Induced pluripotent stem cells from a spinal muscular atrophy patient

Cell reprogramming: methods, mechanisms and applications

Cell reprogramming represents a powerful approach to achieve the conversion cells of one type into cells of another type of interest, which has substantially changed the landscape in the field of developmental biology, regenerative medicine, disease modeling, drug discovery and cancer immunotherapy. Cell reprogramming is a complex and ordered process that involves the coordination of transcriptional, epigenetic, translational and metabolic changes. Over the past two decades, a range of questions regarding the facilitators/barriers, the trajectories, and the mechanisms of cell reprogramming have been extensively investigated. This review summarizes the recent advances in cell reprogramming mediated by transcription factors or chemical molecules, followed by elaborating on the important roles of biophysical cues in cell reprogramming. Additionally, this review will detail our current understanding of the mechanisms that govern cell reprogramming, including the involvement of the recently discovered biomolecular condensates. Finally, the review discusses the broad applications and future directions of cell reprogramming in developmental biology, disease modeling, drug development, regenerative/rejuvenation therapy, and cancer immunotherapy.

Human Induced Pluripotent Stem Cells: Directed Differentiation Methods and Applications in Brain Diseases

Human induced pluripotent stem cells (hiPSCs), similar to embryonic stem cells, are a class of pluripotent stem cells with the potential to differentiate into various kinds of cells. Because the application of hiPSCs obtained by reprogramming patients' somatic cells in the treatment of brain diseases bypasses the ethical constraints on the use of embryonic stem cells and mitigates immune rejection, hiPSCs have profound clinical application prospects. In this review, we first summarized the differentiation methods of hiPSCs into different kinds of neurons, and secondly discussed the application of hiPSCs in several brain disease models, so as to provide a reference for the future application of hiPSCs in the studies and treatment of brain diseases.

A longevity-specific bank of induced pluripotent stem cells from centenarians and their offspring

Centenarians provide a unique lens through which to study longevity, healthy aging, and resiliency. Moreover, models of human aging and resilience to disease that allow for the testing of potential interventions are virtually non-existent. We obtained and characterized over 96 centenarian and offspring peripheral blood samples including those connected to functional independence data highlighting resistance to disability and cognitive impairment. Targeted methylation arrays were used in molecular aging clocks to compare and contrast differences between biological and chronological age in these specialized subjects. Isolated peripheral blood mononuclear cells (PBMCs) from 20 of these subjects were then successfully reprogrammed into high-quality induced pluripotent stem cell (iPSC) lines which were functionally characterized for pluripotency, genomic stability, and the ability to undergo directed differentiation. The result of this work is a one-of-a-kind resource for studies of human longevity and resilience that can fuel the discovery and validation of novel therapeutics for aging-related disease.

Patient-specific responses to SMN2 splice-modifying treatments in spinal muscular atrophy fibroblasts

The availability of three therapies for the neuromuscular disease spinal muscular atrophy (SMA) highlights the need to match patients to the optimal treatment. Two of these treatments (nusinersen and risdiplam) target splicing of SMN2, but treatment outcomes vary from patient to patient. An incomplete understanding of the complex interactions among SMA genetics, SMN protein and mRNA levels, and gene-targeting treatments, limits our ability to explain this variability and identify optimal treatment strategies for individual patients. To address this, we analyzed responses to nusinersen and risdiplam in 45 primary fibroblast cell lines. Pre-treatment SMN2-FL, SMN2Δ7 mRNA, and SMN protein levels were influenced by SMN2 copy number, age, and sex. After treatment, SMN and mRNA levels were more heterogeneous. In 43% of patients, response to both therapies was similar, but in 57% one treatment led to a significantly higher SMN increase than the other treatment. Younger age, higher SMN2 copy number, and higher SMN levels before treatment predicted better in vitro efficacy. These findings showcase patient-derived fibroblasts as a tool for identifying molecular predictors for personalized treatment.

Proteomic and functional comparison between human induced and embryonic stem cells

Human induced pluripotent stem cells (hiPSCs) have great potential to be used as alternatives to embryonic stem cells (hESCs) in regenerative medicine and disease modelling. In this study, we characterise the proteomes of multiple hiPSC and hESC lines derived from independent donors and find that while they express a near-identical set of proteins, they show consistent quantitative differences in the abundance of a subset of proteins. hiPSCs have increased total protein content, while maintaining a comparable cell cycle profile to hESCs, with increased abundance of cytoplasmic and mitochondrial proteins required to sustain high growth rates, including nutrient transporters and metabolic proteins. Prominent changes detected in proteins involved in mitochondrial metabolism correlated with enhanced mitochondrial potential, shown using high-resolution respirometry. hiPSCs also produced higher levels of secreted proteins, including growth factors and proteins involved in the inhibition of the immune system. The data indicate that reprogramming of fibroblasts to hiPSCs produces important differences in cytoplasmic and mitochondrial proteins compared to hESCs, with consequences affecting growth and metabolism. This study improves our understanding of the molecular differences between hiPSCs and hESCs, with implications for potential risks and benefits for their use in future disease modelling and therapeutic applications.

The Relevance of Spinal Muscular Atrophy Biomarkers in the Treatment Era

Spinal muscular atrophy (SMA) is a severe neuromuscular disorder that currently has an approved treatment for all forms of the disease. Previously, biomarkers were primarily used for diagnostic purposes, such as detecting the presence of the disease or determining a specific clinical type of SMA. Currently, with the availability of therapy, biomarkers have become more valuable due to their potential for prognostic, predictive, and pharmacodynamic applications. This review describes the most promising physiological, functional, imaging and molecular biomarkers for SMA, derived from different patients' tissues. The review summarizes information about classical biomarkers that are already used in clinical practice as well as fresh findings on promising biomarkers that have been recently disclosed. It highlights the usefulness, limitations, and strengths of each potential biomarker, indicating the purposes for which each is best suited and when combining them may be most beneficial.

SMN1 c.5C>G (p.Ala2Gly) missense variant, a challenging molecular SMA diagnosis associated with mild disease, preserves SMN nuclear gems in patient-specific fibroblasts

Introduction

Spinal muscular atrophy (SMA) is caused by homozygous loss of the SMN1 gene with SMN2 gene copy number correlating with disease severity. Rarely SMA is caused by a deletion on one allele and a pathogenic variant on the other. The pathogenic missense variant c.5C>G (p.Ala2Gly) correlates with a mild disease phenotype that does not correlate with SMN2 copy number. In a mouse model the c.5C>G transgene produces SMN that is thought to form partially functional SMN complexes, but levels in humans have not yet been investigated.

Methods

We identified two patients with mild SMA caused by a heterozygous deletion of SMN1 and the heterozygous variant, c.5C>G. Molecular findings were confirmed with deletion/duplication analysis and Sanger sequencing. Skin fibroblasts were collected and cultured, and SMN expression was analyzed using immunofluorescence.

Results

Two patients with slowly progressing mild weakness were confirmed to have heterozygous pathogenic missense variant c.5C>G and a heterozygous deletion of SMN1. Their clinical presentation revealed much milder disease progression than patients with matched SMN2 copy number. Analysis of the patients' fibroblasts revealed much higher numbers of SMN nuclear complexes than a patient with a homozygous SMN1 deletion and matched SMN2 copy number.

Conclusions

These case reports reinforce that the rare c.5C>G variant causes mild disease. Furthermore, the analysis of SMA nuclear gems in patient samples supports the theory that the p.Ala2Gly SMN can form partially functional SMN complexes that may carry out essential cellular functions and result in mild disease.

