Self-renewal of pluripotent embryonic stem cells is mediated via activation of STAT3

RALYL increases hepatocellular carcinoma stemness by sustaining the mRNA stability of TGF-β2

Growing evidences suggest that cancer stem cells exhibit many molecular characteristics and phenotypes similar to their ancestral progenitor cells. In the present study, human embryonic stem cells are induced to differentiate into hepatocytes along hepatic lineages to mimic liver development in vitro. A liver progenitor specific gene, RALY RNA binding protein like (RALYL), is identified. RALYL expression is associated with poor prognosis, poor differentiation, and metastasis in clinical HCC patients. Functional studies reveal that RALYL could promote HCC tumorigenicity, self-renewal, chemoresistance, and metastasis. Moreover, molecular mechanism studies show that RALYL could upregulate TGF-β2 mRNA stability by decreasing N6-methyladenosine (m⁶A) modification. TGF-β signaling and the subsequent PI3K/AKT and STAT3 pathways, upregulated by RALYL, contribute to the enhancement of HCC stemness. Collectively, RALYL is a liver progenitor specific gene and regulates HCC stemness by sustaining TGF-β2 mRNA stability. These findings may inspire precise therapeutic strategies for HCC.

RALYL is a liver progenitor cell-specific gene but its role in hepatocellular carcinoma (HCC) remains unknown. Here, the authors demonstrate that RALYL regulates HCC stemness through upregulation of TGF-β2 mRNA stability by decreasing N6-methyladenosine modification.

Leukemia Inhibitory Factor: A Potential Biomarker and Therapeutic Target in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive, treatment-resistant cancer. Five-year survival rate is about 9%, one of the lowest among all solid tumors. Such a poor outcome is partly due to the limited knowledge of tumor biology, and the resulting lack of effective treatment options and robust predictive biomarkers. The leukemia inhibitory factor (LIF) has recently emerged as a potential biomarker and therapeutic target for PDAC. Accumulating evidence has suggested that LIF plays a role in supporting cancer evolution as a regulator of cell differentiation, renewal and survival. Interestingly, it can be detected in the serum of PDAC patients at higher concentrations than healthy individuals, this supporting its potential value as diagnostic biomarker. Furthermore, preliminary data indicate that testing for LIF serum concentration or tissue expression may help with treatment response monitoring and prognostication. Finally, studies in PDAC mouse models have also shown that LIF may be a valuable therapeutic target, and first-in-human clinical trial is currently ongoing. This article aims to review the available data on the role of LIF in PDAC promotion, and to discuss the evidence supporting its potential role as a biomarker and target of effective anti-cancer therapy in this setting.

Induced pluripotent stem cells from farm animals

The development of the induced pluripotent stem cells (iPSCs) technology has revolutionized the world on the establishment of pluripotent stem cells (PSCs) across a great variety of animal species. Generation of iPSCs from domesticated animals would provide unrestricted cell resources for the study of embryonic development and cell differentiation of these species, for screening and establishing desired traits for sustainable agricultural production, and as veterinary and preclinical therapeutic tools for animal and human diseases. Induced PSCs from domesticated animals thus harbor enormous scientific, economical, and societal values. Although much progress has been made toward the generation of PSCs from these species, major obstacles remain precluding the exclamation of the establishment of bona fide iPSCs. The most prominent of them remain the inability of these cells to silence exogenous reprogramming factors, the obvious reliance on exogenous factors for their self-renewal, and the restricted development potential in vivo. In this review, we summarize the history and current progress in domestic farm animal iPSC generation, with a focus on swine, ruminants (cattle, ovine, and caprine), horses, and avian species (quails and chickens). We also discuss the problems associated with the farm animal iPSCs and potential future directions toward the complete reprogramming of somatic cells from farm animals.

OCT4 induces embryonic pluripotency via STAT3 signaling and metabolic mechanisms

OCT4 is a fundamental component of the molecular circuitry governing pluripotency in vivo and in vitro. To determine how OCT4 establishes and protects the pluripotent lineage in the embryo, we used comparative single-cell transcriptomics and quantitative immunofluorescence on control and OCT4 null blastocyst inner cell masses at two developmental stages. Surprisingly, activation of most pluripotency-associated transcription factors in the early mouse embryo occurs independently of OCT4, with the exception of the JAK/STAT signaling machinery. Concurrently, OCT4 null inner cell masses ectopically activate a subset of trophectoderm-associated genes. Inspection of metabolic pathways implicates the regulation of rate-limiting glycolytic enzymes by OCT4, consistent with a role in sustaining glycolysis. Furthermore, up-regulation of the lysosomal pathway was specifically detected in OCT4 null embryos. This finding implicates a requirement for OCT4 in the production of normal trophectoderm. Collectively, our findings uncover regulation of cellular metabolism and biophysical properties as mechanisms by which OCT4 instructs pluripotency.

Mammalian SWI/SNF Chromatin Remodeling Complexes in Embryonic Stem Cells: Regulating the Balance Between Pluripotency and Differentiation

The unique capability of embryonic stem cells (ESCs) to maintain and adjust the equilibrium between self-renewal and multi-lineage cellular differentiation contributes indispensably to the integrity of all developmental processes, leading to the advent of an organism in its adult form. The ESC fate decision to favor self-renewal or differentiation into specific cellular lineages largely depends on transcriptome modulations through gene expression regulations. Chromatin remodeling complexes play instrumental roles to promote chromatin structural changes resulting in gene expression changes that are key to the ESC fate choices governing the equilibrium between pluripotency and differentiation. BAF (Brg/Brahma-associated factors) or mammalian SWI/SNF complexes employ energy generated by ATP hydrolysis to change chromatin states, thereby governing the accessibility of transcriptional regulators that ultimately affect transcriptome and cell fate. Interestingly, the requirement of BAF complex in self-renewal and differentiation of ESCs has been recently shown by genetic studies through gene expression modulations of various BAF components in ESCs, although the precise molecular mechanisms by which BAF complex influences ESC fate choice remain largely underexplored. This review surveys these recent progresses of BAF complex on ESC functions, with a focus on its role of conditioning the pluripotency and differentiation balance of ESCs. A discussion of the mechanistic bases underlying the genetic requirements for BAF in ESC biology as well as the outcomes of its interplays with key transcription factors or other chromatin remodelers in ESCs will be highlighted.

BAF Complex in Embryonic Stem Cells and Early Embryonic Development

Embryonic stem cells (ESCs) can self-renew indefinitely and maintain their pluripotency status. The pluripotency gene regulatory network is critical in controlling these properties and particularly chromatin remodeling complexes. In this review, we summarize the research progresses of the functional and mechanistic studies of BAF complex in mouse ESCs and early embryonic development. A discussion of the mechanistic bases underlying the distinct phenotypes upon the deletion of different BAF subunits in ESCs and embryos will be highlighted.

Essential roles of insulin and IGF-1 receptors during embryonic lineage development

The insulin and insulin-like growth factor-1 (IGF-1) receptors are important for the growth and development of embryonic tissues. To directly define their roles in the maintenance of pluripotency and differentiation of stem cells, we knocked out both receptors in induced pluripotent stem cells (iPSCs). iPSCs lacking both insulin and IGF-1 receptors (double knockout, DKO) exhibited preserved pluripotency potential despite decreased expression of transcription factors Lin28a and Tbx3 compared to control iPSCs. While embryoid body and teratoma assays revealed an intact ability of DKO iPSCs to form all three germ layers, the latter were composed of primitive neuroectodermal tumor-like cells in the DKO group. RNA-seq analyses of control vs DKO iPSCs revealed differential regulation of pluripotency, developmental, E2F1, and apoptosis pathways. Signaling analyses pointed to downregulation of the AKT/mTOR pathway and upregulation of the STAT3 pathway in DKO iPSCs in the basal state and following stimulation with insulin/IGF-1. Directed differentiation toward the three lineages was dysregulated in DKO iPSCs, with significant downregulation of key markers (Cebpα, Fas, Pparγ, and Fsp27) in adipocytes and transcription factors (Ngn3, Isl1, Pax6, and Neurod1) in pancreatic endocrine progenitors. Furthermore, differentiated pancreatic endocrine progenitor cells from DKO iPSCs showed increased apoptosis. We conclude that insulin and insulin-like growth factor-1 receptors are indispensable for normal lineage development and perturbations in the function and signaling of these receptors leads to upregulation of alternative compensatory pathways to maintain pluripotency.

