Embryonic stem cell lines derived from human blastocysts

Generation, interrogation, and future applications of microglia-containing brain organoids

Brain organoids encompass a large collection of in vitro stem cell-derived 3D culture systems that aim to recapitulate multiple aspects of in vivo brain development and function. First, this review provides a brief introduction to the current state-of-the-art for neuro-ectoderm brain organoid development, emphasizing their biggest advantages in comparison with classical two-dimensional cell cultures and animal models. However, despite their usefulness for developmental studies, a major limitation for most brain organoid models is the absence of contributing cell types from endodermal and mesodermal origin. As such, current research is highly investing towards the incorporation of a functional vasculature and the microglial immune component. In this review, we will specifically focus on the development of immune-competent brain organoids. By summarizing the different approaches applied to incorporate microglia, it is highlighted that immune-competent brain organoids are not only important for studying neuronal network formation, but also offer a clear future as a new tool to study inflammatory responses in vitro in 3D in a brain-like environment. Therefore, our main focus here is to provide a comprehensive overview of assays to measure microglial phenotype and function within brain organoids, with an outlook on how these findings could better understand neuronal network development or restoration, as well as the influence of physical stress on microglia-containing brain organoids. Finally, we would like to stress that even though the development of immune-competent brain organoids has largely evolved over the past decade, their full potential as a pre-clinical tool to study novel therapeutic approaches to halt or reduce inflammation-mediated neurodegeneration still needs to be explored and validated.

A systematic review of progenitor survival and maturation in Parkinsonian models

Stem cell-based brain repair is a promising emergent therapy for Parkinson's disease based on years of foundational research using human fetal donors as a cell source. Unlike current therapeutic options for patients, this approach has the potential to provide long-term stem cell-derived reconstruction and restoration of the dopaminergic input to denervated regions of the brain allowing for restoration of certain functions to patients. The ultimate clinical success of stem cell-derived brain repair will depend on both the safety and efficacy of the approach and the latter is dependent on the ability of the transplanted cells to survive and differentiate into functional dopaminergic neurons in the Parkinsonian brain. Because the pre-clinical literature suggests that there is considerable variability in survival and differentiation between studies, the aim of this systematic review was to assess these parameters in human stem cell-derived dopaminergic progenitor transplant studies in animal models of Parkinson's disease. A defined systematic search of the PubMed database was completed to identify relevant studies published up to March 2024. After screening, 76 articles were included in the analysis from which 178 separate transplant studies were identified. From these, graft survival could be assessed in 52 studies and differentiation in 129 studies. Overall, we found that graft survival ranged from < 1% to 500% of cells transplanted, with a median of 51% of transplanted cells surviving in the brain; while dopaminergic differentiation of the cells ranged from 0% to 46% of cells transplanted with a median of 3%. This systematic review suggests that there is considerable scope for improvement in the differentiation of stem cell-derived dopaminergic progenitors to maximize the therapeutic potential of this approach for patients.

Therapeutic potential of stem cell-derived somatic cells to treat metabolic dysfunction-associated steatotic liver disease and diabetes

Developments in basic stem cell biology have paved the way for technology translation in human medicine. An exciting prospective use of stem cells is the ex vivo generation of hepatic and pancreatic endocrine cells for biomedical applications. This includes creating novel models 'in a dish' and developing therapeutic strategies for complex diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD) and diabetes. In this review, we explore recent advances in the generation of stem cell-derived hepatocyte-like cells and insulin-producing β-like cells. We cover the different differentiation strategies, new discoveries, and the caveats that still exist regarding their routine use. Finally, we discuss the challenges and limitations of stem cell-derived therapies as a clinical strategy to manage metabolic diseases in humans.

An overview of stem cells and cell products involved in trauma injury

Trauma injuries represent a significant public health burden worldwide, often leading to long-term disability and reduced quality of life. This review provides a comprehensive overview of the therapeutic potential of stem cells and cell products for traumatic injuries. The extraordinary characteristics of stem cells, such as self-renewal and transdifferentiation, make them definitive candidates for tissue regeneration. Mesenchymal stem cells (MSCs), neural stem cells (NSCs), and hematopoietic stem cells (HSCs) have been tested in preclinical studies for treating distinct traumatic injuries. Stem cell mechanisms of action are addressed through paracrine signaling, immunomodulation, differentiation, and neuroprotection. Cell products such as conditioned media, exosomes, and secretomes offer cell-free resources, thereby avoiding the risks of live cell transplantation. Clinical trials have reported many effective outcomes; however, variability exists across trauma types. Some challenges include tumorigenicity, standardized protocols, and regulatory issues. Collaboration and interdisciplinary research are being conducted to harness stem cells and products for trauma treatment. This emerging field is promising for improving patient recovery and quality of life after traumatic injuries.

Advances in human induced pluripotent stem cell (hiPSC)-based disease modelling in cardiogenetics

Human induced pluripotent stem cell (hiPSC)-based disease modelling has significantly advanced the field of cardiogenetics, providing a precise, patient-specific platform for studying genetic causes of heart diseases. Coupled with genome editing technologies such as CRISPR/Cas, hiPSC-based models not only allow the creation of isogenic lines to study mutation-specific cardiac phenotypes, but also enable the targeted modulation of gene expression to explore the effects of genetic and epigenetic deficits at the cellular and molecular level. hiPSC-based models of heart disease range from two-dimensional cultures of hiPSC-derived cardiovascular cell types, such as various cardiomyocyte subtypes, endothelial cells, pericytes, vascular smooth muscle cells, cardiac fibroblasts, immune cells, etc., to cardiac tissue cultures including organoids, microtissues, engineered heart tissues, and microphysiological systems. These models are further enhanced by multi-omics approaches, integrating genomic, transcriptomic, epigenomic, proteomic, and metabolomic data to provide a comprehensive view of disease mechanisms. In particular, advances in cardiovascular tissue engineering enable the development of more physiologically relevant systems that recapitulate native heart architecture and function, allowing for more accurate modelling of cardiac disease, drug screening, and toxicity testing, with the overall goal of personalised medical approaches, where therapies can be tailored to individual genetic profiles. Despite significant progress, challenges remain in the maturation of hiPSC-derived cardiomyocytes and the complexity of reproducing adult heart conditions. Here, we provide a concise update on the most advanced methods of hiPSC-based disease modelling in cardiogenetics, with a focus on genome editing and cardiac tissue engineering.

Cartilage repair: unleashing PRP's potential in organoid models

Platelet-rich plasma (PRP) has emerged as a promising biological therapy in regenerative medicine due to its high concentration of growth factors and cytokines, which promote tissue healing and regeneration. In recent years, its application in cartilage tissue engineering has garnered significant attention. This study explores the synergistic interaction between PRP and cartilage organoids, a novel three-dimensional in vitro culture system that closely mimics the structural and functional properties of native cartilage. Cartilage organoids serve as a physiologically relevant model for studying cartilage development, disease progression, and regeneration. By integrating PRP with cartilage organoids, this review aims to enhance chondrogenesis, extracellular matrix synthesis, and cellular proliferation within the organoids. Emerging evidence suggests that PRP supplementation significantly improves chondrocyte viability, growth, and differentiation in cartilage organoids, thereby accelerating their maturation. This combination holds great potential for advancing cartilage repair strategies, providing a robust platform for preclinical studies, and paving the way for innovative therapeutic approaches for cartilage-related injuries and degenerative diseases. These key aspects-chondrogenesis, matrix synthesis, and cellular proliferation-were specifically selected due to their fundamental roles in cartilage tissue engineering and regeneration. Chondrogenesis is crucial for chondrocyte differentiation and maintenance, matrix synthesis ensures the structural integrity and functional properties of regenerated cartilage, and cellular proliferation supports tissue viability and repair. Addressing these factors is essential, as current cartilage regeneration strategies often suffer from limited long-term efficacy and inadequate extracellular matrix production. By elucidating the synergistic effects of PRP and cartilage organoids in these areas, this study seeks to bridge existing knowledge gaps and provide valuable insights for improving regenerative approaches in clinical applications, particularly for osteoarthritis and cartilage defects.

