Oliver Cooper

Parkinson's Disease Patient-Derived Induced Pluripotent Stem Cells Free of Viral Reprogramming Factors

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients represent a powerful tool for biomedical research and may provide a source for replacement therapies. However, the use of viruses encoding the reprogramming factors represents a major limitation of the current technology since even low vector expression may alter the differentiation potential of the iPSCs or induce malignant transformation. Here, we show that fibroblasts from five patients with idiopathic Parkinsons disease can be efficiently reprogrammed and subsequently differentiated into dopaminergic neurons. Moreover, we derived hiPSCs free of reprogramming factors using Cre-recombinase excisable viruses. Factor-free hiPSCs maintain a pluripotent state and show a global gene expression profile, more closely related to hESCs than to hiPSCs carrying the transgenes. Our results indicate that residual transgene expression in virus-carrying hiPSCs can affect their molecular characteristics and that factor-free hiPSCs therefore represent a more suitable source of cells for modeling of human disease.

Differentiated Parkinson patient-derived induced pluripotent stem cells grow in the adult rodent brain and reduce motor asymmetry in Parkinsonian rats

Recent advances in deriving induced pluripotent stem (iPS) cells from patients offer new possibilities for biomedical research and clinical applications, as these cells could be used for autologous transplantation. We differentiated iPS cells from patients with Parkinsons disease (PD) into dopaminergic (DA) neurons and show that these DA neurons can be transplanted without signs of neurodegeneration into the adult rodent striatum. The PD patient iPS (PDiPS) cell-derived DA neurons survived at high numbers, showed arborization, and mediated functional effects in an animal model of PD as determined by reduction of amphetamine- and apomorphine-induced rotational asymmetry, but only a few DA neurons projected into the host striatum at 16 wk after transplantation. We next applied FACS for the neural cell adhesion molecule NCAM on differentiated PDiPS cells before transplantation, which resulted in surviving DA neurons with functional effects on amphetamine-induced rotational asymmetry in a 6-OHDA animal model of PD. Morphologically, we found that PDiPS cell-derived non-DA neurons send axons along white matter tracts into specific close and remote gray matter target areas in the adult brain. Such findings establish the transplantation of human PDiPS cell-derived neurons as a long-term in vivo method to analyze potential disease-related changes in a physiological context. Our data also demonstrate proof of principle of survival and functional effects of PDiPS cell-derived DA neurons in an animal model of PD and encourage further development of differentiation protocols to enhance growth and function of implanted PDiPS cell-derived DA neurons in regard to potential therapeutic applications.

Pharmacological Rescue of Mitochondrial Deficits in iPSC-Derived Neural Cells from Patients with Familial Parkinson’s Disease

