Wnt/β-catenin signaling promotes differentiation, not self-renewal, of human embryonic stem cells and is repressed by Oct4. Proc Natl Acad Sci U S A. 2012;109:4485-4490. [PMID: 22392999 DOI: 10.1073/pnas.1118777109]

β-catenin mediates endodermal commitment of human ES cells via distinct transactivation functions

BACKGROUND

β-catenin, acting as the core effector of canonical Wnt signaling pathway, plays a pivotal role in controlling lineage commitment and the formation of definitive endoderm (DE) during early embryonic development. Despite extensive studies using various animal and cell models, the β-catenin-centered regulatory mechanisms underlying DE formation remain incompletely understood, partly due to the rapid and complex cell fate transitions during early differentiation.

RESULTS

In this study, we generated new CTNNB1-/- human ES cells (hESCs) using CRISPR-based insertional gene disruption approach and systematically rescued the DE defect in these cells by introducing various truncated or mutant forms of β-catenin. Our analysis showed that a truncated β-catenin lacking both N- and C-terminal domains (ΔN148C) could robustly rescue the DE formation, whereas hyperactive β-catenin mutants with S33Y mutation or N-terminal deletion (ΔN90) had limited ability to induce DE lineage. Notably, the ΔN148C mutant exhibited significant nuclear translocation that was positively correlated with successful DE rescue. Transcriptomic analysis further uncovered that two weak β-catenin mutants lacking the C-terminal transactivation domain (CTD) activated primitive streak (PS) genes, whereas the hyperactive β-catenin mutants activated mesoderm genes.

CONCLUSION

Our study uncovered an unconventional regulatory function of β-catenin through weak transactivation, indicating that the levels of β-catenin activity determine the lineage bifurcation from mesendoderm into endoderm and mesoderm.

Dynamic Transcriptome Analysis of SFRP Family in Guided Bone Regeneration With Occlusive Periosteum in Swine Model

BACKGROUND

A variety of congenital or acquired conditions can cause craniomaxillofacial bone defects, resulting in a heavy financial burden and psychological stress. Guided bone self-generation with periosteum-preserved has great potential for reconstructing large bone defects.

METHODS

A swine model of guided bone regeneration with occlusive periosteum was established, the rib segment was removed, and the periosteum was sutured to form a closed regeneration chamber. Hematoxylin and eosin staining, Masson's staining, and Safranine O-Fast Green staining were done. Nine-time points were chosen for collecting the periosteum and regenerated bone tissue for gene sequencing. The expression level of each secreted frizzled-related protein (SFRP) member and the correlations among them were analyzed.

RESULTS

The process of bone regeneration is almost complete 1 month after surgery, and up to 1 week after surgery is an important interval for initiating the process. The expression of each SFRP family member fluctuated greatly. The highest expression level of all members ranged from 3 days to 3 months after surgery. The expression level of SFRP2 was the highest, and the difference between 2 groups was the largest. Secreted frizzled-related protein 2 and SFRP4 showed a notable positive correlation between the control and model groups. Secreted frizzled-related protein 1, SFRP2, and SFRP4 had a significant spike in fold change at 1 month postoperatively. Secreted frizzled-related protein 1 and SFRP2 had the strongest correlation.

CONCLUSIONS

This study revealed the dynamic expression of the SFRP family in guided bone regeneration with occlusive periosteum in a swine model, providing a possibility to advance the clinical application of bone defect repair.

Trisomy 12 compromises the mesendodermal differentiation propensity of human pluripotent stem cells

Trisomy 12 is one of the most frequent chromosomal abnormalities in cultured human pluripotent stem cells (hPSCs). Although potential oncogenic properties and augmented cell cycle caused by trisomy 12 have been reported, the consequences of trisomy 12 in terms of cell differentiation, which is the basis for regenerative medicine, drug development, and developmental biology studies, have not yet been investigated. Here, we report that trisomy 12 compromises the mesendodermal differentiation of hPSCs. We identified sublines of hPSCs carrying trisomy 12 after their prolonged culture. Transcriptome analysis revealed that these hPSC sublines carried abnormal gene expression patterns in specific signaling pathways in addition to cancer-related cell cycle pathways. These hPSC sublines showed a lower propensity for mesendodermal differentiation in embryoid bodies cultured in a serum-free medium. BMP4-induced exit from the self-renewal state was impaired in the trisomy 12 hPSC sublines, with less upregulation of key transcription factor gene expression. As a consequence, the differentiation efficiency of hematopoietic and hepatic lineages was also impaired in the trisomy 12 hPSC sublines. We reveal that trisomy 12 disrupts the genome-wide expression patterns that are required for proper mesendodermal differentiation.

The evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Dynamic Roles of Signaling Pathways in Maintaining Pluripotency of Mouse and Human Embryonic Stem Cells

Culturing of mouse and human embryonic stem cells (ESCs) in vitro was a major breakthrough in the field of stem cell biology. These models gained popularity very soon mainly due to their pluripotency. Evidently, the ESCs of mouse and human origin share typical phenotypic responses due to their pluripotent nature, such as self-renewal capacity and potency. The conserved network of core transcription factors regulates these responses. However, significantly different signaling pathways and upstream transcriptional networks regulate expression and activity of these core pluripotency factors in ESCs of both the species. In fact, ample evidence shows that a pathway, which maintains pluripotency in mouse ESCs, promotes differentiation in human ESCs. In this review, we discuss the role of canonical signaling pathways implicated in regulation of pluripotency and differentiation particularly in mouse and human ESCs. We believe that understanding these distinct and at times-opposite mechanisms-is critical for the progress in the field of stem cell biology and regenerative medicine.

Electrical stimulation promotes functional recovery after spinal cord injury by activating endogenous spinal cord-derived neural stem/progenitor cell: an in vitro and in vivo study

BACKGROUND CONTEXT

Electrical stimulation is a noninvasive treatment method that has gained popularity in the treatment of spinal cord injury (SCI). Activation of spinal cord-derived neural stem/progenitor cell (SC-NSPC) proliferation and differentiation in the injured spinal cord may elicit considerable neural regenerative effects.

PURPOSE

This study aimed to explore the effect of electrical stimulation on the neurogenesis of SC-NSPCs.

STUDY DESIGN

This study analyzed the effects of electrical stimulation on neurogenesis in rodent SC-NSPCs in vitro and in vivo and evaluated functional recovery and neural circuitry improvements with electrical stimulation using a rodent SCI model.

METHODS

Rats (20 rats/group) were assigned to sham (Group 1), SCI only (Group 2), SCI + electrode implant without stimulation (Group 3), and SCI + electrode with stimulation (Group 4) groups to count total SC-NSPCs and differentiated neurons and to evaluate morphological changes in differentiated neurons. Furthermore, the Basso, Beattie, and Bresnahan scores were analyzed, and the motor- and somatosensory-evoked potentials in all rats were monitored.

RESULTS

Biphasic electrical currents enhanced SC-NSPC proliferation differentiation and caused qualitative morphological changes in differentiated neurons in vitro. Electrical stimulation promoted SC-NSPC proliferation and neuronal differentiation and improved functional outcomes and neural circuitry in SCI models. Increased Wnt3, Wnt7, and β-catenin protein levels were also observed after electrical stimulation.

CONCLUSIONS

Our study proved the beneficial effects of electrical stimulation on SCI. The Wnt/β-catenin pathway activation may be associated with this relationship between electrical stimulation and neuronal regeneration after SCI.

CLINICAL SIGNIFICANCE

The study confirmed the benefits of electrical stimulation on SCI based on cellular, functional, electrophysiological, and histological evidence. Based on these findings, we expect electrical stimulation to make a positive and significant difference in SCI treatment strategies.