Proteogenomic reprogramming to a functional human blastomere-like stem cell state via a PARP-DUX4 regulatory axis

Here, we show that conventional human pluripotent stem cells cultured with non-specific tankyrase-PARP1-inhibited conditions underwent proteogenomic reprogramming to functional blastomere-like tankyrase/PARP inhibitor-regulated naive stem cells (TIRN-SC). TIRN-SCs concurrently expressed hundreds of pioneer factors in hybrid 2C-8C-morula-ICM programs that were augmented by induced expression of DUX4. Injection of TIRN-SCs into 8C-staged murine embryos equipotently differentiated human cells to the extra-embryonic and embryonic compartments of chimeric blastocysts and fetuses. Ectopic expression of murine-E-Cadherin in TIRN-SCs further enhanced interspecific chimeric tissue targeting. TIRN-SC-derived trophoblast stem cells efficiently generated placental chimeras. Proteome-ubiquitinome analyses revealed increased TNKS and reduced PARP1 levels and an ADP-ribosylation-deficient, hyper-ubiquitinated proteome that impacted expression of both tankyrase and PARP1 substrates. ChIP-seq of NANOG-SOX2-OCT4 and PARP1 (NSOP) revealed genome-wide NSOP co-binding at DUX4-accessible enhancers of embryonic lineage factors; suggesting a DUX4-NSOP axis regulated TIRN-SC lineage plasticity. TIRN-SCs may serve as valuable models for studying the proteogenomic regulation of pre-lineage human embryogenesis. VIDEO ABSTRACT.

Advances in Islet Transplantation and the Future of Stem Cell-Derived Islets to Treat Diabetes

β-Cell replacement for type 1 diabetes (T1D) can restore normal glucose homeostasis, thereby eliminating the need for exogenous insulin and halting the progression of diabetes complications. Success in achieving insulin independence following transplantation of cadaveric islets fueled academic and industry efforts to develop techniques to mass produce β cells from human pluripotent stem cells, and these have now been clinically validated as an alternative source of regulated insulin production. Various encapsulation strategies are being pursued to contain implanted cells in a retrievable format, and different implant sites are being explored with some strategies reaching clinical studies. Stem cell lines, whether derived from embryonic sources or reprogrammed somatic cells, are being genetically modified for designer features, including immune evasiveness to enable implant without the use of chronic immunosuppression. Although hurdles remain in optimizing large-scale manufacturing, demonstrating efficacy, durability, and safety, products containing stem cell-derived β cells promise to provide a potent treatment for insulin-dependent diabetes.

Emerging brain organoids: 3D models to decipher, identify and revolutionize brain

Brain organoids are an emerging in vitro 3D brain model that is integrated from pluripotent stem cells. This model mimics the human brain's developmental process and disease-related phenotypes to a certain extent while advancing the development of human brain-based biological intelligence. However, many limitations of brain organoid culture (e.g., lacking a functional vascular system, etc.) prevent in vitro-cultured organoids from truly replicating the human brain in terms of cell type and structure. To improve brain organoids' scalability, efficiency, and stability, this paper discusses important contributions of material biology and microprocessing technology in solving the related limitations of brain organoids and applying the latest imaging technology to make real-time imaging of brain organoids possible. In addition, the related applications of brain organoids, especially the development of organoid intelligence combined with artificial intelligence, are analyzed, which will help accelerate the rational design and guidance of brain organoids.

Tissue Engineering and Regenerative Medicine: Perspectives and Challenges

From the pioneering days of cell therapy to the achievement of bioprinting organs, tissue engineering, and regenerative medicine have seen tremendous technological advancements, offering solutions for restoring damaged tissues and organs. However, only a few products and technologies have received United States Food and Drug Administration approval. This review highlights significant progress in cell therapy, extracellular vesicle-based therapy, and tissue engineering. Hematopoietic stem cell transplantation is a powerful tool for treating many diseases, especially hematological malignancies. Mesenchymal stem cells have been extensively studied. The discovery of induced pluripotent stem cells has revolutionized disease modeling and regenerative applications, paving the way for personalized medicine. Gene therapy represents an innovative approach to the treatment of genetic disorders. Additionally, extracellular vesicle-based therapies have emerged as rising stars, offering promising solutions in diagnostics, cell-free therapeutics, drug delivery, and targeted therapy. Advances in tissue engineering enable complex tissue constructs, further transforming the field. Despite these advancements, many technical, ethical, and regulatory challenges remain. This review addresses the current bottlenecks, emphasizing novel technologies and interdisciplinary research to overcome these hurdles. Standardizing practices and conducting clinical trials will balance innovation and regulation, improving patient outcomes and quality of life.

Modelling human brain development and disease with organoids

Organoids are systems derived from pluripotent stem cells at the interface between traditional monolayer cultures and in vivo animal models. The structural and functional characteristics of organoids enable the modelling of early stages of brain development in a physiologically relevant 3D environment. Moreover, organoids constitute a tool with which to analyse how individual genetic variation contributes to the susceptibility and progression of neurodevelopmental disorders. This Roadmap article describes the features of brain organoids, focusing on the neocortex, and their advantages and limitations - in comparison with other model systems - for the study of brain development, evolution and disease. We highlight avenues for enhancing the physiological relevance of brain organoids by integrating bioengineering techniques and unbiased high-throughput analyses, and discuss future applications. As organoids advance in mimicking human brain functions, we address the ethical and societal implications of this technology.

ATR regulates OCT4 phosphorylation and safeguards human naïve pluripotency

Under specific conditions, cultured human embryonic stem cells (hESCs) corresponding to primed post-implantation epiblasts can be converted back to a 'naïve pluripotency' state that resembles the pre-implantation epiblasts. The core pluripotency factor OCT4 is known to be crucial in regulating different states of pluripotency, but its potential regulatory role in human naïve pluripotency remains unexplored. In this study, we systematically mapped out phosphorylation sites in OCT4 protein that are differentially phosphorylated between two states of pluripotency, and further identified ATR as a key kinase that phosphorylated OCT4 in naïve but not primed hESCs. The kinase activity levels of ATR in naïve hESCs were higher than those in primed hESCs. Ablating cellular ATR activity significantly halted the induction of naïve hESCs from their primed counterparts, and increased early apoptotic death of naïve hESCs upon UV and CPT treatment. Thus, our work reveals the importance of ATR activity in safeguarding human naïve pluripotency, and implicates a potential association of OCT4 phosphorylation, DNA damage sensing and repairing system in regulating different states of pluripotency during early development.