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Insulin and IGF-1 receptor signaling regulate the expression of pluripotency genes Lin28 and Tbx3.

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The STAT3 pathway is upregulated in DKO iPSCs.

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RNA-seq analyses revealed key developmental and apoptosis pathways regulated by insulin and IGF-1 receptors.

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Lineage development was dysregulated in DKO iPSCs with downregulation of key mesoderm and endodermal markers.

Gene-expression profile and postpartum transition of bovine endometrial side population cells†

The mechanism of bovine endometrial regeneration after parturition remains unclear. Here, we hypothesized that bovine endometrial stem/progenitor cells participate in the postpartum regeneration of the endometrium. Flow cytometry analysis identified the presence of side population (SP) cells among endometrial stromal cells. Endometrial SP cells were shown to differentiate into osteoblasts and adipocytes. RNA-seq data showed that the gene expression pattern was different between bovine endometrial SP cells and main population cells. Gene Set Enrichment Analysis identified the enrichment of stemness genes in SP cells. Significantly (false discovery rate < 0.01) upregulated genes in SP cells contained several stem cell marker genes. Gene ontology (GO) analysis of the upregulated genes in SP cells showed enrichment of terms related to RNA metabolic process and transcription. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of upregulated genes in SP cells revealed enrichment of signaling pathways associated with maintenance and differentiation of stem/progenitor cells. The terms involved in TCA cycles were enriched in GO and KEGG pathway analysis of downregulated genes in SP cells. These results support the assumption that bovine endometrial SP cells exhibit characteristics of somatic stem/progenitor cells. The ratio of SP cells to endometrial cells was lowest on days 9-11 after parturition, which gradually increased thereafter. SP cells were shown to differentiate into epithelial cells. Collectively, these results suggest that bovine endometrial SP cells were temporarily reduced immediately after calving possibly due to their differentiation to provide new endometrial cells.

FOLFOX Therapy Induces Feedback Upregulation of CD44v6 through YB-1 to Maintain Stemness in Colon Initiating Cells

Cancer initiating cells (CICs) drive tumor formation and drug-resistance, but how they develop drug-resistance characteristics is not well understood. In this study, we demonstrate that chemotherapeutic agent FOLFOX, commonly used for drug-resistant/metastatic colorectal cancer (CRC) treatment, induces overexpression of CD44v6, MDR1, and oncogenic transcription/translation factor Y-box-binding protein-1 (YB-1). Our study revealed that CD44v6, a receptor for hyaluronan, increased the YB-1 expression through PGE2/EP1-mTOR pathway. Deleting CD44v6, and YB-1 by the CRISPR/Cas9 system attenuates the in vitro and in vivo tumor growth of CICs from FOLFOX resistant cells. The results of DNA:CD44v6 immunoprecipitated complexes by ChIP (chromatin-immunoprecipitation) assay showed that CD44v6 maintained the stemness traits by promoting several antiapoptotic and stemness genes, including cyclin-D1,BCL2,FZD1,GINS-1, and MMP9. Further, computer-based analysis of the clones obtained from the DNA:CD44v6 complex revealed the presence of various consensus binding sites for core stemness-associated transcription factors “CTOS” (c-Myc, TWIST1, OCT4, and SOX2). Simultaneous expressions of CD44v6 and CTOS in CD44v6 knockout CICs reverted differentiated CD44v6-knockout CICs into CICs. Finally, this study for the first time describes a positive feedback loop that couples YB-1 induction and CD44 alternative splicing to sustain the MDR1 and CD44v6 expressions, and CD44v6 is required for the reversion of differentiated tumor cells into CICs.

Identification of novel Taz isoforms and functional comparison in pluripotency maintenance of mouse embryonic stem cells

Alternative splicing (AS) is a key process to expand the diversity of mRNA and protein from the genome and it is crucial for fate determination of embryonic stem cells (ESCs) by encoding isoforms with different functions to regulate the balance between pluripotency maintenance and differentiation. Since the role of the Hippo pathway in ESCs is controversial, there may be novel isoforms of Taz, a key effector of the Hippo pathway, previously unknown to us. Here, we identified three variants of Taz in mESCs. Apart from the canonical Taz1185, there were also two novel variants, Taz402 and Taz1086. We found their structure and subcellular localization to be different, while they could all interact with TEAD2 with similar binding affinities and activate transcription. Under the LIF^low condition, overexpression of them all induced apoptosis and differentiation of mESCs, among which the phenotype of Taz1086 was the most dramatic. Taken together, we discovered novel variants of Taz and compared their structure and functional differences in mESC pluripotency maintenance. These findings will help us to understand the Taz gene and clarify its role in mESC.

Stat3 oxidation-dependent regulation of gene expression impacts on developmental processes and involves cooperation with Hif-1α

Reactive oxygen species are bona fide intracellular second messengers that influence cell metabolism and aging by mechanisms that are incompletely resolved. Mitochondria generate superoxide that is dis-mutated to hydrogen peroxide, which in turn oxidises cysteine-based enzymes such as phosphatases, peroxiredoxins and redox-sensitive transcription factors to modulate their activity. Signal Transducer and Activator of Transcription 3 (Stat3) has been shown to participate in an oxidative relay with peroxiredoxin II but the impact of Stat3 oxidation on target gene expression and its biological consequences remain to be established. Thus, we created murine embryonic fibroblasts (MEFs) that express either WT-Stat3 or a redox-insensitive mutant of Stat3 (Stat3-C3S). The Stat3-C3S cells differed from WT-Stat3 cells in morphology, proliferation and resistance to oxidative stress; in response to cytokine stimulation, they displayed elevated Stat3 tyrosine phosphorylation and Socs3 expression, implying that Stat3-C3S is insensitive to oxidative inhibition. Comparative analysis of global gene expression in WT-Stat3 and Stat3-C3S cells revealed differential expression (DE) of genes both under basal conditions and during oxidative stress. Using differential gene regulation pattern analysis, we identified 199 genes clustered into 10 distinct patterns that were selectively responsive to Stat3 oxidation. GO term analysis identified down-regulated genes to be enriched for tissue/organ development and morphogenesis and up-regulated genes to be enriched for cell-cell adhesion, immune responses and transport related processes. Although most DE gene promoters contain consensus Stat3 inducible elements (SIEs), our chromatin immunoprecipitation (ChIP) and ChIP-seq analyses did not detect Stat3 binding at these sites in control or oxidant-stimulated cells, suggesting that oxidised Stat3 regulates these genes indirectly. Our further computational analysis revealed enrichment of hypoxia response elements (HREs) within DE gene promoters, implying a role for Hif-1. Experimental validation revealed that efficient stabilisation of Hif-1α in response to oxidative stress or hypoxia required an oxidation-competent Stat3 and that depletion of Hif-1α suppressed the inducible expression of Kcnb1, a representative DE gene. Our data suggest that Stat3 and Hif-1α cooperate to regulate genes involved in immune functions and developmental processes in response to oxidative stress.

E2A regulates neural ectoderm fate specification in human embryonic stem cells

E protein transcription factors are crucial for many cell fate decisions. However, the roles of E proteins in the germ-layer specification of human embryonic stem cells (hESCs) are poorly understood. We disrupted the TCF3 gene locus to delete the E protein E2A in hESCs. E2A knockout (KO) hESCs retained key features of pluripotency, but displayed decreased neural ectoderm coupled with enhanced mesoendoderm outcomes. Genome-wide analyses showed that E2A directly regulates neural ectoderm and Nodal pathway genes. Accordingly, inhibition of Nodal or E2A overexpression partially rescued the neural ectoderm defect in E2A KO hESCs. Loss of E2A had little impact on the epigenetic landscape of hESCs, whereas E2A KO neural precursors displayed increased accessibility of the gene locus encoding the Nodal agonist CRIPTO. Double-deletion of both E2A and HEB (TCF12) resulted in a more severe neural ectoderm defect. Therefore, this study reveals critical context-dependent functions for E2A in human neural ectoderm fate specification.