Neural cells derived from induced pluripotent stem cells from patients with genetic forms of Parkinson’s disease provide insights into disease pathogenesis. Understanding Mitochondrial Deficits in Parkinson’s Disease Parkinson’s disease (PD) is a common, progressive neurodegenerative disease characterized by loss of dopaminergic neurons in the nigrostriatal pathway of the brain, resulting in motor and cognitive deficits. Rodent and primate models only partially predict disease mechanisms. In a new study, Cooper et al. set out to make a human cellular model of PD. First, the authors obtained fibroblasts from members of families with genetically defined forms of PD and generated induced pluripotent stem cells (iPSCs) from the fibroblasts. They then induced differentiation of these PD patient–derived iPSCs into neural cells including dopaminergic neurons to study how the genetic mutations influenced the responses of neural cells to various cellular stressors. Mitochondrial dysfunction has already been implicated in the pathogenesis of PD, so the authors decided to treat their iPSC-derived neural cells from patients with rare familial forms of PD with chemical stressors and toxins known to disrupt mitochondrial function. The researchers observed a gradual increase in sensitivity to cellular stress as the cell type analyzed became functionally closer to the vulnerable cell types in the PD brain; that is, fibroblasts taken directly from PD patients were less sensitive to the chemical stressors than iPSC-derived neural cells. Several drugs helped iPSC-derived neural cells to resist the damaging effects of the cellular stressors. These studies with human neural cells from iPSCs from patients with familial PD highlight opportunities to characterize disease pathways and to screen for new therapeutic agents. Parkinson’s disease (PD) is a common neurodegenerative disorder caused by genetic and environmental factors that results in degeneration of the nigrostriatal dopaminergic pathway in the brain. We analyzed neural cells generated from induced pluripotent stem cells (iPSCs) derived from PD patients and presymptomatic individuals carrying mutations in the PINK1 (PTEN-induced putative kinase 1) and LRRK2 (leucine-rich repeat kinase 2) genes, and compared them to those of healthy control subjects. We measured several aspects of mitochondrial responses in the iPSC-derived neural cells including production of reactive oxygen species, mitochondrial respiration, proton leakage, and intraneuronal movement of mitochondria. Cellular vulnerability associated with mitochondrial dysfunction in iPSC-derived neural cells from familial PD patients and at-risk individuals could be rescued with coenzyme Q10, rapamycin, or the LRRK2 kinase inhibitor GW5074. Analysis of mitochondrial responses in iPSC-derived neural cells from PD patients carrying different mutations provides insight into convergence of cellular disease mechanisms between different familial forms of PD and highlights the importance of oxidative stress and mitochondrial dysfunction in this neurodegenerative disease.

Selective COX-2 inhibition prevents progressive dopamine neuron degeneration in a rat model of Parkinson's disease

Several lines of evidence point to a significant role of neuroinflammation in Parkinsons disease (PD) and other neurodegenerative disorders. In the present study we examined the protective effect of celecoxib, a selective inhibitor of the inducible form of cyclooxygenase (COX-2), on dopamine (DA) cell loss in a rat model of PD. We used the intrastriatal administration of 6-hydroxydopamine (6-OHDA) that induces a retrograde neuronal damage and death, which progresses over weeks. Animals were randomized to receive celecoxib (20 mg/kg/day) or vehicle starting 1 hour before the intrastriatal administration of 6-OHDA. Evaluation was performed in vivo using micro PET and selective radiotracers for DA terminals and microglia. Post mortem analysis included stereological quantification of tyrosine hydroxylase, astrocytes and microglia. 12 days after the 6-OHDA lesion there were no differences in DA cell or fiber loss between groups, although the microglial cell density and activation was markedly reduced in animals receiving celecoxib (p < 0.01). COX-2 inhibition did not reduce the typical astroglial response in the striatum at any stage. Between 12 and 21 days, there was a significant progression of DA cell loss in the vehicle group (from 40 to 65%) that was prevented by celecoxib. Therefore, inhibition of COX-2 by celecoxib appears to be able, either directly or through inhibition of microglia activation to prevent or slow down DA cell degeneration.

Intrastriatal Transforming Growth Factor α Delivery to a Model of Parkinson's Disease Induces Proliferation and Migration of Endogenous Adult Neural Progenitor Cells without Differentiation into Dopaminergic Neurons

We examined the cell proliferative, neurogenic, and behavioral effects of transforming growth factor α (TGFα) in a 6-OHDA Parkinsons disease model when compared with naive rats. Intrastriatal TGFα infusion induced significant proliferation, hyperplastic nodules, and substantial migratory waves of nestin-positive progenitor cells from the adult subventricular zone (SVZ) of dopamine-denervated rats. Interestingly, SVZ cells in naive rats displayed proliferation but minimal migration in response to the TGFα infusion. The cells in the expanded SVZ accumulated cytoplasmic β-catenin, indicating activation of classical Wnt signaling. However, no evidence of any neuronal differentiation was found of these recruited progenitor cells anywhere examined in the brain. Consequently, no evidence of dopaminergic (DA) neurogenesis was found in the striatum or substantia nigra in any experimental group, and amphetamine-induced behavioral rotations did not improve. In summary, the cells in the TGFα-induced migratory cellular wave remain undifferentiated and do not differentiate into midbrain-like DA neurons.