Advantages and challenges of using allogeneic vs. autologous sources for neuronal cell replacement in Parkinson's disease: Insights from non-human primate studies

Intracerebral grafting of dopamine-producing cells is proposed as a strategy to replace the typical neurons lost to Parkinson's disease (PD) and improve PD motor symptoms. Non-human primate studies have provided clues on the relationship between the host's immune response and grafting success. Herein, we discuss how the host's immune system differentially affects the graft depending on the origin of the cells and reflect on the advantages and limitations of the immune paradigms utilized to assess graft-related outcomes. We also consider new strategies to minimize or circumvent the host's immunological response and related preclinical research needed to identify the most promising new approaches to be translated into the clinic.

Trials and tribulations of cell therapy for heart failure: an update on ongoing trials

Heart failure (HF) remains a leading cause of mortality, responsible for 13% of all deaths worldwide. The prognosis for patients with HF is poor, with only a 50% survival rate within 5 years. A major challenge of ischaemia-driven HF is the loss of cardiomyocytes, compounded by the minimal regenerative capacity of the adult heart. To date, replacement of irreversibly damaged heart muscle can only be achieved by complete heart transplantation. In the past 20 years, cell therapy has emerged and evolved as a promising avenue for cardiac repair and regeneration. During this time, cell therapy for HF has encountered substantial barriers in both preclinical studies and clinical trials but the field continues to progress and evolve from lessons learned from such research. In this Review, we provide an overview of ongoing trials of cell-based and cell product-based therapies for the treatment of HF. Findings from these trials will facilitate the clinical translation of cardiac regenerative and reparative therapies not only by evaluating the safety and efficacy of specific cell-based therapeutics but also by establishing the feasibility of novel or underexplored treatment protocols such as repeated intravenous dosing, personalized patient selection based on pharmacogenomics, systemic versus intramural cell delivery, and epicardial engraftment of engineered tissue products.

Moving toward totipotency: the molecular and cellular features of totipotent and naive pluripotent stem cells

BACKGROUND

Dissecting the key molecular mechanism of embryonic development provides novel insights into embryogenesis and potential intervention strategies for clinical practices. However, the ability to study the molecular mechanisms of early embryo development in humans, such as zygotic genome activation and lineage segregation, is meaningfully constrained by methodological limitations and ethical concerns. Totipotent stem cells have an extended developmental potential to differentiate into embryonic and extraembryonic tissues, providing a suitable model for studying early embryo development. Recently, a series of ground-breaking results on stem cells have identified totipotent-like cells or induced pluripotent stem cells into totipotent-like cells.

OBJECTIVE AND RATIONALE

This review followed the PRISMA guidelines, surveys the current works of literature on totipotent, naive, and formative pluripotent stem cells, introduces the molecular and biological characteristics of those stem cells, and gives advice for future research.

SEARCH METHODS

The search method employed the terms 'totipotent' OR 'naive pluripotent stem cell' OR 'formative pluripotent stem cell' for unfiltered search on PubMed, Web of Science, and Cochrane Library. Papers included were those with information on totipotent stem cells, naive pluripotent stem cells, or formative pluripotent stem cells until June 2024 and were published in the English language. Articles that have no relevance to stem cells, or totipotent, naive pluripotent, or formative pluripotent cells were excluded.

OUTCOMES

There were 152 records included in this review. These publications were divided into four groups according to the species of the cells included in the studies: 67 human stem cell studies, 70 mouse stem cell studies, 9 porcine stem cell studies, and 6 cynomolgus stem cell studies. Naive pluripotent stem cell models have been established in other species such as porcine and cynomolgus. Human and mouse totipotent stem cells, e.g. human 8-cell-like cells, human totipotent blastomere-like cells, and mouse 2-cell-like cells, have been successfully established and exhibit high developmental potency for both embryonic and extraembryonic contributions. However, the observed discrepancies between these cells and real embryos in terms of epigenetics and transcription suggest that further research is warranted. Our results systematically reviewed the established methods, molecular characteristics, and developmental potency of different naive, formative pluripotent, and totipotent stem cells. Furthermore, we provide a parallel comparison between animal and human models, and offer recommendations for future applications to advance early embryo research and assisted reproduction technologies.

WIDER IMPLICATIONS

Totipotent cell models provide a valuable resource to understand the underlying mechanisms of embryo development and forge new paths toward future treatment of infertility and regenerative medicine. However, current in vitro cell models exhibit epigenetic and transcriptional differences from in vivo embryos, and many cell models are unstable across passages, thus imperfectly recapitulating embryonic development. In this regard, standardizing and expanding current research on totipotent stem cell models are essential to enhance our capability to resemble and decipher embryogenesis.

A Cross-Linked Cyclosiloxane Polymer Matrix as a Platform Enabling Long-Term Culture of Human Induced Pluripotent Stem Cells with Naïve-Like Features

Culture platforms for human induced pluripotent stem cells (hiPSCs) that rely on feeder cells or extracellular matrices (ECMs) face substantial limitations for practical regenerative medicine applications, including undefined components, high costs, and a tendency to maintain hiPSCs in the primed pluripotent state, which has lower differentiation potential than the naïve state. To overcome these challenges, we developed a long-term hiPSC culture platform based on a cross-linked cyclosiloxane polymer matrix that preserves pluripotency with naïve-like characteristics. Through optimization, we identified an ideal cyclosiloxane polymer matrix, designated as poly-Z, which supported the growth of hiPSCs as spheroids. Even after 60 d of continuous culture, hiPSC spheroids maintained on poly-Z retained pluripotency markers and normal karyotypes at levels comparable to those of hiPSC colonies cultured on conventional vitronectin (VN)-coated plates. Furthermore, mRNA sequencing revealed that hiPSC spheroids cultured on poly-Z not only exhibited up-regulation of typical pluripotency-related genes but also showed increased expression of genes associated with the naïve pluripotent state, in contrast to the primed state observed in hiPSCs cultured on VN-coated plates or in suspension culture. Gene ontology (GO) analysis and gene set enrichment analysis (GSEA) further suggested that the down-regulation of genes involved in cell-ECM interactions contributed to the induction of naïve-like features in poly-Z-cultured hiPSC spheroids. These findings highlight the potential of cross-linked cyclosiloxane-based polymer matrices as an innovative platform for human pluripotent stem cell research and regenerative medicine.

Frontier progress and translational challenges of pluripotent differentiation of stem cells

Stem cell research has significantly transformed regenerative medicine, with pluripotent stem cells (PSCs) serving as the cornerstone for disease modeling, drug screening, and therapeutic applications. Embryonic stem cells (ESCs) exhibit unparalleled self-renewal and tri-lineage differentiation, while induced pluripotent stem cells (iPSCs) bypass ethical constraints through somatic cell reprogramming. Clinical trials highlight the potential of mesenchymal stem cells (MSCs) in osteoarthritis and graft-versus-host disease, which leverage their immunomodulatory and paracrine effects. Despite advancements, challenges persist: iPSCs face epigenetic instability and tumorigenic risks, and adult stem cells struggle with inefficient differentiation. This paper systematically reviews stem cell source classification, differentiation regulatory mechanisms, cutting-edge technologies such as CRISPR/Cas9, and explores field-specific controversies (e.g., epigenetic stability of iPSCs) and future directions (e.g., integration of organoids and biomaterials). By analyzing current progress and challenges, it provides a multidimensional perspective for stem cell research.

