In Vivo Phenotyping of Familial Parkinson’s Disease with Human Induced Pluripotent Stem Cells: A Proof-of-Concept Study

Challenges involved in cell therapy for Parkinson's disease using human pluripotent stem cells

Neurons derived from human pluripotent stem cells (hPSCs) provide a valuable tool for studying human neural development and neurodegenerative diseases. The investigation of hPSC-based cell therapy, involving the differentiation of hPSCs into target cells and their transplantation into affected regions, is of particular interest. One neurodegenerative disease that is being extensively studied for hPSC-based cell therapy is Parkinson's disease (PD), the second most common among humans. Various research groups are focused on differentiating hPSCs into ventral midbrain dopaminergic (vmDA) progenitors, which have the potential to further differentiate into neurons closely resembling DA neurons found in the substantia nigra pars compacta (SNpc) after transplantation, providing a promising treatment option for PD. In vivo experiments, where hPSC-derived vmDA progenitor cells were transplanted into the striatum or SNpc of animal PD models, the transplanted cells demonstrated stable engraftment and resulted in behavioral recovery in the transplanted animals. Several differentiation protocols have been developed for this specific cell therapy. However, the lack of a reliable live-cell lineage identification method presents a significant obstacle in confirming the precise lineage of the differentiated cells intended for transplantation, as well as identifying potential contamination by non-vmDA progenitors. This deficiency increases the risk of adverse effects such as dyskinesias and tumorigenicity, highlighting the importance of addressing this issue before proceeding with transplantation. Ensuring the differentiation of hPSCs into the target cell lineage is a crucial step to guarantee precise therapeutic effects in cell therapy. To underscore the significance of lineage identification, this review focuses on the differentiation protocols of hPSC-derived vmDA progenitors developed by various research groups for PD treatment. Moreover, in vivo experimental results following transplantation were carefully analyzed. The encouraging outcomes from these experiments demonstrate the potential efficacy and safety of hPSC-derived vmDA progenitors for PD cell therapy. Additionally, the results of clinical trials involving the use of hPSC-derived vmDA progenitors for PD treatment were briefly reviewed, shedding light on the progress and challenges faced in translating this promising therapy into clinical practice.

Recent Advances in High-Content Imaging and Analysis in iPSC-Based Modelling of Neurodegenerative Diseases

In the field of neurodegenerative pathologies, the platforms for disease modelling based on patient-derived induced pluripotent stem cells (iPSCs) represent a valuable molecular diagnostic/prognostic tool. Indeed, they paved the way for the in vitro recapitulation of the pathological mechanisms underlying neurodegeneration and for characterizing the molecular heterogeneity of disease manifestations, also enabling drug screening approaches for new therapeutic candidates. A major challenge is related to the choice and optimization of the morpho-functional study designs in human iPSC-derived neurons to deeply detail the cell phenotypes as markers of neurodegeneration. In recent years, the specific combination of high-throughput screening with subcellular resolution microscopy for cell-based high-content imaging (HCI) screening allowed in-depth analyses of cell morphology and neurite trafficking in iPSC-derived neuronal cells by using specific cutting-edge microscopes and automated computational assays. The present work aims to describe the main recent protocols and advances achieved with the HCI analysis in iPSC-based modelling of neurodegenerative diseases, highlighting technical and bioinformatics tips and tricks for further uses and research. To this end, microscopy requirements and the latest computational pipelines to analyze imaging data will be explored, while also providing an overview of the available open-source high-throughput automated platforms.

High content screening and proteomic analysis identify a kinase inhibitor that rescues pathological phenotypes in a patient-derived model of Parkinson's disease

Combining high throughput screening approaches with induced pluripotent stem cell (iPSC)-based disease modeling represents a promising unbiased strategy to identify therapies for neurodegenerative disorders. Here we applied high content imaging on iPSC-derived neurons from patients with familial Parkinson’s disease bearing the G209A (p.A53T) α-synuclein (αSyn) mutation and launched a screening campaign on a small kinase inhibitor library. We thus identified the multi-kinase inhibitor BX795 that at a single dose effectively restores disease-associated neurodegenerative phenotypes. Proteomics profiling mapped the molecular pathways underlying the protective effects of BX795, comprising a cohort of 118 protein-mediators of the core biological processes of RNA metabolism, protein synthesis, modification and clearance, and stress response, all linked to the mTORC1 signaling hub. In agreement, expression of human p.A53T-αSyn in neuronal cells affected key components of the mTORC1 pathway resulting in aberrant protein synthesis that was restored in the presence of BX795 with concurrent facilitation of autophagy. Taken together, we have identified a promising small molecule with neuroprotective actions as candidate therapeutic for PD and other protein conformational disorders.