Advantages of Using 3D Spheroid Culture Systems in Toxicological and Pharmacological Assessment for Osteogenesis Research

Bone differentiation is crucial for skeletal development and maintenance. Its dysfunction can cause various pathological conditions such as rickets, osteoporosis, osteogenesis imperfecta, or Paget's disease. Although traditional two-dimensional cell culture systems have contributed significantly to our understanding of bone biology, they fail to replicate the intricate biotic environment of bone tissue. Three-dimensional (3D) spheroid cell cultures have gained widespread popularity for addressing bone defects. This review highlights the advantages of employing 3D culture systems to investigate bone differentiation. It highlights their capacity to mimic the complex in vivo environment and crucial cellular interactions pivotal to bone homeostasis. The exploration of 3D culture models in bone research offers enhanced physiological relevance, improved predictive capabilities, and reduced reliance on animal models, which have contributed to the advancement of safer and more effective strategies for drug development. Studies have highlighted the transformative potential of 3D culture systems for expanding our understanding of bone biology and developing targeted therapeutic interventions for bone-related disorders. This review explores how 3D culture systems have demonstrated promise in unraveling the intricate mechanisms governing bone homeostasis and responses to pharmacological agents.

Wnt signaling blockade is essential for maintaining the pluripotency of chicken embryonic stem cells

Activation of Wnt/β-catenin signaling supports the self-renewal of mouse embryonic stem cells. We aimed to understand the effects of Wnt signaling activation or inhibition on chicken embryonic stem cells (chESCs), as these effects are largely unknown. When the glycogen synthase kinase-3 β inhibitor CHIR99021-which activates Wnt signaling-was added to chESC cultures, the colony shape flattened, and the expression levels of pluripotency-related (NANOG, SOX2, SOX3, OCT4, LIN28A, DNMT3B, and PRDM14) and germ cell (CVH and DAZL) markers showed a decreasing trend, and the growth of chESCs was inhibited after approximately 7 d. By contrast, when the Wnt signaling inhibitor XAV939 was added to the culture, dense and compact multipotent colonies (morphologically similar to mouse embryonic stem cell colonies) showing stable expression of pluripotency-related and germline markers were formed. The addition of XAV939 stabilized the proliferation of chESCs in the early stages of culture and promoted their establishment. Furthermore, these chESCs formed chimeras. In conclusion, functional chESCs can be stably cultured using Wnt signaling inhibitors. These findings suggest the importance of Wnt/β-catenin signaling in avian stem cells, offering valuable insights for applied research using chESCs.

Epigenetic Causes of Overgrowth Syndromes

Human overgrowth disorders are characterized by excessive prenatal and/or postnatal growth of various tissues. These disorders often present with tall stature, macrocephaly, and/or abdominal organomegaly and are sometimes associated with additional phenotypic abnormalities such as intellectual disability and increased cancer risk. As the genetic etiology of these disorders have been elucidated, a surprising pattern has emerged. Multiple monogenic overgrowth syndromes result from variants in epigenetic regulators: variants in histone methyltransferases NSD1 and EZH2 cause Sotos syndrome and Weaver syndrome, respectively, variants in DNA methyltransferase DNMT3A cause Tatton-Brown-Rahman syndrome, and variants in chromatin remodeler CHD8 cause an autism spectrum disorder with overgrowth. In addition, very recently, a variant in histone reader protein SPIN4 was identified in a new X-linked overgrowth disorder. In this review, we discuss the genetics of these overgrowth disorders and explore possible common underlying mechanisms by which epigenetic pathways regulate human body size.

Rapid conversion of porcine pluripotent stem cells into macrophages with chemically defined conditions

A renewable source of porcine macrophages derived from pluripotent stem cells (PSCs) would be a valuable alternative to primary porcine alveolar macrophages (PAMs) in the research of host-pathogen interaction mechanisms. We developed an efficient and rapid protocol, within 11 days, to derive macrophages from porcine PSCs (pPSCs). The pPSC-derived macrophages (pPSCdMs) exhibited molecular and functional characteristics of primary macrophages. The pPSCdMs showed macrophage-specific surface protein expression and macrophage-specific transcription factors, similar to PAMs. The pPSCdMs also exhibited the functional characteristics of macrophages, such as endocytosis, phagocytosis, porcine respiratory and reproductive syndrome virus infection and the response to lipopolysaccharide stimulation. Furthermore, we performed transcriptome sequencing of the whole differentiation process to track the fate transitions of porcine PSCs involved in the signaling pathway. The activation of transforming growth factor beta signaling was required for the formation of mesoderm and the inhibition of the transforming growth factor beta signaling pathway at the hematopoietic endothelium stage could enhance the fate transformation of hematopoiesis. In summary, we developed an efficient and rapid protocol to generate pPSCdMs that showed aspects of functional maturity comparable with PAMs. pPSCdMs could provide a broad prospect for the platforms of host-pathogen interaction mechanisms.

Sensory progenitors influence patterning of the mammalian auditory sensory epithelium

During embryonic development Wnt signaling has been shown to influence proliferation and sensory formation in the cochlea. How the dual nature of Wnt signaling is coordinated is unknown. In this study, we define a novel role for a Wnt regulated gene, Mybl2, which was already known to be important for proliferation, in influencing patterning and determining the size of the sensory epithelium in the murine cochlea. Using a quantitative spatial analysis approach and analyzing Mybl2 loss-of-function cochleas, we show that Mybl2 simultaneously specifies the progenitor niche and the size of the sensory domain, and influences the positioning of the medial sensory domain boundary via Jag1 regulation during the mid-gestational stages. Mybl2 conditional knockout resulted in a decrease of proliferation within the progenitor niche. During the late embryonic stages, conditional knockout of Mybl2 produced a wider sensory epithelium across the radial axis with an increase in ectopic inner hair cell formation. These data suggest that Mybl2 -positive progenitors play a role in boundary formation and patterning the sensory epithelium.

Summary Statement

Mybl2 is a Wnt-regulated gene encoding a transcription factor that is expressed in the cochlear progenitor niche and influences the boundary formation between the niche and the sensory domain during mid-cochlear developmental stages, thereby impacting the size of the sensory epithelium.

Haploid androgenetic development of bovine embryos reveals imbalanced WNT signaling and impaired cell fate differentiation†

Haploid embryos have contributed significantly to our understanding of the role of parental genomes in development and can be applied to important biotechnology for human and animal species. However, development to the blastocyst stage is severely hindered in bovine haploid androgenetic embryos (hAE). To further our understanding of such developmental arrest, we performed a comprehensive comparison of the transcriptomic profile of morula-stage embryos, which were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) of transcripts associated with differentiation in haploid and biparental embryos. Among numerous disturbances, results showed that pluripotency pathways, especially the wingless-related integration site (WNT) signaling, were particularly unbalanced in hAE. Moreover, transcript levels of KLF4, NANOG, POU5F1, SOX2, CDX2, CTNNBL1, AXIN2, and GSK3B were noticeably altered in hAE, suggesting disturbance of pluripotency and canonical WNT pathways. To evaluate the role of WNT on hAE competence, we exposed early Day-5 morula stage embryos to the GSK3B inhibitor CHIR99021. Although no alterations were observed in pluripotency and WNT-related transcripts, exposure to CHIR99021 improved their ability to reach the blastocysts stage, confirming the importance of the WNT pathway in the developmental outcome of bovine hAE.

OCT4 regulates WNT/β-catenin signaling and prevents mesoendoderm differentiation by repressing EOMES in porcine pluripotent stem cells

The regulatory network between signaling pathways and transcription factors (TFs) is crucial for the maintenance of pluripotent stem cells. However, little is known about how the key TF OCT4 coordinates signaling pathways to regulate self-renewal and lineage differentiation of porcine pluripotent stem cells (pPSCs). Here, we explored the function of OCT4 in pPSCs by transcriptome and chromatin accessibility analysis. The TFs motif enrichment analysis revealed that, following OCT4 knockdown, the regions of increased chromatin accessibility were enriched with EOMES, GATA6, and FOXA1, indicating that pPSCs differentiated toward the mesoendoderm (ME) lineage. Besides, pPSCs rapidly differentiated into ME when the WNT/β-catenin inhibitor XAV939 was removed. However, the ME differentiation of pPSCs caused by OCT4 knockdown did not rely on the activation of WNT/β-catenin signaling because the target gene of WNT/β-catenin signaling, AXIN2 was not upregulated after OCT4 knockdown, despite significant upregulation of WLS and some WNT ligands. Importantly, OCT4 is directly bound to the promoter and enhancers of EOMES and repressed its transcription. Overexpression of EOMES was sufficient to induce ME differentiation in the presence of XAV939. These results demonstrate that OCT4 can regulate WNT/β-catenin signaling and prevent ME differentiation of pPSCs by repressing EOMES transcription.