STAT3 phosphorylation at Ser727 and Tyr705 differentially regulates the EMT-MET switch and cancer metastasis

Epithelial–mesenchymal transition (EMT)/mesenchymal–epithelial transition (MET) processes are proposed to be a driving force of cancer metastasis. By studying metastasis in bone marrow-derived mesenchymal stem cell (BM-MSC)-driven lung cancer models, microarray time-series data analysis by systems biology approaches revealed BM-MSC-induced signaling triggers early dissemination of CD133⁺/CD83⁺ cancer stem cells (CSCs) from primary sites shortly after STAT3 activation but promotes proliferation towards secondary sites. The switch from migration to proliferation was regulated by BM-MSC-secreted LIF and activated LIFR/p-ERK/pS727-STAT3 signaling to promote early disseminated cancer cells MET and premetastatic niche formation. Then, tumor-tropic BM-MSCs circulated to primary sites and triggered CD151⁺/CD38⁺ cells acquiring EMT-associated CSC properties through IL6R/pY705-STAT3 signaling to promote tumor initiation and were also attracted by and migrated towards the premetastatic niche. In summary, STAT3 phosphorylation at tyrosine 705 and serine 727 differentially regulates the EMT–MET switch within the distinct molecular subtypes of CSCs to complete the metastatic process.

2,3,5,4'-tetrahydroxystilbene-2-O-b-D-glucoside triggers the pluripotent-like possibility of dental pulp stem cells by activating the JAK2/STAT3 axis: Preliminary observations

Abstract

Background/Purpose

Although 2,3,5,4′-Tetrahydroxystilbene-2-O-beta-glucoside (THSG) reportedly has anti-inflammatory properties, its role in inducing the dedifferentiation of human dental pulp stem cells (DPSC) into pluripotent-like stem cells remains to be determined. The purpose of this study is to evaluate the effects of THSG on the pluripotent-like possibility and mechanism of DPSC.

Materials and methods

DPSCs were treated with THSG, and cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTS) assay. Real-time polymerase chain reaction was used to analyze the mRNA expression levels of pluripotency-associated genes and oncogenes and to detect telomerase activity in the cells. Embryoid body formation assay was conducted, and pluripotency-related proteins were identified using Western blotting. Data were analyzed using one-way analysis of variance.

Results

Cell viability, telomerase activity, and embryoid body formation were enhanced in THSG-treated DPSCs. The mRNA expression levels of pluripotent-like genes (including Nanog homeobox [NANOG], SRY-box 2 [SOX2], and POU class 5 homeobox 1 [POU5F1/OCT4]) significantly increased after THSG treatment. The expression levels of pluripotency-related genes (Janus kinase-signal transducer 2 [JAK2] and signal transducer and activator of transcription 3 [STAT3]) increased, whereas those of oncogenes (Ras, SRC, HER2, and C-sis) decreased. Furthermore, the expression levels of the phosphorylated JAK2 and STAT3 proteins significantly increased after THSG treatment.

Conclusion

THSG treatment may enhance the pluripotent-like possibility of DPSC through the JAK2/STAT3 axis. Hence, it may be used as an alternative cell-based therapeutic strategy in regenerative dentistry.

Inhibition of MUC1-C Increases ROS and Cell Death in Mouse Embryonic Stem Cells

Background and Objectives

Embryonic stem (ES) cells have the capacity to self-renew and generate all types of cells. MUC1-C, a cytoplasmic subunit of MUC1, is overexpressed in various carcinomas and mediates signaling pathways to regulate intracellular metabolic processes and gene expression involved in the maintenance of cancer cells. However, the functional role of MUC1-C in ES cells is not well understood. In this study, we investigated the role of MUC1-C on growth, survival, and differentiation of mouse ES (mES) cells.

Methods and Results

Undifferentiated mES cells expressed the MUC1-C protein and the expression level was decreased during differentiation. Inhibition of MUC1-C, by the specific inhibitor GO201, reduced proliferation of mES cells. However, there was no prominent effect on pluripotent markers such as Oct4 expression and STAT3 signaling, and MUC1-C inhibition did not induce differentiation. Inhibition of MUC1-C increased the G1 phase population, decreased the S phase population, and increased cell death. Furthermore, inhibition of MUC1-C induced disruption of the ROS balance in mES cells.

Conclusions

These results suggest that MUC1-C is involved in the growth and survival of mES cells.

Identification of differentially expressed genes in mouse embryonic stem cell under hypoxia

BACKGROUND

Under hypoxia, mouse embryonic stem cells (mESCs) lose the ability to self-renew and begin to differentiate through down-regulation of LIFR-STAT3 pathway via hypoxia-inducible factor-1α (HIF-1α). However, it remains largely unknown what kinds of factors are involved in hypoxia-induced differentiation of mESCs.

PURPOSE

This study aims to identify the differentially expressed genes (DEGs) in early differentiation of mESCs under hypoxia.

METHODS

Here we utilized a Genefishing technique^TM to discover the new DEGs during hypoxia-induced early differentiation in CCE mESCs. Next, we investigated the role of DEGs using morphological observation, alkaline phosphatase (ALP) assay, STAT3 activation analysis, and biomarkers analysis for stemness.

RESULTS

We detected 19 DEGs under hypoxia and performed cloning with sequencing in six genes. We confirmed the expression patterns of five DEGs including H2afz and GOT1 by realtime PCR assay. Among them, H2afz was significantly decreased under hypoxia, depending on HIF-1α. H2afz-overexpressing CCE mESCs maintained their ALP activity and stem cell markers (Nanog and Rex1), even in hypoxic condition. On the other hand, the early differentiation markers such as FGF5 and STAT5a, which had been increased in hypoxic conditions, were reduced by H2afz overexpression.

CONCLUSION

We discovered that H2afz could be a new target gene that functions in hypoxia-induced differentiation in mESCs and have revealed that it is involved in maintaining the pluripotency of mESCs in the early stages of differentiation. These findings will provide insights into mechanisms of hypoxia-mediated differentiation of mESCs during early development.

The epitranscriptome in stem cell biology and neural development

The blossoming field of epitranscriptomics has recently garnered attention across many fields by findings that chemical modifications on RNA have immense biological consequences. Methylation of nucleotides in RNA, including N6-methyladenosine (m⁶A), 2-O-dimethyladenosine (m⁶A_m), N1-methyladenosine (m¹A), 5-methylcytosine (m⁵C), and isomerization of uracil to pseudouridine (Ψ), have the potential to alter RNA processing events and contribute to developmental processes and different diseases. Though the abundance and roles of some RNA modifications remain contentious, the epitranscriptome is thought to be especially relevant in stem cell biology and neurobiology. In particular, m⁶A occurs at the highest levels in the brain and plays major roles in embryonic stem cell differentiation, brain development, and neurodevelopmental disorders. However, studies in these areas have reported conflicting results on epitranscriptomic regulation of stem cell pluripotency and mechanisms in neural development. In this review we provide an overview of the current understanding of several RNA modifications and disentangle the various findings on epitranscriptomic regulation of stem cell biology and neural development.

Genetic Signatures of Evolution of the Pluripotency Gene Regulating Network across Mammals

Mammalian pluripotent stem cells (PSCs) have distinct molecular and biological characteristics among species, but to date we lack a comprehensive understanding of regulatory network evolution in mammals. Here, we carried out a comparative genetic analysis of 134 genes constituting the pluripotency gene regulatory network across 48 mammalian species covering all the major taxonomic groups. We report that mammalian genes in the pluripotency regulatory network show a remarkably high degree of evolutionary stasis, suggesting the conservation of fundamental biological process of mammalian PSCs across species. Nevertheless, despite the overall conservation of the regulatory network, we discovered rapid evolution of the downstream targets of the core regulatory elements and specific amino acid residues that have undergone positive selection. Our data indicate development of lineage-specific pluripotency regulating networks that may explain observed variations in some characteristics of mammalian PSCs. We further revealed that positively selected genes could be associated with species' unique adaptive characteristics that were not dedicated to regulation of PSCs. These results provide important insight into the evolution of the pluripotency gene regulatory network underlying variations in characteristics of mammalian PSCs.

