Generation of organized germ layers from a single mouse embryonic stem cell

A 3D micro-printed single cell micro-niche with asymmetric niche signals - An in vitro model for asymmetric cell division study

Intricate microenvironment signals orchestrate to affect cell behavior and fate during tissue morphogenesis. However, the underlying mechanisms on how specific local niche signals influence cell behavior and fate are not fully understood, owing to the lack of in vitro platform able to precisely, quantitatively, spatially, and independently manipulate individual niche signals. Here, microarrays of protein-based 3D single cell micro-niche (3D-SCμN), with precisely engineered biophysical and biochemical niche signals, are micro-printed by a multiphoton microfabrication and micropatterning technology. Mouse embryonic stem cell (mESC) is used as the model cell to study how local niche signals affect stem cell behavior and fate. By precisely engineering the internal microstructures of the 3D SCμNs, we demonstrate that the cell division direction can be controlled by the biophysical niche signals, in a cell shape-independent manner. After confining the cell division direction to a dominating axis, single mESCs are exposed to asymmetric biochemical niche signals, specifically, cell-cell adhesion molecule on one side and extracellular matrix on the other side. We demonstrate that, symmetry-breaking (asymmetric) niche signals successfully trigger cell polarity formation and bias the orientation of asymmetric cell division, the mitosis process resulting in two daughter cells with differential fates, in mESCs.

Orai1 and Orai3 act through distinct signalling axes to promote stemness and tumorigenicity of breast cancer stem cells

BACKGROUND

One of major challenges in breast tumor therapy is the existence of breast cancer stem cells (BCSCs). BCSCs are a small subpopulation of tumor cells that exhibit characteristics of stem cells. BCSCs are responsible for progression, recurrence, chemoresistance and metastasis of breast cancer. Ca2+ signalling plays an important role in diverse processes in cancer development. However, the role of Ca2+ signalling in BCSCs is still poorly understood.

METHODS

A highly effective 3D soft fibrin gel system was used to enrich BCSC-like cells from ER+ breast cancer lines MCF7 and MDA-MB-415. We then investigated the role of two Ca2+-permeable ion channels Orai1 and Orai3 in the growth and stemness of BCSC-like cells in vitro, and tumorigenicity in female NOD/SCID mice in vivo.

RESULTS

Orai1 RNA silencing and pharmacological inhibition reduced the growth of BCSC-like cells in tumor spheroids, decreased the expression levels of BCSC markers, and reduced the growth of tumor xenografts in NOD/SCID mice. Orai3 RNA silencing also had similar inhibitory effect on the growth and stemness of BCSC-like cells in vitro, and tumor xenograft growth in vivo. Mechanistically, Orai1 and SPCA2 mediate store-operated Ca2+ entry. Knockdown of Orai1 or SPCA2 inhibited glycolysis pathway, whereas knockdown of Orai3 or STIM1 had no effect on glycolysis.

CONCLUSION

We found that Orai1 interacts with SPCA2 to mediate store-independent Ca2+ entry, subsequently promoting the growth and tumorigenicity of BCSC-like cells via glycolysis pathway. In contrast, Orai3 and STIM1 mediate store-operated Ca2+ entry, promoting the growth and tumorigenicity of BCSC-like cells via a glycolysis-independent pathway. Together, our study uncovered a well-orchestrated mechanism through which two Ca2+ entry pathways act through distinct signalling axes to finely control the growth and tumorigenicity of BCSCs.

Coordination between endoderm progression and mouse gastruloid elongation controls endodermal morphotype choice

Embryonic development is highly robust. Morphogenetic variability between embryos (under ideal conditions) is largely quantitative. This robustness stands in contrast to in vitro embryo-like models, which, like most organoids, can display a high degree of tissue morphogenetic variability. The source of this difference is not fully understood. We use the mouse gastruloid model to study the morphogenetic progression of definitive endoderm (DE) and its divergence. We first catalog the different morphologies and characterize their statistics. We then learn predictive models for DE morphotype based on earlier expression and morphology measurements. Finally, we analyze these models to identify key drivers of morphotype variability and devise gastruloid-specific and global interventions that can lower this variability and steer morphotype choice. In the process, we identify two types of coordination lacking in the in vitro model but required for robust gut-tube formation. This approach can help improve the quality and usability of 3D embryo-like models.

Nanofiber-microwell cell culture system for spatially patterned differentiation of pluripotent stem cells in 3D

The intricate interplay between biochemical and physical cues dictates pluripotent stem cell (PSC) differentiation to form various tissues. While biochemical modulation has been extensively studied, the role of biophysical microenvironments in early lineage commitment remains elusive. Here, we introduce a novel 3D cell culture system combining electrospun nanofibers with microfabricated polydimethylsiloxane (PDMS) patterns. This system enables the controlled formation of semispherical human induced pluripotent stem cell (hiPSC) colonies, facilitating the investigation of local mechanical stem cell niches on mechano-responsive signaling and lineage specification. Our system unveiled spatially organized RhoA activity coupled with actin-myosin cable formation, suggesting mechano-dependent hiPSC behaviors. Nodal network analysis of RNA-seq data revealed RhoA downstream regulation of YAP signaling, DNA histone modifications, and patterned germ layer specification. Notably, altering colony morphology through controlled PDMS microwell shaping effectively modulated the spatial distribution of mechano-sensitive mediators and subsequent differentiation. This study provides a cell culture platform to decipher the role of biophysical cues in early embryogenesis, offering valuable insights for material design in tissue engineering and regenerative medicine applications.