Mitochondrial leak metabolism induces the Spemann-Mangold Organizer via Hif-1α in Xenopus

An instructive role for metabolism in embryonic patterning is emerging, although a role for mitochondria is poorly defined. We demonstrate that mitochondrial oxidative metabolism establishes the embryonic patterning center, the Spemann-Mangold Organizer, via hypoxia-inducible factor 1α (Hif-1α) in Xenopus. Hypoxia or decoupling ATP production from oxygen consumption expands the Organizer by activating Hif-1α. In addition, oxygen consumption is 20% higher in the Organizer than in the ventral mesoderm, indicating an elevation in mitochondrial respiration. To reconcile increased mitochondrial respiration with activation of Hif-1α, we discovered that the "free" c-subunit ring of the F1Fo ATP synthase creates an inner mitochondrial membrane leak, which decouples ATP production from respiration at the Organizer, driving Hif-1α activation there. Overexpression of either the c-subunit or Hif-1α is sufficient to induce Organizer cell fates even when β-catenin is inhibited. We propose that mitochondrial leak metabolism could be a general mechanism for activating Hif-1α and Wnt signaling.

Derivation of new pluripotent stem cells from human extended pluripotent stem cells with formative features and trophectoderm potential

Previous studies have demonstrated the existence of intermediate stem cells, which have been successfully obtained from human naive pluripotent stem cells (PSCs) and peri-implantation embryos. However, it is not known whether human extended pluripotent stem cells (hEPSCs) can be directly induced into intermediate stem cells. Moreover, the ability of extra-embryonic lineage differentiation in intermediate stem cells has not been verified. In this issue, we transformed hEPSCs into a kind of novel intermediate pluripotent stem cell resembling embryonic days 8-9 (E8-E9) epiblasts and proved its feature of formative epiblasts. We engineered hEPSCs from primed hPSCs under N2B27-LCDM (N2B27 plus Lif, CHIR, DiH and MiH) conditions. Then, we added Activin A, FGF and XAV939 to modulate signalling pathways related to early humans' embryogenesis. We performed RNA-seq and CUT&Tag analysis to compare with AF9-hPSCs from different pluripotency stages of hPSCs. Trophectoderm (TE), primordial germ cells-like cells (PGCLC) and endoderm, mesoderm, and neural ectoderm induction were conducted by specific small molecules and proteins. AF9-hPSCs transcription resembled that of E8-E9 peri-implantation epiblasts. Signalling pathway responsiveness and histone methylation further revealed their formative pluripotency. Additionally, AF9-hPSCs responded directly to primordial germ cells (PGCs) specification and three germ layer differentiation signals in vitro. Moreover, AF9-hPSCs could differentiate into the TE lineage. Therefore, AF9-hPSCs represented an E8-E9 formative pluripotency state between naïve and primed pluripotency, opening new avenues for studying human pluripotency development during embryogenesis.

Generation of stable integration-free pig induced pluripotent stem cells under chemically defined culture condition

Genome integration-free pig induced pluripotent stem cells (iPSCs) bring tremendous value in pre-clinical testing of regenerative medicine, as well as conservation and exploitation of endangered or rare local pig idioplasmatic resources. However, due to a lack of appropriate culture medium, efficient induction and stable maintenance of pig iPSCs with practical value remains challenging. Here, we established an efficient induction system for exogenous gene-independent iPSCs under chemically defined culture condition previously used for generation of stable pig pre-gastrulation epiblast stem cells (pgEpiSCs). WNT suppression was found to play an essential role in establishment of exogenous gene-independent iPSCs. Strikingly, stable integration-free pig iPSCs could be established from pig somatic cells using episomal vectors in this culture condition. The iPSCs had pluripotency features and transcriptome characteristics approximating pgEpiSCs. More importantly, this induction system may be used to generate integration-free iPSCs from elderly disabled rare local pig somatic cells and the iPSCs could be gene-edited and used as donor cells for nuclear transfer. Our results provide novel insights into potential applications for genetic breeding of livestock species and pre-clinical evaluation of regenerative medicine.

Elaiophylin Elicits Robust Anti-Tumor Responses via Apoptosis Induction and Attenuation of Proliferation, Migration, Invasion, and Angiogenesis in Pancreatic Cancer Cells

Pancreatic cancer remains a formidable challenge in oncology due to its aggressive nature and limited treatment options. In this study, we investigate the potential therapeutic efficacy of elaiophylin, a novel compound, in targeting BxPC-3 and PANC-1 pancreatic cancer cells. We comprehensively explore elaiophylin's impact on apoptosis induction, proliferation inhibition, migration suppression, invasion attenuation, and angiogenesis inhibition, key processes contributing to cancer progression and metastasis. The results demonstrate that elaiophylin exerts potent pro-apoptotic effects, inducing a substantial increase in apoptotic cells. Additionally, elaiophylin significantly inhibits proliferation, migration, and invasion of BxPC-3 and PANC-1 cells. Furthermore, elaiophylin exhibits remarkable anti-angiogenic activity, effectively disrupting tube formation in HUVECs. Moreover, elaiophylin significantly inhibits the Wnt/β-Catenin signaling pathway. Our findings collectively demonstrate the multifaceted potential of elaiophylin as a promising therapeutic agent against pancreatic cancer via inhibition of the Wnt/β-Catenin signaling pathway. By targeting diverse cellular processes crucial for cancer progression, elaiophylin emerges as a prospective candidate for future targeted therapies. Further investigation of the in vivo efficacy of elaiophylin is warranted, potentially paving the way for novel and effective treatment approaches in pancreatic cancer management.

TGF-β and SHH Regulate Pluripotent Stem Cell Differentiation into Brain Microvascular Endothelial Cells in Generating an In Vitro Blood-Brain Barrier Model

Blood-brain barrier (BBB) models are important tools for studying CNS drug delivery, brain development, and brain disease. In vitro BBB models have been obtained from animals and immortalized cell lines; however, brain microvascular endothelial cells (BMECs) derived from them have several limitations. Furthermore, obtaining mature brain microvascular endothelial-like cells (BME-like cells) from human pluripotent stem cells (hPSCs) with desirable properties for establishing BBB models has been challenging. Here, we developed an efficient method for differentiating hPSCs into BMECs that are amenable to the development and application of human BBB models. The established conditions provided an environment similar to that occurring during BBB differentiation in the presence of the co-differentiating neural cell population by the modulation of TGF-β and SHH signaling. The developed BME-like cells showed well-organized tight junctions, appropriate expression of nutrient transporters, and polarized efflux transporter activity. In addition, BME-like cells responded to astrocytes, acquiring substantial barrier properties as measured by transendothelial electrical resistance. Moreover, the BME-like cells exhibited an immune quiescent property of BBB endothelial cells by decreasing the expression of adhesion molecules. Therefore, our novel cellular platform could be useful for drug screening and the development of brain-permeable pharmaceuticals.

WNT pathway in focal cortical dysplasia compared to perilesional nonlesional tissue in refractory epilepsies

BACKGROUND

Focal cortical dysplasia (FCD) is a malformation of cortical development that causes medical refractory seizures, and one of the main treatments may be surgical resection of the affected area of the brain. People affected by FCD may present with seizures of variable severity since childhood. Despite many medical treatments available, only surgery can offer cure. The pathophysiology of the disease is not yet understood; however, it is known that several gene alterations may play a role. The WNT/β-catenin pathway is closely related to the control and balance of cell proliferation and differentiation in the central nervous system. The aim of this study was to explore genes related to the WNT/β-catenin pathway in lesional and perilesional brain tissue in patients with FCD type II.

METHODS

Dysplastic and perilesional tissue from the primary dysplastic lesion of patients with FCD type IIa were obtained from two patients who underwent surgical treatment. The analysis of the relative expression of genes was performed by a qRT-PCR array (super array) containing 84 genes related to the WNT pathway.

RESULTS

Our results suggest the existence of molecular alteration in some genes of the WNT pathway in tissue with dysplastic lesions and of perilesional tissue. We call this tissue of normal-appearing adjacent cortex (NAAC). Of all genes analyzed, a large number of genes show similar behavior between injured, perilesional and control tissues. However, some genes have similar characteristics between the perilesional and lesional tissue and are different from the control brain tissue, presenting the perilesional tissue as a molecularly altered material.