Collagen Nanofiber Reinforced Alginate Hydrogel Tube Microbioreactors for Cell Culture

The large-scale production of mammalian cells is pivotal for various applications; however, current bioreactor technologies encounter significant technical and economic challenges. Scaling up cell cultures remains problematic due to excessive cell aggregation, shear stress-induced cell death, batch-to-batch inconsistencies, and limited scalability. We propose that engineering a cell-friendly microenvironment can enhance culture efficiency. Previously, we developed alginate hydrogel microtubes (AlgTubes) that significantly improved cell density and growth rates. Nevertheless, AlgTubes lack adhesion sites essential for anchorage-dependent cells and frequently break, causing cell leakage and production inconsistencies. To address these limitations, this study reinforced AlgTubes with collagen nanofibers, creating collagen-alginate hybrid hydrogel microtubes (ColAlgTubes). Utilizing a novel micro-extruder, we efficiently produced cell-loaded ColAlgTubes. Collagen formed a dense nanofiber network interwoven with the alginate mesh, enhancing the hydrogel's mechanical properties while providing cell adhesion sites. ColAlgTubes protected cells from hydrodynamic stress and maintained cell mass within a 400 μm diameter, ensuring efficient nutrient exchange and waste removal. This optimized microenvironment resulted in high cell viability, rapid proliferation, and exceptional yields of 5×10 8 cells/mL - 200 times higher than conventional culture methods. With their scalability, cost-effectiveness, and efficiency, ColAlgTubes offers a transformative solution for large-scale cell production with broad applications in biotechnology, regenerative medicine, and therapeutic manufacturing.

Intelligent Manufacturing for Osteoarthritis Organoids

Osteoarthritis (OA) is the most prevalent degenerative joint disease worldwide, imposing a substantial global disease burden. However, its pathogenesis remains incompletely understood, and effective treatment strategies are still lacking. Organoid technology, in which stem cells or progenitor cells self-organise into miniature tissue structures under three-dimensional (3D) culture conditions, provides a promising in vitro platform for simulating the pathological microenvironment of OA. This approach can be employed to investigate disease mechanisms, carry out high-throughput drug screening and facilitate personalised therapies. This review summarises joint structure, OA pathogenesis and pathological manifestations, thereby establishing the disease context for the application of organoid technology. It then examines the components of the arthrosis organoid system, specifically addressing cartilage, subchondral bone, synovium, skeletal muscle and ligament organoids. Furthermore, it details various strategies for constructing OA organoids, including considerations of cell selection, pathological classification and fabrication techniques. Notably, this review introduces the concept of intelligent manufacturing of OA organoids by incorporating emerging engineering technologies such as artificial intelligence (AI) into the organoid fabrication process, thereby forming an innovative software and hardware cluster. Lastly, this review discusses the challenges currently facing intelligent OA organoid manufacturing and highlights future directions for this rapidly evolving field. By offering a comprehensive overview of state-of-the-art methodologies and challenges, this review anticipates that intelligent, automated fabrication of OA organoids will expedite fundamental research, drug discovery and personalised translational applications in the orthopaedic field.

HAND1, partially mediated through ape-specific LTR binding, is essential for human extra-embryonic mesenchyme derivation from iPSCs

The specification of extra-embryonic mesenchyme (ExMC) is a prime example of developmental divergence between mouse and human. Derived from definitive mesoderm during mouse gastrulation, the human ExMC first appears at peri-implantation prior to gastrulation and therefore its human cellular origin, still unknown, must differ. In a human pluripotent stem cell model, we report that ExMC shares progenitor cells with trophoblast, suggesting a trophectoderm origin. This ability to form ExMC appears to extend to human trophoblast stem cell lines. We define HAND1 as an essential regulator of ExMC specification, with null cells remaining in the trophoblast lineage. Bound by HAND1, ape-specific, endogenous retrovirus-derived LTR2B contributes to unique features of ExMC. Additionally, ExMC supports the maintenance of pluripotent stem cells, possibly reflecting a role in maintaining epiblast pluripotency through peri-implantation development. Our data emphasize the nascent evolutionary innovation in human early development and provide a cellular system to study this.

The building blocks of embryo models: embryonic and extraembryonic stem cells

The process of a single-celled zygote developing into a complex multicellular organism is precisely regulated at spatial and temporal levels in vivo. However, understanding the mechanisms underlying development, particularly in humans, has been constrained by technical and ethical limitations associated with studying natural embryos. Harnessing the intrinsic ability of embryonic stem cells (ESCs) to self-organize when induced and assembled, researchers have established several embryo models as alternative approaches to studying early development in vitro. Recent studies have revealed the critical role of extraembryonic cells in early development; and many groups have created more sophisticated and precise ESC-derived embryo models by incorporating extraembryonic stem cell lines, such as trophoblast stem cells (TSCs), extraembryonic mesoderm cells (EXMCs), extraembryonic endoderm cells (XENs, in rodents), and hypoblast stem cells (in primates). Here, we summarize the characteristics of existing mouse and human embryonic and extraembryonic stem cells and review recent advancements in developing mouse and human embryo models.

High-resolution single-cell RNA-seq data and heterogeneity analysis of human ESCs and ffEPSCs

This study presents a comprehensive transcriptomic analysis of feeder-free extended pluripotent stem cells (ffEPSCs) and their parental human embryonic stem cells (ESCs), providing new insights into understanding human early development and cellular heterogeneity of pluripotency. Leveraging Smart-seq2-based single-cell RNA sequencing (scRNA-seq), we have compared gene expression profiles between ESCs and ffEPSCs and uncovered distinct subpopulations within both groups. Through pseudotime analysis, we have mapped the transition process from ESCs to ffEPSCs, revealing critical molecular pathways involved in the shift from a primed pluripotency to an extended pluripotent state. Additionally, we have employed repeat sequence analysis based on the latest T2T database and identified the stage-specific repeat elements contributing to regulating pluripotency and developmental transitions. This dataset deepens our understanding on early pluripotency and highlights the role of repeat sequences in early embryonic development. Our findings thus offer valuable resources for researchers in stem cell biology, pluripotency, early embryonic development, and potential cell therapy and regenerative medical applications.

Organoids in Dynamic Culture: Microfluidics and 3D Printing Technologies

With the rapid advancement of biomaterials and tissue engineering technologies, organoid research and its applications have made significant strides. Organoids are increasingly utilized in pharmacology, regenerative medicine, and precision clinical medicine. Current trends in organoid research are moving toward multifunctional composite three-dimensional cultivation and dynamic cultivation strategies. Key technologies driving this evolution, including 3D printing and microfluidics, continue to impact new areas of discovery and clinical relevance. This review provides a systematic overview of these emerging trends, discussing the strengths and limitations of these critical technologies and offering insight and research directions for professionals working in the organoid field.

