Molecular basis of vertebrate endoderm development

RFX6 regulates human intestinal patterning and function upstream of PDX1

The gastrointestinal (GI) tract is complex and consists of multiple organs with unique functions. Rare gene variants can cause congenital malformations of the human GI tract, although the molecular basis of these has been poorly studied. We identified a patient with compound-heterozygous variants in RFX6 presenting with duodenal malrotation and atresia, implicating RFX6 in development of the proximal intestine. To identify how mutations in RFX6 impact intestinal patterning and function, we derived induced pluripotent stem cells from this patient to generate human intestinal organoids (HIOs). We identified that the duodenal HIOs and human tissues had mixed regional identity, with gastric and ileal features. CRISPR-mediated correction of RFX6 restored duodenal identity. We then used gain- and loss-of-function and transcriptomic approaches in HIOs and Xenopus embryos to identify that PDX1 is a downstream transcriptional target of RFX6 required for duodenal development. However, RFX6 had additional PDX1-independent transcriptional targets involving multiple components of signaling pathways that are required for establishing early regional identity in the GI tract. In summary, we have identified RFX6 as a key regulator in intestinal patterning that acts by regulating transcriptional and signaling pathways.

PAX1 represses canonical Wnt signaling pathway and plays dual roles during endoderm differentiation

BACKGROUND

Paired box 1 (PAX1) is a transcription factor and essential for the development of pharyngeal pouches-derived tissues, including thymus. PAX1 mutations are identified in Severe Combined Immunodeficiency (SCID) patients with Otofaciocervical Syndrome Type 2 (OTFCS2). However, despite the critical roles of PAX1 in embryonic development and diseases, detailed insights into its molecular mode of action are critically missing.

METHODS

The repressing roles of PAX1 and SCID associated mutants on Wnt signaling pathway were investigated by luciferase reporter assays, qRT-PCR and in situ hybridization in HEK293FT, HCT116 cells and zebrafish embryos, respectively. Co-immunoprecipitation (co-IP) and western blotting assays were carried out to identify the molecular mechanisms underlying PAX1's role on Wnt signaling pathway. hESC based endoderm differentiation, flow cytometry, high-throughput sequencing data analysis, and qRT-PCR assays were utilized to determine the roles of PAX1 during endoderm differentiation.

RESULTS

Here, we show that PAX1 represses canonical Wnt signaling pathway in vertebrate cells. Mechanically, PAX1 competes with SUMO E3 ligase PIASy to bind to TCF7L2, thus perturbing TCF7L2 SUMOylation level, further reducing its transcriptional activity and protein stability. Moreover, we reveal that PAX1 plays dual roles in hESC-derived definitive and foregut/pharyngeal endoderm cells, which give rise to the thymus epithelium, by inhibiting Wnt signaling. Importantly, our data show PAX1 mutations found in SCID patients significantly compromise the suppressing ability of PAX1 on Wnt signaling.

CONCLUSIONS

Our study presents a novel molecular mode of action of PAX1 in regulation of canonical Wnt signaling and endoderm differentiation, thus providing insights for the molecular basis of PAX1 associated SCID, offering better understanding of the behavior of PAX1 in embryogenesis.

Developmental toxicity assessment of neonicotinoids and organophosphate esters with a human embryonic stem cell- and metabolism-based fast-screening model

In recent years, neonicotinoids (NEOs) and organophosphate esters (OPEs) have been widely used as substitutes for traditional pesticides and brominated flame-retardants, respectively. Previous studies have shown that those compounds can be frequently detected in environmental and human samples, are able to penetrate the placental barrier, and are toxic to animals. Thus, it is reasonable to speculate that NEOs and OPEs may have potential adverse effects in humans, especially during development. We employed a human embryonic stem cell differentiation- and liver S9 fraction metabolism-based fast screening model to assess the potential embryonic toxicity of those two types of chemicals. We show that four NEO and five OPE prototypes targeted mostly ectoderm specification, as neural ectoderm and neural crest genes were down-regulated, and surface ectoderm and placode markers up-regulated. Human liver S9 fraction's treatment could generally reduce the effects of the chemicals, except in a few specific instances, indicating the liver may detoxify NEOs and OPEs. Our findings suggest that NEOs and OPEs interfere with human early embryonic development.

Magnesium and Liver Metabolism Through the Lifespan

Within the organism, the liver is the main organ responsible for metabolic homeostasis and xenobiotic transformation. To maintain an adequate liver weight-to-bodyweight ratio, this organ has an extraordinary regenerative capacity and is able to respond to an acute insult or partial hepatectomy. Maintenance of hepatic homeostasis is crucial for the proper functioning of the liver, and in this context, adequate nutrition with macro- and micronutrient intake is mandatory. Among all known macro-minerals, magnesium has a key role in energy metabolism and in metabolic and signaling pathways that maintain liver function and physiology throughout its life span. In the present review, the cation is reported as a potential key molecule during embryogenesis, liver regeneration, and aging. The exact role of the cation during liver formation and regeneration is not fully understood due to its unclear role in the activation and inhibition of those processes, and further research in a developmental context is needed. As individuals age, they may develop hypomagnesemia, a condition that aggravates the characteristic alterations. Additionally, risk of developing liver pathologies increases with age, and hypomagnesemia may be a contributing factor. Therefore, magnesium loss must be prevented by adequate intake of magnesium-rich foods such as seeds, nuts, spinach, or rice to prevent age-related hepatic alterations and contribute to the maintenance of hepatic homeostasis. Since magnesium-rich sources include a variety of foods, a varied and balanced diet can meet both macronutrient and micronutrient needs.

Hexafluoropropylene oxide trimer acid (HFPO-TA) disturbs embryonic liver and biliary system development in zebrafish

Hexafluoropropylene oxide trimer acid (HFPO-TA), a novel alternative to perfluorooctanoic acid (PFOA), has emerged as a potential environmental pollutant. Here, to investigate the toxic effects of HFPO-TA on liver and biliary system development, zebrafish embryos were exposed to 0, 50, 100, or 200 mg/L HFPO-TA from 6 to 120 h post-fertilization (hpf). Results showed that the 50 % lethal concentration (LC₅₀) of HFPO-TA was 231 mg/L at 120 hpf, lower than that of PFOA. HFPO-TA exposure decreased embryonic hatching, survival, and body length. Furthermore, HFPO-TA exerted higher toxicity at the specification stage than during the differentiation and maturation stages, leading to small-sized livers in Tg(fabp10a: DsRed) transgenic larvae and histopathological changes. Significant decreases in the mRNA expression of genes related to liver formation were observed. Alanine transaminase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL) levels were significantly increased. HFPO-TA decreased total cholesterol (TCHO) and triglyceride (TG) activities, disturbed lipid metabolism through the peroxisome proliferator-activated receptor (PPAR) pathway, and induced an inflammatory response. Furthermore, HFPO-TA inhibited intrahepatic biliary development in Tg(Tp1:eGFP) transgenic larvae and interfered with transcription of genes associated with biliary duct development. HFPO-TA reduced bile acid synthesis but increased bile acid transport, resulting in disruption of bile acid metabolism. Therefore, HFPO-TA influenced embryonic liver and biliary system morphogenesis, caused liver injury, and may be an unsafe alternative for PFOA.