Enhancing genome editing in hPSCs through dual inhibition of DNA damage response and repair pathways

Precise genome editing is crucial for establishing isogenic human disease models and ex vivo stem cell therapy from the patient-derived hPSCs. Unlike Cas9-mediated knock-in, cytosine base editor and prime editor achieve the desirable gene correction without inducing DNA double strand breaks. However, hPSCs possess highly active DNA repair pathways and are particularly susceptible to p53-dependent cell death. These unique characteristics impede the efficiency of gene editing in hPSCs. Here, we demonstrate that dual inhibition of p53-mediated cell death and distinct activation of the DNA damage repair system upon DNA damage by cytosine base editor or prime editor additively enhanced editing efficiency in hPSCs. The BE4stem system comprised of p53DD, a dominant negative p53, and three UNG inhibitor, engineered to specifically diminish base excision repair, improves cytosine base editor efficiency in hPSCs. Addition of dominant negative MLH1 to inhibit mismatch repair activity and p53DD in the conventional prime editor system also significantly enhances prime editor efficiency in hPSCs. Thus, combined inhibition of the distinct cellular cascades engaged in hPSCs upon gene editing could significantly enhance precise genome editing in these cells.

CRISPRi: a way to integrate iPSC-derived neuronal models

The genetic landscape of neurodegenerative diseases encompasses genes affecting multiple cellular pathways which exert effects in an array of neuronal and glial cell-types. Deconvolution of the roles of genes implicated in disease and the effects of disease-associated variants remains a vital step in the understanding of neurodegeneration and the development of therapeutics. Disease modelling using patient induced pluripotent stem cells (iPSCs) has enabled the generation of key cell-types associated with disease whilst maintaining the genomic variants that predispose to neurodegeneration. The use of CRISPR interference (CRISPRi), alongside other CRISPR-perturbations, allows the modelling of the effects of these disease-associated variants or identifying genes which modify disease phenotypes. This review summarises the current applications of CRISPRi in iPSC-derived neuronal models, such as fluorescence-activated cell sorting (FACS)-based screens, and discusses the future opportunities for disease modelling, identification of disease risk modifiers and target/drug discovery in neurodegeneration.

Optogenetic and chemogenetic approaches for modeling neurological disorders in vivo

Animal models of human neurological disorders provide valuable experimental tools which enable us to study various aspects of disorder pathogeneses, ranging from structural abnormalities and disrupted metabolism and signaling to motor and mental deficits, and allow us to test novel therapies in preclinical studies. To be valid, these animal models should recapitulate complex pathological features at the molecular, cellular, tissue, and behavioral levels as closely as possible to those observed in human subjects. Pathological states resembling known human neurological disorders can be induced in animal species by toxins, genetic factors, lesioning, or exposure to extreme conditions. In recent years, novel animal models recapitulating neuropathologies in humans have been introduced. These animal models are based on synthetic biology approaches: opto- and chemogenetics. In this paper, we review recent opto- and chemogenetics-based animal models of human neurological disorders. These models allow for the creation of pathological states by disrupting specific processes at the cellular level. The artificial pathological states mimic a range of human neurological disorders, such as aging-related dementia, Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, epilepsy, and ataxias. Opto- and chemogenetics provide new opportunities unavailable with other animal models of human neurological disorders. These techniques enable researchers to induce neuropathological states varying in severity and ranging from acute to chronic. We also discuss future directions for the development and application of synthetic biology approaches for modeling neurological disorders.

A longevity-specific bank of induced pluripotent stem cells from centenarians and their offspring

Centenarians provide a unique lens through which to study longevity, healthy aging, and resiliency. Moreover, models of human aging and resilience to disease that allow for the testing of potential interventions are virtually non-existent. We obtained and characterized over 50 centenarian and offspring peripheral blood samples including those connected to functional independence data highlighting resistance to disability and cognitive impairment. Targeted methylation arrays were used in molecular aging clocks to compare and contrast differences between biological and chronological age in these specialized subjects. Isolated peripheral blood mononuclear cells (PBMCs) were then successfully reprogrammed into high-quality induced pluripotent stem cell (iPSC) lines which were functionally characterized for pluripotency, genomic stability, and the ability to undergo directed differentiation. The result of this work is a one-of-a-kind resource for studies of human longevity and resilience that can fuel the discovery and validation of novel therapeutics for aging-related disease.

Generation of human iPSC-derived phrenic-like motor neurons to model respiratory motor neuron degeneration in ALS

The fatal motor neuron (MN) disease Amyotrophic Lateral Sclerosis (ALS) is characterized by progressive MN degeneration. Phrenic MNs (phMNs) controlling the activity of the diaphragm are prone to degeneration in ALS, leading to death by respiratory failure. Understanding of the mechanisms of phMN degeneration in ALS is limited, mainly because human experimental models to study phMNs are lacking. Here we describe a method enabling the derivation of phrenic-like MNs from human iPSCs (hiPSC-phMNs) within 30 days. This protocol uses an optimized combination of small molecules followed by cell-sorting based on a cell-surface protein enriched in hiPSC-phMNs, and is highly reproducible using several hiPSC lines. We show further that hiPSC-phMNs harbouring ALS-associated amplification of the C9orf72 gene progressively lose their electrophysiological activity and undergo increased death compared to isogenic controls. These studies establish a previously unavailable protocol to generate human phMNs offering a disease-relevant system to study mechanisms of respiratory MN dysfunction.

Assessment of Nuclear Gem Quantity for Evaluating the Efficacy of Antisense Oligonucleotides in Spinal Muscular Atrophy Cells

Spinal muscular atrophy is a neuromuscular disorder caused by mutations in both copies of the survival motor neuron gene 1 (SMN1), which lead to reduction in the production of the SMN protein. Currently, there are several therapies that have been approved for SMA, with many more undergoing active research. While various biomarkers have been proposed for assessing the effectiveness of SMA treatment, a universally accepted one still has not been identified. This study aimed to describe a fast and reliable method using the number of gems in cell nuclei as a potential tool for assessment of splicing correction of oligonucleotide efficacy in SMA cells. To gain insight into whether the number of gems in cell nuclei varies based on their SMN genotype and whether the increase in gem number is associated with therapeutic response, we utilized fibroblast cell cultures obtained from a patient with SMA type II and from a healthy individual. We discovered a remarkable difference in the number of gems found in the nuclei of these cells, specifically when counting gems per 100 nuclei. The SMA fibroblasts treated with antisense oligonucleotide showed beneficial effects in correcting the abnormal splicing of SMN2 exon 7. It was observed that there was a significant increase in the number of gems in the treated cells compared to the intact SMA cells. The results obtained significantly correlate with an increase of full-length SMN transcript sharing. Based on our findings, we propose using the quantity of gems as a reliable biomarker for SMA drug development.

The MORC2 p.S87L mutation reduces proliferation of pluripotent stem cells derived from a patient with the spinal muscular atrophy-like phenotype by inhibiting proliferation-related signaling pathways

Mutations in the microrchidia CW-type zinc finger protein 2 (MORC2) gene are the causative agent of Charcot-Marie-Tooth disease type 2Z (CMT2Z), and the hotspot mutation p.S87L is associated with a more severe spinal muscular atrophy-like clinical phenotype. The aims of this study were to determine the mechanism of the severe phenotype caused by the MORC2 p.S87L mutation and to explore potential treatment strategies. Epithelial cells were isolated from urine samples from a spinal muscular atrophy (SMA)-like patient (MORC2 p.S87L), a CMT2Z patient (MORC2 p.Q400R), and a healthy control and induced to generate pluripotent stem cells, which were then differentiated into motor neuron precursor cells. Next-generation RNA sequencing followed by KEGG pathway enrichment analysis revealed that differentially expressed genes involved in the PI3K/Akt and MAPK/ERK signaling pathways were enriched in the p.S87L SMA-like patient group and were significantly downregulated in induced pluripotent stem cells. Reduced proliferation was observed in the induced pluripotent stem cells and motor neuron precursor cells derived from the p.S87L SMA-like patient group compared with the CMT2Z patient group and the healthy control. G0/G1 phase cell cycle arrest was observed in induced pluripotent stem cells derived from the p.S87L SMA-like patient. MORC2 p.S87L-specific antisense oligonucleotides (p.S87L-ASO-targeting) showed significant efficacy in improving cell proliferation and activating the PI3K/Akt and MAPK/ERK pathways in induced pluripotent stem cells. However, p.S87L-ASO-targeting did not rescue proliferation of motor neuron precursor cells. These findings suggest that downregulation of the PI3K/Akt and MAPK/ERK signaling pathways leading to reduced cell proliferation and G0/G1 phase cell cycle arrest in induced pluripotent stem cells might be the underlying mechanism of the severe p.S87L SMA-like phenotype. p.S87L-ASO-targeting treatment can alleviate disordered cell proliferation in the early stage of pluripotent stem cell induction.

