Embryo-derived stem cells: of mice and men

Bioengineering strategies for regeneration of skin integrity: A literature review

Objective

The skin is a complex organ that includes various stem cell populations. Current approaches for non-healing skin defects are sometimes inadequate and many attempts have been made to regenerate skin integrity. The aim of this review is to bridge the gap between basic research and clinical application of skin integrity regeneration.

Methods

A literature search was carried out in PubMed using combinations of the keywords "skin integrity", "tissue-engineered skin", "bioengineered skin", and "skin regeneration". Articles published from 1968 to 2023 reporting evidence from in vivo and in vitro skin regeneration experiments were included.

Results

These articles showed that stem cells can be differentiated into normal skin cells, including keratinocytes, and are a significant source of skin organoids, which are useful for investigating skin biology; and that emerging direct reprogramming methods have great potential to regenerate skin from the wounded skin surface.

Conclusion

Recent advances in skin regeneration will facilitate further advancement of both basic and clinical research in skin biology.

Intra-Arterial Stem Cell Injection for Treating Various Diseases: A New Frontier in Interventional Radiology

This article provides radiologists with insights into stem cells' functions, sources, and potentially successful clinical treatments via intravascular injection in organs such as the liver, kidney, pancreas, musculoskeletal system, and for ischemic conditions affecting the brain, heart and limbs. Understanding stem cells' significance in interventional radiology and its limitations enables tailored interventions for diverse conditions, ensuring efficient medical care and optimal treatment selection.

Propagating pluripotency - The conundrum of self-renewal

The discovery of mouse embryonic stem cells in 1981 transformed research in mammalian developmental biology and functional genomics. The subsequent generation of human pluripotent stem cells (PSCs) and the development of molecular reprogramming have opened unheralded avenues for drug discovery and cell replacement therapy. Here, I review the history of PSCs from the perspective that long-term self-renewal is a product of the in vitro signaling environment, rather than an intrinsic feature of embryos. I discuss the relationship between pluripotent states captured in vitro to stages of epiblast in the embryo and suggest key considerations for evaluation of PSCs. A remaining fundamental challenge is to determine whether naïve pluripotency can be propagated from the broad range of mammals by exploiting common principles in gene regulatory architecture.

Proteomic and functional comparison between human induced and embryonic stem cells

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

Advancing stem cell technologies for conservation of wildlife biodiversity

Wildlife biodiversity is essential for healthy, resilient and sustainable ecosystems. For biologists, this diversity also represents a treasure trove of genetic, molecular and developmental mechanisms that deepen our understanding of the origins and rules of life. However, the rapid decline in biodiversity reported recently foreshadows a potentially catastrophic collapse of many important ecosystems and the associated irreversible loss of many forms of life on our planet. Immediate action by conservationists of all stripes is required to avert this disaster. In this Spotlight, we draw together insights and proposals discussed at a recent workshop hosted by Revive & Restore, which gathered experts to discuss how stem cell technologies can support traditional conservation techniques and help protect animal biodiversity. We discuss reprogramming, in vitro gametogenesis, disease modelling and embryo modelling, and we highlight the prospects for leveraging stem cell technologies beyond mammalian species.

Boric acid supplementation promotes the development of in vitro-produced mouse embryos by related pluripotent and antioxidant genes

Boric acid (BA) is an important mineral for plants, animals and humans that assists metabolic function and has both positive and negative effects on biological systems. The present study aimed to investigate the effects of different concentrations of BA added to the culture media, the quality and in vitro development potential of mouse embryos. Superovulated C57Bl6/6j female mice were sacrificed ∼18 hours after human chorionic gonadotropin (hCG) injection. Single-cell-stage embryos were collected from the oviduct, divided into experiment groups and cultured in embryo medium with supplemented BA+ in 5% CO2 at 37 °C until 96 hours at the blastocyst stage. The blastocyst development rates of 0, 1.62 × 10-1, 1.62 × 10-2, 1.62 × 10-3 and 1.62 × 10-4 µM BA were 51.52%, 73.47%, 77.36% and 81.13%, respectively. The in vitro development rates were significantly higher in the 1.62 × 10-3 (p < 0.05) and 1.62 × 10-4 µM BA groups than in the control group (p < 0.001). These results indicated that low BA doses influenced embryo development by positively affecting in vitro development rates, embryo cell numbers, biochemical parameters and development at the molecular level by pluripotent and antioxidant genes. Therefore, BA seems to play an important role on in vitro embryo development.

The codon optimised gene produces an active human basic fibroblastic growth factor in rice cell suspension culture

The coding sequence of human basic fibroblast growth factor (hbFGF) was optimised for expression in rice. An expression cassette was constructed by fusing the PCR-amplified RAmy3D promoter, along with its 5'UTR, 3'UTR, and terminator sequences, to the codon-optimised hbFGF sequence. This cassette was inserted into the pCAMBIA1304 shuttle vector, which also contained the RAmy3D signal peptide. Agrobacterium tumefaciens strain LBA 4404 was used to transform rice callus. Among the transformed lines, the callus expressing the highest level of bFGF (38.1 mg/kg fresh weight) was identified via ELISA and selected for establishing a cell suspension culture. Expression and secretion of the recombinant bFGF into the culture medium were observed three days after incubating the transgenic rice cells in sucrose-free medium. The presence of recombinant bFGF was confirmed through Western blot and SDS-PAGE analyses. Furthermore, the rice-derived bFGF effectively stimulated the proliferation of NIH/3T3 cells, demonstrating a comparable biological activity to that of commercial bFGF.

A novel chemical genetic approach reveals paralog-specific role of ERK1/2 in mouse embryonic stem cell fate control

Introduction: Mouse embryonic stem cell (ESC) self-renewal can be maintained through dual inhibition of GSK3 and MEK kinases. MEK has two highly homologous downstream kinases, extracellular signal-regulated kinase 1 and 2 (ERK1/2). However, the exact roles of ERK1/2 in mouse ESC self-renewal and differentiation remain unclear. Methods: We selectively deleted or inhibited ERK1, ERK2, or both using genetic and chemical genetic approaches combined with small molecule inhibitors. The effects of ERK paralog-specific inhibition on mouse ESC self-renewal and differentiation were then assessed. Results: ERK1/2 were found to be dispensable for mouse ESC survival and self-renewal. The inhibition of both ERK paralogs, in conjunction with GSK3 inhibition, was sufficient to maintain mouse ESC self-renewal. In contrast, selective deletion or inhibition of only one ERK paralog did not mimic the effect of MEK inhibition in promoting mouse ESC self-renewal. Regarding ESC differentiation, inhibition of ERK1/2 prevented mesendoderm differentiation. Additionally, selective inhibition of ERK1, but not ERK2, promoted mesendoderm differentiation. Discussion: These findings suggest that ERK1 and ERK2 have both overlapping and distinct roles in regulating ESC self-renewal and differentiation. This study provides new insights into the molecular mechanisms of ERK1/2 in governing ESC maintenance and lineage commitment, potentially informing future strategies for controlling stem cell fate in research and therapeutic applications.