Differential regulation of alternate promoter regions in Sox17 during endodermal and vascular endothelial development

Sox17 gene expression is essential for both endothelial and endodermal cell differentiation. To better understand the genetic basis for the expression of multiple Sox17 mRNA forms, we identified and performed CRISPR/Cas9 mutagenesis of two evolutionarily conserved promoter regions (CRs). The deletion of the upstream and endothelial cell-specific CR1 caused only a modest increase in lympho-vasculogenesis likely via reduced Notch signaling downstream of SOX17. In contrast, the deletion of the downstream CR2 region, which functions in both endothelial and endodermal cells, impairs both vascular and endodermal development causing death by embryonic day 12.5. Analyses of 3D chromatin looping, transcription factor binding, histone modification, and chromatin accessibility data at the Sox17 locus and surrounding region further support differential regulation of the two promoters during the development.

Derivation and Characterization of Endothelial Cells from Porcine Induced Pluripotent Stem Cells

Although the study on the regulatory mechanism of endothelial differentiation from the perspective of development provides references for endothelial cell (EC) derivation from pluripotent stem cells, incomplete reprogramming and donor-specific epigenetic memory are still thought to be the obstacles of iPSCs for clinical application. Thus, it is necessary to establish a stable iPSC-EC induction system and investigate the regulatory mechanism of endothelial differentiation. Based on a single-layer culture system, we successfully obtained ECs from porcine iPSCs (piPSCs). In vitro, the derived piPSC-ECs formed microvessel-like structures along 3D gelatin scaffolds. Under pathological conditions, the piPSC-ECs functioned on hindlimb ischemia repair by promoting blood vessel formation. To elucidate the molecular events essential for endothelial differentiation in our model, genome-wide transcriptional profile analysis was conducted, and we found that during piPSC-EC derivation, the synthesis and secretion level of TGF-β as well as the phosphorylation level of Smad2/3 changed dynamically. TGF-β-Smad2/3 signaling activation promoted mesoderm formation and prevented endothelial differentiation. Understanding the regulatory mechanism of iPSC-EC derivation not only paves the way for further optimization, but also provides reference for establishing a cardiovascular drug screening platform and revealing the molecular mechanism of endothelial dysfunction.

Differential impact of TGFβ/SMAD signaling activity elicited by Activin A and Nodal on endoderm differentiation of epiblast stem cells

Allocation of cells to an endodermal fate in the gastrulating embryo is driven by Nodal signaling and consequent activation of TGFβ pathway. In vitro methodologies striving to recapitulate the process of endoderm differentiation, however, use TGFβ family member Activin in place of Nodal. This is despite Activin not known to have an in vivo role in endoderm differentiation. In this study, five epiblast stem cell lines were subjected to directed differentiation using both Activin A and Nodal to induce endodermal fate. A reporter line harboring endoderm markers FoxA2 and Sox17 was further analyzed for TGFβ pathway activation and WNT response. We demonstrated that Activin A-treated cells remain more primitive streak-like when compared to Nodal-treated cells that have a molecular profile suggestive of more advanced differentiation. Activin A elicited a robust TGFβ/SMAD activity, enhanced WNT signaling activity and promoted the generation of DE precursors. Nodal treatment resulted in lower TGFβ/SMAD activity, and a weaker, sustained WNT response, and ultimately failed to upregulate endoderm markers. This is despite signaling response resembling more closely the activity seen in vivo. These findings emphasize the importance of understanding the downstream activities of Activin A and Nodal signaling in directing in vitro endoderm differentiation of primed-state epiblast stem cells.

Functional Recellularization of Acellular Rat Liver Scaffold by Induced Pluripotent Stem Cells: Molecular Evidence for Wnt/B-Catenin Upregulation

BACKGROUND

Liver transplantation remains the only viable therapy for liver failure but has a severely restricted utility. Here, we aimed to decellularize rat livers to form acellular 3D bio-scaffolds suitable for seeding with induced pluripotent cells (iPSCs) as a tool to investigate the role of Wnt/β-catenin signaling in liver development and generation.

METHODS

Dissected rat livers were randomly divided into three groups: I (control); II (decellularized scaffolds) and III (recellularized scaffolds). Liver decellularization was established via an adapted perfusion procedure and assessed through the measurement of extracellular matrix (ECM) proteins and DNA content. Liver recellularization was assessed through histological examination and measurement of transcript levels of Wnt/β-catenin pathway, hepatogenesis, liver-specific microRNAs and growth factors essential for liver development. Adult rat liver decellularization was confirmed by the maintenance of ECM proteins and persistence of growth factors essential for liver regeneration.

RESULTS

iPSCs seeded rat decellularized livers displayed upregulated transcript expression of Wnt/β-catenin pathway-related, growth factors, and liver specification genes. Further, recellularized livers displayed restored liver-specific functions including albumin secretion and urea synthesis.

CONCLUSION

This establishes proof-of-principle for the generation of three-dimensional liver organ scaffolds as grafts and functional re-establishment.

Gastric Organoids: Progress and Remaining Challenges

The stomach is a complex and physiologically necessary organ, yet large differences in physiology between mouse and human stomachs have impeded translation of physiological discoveries and drug screens performed using murine gastric tissues. Gastric cancer (GC) is a global health threat, with a high mortality rate and limited treatment options. The heterogeneous nature of GC makes it poorly suited for current "one size fits all" standard treatments. In this review, we discuss the rapidly evolving field of gastric organoids, with a focus on studies expanding cultures from primary human tissues and describing the benefits of mouse organoid models. We introduce the differing methods for culturing healthy gastric tissue from adult tissues or pluripotent stem cells, discuss the promise these systems have for preclinical drug screens, and highlight applications of organoids for precision medicine. Finally, we discuss the limitations of these models and look to the future to present potential ways gastric organoids will advance treatment options for patients with GC.

Modeling endodermal organ development and diseases using human pluripotent stem cell-derived organoids

Recent advances in development of protocols for directed differentiation from human pluripotent stem cells (hPSCs) to defined lineages, in combination with 3D organoid technology, have facilitated the generation of various endoderm-derived organoids for in vitro modeling of human gastrointestinal development and associated diseases. In this review, we discuss current state-of-the-art strategies for generating hPSC-derived endodermal organoids including stomach, liver, pancreatic, small intestine, and colonic organoids. We also review the advantages of using this system to model various human diseases and evaluate the shortcomings of this technology. Finally, we emphasize how other technologies, such as genome editing and bioengineering, can be incorporated into the 3D hPSC-organoid models to generate even more robust and powerful platforms for understanding human organ development and disease modeling.