STAT3 modulates reprogramming efficiency of human somatic cells; insights from autosomal dominant Hyper IgE syndrome caused by STAT3 mutations

Human induced pluripotent stem cell (iPSC) technology has opened exciting opportunities for stem-cell-based therapy. However, its wide adoption is precluded by several challenges including low reprogramming efficiency and potential for malignant transformation. Better understanding of the molecular mechanisms of the changes that cells undergo during reprograming is needed to improve iPSCs generation efficiency and to increase confidence for their clinical use safety. Here, we find that dominant negative mutations in STAT3 in patients with autosomal-dominant hyper IgE (Job's) syndrome (AD-HIES) result in greatly reduced reprograming efficiency of primary skin fibroblasts derived from skin biopsies. Analysis of normal skin fibroblasts revealed upregulation and phosphorylation of endogenous signal transducer and activator of transcription 3 (STAT3) and its binding to the NANOG promoter following transduction with OKSM factors. This coincided with upregulation of NANOG and appearance of cells expressing pluripotency markers. Upregulation of NANOG and number of pluripotent cells were greatly reduced throughout the reprograming process of AD-HIES fibroblasts that was restored by over-expression of functional STAT3. NANOGP8, the human-specific NANOG retrogene that is often expressed in human cancers, was also induced during reprogramming, to very low but detectable levels, in a STAT3-dependent manner. Our study revealed the critical role of endogenous STAT3 in facilitating reprogramming of human somatic cells.

Double sperm cloning (DSC) is a promising strategy in mammalian genetic engineering and stem cell research

Embryonic stem cells (ESCs) derived from somatic cell nuclear transfer (SCNT) and induced pluripotent stem cells (iPSCs) are promising tools for meeting the personalized requirements of regenerative medicine. However, some obstacles need to be overcome before clinical trials can be undertaken. First, donor cells vary, and the reprogramming procedures are diverse, so standardization is a great obstacle regarding SCNT and iPSCs. Second, somatic cells derived from a patient may carry mitochondrial DNA mutations and exhibit telomere instability with aging or disease, and SCNT-ESCs and iPSCs retain the epigenetic memory or epigenetic modification errors. Third, reprogramming efficiency has remained low. Therefore, in addition to improving their success rate, other alternatives for producing ESCs should be explored. Producing androgenetic diploid embryos could be an outstanding strategy; androgenic diploid embryos are produced through double sperm cloning (DSC), in which two capacitated sperms (XY or XX, sorted by flow cytometer) are injected into a denucleated oocyte by intracytoplasmic sperm injection (ICSI) to reconstruct embryo and derive DSC-ESCs. This process could avoid some potential issues, such as mitochondrial interference, telomere shortening, and somatic epigenetic memory, all of which accompany somatic donor cells. Oocytes are naturally activated by sperm, which is unlike the artificial activation that occurs in SCNT. The procedure is simple and practical and can be easily standardized. In addition, DSC-ESCs can overcome ethical concerns and resolve immunological response matching with sperm providers. Certainly, some challenges must be faced regarding imprinted genes, epigenetics, X chromosome inactivation, and dosage compensation. In mice, DSC-ESCs have been produced and have shown excellent differentiation ability. Therefore, the many advantages of DSC make the study of this process worthwhile for regenerative medicine and animal breeding.

Novel alternative splicing variants of Klf4 display different capacities for self-renewal and pluripotency in mouse embryonic stem cells

Embryonic stem (ES) cells are unique in their ability to self-renew indefinitely while maintaining pluripotency. Krüppel-like factor (Klf) 4 is an important member of the Klf family that is known to play a key role in pluripotency and somatic cell reprogramming. However, the identification and functional comparison of Klf4 splicing isoforms in mouse ESCs (mESCs) remains to be elucidated. Here, we identified three novel alternative splicing variants of Klf4 in mESCs-mKlf4-108, mKlf4-375 and mKlf4-1482-that are distinct from the previously known mKlf4-1449. mKlf4-1449 and mKlf4-1482 may stimulate the growth of ESCs, while mKlf4-108 can only promote the growth of ESCs in LIF^low/serum conditions. In addition, both mKlf4-1449 and mKlf4-1482 can inhibit the differentiation of mESCs. However, the ability of mKlf4-1482 to promote self-renewal and inhibit differentiation is not as strong as that of mKlf4-1449. In contrast, both mKlf4-108 and mKlf4-375 may have the ability to induce endodermal differentiation. Taken together, we have identified for the first time the existence of alternative splicing variants of mKlf4 and have revealed their different roles, which provide new insights into the contribution of Klf4 to the self-renewal and pluripotency of mouse ESCs.

STAT3, the Challenge for Chemotherapeutic and Radiotherapeutic Efficacy

Chemoradiotherapy is one of the most effective and extensively used strategies for cancer treatment. Signal transducer and activator of transcription 3 (STAT3) regulates vital biological processes, such as cell proliferation and cell growth. It is constitutively activated in various cancers and limits the application of chemoradiotherapy. Accumulating evidence suggests that STAT3 regulates resistance to chemotherapy and radiotherapy and thereby impairs therapeutic efficacy by mediating its feedback loop and several target genes. The alternative splicing product STAT3β is often identified as a dominant-negative regulator, but it enhances sensitivity to chemotherapy and offers a new and challenging approach to reverse therapeutic resistance. We focus here on exploring the role of STAT3 in resistance to receptor tyrosine kinase (RTK) inhibitors and radiotherapy, outlining the potential of targeting STAT3 to overcome chemo(radio)resistance for improving clinical outcomes, and evaluating the importance of STAT3β as a potential therapeutic approach to overcomes chemo(radio)resistance. In this review, we discuss some new insights into the effect of STAT3 and its subtype STAT3β on chemoradiotherapy sensitivity, and we explore how these insights influence clinical treatment and drug development for cancer.

Leptin promotes proliferation of neonatal mouse stem/progenitor spermatogonia

PURPOSE

To keep and increase spermatogonial stem cell number (SSC) is the only available option for pediatric cancer survivors to maintain fertility. Leptin is secreted by the epididymal white adipose tissue and has receptors on stem/progenitor spermatogonia. The purpose of this study is to demonstrate dose- and time-dependent proliferative effect of leptin on stem/progenitor spermatogonia cultures from prepubertal mice testes.

METHODS

CD90.2 (+) stem/progenitor spermatogonia were isolated from the C57BL/6 mouse testis on postnatal day 6 and placed in culture. The proliferative effect of leptin supplementation was assessed by colony formation (diameter and number), WST proliferation assays, and xCELLigence real-time cell analysis (RTCA) on days 3, 5, and 7 of culture. Expressions of p-ERK1/2, p-STAT3, total STAT3, and p-SHP2 levels were determined by western blot analysis.

RESULTS

Leptin supplementation of 100 ng/ml increased the diameter (p = 0.001) and number (p = 0.01) of colonies in stem/progenitor spermatogonial cultures and caused higher proliferation by WST-1 (p = 0.009) compared with the control on day 7. The EC50 was calculated as 114 ng/ml for leptin by RTCA. Proliferative dose of leptin induced increased expression of p-ERK1/2 (p = 0.009) and p-STAT3 (p = 0.023) on stem/progenitor spermatogonia when compared with the untreated group.

CONCLUSION

The results indicated that leptin supplementation exhibited a dose- and time-dependent proliferative effect on stem/progenitor spermatogonia that was associated with increased expression of ERK1/2 and STAT3 pathways while maintaining their undifferentiated state. This output presents a new agent that may help to expand the stem/progenitor spermatogonia pool from the neonatal testis in order to autotransplant after cancer treatment.