Deep Learning Powered Identification of Differentiated Early Mesoderm Cells from Pluripotent Stem Cells

Pluripotent stem cells can be differentiated into all three germ-layers including ecto-, endo-, and mesoderm in vitro. However, the early identification and rapid characterization of each germ-layer in response to chemical and physical induction of differentiation is limited. This is a long-standing issue for rapid and high-throughput screening to determine lineage specification efficiency. Here, we present deep learning (DL) methodologies for predicting and classifying early mesoderm cells differentiated from embryoid bodies (EBs) based on cellular and nuclear morphologies. Using a transgenic murine embryonic stem cell (mESC) line, namely OGTR1, we validated the upregulation of mesodermal genes (Brachyury (T): DsRed) in cells derived from EBs for the deep learning model training. Cells were classified into mesodermal and non-mesodermal (representing endo- and ectoderm) classes using a convolutional neural network (CNN) model called InceptionV3 which achieved a very high classification accuracy of 97% for phase images and 90% for nuclei images. In addition, we also performed image segmentation using an Attention U-Net CNN and obtained a mean intersection over union of 61% and 69% for phase-contrast and nuclear images, respectively. This work highlights the potential of integrating cell culture, imaging technologies, and deep learning methodologies in identifying lineage specification, thus contributing to the advancements in regenerative medicine. Collectively, our trained deep learning models can predict the mesoderm cells with high accuracy based on cellular and nuclear morphologies.

An Insight into the Role of GLIS1 in Embryonic Development, iPSC Generation, and Cancer

The curiosity to discover transcription factors to reprogram somatic cells to induced pluripotent stem cells (iPSCs) resulted in the identification of a reprogramming factor, Gli-similar transcription factor GLIS1. This proline-rich Kruppel-like zinc finger transcription factor has a role in embryonic development, iPSC generation, and cancer. The spatial and temporal expression of GLIS1 during embryonic development implicates that it can control gene expression at specific developmental stages. Moreover, GLIS1 in combination with OCT4, SOX2, and KLF4 reprogramming factors resulted in an increase in reprogramming efficiency, giving rise to primarily bona fide iPSCs. Mutations in the GLIS1 gene are associated with several types of tumors and cancers, and it shows a tissue-specific function where it acts either as an oncogene or as a tumor suppressor gene. This review gives a comprehensive overview of GLIS1 and its important role in embryonic development, cancer, and the generation of iPSCs.

Mass production of lumenogenic human embryoid bodies and functional cardiospheres using in-air-generated microcapsules

Organoids are engineered 3D miniature tissues that are defined by their organ-like structures, which drive a fundamental understanding of human development. However, current organoid generation methods are associated with low production throughputs and poor control over size and function including due to organoid merging, which limits their clinical and industrial translation. Here, we present a microfluidic platform for the mass production of lumenogenic embryoid bodies and functional cardiospheres. Specifically, we apply triple-jet in-air microfluidics for the ultra-high-throughput generation of hollow, thin-shelled, hydrogel microcapsules that can act as spheroid-forming bioreactors in a cytocompatible, oil-free, surfactant-free, and size-controlled manner. Uniquely, we show that microcapsules generated by in-air microfluidics provide a lumenogenic microenvironment with near 100% efficient cavitation of spheroids. We demonstrate that upon chemical stimulation, human pluripotent stem cell-derived spheroids undergo cardiomyogenic differentiation, effectively resulting in the mass production of homogeneous and functional cardiospheres that are responsive to external electrical stimulation. These findings drive clinical and industrial adaption of stem cell technology in tissue engineering and drug testing.

Self-formation of concentric zones of telencephalic and ocular tissues and directional retinal ganglion cell axons

The telencephalon and eye in mammals are originated from adjacent fields at the anterior neural plate. Morphogenesis of these fields generates telencephalon, optic-stalk, optic-disc, and neuroretina along a spatial axis. How these telencephalic and ocular tissues are specified coordinately to ensure directional retinal ganglion cell (RGC) axon growth is unclear. Here, we report self-formation of human telencephalon-eye organoids comprising concentric zones of telencephalic, optic-stalk, optic-disc, and neuroretinal tissues along the center-periphery axis. Initially-differentiated RGCs grew axons towards and then along a path defined by adjacent PAX2+ VSX2+ optic-disc cells. Single-cell RNA sequencing of these organoids not only confirmed telencephalic and ocular identities but also identified expression signatures of early optic-disc, optic-stalk, and RGCs. These signatures were similar to those in human fetal retinas. Optic-disc cells in these organoids differentially expressed FGF8 and FGF9; FGFR inhibitions drastically decreased early RGC differentiation and directional axon growth. Through the RGC-specific cell-surface marker CNTN2 identified here, electrophysiologically excitable RGCs were isolated under a native condition. Our findings provide insight into the coordinated specification of early telencephalic and ocular tissues in humans and establish resources for studying RGC-related diseases such as glaucoma.

YAP at the Crossroads of Biomechanics and Drug Resistance in Human Cancer

Biomechanical forces are of fundamental importance in biology, diseases, and medicine. Mechanobiology is an emerging interdisciplinary field that studies how biological mechanisms are regulated by biomechanical forces and how physical principles can be leveraged to innovate new therapeutic strategies. This article reviews state-of-the-art mechanobiology knowledge about the yes-associated protein (YAP), a key mechanosensitive protein, and its roles in the development of drug resistance in human cancer. Specifically, the article discusses three topics: how YAP is mechanically regulated in living cells; the molecular mechanobiology mechanisms by which YAP, along with other functional pathways, influences drug resistance of cancer cells (particularly lung cancer cells); and finally, how the mechanical regulation of YAP can influence drug resistance and vice versa. By integrating these topics, we present a unified framework that has the potential to bring theoretical insights into the design of novel mechanomedicines and advance next-generation cancer therapies to suppress tumor progression and metastasis.

