command of hES cell lineage choice. This study suggested the potential of utilizing PA6 coculture to imitate the embryonic niche for hES cell neural induction via Notch signaling and a high application potential of BMSC-involved protocol, which can yield a whole lineage of human neural cells to promote endogenous regeneration in the hippocampus upon transplantation for potential therapy of ischemic stroke.

Review: The future of cell therapies and brain repair: Parkinson's disease leads the way

During the past 40 years brain tissue grafting techniques have been used both to study fundamental neurobiological questions and to treat neurological diseases. Motor symptoms of Parkinson's disease are largely due to degeneration of midbrain dopamine neurones. Because the nigrostriatal pathology is relatively focused anatomically, Parkinson's disease is considered the ideal candidate for brain repair by neural grafting and dopamine neurone transplantation for it has led the way in the neural transplantation research field. In this mini-review, we briefly highlight four important areas of development. First, we describe marked functional benefits up to 18 years after transplantation surgery in patients with Parkinson's disease. This is proof-of-principle that, using optimal techniques and patient selection, grafted dopamine neurones can work in humans and the duration of the benefit exceeds placebo effects associated with surgery. Second, we describe that eventually protein aggregates containing α-synuclein, identical to Lewy bodies, develop inside foetal dopamine neurones transplanted to patients with Parkinson's disease. This gives clues about pathogenetic mechanisms operating in Parkinson's disease, and also raises the question whether neural graft function will eventually decline as the result of the disease process. Third, we describe new emerging sources of transplantable dopamine neurones derived from pluripotent stem cells or reprogrammed adult somatic cells. Fourth, we highlight an important European Union-funded multicentre clinical trial involving transplantation of foetal dopamine neurones in Parkinson's disease. We describe the design of this ongoing trial and how it can impact on the overall future of cell therapy in Parkinson's disease.