Heat Shock Proteins and their Protective Roles in Stem Cell Biology

Stem cells (SCs) are discovered long back but the idea that SCs possess therapeutic potential came up just a few decades back. In a past decade stem cell therapy is highly emerged and displayed tremendous potential for the treatment of a wide range of diseases and disorders such as blindness and vision impairment, type I diabetes, infertility, HIV, etc. SCs are very susceptible to destruction after transplantation into the host because of the inability to sustain elevated stress conditions inside the damaged tissue/organ. Heat shock proteins (HSPs) are molecular chaperones/stress proteins expressed in response to stress (elevated temperature, harmful chemicals, ischemia, viruses, etc) inside a living cell. HSPs protect the cell from damage by assisting in the proper folding of cellular proteins. This review briefly summarises different types of HSPs, their classification, cellular functions as well as the role of HSPs in regulating SC self-renewal and survival in the transplanted host. Applications of HSP modulated SCs in regenerative medicine and for the treatment of ischemic heart disease, myocardial infarction (MI), osteoarthritis, ischemic stroke, spinocerebellar ataxia type 3 (SCA3), leukemia, hepatic ischemia-reperfusion injury, Graft-versus-host disease (GVHD) and Parkinson's disease (PD) are discussed. In order to provide potential insights in understanding molecular mechanisms related to SCs in vertebrates, correlations between HSPs and SCs in cnidarians and planarians are also reviewed. There is a need to advance research in order to validate the use of HSPs for SC therapy and establish effective treatment strategies.

Endothelial-Initiated Crosstalk Regulates Dental Pulp Stem Cell Self-Renewal

Interactions with the microenvironment modulate the fate of stem cells in perivascular niches in tissues (e.g., bone) and organs (e.g., liver). However, the functional relevance of the molecular crosstalk between endothelial cells and stem cells within the perivascular niche in dental pulps is unclear. Here, we tested the hypothesis that endothelial cell-initiated signaling is necessary to maintain self-renewal of dental pulp stem cells. Confocal microscopy showed that ALDH1high and Bmi-1high stem cells are preferentially localized in close proximity to blood vessels in physiological human dental pulps. Secondary orosphere assays revealed that endothelial cell-derived factors (e.g., interleukin-6 [IL-6]) promote self-renewal of dental pulp stem cells cultured in low-attachment conditions. Mechanistic studies demonstrated that endothelial cell-derived IL-6 activates IL-6R (IL-6 Receptor) and signal transducer and activator of transcription 3 (STAT3) signaling and induces expression of Bmi-1 (master regulator of stem cell self-renewal) in dental pulp stem cells. Transplantation of dental pulp stem cells stably transduced with small hairpin RNA (shRNA)-STAT3 into immunodeficient mice revealed a decrease in the number of blood vessels surrounded by ALDH1high or Bmi-1high cells (perivascular niches) compared to tissues formed upon transplantation of vector control stem cells. And finally, in vitro capillary sprouting assays revealed that inhibition of IL-6 or STAT3 signaling decreases the vasculogenic potential of dental pulp stem cells. Collectively, these data demonstrate that endothelial cell-derived IL-6 enhances the self-renewal of dental pulp stem cells via STAT3 signaling and induction of Bmi-1. These data suggest that a crosstalk between endothelial cells and stem cells within the perivascular niche is required for the maintenance of stem cell pools in dental pulps.

A novel GSK3 inhibitor that promotes self-renewal in mouse embryonic stem cells

Small molecules that regulate cell stemness have the potential to make a major contribution to regenerative medicine. In the course of screening for small molecules that affect stemness in mouse embryonic stem cells (mESCs), we discovered that NPD13432, an aurone derivative, promoted self-renewal of mESCs. Normally, mESCs start to differentiate upon withdrawal of 2i/LIF. However, cells treated with the compound continued to express endogenous Nanog, a pluripotency marker protein essential for sustaining the undifferentiated state, even in the absence of 2i/LIF. Biochemical characterization revealed that NPD13432 inhibited GSK3α and GSK3β with IC₅₀ values of 92 nM and 310 nM, respectively, suggesting that the compound promotes self-renewal in mESCs by inhibiting GSK3. The chemical structure of the compound is unique among known molecules with this activity, providing an opportunity to develop new inhibitors of GSK3, as well as chemical tools for investigating cell stemness.

Trophoblast lineage specification in the mammalian preimplantation embryo

BACKGROUND

The establishment of the trophectoderm (TE) and the inner cell mass (ICM) is the first cell lineage segregation that occurs in mammalian preimplantation development. TE will contribute to the placenta while ICM cells give rise to the epiblast (EPI) and primitive endoderm (PrE). There are two historical models for TE/ICM segregation: the positional (inside-outside) model and the polarity model, but both models alone cannot explain the mechanism of TE/ICM segregation.

METHODS

This article discusses a current possible model based on recent studies including the finding through live-cell imaging of the expression patterns of caudal type homeobox 2 (Cdx2), a key transcription factor of TE differentiation in the mouse embryo.

RESULTS

It was observed that a part of outer Cdx2-expressing blastomeres was internalized at the around 20- to 30-cell stage, downregulates Cdx2, ceases TE differentiation, and participates in ICM lineages.

CONCLUSION

The early blastomere, which starts differentiation toward the TE cell fate, still has plasticity and can change its fate. Differentiation potency of all blastomeres until approximately the 32-cell stage is presumably not irreversibly restricted even if they show heterogeneity in their epigenetic modifications or gene expression patterns.

Prevention of tumor risk associated with the reprogramming of human pluripotent stem cells

Human pluripotent embryonic stem cells have two special features: self-renewal and pluripotency. It is important to understand the properties of pluripotent stem cells and reprogrammed stem cells. One of the major problems is the risk of reprogrammed stem cells developing into tumors. To understand the process of differentiation through which stem cells develop into cancer cells, investigators have attempted to identify the key factors that generate tumors in humans. The most effective method for the prevention of tumorigenesis is the exclusion of cancer cells during cell reprogramming. The risk of cancer formation is dependent on mutations of oncogenes and tumor suppressor genes during the conversion of stem cells to cancer cells and on the environmental effects of pluripotent stem cells. Dissecting the processes of epigenetic regulation and chromatin regulation may be helpful for achieving correct cell reprogramming without inducing tumor formation and for developing new drugs for cancer treatment. This review focuses on the risk of tumor formation by human pluripotent stem cells, and on the possible treatment options if it occurs. Potential new techniques that target epigenetic processes and chromatin regulation provide opportunities for human cancer modeling and clinical applications of regenerative medicine.

Combined Targeting of Glioblastoma Stem-Like Cells by Neutralizing RNA-Bio-Drugs for STAT3

An important drawback in the management of glioblastoma (GBM) patients is the frequent relapse upon surgery and therapy. A likely explanation is that conventional therapies poorly affect a small population of stem-like cancer cells (glioblastoma stem cells, GSCs) that remain capable of repopulating the tumour mass. Indeed, the development of therapeutic strategies able to hit GSCs while reducing the tumour burden has become an important challenge to increase a patient’s survival. The signal transducer and activator of transcription-3 (STAT3) has been reported to play a pivotal role in maintaining the tumour initiating capacity of the GSC population. Therefore, in order to impair the renewal and propagation of the PDGFRβ-expressing GSC population, here we took advantage of the aptamer–siRNA chimera (AsiC), named Gint4.T-STAT3, that we previously have shown to efficiently antagonize STAT3 in subcutaneous PDGFRβ-positive GBM xenografts. We demonstrate that the aptamer conjugate is able to effectively and specifically prevent patient-derived GSC function and expansion. Moreover, because of the therapeutic potential of using miR-10b inhibitors and of the broad expression of the Axl receptor in GBM, we used the GL21.T anti-Axl aptamer as the targeting moiety for anti-miR-10b, showing that, in combination with the STAT3 AsiC, the aptamer–miR-10b antagonist treatment further enhances the inhibition of GSC sphere formation. Our results highlight the potential to use a combined approach with targeted RNA therapeutics to inhibit GBM tumour dissemination and relapse.

A function of fascin1 in the colony formation of mouse embryonic stem cells

Fascin1 is known to participate in the migration of cancer cells by binding to actin filaments. Recent studies evidenced that fascin1 also modulates processes such as the tumorigenesis and maintenance of pluripotency genes in cancer stem cells. However, the function of fascin1 in embryonic stem cells remains unclear. In this article, we report that fascin1 is highly expressed and widely distributed in mouse embryonic stem cells (mESCs), which are regulated by JAK-STAT3 and β-catenin. We found that the overexpression of fascin1 impairs the formation of mESC colonies via the downregulation of intercellular adhesion molecules, and that mimicking the dephosphorylated mutation of fascin1 or inhibiting phosphorylation with Gö6983 significantly enhances colony formation. Hyperphosphorylated fascin1 can promote the maintenance of pluripotency in mESCs via nuclear localization and suppressing DNA methyltransferase expression. Our findings demonstrate a novel function of fascin1, as a vital regulator, in the colony formation and pluripotency of mESCs and provide insights into the molecular mechanisms underlying embryonic stem cell self-organization and development in vitro.