Self-formation of concentric zones of telencephalic and ocular tissues and directional retinal ganglion cell axons

The telencephalon and eye in mammals are originated from adjacent fields at the anterior neural plate. Morphogenesis of these fields generates telencephalon, optic-stalk, optic-disc, and neuroretina along a spatial axis. How these telencephalic and ocular tissues are specified coordinately to ensure directional retinal ganglion cell (RGC) axon growth is unclear. Here, we report the self-formation of human telencephalon-eye organoids comprising concentric zones of telencephalic, optic-stalk, optic-disc, and neuroretinal tissues along the center-periphery axis. Initially-differentiated RGCs grew axons towards and then along a path defined by adjacent PAX2+ optic-disc cells. Single-cell RNA sequencing of CONCEPT organoids not only confirmed telencephalic and ocular identities but also identified expression signatures of early optic-disc, optic-stalk, and RGCs. These signatures were similar to those in human fetal retinas. Optic-disc cells in CONCEPT organoids differentially expressed FGF8 and FGF9 ; FGFR inhibitions drastically decreased RGC differentiation and directional axon growth. Through the identified RGC-specific cell-surface marker CNTN2, electrophysiologically-excitable RGCs were isolated under a native condition. Our findings provide insight into the coordinated specification of early telencephalic and ocular tissues in humans and establish resources for studying RGC-related diseases such as glaucoma.

Impact statement

A human telencephalon-eye organoid model that exhibited axon growth and pathfinding from retinal ganglion cell (RGC) axons is reported; via cell surface marker CNTN2 identified using scRNA-seq, early RGCs were isolated under a native condition.

Thermostable Human Basic Fibroblast Growth Factor (TS-bFGF) Engineered with a Disulfide Bond Demonstrates Superior Culture Outcomes in Human Pluripotent Stem Cell

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) can differentiate into various tissues and are an essential source of various disease models and therapeutics. Various growth factors are required in order to culture pluripotent stem cells, among which basic fibroblast growth factor (bFGF) is essential for maintaining stem cell ability. However, bFGF has a short half-life (8 h) under normal mammalian cell culture conditions, and its activity decreases after 72 h, posing a serious problem in the production of high-quality stem cells. Here, we evaluated the various functions of pluripotent stem cells (PSCs) by utilizing an engineered thermostable bFGF (TS-bFGF) that is thermally stable and maintains activity longer under mammalian culture conditions. PSCs cultured with TS-bFGF showed better proliferation, stemness, morphology, and differentiation than cells cultured with wild-type bFGF. In light of the importance of stem cells in a wide range of applications in the medical and biotechnology fields, we anticipate that TS-bFGF, as a thermostable and long-acting bFGF, can play a key role in securing high-quality stem cells through various sets of stem cell culture processes.

YAP1 is essential for self-organized differentiation of pluripotent stem cells

Induced pluripotent stem cells (iPSCs) form aggregates that recapitulate aspects of the self-organization in early embryogenesis. Within few days, cells undergo a transition from epithelial-like structures to organized three-dimensional embryoid bodies (EBs) with upregulation of germ layer-specific genes. However, it is largely unclear, which signaling cascades regulate self-organized differentiation. The Yes-associated protein 1 (YAP1) is a downstream effector of the Hippo pathway and essential mechanotransducer. YAP1 has been suggested to play a crucial role for early embryo development, but the relevance for early germ layer commitment of human iPSCs remains to be elucidated. To gain insights into the function of YAP1 in early cell-fate decisions, we generated YAP1 knockout (YAP^-/-) iPSC lines with CRISPR/Cas9 technology and analyzed transcriptomic and epigenetic modifications. YAP^-/- iPSCs showed increased expression of several YAP1 targets and of NODAL, an important regulator of cell differentiation. Furthermore, YAP1 deficiency evoked global DNA methylation changes. Directed differentiation of adherent iPSC colonies towards endoderm, mesoderm, and ectoderm could be induced, albeit endodermal and ectodermal differentiation showed transcriptomic and epigenetic changes in YAP^-/- lines. Notably, in undirected self-organized YAP^-/- EBs germ layer specification was clearly impaired. This phenotype was rescued via lentiviral overexpression of YAP1 and also by NODAL inhibitors. Our results demonstrate that YAP1 plays an important role during early germ layer specification of iPSCs, particularly for the undirected self-organization of EBs, and this is at least partly attributed to activation of the NODAL signaling.

Functional Blood-Brain Barrier Model with Tight Connected Minitissue by Liquid Substrates Culture

The functional blood-brain barrier (BBB) model can provide a reliable tool for better understanding BBB transport mechanisms and in vitro preclinical experimentation. However, recapitulating microenvironmental complexities and physiological functions in an accessible approach remains a major challenge. Here, a new BBB model with a high-cell spatial density and tightly connected biomimetic minitissue is presented. The minitissue, pivotal functional structure of the BBB model, is fabricated by a novel and easy-to-use liquid substrate culture (LSC) method, which allows cells to self-assemble and self-heal into macrosized, tightly connected membranous minitissue. The minitissue with uniform thickness can be easily harvested in their entirety with extracellular matrix. Attributed to the tightly connected minitissue formed by LSC, the fabricated BBB biomimetic model has 1 to 2 orders of magnitude higher transendothelial electric resistance than the commonly reported BBB model. It also better prevents the transmission of large molecular substances, recapitulating the functional features of BBB. Furthermore, the BBB biomimetic model provides feedback regarding BBB-destructive drugs, exhibits selective transmission, and shows efflux pump activity. Overall, this model can serve as an accessible tool for life science or clinical medical researchers to enhance the understanding of human BBB and expedite the development of new brain-permeable drugs.

Lnc956 regulates mouse embryonic stem cell differentiation in response to DNA damage in a p53-independent pathway

Maintaining genomic stability is crucial for embryonic stem cells (ESCs). ESCs with unrepaired DNA damage are eliminated through differentiation and apoptosis. To date, only tumor suppressor p53 is known to be implicated in this quality control process. Here, we identified a p53-independent quality control factor lncRNA NONMMUT028956 (Lnc956 for short) in mouse ESCs. Lnc956 is prevalently expressed in ESCs and regulates the differentiation of ESCs after DNA damage. Mechanistically, Ataxia telangiectasia mutated (ATM) activation drives m6A methylation of Lnc956, which promotes its interaction with Krüppel-like factor 4 (KLF4). Lnc956-KLF4 association sequestrates the KLF4 protein and prevents KLF4's transcriptional regulation on pluripotency. This posttranslational mechanism favors the rapid shutdown of the regulatory circuitry of pluripotency. Thus, ATM signaling in ESCs can activate two pathways mediated by p53 and Lnc956, respectively, which act together to ensure robust differentiation and apoptosis in response to unrepaired DNA damage.