Role of small molecules as drug candidates for reprogramming somatic cells into induced pluripotent stem cells: A comprehensive review

With the use of specific genetic factors and recent developments in cellular reprogramming, it is now possible to generate lineage-committed cells or induced pluripotent stem cells (iPSCs) from readily available and common somatic cell types. However, there are still significant doubts regarding the safety and effectiveness of the current genetic methods for reprogramming cells, as well as the conventional culture methods for maintaining stem cells. Small molecules that target specific epigenetic processes, signaling pathways, and other cellular processes can be used as a complementary approach to manipulate cell fate to achieve a desired objective. It has been discovered that a growing number of small molecules can support lineage differentiation, maintain stem cell self-renewal potential, and facilitate reprogramming by either increasing the efficiency of reprogramming or acting as a genetic reprogramming factor substitute. However, ongoing challenges include improving reprogramming efficiency, ensuring the safety of small molecules, and addressing issues with incomplete epigenetic resetting. Small molecule iPSCs have significant clinical applications in regenerative medicine and personalized therapies. This review emphasizes the versatility and potential safety benefits of small molecules in overcoming challenges associated with the iPSCs reprogramming process.

Malat1 affects transcription and splicing through distinct pathways in mouse embryonic stem cells

Malat1 is a long-noncoding RNA with critical roles in gene regulation and cancer metastasis, however its functional role in stem cells is largely unexplored. We here perform a nuclear knockdown of Malat1 in mouse embryonic stem cells, causing the de-regulation of 320 genes and aberrant splicing of 90 transcripts, some of which potentially affecting the translated protein sequence. We find evidence that Malat1 directly interacts with gene bodies and aberrantly spliced transcripts, and that it locates upstream of down-regulated genes at their putative enhancer regions, in agreement with functional genomics data. Consistent with this, we find these genes affected at both exon and intron levels, suggesting that they are transcriptionally regulated by Malat1. Besides, the down-regulated genes are regulated by specific transcription factors and bear both activating and repressive chromatin marks, suggesting that some of them might be regulated by bivalent promoters. We propose a model in which Malat1 facilitates the transcription of genes involved in chromatid dynamics and mitosis in one pathway, and affects the splicing of transcripts that are themselves involved in RNA processing in a distinct pathway. Lastly, we compare our findings with Malat1 perturbation studies performed in other cell systems and in vivo.

γH2AX in mouse embryonic stem cells: Distribution during differentiation and following γ-irradiation

Phosphorylated histone H2AX (γH2AX) represents a sensitive molecular marker of DNA double-strand breaks (DSBs) and is implicated in stem cell biology. We established a model of mouse embryonic stem cell (mESC) differentiation and examined the dynamics of γH2AX foci during the process. Our results revealed high numbers of γH2AX foci in undifferentiated mESCs, decreasing as the cells differentiated towards the endothelial cell lineage. Notably, we observed two distinct patterns of γH2AX foci: the typical discrete γH2AX foci, which colocalize with the transcriptionally permissive chromatin mark H3K4me3, and the less well-characterized clustered γH2AX regions, which were only observed in intermediate progenitor cells. Next, we explored responses of mESCs to γ-radiation (137Cs). Following exposure to γ-radiation, mESCs showed a reduction in cell viability and increased γH2AX foci, indicative of radiosensitivity. Despite irradiation, surviving mESCs retained their differentiation potential. To further exemplify our findings, we investigated neural stem progenitor cells (NSPCs). Similar to mESCs, NSPCs displayed clustered γH2AX foci associated with progenitor cells and discrete γH2AX foci indicative of embryonic stem cells or differentiated cells. In conclusion, our findings demonstrate that γH2AX serves as a versatile marker of DSBs and may have a role as a biomarker in stem cell differentiation. The distinct patterns of γH2AX foci in differentiating mESCs and NSPCs provide valuable insights into DNA repair dynamics during differentiation, shedding light on the intricate balance between genomic integrity and cellular plasticity in stem cells. Finally, the clustered γH2AX foci observed in intermediate progenitor cells is an intriguing feature, requiring further exploration.

Stem cells as a regenerative medicine approach in treatment of microvascular diabetic complications

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by high blood glucose and is associated with high morbidity and mortality among the diabetic population. Uncontrolled chronic hyperglycaemia causes increased formation and accumulation of different oxidative and nitrosative stress markers, resulting in microvascular and macrovascular complications, which might seriously affect the quality of a patient's life. Conventional treatment strategies are confined to controlling blood glucose by regulating the insulin level and are not involved in attenuating the life-threatening complications of diabetes mellitus. Thus, there is an unmet need to develop a viable treatment strategy that could target the multi-etiological factors involved in the pathogenesis of diabetic complications. Stem cell therapy, a regenerative medicine approach, has been investigated in diabetic complications owing to their unique characteristic features of self-renewal, multilineage differentiation and regeneration potential. The present review is focused on potential therapeutic applications of stem cells in the treatment of microvascular diabetic complications such as nephropathy, retinopathy, and polyneuropathy.

Embryonic stem cell-derived extracellular vesicles rejuvenate senescent cells and antagonize aging in mice

Aging is a degenerative process that leads to tissue dysfunction and death. Embryonic stem cells (ESCs) have great therapeutic potential for age-related diseases due to their capacity for self-renewal and plasticity. However, the use of ESCs in clinical treatment is limited by immune rejection, tumourigenicity and ethical issues. ESC-derived extracellular vesicles (EVs) may provide therapeutic effects that are comparable to those of ESCs while avoiding unwanted effects. Here, we fully evaluate the role of ESC-EVs in rejuvenation in vitro and in vivo. Using RNA sequencing (RNA-Seq) and microRNA sequencing (miRNA-Seq) screening, we found that miR-15b-5p and miR-290a-5p were highly enriched in ESC-EVs, and induced rejuvenation by silencing the Ccn2-mediated AKT/mTOR pathway. These results demonstrate that miR-15b-5p and miR-290a-5p function as potent activators of rejuvenation mediated by ESC-EVs. The rejuvenating effect of ESC-EVs was further investigated in vivo by injection into aged mice. The results showed that ESC-EVs successfully ameliorated the pathological age-related phenotypes and rescued the transcriptome profile of aged mice. Our findings demonstrate that ESC-EVs treatment can rejuvenate senescence both in vitro and in vivo and suggest the therapeutic potential of ESC-EVs as a novel cell-free alternative to ESCs for age-related diseases.