Protocol for the generation of pancreatic and hepatic progenitors from human pluripotent stem cells for gene regulatory assays

This protocol describes the detailed procedures for utilizing human pluripotent stem cells (hPSCs) for pancreatic progenitor and hepatic differentiation, followed by the application of hPSC-derived cells in a luciferase reporter-based assay to study gene regulation. The generated hPSC-derived cells have been shown to achieve morphologies and gene expression profiles specific to their differentiated cell types, and subsequent luciferase assay has been shown to effectively elucidate the role of disease-relevant gene variants. Therefore, this protocol provides a valuable approach for pancreatic and liver disease modeling.

For complete details on the use and execution of this protocol, please refer to Ng et al. (2019).

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Protocol generates pancreatic and hepatic progenitors from human pluripotent stem cells

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Describes use of luciferase reporter assay to study gene regulation in hPSC-derived cells

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Enables the study of gene regulation during pancreatic and liver development

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Provides a valuable approach for modeling pancreatic and liver diseases

Molecular Aspects of Regeneration Mechanisms in Holothurians

Holothurians, or sea cucumbers, belong to the phylum Echinodermata. They show good regenerative abilities. The present review provides an analysis of available data on the molecular aspects of regeneration mechanisms in holothurians. The genes and signaling pathways activated during the asexual reproduction and the formation of the anterior and posterior parts of the body, as well as the molecular mechanisms that provide regeneration of the nervous and digestive systems, are considered here. Damage causes a strong stress response, the signs of which are recorded even at late regeneration stages. In holothurian tissues, the concentrations of reactive oxygen species and antioxidant enzymes increase. Furthermore, the cellular and humoral components of the immune system are activated. Extracellular matrix remodeling and Wnt signaling play a major role in the regeneration in holothurians. All available morphological and molecular data show that the dedifferentiation of specialized cells in the remnant of the organ and the epithelial morphogenesis constitute the basis of regeneration in holothurians. However, depending on the type of damage, the mechanisms of regeneration may differ significantly in the spatial organization of regeneration process, the involvement of different cell types, and the depth of reprogramming of their genome (dedifferentiation or transdifferentiation).

The Canonical Wnt Pathway as a Key Regulator in Liver Development, Differentiation and Homeostatic Renewal

The canonical Wnt (Wnt/β-catenin) signalling pathway is highly conserved and plays a critical role in regulating cellular processes both during development and in adult tissue homeostasis. The Wnt/β-catenin signalling pathway is vital for correct body patterning and is involved in fate specification of the gut tube, the primitive precursor of liver. In adults, the Wnt/β-catenin pathway is increasingly recognised as an important regulator of metabolic zonation, homeostatic renewal and regeneration in response to injury throughout the liver. Herein, we review recent developments relating to the key role of the pathway in the patterning and fate specification of the liver, in the directed differentiation of pluripotent stem cells into hepatocytes and in governing proliferation and zonation in the adult liver. We pay particular attention to recent contributions to the controversy surrounding homeostatic renewal and proliferation in response to injury. Furthermore, we discuss how crosstalk between the Wnt/β-catenin and Hedgehog (Hh) and hypoxia inducible factor (HIF) pathways works to maintain liver homeostasis. Advancing our understanding of this pathway will benefit our ability to model disease, screen drugs and generate tissue and organ replacements for regenerative medicine.

Intestinal Organoids Generated from Human Pluripotent Stem Cells

The gastrointestinal system is one of the most complex organ systems in the human body, and consists of numerous cell types originating from three germ layers. To understand intestinal development and homeostasis and elucidate the pathogenesis of intestinal disorders, including unidentified diseases, several in vitro models have been developed. Human pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have remarkable developmental plasticity and possess the potential for a wide variety of applications. Three-dimensional organs, termed organoids and produced in vitro by PSCs, contain not only epithelium but also mesenchymal tissue and partially recapitulate intestinal functions. Such intestinal organoids have begun to be applied in disease models and drug development and have contributed to a detailed analysis of molecular interactions and findings in the synergistic development of biomedicine for human digestive organs. In this review, we describe gastrointestinal organoid technology derived from PSCs and consider its potential applications.

Case-control study on the association between the GATA2 gene and premature myocardial infarction in the Iranian population

In recent decades, due to the high prevalence of coronary artery disease (CAD) and myocardial infarction (MI), numerous studies have attempted to elucidate genetic contributing factors in these complex disorders. A very interesting gene in this regard is GATA-binding protein 2 (GATA2), an important regulator of various gene expressions in vascular endothelial cells. Accordingly, the association of different GATA2 polymorphisms with CAD and MI has already been evaluated. Rs2713604 is a genetic marker whose association with CAD has not been reproduced in previous studies. Considering the importance of replicating the initial association, the present case-control study aimed to examine the association of this intronic variant with premature MI in a sample of the Iranian population. In this study, 193 participants from Jahrom Hospital (Jahrom, Iran) were consecutively recruited during a 1.5-year period, and, following blood sampling, genomic DNA was extracted. We then proceeded to genotype rs2713604 using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and statistically analyzed the data. After adjustment for hyperlipidemia, hypertension, and type 2 diabetes mellitus, the results of the multivariate regression analysis showed no significant association between rs2713604 and premature MI. Interestingly, the risk allele (A-allele) of rs2713604 displayed a slightly higher frequency among controls compared to cases.

The Expression and Functional Roles of miRNAs in Embryonic and Lineage-Specific Stem Cells

The discovery of small non-coding RNAs began an interesting era in cellular and molecular biology. To date, miRNAs are the best recognized non-coding RNAs for maintenance and differentiation of pluripotent stem cells including embryonic stem cells (ES), induced pluripotent stem cells (iPSC), and cancer stem cells. ES cells are defined by their ability to self-renew, teratoma formation, and to produce numerous types of differentiated cells. Dual capacity of ES cells for self-renewal and differentiation is controlled by specific interaction with the neighboring cells and intrinsic signaling pathways from the level of transcription to translation. The ES cells have been the suitable model for evaluating the function of non-coding RNAs and in specific miRNAs. So far, the general function of the miRNAs in ES cells has been assessed in mammalian and non-mammalian stem cells. Nowadays, the evolution of sequencing technology led to the discovery of numerous miRNAs in human and mouse ES cells that their expression levels significantly changes during proliferation and differentiation. Several miRNAs have been identified in ectoderm, mesoderm, and endoderm cells, as well. This review would focus on recent knowledge about the expression and functional roles of miRNAs in embryonic and lineage-specific stem cells. It also describes that miRNAs might have essential roles in orchestrating the Waddington's landscape structure during development.