Pleiotropic roles of tankyrase/PARP proteins in the establishment and maintenance of human naïve pluripotency

Tankyrase 1 (TNKS1; PARP-5a) and Tankyrase 2 (TNKS2; PARP-5b) are poly-ADP-ribosyl-polymerase (PARP)-domain-containing proteins that regulate the activities of a wide repertoire of target proteins via post-translational addition of poly-ADP-ribose polymers (PARylation). Although tankyrases were first identified as regulators of human telomere elongation, important and expansive roles of tankyrase activity have recently emerged in the development and maintenance of stem cell states. Herein, we summarize the current state of knowledge of the various tankyrase-mediated activities that may promote human naïve and 'extended' pluripotency'. We review the putative role of tankyrase and PARP inhibition in trophectoderm specification, telomere elongation, DNA repair and chromosomal segregation, metabolism, and PTEN-mediated apoptosis. Importantly, tankyrases possess PARP-independent activities that include regulation of MDC1-associated DNA repair by homologous recombination (HR) and autophagy/pexophagy, which is an essential mechanism of protein synthesis in the preimplantation embryo. Additionally, tankyrases auto-regulate themselves via auto-PARylation which augments their cellular protein levels and potentiates their non-PARP tankyrase functions. We propose that these non-PARP-related activities of tankyrase proteins may further independently affect both naïve and extended pluripotency via mechanisms that remain undetermined. We broadly outline a hypothetical framework for how inclusion of a tankyrase/PARP inhibitor in small molecule cocktails may stabilize and potentiate naïve and extended pluripotency via pleiotropic routes and mechanisms.

STAT3 for Cardiac Regenerative Medicine: Involvement in Stem Cell Biology, Pathophysiology, and Bioengineering

Heart disease is the most common cause of death in developed countries, but the medical treatments for heart failure remain limited. In this context, the development of cardiac regeneration therapy for severe heart failure is important. Owing to their unique characteristics, including multiple differentiation and infinitive self-renewal, pluripotent stem cells can be considered as a novel source for regenerative medicine. Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling plays critical roles in the induction, maintenance, and differentiation of pluripotent stem cells. In the heart, JAK/STAT3 signaling has diverse cellular functions, including myocardial differentiation, cell cycle re-entry of matured myocyte after injury, and anti-apoptosis in pathological conditions. Therefore, regulating STAT3 activity has great potential as a strategy of cardiac regeneration therapy. In this review, we summarize the current understanding of STAT3, focusing on stem cell biology and pathophysiology, as they contribute to cardiac regeneration therapy. We also introduce a recently reported therapeutic strategy for myocardial regeneration that uses engineered artificial receptors that trigger endogenous STAT3 signal activation.

Inhibition of MAGEA2 regulates pluripotency, proliferation, apoptosis, and differentiation in mouse embryonic stem cells

Mouse embryonic stem cells (mESCs) exhibit self-renewal and pluripotency, can differentiate into all three germ layers, and serve as an essential model in stem cell research and for potential clinical application in regenerative medicine. Melanoma-associated antigen A2 (MAGEA2) is not expressed in normal somatic cells but rather in different types of cancer, especially in undifferentiated cells, such as in the testis, differentiating cells, and ESCs. However, the role of MAGEA2 in mESCs remains to be clarified. Accordingly, in this study, we examined the expression and functions of MAGEA2 in mESCs. MAGEA2 messenger RNA (mRNA) expression was decreased during mESCs differentiation. MAGEA2 function was then evaluated in knockdown mESC. MAGEA2 knockdown resulted in decreased pluripotency marker gene expression in mESCs consequent to increased Erk1/2 phosphorylation. Decreased MAGEA2 expression inhibited mESC proliferation via S phase cell cycle arrest with a subsequent decrease in cell cycle-associated genes Cdk1, Cdk2, Cyclin A1, Cyclin D1, and Cdc25a. Apoptotic mESCs markedly increased along with cleaved forms of caspases 3, 6, and 7 and PARP expression, confirming caspase-dependent apoptosis. MAGEA2 knockdown significantly decreased embryoid body size in vitro when cells were differentiated naturally and teratoma size in vivo, concomitant with decreased ectoderm marker gene expression. These findings suggested that MAGEA2 regulates ESC pluripotency, proliferation, cell cycle, apoptosis, and differentiation. The enhanced understanding of the regulatory mechanisms underlying diverse mESC characteristics will facilitate the clinical application of mESCs.

Landscape inferred from gene expression data governs pluripotency in embryonic stem cells

Embryonic stem cells (ESCs) can differentiate into diverse cell types and have the ability of self-renewal. Therefore, the study of cell fate decisions on embryonic stem cells has far-reaching significance for regenerative medicine and other biomedical fields. Mathematical models have been used to study emryonic stem cell differentiation. However, the underlying mechanisms of cell differentiation and lineage reprogramming remain to be elucidated. Especially, how to integrate the computational models with quantitative experimental data is still challenging. In this work, we developed a data-constrained modelling approach, and established a model of mouse embryonic stem cells. We used the truncated moment equations (TME) method to quantify the potential landscape of the ESC network. We identified two attractors on the landscape, which represent the embryonic stem cell (ESC) state and differentiated cell (DC) state, respectively, and quantified high dimensional biological paths for differentiation and reprogramming process. Through identifying the optimal combinations of gene targets based on a landscape control strategy, we offered some predictions about the key regulatory factors that govern the differentiation and reprogramming in ESCs.

The novel application of cordycepin in maintaining stem cell pluripotency and increasing iPS cell generation efficiency

Maintaining the pluripotency of either embryonic stem (ES) cells or induced pluripotent stem (iPS) cells is a fundamental part of stem cell research. In this study, we reported that cordycepin promoted the expression of pluripotency markers in ES and iPS cells. ES cells treated with cordycepin demonstrated their potential for generating embryoid bodies and differentiating into all three germ layers. The expression levels of phospho-Jak2, phospho-Stat3, integrin αV, and integrin β5 were increased after cordycepin treatment. Furthermore, the protein expression levels of IL-6 family proteins (IL-6, IL-11, LIF, oncostatin M (OSM), ciliary neurotrophic factor (CNTF)), and epidermal growth factor (EGF) were also upregulated after cordycepin treatment, but were restored after co-treatment with a Jak2 inhibitor (AG490). The gene expression levels of Yamanaka factors were upregulated in mouse embryonic fibroblasts (MEFs) after cordycepin treatment. Moreover, the generation efficiencies of iPS cells were elevated after cordycepin treatment. We found that iPS cells generated after cordycepin treatment, not only expressed pluripotency markers, but also showed the ability of differentiating into neuron stem/progenitor cells. Taken together, we demonstrated that cordycepin maintained the pluripotency of stem cells via regulation of extracellular matrix (ECM) and Jak2/Stat3 signaling pathway and improved the generation efficiency of iPSCs.