Metabolic switches during development and regeneration

Metabolic switches are a crucial hallmark of cellular development and regeneration. In response to changes in their environment or physiological state, cells undergo coordinated metabolic switching that is necessary to execute biosynthetic demands of growth and repair. In this Review, we discuss how metabolic switches represent an evolutionarily conserved mechanism that orchestrates tissue development and regeneration, allowing cells to adapt rapidly to changing conditions during development and postnatally. We further explore the dynamic interplay between metabolism and how it is not only an output, but also a driver of cellular functions, such as cell proliferation and maturation. Finally, we underscore the epigenetic and cellular mechanisms by which metabolic switches mediate biosynthetic needs during development and regeneration, and how understanding these mechanisms is important for advancing our knowledge of tissue development and devising new strategies to promote tissue regeneration.

Engineered and banked iPSCs for advanced NK- and T-cell immunotherapies

The development of methods to derive induced pluripotent stem cells (iPSCs) has propelled stem cell research, and has the potential to revolutionize many areas of medicine, including cancer immunotherapy. These cells can be propagated limitlessly and can differentiate into nearly any specialized cell type. The ability to perform precise multigene engineering at the iPSC stage, generate master cell lines after clonal selection, and faithfully promote differentiation along natural killer (NK) cells and T-cell lineages is now leading to new opportunities for the administration of off-the-shelf cytotoxic lymphocytes with direct antigen targeting to treat patients with relapsed/refractory cancer. In this review, we highlight the recent progress in iPSC editing and guided differentiation in the development of NK- and T-cell products for immunotherapy. We also discuss some of the potential barriers that remain in unleashing the full potential of iPSC-derived cytotoxic effector cells in the adoptive transfer setting, and how some of these limitations may be overcome through gene editing.

Attempts for deriving extended pluripotent stem cells from common marmoset embryonic stem cells

Extended pluripotent stem cells (EPSCs) derived from mice and humans showed an enhanced potential for chimeric formation. By exploiting transcriptomic approaches, we assessed the differences in gene expression profile between extended EPSCs derived from mice and humans, and those newly derived from the common marmoset (marmoset; Callithrix jacchus). Although the marmoset EPSC-like cells displayed a unique colony morphology distinct from murine and human EPSCs, they displayed a pluripotent state akin to embryonic stem cells (ESCs), as confirmed by gene expression and immunocytochemical analyses of pluripotency markers and three-germ-layer differentiation assay. Importantly, the marmoset EPSC-like cells showed interspecies chimeric contribution to mouse embryos, such as E6.5 blastocysts in vitro and E6.5 epiblasts in vivo in mouse development. Also, we discovered that the perturbation of gene expression of the marmoset EPSC-like cells from the original ESCs resembled that of human EPSCs. Taken together, our multiple analyses evaluated the efficacy of the method for the derivation of marmoset EPSCs.

State of the Art and Future of Stem Cell Therapy in Ischemic Stroke: Why Don't We Focus on Their Administration?

Stroke is one of the leading causes of death and disability worldwide, so there is an urgent need to find a therapy for the tragic outcomes of this cerebrovascular disease. Stem cells appeared to be a good solution for many conditions, so different experiments were made to establish stem cells as a feasible therapy for stroke. The aim of this review is to analyze the state of the art of stem cell therapy for stroke and if the route of administration could represent a valid adjusting point for ameliorating the therapy's outcome. To obtain this, we searched the scientific literature of the last 10 years for relevant in vitro and in vivo evidence regarding stem cells' potential in stroke therapy. In vitro evidence points to hypoxia, among the preconditioning strategies, as the most used and probably efficient method to enhance cells qualities, while in vivo results raise the question if it is the type of cells or how they are administrated which can make the difference in terms of efficiency. Unfortunately, despite the number of clinical trials, only a few were successfully concluded, demonstrating how urgent the necessity is to translate pre-clinical results into clinics. Since any type of stem cell seems suitable for therapy, the chosen route of administration corresponds to different engraftment rates, distribution and efficiency in terms of the beneficial effects of stem cells. Intravenous administration was widely used for delivering stem cells into the human body, but recently intranasal administration has given promising results in vivo. It allows stem cells to efficiently reach the brain that was precluded to intravenous administration, so it is worth further investigation.

Production of large, defined genome modifications in rats by targeting rat embryonic stem cells

Rats were more frequently used than mice to model human disease before mouse embryonic stem cells (mESCs) revolutionized genetic engineering in mice. Rat ESCs (rESCs) were first reported over 10 years ago, yet they are not as frequently used as mESCs. CRISPR-based gene editing in zygotes is widely used in rats but is limited by the difficulty of inserting or replacing DNA sequences larger than about 10 kb. We report here the generation of germline-competent rESC lines from several rat strains. These rESC lines maintain their potential for germline transmission after serial targeting with bacterial artificial chromosome (BAC)-based targeting vectors, and CRISPR-Cas9 cutting can increase targeting efficiency. Using these methods, we have successfully replaced entire rat genes spanning up to 101 kb with the human ortholog.

Stem Cells as Nuclear Donors for Mammalian Cloning

Mammals are routinely cloned by introducing somatic nuclei into enucleated oocytes. Cloning contributes to propagating desired animals, to germplasm conservation efforts, among other applications. A challenge to more broader use of this technology is the relatively low cloning efficiency, which inversely correlates with donor cell differentiation status. Emerging evidence suggests that adult multipotent stem cells improve cloning efficiency, while the greater potential of embryonic stem cells for cloning remains restricted to the mouse. The derivation of pluripotent or totipotent stem cells from livestock and wild species and their association with modulators of epigenetic marks in donor cells should increase cloning efficiency.

Current treatments after spinal cord injury: Cell engineering, tissue engineering, and combined therapies

Both traumatic and non-traumatic spinal cord injuries (SCIs) can be categorized as damages done to our central nervous system (CNS). The patients' physical and mental health may suffer greatly because of traumatic SCI. With the widespread use of motor vehicles and increasingly aged population, the occurrence of SCI is more frequent than before, creating a considerable burden to global public health. The regeneration process of the spinal cord is hampered by a series of events that occur following SCI like edema, hemorrhage, formation of cystic cavities, and ischemia. An effective strategy for the treatment of SCI and functional recovery still has not been discovered; however, recent advances have been made in bioengineering fields that therapies based on cells, biomaterials, and biomolecules have proved effective in the repair of the spinal cord. In the light of worldwide importance of treatments for SCI, this article aims to provide a review of recent advances by first introducing the physiology, etiology, epidemiology, and mechanisms of SCI. We then put emphasis on the widely used clinical treatments and bioengineering strategies (cell-based, biomaterial-based, and biomolecule-based) for the functional regeneration of the spinal cord as well as challenges faced by scientists currently. This article provides scientists and clinicians with a comprehensive outlook on the recent advances of preclinical and clinical treatments of SCI, hoping to help them find keys to the functional regeneration of SCI.