Advances in Genetic Reprogramming: Prospects from Developmental Biology to Regenerative Medicine

The foundations of cell reprogramming were laid by Yamanaka and co-workers, who showed that somatic cells can be reprogrammed into pluripotent cells (induced pluripotency). Since this discovery, the field of regenerative medicine has seen advancements. For example, because they can differentiate into multiple cell types, pluripotent stem cells are considered vital components in regenerative medicine aimed at the functional restoration of damaged tissue. Despite years of research, both replacement and restoration of failed organs/ tissues have remained elusive scientific feats. However, with the inception of cell engineering and nuclear reprogramming, useful solutions have been identified to counter the need for compatible and sustainable organs. By combining the science underlying genetic engineering and nuclear reprogramming with regenerative medicine, scientists have engineered cells to make gene and stem cell therapies applicable and effective. These approaches have enabled the targeting of various pathways to reprogramme cells, i.e., make them behave in beneficial ways in a patient-specific manner. Technological advancements have clearly supported the concept and realization of regenerative medicine. Genetic engineering is used for tissue engineering and nuclear reprogramming and has led to advances in regenerative medicine. Targeted therapies and replacement of traumatized , damaged, or aged organs can be realized through genetic engineering. Furthermore, the success of these therapies has been validated through thousands of clinical trials. Scientists are currently evaluating induced tissue-specific stem cells (iTSCs), which may lead to tumour-free applications of pluripotency induction. In this review, we present state-of-the-art genetic engineering that has been used in regenerative medicine. We also focus on ways that genetic engineering and nuclear reprogramming have transformed regenerative medicine and have become unique therapeutic niches.

Advances in iPSC Technology in Neural Disease Modeling, Drug Screening, and Therapy

Neurodegenerative disorders (NDs) including Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease are all incurable and can only be managed with drugs for the associated symptoms. Animal models of human illnesses help to advance our understanding of the pathogenic processes of diseases. Understanding the pathogenesis as well as drug screening using appropriate disease models of neurodegenerative diseases (NDs) are vital for identifying novel therapies. Human-derived induced pluripotent stem cell (iPSC) models can be an efficient model to create disease in a dish and thereby can proceed with drug screening and identifying appropriate drugs. This technology has many benefits, including efficient reprogramming and regeneration potential, multidirectional differentiation, and the lack of ethical concerns, which open up new avenues for studying neurological illnesses in greater depth. The review mainly focuses on the use of iPSC technology in neuronal disease modeling, drug screening, and cell therapy.

MELAS-Derived Neurons Functionally Improve by Mitochondrial Transfer from Highly Purified Mesenchymal Stem Cells (REC)

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode (MELAS) syndrome, caused by a single base substitution in mitochondrial DNA (m.3243A>G), is one of the most common maternally inherited mitochondrial diseases accompanied by neuronal damage due to defects in the oxidative phosphorylation system. There is no established treatment. Our previous study reported a superior restoration of mitochondrial function and bioenergetics in mitochondria-deficient cells using highly purified mesenchymal stem cells (RECs). However, whether such exogenous mitochondrial donation occurs in mitochondrial disease models and whether it plays a role in the recovery of pathological neuronal functions is unknown. Here, utilizing induced pluripotent stem cells (iPSC), we differentiated neurons with impaired mitochondrial function from patients with MELAS. MELAS neurons and RECs/mesenchymal stem cells (MSCs) were cultured under contact or non-contact conditions. Both RECs and MSCs can donate mitochondria to MELAS neurons, but RECs are more excellent than MSCs for mitochondrial transfer in both systems. In addition, REC-mediated mitochondrial transfer significantly restored mitochondrial function, including mitochondrial membrane potential, ATP/ROS production, intracellular calcium storage, and oxygen consumption rate. Moreover, mitochondrial function was maintained for at least three weeks. Thus, REC-donated exogenous mitochondria might offer a potential therapeutic strategy for treating neurological dysfunction in MELAS.

Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy

Spinal muscular atrophy (SMA), the top genetic cause of infant mortality, is characterized by motor neuron degeneration. Mechanisms underlying SMA pathogenesis remain largely unknown. Here, we report that the activity of cyclin-dependent kinase 5 (Cdk5) and the conversion of its activating subunit p35 to the more potent activator p25 are significantly up-regulated in mouse models and human induced pluripotent stem cell (iPSC) models of SMA. The increase of Cdk5 activity occurs before the onset of SMA phenotypes, suggesting that it may be an initiator of the disease. Importantly, aberrant Cdk5 activation causes mitochondrial defects and motor neuron degeneration, as the genetic knockout of p35 in an SMA mouse model rescues mitochondrial transport and fragmentation defects, and alleviates SMA phenotypes including motor neuron hyperexcitability, loss of excitatory synapses, neuromuscular junction denervation, and motor neuron degeneration. Inhibition of the Cdk5 signaling pathway reduces the degeneration of motor neurons derived from SMA mice and human SMA iPSCs. Altogether, our studies reveal a critical role for the aberrant activation of Cdk5 in SMA pathogenesis and suggest a potential target for therapeutic intervention.

Assessment of Fallopian Tube Epithelium Features Derived from Induced Pluripotent Stem Cells of Both Fallopian Tube and Skin Origins

Fallopian tube epithelial cells (FTECs) play a significant role in the development of high-grade serous ovarian cancer (HGSOC), but their utilization in in vitro experiments presents challenges. To address these limitations, induced pluripotent stem cells (iPSCs) have been employed as a potential solution, driven by the hypothesis that orthologous iPSCs may offer superior differentiation capabilities compared with their non-orthologous counterparts. Our objective was to generate iPSCs from FTECs, referred to as FTEC-iPSCs, and compare their differentiation potential with iPSCs derived from skin keratinocytes (NHEK). By introducing a four-factor Sendai virus transduction system, we successfully derived iPSCs from FTECs. To assess the differentiation capacity of iPSCs, we utilized embryoid body formation, revealing positive immunohistochemical staining for markers representing the three germ layers. In vivo tumorigenesis evaluation further validated the pluripotency of iPSCs, as evidenced by the formation of tumors in immunodeficient mice, with histological analysis confirming the presence of tissues from all three germ layers. Quantitative polymerase chain reaction (qPCR) analysis illuminated a sequential shift in gene expression, encompassing pluripotent, mesodermal, and intermediate mesoderm-related genes, during the iPSC differentiation process into FTECs. Notably, the introduction of WNT3A following intermediate mesoderm differentiation steered the cells toward a FTEC phenotype, supported by the expression of FTEC-related markers and the formation of tubule-like structures. In specific culture conditions, the expression of FTEC-related genes was comparable in FTECs derived from FTEC-iPSCs compared with those derived from NHEK-iPSCs. To conclude, our study successfully generated iPSCs from FTECs, demonstrating their capacity for FTEC differentiation. Furthermore, iPSCs originating from orthologous cell sources exhibited comparable differentiation capabilities. These findings hold promise for using iPSCs in modeling and investigating diseases associated with these specific cell types.

Organ-Chips Enhance the Maturation of Human iPSC-Derived Dopamine Neurons

While cells in the human body function in an environment where the blood supply constantly delivers nutrients and removes waste, cells in conventional tissue culture well platforms are grown with a static pool of media above them and often lack maturity, limiting their utility to study cell biology in health and disease. In contrast, organ-chip microfluidic systems allow the growth of cells under constant flow, more akin to the in vivo situation. Here, we differentiated human induced pluripotent stem cells into dopamine neurons and assessed cellular properties in conventional multi-well cultures and organ-chips. We show that organ-chip cultures, compared to multi-well cultures, provide an overall greater proportion and homogeneity of dopaminergic neurons as well as increased levels of maturation markers. These organ-chips are an ideal platform to study mature dopamine neurons to better understand their biology in health and ultimately in neurological disorders.