Temporal perturbation of histone deacetylase activity reveals a requirement for HDAC1-3 in mesendoderm cell differentiation

Histone deacetylases (HDACs) are a class of enzymes that control chromatin state and influence cell fate. We evaluated the chromatin accessibility and transcriptome dynamics of zinc-containing HDACs during cell differentiation in vitro coupled with chemical perturbation to identify the role of HDACs in mesendoderm cell fate specification. Single-cell RNA sequencing analyses of HDAC expression during human pluripotent stem cell (hPSC) differentiation in vitro and mouse gastrulation in vivo reveal a unique association of HDAC1 and -3 with mesendoderm gene programs during exit from pluripotency. Functional perturbation with small molecules reveals that inhibition of HDAC1 and -3, but not HDAC2, induces mesoderm while impeding endoderm and early cardiac progenitor specification. These data identify unique biological functions of the structurally homologous enzymes HDAC1-3 in influencing hPSC differentiation from pluripotency toward mesendodermal and cardiac progenitor populations.

Synthetic developmental biology: Engineering approaches to guide multicellular organization

Multicellular organisms of various complexities self-organize in nature. Organoids are in vitro 3D structures that display important aspects of the anatomy and physiology of their in vivo counterparts and that develop from pluripotent or tissue-specific stem cells through a self-organization process. In this review, we describe the multidisciplinary concept of “synthetic developmental biology” where engineering approaches are employed to guide multicellular organization in an experimental setting. We introduce a novel classification of engineering approaches based on the extent of microenvironmental manipulation applied to organoids. In the final section, we discuss how engineering tools might help overcome current limitations in organoid construction.

Towards an integrative understanding of cancer mechanobiology: calcium, YAP, and microRNA under biophysical forces

An increasing number of studies have demonstrated the significant roles of the interplay between microenvironmental mechanics in tissues and biochemical-genetic activities in resident tumor cells at different stages of tumor progression. Mediated by molecular mechano-sensors or -transducers, biomechanical cues in tissue microenvironments are transmitted into the tumor cells and regulate biochemical responses and gene expression through mechanotransduction processes. However, the molecular interplay between the mechanotransduction processes and intracellular biochemical signaling pathways remains elusive. This paper reviews the recent advances in understanding the crosstalk between biomechanical cues and three critical biochemical effectors during tumor progression: calcium ions (Ca²⁺), yes-associated protein (YAP), and microRNAs (miRNAs). We address the molecular mechanisms underpinning the interplay between the mechanotransduction pathways and each of the three effectors. Furthermore, we discuss the functional interactions among the three effectors in the context of soft matter and mechanobiology. We conclude by proposing future directions on studying the tumor mechanobiology that can employ Ca²⁺, YAP, and miRNAs as novel strategies for cancer mechanotheraputics. This framework has the potential to bring insights into the development of novel next-generation cancer therapies to suppress and treat tumors.

Viscoelasticity, Like Forces, Plays a Role in Mechanotransduction

Viscoelasticity and its alteration in time and space has turned out to act as a key element in fundamental biological processes in living systems, such as morphogenesis and motility. Based on experimental and theoretical findings it can be proposed that viscoelasticity of cells, spheroids and tissues seems to be a collective characteristic that demands macromolecular, intracellular component and intercellular interactions. A major challenge is to couple the alterations in the macroscopic structural or material characteristics of cells, spheroids and tissues, such as cell and tissue phase transitions, to the microscopic interferences of their elements. Therefore, the biophysical technologies need to be improved, advanced and connected to classical biological assays. In this review, the viscoelastic nature of cytoskeletal, extracellular and cellular networks is presented and discussed. Viscoelasticity is conceptualized as a major contributor to cell migration and invasion and it is discussed whether it can serve as a biomarker for the cells’ migratory capacity in several biological contexts. It can be hypothesized that the statistical mechanics of intra- and extracellular networks may be applied in the future as a powerful tool to explore quantitatively the biomechanical foundation of viscoelasticity over a broad range of time and length scales. Finally, the importance of the cellular viscoelasticity is illustrated in identifying and characterizing multiple disorders, such as cancer, tissue injuries, acute or chronic inflammations or fibrotic diseases.

Viscoelasticity Acts as a Marker for Tumor Extracellular Matrix Characteristics

Biological materials such as extracellular matrix scaffolds, cancer cells, and tissues are often assumed to respond elastically for simplicity; the viscoelastic response is quite commonly ignored. Extracellular matrix mechanics including the viscoelasticity has turned out to be a key feature of cellular behavior and the entire shape and function of healthy and diseased tissues, such as cancer. The interference of cells with their local microenvironment and the interaction among different cell types relies both on the mechanical phenotype of each involved element. However, there is still not yet clearly understood how viscoelasticity alters the functional phenotype of the tumor extracellular matrix environment. Especially the biophysical technologies are still under ongoing improvement and further development. In addition, the effect of matrix mechanics in the progression of cancer is the subject of discussion. Hence, the topic of this review is especially attractive to collect the existing endeavors to characterize the viscoelastic features of tumor extracellular matrices and to briefly highlight the present frontiers in cancer progression and escape of cancers from therapy. Finally, this review article illustrates the importance of the tumor extracellular matrix mechano-phenotype, including the phenomenon viscoelasticity in identifying, characterizing, and treating specific cancer types.

Cardiac Tissue Engineering for the Treatment of Myocardial Infarction

Poor cell engraftment rate is one of the primary factors limiting the effectiveness of cell transfer therapy for cardiac repair. Recent studies have shown that the combination of cell-based therapy and tissue engineering technology can improve stem cell engraftment and promote the therapeutic effects of the treatment for myocardial infarction. This mini-review summarizes the recent progress in cardiac tissue engineering of cardiovascular cells from differentiated human pluripotent stem cells (PSCs), highlights their therapeutic applications for the treatment of myocardial infarction, and discusses the present challenges of cardiac tissue engineering and possible future directions from a clinical perspective.