Cost-efficient boundary-free surface patterning achieves high effective-throughput of time-lapse microscopy experiments

Time-lapse microscopy plays critical roles in the studies of cellular dynamics. However, setting up a time-lapse movie experiments is not only laborious but also with low output, mainly due to the cell-losing problem (i.e., cells moving out of limited field of view), especially in a long-time recording. To overcome this issue, we have designed a cost-efficient way that enables cell patterning on the imaging surfaces without any physical boundaries. Using mouse embryonic stem cells as an example system, we have demonstrated that our boundary-free patterned surface solves the cell-losing problem without disturbing their cellular phenotype. Statistically, the presented system increases the effective-throughput of time-lapse microscopy experiments by an order of magnitude.

Dynamic gelatin-based hydrogels promote the proliferation and self-renewal of embryonic stem cells in long-term 3D culture

Long-term maintenance of embryonic stem cells (ESCs) in the undifferentiated state is still challenging. Compared with traditional 2D culture methods, 3D culture in biomaterials such as hydrogels is expected to better support the long-term self-renewal of ESCs by emulating the biophysical and biochemical properties of the extracellular matrix (ECM). Although prior studies showed that soft and degradable hydrogels favor the 3D growth of ESCs, few studies have examined the impact of the structural dynamics of the hydrogel matrix on ESC behaviors. Herein, we report a gelatin-based structurally dynamic hydrogel (GelCD hydrogel) that emulates the intrinsic structural dynamics of the ECM. Compared with covalently crosslinked gelatin hydrogels (GelMA hydrogels) with similar stiffness and biodegradability, GelCD hydrogels significantly promote the clonal expansion and viability of encapsulated mouse ESCs (mESCs) independent of MMP-mediated hydrogel degradation. Furthermore, GelCD hydrogels better maintain the pluripotency of encapsulated mESCs than do traditional 2D culture methods that use MEF feeder cells or medium supplementation with GSK3β and MEK 1/2 inhibitors (2i). When cultured in GelCD hydrogels for an extended period (over 2 months) with cell passaging every 7 days, mESCs preserve their normal morphology and maintain their pluripotency and full differentiation capability. Our findings highlight the critical role of the structural dynamics of the hydrogel matrix in accommodating the volume expansion that occurs during clonal ESC growth, and we believe that our dynamic hydrogels represent a valuable tool to support the long-term 3D culture of ESCs.

Characterization of multitype colonies originating from porcine blastocysts produced in vitro

Many types of embryonic stem cells have been induced from pre-implantation blastocysts to study the specification of early lineages. Various cell lines have been established using chemicals, including excessive inhibitory molecules. Previous studies have also aimed to purify cell populations representing a single embryonic lineage from a protocol. In this study, we used a novel culture condition to induce cells from blastocyst seeding and analyzed their characteristics. Next, signaling inhibitors were introduced during the cell culture period. Furthermore, we investigated the cell types using RNA sequencing. Each type of cell population showed a distinct morphology and reactivity with alkaline phosphatase. Marker proteins enabled each cell type to be distinguished by immunocytochemistry, and genes such as Sox17, Gata4, Gata6, T, and Cdx2 showed applicability for the discrimination of cell types. Signaling inhibitors suppressed the production of some cell types, and gene expression and marker protein patterns were collapsed. RNA-sequencing suggested cell-type-specific marker genes and the correlation among samples. In conclusion, four types of cells could be induced from porcine embryos using a single protocol, and they could be isolated manually. Our data will help promote the study of lineage segregation based on embryonic cells.

Mechanotransduction through adhesion molecules: Emerging roles in regulating the stem cell niche

Stem cells have been shown to play an important role in regenerative medicine due to their proliferative and differentiation potential. The challenge, however, lies in regulating and controlling their potential for this purpose. Stem cells are regulated by growth factors as well as an array of biochemical and mechanical signals. While the role of biochemical signals and growth factors in regulating stem cell homeostasis is well explored, the role of mechanical signals has only just started to be investigated. Stem cells interact with their niche or to other stem cells via adhesion molecules that eventually transduce mechanical cues to maintain their homeostatic function. Here, we present a comprehensive review on our current understanding of the influence of the forces perceived by cell adhesion molecules on the regulation of stem cells. Additionally, we provide insights on how this deeper understanding of mechanobiology of stem cells has translated toward therapeutics.

Gastruloids: Pluripotent stem cell models of mammalian gastrulation and embryo engineering

Gastrulation is a fundamental and critical process of animal development whereby the mass of cells that results from the proliferation of the zygote transforms itself into a recognizable outline of an organism. The last few years have seen the emergence of a number of experimental models of early mammalian embryogenesis based on Embryonic Stem (ES) cells. One of this is the Gastruloid model. Gastruloids are aggregates of defined numbers of ES cells that, under defined culture conditions, undergo controlled proliferation, symmetry breaking, and the specification of all three germ layers characteristic of vertebrate embryos, and their derivatives. However, they lack brain structures and, surprisingly, reveal a disconnect between cell type specific gene expression and tissue morphogenesis, for example during somitogenesis. Gastruloids have been derived from mouse and human ES cells and several variations of the original model have emerged that reveal a hereto unknown modularity of mammalian embryos. We discuss the organization and development of gastruloids in the context of the embryonic stages that they represent, pointing out similarities and differences between the two. We also point out their potential as a reproducible, scalable and searchable experimental system and highlight some questions posed by the current menagerie of gastruloids.

Optimized Method for Using Embryonic Microenvironment to Reprogram Cancer Stem Cells

Purpose: The embryonic microenvironment contains many properties that have not yet been fully explored. Our aim in this study is to report an optimized and efficient method that enables investigating the effects of the secretome of pluripotent embryonic stem cells on cancer stem cells. Methods: The study is performed with a chimeric model consisted of mouse blastocysts, human prostate cancer stem cells and non-cancer stem cells. Ovulation induced mice were used for blastocyst collection. DU145 prostate cancer cell line was separated into cancer stem cells and non-cancer stem cells according to cancer stem cells biomarker expressions by fluorescent activated cell sorting method. Human prostate cancer stem cells and non-cancer stem cells were microinjected into 4-day blastocyst culture in vitro by intracytoplasmic sperm injection method. Results: Chimeric models provide us great convenience in basic oncological studies. In this study, using a chimeric model, we were able to study the secretome of mouse embryonic stem cells and their effect on cancer stem cells. The method is efficient and yield promising result; and could be used to study the effects on other cells as well. Conclusion: The embryonic stem cell microenvironment is suggested to have a great regenerative capacity which is, nowadays, the center of attraction for cancer research studies. Ethical issues restrict the human embryo studies, however, mimicking the in vivo human microenvironment with 3D cell cultures or bioprinting are now possible. Finally, optimization of new methods including 3D cell cultures with human cell lines will be a great opportunity for better understanding the reprogramming notion.

