Increased motor neuron resilience by small molecule compounds that regulate IGF-II expression

Motor neurons and endothelial cells additively promote development and fusion of human iPSC-derived skeletal myocytes

BACKGROUND

Neurovascular cells have wide-ranging implications on skeletal muscle biology regulating myogenesis, maturation, and regeneration. Although several in vitro studies have investigated how motor neurons and endothelial cells interact with skeletal myocytes independently, there is limited knowledge about the combined effect of neural and vascular cells on muscle maturation and development.

METHODS

Here, we report a triculture system comprising human-induced pluripotent stem cell (iPSC)-derived skeletal myocytes, human iPSC-derived motor neurons, and primary human endothelial cells maintained under controlled media conditions. Briefly, iPSCs were differentiated to generate skeletal muscle progenitor cells (SMPCs). These SMPCs were seeded at a density of 5 × 104 cells/well in 12-well plates and allowed to differentiate for 7 days before adding iPSC-derived motor neurons at a concentration of 0.5 × 104 cells/well. The neuromuscular coculture was maintained for another 7 days in coculture media before addition of primary human umbilical vein endothelial cells (HUVEC) also at 0.5 × 104 cells/well. The triculture was maintained for another 7 days in triculture media comprising equal portions of muscle differentiation media, coculture media, and vascular media. Extensive morphological, genetic, and molecular characterization was performed to understand the combined and individual effects of neural and vascular cells on skeletal muscle maturation.

RESULTS

We observed that motor neurons independently promoted myofiber fusion, upregulated neuromuscular junction genes, and maintained a molecular niche supportive of muscle maturation. Endothelial cells independently did not support myofiber fusion and downregulated expression of LRP4 but did promote expression of type II specific myosin isoforms. However, neurovascular cells in combination exhibited additive increases in myofiber fusion and length, enhanced production of Agrin, along with upregulation of several key genes like MUSK, RAPSYN, DOK-7, and SLC2A4. Interestingly, more divergent effects were observed in expression of genes like MYH8, MYH1, MYH2, MYH4, and LRP4 and secretion of key molecular factors like amphiregulin and IGFBP-4.

CONCLUSIONS

Neurovascular cells when cultured in combination with skeletal myocytes promoted myocyte fusion with concomitant increase in expression of various neuromuscular genes. This triculture system may be used to gain a deeper understanding of the effects of the neurovascular niche on skeletal muscle biology and pathophysiology.

IGF2 in memory, neurodevelopmental disorders, and neurodegenerative diseases

Insulin-like growth factor 2 (IGF2) emerged as a critical mechanism of synaptic plasticity and learning and memory. Deficits in IGF2 in the brain, serum, or cerebrospinal fluid (CSF) are associated with brain diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). Increasing IGF2 levels enhances memory in healthy animals and reverses numerous symptoms in laboratory models of aging, neurodevelopmental disorders, and neurodegenerative diseases. These effects occur via the IGF2 receptor (IGF2R) - a receptor that is highly expressed in neurons and regulates protein trafficking, synthesis, and degradation. Here, I summarize the current knowledge regarding IGF2 expression and functions in the brain, particularly in memory, and propose a novel conceptual model for IGF2/IGF2R mechanisms of action in brain health and diseases.

Motor neuron-derived induced pluripotent stem cells as a drug screening platform for amyotrophic lateral sclerosis

The development of cell culture models that recapitulate the etiology and features of nervous system diseases is central to the discovery of new drugs and their translation onto therapies. Neuronal tissues are inaccessible due to skeletal constraints and the invasiveness of the procedure to obtain them. Thus, the emergence of induced pluripotent stem cell (iPSC) technology offers the opportunity to model different neuronal pathologies. Our focus centers on iPSCs derived from amyotrophic lateral sclerosis (ALS) patients, whose pathology remains in urgent need of new drugs and treatment. In this sense, we aim to revise the process to obtain motor neurons derived iPSCs (iPSC-MNs) from patients with ALS as a drug screening model, review current 3D-models and offer a perspective on bioinformatics as a powerful tool that can aid in the progress of finding new pharmacological treatments.

IGF2: Development, Genetic and Epigenetic Abnormalities

In the 30 years since the first report of parental imprinting in insulin-like growth factor 2 (Igf2) knockout mouse models, we have learnt much about the structure of this protein, its role and regulation. Indeed, many animal and human studies involving innovative techniques have shed light on the complex regulation of IGF2 expression. The physiological roles of IGF-II have also been documented, revealing pleiotropic tissue-specific and developmental-stage-dependent action. Furthermore, in recent years, animal studies have highlighted important interspecies differences in IGF-II function, gene expression and regulation. The identification of human disorders due to impaired IGF2 gene expression has also helped to elucidate the major role of IGF-II in growth and in tumor proliferation. The Silver-Russell and Beckwith-Wiedemann syndromes are the most representative imprinted disorders, as they constitute both phenotypic and molecular mirrors of IGF2-linked abnormalities. The characterization of patients with either epigenetic or genetic defects altering IGF2 expression has confirmed the central role of IGF-II in human growth regulation, particularly before birth, and its effects on broader body functions, such as metabolism or tumor susceptibility. Given the long-term health impact of these rare disorders, it is important to understand the consequences of IGF2 defects in these patients.