The endoderm: a divergent cell lineage with many commonalities

The endoderm is a progenitor tissue that, in humans, gives rise to the majority of internal organs. Over the past few decades, genetic studies have identified many of the upstream signals specifying endoderm identity in different model systems, revealing them to be divergent from invertebrates to vertebrates. However, more recent studies of the cell behaviours driving endodermal morphogenesis have revealed a surprising number of shared features, including cells undergoing epithelial-to-mesenchymal transitions (EMTs), collective cell migration, and mesenchymal-to-epithelial transitions (METs). In this Review, we highlight how cross-organismal studies of endoderm morphogenesis provide a useful perspective that can move our understanding of this fascinating tissue forward.

Generation of human antral and fundic gastric organoids from pluripotent stem cells

The human stomach contains two primary domains: the corpus, which contains the fundic epithelium, and the antrum. Each of these domains has distinct cell types and functions, and therefore each presents with unique disease pathologies. Here, we detail two protocols to differentiate human pluripotent stem cells (hPSCs) into human gastric organoids (hGOs) that recapitulate both domains. Both protocols begin with the differentiation of hPSCs into definitive endoderm (DE) using activin A, followed by the generation of free-floating 3D posterior foregut spheroids using FGF4, Wnt pathway agonist CHIR99021 (CHIR), BMP pathway antagonist Noggin, and retinoic acid. Embedding spheroids in Matrigel and continuing 3D growth in epidermal growth factor (EGF)-containing medium for 4 weeks results in antral hGOs (hAGOs). To obtain fundic hGOs (hFGOs), spheroids are additionally treated with CHIR and FGF10. Induced differentiation of acid-secreting parietal cells in hFGOs requires temporal treatment of BMP4 and the MEK inhibitor PD0325901 for 48 h on protocol day 30. In total, it takes ~34 d to generate hGOs from hPSCs. To date, this is the only approach that generates functional human differentiated gastric cells de novo from hPSCs.

Modelling the endocrine pancreas in health and disease

Diabetes mellitus is a multifactorial disease affecting increasing numbers of patients worldwide. Progression to insulin-dependent diabetes mellitus is characterized by the loss or dysfunction of pancreatic β-cells, but the pathomechanisms underlying β-cell failure in type 1 diabetes mellitus and type 2 diabetes mellitus are still poorly defined. Regeneration of β-cell mass from residual islet cells or replacement by β-like cells derived from stem cells holds great promise to stop or reverse disease progression. However, the development of new treatment options is hampered by our limited understanding of human pancreas organogenesis due to the restricted access to primary tissues. Therefore, the challenge is to translate results obtained from preclinical model systems to humans, which requires comparative modelling of β-cell biology in health and disease. Here, we discuss diverse modelling systems across different species that provide spatial and temporal resolution of cellular and molecular mechanisms to understand the evolutionary conserved genotype-phenotype relationship and translate them to humans. In addition, we summarize the latest knowledge on organoids, stem cell differentiation platforms, primary micro-islets and pseudo-islets, bioengineering and microfluidic systems for studying human pancreas development and homeostasis ex vivo. These new modelling systems and platforms have opened novel avenues for exploring the developmental trajectory, physiology, biology and pathology of the human pancreas.

Esophageal Organoids from Human Pluripotent Stem Cells Delineate Sox2 Functions during Esophageal Specification

Tracheal and esophageal disorders are prevalent in humans and difficult to accurately model in mice. We therefore established a three-dimensional organoid model of esophageal development through directed differentiation of human pluripotent stem cells. Sequential manipulation of bone morphogenic protein (BMP), Wnt, and RA signaling pathways was required to pattern definitive endoderm into foregut, anterior foregut (AFG), and dorsal AFG spheroids. Dorsal AFG spheroids grown in a 3D matrix formed human esophageal organoids (HEOs), and HEO cells could be transitioned into two-dimensional cultures and grown as esophageal organotypic rafts. In both configurations, esophageal tissues had proliferative basal progenitors and a differentiated stratified squamous epithelium. Using HEO cultures to model human esophageal birth defects, we identified that Sox2 promotes esophageal specification in part through repressing Wnt signaling in dorsal AFG and promoting survival. Consistently, Sox2 ablation in mice causes esophageal agenesis. Thus, HEOs present a powerful platform for modeling human pathologies and tissue engineering.

Cell migration in the Xenopus gastrula

Xenopus gastrulation movements are in large part based on the rearrangement of cells by differential cell-on-cell migration within multilayered tissues. Different patterns of migration-based cell intercalation drive endoderm and mesoderm internalization and their positioning along their prospective body axes. C-cadherin, fibronectin, integrins, and focal contact components are expressed in all gastrula cells and play putative roles in cell-on-cell migration, but their actual functions in this respect are not yet understood. The gastrula can be subdivided into two motility domains, and in the vegetal, migratory domain, two modes of cell migration are discerned. Vegetal endoderm cells show ingression-type migration, a variant of amoeboid migration characterized by the lack of locomotory protrusions and by macropinocytosis as a mechanism of trailing edge resorption. Mesendoderm and prechordal mesoderm cells use lamellipodia in a mesenchymal mode of migration. Gastrula cell motility can be dissected into traits, such as cell polarity, adhesion, mobility, or protrusive activity, which are controlled separately yet in complex, combinatorial ways. Cells can instantaneously switch between different combinations of traits, showing plasticity as they respond to substratum properties. This article is categorized under: Early Embryonic Development > Gastrulation and Neurulation.

Molecular mechanisms of fission in echinoderms: Transcriptome analysis

Echinoderms are capable of asexual reproduction by fission. An individual divides into parts due to changes in the strength of connective tissue of the body wall. The structure of connective tissue and the mechanisms of variations in its strength in echinoderms remain poorly studied. An analysis of transcriptomes of individuals during the process of fission provides a new opportunity to understand the mechanisms of connective tissue mutability. In the holothurian Cladolabes schmeltzii, we have found a rather complex organization of connective tissue. Transcripts of genes encoding a wide range of structural proteins of extracellular matrix, as well as various proteases and their inhibitors, have been discovered. All these molecules may constitute a part of the mechanism of connective tissue mutability. According to our data, the extracellular matrix of echinoderms is substantially distinguished from that of vertebrates by the lack of elastin, fibronectins, and tenascins. In case of fission, a large number of genes of transcription factors and components of different signaling pathways are expressed. Products of these genes are probably involved in regulation of asexual reproduction, connective tissue mutability, and preparation of tissues for subsequent regeneration. It has been shown that holothurian tensilins are a special group of tissue inhibitors of metalloproteinases, which has formed within the class Holothuroidea and is absent from other echinoderms. Our data can serve a basis for the further study of the mechanisms of extracellular matrix mutability, as well as the mechanisms responsible for asexual reproduction in echinoderms.