The context-dependent, combinatorial logic of BMP signaling

Cell-cell communication systems typically comprise families of ligand and receptor variants that function together in combinations. Pathway activation depends on the complex way in which ligands are presented extracellularly and receptors are expressed by the signal-receiving cell. To understand the combinatorial logic of such a system, we systematically measured pairwise bone morphogenetic protein (BMP) ligand interactions in cells with varying receptor expression. Ligands could be classified into equivalence groups based on their profile of positive and negative synergies with other ligands. These groups varied with receptor expression, explaining how ligands can functionally replace each other in one context but not another. Context-dependent combinatorial interactions could be explained by a biochemical model based on the competitive formation of alternative signaling complexes with distinct activities. Together, these results provide insights into the roles of BMP combinations in developmental and therapeutic contexts and establish a framework for analyzing other combinatorial, context-dependent signaling systems.

Stem Cell Transplantation Therapy and Neurological Disorders: Current Status and Future Perspectives

Neurodegenerative diseases are a global health issue with inadequate therapeutic options and an inability to restore the damaged nervous system. With advances in technology, health scientists continue to identify new approaches to the treatment of neurodegenerative diseases. Lost or injured neurons and glial cells can lead to the development of several neurological diseases, including Parkinson's disease, stroke, and multiple sclerosis. In recent years, neurons and glial cells have successfully been generated from stem cells in the laboratory utilizing cell culture technologies, fueling efforts to develop stem cell-based transplantation therapies for human patients. When a stem cell divides, each new cell has the potential to either remain a stem cell or differentiate into a germ cell with specialized characteristics, such as muscle cells, red blood cells, or brain cells. Although several obstacles remain before stem cells can be used for clinical applications, including some potential disadvantages that must be overcome, this cellular development represents a potential pathway through which patients may eventually achieve the ability to live more normal lives. In this review, we summarize the stem cell-based therapies that have been explored for various neurological disorders, discuss the potential advantages and drawbacks of these therapies, and examine future directions for this field.

Immunomodulation of Skin Repair: Cell-Based Therapeutic Strategies for Skin Replacement (A Comprehensive Review)

The immune system has a crucial role in skin wound healing and the application of specific cell-laden immunomodulating biomaterials emerged as a possible treatment option to drive skin tissue regeneration. Cell-laden tissue-engineered skin substitutes have the ability to activate immune pathways, even in the absence of other immune-stimulating signals. In particular, mesenchymal stem cells with their immunomodulatory properties can create a specific immune microenvironment to reduce inflammation, scarring, and support skin regeneration. This review presents an overview of current wound care techniques including skin tissue engineering and biomaterials as a novel and promising approach. We highlight the plasticity and different roles of immune cells, in particular macrophages during various stages of skin wound healing. These aspects are pivotal to promote the regeneration of nonhealing wounds such as ulcers in diabetic patients. We believe that a better understanding of the intrinsic immunomodulatory features of stem cells in implantable skin substitutes will lead to new translational opportunities. This, in turn, will improve skin tissue engineering and regenerative medicine applications.

Application of Induced Pluripotent Stem Cells for Disease Modeling and 3D Model Construction: Focus on Osteoarthritis

Since their discovery in 2006, induced pluripotent stem cells (iPSCs) have shown promising potential, specifically because of their accessibility and plasticity. Hence, the clinical applicability of iPSCs was investigated in various fields of research. However, only a few iPSC studies pertaining to osteoarthritis (OA) have been performed so far, despite the high prevalence rate of degenerative joint disease. In this review, we discuss some of the most recent applications of iPSCs in disease modeling and the construction of 3D models in various fields, specifically focusing on osteoarthritis and OA-related conditions. Notably, we comprehensively reviewed the successful results of iPSC-derived disease models in recapitulating OA phenotypes for both OA and early-onset OA to encompass their broad etiology. Moreover, the latest publications with protocols that have used iPSCs to construct 3D models in recapitulating various conditions, particularly the OA environment, were further discussed. With the overall optimistic results seen in both fields, iPSCs are expected to be more widely used for OA disease modeling and 3D model construction, which could further expand OA drug screening, risk assessment, and therapeutic capabilities.

Regenerative Engineering: Current Applications and Future Perspectives

Many pathologies, congenital defects, and traumatic injuries are untreatable by conventional pharmacologic or surgical interventions. Regenerative engineering represents an ever-growing interdisciplinary field aimed at creating biological replacements for injured tissues and dysfunctional organs. The need for bioengineered replacement parts is ubiquitous among all surgical disciplines. However, to date, clinical translation has been limited to thin, small, and/or acellular structures. Development of thicker tissues continues to be limited by vascularization and other impediments. Nevertheless, currently available materials, methods, and technologies serve as robust platforms for more complex tissue fabrication in the future. This review article highlights the current methodologies, clinical achievements, tenacious barriers, and future perspectives of regenerative engineering.

A Modified SMART-Seq Method for Single-Cell Transcriptomic Analysis of Embryoid Body Differentiation

Embryoid bodies (EBs) are aggregate of cells that contain three embryonic germ layers. They can be formed by direct differentiation from pluripotent embryonic stem cells (ESCs), which serves as a useful model for understanding early embryo development. Due to the mixture of different cell types, it is necessary to investigate EBs at the single-cell level. Here, we describe a robust and straightforward method for single-cell gene expression profiling during mouse EB differentiation from mouse ESCs (mESCs). The protocol is modified from a widely used method in the SMART-seq family, which only requires standard molecular biology techniques and lab equipment. It allows for accurate 3' counting of transcript at the single-cell level, which helps reveal cellular identities during EB formation. Combined with perturbation experiments, the method provides an opportunity for mechanistic studies of embryo development at the single-cell level.

The Use of Stem Cell-Derived Organoids in Disease Modeling: An Update

Organoids represent one of the most important advancements in the field of stem cells during the past decade. They are three-dimensional in vitro culturing models that originate from self-organizing stem cells and can mimic the in vivo structural and functional specificities of body organs. Organoids have been established from multiple adult tissues as well as pluripotent stem cells and have recently become a powerful tool for studying development and diseases in vitro, drug screening, and host-microbe interaction. The use of stem cells-that have self-renewal capacity to proliferate and differentiate into specialized cell types-for organoids culturing represents a major advancement in biomedical research. Indeed, this new technology has a great potential to be used in a multitude of fields, including cancer research, hereditary and infectious diseases. Nevertheless, organoid culturing is still rife with many challenges, not limited to being costly and time consuming, having variable rates of efficiency in generation and maintenance, genetic stability, and clinical applications. In this review, we aim to provide a synopsis of pluripotent stem cell-derived organoids and their use for disease modeling and other clinical applications.

Continuous expression of reprogramming factors induces and maintains mouse pluripotency without specific growth factors and signaling inhibitors

Objectives

Derivation and maintenance of pluripotent stem cells (PSCs) generally require optimized and complex culture media, which hinders the derivation of PSCs from various species. Expression of Oct4, Sox2, Klf4, and c‐Myc (OSKM) can reprogram somatic cells into induced PSCs (iPSCs), even for species possessing no optimal culture condition. Herein, we explored whether expression of OSKM could induce and maintain pluripotency without PSC‐specific growth factors and signaling inhibitors.