Fate and state transitions during human blood vessel organoid development

Human blood vessel organoids (hBVOs) have emerged as a system to model human vascular development and disease. Here, we use single-cell multi-omics together with genetic and signaling pathway perturbations to reconstruct hBVO development. Mesodermal progenitors bifurcate into endothelial and mural fates in vitro, and xenografted BVOs acquire definitive arteriovenous endothelial cell specification. We infer a gene regulatory network and use single-cell genetic perturbations to identify transcription factors (TFs) and receptors involved in cell fate specification, including a role for MECOM in endothelial and mural specification. We assess the potential of BVOs to generate organotypic states, identify TFs lacking expression in hBVOs, and find that induced LEF1 overexpression increases brain vasculature specificity. Finally, we map vascular disease-associated genes to hBVO cell states and analyze an hBVO model of diabetes. Altogether, we provide a comprehensive cell state atlas of hBVO development and illuminate the power and limitation of hBVOs for translational research.

Exploring human brain development and disease using assembloids

How the human brain develops and what goes awry in neurological disorders represent two long-lasting questions in neuroscience. Owing to the limited access to primary human brain tissue, insights into these questions have been largely gained through animal models. However, there are fundamental differences between developing mouse and human brain, and neural organoids derived from human pluripotent stem cells (hPSCs) have recently emerged as a robust experimental system that mimics self-organizing and multicellular features of early human brain development. Controlled integration of multiple organoids into assembloids has begun to unravel principles of cell-cell interactions. Moreover, patient-derived or genetically engineered hPSCs provide opportunities to investigate phenotypic correlates of neurodevelopmental disorders and to develop therapeutic hypotheses. Here, we outline the advances in technologies that facilitate studies by using assembloids and summarize their applications in brain development and disease modeling. Lastly, we discuss the major roadblocks of the current system and potential solutions.

Small molecules direct the generation of ameloblast-like cells from human embryonic stem cells

BACKGROUND

Ameloblasts present a promising avenue for the investigation of enamel and tooth regeneration. Previous protocols for directing the differentiation of human embryonic stem cells (hESCs) into dental epithelial (DE) cells involving the need for additional cells, conditional medium, and the use of costly cytokines. Importantly, ameloblasts have not been generated from hESCs in previous studies. Hence, we aimed to identify defined differentiation conditions that would solely utilize small molecules to achieve the production of ameloblasts.

METHODS

We developed a three-step strategy entailing the progression of hESCs through non-neural ectoderm (NNE) and DE to generate functional ameloblasts in vitro. Initially, the NNE fate was induced from hESCs using a 6-day differentiation protocol with 1 µmol/L Retinoic acid (RA). Subsequently, the NNE lineage was differentiated into DE by employing a combination of 1 µmol/L LDN193189 (a BMP signaling inhibitor) and 1 µmol/L XAV939 (a WNT signaling inhibitor). In the final phase, 3 µmol/L CHIR99021 (a WNT signaling activator) and 2 µmol/L DAPT (a NOTCH signaling inhibitor) were utilized to achieve the fate of ameloblasts from DE cells. Three-dimensional cultures were investigated to enhance the ameloblast differentiation ability of the induced DE cells. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence were conducted to assess the expression of lineage-specific markers. Alizarin Red S (ARS) staining was performed to evaluate the formation of mineralization nodules.

RESULTS

The application of RA facilitated the efficient generation of NNE within a six-day period. Subsequently, upon stimulation with LDN193189 and XAV939, a notable emergence of DE cells was observed on the eighth days. By the tenth day, ameloblast-like cells derived from hESCs were generated. Upon cultivation in spheroids, these cells exhibited elevated levels of ameloblast markers AMBN and AMELX expression, suggesting that spheroid culture augments the differentiation of ameloblasts.

CONCLUSION

We established an efficient small molecule-based method to differentiate hESCs into ameloblast-like cells through the concerted modulation of RA, BMP, WNT, and NOTCH signaling pathways, potentially advancing research in enamel and tooth regeneration.

EIF3D safeguards the homeostasis of key signaling pathways in human primed pluripotency

Although pluripotent stem cell (PSC) properties, such as differentiation and infinite proliferation, have been well documented within the frameworks of transcription factor networks, epigenomes, and signal transduction, they remain unclear and fragmented. Directing attention toward translational regulation as a bridge between these events can yield additional insights into previously unexplained mechanisms. Our functional CRISPR interference screen-based approach revealed that EIF3D, a translation initiation factor, is crucial for maintaining primed pluripotency. Loss of EIF3D disrupted the balance of pluripotency-associated signaling pathways, thereby compromising primed pluripotency. Moreover, EIF3D ensured robust proliferation by controlling the translation of various p53 regulators, which maintain low p53 activity in the undifferentiated state. In this way, EIF3D-mediated translation contributes to tuning the homeostasis of the primed pluripotency networks, ensuring the maintenance of an undifferentiated state with high proliferative potential. This study provides further insights into the translation network in maintaining pluripotency.

The influence of SARS-CoV-2 spike protein exposure on retinal development in the human retinal organoids

BACKGROUND

Pregnant women are considered a high-risk population for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as the virus can infect the placenta and embryos. Recently, SARS-CoV-2 has been widely reported to cause retinal pathological changes and to infect the embryonic retina. The infection of host cells by SARS-CoV-2 is primarily mediated through spike (S) protein, which also plays a crucial role in the pathogenesis of SARS-CoV-2. However, it remains poorly understood how the S protein of SARS-CoV-2 affects retinal development, and the underlying mechanism has not yet been clarified.

METHODS

We used human embryonic stem cell-derived retinal organoids (hEROs) as a model to study the effect of S protein exposure at different stages of retinal development. hEROs were treated with 2 μg/mL of S protein on days 90 and 280. Immunofluorescence staining, RNA sequencing, and RT-PCR were performed to assess the influence of S protein exposure on retinal development at both early and late stages.

RESULTS

The results showed that ACE2 and TMPRSS2, the receptors facilitating SARS-CoV-2 entry into host cells, were expressed in hEROs. Exposure to the S protein induced an inflammatory response in both the early and late stages of retinal development in the hEROs. Additionally, RNA sequencing indicated that early exposure of the S protein to hEROs affected nuclear components and lipid metabolism, while late-stages exposure resulted in changes to cell membrane components and the extracellular matrix.

CONCLUSION

This work highlights the differential effects of SARS-CoV-2 S protein exposure on retinal development at both early and late stages, providing insights into the cellular and molecular mechanisms underlying SARS-CoV-2-induced developmental impairments in the human retina.

Benchmark for Setting ACTH Cell Dosage in Clinical Regenerative Medicine for Post-Operative Hypopituitarism

BACKGROUND/OBJECTIVES

Our objective is to develop hormone-producing pituitary cells that can function in the same manner as the human body and provide more effective treatments than current hormone replacement therapy. We have already established a technique for generating hypothalamic-pituitary organoids using feeder-free human pluripotent stem cells (hPSCs) and demonstrated their effectiveness in vivo through transplantation into hypopituitary mouse models. To prospectively determine the upper limit of transplanting adenohypophyseal cells into humans, we investigated the human maximum secretion capacity of adrenocorticotropic hormone (ACTH) and growth hormone (GH).

METHODS

We analyzed data from 28 patients with pituitary adenomas, among whom 16 evinced no abnormality of ACTH secretion and 12 showed no GH secretion on corticotropin-releasing hormone (CRH) and growth hormone-releasing hormone-2 (GHRP-2) stimulation testing.