CONCLUSION

Our results suggest that the perilesional area after surgical resection of tissue with cortical dysplasia presents molecular changes that may play a role in the recurrence of seizures in these patients. The perilesional tissue should receive expanded attention beyond the somatic mutations described and associated with FCD, such as mTOR, for example, to new signaling pathways that may play a crucial role in seizure recurrence.

Neuropeptide substance P: A promising regulator of wound healing in diabetic foot ulcers

In the past, neuropeptide substance P (SP) was predominantly recognized as a neuroinflammatory factor, while its potent healing activity was overlooked. This paper aims to review the regulatory characteristics of neuropeptide SP in both normal and diabetic wound healing. SP actively in the regulation of wound healing-related cells directly and indirectly, exhibiting robust inflammatory properties, promoting cell proliferation and migration and restoring the activity and paracrine ability of skin cells under diabetic conditions. Furthermore, SP not only regulates healing-related cells but also orchestrates the immune environment, thereby presenting unique and promising application prospects in wound intervention. As new SP-based preparations are being explored, SP-related drugs are poised to become an effective therapeutic intervention for diabetic foot ulcers (DFU).

The time-resolved genomic impact of Wnt/β-catenin signaling

Wnt signaling orchestrates gene expression via its effector, β-catenin. However, it is unknown whether β-catenin binds its target genomic regions simultaneously and how this impacts chromatin dynamics to modulate cell behavior. Using a combination of time-resolved CUT&RUN against β-catenin, ATAC-seq, and perturbation assays in different cell types, we show that Wnt/β-catenin physical targets are tissue-specific, β-catenin "moves" on different loci over time, and its association to DNA accompanies changing chromatin accessibility landscapes that determine cell behavior. In particular, Wnt/β-catenin progressively shapes the chromatin of human embryonic stem cells (hESCs) as they undergo mesodermal differentiation, a behavior that we define as "plastic." In HEK293T cells, on the other hand, Wnt/β-catenin drives a transient chromatin opening, followed by re-establishment of the pre-stimulation state, a response that we define as "elastic." Future experiments shall assess whether other cell communication mechanisms, in addition to Wnt signaling, are ruled by time, cellular idiosyncrasies, and chromatin constraints. A record of this paper's transparent peer review process is included in the supplemental information.

Optogenetic control of Wnt signaling models cell-intrinsic embryogenic patterning using 2D human pluripotent stem cell culture

In embryonic stem cell (ESC) models for early development, spatially and temporally varying patterns of signaling and cell types emerge spontaneously. However, mechanistic insight into this dynamic self-organization is limited by a lack of methods for spatiotemporal control of signaling, and the relevance of signal dynamics and cell-to-cell variability to pattern emergence remains unknown. Here, we combine optogenetic stimulation, imaging and transcriptomic approaches to study self-organization of human ESCs (hESC) in two-dimensional (2D) culture. Morphogen dynamics were controlled via optogenetic activation of canonical Wnt/β-catenin signaling (optoWnt), which drove broad transcriptional changes and mesendoderm differentiation at high efficiency (>99% cells). When activated within cell subpopulations, optoWnt induced cell self-organization into distinct epithelial and mesenchymal domains, mediated by changes in cell migration, an epithelial to mesenchymal-like transition and TGFβ signaling. Furthermore, we demonstrate that such optogenetic control of cell subpopulations can be used to uncover signaling feedback mechanisms between neighboring cell types. These findings reveal that cell-to-cell variability in Wnt signaling is sufficient to generate tissue-scale patterning and establish a hESC model system for investigating feedback mechanisms relevant to early human embryogenesis.

Evaluation of the effect of boron derivatives on cardiac differentiation of mouse pluripotent stem cells

BACKGROUND

The heart is one of the first organs to form during embryonic development and has a very important place. So much that the formation of a functional heart is completed on the 55th day of human development and the 15th day of mouse development. Myocardial, endocardial and epicardial cells, which are derived from the mesoderm layer, are the cells that form the basis of the heart. Cardiac development, like other embryonic developments, is tightly controlled and regulated by various signaling pathways. The WNT signaling pathway is the most studied of these signaling pathways and the one with the clearest relationship with heart development. It is known that boron compounds and the Wnt/β-catenin pathway are highly correlated. Therefore, this study aimed to investigate the role of boron compounds in heart development as well as its effect on pluripotency of mouse embryonic stem cells for the first time in the literature.

METHODS

Toxicity of boron compounds was evaluated by using MTS analysis and obtained results were supported by morphological pictures, Trypan Blue staining and Annexin V staining. Additionally, the possible boron-related change in pluripotency of embryonic stem cells were analyzed with alkaline phosphatase activity and immunocytochemical staining of Oct4 protein as well as gene expression levels of pluripotency related OCT4, SOX2 and KLF4 genes. The alterations in the embryonic body formation capacity of mouse embryonic stem cells due to the application boron derivatives were also evaluated. Three linage differentiation was conducted to clarify the real impact of boron compounds on embryonic development. Lastly, cardiac differentiation of mESCs was investigated by using morphological pictures, cytosolic calcium measurement, gene expression and immunocytochemical analysis of cardiac differentiation related genes and in the presence of boron compounds.

RESULTS

Obtained results show that boron treatment maintains the pluripotency of embryonic stem cells at non-toxic concentrations. Additionally, endodermal, and mesodermal fate was found to be triggered after boron treatment. Also, initiation of cardiomyocyte differentiation by boron derivative treatments caused an increased gene expression levels of cardiac differentiation related TNNT2, Nkx2.5 and ISL-1 gene expression levels.

CONCLUSION

This study indicates that boron application, which is responsible for maintaining pluripotency of mESCs, can be used for increased cardiomyocyte differentiation of mESCs.

Wnt/β-Catenin Signaling Activation Induces Differentiation in Human Limbal Epithelial Stem Cells Cultured Ex Vivo

Human limbal epithelial stem cells (hLESCs) continuously replenish lost or damaged human corneal epithelial cells. The percentage of stem/progenitor cells in autologous ex vivo expanded tissue is essential for the long-term success of transplantation in patients with limbal epithelial stem cell deficiency. However, the molecular processes governing the stemness and differentiation state of hLESCs remain uncertain. Therefore, we sought to explore the impact of canonical Wnt/β-catenin signaling activation on hLESCs by treating ex vivo expanded hLESC cultures with GSK-3 inhibitor LY2090314. Real-time qRT-PCR and microarray data reveal the downregulation of stemness (TP63), progenitor (SOX9), quiescence (CEBPD), and proliferation (MKI67, PCNA) genes and the upregulation of genes for differentiation (CX43, KRT3) in treated- compared to non-treated samples. The pathway activation was shown by AXIN2 upregulation and enhanced levels of accumulated β-catenin. Immunocytochemistry and Western blot confirmed the findings for most of the above-mentioned markers. The Wnt/β-catenin signaling profile demonstrated an upregulation of WNT1, WNT3, WNT5A, WNT6, and WNT11 gene expression and a downregulation for WNT7A and DKK1 in the treated samples. No significant differences were found for WNT2, WNT16B, WIF1, and DKK2 gene expression. Overall, our results demonstrate that activation of Wnt/β-catenin signaling in ex vivo expanded hLESCs governs the cells towards differentiation and reduces proliferation and stem cell maintenance capability.

Single-cell response to Wnt signaling activation reveals uncoupling of Wnt target gene expression

Wnt signaling drives nuclear translocation of β-catenin and its subsequent association with the DNA-bound TCF/LEF transcription factors, which dictate target gene specificity by recognizing Wnt responsive elements across the genome. β-Catenin target genes are therefore thought to be collectively activated upon Wnt pathway stimulation. However, this appears in contrast with the non-overlapping patterns of Wnt target gene expression in several contexts, including early mammalian embryogenesis. Here we followed Wnt target gene expression in human embryonic stem cells after Wnt pathway stimulation at a single-cell resolution. Cells changed gene expression program over time consistent with three key developmental events: i) loss of pluripotency, ii) induction of Wnt target genes, and iii) mesoderm specification. Contrary to our expectation, not all cells displayed equal amplitude of Wnt target gene activation; rather, they distributed in a continuum from strong to weak responders when ranked based on the expression of the target AXIN2. Moreover, high AXIN2 did not always correspond to elevated expression of other Wnt targets, which were activated in different proportions in individual cells. The uncoupling of Wnt target gene expression was also identified in single cell transcriptomics profiling of other Wnt-responding cell types, including HEK293T, murine developing forelimbs, and human colorectal cancer. Our finding underlines the necessity to identify additional mechanisms that explain the heterogeneity of the Wnt/β-catenin-mediated transcriptional outputs in single cells.