Advances in Pluripotent Stem Cells: History, Mechanisms, Technologies, and Applications

Over the past 20 years, and particularly in the last decade, significant developmental milestones have driven basic, translational, and clinical advances in the field of stem cell and regenerative medicine. In this article, we provide a systemic overview of the major recent discoveries in this exciting and rapidly developing field. We begin by discussing experimental advances in the generation and differentiation of pluripotent stem cells (PSCs), next moving to the maintenance of stem cells in different culture types, and finishing with a discussion of three-dimensional (3D) cell technology and future stem cell applications. Specifically, we highlight the following crucial domains: 1) sources of pluripotent cells; 2) next-generation in vivo direct reprogramming technology; 3) cell types derived from PSCs and the influence of genetic memory; 4) induction of pluripotency with genomic modifications; 5) construction of vectors with reprogramming factor combinations; 6) enhancing pluripotency with small molecules and genetic signaling pathways; 7) induction of cell reprogramming by RNA signaling; 8) induction and enhancement of pluripotency with chemicals; 9) maintenance of pluripotency and genomic stability in induced pluripotent stem cells (iPSCs); 10) feeder-free and xenon-free culture environments; 11) biomaterial applications in stem cell biology; 12) three-dimensional (3D) cell technology; 13) 3D bioprinting; 14) downstream stem cell applications; and 15) current ethical issues in stem cell and regenerative medicine. This review, encompassing the fundamental concepts of regenerative medicine, is intended to provide a comprehensive portrait of important progress in stem cell research and development. Innovative technologies and real-world applications are emphasized for readers interested in the exciting, promising, and challenging field of stem cells and those seeking guidance in planning future research direction.

GP130 Cytokines in Breast Cancer and Bone

Breast cancer cells have a high predilection for skeletal homing, where they may either induce osteolytic bone destruction or enter a latency period in which they remain quiescent. Breast cancer cells produce and encounter autocrine and paracrine cytokine signals in the bone microenvironment, which can influence their behavior in multiple ways. For example, these signals can promote the survival and dormancy of bone-disseminated cancer cells or stimulate proliferation. The interleukin-6 (IL-6) cytokine family, defined by its use of the glycoprotein 130 (gp130) co-receptor, includes interleukin-11 (IL-11), leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF), and cardiotrophin-1 (CT-1), among others. These cytokines are known to have overlapping pleiotropic functions in different cell types and are important for cross-talk between bone-resident cells. IL-6 cytokines have also been implicated in the progression and metastasis of breast, prostate, lung, and cervical cancer, highlighting the importance of these cytokines in the tumor–bone microenvironment. This review will describe the role of these cytokines in skeletal remodeling and cancer progression both within and outside of the bone microenvironment.

β-catenin stimulates Tcf7l1 degradation through recruitment of casein kinase 2 in mouse embryonic stem cells

Activation of the Wnt/β-catenin signaling pathway by the inhibition of glycogen synthase kinase-3 (GSK-3) will induce Tcf7l1 protein degradation to effectively promote embryonic stem cell (ESC) self-renewal. However, the exact mechanism remains unclear. Here, we found that inhibition of casein kinase 2 (Csnk2) by TBB or DMAT was sufficient to block the reduction of the Tcf7l1 protein induced by CHIR99021, a specific inhibitor of GSK-3. Similarly, downregulation of Csnk2 increased the Tcf7l1 level. In contrast, overexpression of Csnk2 significantly decreased Tcf7l1 protein stability in mouse ESCs. Notably, Csnk2α1 controls Tcf7l1 turnover to a greater degree than the other two isoforms of Csnk2, Csnk2α2 and Csnk2β, as Csnk2α1-overexpressing mouse ESCs exhibited the lowest level of Tcf7l1. Csnk2α1 interacted with and phosphorylated Tcf7l1. In addition, the association of Csnk2α1 and Tcf7l1 was enhanced by CHIR99021. Our study demonstrated, for the first time, that Csnk2 is involved in Tcf7l1 turnover mediated by the Wnt/β-catenin signaling pathway. These results expand our understanding of the function and circuit of Wnt/β-catenin signaling pathway in ESCs.

Defined Stem Cell Culture Conditions to Model Mouse Blastocyst Development

The complex program of mouse development entails specification of the embryonic epiblast (Epi) as well as the extra-embryonic trophectoderm (TE) and primitive endoderm (PrE). These three lineages of mouse blastocyst can be modeled in vitro using stem cells derived from primary tissues. In these cultures, cells self-renew while retaining their developmental potential if put back into a developing embryo. Indeed, embryonic stem cells (ESC), when injected into a blastocyst, readily contribute to all embryonic lineages. Similarly, trophoblast stem cells (TSCs) will give rise to all TE-derived trophoblast lineages, and extraembryonic endoderm cells (XEN) will contribute to the PrE-derived yolk sack. These model systems are a powerful tool to study early development, lineage specification, and placenta formation. Only recently reproducible and chemically defined culture systems of these cells have been described. This overview discusses such novel methods for culturing ESC/TSC/XEN, as well as their molecular signatures and developmental potential. Recent strides in expanding the developmental potential of stem cells as well as achieving models more reminiscent of their in vivo counterparts are discussed. Finally, such in vitro stem cells can self-assemble into structures resembling embryos when used in novel 3D-culture systems. This article discusses the strengths and limitations of such "synthetic embryos" in studying developmental processes. © 2020 by John Wiley & Sons, Inc.

SSEA3 and Sialyl Lewis a Glycan Expression Is Controlled by B3GALT5 LTR through Lamin A-NFYA and SIRT1-STAT3 Signaling in Human ES Cells

B3GALT5 is involved in the synthesis of embryonic stem (ES) cell marker glycan, stage-specific embryonic antigen-3 (SSEA3). This gene has three native promoters and an integrated retroviral long terminal repeat (LTR) promoter. We found that B3GALT5-LTR is expressed at high levels in human ES cells. B3GALT5-LTR is also involved in the synthesis of the cancer-associated glycan, sialyl Lewis a. Sialyl Lewis a is expressed in ES cells and its expression decreases upon differentiation. Retinoic acid induced differentiation of ES cells, decreased the short form of NFYA (NFYAs), increased phosphorylation of STAT3, and decreased B3GALT5-LTR expression. NFYAs activated, and constitutively-active STAT3 (STAT3C) repressed B3GALT5-LTR promoter. The NFYAs and STAT3C effects were eliminated when their binding sites were deleted. Retinoic acid decreased the binding of NFYA to B3GALT5-LTR promoter and increased phospho-STAT3 binding. Lamin A repressed NFYAs and SSEA3 expression. SSEA3 repression mediated by a SIRT1 inhibitor was reversed by a STAT3 inhibitor. Repression of SSEA3 and sialyl Lewis a synthesis mediated by retinoic acid was partially reversed by lamin A short interfering RNA (siRNA) and a STAT3 inhibitor. In conclusion, B3GALT5-LTR is regulated by lamin A-NFYA and SIRT1-STAT3 signaling that regulates SSEA3 and sialyl Lewis a synthesis in ES cells, and sialyl Lewis a is also a ES cell marker.

STAT Signaling in Glioma Cells

STAT (signal transducers and activators of transcription) are latent cytoplasmic transcription factors that function as downstream effectors of cytokine and growth factor receptor signaling. The canonical JAK/STAT signaling pathway involves the activation of Janus kinases (JAK) or growth factors receptor kinases, phosphorylation of STAT proteins, their dimerization and translocation into the nucleus where STATs act as transcription factors with pleiotropic downstream effects. STAT signaling is tightly controlled with restricted kinetics due to action of its negative regulators. While STAT1 is believed to play an important role in growth arrest and apoptosis, and to act as a tumor suppressor, STAT3 and 5 are involved in promoting cell cycle progression, cellular transformation, and preventing apoptosis. Aberrant activation of STATs, in particular STAT3 and STAT5, have been found in a large number of human tumors, including gliomas and may contribute to oncogenesis. In this chapter, we have (1) summarized the mechanisms of STAT activation in normal and malignant signaling; (2) discussed evidence for the critical role of constitutively activated STAT3 and STAT5 in glioma pathobiology; (3) disclosed molecular and pharmacological strategies to interfere with STAT signaling for potential therapeutic intervention in gliomas.

Rbm14 maintains the integrity of genomic DNA during early mouse embryogenesis via mediating alternative splicing

OBJECTIVE

In this study, we generated an Rbm14 knockout mouse model to explore its functions during early mouse embryogenesis.

MATERIALS AND METHODS

The Rbm14 knockout mouse model was generated by a combination of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 and microinjection techniques. The developmental defects of the knockout embryos were characterized by histological analyses. The accumulation of DNA damage in mouse embryonic stem cells (ESCs) was detected by γH2AX staining and comet assay. The altered mRNA splicing of DNA damage response (DDR)-related genes was detected by RNA-Seq analysis and confirmed by semi-quantitative PCR. The interaction of RBM14 with alternative splicing-related genes was detected by immunoprecipitation-mass spectra (IP-MS) and confirmed by co-immunoprecipitation (Co-IP).