Differentiation of human ES and Parkinson's disease iPS cells into ventral midbrain dopaminergic neurons requires a high activity form of SHH, FGF8a and specific regionalization by retinoic acid.

The cardinal motor symptoms of Parkinsons disease (PD) are caused by the vulnerability to dysfunction and degeneration of ventral midbrain (VM) dopaminergic (DA) neurons. A major limitation for experimental studies of current ES/iPS cell differentiation protocols is the lack of VM DA neurons with a stable phenotype as defined by an expression marker code of FOXA2/TH/β-tubulin. Here we demonstrate a combination of three modifications that were required to produce VM DA neurons. Firstly, early and specific exposure to 10(-)(8)M (low dose) retinoic acid improved the regional identity of neural progenitor cells derived from human ES cells, PD or healthy subject-specific iPS cells. Secondly, a high activity form of human sonic hedgehog established a sizeable FOXA2(+) neural progenitor cell population in vitro. Thirdly, early exposure to FGF8a, rather than Fgf8b, and WNT1 was required for robust differentiation of the FOXA2(+) floor plate-like human neural progenitor cells into FOXA2(+) DA neurons. FOXA2(+) DA neurons were also generated when this protocol was adapted to feeder-free conditions. In summary, this new human ES and iPS cell differentiation protocol using FGF8a, WNT1, low dose retinoic acid and a high activity form of SHH can generate human VM DA neurons that are required for relevant new bioassays, drug discovery and cell based therapies for PD.

Successful Function of Autologous iPSC-Derived Dopamine Neurons following Transplantation in a Non-Human Primate Model of Parkinson’s Disease

Autologous transplantation of patient-specific induced pluripotent stem cell (iPSC)-derived neurons is a potential clinical approach for treatment of neurological disease. Preclinical demonstration of long-term efficacy, feasibility, and safety of iPSC-derived dopamine neurons in non-human primate models will be an important step in clinical development of cell therapy. Here, we analyzed cynomolgus monkey (CM) iPSC-derived midbrain dopamine neurons for up to 2 years following autologous transplantation in a Parkinsons disease (PD) model. In one animal, with the most successful protocol, we found that unilateral engraftment of CM-iPSCs could provide a gradual onset of functional motor improvement contralateral to the side of dopamine neuron transplantation, and increased motor activity, without a need for immunosuppression. Postmortem analyses demonstrated robust survival of midbrain-like dopaminergic neurons and extensive outgrowth into the transplanted putamen. Our proof of concept findings support further development of autologous iPSC-derived cell transplantation for treatment of PD.

Improved cell therapy protocols for Parkinson's disease based on differentiation efficiency and safety of hESC-, hiPSC-, and non-human primate iPSC-derived dopaminergic neurons

The main motor symptoms of Parkinsons disease are due to the loss of dopaminergic (DA) neurons in the ventral midbrain (VM). For the future treatment of Parkinsons disease with cell transplantation it is important to develop efficient differentiation methods for production of human iPSCs and hESCs‐derived midbrain‐type DA neurons. Here we describe an efficient differentiation and sorting strategy for DA neurons from both human ES/iPS cells and non‐human primate iPSCs. The use of non‐human primate iPSCs for neuronal differentiation and autologous transplantation is important for preclinical evaluation of safety and efficacy of stem cell‐derived DA neurons. The aim of this study was to improve the safety of human‐ and non‐human primate iPSC (PiPSC)‐derived DA neurons. According to our results, NCAM+/CD29low sorting enriched VM DA neurons from pluripotent stem cell‐derived neural cell populations. NCAM+/CD29low DA neurons were positive for FOXA2/TH and EN1/TH and this cell population had increased expression levels of FOXA2, LMX1A, TH, GIRK2, PITX3, EN1, NURR1 mRNA compared to unsorted neural cell populations. PiPSC‐derived NCAM+/CD29low DA neurons were able to restore motor function of 6‐hydroxydopamine (6‐OHDA) lesioned rats 16 weeks after transplantation. The transplanted sorted cells also integrated in the rodent brain tissue, with robust TH+/hNCAM+ neuritic innervation of the host striatum. One year after autologous transplantation, the primate iPSC‐derived neural cells survived in the striatum of one primate without any immunosuppression. These neural cell grafts contained FOXA2/TH‐positive neurons in the graft site. This is an important proof of concept for the feasibility and safety of iPSC‐derived cell transplantation therapies in the future. STEM Cells 2013;31:1548–1562