Molecular regulation of Nodal signaling during mesendoderm formation

One of the most important events during vertebrate embryogenesis is the formation or specification of the three germ layers, endoderm, mesoderm, and ectoderm. After a series of rapid cleavages, embryos form the mesendoderm and ectoderm during late blastulation and early gastrulation. The mesendoderm then further differentiates into the mesoderm and endoderm. Nodal, a member of the transforming growth factor β (TGF-β) superfamily, plays a pivotal role in mesendoderm formation by regulating the expression of a number of critical transcription factors, including Mix-like, GATA, Sox, and Fox. Because the Nodal signal transduction pathway is well-characterized, increasing effort has been made to delineate the spatiotemporal modulation of Nodal signaling during embryonic development. In this review, we summarize the recent progress delineating molecular regulation of Nodal signal intensity and duration during mesendoderm formation.

An arduous journey from human pluripotent stem cells to functional pancreatic β cells

Type 1 and type 2 diabetes are caused by a destruction and decrease in the number of functional insulin-producing β cells, respectively; therefore, the generation of functional β cells from human embryonic stem cells and human induced pluripotent stem cells, collectively known as human pluripotent stem cells (hPSCs), for potential cell replacement therapy and disease modelling is an intensely investigated area. Recent scientific breakthroughs enabled derivation of large quantities of human pancreatic β-like cells in vitro, although with varied glucose-stimulated insulin secretion kinetics. In the present review, we comprehensively summarize, compare and critically analyze the intricacies of these developing technologies, including differentiation platforms, robustness of protocols, and methodologies used to characterize hPSC-derived β-like cells. We also discuss experimental issues that need to be resolved before these β-like cells can be used clinically.

Epithelial-Myeloid cell crosstalk regulates acinar cell plasticity and pancreatic remodeling in mice

Dedifferentiation of acini to duct-like cells occurs during the physiologic damage response in the pancreas, but this process can be co-opted by oncogenic Kras to drive carcinogenesis. Myeloid cells infiltrate the pancreas during the onset of pancreatic cancer, and promote carcinogenesis. Here, we show that the function of infiltrating myeloid cells is regulated by oncogenic Kras expressed in epithelial cells. In the presence of oncogenic Kras, myeloid cells promote acinar dedifferentiation and carcinogenesis. Upon inactivation of oncogenic Kras, myeloid cells promote re-differentiation of acinar cells, remodeling of the fibrotic stroma and tissue repair. Intriguingly, both aspects of myeloid cell activity depend, at least in part, on activation of EGFR/MAPK signaling, with different subsets of ligands and receptors in different target cells promoting carcinogenesis or repair, respectively. Thus, the cross-talk between epithelial cells and infiltrating myeloid cells determines the balance between tissue repair and carcinogenesis in the pancreas.

EphrinB1/EphB3b Coordinate Bidirectional Epithelial-Mesenchymal Interactions Controlling Liver Morphogenesis and Laterality

Positioning organs in the body often requires the movement of multiple tissues, yet the molecular and cellular mechanisms coordinating such movements are largely unknown. Here, we show that bidirectional signaling between EphrinB1 and EphB3b coordinates the movements of the hepatic endoderm and adjacent lateral plate mesoderm (LPM), resulting in asymmetric positioning of the zebrafish liver. EphrinB1 in hepatoblasts regulates directional migration and mediates interactions with the LPM, where EphB3b controls polarity and movement of the LPM. EphB3b in the LPM concomitantly repels hepatoblasts to move leftward into the liver bud. Cellular protrusions controlled by Eph/Ephrin signaling mediate hepatoblast motility and long-distance cell-cell contacts with the LPM beyond immediate tissue interfaces. Mechanistically, intracellular EphrinB1 domains mediate EphB3b-independent hepatoblast extension formation, while EpB3b interactions cause their destabilization. We propose that bidirectional short- and long-distance cell interactions between epithelial and mesenchyme-like tissues coordinate liver bud formation and laterality via cell repulsion.

Developmental expression and regulation of flavin-containing monooxygenase by the unfolded protein response in Japanese medaka (Oryzias latipes)

Flavin-containing monooxygenases (FMOs) play a key role in xenobiotic metabolism, are regulated by environmental conditions, and are differentially regulated during mammalian development. Japanese medaka (Oryzias latipes) are a common model organism for toxicological studies. The goal of the current research was to characterize developmental expression and regulation of FMOs in Japanese medaka embryos to better understand the role of FMOs in this model species. Five putative medaka fmos were characterized from the medaka genome through the National Center for Biotechnology Information (NCBI) database by protein motifs and alignments, then identified as fmo4, fmo5A, fmo5B, fmo5C and fmo5D for the current study. Fmo gene expression was analyzed at 1dpf, 3dpf, 6dpf and 9dpf and distinct developmental patterns of expression were observed. Fmo4 and fmo5D increased 3-fold during mid organogenesis (6dpf), while fmo5B and fmo5C decreased significantly in early organogenesis (3dpf) and fmo5A was unaltered. Promoter analysis was performed for transcription factor binding sites and indicated regulation by developmental factors and a role for the unfolded protein response in fmo modulation. Fmo regulation by the UPR was assessed with treatments of 1μg/ml, 2μg/ml, and 4μg/ml Tunicamycin (Tm), and 2mM and 4mM dithiothreitol (DTT), well-known inducers of endoplasmic reticulum stress, for 24h from 5-6dpf. High concentrations to Tm induced fmo4 and fmo5A up to two-fold, while DTT significantly decreased expression of fmo5A, fmo5B, and fmo5C. Results suggest that medaka fmos are variably regulated by the UPR during organogenesis with variable developmental expression, and suggesting potential stage-dependent activation or detoxification of xenobiotics.

Gene regulatory networks in differentiation and direct reprogramming of hepatic cells

Liver development proceeds by sequential steps during which gene regulatory networks (GRNs) determine differentiation and maturation of hepatic cells. Characterizing the architecture and dynamics of these networks is essential for understanding how cell fate decisions are made during development, and for recapitulating these processes during in vitro production of liver cells for toxicology studies, disease modelling and regenerative therapy. Here we review the GRNs that control key steps of liver development and lead to differentiation of hepatocytes and cholangiocytes in mammals. We focus on GRNs determining cell fate decisions and analyse subcircuitry motifs that may confer specific dynamic properties to the networks. Finally, we put our analysis in the perspective of recent attempts to directly reprogram cells to hepatocytes by forced expression of transcription factors.