Spatial Stem Cell Fate Engineering via Facile Morphogen Localization

Spatiotemporally controlled presentation of morphogens and elaborate modulation of signaling pathways elicit pattern formation during development. Though this process is critical for proper organogenesis, unraveling the mechanisms of developmental biology have been restricted by challenges associated with studying human embryos. Human pluripotent stem cells (hPSCs) have been used to model development in vitro, however difficulties in precise spatiotemporal control of the cellular microenvironment have limited the utility of this model in exploring mechanisms of pattern formation. Here, a simple and versatile method is presented to spatially pattern hPSC differentiation in 2-dimensional culture via localized morphogen adsorption on substrates. Morphogens including bone morphogenetic protein 4 (BMP4), activin A, and WNT3a are patterned to induce localized mesendoderm, endoderm, cardiomyocyte (CM), and epicardial cell (EpiC) differentiation from hPSCs and hPSC-derived progenitors. Patterned CM and EpiC co-differentiation allows investigation of intercellular interactions in a spatially controlled manner and demonstrate improved alignment of CMs in proximity to EpiCs. This approach provides a platform for the controlled and systematic study of early pattern formation. Moreover, this study provides a facile approach to generate 2D patterned hPSC-derived tissue structures for modeling disease and drug interactions.

A novel engineered vascular construct of stem cell-laden 3D-printed PGSA scaffold enhances tissue revascularization

Development of transplantable engineered tissue has been hampered by lacking vascular network within the engineered tissue. Three-dimensional (3D) printing has emerged as a new technology with great potential in fabrication and customization of geometric microstructure. In this study, utilizing digital light processing system, we manufactured a recently designed novel 3D architecture scaffold with poly(glycerol sebacate) acrylate (PGSA). Vascular construct was subsequently generated by seeding stem cells within this scaffold. PGSA provided inductive substrate in terms of supporting three-germ layer differentiation of embryonic stem cells (ESCs) and also promoting ESCs-derived vascular progenitor cells (VPCs) differentiation into endothelial cells (ECs). Furthermore, the differentiation efficiency of VPCs into ECs on PGSA was much higher than that on collagen IV or fibronectin. The results from seeding VPCs in the rotating hexagonal PGSA scaffold suggest that this architectural framework is highly efficient for cell engraftment in 3D structures. After long-term suspension culture of the VPCs in scaffold under directed EC differentiation condition, VPC-differentiated ECs were populated in the scaffold and expressed EC markers. Transplantation of the vascular construct in mice resulted in formation of new vascular network and integration of the microvasculature within the scaffold into the existing vasculature of host tissue. Importantly, in a mouse model of wound healing, ECs from the transplanted vascular construct directly contributed to revascularization and enhanced blood perfusion at the injured site. Collectively, this transplantable vascular construct provides an innovative alternative therapeutic strategy for vascular tissue engineering.

Effect of the phenylpyrrole fungicide fludioxonil on cell proliferation and cardiac differentiation in mouse embryonic stem cells

Fludioxnil is extensively used as a fungicide in agricultural application, but its possible impact on embryonic development is not yet well understood. In this study, the potential effect of fludioxonil on cardiac differentiation was evaluated in mouse embryonic stem cells (mESCs). The water-soluble tetrazolium (WST) and colony formation assays were conducted to confirm the effect of fludioxonil on proliferation of mESCs. The effect of fludioxonil on the ability of mESCs to form mouse embryoid bodies (mEBs) was determined by the hanging drop assay, whereas the ability of cardiomyocyte differentiation in the early stage was evaluated by determining the beating ratio (ratio of the number of contracting cells to the number of attached EBs) of cardiomyocytes. The viability of mESCs was significantly decreased (less than 50 %) at 10^-5 M fludioxonil. Results of the colony formation assay revealed suppressed colony formation at 10^-5 M fludioxonil (about 50 % at 5 days). Furthermore, the expressions of cell-cycle related proteins, i.e., cyclin D1, cyclin E, p21 and p27, were altered and trending towards inhibiting cell growth. Exposure to fludioxonil also resulted in reduced size of the mEB and induced increasing expression levels of the pluripotency markers Oct4, Sox2 and Nanog. Development of the beating ratio in the process of differentiation to cardiomyocytes derived from mESCs was completely inhibited after exposure to 10^-5 M fludioxonil during the early stage of differentiation (day 5), whereas the beating ratio gradually increased after 5-day treatment. Simultaneously, expressions of the cardiomyocyte-related proteins, Gata4, Hand1 and cTnI, were inhibited after exposure to 10^-5 M fludioxonil. Taken together, these results imply that fludioxonil may impact on the developmental process of mESCs, particularly the cardiac lineage.

Cytoskeletal prestress: The cellular hallmark in mechanobiology and mechanomedicine

Increasing evidence demonstrates that mechanical forces, in addition to soluble molecules, impact cell and tissue functions in physiology and diseases. How living cells integrate mechanical signals to perform appropriate biological functions is an area of intense investigation. Here, we review the evidence of the central role of cytoskeletal prestress in mechanotransduction and mechanobiology. Elevating cytoskeletal prestress increases cell stiffness and reinforces cell stiffening, facilitates long-range cytoplasmic mechanotransduction via integrins, enables direct chromatin stretching and rapid gene expression, spurs embryonic development and stem cell differentiation, and boosts immune cell activation and killing of tumor cells whereas lowering cytoskeletal prestress maintains embryonic stem cell pluripotency, promotes tumorigenesis and metastasis of stem cell-like malignant tumor-repopulating cells, and elevates drug delivery efficiency of soft-tumor-cell-derived microparticles. The overwhelming evidence suggests that the cytoskeletal prestress is the governing principle and the cellular hallmark in mechanobiology. The application of mechanobiology to medicine (mechanomedicine) is rapidly emerging and may help advance human health and improve diagnostics, treatment, and therapeutics of diseases.