Effect of Honokiol on culture time and survival of Alzheimer's disease iPSC-derived neurons

Introduction

Patient-derived induced pluripotent stem cells (iPSCs) have been widely used as disease models to test new therapeutic strategies. Moreover, the regenerative potential of stem cells can be improved with the use of biologically active compounds. Our study was designed to explore the effect of honokiol, a small polyphenol molecule extracted from Magnolia officinalis, on the survival and culture time of iPSC-derived neurons from a sporadic Alzheimer's disease (AD) patient. This study aimed to generate iPSCs from peripheral blood mononuclear cells (PBMCs) of an AD patient using episomal plasmids with a nucleofector system and differentiate them into neurons. These iPSC-derived neurons were used to investigate the effect of honokiol extracted from M. officinalis on their survival and long-term cultures.

Methods

IPSCs were generated from PBMCs of an AD patient by introducing Oct-3/4, Sox2, Klf4, L-Myc, and Lin28 using NucleofectorTM Technology. Differentiation of neurons derived from iPSCs was carried out using inducers and recognized by biomarkers. The viability of iPSC-derived neurons with the addition of honokiol extracted from the bark of M. officinalis was determined by the MTT analytical kit.

Results

IPSCs were generated by reprogramming AD patient-derived PBMCs and subsequently converted into neurons. The survival and growth of iPSC-derived neurons were significantly enhanced by adding honokiol in the experiment conditions.

Conclusion

AD iPSC-derived neurons had a high viability rate when cultured in the presence of honokiol. These results have shown that AD iPSC-derived neurons can be an excellent model for screening neurotrophic agents and improving the conditions for long-term cultures of human iPSC-derived neurons. Honokiol proves to be a potential candidate for cellular therapeutics against neurodegenerative disorders.

LONRF2 is a protein quality control ubiquitin ligase whose deficiency causes late-onset neurological deficits

Protein misfolding is a major factor of neurodegenerative diseases. Post-mitotic neurons are highly susceptible to protein aggregates that are not diluted by mitosis. Therefore, post-mitotic cells may have a specific protein quality control system. Here, we show that LONRF2 is a bona fide protein quality control ubiquitin ligase induced in post-mitotic senescent cells. Under unperturbed conditions, LONRF2 is predominantly expressed in neurons. LONRF2 binds and ubiquitylates abnormally structured TDP-43 and hnRNP M1 and artificially misfolded proteins. Lonrf2-/- mice exhibit age-dependent TDP-43-mediated motor neuron (MN) degeneration and cerebellar ataxia. Mouse induced pluripotent stem cell-derived MNs lacking LONRF2 showed reduced survival, shortening of neurites and accumulation of pTDP-43 and G3BP1 after long-term culture. The shortening of neurites in MNs from patients with amyotrophic lateral sclerosis is rescued by ectopic expression of LONRF2. Our findings reveal that LONRF2 is a protein quality control ligase whose loss may contribute to MN degeneration and motor deficits.

Induced Pluripotent Stem Cells for Tissue-Engineered Skeletal Muscles

Skeletal muscle, which comprises a significant portion of the body, is responsible for vital functions such as movement, metabolism, and overall health. However, severe injuries often result in volumetric muscle loss (VML) and compromise the regenerative capacity of the muscle. Tissue-engineered muscles offer a potential solution to address lost or damaged muscle tissue, thereby restoring muscle function and improving patients' quality of life. Induced pluripotent stem cells (iPSCs) have emerged as a valuable cell source for muscle tissue engineering due to their pluripotency and self-renewal capacity, enabling the construction of tissue-engineered artificial skeletal muscles with applications in transplantation, disease modelling, and bio-hybrid robots. Next-generation iPSC-based models have the potential to revolutionize drug discovery by offering personalized muscle cells for testing, reducing reliance on animal models. This review provides a comprehensive overview of iPSCs in tissue-engineered artificial skeletal muscles, highlighting the advancements, applications, advantages, and challenges for clinical translation. We also discussed overcoming limitations and considerations in differentiation protocols, characterization methods, large-scale production, and translational regulations. By tackling these challenges, iPSCs can unlock transformative advancements in muscle tissue engineering and therapeutic interventions for the future.

Neural cell state shifts and fate loss in ageing and age-related diseases

Most age-related neurodegenerative diseases remain incurable owing to an incomplete understanding of the disease mechanisms. Several environmental and genetic factors contribute to disease onset, with human biological ageing being the primary risk factor. In response to acute cellular damage and external stimuli, somatic cells undergo state shifts characterized by temporal changes in their structure and function that increase their resilience, repair cellular damage, and lead to their mobilization to counteract the pathology. This basic cell biological principle also applies to human brain cells, including mature neurons that upregulate developmental features such as cell cycle markers or glycolytic reprogramming in response to stress. Although such temporary state shifts are required to sustain the function and resilience of the young human brain, excessive state shifts in the aged brain might result in terminal fate loss of neurons and glia, characterized by a permanent change in cell identity. Here, we offer a new perspective on the roles of cell states in sustaining health and counteracting disease, and we examine how cellular ageing might set the stage for pathological fate loss and neurodegeneration. A better understanding of neuronal state and fate shifts might provide the means for a controlled manipulation of cell fate to promote brain resilience and repair.

In Vitro Modeling as a Tool for Testing Therapeutics for Spinal Muscular Atrophy and IGHMBP2-Related Disorders

Spinal Muscular Atrophy (SMA) is the leading genetic cause of infant mortality. The most common form of SMA is caused by mutations in the SMN1 gene, located on 5q (SMA). On the other hand, mutations in IGHMBP2 lead to a large disease spectrum with no clear genotype-phenotype correlation, which includes Spinal Muscular Atrophy with Muscular Distress type 1 (SMARD1), an extremely rare form of SMA, and Charcot-Marie-Tooth 2S (CMT2S). We optimized a patient-derived in vitro model system that allows us to expand research on disease pathogenesis and gene function, as well as test the response to the AAV gene therapies we have translated to the clinic. We generated and characterized induced neurons (iN) from SMA and SMARD1/CMT2S patient cell lines. After establishing the lines, we treated the generated neurons with AAV9-mediated gene therapy (AAV9.SMN (Zolgensma) for SMA and AAV9.IGHMBP2 for IGHMBP2 disorders (NCT05152823)) to evaluate the response to treatment. The iNs of both diseases show a characteristic short neurite length and defects in neuronal conversion, which have been reported in the literature before with iPSC modeling. SMA iNs respond to treatment with AAV9.SMN in vitro, showing a partial rescue of the morphology phenotype. For SMARD1/CMT2S iNs, we were able to observe an improvement in the neurite length of neurons after the restoration of IGHMBP2 in all disease cell lines, albeit to a variable extent, with some lines showing better responses to treatment than others. Moreover, this protocol allowed us to classify a variant of uncertain significance on IGHMBP2 on a suspected SMARD1/CMT2S patient. This study will further the understanding of SMA, and SMARD1/CMT2S disease in particular, in the context of variable patient mutations, and might further the development of new treatments, which are urgently needed.

Merits and challenges of iPSC-derived organoids for clinical applications

Induced pluripotent stem cells (iPSCs) have entered an unprecedented state of development since they were first generated. They have played a critical role in disease modeling, drug discovery, and cell replacement therapy, and have contributed to the evolution of disciplines such as cell biology, pathophysiology of diseases, and regenerative medicine. Organoids, the stem cell-derived 3D culture systems that mimic the structure and function of organs in vitro, have been widely used in developmental research, disease modeling, and drug screening. Recent advances in combining iPSCs with 3D organoids are facilitating further applications of iPSCs in disease research. Organoids derived from embryonic stem cells, iPSCs, and multi-tissue stem/progenitor cells can replicate the processes of developmental differentiation, homeostatic self-renewal, and regeneration due to tissue damage, offering the potential to unravel the regulatory mechanisms of development and regeneration, and elucidate the pathophysiological processes involved in disease mechanisms. Herein, we have summarized the latest research on the production scheme of organ-specific iPSC-derived organoids, the contribution of these organoids in the treatment of various organ-related diseases, in particular their contribution to COVID-19 treatment, and have discussed the unresolved challenges and shortcomings of these models.