In vitro patterning of pluripotent stem cell-derived intestine recapitulates in vivo human development

The intestine plays a central role in digestion, nutrient absorption and metabolism, with individual regions of the intestine having distinct functional roles. Many examples of region-specific gene expression in the adult intestine are known, but how intestinal regional identity is established during development is a largely unresolved issue. Here, we have identified several genes that are expressed in a region-specific manner in the developing human intestine. Using human embryonic stem cell-derived intestinal organoids, we demonstrate that the duration of exposure to active FGF and WNT signaling controls regional identity. Short-term exposure to FGF4 and CHIR99021 (a GSK3β inhibitor that stabilizes β-catenin) resulted in organoids with gene expression patterns similar to developing human duodenum, whereas longer exposure resulted in organoids similar to ileum. When region-specific organoids were transplanted into immunocompromised mice, duodenum-like organoids and ileum-like organoids retained their regional identity, demonstrating that regional identity of organoids is stable after initial patterning occurs. This work provides insights into the mechanisms that control regional specification of the developing human intestine and provides new tools for basic and translational research.

Summary: Human embryonic stem cell-derived intestinal organoids can be patterned into duodenum-like or ileum-like tissue, recapitulating in vivo human development.

Assessment of Toxicological Perturbations and Variants of Pancreatic Islet Development in the Zebrafish Model

The pancreatic islets, largely comprised of insulin-producing beta cells, play a critical role in endocrine signaling and glucose homeostasis. Because they have low levels of antioxidant defenses and a high perfusion rate, the endocrine islets may be a highly susceptible target tissue of chemical exposures. However, this endpoint, as well as the integrity of the surrounding exocrine pancreas, is often overlooked in studies of developmental toxicology. Disruption of development by toxicants can alter cell fate and migration, resulting in structural alterations that are difficult to detect in mammalian embryo systems, but that are easily observed in the zebrafish embryo model (Danio rerio). Using endogenously expressed fluorescent protein markers for developing zebrafish beta cells and exocrine pancreas tissue, we documented differences in islet area and incidence rates of islet morphological variants in zebrafish embryos between 48 and 96 h post fertilization (hpf), raised under control conditions commonly used in embryotoxicity assays. We identified critical windows for chemical exposures during which increased incidences of endocrine pancreas abnormalities were observed following exposure to cyclopamine (2–12 hpf), Mono-2-ethylhexyl phthalate (MEHP) (3–48 hpf), and Perfluorooctanesulfonic acid (PFOS) (3–48 hpf). Both islet area and length of the exocrine pancreas were sensitive to oxidative stress from exposure to the oxidant tert-butyl hydroperoxide during a highly proliferative critical window (72 hpf). Finally, pancreatic dysmorphogenesis following developmental exposures is discussed with respect to human disease.

Reverse engineering liver buds through self-driven condensation and organization towards medical application

The self-organizing tissue-based approach coupled with induced pluripotent stem (iPS) cell technology is evolving as a promising field for designing organoids in culture and is expected to achieve valuable practical outcomes in regenerative medicine and drug development. Organoids show properties of functional organs and represent an alternative to cell models in conventional two-dimensional differentiation platforms; moreover, organoids can be used to investigate mechanisms of development and disease, drug discovery and toxicity assessment. Towards a more complex and advanced organoid model, it is essential to incorporate multiple cell lineages including developing vessels. Using a self-condensation method, we recently demonstrated self-organizing "organ buds" of diverse systems together with human mesenchymal and endothelial progenitors, proposing a new reverse engineering method to generate a more complex organoid structure. In this section, we review characters of organ bud technology based on two important principles: self-condensation and self-organization focusing on liver bud as an example, and discuss their practicality in regenerative medicine and potential as research tools for developmental biology and drug discovery.

Naringenin enhances the efficacy of human embryonic stem cell-derived pancreatic endoderm in treating gestational diabetes mellitus mice

Gestational diabetes mellitus (GDM) is a disease commonly occurs during mid to late pregnancy with pathologies such as hyperglycemia, hyperinsulinemia and mal-development of fetus. We have previously demonstrated that pancreatic endoderm (PE) derived from human embryonic stem cells (hESCs) effectively alleviated diabetic symptoms in a mouse model of GDM, although the clinical efficacy was limited due to oxidative stress. In this study, using the anti-oxidant agent naringenin, we aimed to further enhance the efficacy of hESC-derived PE transplant. Insulin-secreting PE was differentiated from hESCs, which were then transplanted into GDM mice. Naringenin was administered to mice receiving the PE transplant, with sham operated mice serving as negative control, to assess its effect on alleviation of GDM symptoms. We found that naringenin supplement further improved insulin response, glucose metabolism and reproductive outcome of the PE-transplanted female mice. Our new findings further potentiates the feasibility of using differentiated hESCs to treat GDM, in which anti-oxidative agent such as naringenin could greatly enhance the clinical efficacy of stem cell based therapies.

PTF1a Activity in Enriched Posterior Foregut Endoderm, but Not Definitive Endoderm, Leads to Enhanced Pancreatic Differentiation in an In Vitro Mouse ESC-Based Model

Transcription factors are tools repetitively used by the embryo to generate a variety of lineages. Hence, their context of activation is an important determinant of their ability to specifically trigger certain cell fates, but not others. The context is also consequential when considering directing differentiation of embryonic stem cells (ESCs). In this study, we sought to assess the context of pancreatic transcription factor 1a (PTF1a) activation in reference to its propancreatic effects in mouse ESCs (mESCs). We hypothesized that an enriched endodermal population would respond to PTF1a and trigger the pancreatic program more effectively than a spontaneously differentiated population. Using an in vitro model of pancreas development that we recently established, we found that inducing PTF1a in highly enriched definitive endoderm did not promote pancreatic differentiation but induction in more differentiated endoderm, specifically posterior foregut endoderm, did form pancreatic progenitors. These progenitors never underwent terminal differentiation to endocrine or acinar phenotype. However, a short 3D culture period, prior to PTF1a induction, led to the generation of monohormonal insulin(+) cells and amylase-expressing cells. Our findings suggest that enriched posterior foregut endoderm is competent to respond to PTF1a's propancreatic activity; but a 3D culture environment is essential for terminal differentiation of pancreatic progenitors.

