Pharmacological rescue of mitochondrial and neuronal defects in SPG7 hereditary spastic paraplegia patient neurons using high throughput assays

Current Applications of Human Pluripotent Stem Cells in Neuroscience Research and Cell Transplantation Therapy for Neurological Disorders

Many neurological diseases involving tissue damage cannot be treated with drug-based approaches, and the inaccessibility of human brain samples further hampers the study of these diseases. Human pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), provide an excellent model for studying neural development and function. PSCs can be differentiated into various neural cell types, providing a renewal source of functional human brain cells. Therefore, PSC-derived neural cells are increasingly used for multiple applications, including neurodevelopmental and neurotoxicological studies, neurological disease modeling, drug screening, and regenerative medicine. In addition, the neural cells generated from patient iPSCs can be used to study patient-specific disease signatures and progression. With the recent advances in genome editing technologies, it is possible to remove the disease-related mutations in the patient iPSCs to generate corrected iPSCs. The corrected iPSCs can differentiate into neural cells with normal physiological functions, which can be used for autologous transplantation. This review highlights the current progress in using PSCs to understand the fundamental principles of human neurodevelopment and dissect the molecular mechanisms of neurological diseases. This knowledge can be applied to develop better drugs and explore cell therapy options. We also discuss the basic requirements for developing cell transplantation therapies for neurological disorders and the current status of the ongoing clinical trials.

iPSC models of mitochondrial diseases

Mitochondrial diseases are historically difficult to study. They cause multi-systemic defects with prevalent impairment of hard-to-access tissues such as the brain and the heart. Furthermore, they suffer from a paucity of conventional model systems, especially because of the challenges associated with mitochondrial DNA (mtDNA) engineering. Consequently, most mitochondrial diseases are currently untreatable. Human induced pluripotent stem cells (iPSCs) represent a promising approach for developing human model systems and assessing therapeutic avenues in a patient- and tissue-specific context. iPSCs are being increasingly used to investigate mitochondrial diseases, either for dissecting mutation-specific defects within two-dimensional (2D) or three-dimensional (3D) progenies or for unveiling the impact of potential treatment options. Here, we review how iPSC-derived 2D cells and 3D organoid models have been applied to the study of mitochondrial diseases caused by either nuclear or mtDNA defects. We anticipate that the field of iPSC-driven modeling of mitochondrial diseases will continue to grow, likely leading to the development of innovative platforms for treatment discovery and toxicity that could benefit the patient community suffering from these debilitating disorders with highly unmet medical needs.

Combining NeuroPainting with transcriptomics reveals cell-type-specific morphological and molecular signatures of the 22q11.2 deletion

Neuropsychiatric conditions pose substantial challenges for therapeutic development due to their complex and poorly understood underlying mechanisms. High-throughput, unbiased phenotypic assays present a promising path for advancing therapeutic discovery, especially within disease-relevant neural tissues. Here, we introduce NeuroPainting, a novel adaptation of the Cell Painting assay, optimized for high-dimensional morphological phenotyping of neural cell types, including neurons, neuronal progenitor cells, and astrocytes derived from human stem cells. Using NeuroPainting, we quantified cell structure and organelle behavior across various brain cell types, creating a public dataset of over 4,000 cellular traits. This extensive dataset not only sets a new benchmark for phenotypic screening in neuropsychiatric research but also serves as a gold standard for the research community, enabling comparisons and validation of results. We then applied NeuroPainting to identify morphological signatures associated with the 22q11.2 deletion, a major genetic risk factor for schizophrenia. We observed profound cell-type-specific effects of the 22q11.2 deletion, with significant alterations in mitochondrial structure, endoplasmic reticulum organization, and cytoskeletal dynamics, particularly in astrocytes. Transcriptomic analysis revealed reduced expression of cell adhesion genes in 22q11.2 deletion astrocytes, consistent with recent post-mortem findings. Integrating the RNA sequencing data and morphological profiles uncovered a novel biological link between altered expression of specific cell adhesion molecules and observed changes in mitochondrial morphology in 22q11.2 deletion astrocytes. These findings underscore the power of combined phenomic and transcriptomic analyses to reveal mechanistic insights associated with human genetic variants of neuropsychiatric conditions.

Coordinated metabolic responses to cyclophilin D deletion in the developing heart

In the embryonic heart, the activation of the mitochondrial electron transport chain (ETC) coincides with the closure of the cyclophilin D (CypD) regulated mitochondrial permeability transition pore (mPTP). However, it remains to be established whether the absence of CypD has a regulatory effect on mitochondria during cardiac development. Using a variety of assays to analyze cardiac tissue from wildtype and CypD knockout mice from embryonic day (E)9.5 to adult, we found that mitochondrial structure, function, and metabolism show distinct transitions. Deletion of CypD altered the timing of these transitions as the mPTP was closed at all ages, leading to coupled ETC activity in the early embryo, decreased citrate synthase activity, and an altered metabolome particularly after birth. Our results suggest that manipulating CypD activity may control myocyte proliferation and differentiation and could be a tool to increase ATP production and cardiac function in immature hearts.

Pluripotent Stem Cells as a Preclinical Cellular Model for Studying Hereditary Spastic Paraplegias

Hereditary spastic paraplegias (HSPs) comprise a family of degenerative diseases mostly hitting descending axons of corticospinal neurons. Depending on the gene and mutation involved, the disease could present as a pure form with limb spasticity, or a complex form associated with cerebellar and/or cortical signs such as ataxia, dysarthria, epilepsy, and intellectual disability. The progressive nature of HSPs invariably leads patients to require walking canes or wheelchairs over time. Despite several attempts to ameliorate the life quality of patients that have been tested, current therapeutical approaches are just symptomatic, as no cure is available. Progress in research in the last two decades has identified a vast number of genes involved in HSP etiology, using cellular and animal models generated on purpose. Although unanimously considered invaluable tools for basic research, those systems are rarely predictive for the establishment of a therapeutic approach. The advent of induced pluripotent stem (iPS) cells allowed instead the direct study of morphological and molecular properties of the patient's affected neurons generated upon in vitro differentiation. In this review, we revisited all the present literature recently published regarding the use of iPS cells to differentiate HSP patient-specific neurons. Most studies have defined patient-derived neurons as a reliable model to faithfully mimic HSP in vitro, discovering original findings through immunological and -omics approaches, and providing a platform to screen novel or repurposed drugs. Thereby, one of the biggest hopes of current HSP research regards the use of patient-derived iPS cells to expand basic knowledge on the disease, while simultaneously establishing new therapeutic treatments for both generalized and personalized approaches in daily medical practice.