Methods

The culture medium of Tet‐On‐OSKM/Oct4‐GFP mouse embryonic stem cells (ESCs) was switched from N2B27 with MEK inhibitor, GSK3β inhibitor, and leukemia inhibitory factor (LIF) (2iL) to N2B27 with doxycycline. Tet‐On‐OSKM mouse embryonic fibroblast (MEF) cells were reprogrammed in N2B27 with doxycycline. Cell proliferation was traced. Pluripotency was assessed by expression of ESC marker genes, teratoma, and chimera formation. RNA‐Seq was conducted to analyze gene expression.

Results

Via continuous expression of OSKM, mouse ESCs (OSKM‐ESCs) and the resulting iPSCs (OSKM‐iPSCs) reprogrammed from MEF cells propagated stably, expressed pluripotency marker genes, and formed three germ layers in teratomas. Transcriptional landscapes of OSKM‐iPSCs resembled those of ESCs cultured in 2iL and were more similar to those of ESCs cultured in serum/LIF. Furthermore, OSKM‐iPSCs contributed to germline transmission.

Conclusions

Expression of OSKM could induce and maintain mouse pluripotency without specific culturing factors. Importantly, OSKM‐iPSCs could produce gene‐modified animals through germline transmission, with potential applications in other species.

Effects of vitamin A and retinoic acid on mouse embryonic stem cells and their differentiating progeny

Embryonic development is controlled by retinoids, and one approach that has been used to investigate the mechanisms for retinoid actions in developmental processes has been to study the effects of adding retinoids to cultures of pluripotent embryonic stem cells (ESC). To date, most in vitro retinoid research has been directed at deciphering the actions of all-trans retinoic acid (atRA). atRA is a derivative of all-trans retinol (a.k.a. vitamin A, VA), which mammals can generate via an enzyme-catalyzed pathway. atRA's effects on development result from its (1) activation of receptor complexes (RARs and RXRs) in the nucleus which then bind to and activate RA response elements (RAREs) in genes and (2) its interactions with processes that are initiated in the cytoplasm. While much work has focused on the impact of atRA on cell differentiation, VA, itself, has been shown to exert effects on the maintenance of ESC identity that are not dependent upon classic RA-signaling pathways. In this chapter, we present results from our laboratory and others using well-documented approaches for investigating the effects of retinoids on the differentiation of ESC in vitro and introduce a novel method that uses chemically-defined growth conditions. The merits of each approach are discussed.

Layer-Number-Dependent Effects of Graphene Oxide on the Pluripotency of Mouse Embryonic Stem Cells Through the Regulation of the Interaction Between the Extracellular Matrix and Integrins

Introduction

Embryonic stem cells (ESCs) possess great application prospects in biological research and regenerative medicine, so it is important to obtain ESCs with excellent and stable cellular states during in vitro expansion. The feeder layer culture system with the addition of leukemia inhibitory factor (LIF) is currently applied in ESC cultures, but it has a series of disadvantages that could influence the culture efficiency and quality of the ESCs. With the development of nanotechnology, many studies have applied nanomaterials to optimize the stem cell culture system and regulate the fate of stem cells. In this study, we investigated the layer-number-dependent biofunction of graphene oxide (GO) on the pluripotency of ESCs from mice (mESCs).

Methods

Single-layer GO (SGO) and multi-layer GO (MGO) were characterized and their effects on the cytotoxicity and self-renewal of mESCs were detected in vitro. The differentiation potentials of mESCs were identified through the formation of embryoid bodies and teratomas. The regulatory mechanism of GO was verified by blocking the target receptors on the surface of mESCs using antibodies.

Results

Both SGO and MGO were biocompatible with mESCs, but only MGO effectively sustained their self-renewal and differentiation potential. In addition, GO influenced the cellular activities of mESCs by regulating the interactions between extracellular matrix proteins and integrins.

Conclusion

This work demonstrates the layer-number-dependent effects of GO on regulating the cell behavior of mESCs and reveals the extracellular regulatory mechanism of this process.

Regenerative Medicine Approaches in Bioengineering Female Reproductive Tissues

Diseases, disorders, and dysfunctions of the female reproductive tract tissues can result in either infertility and/or hormonal imbalance. Current treatment options are limited and often do not result in tissue function restoration, requiring alternative therapeutic approaches. Regenerative medicine offers potential new therapies through the bioengineering of female reproductive tissues. This review focuses on some of the current technologies that could address the restoration of functional female reproductive tissues, including the use of stem cells, biomaterial scaffolds, bio-printing, and bio-fabrication of tissues or organoids. The use of these approaches could also be used to address issues in infertility. Strategies such as cell-based hormone replacement therapy could provide a more natural means of restoring normal ovarian physiology. Engineering of reproductive tissues and organs could serve as a powerful tool for correcting developmental anomalies. Organ-on-a-chip technologies could be used to perform drug screening for personalized medicine approaches and scientific investigations of the complex physiological interactions between the female reproductive tissues and other organ systems. While some of these technologies have already been developed, others have not been translated for clinical application. The continuous evolution of biomaterials and techniques, advances in bioprinting, along with emerging ideas for new approaches, shows a promising future for treating female reproductive tract-related disorders and dysfunctions.

Pluripotent and Multipotent Stem Cells and Current Therapeutic Applications: Review

There is numerous evidence for the presence of stem cells, which is important for the treatment of a wide variety of disease conditions. Stem cells have a great therapeutic effect on different degenerative diseases through the development of specialized cells. Embryonic stem (ES) cells are derived from preimplantation embryos, which have a natural karyotype. This cell has the capacity of proliferation indefinitely and undifferentiated. Stem cells are very crucial for the treatment of different chronic and degenerative diseases. For instance, stem cell clinical trials have been done for ischemic heart disease. Also, the olfactory cells for spinal cord lesions and human fetal pancreatic cells for diabetes mellitus are the other clinical importance of stem cell therapy. Extracellular matrix (ECM) and other environmental factors influence the fate and activity of stem cells.

Non-viral Induction of Transgene-free iPSCs from Somatic Fibroblasts of Multiple Mammalian Species

Induced pluripotent stem cells (iPSCs) are capable of providing an unlimited source of cells from all three germ layers and germ cells. The derivation and usage of iPSCs from various animal models may facilitate stem cell-based therapy, gene-modified animal production, and evolutionary studies assessing interspecies differences. However, there is a lack of species-wide methods for deriving iPSCs, in particular by means of non-viral and non-transgene-integrating (NTI) approaches. Here, we demonstrate the iPSC derivation from somatic fibroblasts of multiple mammalian species from three different taxonomic orders, including the common marmoset (Callithrix jacchus) in Primates, the dog (Canis lupus familiaris) in Carnivora, and the pig (Sus scrofa) in Cetartiodactyla, by combinatorial usage of chemical compounds and NTI episomal vectors. Interestingly, the fibroblasts temporarily acquired a neural stem cell-like state during the reprogramming. Collectively, our method, robustly applicable to various species, holds a great potential for facilitating stem cell-based research using various animals in Mammalia.