α-synuclein pathogenesis in hiPSC models of Parkinson's disease

α-synuclein is an increasingly prominent player in the pathology of a variety of neurodegenerative conditions. Parkinson’s disease (PD) is a neurodegenerative disorder that affects mainly the dopaminergic (DA) neurons in the substantia nigra of the brain. Typical of PD pathology is the finding of protein aggregations termed ‘Lewy bodies’ in the brain regions affected. α-synuclein is implicated in many disease states including dementia with Lewy bodies (DLB) and Alzheimer’s disease. However, PD is the most common synucleinopathy and continues to be a significant focus of PD research in terms of the α-synuclein Lewy body pathology. Mutations in several genes are associated with PD development including SNCA, which encodes α-synuclein. A variety of model systems have been employed to study α-synuclein physiology and pathophysiology in an attempt to relate more closely to PD pathology. These models include cellular and animal system exploring transgenic technologies, viral vector expression and knockdown approaches, and models to study the potential prion protein-like effects of α-synuclein. The current review focuses on human induced pluripotent stem cell (iPSC) models with a specific focus on mutations or multiplications of the SNCA gene. iPSCs are a rapidly evolving technology with huge promise in the study of normal physiology and disease modeling in vitro. The ability to maintain a patient’s genetic background and replicate similar cell phenotypes make iPSCs a powerful tool in the study of neurological diseases. This review focuses on the current knowledge about α-synuclein physiological function as well as its role in PD pathogenesis based on human iPSC models.

Engraftable Induced Pluripotent Stem Cell-Derived Neural Precursors for Brain Repair

Stem cell transplantation has attracted great interest for treatment of neurodegenerative diseases to provide neuroprotection, repair the lesioned neuronal network and restore functionality. Parkinson's disease (PD), in particular, has been a preferred target because motor disability that constitutes a core pathology of the disease is associated with local loss of dopaminergic neurons in a specific brain area, the substantia nigra pars compacta. These cells project to the striatum where they deliver the neurotransmitter dopamine that is involved in control of many aspects of motor behavior. Therefore, cell transplantation approaches in PD aim to replenish dopamine deficiency in the striatum. A major challenge in developing cell therapy approaches is the ability to generate large numbers of transplantable cells in a reliable and reproducible manner. In recent years the technological breakthrough of induced pluripotent stem cells (iPSCs) has demonstrated that this is possible at a preclinical level, accelerating clinical translation. A second important issue is to efficiently differentiate iPSCs into dopaminergic neuronal progenitors with restricted proliferation potential in order to avoid cellular overgrowth in vivo and minimize the risk of tumorigenesis. Here we describe an effective protocol that includes human iPSC differentiation to the dopaminergic lineage and enrichment in neuronal precursor cells expressing the polysialylated form of the neural cell adhesion molecule PSA-NCAM, through magnetically activated cell sorting. The resulting cells are transplanted and shown to survive, differentiate, and integrate within a striatal lesion model generated by unilateral 6-hydroxydopamine administration in mice of the NOD/SCID strain that supports xenografts.

Modelling Parkinson's Disease: iPSCs towards Better Understanding of Human Pathology

Parkinson’s Disease (PD) is a chronic neurodegenerative disorder characterized by motor and non-motor symptoms, among which are bradykinesia, rigidity, tremor as well as mental symptoms such as dementia. The underlying cause of Parkinson disease is degeneration of dopaminergic neurons. It has been challenging to develop an efficient animal model to accurately represent the complex phenotypes found with PD. However, it has become possible to recapitulate the myriad of phenotypes underlying the PD pathology by using human induced pluripotent stem cell (iPSC) technology. Patient-specific iPSC-derived dopaminergic neurons are available and present an opportunity to study many aspects of the PD phenotypes in a dish. In this review, we report the available data on iPSC-derived neurons derived from PD patients with identified gene mutations. Specifically, we will report on the key phenotypes of the generated iPSC-derived neurons from PD patients with different genetic background. Furthermore, we discuss the relationship these cellular phenotypes have to PD pathology and future challenges and prospects for iPSC modelling and understanding of the pathogenesis of PD.

Electrophysiological Phenotype Characterization of Human iPSC-Derived Neuronal Cell Lines by Means of High-Density Microelectrode Arrays

Recent advances in the field of cellular reprogramming have opened a route to studying the fundamental mechanisms underlying common neurological disorders. High-density microelectrode-arrays (HD-MEAs) provide unprecedented means to study neuronal physiology at different scales, ranging from network through single-neuron to subcellular features. In this work, HD-MEAs are used in vitro to characterize and compare human induced-pluripotent-stem-cell-derived dopaminergic and motor neurons, including isogenic neuronal lines modeling Parkinson's disease and amyotrophic lateral sclerosis. Reproducible electrophysiological network, single-cell and subcellular metrics are used for phenotype characterization and drug testing. Metrics, such as burst shape and axonal velocity, enable the distinction of healthy and diseased neurons. The HD-MEA metrics can also be used to detect the effects of dosing the drug retigabine to human motor neurons. Finally, it is shown that the ability to detect drug effects and the observed culture-to-culture variability critically depend on the number of available recording electrodes.