Molecular signature and colony morphology affect in vitro pluripotency of porcine induced pluripotent stem cells

Overall efficiency of cell reprogramming for porcine fibroblasts into induced pluripotent stem cells (iPSCs) is currently poor, and few cell lines have been established. This study examined gene expression during early phase of cellular reprogramming in the relationship to the iPSC colony morphology and in vitro pluripotent characteristics. Fibroblasts were reprogrammed with OCT4, SOX2, KLF4 and c-MYC. Two different colony morphologies referred to either compact (n = 10) or loose (n = 10) colonies were further examined for proliferative activity, gene expression and in vitro pluripotency. A total of 1,697 iPSC-like colonies (2.34%) were observed after gene transduction. The compact colonies contained with tightly packed cells with a distinct-clear border between the colony and feeder cells, while loose colonies demonstrated irregular colony boundary. For quantitative expression of genes responsible for early phase cell reprogramming, the Dppa2 and EpCAM were significantly upregulated while NR0B1 was downregulated in compact colonies compared with loose phenotype (p < .05). Higher proportion of compact iPSC phenotype (5 of 10, 50%) could be maintained in undifferentiated state for more than 50 passages compared unfavourably with loose morphology (3 of 10, 30%). All iPS cell lines obtained from these two types of colony morphologies expressed pluripotent genes and proteins (OCT4, NANOG and E-cadherin). In addition, they could aggregate and form three-dimensional structure of embryoid bodies. However, only compact iPSC colonies differentiated into three germ layers. Molecular signature of early phase of cell reprogramming coupled with primary colony morphology reflected the in vitro pluripotency of porcine iPSCs. These findings can be simply applied for pre-screening selection of the porcine iPSC cell line.

Biomaterials-based approaches to model embryogenesis

Understanding, reproducing, and regulating the cellular and molecular processes underlying human embryogenesis is critical to improve our ability to recapitulate tissues with proper architecture and function, and to address the dysregulation of embryonic programs that underlies birth defects and cancer. The rapid emergence of stem cell technologies is enabling enormous progress in understanding embryogenesis using simple, powerful, and accessible in vitro models. Biomaterials are playing a central role in providing the spatiotemporal organisation of biophysical and biochemical signalling necessary to mimic, regulate and dissect the evolving embryonic niche in vitro. This contribution is rapidly improving our understanding of the mechanisms underlying embryonic patterning, in turn enabling the development of more effective clinical interventions for regenerative medicine and oncology. Here we highlight how key biomaterial approaches contribute to organise signalling in human embryogenesis models, and we summarise the biological insights gained from these contributions. Importantly, we highlight how nanotechnology approaches have remained largely untapped in this space, and we identify their key potential contributions.

Progress in the mechanical modulation of cell functions in tissue engineering

In mammals, mechanics at multiple stages-nucleus to cell to ECM-underlie multiple physiological and pathological functions from its development to reproduction to death. Under this inspiration, substantial research has established the role of multiple aspects of mechanics in regulating fundamental cellular processes, including spreading, migration, growth, proliferation, and differentiation. However, our understanding of how these mechanical mechanisms are orchestrated or tuned at different stages to maintain or restore the healthy environment at the tissue or organ level remains largely a mystery. Over the past few decades, research in the mechanical manipulation of the surrounding environment-known as substrate or matrix or scaffold on which, or within which, cells are seeded-has been exceptionally enriched in the field of tissue engineering and regenerative medicine. To do so, traditional tissue engineering aims at recapitulating key mechanical milestones of native ECM into a substrate for guiding the cell fate and functions towards specific tissue regeneration. Despite tremendous progress, a big puzzle that remains is how the cells compute a host of mechanical cues, such as stiffness (elasticity), viscoelasticity, plasticity, non-linear elasticity, anisotropy, mechanical forces, and mechanical memory, into many biological functions in a cooperative, controlled, and safe manner. High throughput understanding of key cellular decisions as well as associated mechanosensitive downstream signaling pathway(s) for executing these decisions in response to mechanical cues, solo or combined, is essential to address this issue. While many reports have been made towards the progress and understanding of mechanical cues-particularly, substrate bulk stiffness and viscoelasticity-in regulating the cellular responses, a complete picture of mechanical cues is lacking. This review highlights a comprehensive view on the mechanical cues that are linked to modulate many cellular functions and consequent tissue functionality. For a very basic understanding, a brief discussion of the key mechanical players of ECM and the principle of mechanotransduction process is outlined. In addition, this review gathers together the most important data on the stiffness of various cells and ECM components as well as various tissues/organs and proposes an associated link from the mechanical perspective that is not yet reported. Finally, beyond addressing the challenges involved in tuning the interplaying mechanical cues in an independent manner, emerging advances in designing biomaterials for tissue engineering are also explored.

Self-organized signaling in stem cell models of embryos

Mammalian embryonic development is a complex process driven by self-organization. Understanding how a fertilized egg develops into an embryo composed of more than 200 cell types in precise spatial patterns remains one of the fundamental challenges in biology. Pluripotent stem cells have been used as in vitro models for investigating mammalian development, and represent promising building blocks for regenerative therapies. Recently, sophisticated stem cell-based models that recapitulate early embryonic fate patterning and morphogenesis have been developed. In this article, we review recent advances in stem cell models of embryos in particular focusing on signaling activities underpinning cell fate decisions in space and time.