From Embryo to Adult: One Carbon Metabolism in Stem Cells

Stem cells are undifferentiated cells with self-renewal property and varying differentiation potential that allow the regeneration of tissue cells of an organism throughout adult life beginning from embryonic development. Through the asymmetric cell divisions, each stem cell replicates itself and produces an offspring identical with the mother cell, and a daughter cell that possesses the characteristics of a progenitor cell and commits to a specific lineage to differentiate into tissue cells to maintain homeostasis. To maintain a pool of stem cells to ensure tissue regeneration and homeostasis, it is important to regulate the metabolic functioning of stem cells, progenitor cells and adult tissue stem cells that will meet their internal and external needs. Upon fertilization, the zygote transforms metabolic reprogramming while implantation, embryonic development, organogenesis processes and after birth through adult life. Metabolism in stem cells is a concept that is relatively new to be enlightened. There are no adequate and comprehensive in vitro studies on the comparative analysis of the effects of one-carbon (1-C) metabolism on fetal and adult stem cells compared to embryonic and cancer stem cells' studies that have been reported recently. Since 1-C metabolism is linking parental environmental/ dietary factors and fetal development, investigating the epigenetic, genetic, metabolic and developmental effects on adult period is necessary. Several mutations and abnormalities in 1-C metabolism have been noted in disease changing from diabetes, cancer, pregnancy-related outcomes such as pre-eclampsia, spontaneous abortion, placental abruption, premature delivery, and cardiovascular diseases. In this review, the effects of 1-C metabolism, mainly the methionine and folate metabolism, in stem cells that exist in different developmental stages will be discussed.

The Role of E3s in Regulating Pluripotency of Embryonic Stem Cells and Induced Pluripotent Stem Cells

Pluripotent embryonic stem cells (ESCs) are derived from early embryos and can differentiate into any type of cells in living organisms. Induced pluripotent stem cells (iPSCs) resemble ESCs, both of which serve as excellent sources to study early embryonic development and realize cell replacement therapies for age-related degenerative diseases and other cell dysfunction-related illnesses. To achieve these valuable applications, comprehensively understanding of the mechanisms underlying pluripotency maintenance and acquisition is critical. Ubiquitination modifies proteins with Ubiquitin (Ub) at the post-translational level to monitor protein stability and activity. It is extensively involved in pluripotency-specific regulatory networks in ESCs and iPSCs. Ubiquitination is achieved by sequential actions of the Ub-activating enzyme E1, Ub-conjugating enzyme E2, and Ub ligase E3. Compared with E1s and E2s, E3s are most abundant, responsible for substrate selectivity and functional diversity. In this review, we focus on E3 ligases to discuss recent progresses in understanding how they regulate pluripotency and somatic cell reprogramming through ubiquitinating core ESC regulators.

3-D Cell Culture Systems in Bone Marrow Tissue and Organoid Engineering, and BM Phantoms as In Vitro Models of Hematological Cancer Therapeutics-A Review

We review the state-of-the-art in bone and marrow tissue engineering (BMTE) and hematological cancer tissue engineering (HCTE) in light of the recent interest in bone marrow environment and pathophysiology of hematological cancers. This review focuses on engineered BM tissue and organoids as in vitro models of hematological cancer therapeutics, along with identification of BM components and their integration as synthetically engineered BM mimetic scaffolds. In addition, the review details interaction dynamics of various BM and hematologic cancer (HC) cell types in co-culture systems of engineered BM tissues/phantoms as well as their relation to drug resistance and cytotoxicity. Interaction between hematological cancer cells and their niche, and the difference with respect to the healthy niche microenvironment narrated. Future perspectives of BMTE for in vitro disease models, BM regeneration and large scale ex vivo expansion of hematopoietic and mesenchymal stem cells for transplantation and therapy are explained. We conclude by overviewing the clinical application of biomaterials in BM and HC pathophysiology and its challenges and opportunities.

Derivation of stable embryonic stem cell-like, but transcriptionally heterogenous, induced pluripotent stem cells from non-permissive mouse strains

Genetic background is known to play a role in the ability to derive pluripotent, embryonic stem cells (ESC), a trait referred to as permissiveness. Previously we demonstrated that induced pluripotent stem cells (iPSC) can be readily derived from non-permissive mouse strains by addition of serum-based media supplemented with GSK3B and MEK inhibitors, termed 2iS media, 3 days into reprogramming. Here, we describe the derivation of second type of iPSC colony from non-permissive mouse strains that can be stably maintained independently of 2iS media. The resulting cells display transcriptional heterogeneity similar to that observed in ESC from permissive genetic backgrounds derived in conventional serum containing media supplemented with leukemia inhibitor factor. However, unlike previous studies that report exclusive subpopulations, we observe both exclusive and simultaneous expression of naive and primed cell surface markers. Herein, we explore shifts in pluripotency in the presence of 2iS and characterize heterogenous subpopulations to determine their pluripotent state and role in heterogenous iPSCs derived from the non-permissive NOD/ShiLtJ strain. We conclude that heterogeneity is a naturally occurring, necessary quality of stem cells that allows for the maintenance of pluripotency. This study further demonstrates the efficacy of the 2iS reprogramming technique. It is also the first study to derive stable ESC-like stem cells from the non-permissive NOD/ShiLtJ and WSB/EiJ strains, enabling easier and broader research possibilities into pluripotency for these and similar non-permissive mouse strains and species.

Dentin-Pulp Tissue Regeneration Approaches in Dentistry: An Overview and Current Trends

Conventional treatment approaches in irreversible pulpitis and apical periodontitis include the disinfection of the pulp space followed by filling with various materials, which is commonly known as the root canal treatment. Disadvantages including the loss of tooth vitality and defense mechanism against carious lesions, susceptibility to fractures, discoloration and microleakage led to the development of regenerative therapies for the dentin pulp-complex. The goal of dentin-pulp tissue regeneration is to reestablish the physiological pulp function such as pulp sensibility, pulp repair capability by mineralization and pulp immunity. Recent dentin-pulp tissue regeneration approaches can be divided into cell homing and cell transplantation. Cell based approaches include a suitable scaffold for the delivery of potent stem cells with or without bioactive molecules into the root canal system while cell homing is based on the recruitment of host endogenous stem cells from the resident tissue including periapical region or dental pulp. This review discusses the recent treatment modalities in dentin-pulp tissue regeneration through tissue engineering and current challenges and trends in this field of research.