LRRK2 mutations cause mitochondrial DNA damage in iPSC-derived neural cells from Parkinson's disease patients: reversal by gene correction.

Parkinsons disease associated mutations in leucine rich repeat kinase 2 (LRRK2) impair mitochondrial function and increase the vulnerability of induced pluripotent stem cell (iPSC)-derived neural cells from patients to oxidative stress. Since mitochondrial DNA (mtDNA) damage can compromise mitochondrial function, we examined whether LRRK2 mutations can induce damage to the mitochondrial genome. We found greater levels of mtDNA damage in iPSC-derived neural cells from patients carrying homozygous or heterozygous LRRK2 G2019S mutations, or at-risk individuals carrying the heterozygous LRRK2 R1441C mutation, than in cells from unrelated healthy subjects who do not carry LRRK2 mutations. After zinc finger nuclease-mediated repair of the LRRK2 G2019S mutation in iPSCs, mtDNA damage was no longer detected in differentiated neuroprogenitor and neural cells. Our results unambiguously link LRRK2 mutations to mtDNA damage and validate a new cellular phenotype that can be used for examining pathogenic mechanisms and screening therapeutic strategies.

Fate Mapping and Lineage Analyses Demonstrate the Production of a Large Number of Striatal Neuroblasts After Transforming Growth Factor α and Noggin Striatal Infusions into the Dopamine‐Depleted Striatum

Infusion of transforming growth factor α (TGFα) into the adult dopamine (DA)‐depleted striatum generates a local population of nestin+/proliferating cell nuclear antigen (PCNA)+ newborn cells. The precise origin and fate of these new striatal cells are unknown, making it difficult to direct them for neural repair in Parkinsons disease. Experiments in rats using 5‐bromo‐2′‐deoxyuridine (BrdU) to label neural progenitor cells showed that during TGFα infusion in the DA‐depleted striatum, newborn striatal cells formed a homogeneous population of precursors, with the majority coexpressing nestin, Mash1, Olig2, and epidermal growth factor receptor, consistent with the phenotype of multipotent C cells. Upon TGFα pump withdrawal, the subventricular zone (SVZ) was repopulated by neuroblasts. Strikingly, during this period, numerous clusters of doublecortin+/polysialylated neuronal cell adhesion molecule+ neuroblasts were also produced in the ipsilateral medial striatum. In parallel, striatal BrdU+/glial fibrillary acidic protein+ astrocytes were generated, but no BrdU+/O4+/CNPase+ oligodendrocytes were generated. Infusion of the neuralizing bone morphogenetic protein antagonist noggin after TGFα pump withdrawal increased the neuroblast‐to‐astrocyte ratio among new striatal cells by blocking glial differentiation but did not alter striatal neurogenesis. At no time or treatment condition were differentiated neurons generated, including DA neurons. Using 6‐hydroxydopamine‐lesioned nestin‐CreERT2/R26R‐YFP mice that allow genetic fate‐mapping of SVZ nestin+ cells, we show that TGFα‐generated striatal cells originate from SVZ nestin+ precursors that confirmed data from the rats on the phenotype and fate of striatal nestin+/PCNA+ cells upon TGFα withdrawal. This work demonstrates that a large population of multipotent striatal C‐like cells can be generated in the DA‐depleted striatum that do not spontaneously differentiate into DA neurons.