RESULTS

Rbm14 knockout in mice results in apoptosis and cell proliferation defects in early post-implantation epiblast cells, leading to gastrulation disruption and embryonic lethality. FACS and immunostaining demonstrate accumulation of DNA damage in Rbm14 knockout ES cells. We also identified altered splicing of DDR-related genes in the knockout mouse ESCs by RNA-Seq, indicating that RBM14-mediated alternative splicing is required for the maintenance of genome integrity during early mouse embryogenesis.

CONCLUSIONS

Our work reveals that Rbm14 plays an essential role in the maintenance of genome integrity during early mouse embryonic development by regulating alternative splicing of DDR-related genes.

Linc1557 is critical for the initiation of embryonic stem cell differentiation by directly targeting the LIF/STAT3 signaling pathway

Embryonic stem cells (ESCs) have self-renewal and multi-lineage differentiation potential and perform critical functions in development and biomedicine. Several long noncoding RNAs (lncRNAs) have been reported as key regulators of stem cell pluripotency and differentiation. However, the function and regulatory mechanism of lncRNAs during the initiation of ESC differentiation remains unclear. Here, we found that linc1557 was highly expressed in mouse ESCs and required for the initiation of ESC differentiation. Knockdown of linc1557 increased the expression and phosphorylation levels of signal transducer and activator of transcription 3 (STAT3), a key factor in the leukemia inhibitory factor (LIF)/STAT3 signaling pathway. Furthermore, we found that linc1557 directly bound to Stat3 mRNA and affected its stability. The differentially expressed transcriptome after linc1557 knockdown in ESCs was involved primarily in multicellular organism development and cell differentiation as similar to that after Stat3 knockdown. Moreover, either knockdown of Stat3 or addition of a LIF/STAT3 signaling inhibitor rescued the suppressive effects of linc1557 knockdown on the initiation of mouse ESC differentiation. These findings not only elucidated the critical function of linc1557 in the initiation of mouse ESC differentiation but also clarified that its specific mechanism as directly affecting Stat3 mRNA stability, which enhanced the understanding of the lncRNA-mediated regulatory mechanism for mRNA stability and key signaling pathways in ESC pluripotency and differentiation.

Modification of stem cell states by alcohol and acetaldehyde

Ethanol (EtOH) is a recreationally ingested compound that is both teratogenic and carcinogenic in humans. Because of its abundant consumption worldwide and the vital role of stem cells in the formation of birth defects and cancers, delineating the effects of EtOH on stem cell function is currently an active and urgent pursuit of scientific investigation to explicate some of the mechanisms contributing to EtOH toxicity. Stem cells represent a primordial, undifferentiated phase of development; thus encroachment on normal physiologic processes of differentiation into terminal lineages by EtOH can greatly alter the function of progenitors and terminally differentiated cells, leading to pathological consequences that manifest as fetal alcohol spectrum disorders and cancers. In this review we explore the disruptive role of EtOH in differentiation of stem cells. Our primary objective is to elucidate the mechanisms by which EtOH alters differentiation-related gene expression and lineage specifications, thus modifying stem cells to promote pathological outcomes. We additionally review the effects of a reactive metabolite of EtOH, acetaldehyde (AcH), in causing both differentiation defects in stem cells as well as genomic damage that incites cellular aging and carcinogenesis.

TGFβ Family Signaling Pathways in Pluripotent and Teratocarcinoma Stem Cells' Fate Decisions: Balancing Between Self-Renewal, Differentiation, and Cancer

The transforming growth factor-β (TGFβ) family factors induce pleiotropic effects and are involved in the regulation of most normal and pathological cellular processes. The activity of different branches of the TGFβ family signaling pathways and their interplay with other signaling pathways govern the fine regulation of the self-renewal, differentiation onset and specialization of pluripotent stem cells in various cell derivatives. TGFβ family signaling pathways play a pivotal role in balancing basic cellular processes in pluripotent stem cells and their derivatives, although disturbances in their genome integrity induce the rearrangements of signaling pathways and lead to functional impairments and malignant transformation into cancer stem cells. Therefore, the identification of critical nodes and targets in the regulatory cascades of TGFβ family factors and other signaling pathways, and analysis of the rearrangements of the signal regulatory network during stem cell state transitions and interconversions, are key issues for understanding the fundamental mechanisms of both stem cell biology and cancer initiation and progression, as well as for clinical applications. This review summarizes recent advances in our understanding of TGFβ family functions in naїve and primed pluripotent stem cells and discusses how these pathways are involved in perturbations in the signaling network of malignant teratocarcinoma stem cells with impaired differentiation potential.

Characterization of Adult Canine Kidney Epithelial Stem Cells That Give Rise to Dome-Forming Tubular Cells

Dome formation can occur in cultured tubular epithelial cells originating from various tissues, including the mammary gland and the kidney. The isolation and characterization of normal kidney epithelial stem cells that give rise to dome-forming tubular cells have never been reported. We attempted to isolate and characterize canine kidney epithelial stem cells using a simple cell culture method that we have previously used to isolate other adult human stem cells. Dome-forming kidney epithelial cells were derived from dissociated adult canine kidney tissues that were cultured in a modified keratinocyte serum-free medium supplemented with N-acetyl-l-cysteine, l-ascorbic acid 2-phosphate, nicotinamide, and fetal bovine serum. These cells exhibited high self-renewal capacity in long-term culture (growth for >13 months and 30 cumulative population doublings) and exhibited characteristics of stem cells, including (1) deficiency in gap junctional intercellular communication, (2) anchorage-independent growth, (3) expression of stem cell markers octamer-binding transcription factor 4 and SRY (sex determining region Y)-box 2, (4) expression of cell surface markers CD24 and CD133, and (5) multipotent differentiation into osteoblasts, adipocytes, chondrocytes, and dome-forming tubular cells. Most of these characteristics are shared by the well-known canine renal tubule-derived immortalized Madin-Darby Canine Kidney cell line. Furthermore, the putative canine kidney stem cells developed in this study formed budding tubule-like organoids on Matrigel and required high cell density (>4,000 cells/cm²) for sustained growth and confluency for dome formation. The signal transducer and activator of transcription-3 (STAT3) phosphorylation inhibitor, AG490, inhibited colony-forming efficiency and dome formation, whereas lipopolysaccharide, an activator of STAT3, increased colony-forming efficiency in a dose-dependent manner. These results are consistent with the hypothesis that high cell density induces STAT3 expression, which promotes both stem cell self-renewal and differentiation into tubular cells. Our novel cell culture method should be useful for the future development of normal human kidney stem cells for clinical applications and for studying mechanisms of nephrotoxicity.

Zinc Maintains Embryonic Stem Cell Pluripotency and Multilineage Differentiation Potential via AKT Activation

Embryonic stem cells (ESCs) possess remarkable abilities, as they can differentiate into all cell types (pluripotency) and be self-renewing, giving rise to two identical cells. These characteristics make ESCs a powerful research tool in fundamental embryogenesis as well as candidates for use in regenerative medicine. Significant efforts have been devoted to developing protocols to control ESC fate, including soluble and complex cocktails of growth factors and small molecules seeking to activate/inhibit key signaling pathways for the maintenance of pluripotency states or activate differentiation. Here we describe a novel method for the effective maintenance of mouse ESCs, avoiding the supplementation of complex inhibitory cocktails or cytokines, e.g., LIF. We show that the addition of zinc to ESC cultures leads to a stable pluripotent state that shares biochemical, transcriptional and karyotypic features with the classical LIF treatment. We demonstrate for the first time that ESCs maintained in long-term cultures with added zinc, are capable of sustaining a stable ESCs pluripotent phenotype, as well as differentiating efficiently upon external stimulation. We show that zinc promotes long-term ESC self-renewal (>30 days) via activation of ZIP7 and AKT signaling pathways. Furthermore, the combination of zinc with LIF results in a synergistic effect that enhances LIF effects, increases AKT and STAT3 activity, promotes the expression of pluripotency regulators and avoids the expression of differentiation markers.