Cell Signaling Coordinates Global PRC2 Recruitment and Developmental Gene Expression in Murine Embryonic Stem Cells

The recruitment of Polycomb repressive complex 2 (PRC2) to gene promoters is critical for its function in repressing gene expression in murine embryonic stem cells (mESCs). However, previous studies have demonstrated that although the expression of early lineage-specific genes is largely repressed, the genome-wide PRC2 occupancy is unexpectedly reduced in naive mESCs. In this study, we provide evidence that fibroblast growth factor/extracellular signal-regulated kinase signaling determines the global PRC2 occupancy through regulating the expression of PRC2-recruiting factor JARID2 in naive mESCs. At the transcriptional level, the de-repression of bivalent genes is predominantly determined by the presence of cell signaling-associated transcription factors but not the status of PRC2 occupancy at gene promoters. Hence, this study not only reveals a key molecular mechanism by which cell signaling regulates the PRC2 occupancy in mESCs but also elucidates the functional roles of transcription factors and Polycomb-mediated epigenetic mechanisms in transcriptional regulation.

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FGF/ERK signaling positively regulates Jarid2 expression in mESCs

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Reduced JARID2 causes global reduction of PRC2 occupancy in naive mESCs

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Reduced PRC2 occupancy alone is insufficient to induce transcriptional activation

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Cell signaling-associated transcription factors drive bivalent gene expression

Noncoding Y RNAs regulate the levels, subcellular distribution and protein interactions of their Ro60 autoantigen partner

Noncoding Y RNAs are abundant in animal cells and present in many bacteria. These RNAs are bound and stabilized by Ro60, a ring-shaped protein that is a target of autoantibodies in patients with systemic lupus erythematosus. Studies in bacteria revealed that Y RNA tethers Ro60 to a ring-shaped exoribonuclease, forming a double-ringed RNP machine specialized for structured RNA degradation. In addition to functioning as a tether, the bacterial RNA gates access of substrates to the Ro60 cavity. To identify roles for Y RNAs in mammals, we used CRISPR to generate mouse embryonic stem cells lacking one or both of the two murine Y RNAs. Despite reports that animal cell Y RNAs are essential for DNA replication, cells lacking these RNAs divide normally. However, Ro60 levels are reduced, revealing that Y RNA binding is required for Ro60 to accumulate to wild-type levels. Y RNAs regulate the subcellular location of Ro60, since Ro60 is reduced in the cytoplasm and increased in nucleoli when Y RNAs are absent. Last, we show that Y RNAs tether Ro60 to diverse effector proteins to generate specialized RNPs. Together, our data demonstrate that the roles of Y RNAs are intimately connected to that of their Ro60 partner.

The Distinct Role of Tcfs and Lef1 in the Self-Renewal or Differentiation of Mouse Embryonic Stem Cells

Background and Objectives

Tcfs and Lef1 are DNA-binding transcriptional factors in the canonical Wnt signaling pathway. In the absence of β-catenin, Tcfs and Lef1 generally act as transcriptional repressors with co-repressor proteins such as Groucho, CtBP, and HIC-5. However, Tcfs and Lef1 turn into transcriptional activators during the interaction with β-catenin. Therefore, the activity of Tcfs and Lef1 is regulated by β-catenin. However, the intrinsic role of Tcfs and Lef1 has yet to be examined. The purpose of this study was to determine whether Tcfs and Lef1 play differential roles in the regulation of self-renewal and differentiation of mouse ES cells.

Methods and Results

Interestingly, the expression of Tcfs and Lef1 was dynamically altered under various differentiation conditions, such as removal of LIF, EB formation and neuronal differentiation in N2B27 media, suggesting that the function of each Tcf and Lef1 may vary in ES cells. Ectopic expression of Tcf1 or the dominant negative form of Lef1 (Lef1-DN) contributes to ES cells to self-renew in the absence of leukemia inhibitory factor (LIF), whereas ectopic expression of Tcf3, Lef1 or Tcf1-DN did not support ES cells to self-renew. Ectopic expression of either Lef1 or Lef1-DN blocked neuronal differentiation, suggesting that the transient induction of Lef1 was necessary for the initiation and progress of differentiation. ChIP analysis shows that Tcf1 bound to Nanog promoter and ectopic expression of Tcf1 enhanced the transcription of Nanog.

Conclusions

The overall data suggest that Tcf1 plays a critical role in the maintenance of stemness whereas Lef1 is involved in the initiation of differentiation.

Intrafollicular spontaneous parthenogenetic development of dromedary camel oocytes

Dromedary camel oocytes are unique in their capability for intrafollicular and in vitro spontaneous parthenogenetic activation (SPA) and development. This study was designed for (a) observing the incidence of SPA and development of dromedary camel oocytes retrieved from ovaries; (b) assessing intrafollicular development of dromedary camel oocytes using histological examination; (c) evaluating the abilities of dromedary camel oocytes to mature, SPA, and develop in vitro; and (d) identifying the transcript abundance of Cdx2 messenger RNA (mRNA) expression in different stages of SPA and developed camel embryos. The results revealed that 2.33% of oocytes retrieved from dromedary camel ovaries were SPA and developed to blastocyst stage. Serial sections of dromedary camel ovaries also demonstrated the presence of 1.4 SPA and parthenotes per ovary, which included from two-cell to the blastocysts with demarcated trophectoderm and inner cell mass layers. A total of 2.6% in vitro matured dromedary camel oocytes developed into morulae. The SPA and developed dromedary embryos expressed transcript abundance for Cdx2 mRNA with the highest (p < .05) at the blastocyst. The present work determines for the first time the intrafollicular oocytes from the dromedary camel display SPA, and the parthenotes can develop into blastocysts and expressing Cdx2 mRNA.

Cellular Functions of OCT-3/4 Regulated by Ubiquitination in Proliferating Cells

Octamer-binding transcription factor 3/4 (OCT-3/4), which is involved in the tumorigenesis of somatic cancers, has diverse functions during cancer development. Overexpression of OCT-3/4 has been detected in various human somatic tumors, indicating that OCT-3/4 activation may contribute to the development and progression of cancers. Stem cells can undergo self-renewal, pluripotency, and reprogramming with the help of at least four transcription factors, OCT-3/4, SRY box-containing gene 2 (SOX2), Krüppel-like factor 4 (KLF4), and c-MYC. Of these, OCT-3/4 plays a critical role in maintenance of undifferentiated state of embryonic stem cells (ESCs) and in production of induced pluripotent stem cells (iPSCs). Stem cells can undergo partitioning through mitosis and separate into specific cell types, three embryonic germ layers: the endoderm, the mesoderm, and the trophectoderm. It has been demonstrated that the stability of OCT-3/4 is mediated by the ubiquitin-proteasome system (UPS), which is one of the key cellular mechanisms for cellular homeostasis. The framework of the mechanism is simple, but the proteolytic machinery is complicated. Ubiquitination promotes protein degradation, and ubiquitination of OCT-3/4 leads to regulation of cellular proliferation and differentiation. Therefore, it is expected that OCT-3/4 may play a key role in proliferation and differentiation of proliferating cells.