Spinal Cord Organoids to Study Motor Neuron Development and Disease

Motor neuron diseases (MNDs) are a heterogeneous group of disorders that affect the cranial and/or spinal motor neurons (spMNs), spinal sensory neurons and the muscular system. Although they have been investigated for decades, we still lack a comprehensive understanding of the underlying molecular mechanisms; and therefore, efficacious therapies are scarce. Model organisms and relatively simple two-dimensional cell culture systems have been instrumental in our current knowledge of neuromuscular disease pathology; however, in the recent years, human 3D in vitro models have transformed the disease-modeling landscape. While cerebral organoids have been pursued the most, interest in spinal cord organoids (SCOs) is now also increasing. Pluripotent stem cell (PSC)-based protocols to generate SpC-like structures, sometimes including the adjacent mesoderm and derived skeletal muscle, are constantly being refined and applied to study early human neuromuscular development and disease. In this review, we outline the evolution of human PSC-derived models for generating spMN and recapitulating SpC development. We also discuss how these models have been applied to exploring the basis of human neurodevelopmental and neurodegenerative diseases. Finally, we provide an overview of the main challenges to overcome in order to generate more physiologically relevant human SpC models and propose some exciting new perspectives.

Engineering a conduction-consistent cardiac patch with graphene oxide modified butterfly wings and human pluripotent stem cell-derived cardiomyocytes

Engineering a conduction-consistent cardiac patch has direct implications to biomedical research. However, there is difficulty in obtaining and maintaining a system that allows researchers to study physiologically relevant cardiac development, maturation, and drug screening due to the issues around inconsistent contractions of cardiomyocytes. Butterfly wings have special nanostructures arranged in parallel, which could help generate the alignment of cardiomyocytes to better mimic the natural heart tissue structure. Here, we construct a conduction-consistent human cardiac muscle patch by assembling human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) on graphene oxide (GO) modified butterfly wings. We also show this system functions as a versatile model to study human cardiomyogenesis by assembling human induced pluripotent stem cell-derived cardiac progenitor cells (hiPSC-CPCs) on the GO modified butterfly wings. The GO modified butterfly wing platform facilitated the parallel orientation of hiPSC-CMs, enhanced relative maturation as well as improved conduction consistency of the cardiomyocytes. In addition, GO modified butterfly wings enhanced the proliferation and maturation characteristics of the hiPSC-CPCs. In accordance with data obtained from RNA-sequencing and gene signatures, assembling hiPSC-CPCs on GO modified butterfly wings stimulated the differentiation of the progenitors into relatively mature hiPSC-CMs. These characteristics and capabilities of GO modified butterfly wings make them an ideal platform for heart research and drug screening.

Identifying altered developmental pathways in human globoid cell leukodystrophy iPSCs-derived NSCs using transcriptome profiling

BACKGROUND

Globoid cell leukodystrophy (GLD) is a devastating neurodegenerative disease characterized by widespread demyelination caused by galactocerebrosidase defects. Changes in GLD pathogenesis occurring at the molecular level have been poorly studied in human-derived neural cells. Patient-derived induced pluripotent stem cells (iPSCs) are a novel disease model for studying disease mechanisms and allow the generation of patient-derived neuronal cells in a dish.

RESULTS

In this study, we identified gene-expression changes in iPSCs and iPSC-derived neural stem cells (NSCs) from a patient with GLD (K-iPSCs/NSCs) and normal control (AF-iPSCs/NSCs), in order to investigate the potential mechanism underlying GLD pathogenesis. We identified 194 (K-iPSCs vs. AF-iPSCs) and 702 (K-NSCs vs. AF-NSCs) significantly dysregulated mRNAs when comparing the indicated groups. We also identified dozens of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway terms that were enriched for the differentially expressed genes. Among them, 25 differentially expressed genes identified by RNA-sequencing analysis were validated using real-time quantitative polymerase chain reaction analysis. Dozens of pathways involved in neuroactive ligand-receptor interactions, synaptic vesicle cycle signaling, serotonergic synapse signaling, phosphatidylinositol-protein kinase B signaling, and cyclic AMP signaling were identified as potential contributors to GLD pathogenesis.

CONCLUSIONS

Our results correspond to the fact that mutations in the galactosylceramidase gene may disrupt the identified signaling pathways during neural development, suggesting that alterations in signaling pathways contribute to GLD pathogenesis. At the same time, our results demonstrates that the model based on K-iPSCs is a novel tool that can be used to study the underlying molecular basis of GLD.

Modelling the erythroblastic island niche of dyserythropoietic anaemia type IV patients using induced pluripotent stem cells

Introduction: Congenital dyserythropoietic anaemia (CDA) type IV has been associated with an amino acid substitution, Glu325Lys (E325K), in the transcription factor KLF1. These patients present with a range of symptoms, including the persistence of nucleated red blood cells (RBCs) in the peripheral blood which reflects the known role for KLF1 within the erythroid cell lineage. The final stages of RBCs maturation and enucleation take place within the erythroblastic island (EBI) niche in close association with EBI macrophages. It is not known whether the detrimental effects of the E325K mutation in KLF1 are restricted to the erythroid lineage or whether deficiencies in macrophages associated with their niche also contribute to the disease pathology. Methods: To address this question, we generated an in vitro model of the human EBI niche using induced pluripotent stem cells (iPSCs) derived from one CDA type IV patient as well as two iPSC lines genetically modified to express an KLF1-E325K-ERT2 protein that could be activated with 4OH-tamoxifen. The one patient iPSC line was compared to control lines from two healthy donors and the KLF1-E325K-ERT2 iPSC line to one inducible KLF1-ERT2 line generated from the same parental iPSCS. Results: The CDA patient-derived iPSCs and iPSCs expressing the activated KLF1-E325K-ERT2 protein showed significant deficiencies in the production of erythroid cells with associated disruption of some known KLF1 target genes. Macrophages could be generated from all iPSC lines but when the E325K-ERT2 fusion protein was activated, we noted the generation of a slightly less mature macrophage population marked by CD93. A subtle trend in their reduced ability to support RBC enucleation was also associated with macrophages carrying the E325K-ERT2 transgene. Discussion: Taken together these data support the notion that the clinically significant effects of the KLF1-E325K mutation are primarily associated with deficiencies in the erythroid lineage but it is possible that deficiencies in the niche might have the potential to exacerbate the condition. The strategy we describe provides a powerful approach to assess the effects of other mutations in KLF1 as well as other factors associated with the EBI niche.

Comparative analysis of the cardiomyocyte differentiation potential of induced pluripotent stem cells reprogrammed from human atrial or ventricular fibroblasts

Background: We had shown that cardiomyocytes (CMs) were more efficiently differentiated from human induced pluripotent stem cells (hiPSCs) when the hiPSCs were reprogrammed from cardiac fibroblasts rather than dermal fibroblasts or blood mononuclear cells. Here, we continued to investigate the relationship between somatic-cell lineage and hiPSC-CM production by comparing the yield and functional properties of CMs differentiated from iPSCs reprogrammed from human atrial or ventricular cardiac fibroblasts (AiPSC or ViPSC, respectively). Methods: Atrial and ventricular heart tissues were obtained from the same patient, reprogrammed into AiPSCs or ViPSCs, and then differentiated into CMs (AiPSC-CMs or ViPSC-CMs, respectively) via established protocols. Results: The time-course of expression for pluripotency genes (OCT4, NANOG, and SOX2), the early mesodermal marker Brachyury, the cardiac mesodermal markers MESP1 and Gata4, and the cardiovascular progenitor-cell transcription factor NKX2.5 were broadly similar in AiPSC-CMs and ViPSC-CMs during the differentiation protocol. Flow-cytometry analyses of cardiac troponin T expression also indicated that purity of the two differentiated hiPSC-CM populations (AiPSC-CMs: 88.23% ± 4.69%, ViPSC-CMs: 90.25% ± 4.99%) was equivalent. While the field-potential durations were significantly longer in ViPSC-CMs than in AiPSC-CMs, measurements of action potential duration, beat period, spike amplitude, conduction velocity, and peak calcium-transient amplitude did not differ significantly between the two hiPSC-CM populations. Yet, our cardiac-origin iPSC-CM showed higher ADP and conduction velocity than previously reported iPSC-CM derived from non-cardiac tissues. Transcriptomic data comparing iPSC and iPSC-CMs showed similar gene expression profiles between AiPSC-CMs and ViPSC-CMs with significant differences when compared to iPSC-CM derived from other tissues. This analysis also pointed to several genes involved in electrophysiology processes responsible for the physiological differences observed between cardiac and non-cardiac-derived cardiomyocytes. Conclusion: AiPSC and ViPSC were differentiated into CMs with equal efficiency. Detected differences in electrophysiological properties, calcium handling activity, and transcription profiles between cardiac and non-cardiac derived cardiomyocytes demonstrated that 1) tissue of origin matters to generate a better-featured iPSC-CMs, 2) the sublocation within the cardiac tissue has marginal effects on the differentiation process.

