Mutations in the acid β-glucocerebrosidase (GBA1) gene, responsible for the lysosomal storage disorder Gaucher's disease (GD), are the strongest genetic risk factor for Parkinson's disease (PD) known to date. Here we generate induced pluripotent stem cells from subjects with GD and PD harbouring GBA1 mutations, and differentiate them into midbrain dopaminergic neurons followed by enrichment using fluorescence-activated cell sorting. Neurons show a reduction in glucocerebrosidase activity and protein levels, increase in glucosylceramide and α-synuclein levels as well as autophagic and lysosomal defects. Quantitative proteomic profiling reveals an increase of the neuronal calcium-binding protein 2 (NECAB2) in diseased neurons. Mutant neurons show a dysregulation of calcium homeostasis and increased vulnerability to stress responses involving elevation of cytosolic calcium. Importantly, correction of the mutations rescues such pathological phenotypes. These findings provide evidence for a link between GBA1 mutations and complex changes in the autophagic/lysosomal system and intracellular calcium homeostasis, which underlie vulnerability to neurodegeneration.

Parkinson's disease (PD) is a common neurodegenerative disease caused by genetic and environmental factors. We analyzed induced pluripotent stem cell (iPSC)-derived neural cells from PD patients and presymptomatic individuals carrying mutations in the PINK1 and LRRK2 genes, and 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 function in iPSC-derived neural cells from 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 insights into convergence of cellular disease mechanisms between different familial forms of PD and highlights the importance of oxidative stress and mitochondrial dysfunction in PD.

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 Parkinson's 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) cellderived 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 cellderived DA neurons in regard to potential therapeutic applications.

Endogenous neural stem/precursor cells (NPCs) are considered a functional reservoir for promoting tissue homeostasis and repair after injury, therefore regenerative strategies that mobilize these cells have recently been proposed. Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke), the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized. Here we show that persistent brain inflammation, induced by immune cells targeting myelin, extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche. In parallel, we demonstrate a quantitative reduction of the putative brain stem cells proliferation in the SVZ during persistent brain inflammation, which is completely reversed after in vitro culture of the isolated NPCs. Together, these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders.

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Summary Autologous transplantation of patient-specific 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 Parkinson's 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. Post-mortem 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.

While mitochondrial dysfunction is emerging as key in Parkinson's disease (PD), a central question remains whether mitochondria are actual disease drivers and whether boosting mitochondrial biogenesis and function ameliorates pathology. We address these questions using patient-derived induced pluripotent stem cells and Drosophila models of GBA-related PD (GBA-PD), the most common PD genetic risk. Patient neurons display stress responses, mitochondrial demise, and changes in NAD+ metabolism. NAD+ precursors have been proposed to ameliorate age-related metabolic decline and disease. We report that increasing NAD+ via the NAD+ precursor nicotinamide riboside (NR) significantly ameliorates mitochondrial function in patient neurons. Human neurons require nicotinamide phosphoribosyltransferase (NAMPT) to maintain the NAD+ pool and utilize NRK1 to synthesize NAD+ from NAD+ precursors. Remarkably, NR prevents the age-related dopaminergic neuronal loss and motor decline in fly models of GBA-PD. Our findings suggest NR as a viable clinical avenue for neuroprotection in PD and other neurodegenerative diseases.

As we age, the immune system undergoes a process of senescence accompanied by the increased production of proinflammatory cytokines, a chronic subclinical condition named as “inflammaging”. Emerging evidence from human and experimental models suggest that immune senescence also affects the central nervous system and promotes neuronal dysfunction, especially within susceptible neuronal populations. In this review we discuss the potential role of immune aging, inflammation and metabolic derangement in neurological diseases. The discovery of novel therapeutic strategies targeting age-linked inflammation may promote healthy brain aging and the treatment of neurodegenerative as well as neuropsychiatric disorders.