RESULTS

The average ACTH peak value after CRH stimulation tests was 97.2 pg/mL, and the average GH peak value after GHRP-2 stimulation tests was 25.1 ng/mL.

CONCLUSIONS

These data will likely serve as benchmarks of ACTH and GH secretion when transplanting cultured cells into humans.

Establishing Bovine Embryonic Stem Cells and Dissecting Their Self-Renewal Mechanisms

Bovine pluripotent stem cells (PSCs) hold significant potential for diverse applications in agriculture, reproductive biotechnology, and biomedical research. However, challenges persist in establishing stable bovine PSC lines and understanding the mechanisms underlying their pluripotency maintenance. Here, we derived bovine embryonic stem cells (bESCs) from Holstein cattle embryos. These cells exhibited robust differentiation capacity into three germ layers in vitro and in vivo. Transcriptome analysis revealed distinct molecular profiles compared to primed-state bESCs. Notably, bESC proliferation ceased on methanol-treated feeder cells, in contrast to mouse ESCs (mESCs), which proliferated normally. Pathway analysis identified key signaling events critical for bESC survival and proliferation, highlighting species-specific regulatory mechanisms. Furthermore, the derived bESCs demonstrated chimerism capacity in early bovine embryos, underscoring their functional pluripotency. This work provides a foundation for advancing bovine embryology research and stem cell-based biotechnologies in livestock.

Scaling up pluripotent stem cell-based therapies - considerations, current challenges and emerging technologies: perspectives from the ISCT Emerging Regenerative Medicine Working Group

Approval of induced pluripotent stem cells (iPSCs) for the manufacture of cell therapies to support clinical trials is now becoming realized after more than 20 years of research and development. However, manufacturing these therapies at the scale required for patient treatment, as well as for key clinical trial enabling activities such as preclinical and stability studies, remains a challenge. In 2022 the International Society for Cell and Gene Therapy (ISCT) established a Working Group on Emerging Regenerative Medicine Technologies, an area in which iPSC-derived technologies are expected to play a key role. In this article, the Working Group provides an overview of the considerations and challenges facing stem cell therapy developers, including development-stage specific manufacturing processes, the decision on when to implement automation, the choice of technology and different requirements of expansion and differentiation aspects of the process, and the integration of automation for both manufacturing and analytics in an end-to-end manufacturing process. The role of scalable manufacturing technologies in the application of quality-by-design approaches to product development, and the use of design-of-experiment approaches for increased product characterization, is discussed. Finally, we provide an in-depth review of the different technologies that have been used for expansion and differentiation of iPSC-derived therapies to date, including compatibility with good manufacturing practice requirements and process analytical technologies. We hope that this overview will summarize the existing knowledge in the field and reduce the challenges that therapy developers face in translating their research into clinical and commercial scale manufacturing.

Cell-based regenerative and rejuvenation strategies for treating neurodegenerative diseases

Neurodegenerative diseases including Alzheimer's and Parkinson's disease are age-related disorders which severely impact quality of life and impose significant societal burdens. Cellular senescence is a critical factor in these disorders, contributing to their onset and progression by promoting permanent cell cycle arrest and reducing cellular function, affecting various types of cells in brain. Recent advancements in regenerative medicine have highlighted "R3" strategies-rejuvenation, regeneration, and replacement-as promising therapeutic approaches for neurodegeneration. This review aims to critically analyze the role of cellular senescence in neurodegenerative diseases and organizes therapeutic approaches within the R3 regenerative medicine paradigm. Specifically, we examine stem cell therapy, direct lineage reprogramming, and partial reprogramming in the context of R3, emphasizing how these interventions mitigate cellular senescence and counteracting aging-related neurodegeneration. Ultimately, this review seeks to provide insights into the complex interplay between cellular senescence and neurodegeneration while highlighting the promise of cell-based regenerative strategies to address these debilitating conditions.

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.

Recent progress on the organoids: Techniques, advantages and applications

Organoids are a cutting-edge technology in the life sciences field, with applications in precision medicine, bionic organs, and toxicological evaluations of chemicals. Their 3D structure closely resembles that of real organs, allowing more accurate functional mimicry. The 3D organoid culture system can simulate the growth state of cells in vivo and establish a suspension culture system for organoid 3D culture by using scaffold-less or scaffold technology to avoid direct contact between cells and plastic culture vessels. Furthermore, organoids can simulate the pathophysiological state of tissues and organs in vitro. This paper primarily discusses the construction methodologies, as well as the advantages and disadvantages of 3D culture systems for both scaffold-free organoids and scaffolded organoids. This review also summarizes the application of organoid models in chemical toxicology evaluation, drug screening and functional evaluation, establishment of in vitro disease models, and research on disease occurrence and potential mechanisms. The aim is to provide a reference for the research and practical applications of organoid-related scientific fields.

Advances in clinical translation of stem cell-based therapy in neurological diseases

Stem cell-based therapies have raised considerable interest to develop regenerative treatment for neurological disorders with high disability. In this review, we focus on recent preclinical and clinical evidence of stem cell therapy in the treatment of degenerative neurological diseases and discuss different cell types, delivery routes and biodistribution of stem cell therapy. In addition, recent advances of mechanistic insights of stem cell therapy, including functional replacement by exogenous cells, immunomodulation and paracrine effects of stem cell therapies are also demonstrated. Finally, we also highlight the adjunction approaches that has been implemented to augment their reparative function, survival and migration to target specific tissue, including stem cell preconditioning, genetical engineering, co-transplantation and combined therapy.

3D-Bioprinting for Precision Microtissue Engineering: Advances, Applications, and Prospects

Microtissues, engineered to emulate the complexity of human organs, are revolutionizing the fields of regenerative medicine, disease modelling, and drug screening. Despite the promise of traditional microtissue engineering, it has yet to achieve the precision required to fully replicate organ-like structures. Enter 3D bioprinting, a transformative approach that offers unparalleled control over the microtissue's spatial arrangement and mechanical properties. This cutting-edge technology enables the detailed layering of bioinks, crafting microtissues with tissue-like 3D structures. It allows for the direct construction of organoids and the fine-tuning of the mechanical forces vital for tissue maturation. Moreover, 3D-printed devices provide microtissues with the necessary guidance and microenvironments, facilitating sophisticated tissue interactions. The applications of 3D-printed microtissues are expanding rapidly, with successful demonstrations of their functionality in vitro and in vivo. This technology excels at replicating the intricate processes of tissue development, offering a more ethical and controlled alternative to traditional animal models. By simulating in vivo conditions, 3D-printed microtissues are emerging as powerful tools for personalized drug screening, offering new avenues for pharmaceutical development and precision medicine.

From Promise to Practice: Recent Growth in 30 Years of Tissue Engineering Commercialization

This perspective, marking the 30th anniversary of the Tissue Engineering journal, discusses the exciting trends in the global commercialization of tissue engineering technology. Within a historical context, we present an evolution of challenges and a discussion of the last 5 years of global commercial successes and emerging market trends, highlighting the continued expansion of the field in the northeastern United States. This leads to an overview of the last 5 years' progress in clinical trials for tissue-engineered therapeutics, including an analysis of trends in success and failure. Finally, we provide a broad overview of preclinical research and a perspective on where the state-of-the-art lies on the horizon.