Reprogramming of adult human dermal fibroblasts to induced dorsal forebrain precursor cells maintains aging signatures

Introduction: With the increase in aging populations around the world, the development of in vitro human cell models to study neurodegenerative disease is crucial. A major limitation in using induced pluripotent stem cell (hiPSC) technology to model diseases of aging is that reprogramming fibroblasts to a pluripotent stem cell state erases age-associated features. The resulting cells show behaviors of an embryonic stage exhibiting longer telomeres, reduced oxidative stress, and mitochondrial rejuvenation, as well as epigenetic modifications, loss of abnormal nuclear morphologies, and age-associated features. Methods: We have developed a protocol utilizing stable, non-immunogenic chemically modified mRNA (cmRNA) to convert adult human dermal fibroblasts (HDFs) to human induced dorsal forebrain precursor (hiDFP) cells, which can subsequently be differentiated into cortical neurons. Analyzing an array of aging biomarkers, we demonstrate for the first time the effect of direct-to-hiDFP reprogramming on cellular age. Results: We confirm direct-to-hiDFP reprogramming does not affect telomere length or the expression of key aging markers. However, while direct-to-hiDFP reprogramming does not affect senescence-associated β-galactosidase activity, it enhances the level of mitochondrial reactive oxygen species and the amount of DNA methylation compared to HDFs. Interestingly, following neuronal differentiation of hiDFPs we observed an increase in cell soma size as well as neurite number, length, and branching with increasing donor age suggesting that neuronal morphology is altered with age. Discussion: We propose direct-to-hiDFP reprogramming provides a strategy for modeling age-associated neurodegenerative diseases allowing the persistence of age-associated signatures not seen in hiPSC-derived cultures, thereby facilitating our understanding of neurodegenerative disease and identification of therapeutic targets.

NeuroLINCS Proteomics: Defining human-derived iPSC proteomes and protein signatures of pluripotency

The National Institute of Health (NIH) Library of integrated network-based cellular signatures (LINCS) program is premised on the generation of a publicly available data resource of cell-based biochemical responses or "signatures" to genetic or environmental perturbations. NeuroLINCS uses human inducible pluripotent stem cells (hiPSCs), derived from patients and healthy controls, and differentiated into motor neuron cell cultures. This multi-laboratory effort strives to establish i) robust multi-omic workflows for hiPSC and differentiated neuronal cultures, ii) public annotated data sets and iii) relevant and targetable biological pathways of spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). Here, we focus on the proteomics and the quality of the developed workflow of hiPSC lines from 6 individuals, though epigenomics and transcriptomics data are also publicly available. Known and commonly used markers representing 73 proteins were reproducibly quantified with consistent expression levels across all hiPSC lines. Data quality assessments, data levels and metadata of all 6 genetically diverse human iPSCs analysed by DIA-MS are parsable and available as a high-quality resource to the public.

iPSCs-Derived Neurons and Brain Organoids from Patients

Induced pluripotent stem cells (iPSCs) can be differentiated into specific neurons and brain organoids by adding induction factors and small molecules in vitro, which carry human genetic information and recapitulate the development process of human brain as well as physiological, pathological, and pharmacological characteristics. Hence, iPSC-derived neurons and organoids hold great promise for studying human brain development and related nervous system diseases in vitro, and provide a platform for drug screening. In this chapter, we summarize the development of the differentiation techniques for neurons and brain organoids from iPSCs, and their applications in studying brain disease, drug screening, and transplantation.

Using Human iPSC-Derived Peripheral Nervous System Disease Models for Drug Discovery

Induced pluripotent stem cells (IPSCs), with their remarkable ability to differentiate into various cell types, including peripheral nervous system cells such as neurons and glial cells, offer an excellent platform for in vitro disease modeling. These iPSC-derived disease models have proven valuable in drug discovery, as they provide more precise simulations of a patient's disease state and allow for the assessment of potential therapeutic effectiveness and safety.

Induced pluripotent stem cell for modeling Pompe disease

Pompe disease (PD) is a rare, autosomal recessive, inherited, and progressive metabolic disorder caused by α-glucosidase defect in lysosomes, resulting in abnormal glycogen accumulation. Patients with PD characteristically have multisystem pathological disorders, particularly hypertrophic cardiomyopathy, muscle weakness, and hepatomegaly. Although the pathogenesis and clinical outcomes of PD are well-established, disease-modeling ability, mechanism elucidation, and drug development targeting PD have been substantially limited by the unavailable PD-relevant cell models. This obstacle has been overcome with the help of induced pluripotent stem cell (iPSC) reprogramming technology, thus providing a powerful tool for cell replacement therapy, disease modeling, drug screening, and drug toxicity assessment. This review focused on the exciting achievement of PD disease modeling and mechanism exploration using iPSC.

The Role of Bone Morphogenetic Protein Receptor Type 2 (BMPR2) and the Prospects of Utilizing Induced Pluripotent Stem Cells (iPSCs) in Pulmonary Arterial Hypertension Disease Modeling

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by increased pulmonary vascular resistance (PVR), causing right ventricular hypertrophy and ultimately death from right heart failure. Heterozygous mutations in the bone morphogenetic protein receptor type 2 (BMPR2) are linked to approximately 80% of hereditary, and 20% of idiopathic PAH cases, respectively. While patients carrying a BMPR2 gene mutation are more prone to develop PAH than non-carriers, only 20% will develop the disease, whereas the majority will remain asymptomatic. PAH is characterized by extreme vascular remodeling that causes pulmonary arterial endothelial cell (PAEC) dysfunction, impaired apoptosis, and uncontrolled proliferation of the pulmonary arterial smooth muscle cells (PASMCs). To date, progress in understanding the pathophysiology of PAH has been hampered by limited access to human tissue samples and inadequacy of animal models to accurately mimic the pathogenesis of human disease. Along with the advent of induced pluripotent stem cell (iPSC) technology, there has been an increasing interest in using this tool to develop patient-specific cellular models that precisely replicate the pathogenesis of PAH. In this review, we summarize the currently available approaches in iPSC-based PAH disease modeling and explore how this technology could be harnessed for drug discovery and to widen our understanding of the pathophysiology of PAH.

Translational potential of hiPSCs in predictive modeling of heart development and disease

Congenital heart disease (CHD) represents a major class of birth defects worldwide and is associated with cardiac malformations that often require surgical intervention immediately after birth. Despite the intense efforts from multicentric genome/exome sequencing studies that have identified several genetic variants, the etiology of CHD remains diverse and often unknown. Genetically modified animal models with candidate gene deficiencies continue to provide novel molecular insights that are responsible for fetal cardiac development. However, the past decade has seen remarkable advances in the field of human induced pluripotent stem cell (hiPSC)-based disease modeling approaches to better understand the development of CHD and discover novel preventative therapies. The iPSCs are derived from reprogramming of differentiated somatic cells to an embryonic-like pluripotent state via overexpression of key transcription factors. In this review, we describe how differentiation of hiPSCs to specialized cardiac cellular identities facilitates our understanding of the development and pathogenesis of CHD subtypes. We summarize the molecular and functional characterization of hiPSC-derived differentiated cells in support of normal cardiogenesis, those that go awry in CHD and other heart diseases. We illustrate how stem cell-based disease modeling enables scientists to dissect the molecular mechanisms of cell-cell interactions underlying CHD. We highlight the current state of hiPSC-based studies that are in the verge of translating into clinical trials. We also address limitations including hiPSC-model reproducibility and scalability and differentiation methods leading to cellular heterogeneity. Last, we provide future perspective on exploiting the potential of hiPSC technology as a predictive model for patient-specific CHD, screening pharmaceuticals, and provide a source for cell-based personalized medicine. In combination with existing clinical and animal model studies, data obtained from hiPSCs will yield further understanding of oligogenic, gene-environment interaction, pathophysiology, and management for CHD and other genetic cardiac disorders.