From Endoderm to Liver Bud: Paradigms of Cell Type Specification and Tissue Morphogenesis

The early specification, rapid growth and morphogenesis, and conserved functions of the embryonic liver across diverse model organisms have made the system an experimentally facile paradigm for understanding basic regulatory mechanisms that govern cell differentiation and organogenesis. This essay highlights concepts that have emerged from studies of the discrete steps of foregut endoderm development into the liver bud, as well as from modeling the steps via embryonic stem cell differentiation. Such concepts include understanding the chromatin basis for the competence of progenitor cells to develop into specific lineages; the importance of combinatorial signaling from different sources to induce cell fates; the impact of inductive signaling on preexisting chromatin states; the ability of separately specified domains of cells to merge into a common tissue; and the marked cell biological dynamics, including interactions with the developing vasculature, which establish the initial morphogenesis and patterning of a tissue. The principles gleaned from these studies, focusing on the 2 days it takes for the endoderm to develop into a liver bud, should be instructive for many other organogenic systems and for manipulating tissues in regenerative contexts for biomedical purposes.

miR-410 enhanced hESC-derived pancreatic endoderm transplant to alleviate gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a condition commonly encountered during mid to late pregnancy with pathologic manifestations including hyperglycemia, hyperinsulinemia, insulin resistance, and fetal mal-development. The deficit and dysfunction of insulin secreting β-cells are signature symptoms for GDM. Pancreatic progenitors derived from human embryonic stem cells (hESCs) were shown to be able to effectively treat diabetes in mice. In this study, we first identified that microRNA-410 (miR-410) directly targets lactate dehydrogenase A (LDHA), a gene selectively repressed in normal insulin secreting β-cells. hESCs that can be induced to express miR-410 hence keeping LDHA levels in check were then differentiated in vitro into pancreatic endoderm, followed by transplantation into db/+ mouse model of GDM. The transplant greatly improved glucose metabolism and reproductive outcome of the pregnant females suffering from GDM. Our findings describe for the first time the method of combining miRNA with hESCs, providing proof of concept by employing genetically modified stem cell therapy for treating GDM.

Orchestrating liver development

The liver is a central regulator of metabolism, and liver failure thus constitutes a major health burden. Understanding how this complex organ develops during embryogenesis will yield insights into how liver regeneration can be promoted and how functional liver replacement tissue can be engineered. Recent studies of animal models have identified key signaling pathways and complex tissue interactions that progressively generate liver progenitor cells, differentiated lineages and functional tissues. In addition, progress in understanding how these cells interact, and how transcriptional and signaling programs precisely coordinate liver development, has begun to elucidate the molecular mechanisms underlying this complexity. Here, we review the lineage relationships, signaling pathways and transcriptional programs that orchestrate hepatogenesis.

First quantitative high-throughput screen in zebrafish identifies novel pathways for increasing pancreatic β-cell mass

Whole-organism chemical screening can circumvent bottlenecks that impede drug discovery. However, in vivo screens have not attained throughput capacities possible with in vitro assays. We therefore developed a method enabling in vivo high-throughput screening (HTS) in zebrafish, termed automated reporter quantification in vivo (ARQiv). In this study, ARQiv was combined with robotics to fully actualize whole-organism HTS (ARQiv-HTS). In a primary screen, this platform quantified cell-specific fluorescent reporters in >500,000 transgenic zebrafish larvae to identify FDA-approved (Federal Drug Administration) drugs that increased the number of insulin-producing β cells in the pancreas. 24 drugs were confirmed as inducers of endocrine differentiation and/or stimulators of β-cell proliferation. Further, we discovered novel roles for NF-κB signaling in regulating endocrine differentiation and for serotonergic signaling in selectively stimulating β-cell proliferation. These studies demonstrate the power of ARQiv-HTS for drug discovery and provide unique insights into signaling pathways controlling β-cell mass, potential therapeutic targets for treating diabetes.

Efficient endodermal induction of human adipose stem cells using various concentrations of Activin A for hepatic differentiation

Activin A, which is a signaling molecule similar to Nodal, rapidly promotes endoderm induction of both embryonic stem (ES) cells and MSCs. Protocols for hepatic induction exhibit differences in efficiency and reproducibility depending on the specific methods or sources of MSCs. We characterized the effects of Activin A concentration on induction efficiency during hepatic differentiation of MSCs. Human MSCs (hMSCs) were differentiated into a hepatic lineage via a three-step protocol. Cells were first cultured in fetal bovine serum-free MSCs conditioned medium supplemented with Activin A (20, 50, or 100 ng/mL) for 3 days followed by treatment with additional agents. RT-PCR analysis, immunocytochemistry assays, periodic acid and Schiff's solution staining, and ELISAs were performed to confirm hepatic induction of hMSCs. Expression of genes related to the primitive foregut endoderm was observed in cells treated with higher concentration of Activin A. Gene expression related to functional primitive hepatocytes was observed in the early phases of hepatic differentiation. During the early period of the differentiation protocol, greater albumin secretion was observed when cells were treated with higher concentrations of Activin A.

CONCLUSION

Thus, Activin A concentration affects the rate of endoderm induction of hMSCs, and at higher concentrations in vitro.

Gutsy moves in mice: cellular and molecular dynamics of endoderm morphogenesis

Despite the importance of the gut and its accessory organs, our understanding of early endoderm development is still incomplete. Traditionally, endoderm has been difficult to study because of its small size and relative fragility. However, recent advances in live cell imaging technologies have dramatically expanded our understanding of this tissue, adding a new appreciation for the complex molecular and morphogenetic processes that mediate gut formation. Several spatially and molecularly distinct subpopulations have been shown to exist within the endoderm before the onset of gastrulation. Here, we review findings that have uncovered complex cell movements within the endodermal layer, before and during gastrulation, leading to the conclusion that cells from primitive endoderm contribute descendants directly to gut.

Human embryonic stem cell-derived pancreatic endoderm alleviates diabetic pathology and improves reproductive outcome in C57BL/KsJ-Lep(db/+) gestational diabetes mellitus mice

Gestational diabetes mellitus is a condition commonly encountered during mid to late pregnancy with pathologic manifestations including hyperglycemia, hyperinsulinemia, insulin resistance, and fetal maldevelopment. The cause of gestational diabetes mellitus can be attributed to both genetic and environmental factors, hence complicating its diagnosis and treatment. Pancreatic progenitors derived from human embryonic stem cells were shown to be able to effectively treat diabetes in mice. In this study, we have developed a system of treating diabetes using human embryonic stem cell-derived pancreatic endoderm in a mouse model of gestational diabetes mellitus. Human embryonic stem cells were differentiated in vitro into pancreatic endoderm, which were then transplanted into db/+ mice suffering from gestational diabetes mellitus. The transplant greatly improved glucose metabolism and reproductive outcome of the females compared with the control groups. Our findings support the feasibility of using differentiated human embryonic stem cells for treating gestational diabetes mellitus patients.