Wnt3a-Loaded Extracellular Vesicles Promote Alveolar Epithelial Regeneration after Lung Injury

Compromised regeneration resulting from the deactivation of Wnt/β-catenin signaling contributes to the progression of chronic obstructive pulmonary disease (COPD) with limited therapeutic options. Extracellular cytokine-induced Wnt-based signaling provides an alternative option for COPD treatment. However, the hydrophobic nature of Wnt proteins limits their purification and use. This study devises a strategy to deliver the membrane-bound wingless-type MMTV integration site family, member 3A (Wnt3a) over a long distance by anchoring it to the surface of extracellular vesicles (EVs). The newly engineered Wnt3aWG EVs are generated by co-expressing Wnt3a with two genes encoding the membrane protein, WLS, and an engineered glypican, GPC6ΔGPI -C1C2. The bioactivity of Wnt3aWG EVs is validated using a TOPFlash assay and a mesoderm differentiation model of human pluripotent stem cells. Wnt3aWG EVs activate Wnt signaling and promote cell growth following human alveolar epithelial cell injury. In an elastase-induced emphysema model, impaired pulmonary function and enlarged airspace are greatly restored by the intravenous delivery of Wnt3aWG EVs. Single-cell RNA sequencing-based analyses further highlight that Wnt3aWG EV-activated regenerative programs are responsible for its beneficial effects. These findings suggest that EV-based Wnt3a delivery represents a novel therapeutic strategy for lung repair and regeneration after injury.

Molecular Mechanisms Underlying Pluripotency and Self-Renewal of Embryonic Stem Cells

Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of the blastocyst. ESCs have two distinctive properties: ability to proliferate indefinitely, a feature referred as "self-renewal", and to differentiate into different cell types, a peculiar characteristic known as "pluripotency". Self-renewal and pluripotency of ESCs are finely orchestrated by precise external and internal networks including epigenetic modifications, transcription factors, signaling pathways, and histone modifications. In this systematic review, we examine the main molecular mechanisms that sustain self-renewal and pluripotency in both murine and human ESCs. Moreover, we discuss the latest literature on human naïve pluripotency.

Quantitative Proteomics for the Development and Manufacturing of Human-Induced Pluripotent Stem Cell-Derived Neural Stem Cells Using Data-Independent Acquisition Mass Spectrometry

Human-induced pluripotent stem cell (iPSC)-derived neural stem cells (NSCs) have several potential applications in regenerative medicine. A deep understanding of stem cell characteristics is critical for developing appropriate products for use in the clinic. This study aimed to develop approaches for characterizing iPSC-derived NSCs. Data-independent acquisition mass spectrometry (DIA-MS) was used to obtain temporal proteomic profiles of differentiating cells. Principal component analysis of the proteome profiles allowed for the discrimination of cells cultured for different periods. Cells were characterized by Gene Ontology analysis to annotate the upregulated proteins based on their functions. We found that trophoblast glycoprotein (TPBG), a membrane glycoprotein that inhibits the Wnt/β-catenin pathway, was elevated in NSC and that silencing TPBG promoted proliferation rather than neuronal differentiation. Treatment with Wnt/β-catenin pathway activators and inhibitors showed that modulating the Wnt/β-catenin pathway is crucial for differentiation into NSC. These results suggest that the level of TPBG is critical for differentiation into NSC, and TPBG is a potentially critical quality attribute of differentiating cells. In summary, DIA-MS-based proteomics is a promising multi-attribute method for characterizing stem cell-derived products.

Wnt signaling in stem cells during development and cell lineage specification

During embryo development, cell proliferation, cell fate specification and tissue patterning are coordinated and tightly regulated by a handful of evolutionarily conserved signaling pathways activated by secreted growth factor families including fibroblast growth factor (FGF), Nodal/bone morphogenetic protein (BMP), Hedgehog and Wnt. The spatial and temporal activation of these signaling pathways elicit context-specific cellular responses that ultimately shape the different tissues of the embryo. Extensive efforts have been dedicated to identifying the molecular mechanisms underlying these signaling pathways during embryo development, adult tissue homeostasis and regeneration. In this review, we first describe the role of the Wnt/β-catenin signaling pathway during early embryo development, axis specification and cell differentiation as a prelude to highlight how this knowledge is being leveraged to manipulate Wnt/β-catenin signaling activity with small molecules and biologics for the directed differentiation of pluripotent stem cells into various cell lineages that are physiologically relevant for stem cell therapy and regenerative medicine.

Inhibition of GSK3β Promotes Proliferation and Suppresses Apoptosis of Porcine Muscle Satellite Cells

As the global population increases, interest in cultured meat (a new research field) is gradually increasing. The main raw material for the production of cultured meat is muscle stem cells called satellite cells isolated from livestock. However, how to mass proliferate and maintain satellite cells in vitro without genetic manipulation remains unclear. In the present study, we isolated and purified porcine muscle satellite cells (PMSCs) from the femur of a 1-day-old piglet and cultured PMSCs by treating them with an inhibitor (XAV939, Tankyrase (TNKS) inhibitor) or an activator (CHIR99021, glycogen synthase kinase 3 beta (GSK3β) inhibitor) of Wnt signaling. The CHIR group treated with 3 μM CHIR99021 showed a significantly increased proliferation rate of PMSCs compared to the SC group (control), whereas the XAV group treated with 1 μM XAV939 showed a significantly decreased proliferation rate of PMSCs. CHIR99021 also inhibited the differentiation of PMSCs by reducing the expression of MyoD while maintaining the expression of Pax7 and suppressed apoptosis by regulating the expression of apoptosis-related proteins and genes. RNA sequencing was performed to obtain gene expression profiles following inhibition or activation of the Wnt signaling pathway and various signaling mechanisms related to the maintenance of satellite cells were identified. Our results suggest that inhibition of GSK3β could dramatically improve the maintenance and mass proliferation ability of PMSCs in vitro by regulating the expression of myogenic markers and the cell cycle.

Virtual cells in a virtual microenvironment recapitulate early development-like patterns in human pluripotent stem cell colonies

The mechanism by which morphogenetic signals engage the regulatory networks responsible for early embryonic tissue patterning is incompletely understood. Here, we developed a minimal gene regulatory network (GRN) model of human pluripotent stem cell (hPSC) lineage commitment and embedded it into "cellular" agents that respond to a dynamic morphogenetic signaling microenvironment. Simulations demonstrated that GRN wiring had significant non-intuitive effects on tissue pattern order, composition, and dynamics. Experimental perturbation of GRN connectivities supported model predictions and demonstrated the role of OCT4 as a master regulator of peri-gastrulation fates. Our so-called GARMEN strategy provides a multiscale computational platform to understand how single-cell-based regulatory interactions scale to tissue domains. This foundation provides new opportunities to simulate the impact of network motifs on normal and aberrant tissue development.

A natural transdifferentiation event involving mitosis is empowered by integrating signaling inputs with conserved plasticity factors

Transdifferentiation, or direct cell reprogramming, is the conversion of one fully differentiated cell type into another. Whether core mechanisms are shared between natural transdifferentiation events when occurring with or without cell division is unclear. We have previously characterized the Y-to-PDA natural transdifferentiation in Caenorhabditis elegans, which occurs without cell division and requires orthologs of vertebrate reprogramming factors. Here, we identify a rectal-to-GABAergic transdifferentiation and show that cell division is required but not sufficient for conversion. We find shared mechanisms, including erasure of the initial identity, which requires the conserved reprogramming factors SEM-4/SALL, SOX-2, CEH-6/OCT, and EGL-5/HOX. We also find three additional and parallel roles of the Wnt signaling pathway: selection of a specific daughter, removal of the initial identity, and imposition of the precise final subtype identity. Our results support a model in which levels and antagonistic activities of SOX-2 and Wnt signaling provide a timer for the acquisition of final identity.