Metabolic Profile Variations along the Differentiation of Human-Induced Pluripotent Stem Cells to Dopaminergic Neurons

In recent years, the availability of induced pluripotent stem cell-based neuronal models has opened new perspectives on the study and therapy of neurological diseases such as Parkinson’s disease. In particular, P. Zhang set up a protocol to efficiently generate dopaminergic neurons from induced pluripotent stem cells. Although the differentiation process of these cells has been widely investigated, there is scant information related to the variation in metabolic features during the differentiation process of pluripotent stem cells to mature dopaminergic neurons. For this reason, we analysed the metabolic profile of induced pluripotent stem cells, neuronal precursors and mature neurons by liquid chromatography–tandem mass spectrometry. We found that induced pluripotent stem cells primarily rely on fatty acid beta-oxidation as a fuel source. Upon progression to neuronal progenitors, it was observed that cells began to shut down fatty acid β-oxidation and preferentially catabolised glucose, which is the principal source of energy in fully differentiated neurons. Interestingly, in neuronal precursors, we observed an increase in amino acids that are likely the result of increased uptake or synthesis, while in mature dopaminergic neurons, we also observed an augmented content of those amino acids needed for dopamine synthesis. In summary, our study highlights a metabolic rewiring occurring during the differentiation stages of dopaminergic neurons.

The Proteome Signatures of Fibroblasts from Patients with Severe, Intermediate and Mild Spinal Muscular Atrophy Show Limited Overlap

Most research to characterise the molecular consequences of spinal muscular atrophy (SMA) has focused on SMA I. Here, proteomic profiling of skin fibroblasts from severe (SMA I), intermediate (SMA II), and mild (SMA III) patients, alongside age-matched controls, was conducted using SWATH mass spectrometry analysis. Differentially expressed proteomic profiles showed limited overlap across each SMA type, and variability was greatest within SMA II fibroblasts, which was not explained by SMN2 copy number. Despite limited proteomic overlap, enriched canonical pathways common to two of three SMA severities with at least one differentially expressed protein from the third included mTOR signalling, regulation of eIF2 and eIF4 signalling, and protein ubiquitination. Network expression clustering analysis identified protein profiles that may discriminate or correlate with SMA severity. From these clusters, the differential expression of PYGB (SMA I), RAB3B (SMA II), and IMP1 and STAT1 (SMA III) was verified by Western blot. All SMA fibroblasts were transfected with an SMN-enhanced construct, but only RAB3B expression in SMA II fibroblasts demonstrated an SMN-dependent response. The diverse proteomic profiles and pathways identified here pave the way for studies to determine their utility as biomarkers for patient stratification or monitoring treatment efficacy and for the identification of severity-specific treatments.

Perspectives on current models of Friedreich’s ataxia

Friedreich’s ataxia (FRDA, OMIM#229300) is the most common hereditary ataxia, resulting from the reduction of frataxin protein levels due to the expansion of GAA repeats in the first intron of the FXN gene. Why the triplet repeat expansion causes a decrease in Frataxin protein levels is not entirely known. Generation of effective FRDA disease models is crucial for answering questions regarding the pathophysiology of this disease. There have been considerable efforts to generate in vitro and in vivo models of FRDA. In this perspective article, we highlight studies conducted using FRDA animal models, patient-derived materials, and particularly induced pluripotent stem cell (iPSC)-derived models. We discuss the current challenges in using FRDA animal models and patient-derived cells. Additionally, we provide a brief overview of how iPSC-based models of FRDA were used to investigate the main pathways involved in disease progression and to screen for potential therapeutic agents for FRDA. The specific focus of this perspective article is to discuss the outlook and the remaining challenges in the context of FRDA iPSC-based models.

Assessing the consistency of iPSC and animal models in cystic fibrosis modelling: A meta-analysis

INTRODUCTION

Cystic fibrosis (CF) is a hereditary autosomal recessive disorder caused by a range of mutations in the CF Transmembrane Conductance Regulator (CFTR) gene. This gene encodes the CFTR protein, which acts as a chloride channel activated by cyclic AMP (cAMP). This meta-analysis aimed to compare the responsiveness of induced pluripotent stem cells (iPSCs) to cAMP analogues to that of commonly used animal models.

METHODS

Databases searched included PubMed, Scopus, and Medline from inception to January 2020. A total of 8 and 3 studies, respectively, for animal models and iPSCs, were analyzed. Studies were extracted for investigating cAMP-stimulated anion transport by measuring the short circuit current (Isc) of chloride channels in different animal models and iPSC systems We utilized an inverse variance heterogeneity model for synthesis.

RESULTS

Our analysis showed considerable heterogeneity in the mean Isc value in both animal models and iPSCs studies (compared to their WT counterparts), and both suffer from variable responsiveness based on the nature of the underlying model. There was no clear advantage of one over the other.

CONCLUSIONS

Studies on both animal and iPSCs models generated considerable heterogeneity. Given the potential of iPSC-derived models to study different diseases, we recommend paying more attention to developing reproducible models of iPSC as it has potential if adequately developed.

Changing Fate: Reprogramming Cells via Engineered Nanoscale Delivery Materials

The incorporation of nanotechnology in regenerative medicine is at the nexus of fundamental innovations and early-stage breakthroughs, enabling exciting biomedical advances. One of the most exciting recent developments is the use of nanoscale constructs to influence the fate of cells, which are the basic building blocks of healthy function. Appropriate cell types can be effectively manipulated by direct cell reprogramming; a robust technique to manipulate cellular function and fate, underpinning burgeoning advances in drug delivery systems, regenerative medicine, and disease remodeling. Individual transcription factors, or combinations thereof, can be introduced into cells using both viral and nonviral delivery systems. Existing approaches have inherent limitations. Viral-based tools include issues of viral integration into the genome of the cells, the propensity for uncontrollable silencing, reduced copy potential and cell specificity, and neutralization via the immune response. Current nonviral cell reprogramming tools generally suffer from inferior expression efficiency. Nanomaterials are increasingly being explored to address these challenges and improve the efficacy of both viral and nonviral delivery because of their unique properties such as small size and high surface area. This review presents the state-of-the-art research in cell reprogramming, focused on recent breakthroughs in the deployment of nanomaterials as cell reprogramming delivery tools.