The Use of Neurons Derived from Pluripotent Stem Cells to Study Nerve-Cancer Cell Interactions

Tumor innervation is a complex interaction between nerves and cancer cells that consists of axons invading tumors, and its complexity remains largely unknown in humans. Although some retrospective studies have provided important insights into the relationship between nerves and tumors, further knowledge is required about this biological process. Animal experiments have elucidated several molecular and cellular mechanisms of tumor innervation; however, no experimental models currently exist to study interactions between human cancer and nerve cells. Human pluripotent stem cells can differentiate into neurons for research purposes; however, the use of these neurons to study interactions with cancer cells remains largely unexplored. Hence, here we analyze the potential of human pluripotent stem cells to study the interaction of cancer cells and neurons derived from human pluripotent stem cells to unravel the poorly understood mechanisms of human tumor innervation.

Chondrocalcin: Insights into its regulation and multi-function in cartilage and bone

Type Ⅱ collagen (COLⅡ) is the primary constituent of the cartilage matrix, specifically present in vitreous bodies, cartilage, bone, and other skeletal elements. Therefore, the normal expression of COLⅡ is crucial for the normal development, linear growth, mechanical properties, and self-repairing ability of cartilage. Chondrocalcin, the C-propeptide of type Ⅱ procollagen, is not only a marker of COLⅡ synthesis but also one of the most abundant polypeptides in cartilage. This work examines the pivotal role of chondrocalcin in the synthesis of COLⅡ, comprehensively examining its regulation and multi-functions in cartilage and bone related diseases. Our findings suggest that mutations in the chondrocalcin-encoding domain of COL2A1 affect cartilage and bone development in clinical conditions.

Role of octamer transcription factor 4 in proliferation, migration, drug sensitivity, and stemness maintenance of pancreatic cancer cells

BACKGROUND

Pancreatic cancer (PC) is one of the most aggressive malignancies characterized by rapid progression and poor prognosis. The involvement of cancer stem cells (CSCs) and Octamer transcription factor 4 (OCT4) in PC pathobiology is being increasingly recognized.

AIM

To investigate the role of OCT4 in pancreatic CSCs and its effect on PC cell proliferation, migration, drug sensitivity, and stemness maintenance.

METHODS

We analyzed OCT4 and CD133 expression in PC tissues and cell lines. BxPC-3 cells were used to assess the effects of OCT4 modulation on cellular behavior. Proliferation, migration, and stemness of BxPC-3 cells were evaluated, and the PI3K/AKT/mTOR pathway was examined to gain mechanistic insights.

RESULTS

OCT4 and CD133 were significantly overexpressed in PC tissues. OCT4 modulation altered BxPC-3 cell proliferation, invasion, and stemness, with OCT4 overexpression (OV-OCT4) enhancing these properties and OCT4 interference decreasing them. OV-OCT4 activated the PI3K/AKT/mTOR pathway, which correlated with an increase in PC stem cells (PCSC).

CONCLUSION

OCT4 plays a crucial role in PCSCs by influencing the aggressiveness and drug resistance of PC cells, thus presenting itself as a potential therapeutic target.

A microfluidic platform for anterior-posterior human endoderm patterning via countervailing morphogen gradients in vitro

Understanding how morphogen gradients spatially pattern tissues is a fundamental question in developmental biology but can be difficult to directly address using conventional approaches. Here, we expose hPSC-derived endoderm cells to countervailing gradients of anteriorizing and posteriorizing signals using a widely available microfluidic device. This approach yielded spatially patterned cultures comprising anterior foregut (precursor to the thyroid, esophagus, and lungs) and mid/hindgut (precursor to the intestines) cells, whose identities were confirmed using single-cell RNA sequencing (scRNA-seq). By exposing stem cells to externally applied signaling gradients, this widely accessible microfluidic platform should accelerate the production of spatially patterned tissues, complementing internally self-organizing organoids. Applying artificial morphogen gradients in vitro may also illuminate how developing tissues interpret signaling gradients in systems that are not readily accessible for in vivo studies.

Protocol for the generation of HLF+ HOXA+ human hematopoietic progenitor cells from pluripotent stem cells

Hematopoietic stem cells (HSCs) generate blood and immune cells. Here, we present a protocol to differentiate human pluripotent stem cells (hPSCs) into hematopoietic progenitors that express the signature HSC transcription factors HLF, HOXA5, HOXA7, HOXA9, and HOXA10. hPSCs are dissociated, seeded, and then sequentially differentiated into posterior primitive streak, lateral mesoderm, artery endothelium, hemogenic endothelium, and hematopoietic progenitors through the sequential addition of defined, serum-free media. This 10-day protocol enables the manufacturing of blood and immune cells in monolayer cultures. For complete details on the use and execution of this protocol, please refer to Fowler and Zheng et al.1.

Metformin Protects Human Induced Pluripotent Stem Cell (hiPSC)-Derived Neurons from Oxidative Damage Through Antioxidant Mechanisms

The antidiabetic drug metformin possesses antioxidant and cell protective effects including in neuronal cells, suggesting its potential use for treating neurodegenerative diseases. This study aimed to assess metformin's effects on viability and antioxidant activity in human-induced pluripotent stem cell (hiPSC)-derived neurons under varying concentrations and stress conditions. Six lines of hiPSC-derived neuronal progenitors derived from healthy human iPSCs were treated with metformin (1-500 µM) on day 18 of differentiation. For mature neurons (day 30), three concentrations (10 µM, 50 µM, and 100 µM) were used to assess cytotoxicity. MG132 proteasomal inhibitor and sodium arsenite (NaArs) were used to investigate oxidative stress, and 50 µM of metformin was tested for its protective effects against oxidative stress in hiPSC-derived neurons. Metformin treatment did not affect cell viability, neuronal differentiation, or trigger reactive oxygen species (ROS) generation in healthy hiPSC-derived motor neurons. Additionally, mitochondrial membrane potential (MMP) loss was not observed at 50 µM metformin. Metformin effectively protected neurons from stress agents and elevated the expression of antioxidant genes when treated with MG132. However, an interplay between MG132 and metformin resulted in lower expression of Nrf2 and NQO1 compared to the MG132 group alone, indicating reduced JC-1 aggregate levels due to MG132 proteasomal inhibition. Metformin upregulated antioxidant genes in hiPSC-derived neurons under stress conditions and protected the cells from oxidative damage.

Genes as Genome Stabilizers in Pluripotent Stem Cells

Pluripotent stem cells, comprising embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are characterized by their self-renewal capacity and the ability to differentiate into cells of all three germ layers of an adult animal. Out of the two, iPSCs are generated through the reprogramming of somatic cells by inducing a pluripotency-specific transcriptional program. This process requires a resetting of the somatic cell genome to a pluripotent cell-specific genome, resulting in cellular stress at genomic, epigenetic, and transcriptional levels. Notably, in contrast to the predominant compact and inactive organization of chromatin in somatic cells, the chromatin in ESCs and iPSCs is open. Furthermore, maintaining a pluripotent state needs a plethora of changes in the genetic landscape of the cells. Here, we attempt to elucidate how certain genes safeguard genomic stability in ESCs and iPSCs, aiding in the complex cellular mechanisms that regulate self-renewal, pluripotency, and somatic reprogramming.