Glycogen Synthase Kinase 3β inhibits BMSCs Chondrogenesis in Inflammation via the Cross-Reaction between NF-κB and β-Catenin in the Nucleus

Inflammation can influence the pluripotency and self-renewal of mesenchymal stem cells (MSCs), thereby altering their cartilage regeneration ability. Sprague-Dawley (SD) rat bone marrow mesenchymal stem cells (BMSCs) were isolated and found to be defective in differentiation potential in the interleukin-1β- (IL-1β-) induced inflammatory microenvironment. Glycogen synthase kinase-3β (GSK-3β) is an evolutionarily conserved serine/threonine kinase that plays a role in numerous cellular processes. The role of GSK-3β in inflammation may be related to the nuclear factor-κB (NF-κB) signaling pathway and the Wnt/β-catenin signaling pathway, whose mechanism remains unclear. In this study, we found that GSK-3β can inhibit chondrogenesis of IL-1β-impaired BMSCs by disrupting metabolic balance and promoting cell apoptosis. By using the inhibitors LiCl and SN50, we demonstrated that GSK-3β regulates the chondrogenesis via the NF-κB and Wnt/β-catenin signaling pathways and possibly mediates the cross-reaction between NF-κB and β-catenin in the nucleus. Given the molecular mechanisms of GSK-3β in chondrogenic differentiation in inflammation, GSK-3β is a crucial target for the treatment of inflammation-induced cartilage disease.

Hsa-miR-150-5p inhibits Wnt-β-catenin signaling in human corneal epithelial stem cells

PURPOSE

In our earlier study, we identified hsa-miR-150-5p as a highly expressed miRNA in enriched corneal epithelial stem cells (CESCs). In this study, we aimed to understand the molecular regulatory function of hsa-miR-150-5p in association with the maintenance of stemness in CESCs.

METHODS

The target mRNAs of hsa-miR-150-5p were predicted and subjected to pathway analysis to identify targets for functional studies. Primary cultured limbal epithelial cells were transfected with hsa-miR-150-5p mimic, inhibitor, or scrambled sequence using Lipofectamine 3000. The transfected cells were analyzed to determine (i) their colony-forming potential; (ii) the expression levels of stem cell (SC) markers/transcription factors (ABCG2, NANOG, OCT4, KLF4, and ΔNp63), the differentiation marker (Cx43), and the hsa-miR-150-5p predicted targets (JARID2, INHBA, AKT3, and CTNNB1) by qPCR; and (iii) the expression levels of ABCG2, p63α, Cx43, JARID2, AKT3, p-AKT3, β-catenin, and active β-catenin by immunofluorescence staining and/or western blotting.

RESULTS

The ectopic expression level of hsa-miR-150-5p increased the colony-forming potential (8.29% ± 0.47%, p < 0.001) with the ability to form holoclone-like colonies compared with the control (1.8% ± 0.47%). The mimic-treated cells had higher expression levels of the SC markers but reduced expression levels of Cx43 and the targets of hsa-miR-150-5p that are involved in the Wnt-β-catenin signaling pathway. The expression levels of β-catenin and active β-catenin in the inhibitor-transfected cells were higher than those in the control cells, and the localized nuclear expression indicated the activation of Wnt signaling.

CONCLUSIONS

Our results indicate a regulatory role for hsa-miR-150-5p in the maintenance of CESCs by inhibiting the Wnt signaling pathway.

ID proteins promote the survival and primed-to-naive transition of human embryonic stem cells through TCF3-mediated transcription

Inhibition of DNA binding proteins 1 and 3 (ID1 and ID3) are important downstream targets of BMP signalling that are necessary for embryonic development. However, their specific roles in regulating the pluripotency of human embryonic stem cells (hESCs) remain unclear. Here, we examined the roles of ID1 and ID3 in primed and naive-like hESCs and showed that ID1 and ID3 knockout lines (IDs KO) exhibited decreased survival in both primed and naive-like state. IDs KO lines in the primed state also tended to undergo pluripotent dissolution and ectodermal differentiation. IDs KO impeded the primed-to-naive transition (PNT) of hESCs, and overexpression of ID1 in primed hESCs promoted PNT. Furthermore, single-cell RNA sequencing demonstrated that ID1 and ID3 regulated the survival and pluripotency of hESCs through the AKT signalling pathway. Finally, we showed that TCF3 mediated transcriptional inhibition of MCL1 promotes AKT phosphorylation, which was confirmed by TCF3 knockdown in KO lines. Our study suggests that IDs/TCF3 acts through AKT signalling to promote survival and maintain pluripotency of both primed and naive-like hESCs.

Oxidative stress as a candidate mechanism for accelerated neuroectodermal differentiation due to trisomy 21

The ubiquity of cognitive deficits and early onset Alzheimer's disease in Down syndrome (DS) has focused much DS iPSC-based research on neuron degeneration and regeneration. Despite reports of elevated oxidative stress in DS brains, few studies assess the impact of this oxidative burden on iPSC differentiation. Here, we evaluate cellular specific redox differences in DS and euploid iPSCs and neural progenitor cells (NPCs) during critical intermediate stages of differentiation. Despite successful generation of NPCs, our results indicate accelerated neuroectodermal differentiation of DS iPSCs compared to isogenic, euploid controls. Specifically, DS embryoid bodies (EBs) and neural rosettes prematurely develop with distinct morphological differences from controls. Additionally, we observed developmental stage-specific alterations in mitochondrial superoxide production and SOD1/2 abundance, coupled with modulations in thioredoxin, thioredoxin reductase, and peroxiredoxin isoforms. Disruption of intracellular redox state and its associated signaling has the potential to disrupt cellular differentiation and development in DS lending to DS-specific phenotypes.

Disruption of β-catenin-mediated negative feedback reinforces cAMP-induced neuronal differentiation in glioma stem cells

Accumulating evidence supports the existence of glioma stem cells (GSCs) and their critical role in the resistance to conventional treatments for glioblastoma multiforme (GBM). Differentiation therapy represents a promising alternative strategy against GBM by forcing GSCs to exit the cell cycle and reach terminal differentiation. In this study, we demonstrated that cAMP triggered neuronal differentiation and compromised the self-renewal capacity in GSCs. In addition, cAMP induced negative feedback to antagonize the differentiation process by activating β-catenin pathway. Suppression of β-catenin signaling synergized with cAMP activators to eliminate GSCs in vitro and extended the survival of animals in vivo. The cAMP/PKA pathway stabilized β-catenin through direct phosphorylation of the molecule and inhibition of GSK-3β. The activated β-catenin translocated into the nucleus and promoted the transcription of APELA and CARD16, which were found to be responsible for the repression of cAMP-induced differentiation in GSCs. Overall, our findings identified a negative feedback mechanism for cAMP-induced differentiation in GSCs and provided potential targets for the reinforcement of differentiation therapy for GBM.

A Quick and Efficient Method for the Generation of Immunomodulatory Mesenchymal Stromal Cell from Human Induced Pluripotent Stem Cell

Mesenchymal stromal cells (MSCs) have been widely investigated for their regenerative capacity, anti-inflammatory properties and beneficial immunomodulatory effects across multiple clinical indications. Nevertheless, their widespread clinical utilization is limited by the variability in MSC quality, impacted by donor age, metabolism, and disease. Human induced pluripotent stem cells (hiPSCs) generated from readily accessible donor tissues, are a promising source of stable and rejuvenated MSC but differentiation methods generally require prolonged culture and result in low frequencies of stable MSCs. To overcome this limitation, we have optimized a quick and efficient method for hiPSC differentiation into footprint-free MSCs (human induced MSCs [hiMSCs]) in this study. This method capitalizes on the synergistic action of growth factors Wnt3a and Activin A with bone morphogenetic protein-4 (BMP4), leading to an enrichment of MSC after only 4 days of treatment. These hiMSCs demonstrate a significant upregulation of mesenchymal stromal markers (CD105+, CD90+, CD73, and cadherin 11) compared with bone marrow-derived MSCs (bmMSCs), with reduced expression of the pluripotency genes (octamer-binding transcription factor [Oct-4], cellular myelocytomatosis oncogene [c-Myc], Klf4, and Nanog homebox [Nanog]) compared with hiPSC. Moreover, they show improved proliferation capacity in culture without inducing any teratoma formation in vivo. Osteogenesis, chondrogenesis, and adipogenesis assays confirmed the ability of hiMSCs to differentiate into the three different lineages. Secretome analyses showed cytokine profiles compared with bmMSCs. Encapsulated hiMSCs in alginate beads cocultured with osteoarthritic (OA) cartilage explants showed robust immunomodulation, with stimulation of cell growth and proteoglycan production in OA cartilage. Our quick and efficient protocol for derivation of hiMSC from hiPSC, and their encapsulation in microbeads, therefore, presents a reliable and reproducible method to boost the clinical applications of MSCs.