Machine learning-assisted high-content analysis of pluripotent stem cell-derived embryos in vitro

Stem cell-based embryo models by cultured pluripotent and extra-embryonic lineage stem cells are novel platforms to model early postimplantation development. We showed that induced pluripotent stem cells (iPSCs) could form ITS (iPSCs and trophectoderm stem cells) and ITX (iPSCs, trophectoderm stem cells, and XEN cells) embryos, resembling the early gastrula embryo developed in vivo. To facilitate the efficient and unbiased analysis of the stem cell-based embryo model, we set up a machine learning workflow to extract multi-dimensional features and perform quantification of ITS embryos using 3D images collected from a high-content screening system. We found that different PSC lines differ in their ability to form embryo-like structures. Through high-content screening of small molecules and cytokines, we identified that BMP4 best promoted the morphogenesis of the ITS embryo. Our study established an innovative strategy to analyze stem cell-based embryo models and uncovered new roles of BMP4 in stem cell-based embryo models.

The PRAME family of cancer testis antigens is essential for germline development and gametogenesis†

Preferentially expressed antigen in melanoma (PRAME) belongs to a group of cancer/testis antigens that are predominately expressed in the testis and a variety of tumors, and are involved in immunity and reproduction. Much of the attention on PRAME has centered on cancer biology as PRAME is a prognostic biomarker for a wide range of cancers and a potential immunotherapeutic target. Less information is available about the PRAME family's function (s) during gametogenesis and in the overall reproduction process. Here, we review the current knowledge of the PRAME gene family and its function in germline development and gametogenesis. Members of the PRAME family are leucine rich repeat proteins, localized in nucleus and cytoplasm, with multifaceted roles in germ cells. As transcriptional regulators, the PRAME family proteins are involved in germline development, particularly in the maintenance of embryonic stem cell pluripotency, development of primordial germ cells, and differentiation/proliferation of spermatogenic and oogenic cells. The PRAME family proteins are also enriched in cytoplasmic organelles, such as rough endoplasmic reticulum, Golgi vesicle, germinal granules, centrioles, and play a role in the formation of the acrosome and sperm tail during spermiogenesis. The PRAME gene family remains transcriptionally active in the germline throughout the entire life cycle and is essential for gametogenesis, with some members specific to either male or female germ cells, while others are involved in both male and female gametogenesis. A potential molecular mechanism that underlies the function of PRAME, and is shared by gametogenesis and oncogenesis is also discussed.

From Snapshots to Development: Identifying the Gaps in the Development of Stem Cell-based Embryo Models along the Embryonic Timeline

In recent years, stem cell-based models that reconstruct mouse and human embryogenesis have gained significant traction due to their near-physiological similarity to natural embryos. Embryo models can be generated in large numbers, provide accessibility to a variety of experimental tools such as genetic and chemical manipulation, and confer compatibility with automated readouts, which permits exciting experimental avenues for exploring the genetic and molecular principles of self-organization, development, and disease. However, the current embryo models recapitulate only snapshots within the continuum of embryonic development, allowing the progression of the embryonic tissues along a specific direction. Hence, to fully exploit the potential of stem cell-based embryo models, multiple important gaps in the developmental landscape need to be covered. These include recapitulating the lesser-explored interactions between embryonic and extraembryonic tissues such as the yolk sac, placenta, and the umbilical cord; spatial and temporal organization of tissues; and the anterior patterning of embryonic development. Here, it is detailed how combinations of stem cells and versatile bioengineering technologies can help in addressing these gaps and thereby extend the implications of embryo models in the fields of cell biology, development, and regenerative medicine.

Efficient induction of neural progenitor cells from human ESC/iPSCs on Type I Collagen

A stable, rapid and effective neural differentiation method is essential for the clinical applications of human embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) in treating neurological disorders and diseases. Herein, we established a novel and robust monolayer differentiation method to produce functional neural progenitor cells (NPCs) from human ESC/iPSCs on Type I Collagen. The derived cells not only displayed the requisite markers, but also behaved similarly to classic NPCs both in vitro and in vivo. Upon transplantation into traumatic brain injury model, the derived NPCs facilitated recovery from injury. We also found that SMAD signaling stayed down throughout the differentiation process on Type I Collagen, and the pluripotent signals were rapidly downregulated along with raising up of neural early markers on the third day. Meanwhile, ATAC-seq data showed the related mediation of distinct transcriptome and global chromatin dynamics during NPC induction. Totally, our results thus provide a convenient way to generate NPCs from human ESC/iPSCs for neural diseases' treatment.

Stem-cell-based embryo models for fundamental research and translation

Despite its importance, understanding the early phases of human development has been limited by availability of human samples. The recent emergence of stem-cell-derived embryo models, a new field aiming to use stem cells to construct in vitro models to recapitulate snapshots of the development of the mammalian conceptus, opens up exciting opportunities to promote fundamental understanding of human development and advance reproductive and regenerative medicine. This Review provides a summary of the current knowledge of early mammalian development, using mouse and human conceptuses as models, and emphasizes their similarities and critical differences. We then highlight existing embryo models that mimic different aspects of mouse and human development. We further discuss bioengineering tools used for controlling multicellular interactions and self-organization critical for the development of these models. We conclude with a discussion of the important next steps and exciting future opportunities of stem-cell-derived embryo models for fundamental discovery and translation.

Basic Biology of Extracellular Matrix in the Cardiovascular System, Part 1/4: JACC Focus Seminar

The extracellular matrix (ECM) is the noncellular component of tissues in the cardiovascular system and other organs throughout the body. It is formed of filamentous proteins, proteoglycans, and glycosaminoglycans, which extensively interact and whose structure and dynamics are modified by cross-linking, bridging proteins, and cleavage by matrix degrading enzymes. The ECM serves important structural and regulatory roles in establishing tissue architecture and cellular function. The ECM of the developing heart has unique properties created by its emerging contractile nature; similarly, ECM lining blood vessels is highly elastic in order to sustain the basal and pulsatile forces imposed on their walls throughout life. In this part 1 of a 4-part JACC Focus Seminar, we focus on the role, function, and basic biology of the ECM in both heart development and in the adult.