Phospholipase iPLA2β averts ferroptosis by eliminating a redox lipid death signal

Ferroptosis, triggered by discoordination of iron, thiols and lipids, leads to the accumulation of 15-hydroperoxy (Hp)-arachidonoyl-phosphatidylethanolamine (15-HpETE-PE), generated by complexes of 15-lipoxygenase (15-LOX) and a scaffold protein, phosphatidylethanolamine (PE)-binding protein (PEBP)1. As the Ca²⁺-independent phospholipase A₂β (iPLA₂β, PLA2G6 or PNPLA9 gene) can preferentially hydrolyze peroxidized phospholipids, it may eliminate the ferroptotic 15-HpETE-PE death signal. Here, we demonstrate that by hydrolyzing 15-HpETE-PE, iPLA₂β averts ferroptosis, whereas its genetic or pharmacological inactivation sensitizes cells to ferroptosis. Given that PLA2G6 mutations relate to neurodegeneration, we examined fibroblasts from a patient with a Parkinson's disease (PD)-associated mutation (fPD^R747W) and found selectively decreased 15-HpETE-PE-hydrolyzing activity, 15-HpETE-PE accumulation and elevated sensitivity to ferroptosis. CRISPR-Cas9-engineered Pnpla9^R748W/R748W mice exhibited progressive parkinsonian motor deficits and 15-HpETE-PE accumulation. Elevated 15-HpETE-PE levels were also detected in midbrains of rotenone-infused parkinsonian rats and α-synuclein-mutant Snca^A53T mice, with decreased iPLA₂β expression and a PD-relevant phenotype. Thus, iPLA₂β is a new ferroptosis regulator, and its mutations may be implicated in PD pathogenesis.

Patient-Derived Induced Pluripotent Stem Cell-Based Models in Parkinson's Disease for Drug Identification

Parkinson's disease (PD) is a common progressive neurodegenerative disorder characterized by loss of striatal-projecting dopaminergic neurons of the ventral forebrain, resulting in motor and cognitive deficits. Despite extensive efforts in understanding PD pathogenesis, no disease-modifying drugs exist. Recent advances in cell reprogramming technologies have facilitated the generation of patient-derived models for sporadic or familial PD and the identification of early, potentially triggering, pathological phenotypes while they provide amenable systems for drug discovery. Emerging developments highlight the enhanced potential of using more sophisticated cellular systems, including neuronal and glial co-cultures as well as three-dimensional systems that better simulate the human pathophysiology. In combination with high-throughput high-content screening technologies, these approaches open new perspectives for the identification of disease-modifying compounds. In this review, we discuss current advances and the challenges ahead in the use of patient-derived induced pluripotent stem cells for drug discovery in PD. We address new concepts implicating non-neuronal cells in disease pathogenesis and highlight the necessity for functional assays, such as calcium imaging and multi-electrode array recordings, to predict drug efficacy. Finally, we argue that artificial intelligence technologies will be pivotal for analysis of the large and complex data sets obtained, becoming game-changers in the process of drug discovery.

A compendious summary of Parkinson's disease patient-derived iPSCs in the first decade

The number of Parkinson's disease (PD) patients increases with aging, which brings heavy burden to families and society. The emergence of patient-derived induced pluripotent stem cells (iPSCs) has brought hope to the current situation of lacking new breakthroughs in diagnosis and treatment of PD. In this article, we reviewed and analyzed the current researches related to PD patient-derived iPSCs, in order to provide solid theoretical basis for future study of PD. In 2008, successful iPSCs derived from PD patients were reported. The current iPSCs research in PD mostly focused on the establishment of specific iPSCs models of PD patients carrying susceptible genes. The main source of PD patient-derived iPSCs is skin fibroblasts and the mainstream reprogramming methodology is the mature "four-factor" method, which introduces four totipotent correlation factors Oct4, Sox2, Klf4 and c-Myc into somatic cells. The main sources of iPSCs are patients with non-pedigrees and there have been no studies involving both PD patients and unaffected carriers within the same family. Most of the existing studies of PD patient-derived iPSCs started with the induction method for obtaining dopaminergic neurons in the first instance, but therapeutic applications are being increased. Although it is not the ultimate panacea, and there are still some unsolved problems (e.g., whether the mutated genes should be corrected or not), a better understanding of iPSCs may be a good gift for both PD patients and doctors due to their advantages in diagnosis and treatment of PD.