Regulated interaction of ID2 with the anaphase-promoting complex links progression through mitosis with reactivation of cell-type-specific transcription

Tissue-specific transcriptional activity is silenced in mitotic cells but it remains unclear whether the mitotic regulatory machinery interacts with tissue-specific transcriptional programs. We show that such cross-talk involves the controlled interaction between core subunits of the anaphase-promoting complex (APC) and the ID2 substrate. The N-terminus of ID2 is independently and structurally compatible with a pocket composed of core APC/C subunits that may optimally orient ID2 onto the APCCDH1 complex. Phosphorylation of serine-5 by CDK1 prevented the association of ID2 with core APC, impaired ubiquitylation and stabilized ID2 protein at the mitosis-G1 transition leading to inhibition of basic Helix-Loop-Helix (bHLH)-mediated transcription. The serine-5 phospho-mimetic mutant of ID2 that inefficiently bound core APC remained stable during mitosis, delayed exit from mitosis and reloading of bHLH transcription factors on chromatin. It also locked cells into a "mitotic stem cell" transcriptional state resembling the pluripotent program of embryonic stem cells. The substrates of APCCDH1 SKP2 and Cyclin B1 share with ID2 the phosphorylation-dependent, D-box-independent interaction with core APC. These results reveal a new layer of control of the mechanism by which substrates are recognized by APC.

Therapeutic correction of hemophilia A by transplantation of hPSC-derived liver sinusoidal endothelial cell progenitors

Liver sinusoidal endothelial cells (LSECs) form the predominant microvasculature in the liver where they carry out many functions including the secretion of coagulation factor VIII (FVIII). To investigate the early origins of this lineage, we develop an efficient and scalable protocol to produce human pluripotent stem cell (hPSC)-derived LSEC progenitors characterized as venous endothelial cells (VECs) from different mesoderm subpopulations. Using a sensitive and quantitative vascular competitive transplantation assay, we demonstrate that VECs generated from BMP4 and activin A-induced KDR⁺CD235a/b⁺ mesoderm are 50-fold more efficient at LSEC engraftment than venous cells from BMP4 and WNT-induced KDR⁺CD235a/b^- mesoderm. When transplanted into immunocompromised hemophilia A mice (NSG-HA), these VECs engraft the liver, proliferate, and mature to functional LSECs that secrete bioactive FVIII capable of correcting the bleeding phenotype. Together, these findings highlight the importance of appropriate mesoderm induction for generating hPSC-derived LSECs capable of functioning in a preclinical model of hemophilia A.

Modelling ciliopathy phenotypes in human tissues derived from pluripotent stem cells with genetically ablated cilia

The functions of cilia-antenna-like organelles associated with a spectrum of disease states-are poorly understood, particularly in human cells. Here we show that human pluripotent stem cells (hPSCs) edited via CRISPR to knock out the kinesin-2 subunits KIF3A or KIF3B can be used to model ciliopathy phenotypes and to reveal ciliary functions at the tissue scale. KIF3A-/- and KIF3B-/- hPSCs lacked cilia, yet remained robustly self-renewing and pluripotent. Tissues and organoids derived from these hPSCs displayed phenotypes that recapitulated defective neurogenesis and nephrogenesis, polycystic kidney disease (PKD) and other features of the ciliopathy spectrum. We also show that human cilia mediate a critical switch in hedgehog signalling during organoid differentiation, and that they constitutively release extracellular vesicles containing signalling molecules associated with ciliopathy phenotypes. The capacity of KIF3A-/- and KIF3B-/- hPSCs to reveal endogenous mechanisms underlying complex ciliary phenotypes may facilitate the discovery of candidate therapeutics.

GP2-enriched pancreatic progenitors give rise to functional beta cells in vivo and eliminate the risk of teratoma formation

Human pluripotent stem cell (hPSC)-derived pancreatic progenitors (PPs) can be differentiated into beta-like cells in vitro and in vivo and therefore have therapeutic potential for type 1 diabetes (T1D) treatment. However, the purity of PPs varies across different hPSC lines, differentiation protocols, and laboratories. The uncommitted cells may give rise to non-pancreatic endodermal, mesodermal, or ectodermal derivatives in vivo, hampering the safety of hPSC-derived PPs for clinical applications and their differentiation efficiency in research settings. Recently, proteomics and transcriptomics analyses identified glycoprotein 2 (GP2) as a PP-specific cell surface marker. The GP2-enriched PPs generate higher percentages of beta-like cells in vitro, but their potential in vivo remains to be elucidated. Here, we demonstrate that the GP2-enriched-PPs give rise to all pancreatic cells in vivo, including functional beta-like cells. Remarkably, GP2 enrichment eliminates the risk of teratomas, which establishes GP2 sorting as an effective method for PP purification and safe pancreatic differentiation.

β-catenin links cell seeding density to global gene expression during mouse embryonic stem cell differentiation

Although cell density is known to affect numerous biological processes including gene expression and cell fate specification, mechanistic understanding of what factors link cell density to global gene regulation is lacking. Here, we reveal that the expression of thousands of genes in mouse embryonic stem cells (mESCs) is affected by cell seeding density and that low cell density enhances the efficiency of differentiation. Mechanistically, β-catenin is localized primarily to adherens junctions during both self-renewal and differentiation at high density. However, when mESCs differentiate at low density, β-catenin translocates to the nucleus and associates with Tcf7l1, inducing co-occupied lineage markers. Meanwhile, Esrrb sustains the expression of pluripotency-associated genes while repressing lineage markers at high density, and its association with DNA decreases at low density. Our results provide new insights into the previously neglected but pervasive phenomenon of density-dependent gene regulation.

A Novel Age-Related Circular RNA Circ-ATXN2 Inhibits Proliferation, Promotes Cell Death and Adipogenesis in Rat Adipose Tissue-Derived Stromal Cells

Adipose tissue-derived stromal cells are promising candidates investigating the stem cell-related treatment. However, their proportion and utility in the human body decline with time, rendering stem cells incompetent to complete repair processes in vivo. The involvement of circRNAs in the aging process is poorly understood. Rat subcutaneous adipose tissue from 10-week-old and 27-month-old rats were used for hematoxylin and eosin (H and E) staining, TUNEL staining, and circRNA sequencing. Rat adipose tissue-derived stromal cells were cultured and overexpressed with circ-ATXN2. Proliferation was examined using xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Apoptosis was induced by CoCl2 and examined using flow cytometry. RT-PCR assay and Oil Red O staining were used to measure adipogenesis at 48 h and 14 days, respectively. H and E staining showed that the diameter of adipocytes increased; however, the number of cells decreased in old rats. TUNEL staining showed that the proportion of apoptotic cells was increased in old rats. A total of 4,860 and 4,952 circRNAs was detected in young and old rats, respectively. Among them, 67 circRNAs exhibited divergent expression between the two groups (fold change ≥2, p ≤ 0.05), of which 33 were upregulated (49.3%) and 34 were downregulated (50.7%). The proliferation of circ-ATXN2-overexpressing cells decreased significantly in vitro, which was further validated by xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Overexpression of circ-ATXN2 significantly increased the total apoptotic rate from 5.78 ± 0.46% to 11.97 ± 1.61%, early apoptotic rate from 1.76 ± 0.22% to 5.50 ± 0.66%, and late apoptosis rate from 4.02 ± 0.25% to 6.47 ± 1.06% in adipose tissue-derived stromal cells. Furthermore, in circ-ATXN2-overexpressing cells, RT-PCR assay revealed that the expression levels of adipose differentiation-related genes PPARγ and CEBP/α were increased and the Oil Red O staining assay showed more lipid droplets. Our study revealed the expression profile of circRNAs in the adipose tissue of old rats. We found a novel age-related circular RNA—circ-ATXN2—that inhibits proliferation and promotes cell death and adipogenesis in rat adipose tissue-derived stromal cells.