Expression of stanniocalcin 1 in thyroid side population cells and thyroid cancer cells

BACKGROUND

Mouse thyroid side population (SP) cells consist of a minor population of mouse thyroid cells that may have multipotent thyroid stem cell characteristics. However the nature of thyroid SP cells remains elusive, particularly in relation to thyroid cancer. Stanniocalcin (STC) 1 and 2 are secreted glycoproteins known to regulate serum calcium and phosphate homeostasis. In recent years, the relationship of STC1/2 expression to cancer has been described in various tissues.

METHOD

Microarray analysis was carried out to determine genes up- and down-regulated in thyroid SP cells as compared with non-SP cells. Among genes up-regulated, stanniocalcin 1 (STC1) was chosen for study because of its expression in various thyroid cells by Western blotting and immunohistochemistry.

RESULTS

Gene expression analysis revealed that genes known to be highly expressed in cancer cells and/or involved in cancer invasion/metastasis were markedly up-regulated in SP cells from both intact as well as partial thyroidectomized thyroids. Among these genes, expression of STC1 was found in five human thyroid carcinoma-derived cell lines as revealed by analysis of mRNA and protein, and its expression was inversely correlated with the differentiation status of the cells. Immunohistochemical analysis demonstrated higher expression of STC1 in the thyroid tumor cell line and thyroid tumor tissues from humans and mice.

CONCLUSION

These results suggest that SP cells contain a population of cells that express genes also highly expressed in cancer cells including Stc1, which warrants further study on the role of SP cells and/or STC1 expression in thyroid cancer.

Generating human intestinal tissues from pluripotent stem cells to study development and disease

As one of the largest and most functionally complex organs of the human body, the intestines are primarily responsible for the breakdown and uptake of macromolecules from the lumen and the subsequent excretion of waste from the body. However, the intestine is also an endocrine organ, regulating digestion, metabolism, and feeding behavior. Intricate neuronal, lymphatic, immune, and vascular systems are integrated into the intestine and are required for its digestive and endocrine functions. In addition, the gut houses an extensive population of microbes that play roles in digestion, global metabolism, barrier function, and host-parasite interactions. With such an extensive array of cell types working and performing in one essential organ, derivation of functional intestinal tissues from human pluripotent stem cells (PSCs) represents a significant challenge. Here we will discuss the intricate developmental processes and cell types that are required for assembly of this highly complex organ and how embryonic processes, particularly morphogenesis, have been harnessed to direct differentiation of PSCs into 3-dimensional human intestinal organoids (HIOs) in vitro. We will further describe current uses of HIOs in development and disease research and how additional tissue complexity might be engineered into HIOs for better functionality and disease modeling.

Signalling pathways involved in the process of mesenchymal stem cells differentiating into hepatocytes

End‐stage liver disease can be the termination of acute or chronic liver diseases, with manifestations of liver failure; transplantation is currently an effective treatment for these. However, transplantation is severely limited due to the serious lack of donors, expense, graft rejection and requirement of long‐term immunosuppression. Mesenchymal stem cells (MSCs) have attracted considerable attention as therapeutic tools as they can be obtained with relative ease and expanded in culture, along with features of self‐renewal and multidirectional differentiation. Many scientific groups have sought to use MSCs differentiating into functional hepatocytes to be used in cell transplantation with liver tissue engineering to repair diseased organs. In most of the literature, hepatocyte differentiation refers to use of various additional growth factors and cytokines, such as hepatocyte growth factor (HGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), oncostatin M (OSM) and more, and most are involved in signalling pathway regulation and cell–cell/cell–matrix interactions. Signalling pathways have been shown to play critical roles in embryonic development, tumourigenesis, tumour progression, apoptosis and cell‐fate determination. However, mechanisms of MSCs differentiating into hepatocytes, particularly signalling pathways involved, have not as yet been completely illustrated. In this review, we have focused on progress of signalling pathways associated with mesenchymal stem cells differentiating into hepatocytes along with the stepwise differentiation procedure.

A Combination of Human Embryonic Stem Cell-Derived Pancreatic Endoderm Transplant with LDHA-Repressing miRNA Can Attenuate High-Fat Diet Induced Type II Diabetes in Mice

Type II diabetes mellitus (T2D) is a chronic metabolic disorder that results from defects in both insulin secretion and insulin action. The deficit and dysfunction of insulin secreting β-cell are signature symptom for T2D. Additionally, in pancreatic β-cell, a small group of genes which are abundantly expressed in most other tissues are highly selectively repressed. Lactate dehydrogenase A (LDHA) is one of such genes. Upregulation of LDHA is found in both human T2D and rodent T2D models. In this study, we identified a LDHA-suppressing microRNA (hsa-miR-590-3p) and used it together with human embryonic stem cell (hESC) derived pancreatic endoderm (PE) transplantation into a high-fat diet induced T2D mouse model. The procedure significantly improved glucose metabolism and other symptoms of T2D. Our findings support the potential T2D treatment using the combination of microRNA and hESC-differentiated PE cells.

Embryonic stem cell-derived pancreatic endoderm transplant with MCT1-suppressing miR-495 attenuates type II diabetes in mice

Type 2 diabetes mellitus (T2D) is a chronic metabolic disorder resulting from defects in both insulin secretion and insulin activity. The deficit and dysfunction of insulin secreting β-cells are signature symptoms of T2D. Additionally, in pancreatic β-cells, a small group of genes that are abundantly expressed in most other tissues is highly selectively repressed. Monocarboxylate transporter 1 (MCT1) is one of these genes. In this study, we identified an MCT1-suppressing microRNA (hsa-miR-495) and used this microRNA together with human embryonic stem cell (hESC) derived pancreatic endoderm (PE) cells transplanted into a high-fat diet induced T2D mouse model. Glucose metabolism significantly improved and other symptoms of T2D were attenuated after the procedure. Our findings support the potential for T2D treatment using the combination of microRNA and hESC differentiated PE cells.

Genome-wide view of TGFβ/Foxh1 regulation of the early mesendoderm program

Nodal/TGFβ signaling regulates diverse biological responses. By combining RNA-seq on Foxh1 and Nodal signaling loss-of-function embryos with ChIP-seq of Foxh1 and Smad2/3, we report a comprehensive genome-wide interaction between Foxh1 and Smad2/3 in mediating Nodal signaling during vertebrate mesendoderm development. This study significantly increases the total number of Nodal target genes regulated by Foxh1 and Smad2/3, and reinforces the notion that Foxh1-Smad2/3-mediated Nodal signaling directly coordinates the expression of a cohort of genes involved in the control of gene transcription, signaling pathway modulation and tissue morphogenesis during gastrulation. We also show that Foxh1 may function independently of Nodal signaling, in addition to its role as a transcription factor mediating Nodal signaling via Smad2/3. Finally, we propose an evolutionarily conserved interaction between Foxh1 and PouV, a mechanism observed in Pou5f1-mediated regulation of pluripotency in human embryonic stem and epiblast cells.