Nitric Oxide Attenuates Human Cytomegalovirus Infection yet Disrupts Neural Cell Differentiation and Tissue Organization

Human cytomegalovirus (HCMV) is a prevalent betaherpesvirus that is asymptomatic in healthy individuals but can cause serious disease in immunocompromised patients. HCMV is also the leading cause of virus-mediated birth defects. Many of these defects manifest within the central nervous system and include microcephaly, sensorineural hearing loss, and cognitive developmental delays. Nitric oxide is a critical effector molecule produced as a component of the innate immune response during infection. Congenitally infected fetal brains show regions of brain damage, including necrotic foci with infiltrating macrophages and microglia, cell types that produce nitric oxide during infection. Using a 3-dimensional cortical organoid model, we demonstrate that nitric oxide inhibits HCMV spread and simultaneously disrupts neural rosette structures, resulting in tissue disorganization. Nitric oxide also attenuates HCMV replication in 2-dimensional cultures of neural progenitor cells (NPCs), a prominent cell type in cortical organoids that differentiate into neurons and glial cells. The multipotency factor SOX2 was decreased during nitric oxide exposure, suggesting that early neural differentiation is affected. Nitric oxide also reduced maximal mitochondrial respiration in both uninfected and infected NPCs. We determined that this reduction likely influences neural differentiation, as neurons (Tuj1⁺ GFAP^- Nestin^-) and glial populations (Tuj1^- GFAP⁺ Nestin^-) were reduced following differentiation. Our studies indicate a prominent, immunopathogenic role of nitric oxide in promoting developmental defects within the brain despite its antiviral activity during congenital HCMV infection. IMPORTANCE Human cytomegalovirus (HCMV) is the leading cause of virus-mediated congenital birth defects. Congenitally infected infants can have a variety of symptoms manifesting within the central nervous system. The use of 3-dimensional (3-D) cortical organoids to model infection of the fetal brain has advanced the current understanding of development and allowed broader investigation of the mechanisms behind disease. However, the impact of the innate immune molecule nitric oxide during HCMV infection has not been explored in neural cells or cortical 3-D models. Here, we investigated the effect of nitric oxide on cortical development during HCMV infection. We demonstrate that nitric oxide plays an antiviral role during infection yet results in disorganized cortical tissue. Nitric oxide contributes to differentiation defects of neuron and glial cells from neural progenitor cells despite inhibiting viral replication. Our results indicate that immunopathogenic consequences of nitric oxide during congenital infection promote developmental defects that undermine its antiviral activity.

The CARM1 transcriptome and arginine methylproteome mediate skeletal muscle integrative biology

OBJECTIVE

Coactivator-associated arginine methyltransferase 1 (CARM1) catalyzes the methylation of arginine residues on target proteins to regulate critical processes in health and disease. A mechanistic understanding of the role(s) of CARM1 in skeletal muscle biology is only gradually emerging. The purpose of this study was to elucidate the function of CARM1 in regulating the maintenance and plasticity of skeletal muscle.

METHODS

We used transcriptomic, methylproteomic, molecular, functional, and integrative physiological approaches to determine the specific impact of CARM1 in muscle homeostasis.

RESULTS

Our data defines the occurrence of arginine methylation in skeletal muscle and demonstrates that this mark occurs on par with phosphorylation and ubiquitination. CARM1 skeletal muscle-specific knockout (mKO) mice displayed altered transcriptomic and arginine methylproteomic signatures with molecular and functional outcomes confirming remodeled skeletal muscle contractile and neuromuscular junction characteristics, which presaged decreased exercise tolerance. Moreover, CARM1 regulates AMPK-PGC-1α signalling during acute conditions of activity-induced muscle plasticity.

CONCLUSIONS

This study uncovers the broad impact of CARM1 in the maintenance and remodelling of skeletal muscle biology.

SMN Enhances Pluripotent Genes Expression and Facilitates Cell Reprogramming

Survival motor neuron (SMN) plays important roles in snRNPs assembly and mRNA splicing. Deficiency of SMN causes spinal muscular atrophy (SMA), a leading genetic disease of childhood mortality. Previous studies have shown that SMN regulates stem cell self-renewal and pluripotency in Drosophila and in mouse, and is abundantly expressed in mouse embryonic stem cells (ESCs). However, whether SMN is required for the establishment of pluripotency is unclear. Herein, we show that SMN is gradually upregulated in pre-implantation mouse embryos and cultured cells undergoing cell reprogramming. Ectopic expression of SMN increased the cell reprogramming efficiency, whereas knockdown of SMN impeded iPSC colony formation. iPSCs could be derived from SMA model mice, but certain impairment in differentiation capacity may present. The ectopic overexpression of SMN in iPSCs can upregulate the expression levels of some pluripotent genes and restore the neuronal differentiation capacity of SMA-iPSCs. Taken together, our findings not only demonstrate the functional relevance of SMN and the establishment of cell pluripotency, but also propose its potential application in facilitating iPSC derivation.

High-throughput "read-on-ski" automated imaging and label-free detection system for toxicity screening of compounds using personalised human kidney organoids

Organoid models are used to study kidney physiology, such as the assessment of nephrotoxicity and underlying disease processes. Personalized human pluripotent stem cell-derived kidney organoids are ideal models for compound toxicity studies, but there is a need to accelerate basic and translational research in the field. Here, we developed an automated continuous imaging setup with the "read-on-ski" law of control to maximize temporal resolution with minimum culture plate vibration. High-accuracy performance was achieved: organoid screening and imaging were performed at a spatial resolution of 1.1 μm for the entire multi-well plate under 3 min. We used the in-house developed multi-well spinning device and cisplatin-induced nephrotoxicity model to evaluate the toxicity in kidney organoids using this system. The acquired images were processed via machine learning-based classification and segmentation algorithms, and the toxicity in kidney organoids was determined with 95% accuracy. The results obtained by the automated "read-on-ski" imaging device, combined with label-free and non-invasive algorithms for detection, were verified using conventional biological procedures. Taking advantage of the close-to-in vivo-kidney organoid model, this new development opens the door for further application of scaled-up screening using organoids in basic research and drug discovery.

"Cutting the Mustard" with Induced Pluripotent Stem Cells: An Overview and Applications in Healthcare Paradigm

Treatment of numerous ailments has been made accessible by the advent of genetic engineering, where the self-renewal property has unfolded the mysteries of regeneration, i.e., stem cells. This is narrowed down to pluripotency, the cell property of differentiating into other adult cells. The generation of induced pluripotent stem cells (iPSCs) was a major breakthrough in 2006, which was generated by a cocktail of 4 Yamanaka Factors, following which significant advancements have been reported in medical science and therapeutics. The iPSCs are reprogrammed from somatic cells, and the fascinating results focused on developing authentic techniques for their generation via molecular reprogramming mechanisms, with a plethora of molecules, like NANOG, miRNAs, and DNA modifying agents, etc. The iPSCs have exhibited reliable results in assessing the etiology and molecular mechanisms of diseases, followed by the development of possible treatments and the elimination of risks of immune rejection. The authors formulate a comprehensive review to develop a clear understanding of iPSC generation, their advantages and limitations, with potential challenges associated with their medical utility. In addition, a wide compendium of applications of iPSCs in regenerative medicine and disease modeling has been discussed, alongside bioengineering technologies for iPSC reprogramming, expansion, isolation, and differentiation. The manuscript aims to provide a holistic picture of the booming advancement of iPSC therapy, to attract the attention of global researchers, to investigate this versatile approach in treatment of multiple disorders, subsequently overcoming the challenges, in order to effectively expand its therapeutic window.

Skeletal Muscle Cells Derived from Induced Pluripotent Stem Cells: A Platform for Limb Girdle Muscular Dystrophies

Limb girdle muscular dystrophies (LGMD), caused by mutations in 29 different genes, are the fourth most prevalent group of genetic muscle diseases. Although the link between LGMD and its genetic origins has been determined, LGMD still represent an unmet medical need. Here, we describe a platform for modeling LGMD based on the use of human induced pluripotent stem cells (hiPSC). Thanks to the self-renewing and pluripotency properties of hiPSC, this platform provides a renewable and an alternative source of skeletal muscle cells (skMC) to primary, immortalized, or overexpressing cells. We report that skMC derived from hiPSC express the majority of the genes and proteins that cause LGMD. As a proof of concept, we demonstrate the importance of this cellular model for studying LGMDR9 by evaluating disease-specific phenotypes in skMC derived from hiPSC obtained from four patients.

Utility of iPSC-Derived Cells for Disease Modeling, Drug Development, and Cell Therapy

The advent of induced pluripotent stem cells (iPSCs) has advanced our understanding of the molecular mechanisms of human disease, drug discovery, and regenerative medicine. As such, the use of iPSCs in drug development and validation has shown a sharp increase in the past 15 years. Furthermore, many labs have been successful in reproducing many disease phenotypes, often difficult or impossible to capture, in commonly used cell lines or animal models. However, there still remain limitations such as the variability between iPSC lines as well as their maturity. Here, we aim to discuss the strategies in generating iPSC-derived cardiomyocytes and neurons for use in disease modeling, drug development and their use in cell therapy.