Small-diameter artery grafts engineered from pluripotent stem cells maintain 100% patency in an allogeneic rhesus macaque model

Autologous vascular grafts, the only clinically approved option for small-diameter (<6 mm) revascularizations, require invasive harvesting and have limited availability and variable quality. To address these challenges, we develop a 3-mm-diameter artery graft by using arterial endothelial cells (AECs) derived from pluripotent stem cells (PSCs). After establishing technologies for pure AEC generation and expanded polytetrafluoroethylene (ePTFE) graft coating, we engineer artery grafts by seeding the inner lumen of ePTFE vascular grafts with either major histocompatibility complex (MHC) mismatched unmodified-wild-type (MHC-WT) AECs or MHC class I/II double knockout (MHC-DKO) AECs. Their function is evaluated in a rhesus arterial interposition grafting model. MHC-WT grafts maintained 100% patency for 6 months, significantly better than naked and MHC-DKO grafts. Additionally, the endothelium of MHC-WT grafts is repopulated with host cells, supporting long-term patency. Collectively, our study demonstrates that PSC-derived MHC-WT artery grafts provide an unlimited homogenous resource for allogeneic arterial revascularization.

Multilayered Freestanding Porous Polycarbonate Nanosheets with Directed Protein Permeability for Cell-Encapsulated Devices

Implantable pancreatic β cell-encapsulated devices are required for the treatment of type 1 diabetes. Such devices should enable a semipermeable membrane to release insulin in response to glucose levels while avoiding immune reactions. Micrometer-thick track-etched porous polycarbonate (PC) membranes have been used for this purpose. However, the immediate release of insulin remains a challenge in the development of such semipermeable membranes. Herein, we attempted to develop a freestanding polymeric ultrathin film (nanosheet) with a porous structure that can be used in a cell-encapsulated device. Specifically, we fabricated a nonbiodegradable, porous PC nanosheet to enhance molecular permeability. The nanosheet was multistacked to ensure the controlled permeability of proteins of various molecular weights, such as insulin and IgG. The porous PC nanosheet was prepared by gravure coating using a blend solution comprising PC and polystyrene (PS) to induce macro-phase separation of the PC and PS. When the PC:PS weight ratio of the mixture was reduced to 3:1, we succeeded in fabricating a porous PC nanosheet (thickness: 100 nm, diameter: < 2.5 μm). A triple layer of such porous nanosheets with various pore sizes demonstrated 10 times less protein clogging, 10 times higher insulin permeability, and comparable IgG-blocking capability compared with commercially available porous PC membranes (thickness: 10 μm). Finally, we demonstrated that a cell-encapsulated device equipped with the multilayered porous PC nanosheet as a permeable membrane preserved the glucose response level of insulin-producing cells before, during, and after the cell-encapsulation process. We believe that cell-encapsulated devices equipped with such porous PC nanosheets will enable immediate insulin release in response to changes in glucose levels.

In vitro liver models for toxicological research

Drug-induced liver injury (DILI) presents a major challenge not only in new drug development but also in post-marketing withdrawals and the safety of food, cosmetics, and chemicals. Experimental model organisms such as the rodents have been widely used for preclinical toxicological testing. However, the tension exists associated with the ethical and sustainable use of animals in part because animals do not necessarily inform the human-specific ADME (adsorption, dynamics, metabolism and elimination) profiling. To establish alternative models in humans, in vitro hepatic tissue models have been proposed, ranging from primary hepatocytes, immortal hepatocytes, to the development of new cell resources such as stem cell-derived hepatocytes. Given the evolving number of novel alternative methods, understanding possible combinations of cell sources and culture methods will be crucial to develop the context-of-use assays. This review primarily focuses on 3D liver organoid models for conducting. We will review the relevant cell sources, bioengineering methods, selection of training compounds, and biomarkers towards the rationale design of in vitro toxicology testing.

A systematic review and embryological perspective of pluripotent stem cell-derived autonomic postganglionic neuron differentiation for human disease modeling

Human autonomic neuronal cell models are emerging as tools for modeling diseases such as cardiac arrhythmias. In this systematic review, we compared 33 articles applying 14 different protocols to generate sympathetic neurons and 3 different procedures to produce parasympathetic neurons. All methods involved the differentiation of human pluripotent stem cells, and none employed permanent or reversible cell immortalization. Almost all protocols were reproduced in multiple pluripotent stem cell lines, and over half showed evidence of neural firing capacity. Common limitations in the field are a lack of three-dimensional models and models that include multiple cell types. Sympathetic neuron differentiation protocols largely mirrored embryonic development, with the notable absence of migration, axon extension, and target-specificity cues. Parasympathetic neuron differentiation protocols may be improved by including several embryonic cues promoting cell survival, cell maturation, or ion channel expression. Moreover, additional markers to define parasympathetic neurons in vitro may support the validity of these protocols. Nonetheless, four sympathetic neuron differentiation protocols and one parasympathetic neuron differentiation protocol reported more than two-thirds of cells expressing autonomic neuron markers. Altogether, these protocols promise to open new research avenues of human autonomic neuron development and disease modeling.

Cardiac differentiation roadmap for analysis of plasticity and balanced lineage commitment

Stem cell-based models of human heart tissue and cardiac differentiation employ monolayer and 3D organoid cultures with different properties, cell type composition, and maturity. Here we show how cardiac monolayer, embryoid body, and engineered heart tissue trajectories compare in a single-cell roadmap of atrial and ventricular differentiation conditions. Using a multiomic approach and gene-regulatory network inference, we identified regulators of the epicardial, atrial, and ventricular cardiomyocyte lineages. We identified ZNF711 as a regulatory switch and safeguard for cardiomyocyte commitment. We show that ZNF711 ablation prevents cardiomyocyte differentiation in the absence of retinoic acid, causing progenitors to be diverted more prominently to epicardial and other lineages. Retinoic acid rescues this shift in lineage commitment and promotes atrial cardiomyocyte differentiation by regulation of shared and complementary target genes, showing interplay between ZNF711 and retinoic acid in cardiac lineage commitment.

An obesogenic FTO allele causes accelerated development, growth and insulin resistance in human skeletal muscle cells

Human GWAS have shown that obesogenic FTO polymorphisms correlate with lean mass, but the mechanisms have remained unclear. It is counterintuitive because lean mass is inversely correlated with obesity and metabolic diseases. Here, we use CRISPR to knock-in FTOrs9939609-A into hESC-derived tissue models, to elucidate potentially hidden roles of FTO during development. We find that among human tissues, FTOrs9939609-A most robustly affect human muscle progenitors' proliferation, differentiation, senescence, thereby accelerating muscle developmental and metabolic aging. An edited FTOrs9939609-A allele over-stimulates insulin/IGF signaling via increased muscle-specific enhancer H3K27ac, FTO expression and m6A demethylation of H19 lncRNA and IGF2 mRNA, with excessive insulin/IGF signaling leading to insulin resistance upon replicative aging or exposure to high fat diet. This FTO-m6A-H19/IGF2 circuit may explain paradoxical GWAS findings linking FTOrs9939609-A to both leanness and obesity. Our results provide a proof-of-principle that CRISPR-hESC-tissue platforms can be harnessed to resolve puzzles in human metabolism.