Applications of 3D Bioprinted-Induced Pluripotent Stem Cells in Healthcare

Induced pluripotent stem cell (iPSC) technology and advancements in three-dimensional (3D) bioprinting technology enable scientists to reprogram somatic cells to iPSCs and 3D print iPSC-derived organ constructs with native tissue architecture and function. iPSCs and iPSC-derived cells suspended in hydrogels (bioinks) allow to print tissues and organs for downstream medical applications. The bioprinted human tissues and organs are extremely valuable in regenerative medicine as bioprinting of autologous iPSC-derived organs eliminates the risk of immune rejection with organ transplants. Disease modeling and drug screening in bioprinted human tissues will give more precise information on disease mechanisms, drug efficacy, and drug toxicity than experimenting on animal models. Bioprinted iPSC-derived cancer tissues will aid in the study of early cancer development and precision oncology to discover patient-specific drugs. In this review, we present a brief summary of the combined use of two powerful technologies, iPSC technology, and 3D bioprinting in health-care applications.

Human pluripotent stem cell-derived models and drug screening in CNS precision medicine

Development of effective therapeutics for neurological disorders has historically been challenging partly because of lack of accurate model systems in which to investigate disease etiology and test new therapeutics at the preclinical stage. Human stem cells, particularly patient-derived induced pluripotent stem cells (iPSCs) upon differentiation, have the ability to recapitulate aspects of disease pathophysiology and are increasingly recognized as robust scalable systems for drug discovery. We review advances in deriving cellular models of human central nervous system (CNS) disorders using iPSCs along with strategies for investigating disease-relevant phenotypes, translatable biomarkers, and therapeutic targets. Given their potential to identify novel therapeutic targets and leads, we focus on phenotype-based, small-molecule screens employing human stem cell-derived models. Integrated efforts to assemble patient iPSC-derived cell models with deeply annotated clinicopathological data, along with molecular and drug-response signatures, may aid in the stratification of patients, diagnostics, and clinical trial success, shifting translational science and precision medicine approaches. A number of remaining challenges, including the optimization of cost-effective, large-scale culture of iPSC-derived cell types, incorporation of aging into neuronal models, as well as robustness and automation of phenotypic assays to support quantitative drug efficacy, toxicity, and metabolism testing workflows, are covered. Continued advancement of the field is expected to help fully humanize the process of CNS drug discovery.

Pluripotent stem cells for neurodegenerative disease modeling: an expert view on their value to drug discovery

INTRODUCTION

Neurodegenerative diseases have become a major global health concern, posing a huge disease burden on patients and their families. Although there has been rapid progress in the development of therapies, a lack of accurate disease models and efficient drug screening platforms have made achieving a breakthrough difficult. The technology of human-induced pluripotent stem cells (iPSCs) shows better recapitulation of disease pathophysiology and provides a more accessible supply of patient-specific samples compared to other modeling methods. It has been a powerful tool for mechanism exploration and drug development.

AREAS COVERED

This review describes the recent use of human iPSC-derived cells for modeling neurodegenerative disorders and discovering potential drugs.

EXPERT OPINION

Model systems based on iPSC-derived cells have created a paradigm shift in drug discovery. Accuracy, consistency, translatability, and cost-effectiveness are the four major focuses of academic and industrial communities to fulfill the potential of iPSC technology for their purposes. It is the art of balance between these four factors to generate efficacious outputs with maximum efficiency. Future studies should persist in refining this technology and promote its application in this field to benefit all the disease-affected population eventually.

Stem cells: A path towards improved epilepsy therapies

Despite the immense growth of new anti-seizure drugs (ASDs), approximately one-third of epilepsy patients remain resistant to current treatment options. Advancements in whole genome sequencing technology continues to identify an increasing number of epilepsy-associated genes at a rate that is outpacing the development of in vivo animal models. Patient-derived induced pluripotent stem cells (iPSCs) show promise in providing a platform for modeling genetic epilepsies, high throughput drug screening, and personalized medicine. This is largely due to the ease of collecting donor cells for iPSC reprogramming, and their ability to be maintained in vitro, while preserving the patient's genetic background. In this review, we summarize the current state of iPSC research in epilepsy and closely related syndromes, discuss the growing need for high-throughput drug screening (HTS), and review the use of stem cell technology for the purpose of autologous transplantation for epilepsy stem cell therapy. Although the use of iPSC technology, as it applies to ASD discovery, is in its infancy, we highlight the significant progress that has been made in phenotype and assay development to facilitate systematic HTS for personalized medicine. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

From Neuronal Differentiation of iPSCs to 3D Neuro-Organoids: Modelling and Therapy of Neurodegenerative Diseases

In the last decade, the advances made into the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) led to great improvements towards their use as models of diseases. In particular, in the field of neurodegenerative diseases, iPSCs technology allowed to culture in vitro all types of patient-specific neural cells, facilitating not only the investigation of diseases' etiopathology, but also the testing of new drugs and cell therapies, leading to the innovative concept of personalized medicine. Moreover, iPSCs can be differentiated and organized into 3D organoids, providing a tool which mimics the complexity of the brain's architecture. Furthermore, recent developments in 3D bioprinting allowed the study of physiological cell-to-cell interactions, given by a combination of several biomaterials, scaffolds, and cells. This technology combines bio-plotter and biomaterials in which several types of cells, such as iPSCs or differentiated neurons, can be encapsulated in order to develop an innovative cellular model. IPSCs and 3D cell cultures technologies represent the first step towards the obtainment of a more reliable model, such as organoids, to facilitate neurodegenerative diseases' investigation. The combination of iPSCs, 3D organoids and bioprinting will also allow the development of new therapeutic approaches. Indeed, on the one hand they will lead to the development of safer and patient-specific drugs testing but, also, they could be developed as cell-therapy for curing neurodegenerative diseases with a regenerative medicine approach.