Lysophosphatidic acid shifts metabolic and transcriptional landscapes to induce a distinct cellular state in human pluripotent stem cells

Pluripotent stem cells (PSCs) can be maintained in a continuum of cellular states with distinct features. Exogenous lipid supplements can relieve the dependence on de novo lipogenesis and shift global metabolism. However, it is largely unexplored how specific lipid components regulate metabolism and subsequently the pluripotency state. In this study, we report that the metabolic landscape of human PSCs (hPSCs) is shifted by signaling lipid lysophosphatidic acid (LPA), which naturally exists. LPA leads to a distinctive transcriptome profile that is not associated with de novo lipogenesis. Although exogenous lipids such as cholesterol, common free fatty acids, and LPA can affect cellular metabolism, they are not necessary for maintaining primed pluripotency. Instead, LPA induces distinct and reversible phenotypes in cell cycle, morphology, and mitochondria. This study reveals a distinct primed state that could be used to alter cell physiology in hPSCs for basic research and stem cell applications.

T-Cell Factors as Transcriptional Inhibitors: Activities and Regulations in Vertebrate Head Development

Since its first discovery in the late 90s, Wnt canonical signaling has been demonstrated to affect a large variety of neural developmental processes, including, but not limited to, embryonic axis formation, neural proliferation, fate determination, and maintenance of neural stem cells. For decades, studies have focused on the mechanisms controlling the activity of β-catenin, the sole mediator of Wnt transcriptional response. More recently, the spotlight of research is directed towards the last cascade component, the T-cell factor (TCF)/Lymphoid-Enhancer binding Factor (LEF), and more specifically, the TCF/LEF-mediated switch from transcriptional activation to repression, which in both embryonic blastomeres and mouse embryonic stem cells pushes the balance from pluri/multipotency towards differentiation. It has been long known that Groucho/Transducin-Like Enhancer of split (Gro/TLE) is the main co-repressor partner of TCF/LEF. More recently, other TCF/LEF-interacting partners have been identified, including the pro-neural BarH-Like 2 (BARHL2), which belongs to the evolutionary highly conserved family of homeodomain-containing transcription factors. This review describes the activities and regulatory modes of TCF/LEF as transcriptional repressors, with a specific focus on the functions of Barhl2 in vertebrate brain development. Specific attention is given to the transcriptional events leading to formation of the Organizer, as well as the roles and regulations of Wnt/β-catenin pathway in growth of the caudal forebrain. We present TCF/LEF activities in both embryonic and neural stem cells and discuss how alterations of this pathway could lead to tumors.

KLF17 promotes human naïve pluripotency but is not required for its establishment

Current knowledge of the transcriptional regulation of human pluripotency is incomplete, with lack of interspecies conservation observed. Single-cell transcriptomics analysis of human embryos previously enabled us to identify transcription factors, including the zinc-finger protein KLF17, that are enriched in the human epiblast and naïve human embryonic stem cells (hESCs). Here, we show that KLF17 is expressed coincident with the known pluripotency-associated factors NANOG and SOX2 across human blastocyst development. We investigate the function of KLF17 using primed and naïve hESCs for gain- and loss-of-function analyses. We find that ectopic expression of KLF17 in primed hESCs is sufficient to induce a naïve-like transcriptome and that KLF17 can drive transgene-mediated resetting to naïve pluripotency. This implies a role for KLF17 in establishing naïve pluripotency. However, CRISPR-Cas9-mediated knockout studies reveal that KLF17 is not required for naïve pluripotency acquisition in vitro. Transcriptome analysis of naïve hESCs identifies subtle effects on metabolism and signalling pathways following KLF17 loss of function, and possible redundancy with other KLF paralogues. Overall, we show that KLF17 is sufficient, but not necessary, for naïve pluripotency under the given in vitro conditions.

Summary: Given that KLF17 was shown to be sufficient, but not necessary, to establish naïve pluripotent hESCs, KLF17 might function as a peripheral regulator of human pluripotent stem cells.

Inhibition of ubiquitin-specific protease 13-mediated degradation of Raf1 kinase by Spautin-1 has opposing effects in naïve and primed pluripotent stem cells

Embryonic stem cells (ESCs) are progenitor cells that retain the ability to differentiate into various cell types and are necessary for tissue repair. Improving cell culture conditions to maintain the pluripotency of ESCs in vitro is an urgent problem in the field of regenerative medicine. Here, we reveal that Spautin-1, a specific small-molecule inhibitor of ubiquitin-specific protease (USP) family members USP10 and USP13, promotes the maintenance of self-renewal and pluripotency of mouse ESCs in vitro. Functional studies reveal that only knockdown of USP13, but not USP10, is capable of mimicking the function of Spautin-1. Mechanistically, we demonstrate that USP13 physically interacts with, deubiquitinates, and stabilizes serine/threonine kinase Raf1 and thereby sustains Raf1 protein at the posttranslational level to activate the FGF/MEK/ERK prodifferentiation signaling pathway in naïve mouse ESCs. In contrast, in primed mouse epiblast stem cells and human induced pluripotent stem cells, the addition of Spautin-1 had an inhibitory effect on Raf1 levels, but USP13 overexpression promoted self-renewal. The addition of an MEK inhibitor impaired the effect of USP13 upregulation in these cells. These findings provide new insights into the regulatory network of naïve and primed pluripotency.

A small molecule modulating monounsaturated fatty acids and Wnt signaling confers maintenance to induced pluripotent stem cells against endodermal differentiation

Background

Stearoyl-coenzyme A desaturase 1 (SCD1) is required for de novo synthesis of fatty acids. Through the fatty acid acylation process, this enzyme orchestrates post-translational modifications to proteins involved in cell development and differentiation. In this study, we used biochemical methods, immunostaining, and covalent labeling to evaluate whether a small molecule modulating unsaturated fatty acids can influence the early endodermal differentiation of human-induced pluripotent stem cells (iPSCs).

Methods

The hiPSCs were cultured in an endoderm-inducing medium containing activin A and defined fetal bovine serum in the presence of an SCD1 inhibitor at different time points. The cell cycles and the yields of the three germ layers (endoderm, mesoderm, and ectoderm) were assessed using flow cytometry. The expression of endoderm and pluripotency markers and the expressions of Wnt signaling pathway proteins were assessed using western blotting and RT-PCR. Total protein acylation was evaluated using a click chemistry reaction.

Results

When SCD1 was inhibited on the first day, the population of cells with endodermal features decreased at the end of differentiation. Moreover, early SCD1 inhibition preserved the properties of hiPSCs, preventing their shift toward mesodermal or ectodermal lineage. Also, first-day-only treatment of cells with the SCD1 inhibitor decreased β-catenin gene expression and the intensity of fluorescent emission in the click chemistry assay. The cells were effectively rescued from these effects by cotreatment with oleate. Late treatment with the inhibitor in the two subsequent days of endoderm induction did not have any significant effects on endoderm-specific markers or fluorescent intensity. Reproducible results were also obtained with human embryonic stem cells.

Conclusion

The small molecule SCD1 inhibitor attenuates the Wnt/β-catenin signaling pathway, conferring the maintenance of hiPSCs by opposing the initiation of endoderm differentiation. The immediate requirement for SCD1 activity in the endoderm commitment of pluripotent stem cells may be of importance in disorders of endoderm-derived organs and dysregulated metabolism.

The schematic representation of the study design and main results. Activin A induces endoderm features through Smad2/3/4 and increases the expression of SCD1. SCD1 can produce MUFAs and subsequently modify the Wnt molecules. MUFA acylated/activated Wnts are secreted to interact with corresponding receptors on the target cells. β-catenin accumulates in the cytoplasm and is translocated into the nucleus after the interaction of Wnt with the receptor. Then, β-catenin increases the expression of the endoderm markers Sox17 and CXCR4.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02617-x.