Measuring Internal Forces in Single-Stranded DNA: Application to a DNA Force Clamp

We present a new method for calculating internal forces in DNA structures using coarse-grained models and demonstrate its utility with the oxDNA model. The instantaneous forces on individual nucleotides are explored and related to model potentials, and using our framework, internal forces are calculated for two simple DNA systems and for a recently published nanoscopic force clamp. Our results highlight some pitfalls associated with conventional methods for estimating internal forces, which are based on elastic polymer models, and emphasize the importance of carefully considering secondary structure and ionic conditions when modeling the elastic behavior of single-stranded DNA. Beyond its relevance to the DNA nanotechnological community, we expect our approach to be broadly applicable to calculations of internal force in a variety of structures-from DNA to protein-and across other coarse-grained simulation models.

Cell Mechanics in Embryoid Bodies

Embryoid bodies (EBs) resemble self-organizing aggregates of pluripotent stem cells that recapitulate some aspects of early embryogenesis. Within few days, the cells undergo a transition from rather homogeneous epithelial-like pluripotent stem cell colonies into a three-dimensional organization of various cell types with multifaceted cell-cell interactions and lumen formation-a process associated with repetitive epithelial-mesenchymal transitions. In the last few years, culture methods have further evolved to better control EB size, growth, cellular composition, and organization-e.g., by the addition of morphogens or different extracellular matrix molecules. There is a growing perception that the mechanical properties, cell mechanics, and cell signaling during EB development are also influenced by physical cues to better guide lineage specification; substrate elasticity and topography are relevant, as well as shear stress and mechanical strain. Epithelial structures outside and inside EBs support the integrity of the cell aggregates and counteract mechanical stress. Furthermore, hydrogels can be used to better control the organization and lineage-specific differentiation of EBs. In this review, we summarize how EB formation is accompanied by a variety of biomechanical parameters that need to be considered for the directed and reproducible self-organization of early cell fate decisions.

Mechanical Cues Affect Migration and Invasion of Cells From Three Different Directions

Cell migration and invasion is a key driving factor for providing essential cellular functions under physiological conditions or the malignant progression of tumors following downward the metastatic cascade. Although there has been plentiful of molecules identified to support the migration and invasion of cells, the mechanical aspects have not yet been explored in a combined and systematic manner. In addition, the cellular environment has been classically and frequently assumed to be homogeneous for reasons of simplicity. However, motility assays have led to various models for migration covering only some aspects and supporting factors that in some cases also include mechanical factors. Instead of specific models, in this review, a more or less holistic model for cell motility in 3D is envisioned covering all these different aspects with a special emphasis on the mechanical cues from a biophysical perspective. After introducing the mechanical aspects of cell migration and invasion and presenting the heterogeneity of extracellular matrices, the three distinct directions of cell motility focusing on the mechanical aspects are presented. These three different directions are as follows: firstly, the commonly used invasion tests using structural and structure-based mechanical environmental signals; secondly, the mechano-invasion assay, in which cells are studied by mechanical forces to migrate and invade; and thirdly, cell mechanics, including cytoskeletal and nuclear mechanics, to influence cell migration and invasion. Since the interaction between the cell and the microenvironment is bi-directional in these assays, these should be accounted in migration and invasion approaches focusing on the mechanical aspects. Beyond this, there is also the interaction between the cytoskeleton of the cell and its other compartments, such as the cell nucleus. In specific, a three-element approach is presented for addressing the effect of mechanics on cell migration and invasion by including the effect of the mechano-phenotype of the cytoskeleton, nucleus and the cell's microenvironment into the analysis. In precise terms, the combination of these three research approaches including experimental techniques seems to be promising for revealing bi-directional impacts of mechanical alterations of the cellular microenvironment on cells and internal mechanical fluctuations or changes of cells on the surroundings. Finally, different approaches are discussed and thereby a model for the broad impact of mechanics on cell migration and invasion is evolved.

Generation of Artificial Gamete and Embryo From Stem Cells in Reproductive Medicine

In addition to the great growing need for assisted reproduction technologies (ART), additional solutions for patients without functional gametes are strongly needed. Due to ethical restrictions, limited studies can be performed on human gametes and embryos; however, artificial gametes and embryos represent a new hope for clinical application and basic research in the field of reproductive medicine. Here, we provide a review of the research progress and possible application of artificial gametes and embryos from different species, including mice, monkeys and humans. Gametes specification from adult stem cells and embryonic stem cells (ESCs) as well as propagation of stem cells from the reproductive system and from organized embryos, which are similar to blastocysts, have been realized in some nonhuman mammals, but not all achievements can be replicated in humans. This area of research remains noteworthy and requires further study and effort to achieve the reconstitution of the entire cycle of gametogenesis and embryo development in vitro.

Understanding embryonic development for cell-based therapies of intervertebral disc degeneration: Toward an effort to treat disc degeneration subphenotypes

Chronic low back and neck pain are associated with intervertebral disc degeneration and are major contributors to the global burden of disability. New evidence now suggests that disc degeneration comprises a spectrum of subphenotypes influenced by genetic background, age, and environmental factors, which may be contributing to the mixed outcomes seen in clinical trials of cell-based therapies that aim to treat disc degeneration. This problem is further compounded by the fact that disc degeneration and aging coincide with an exhaustion of endogenous progenitor cells, imposing limitations on the regenerative capacity of the disc. At the bench-side, current work is focused on applying our knowledge of embryonic disc development to direct and refine differentiation of adult and human-induced pluripotent stem cells into notochord-like and nucleus pulposus-like cells for use in novel cell-based therapies. Accordingly, this review presents the salient features of intervertebral disc development, post-natal maintenance, and regeneration, with emphasis on recent advancements. We also discuss how a stratified approach can be undertaken for the development of future cell-based therapies to bring emerging subphenotypes into consideration.

The effects of macrophages on cardiomyocyte calcium-handling function using in vitro culture models

Following myocardial infarction (MI), myocardial inflammation plays a crucial role in the pathogenesis of MI injury and macrophages are among the key cells activated during the initial phases of the host response regulating the healing process. While macrophages have emerged as attractive effectors in tissue injury and repair, the contribution of macrophages on cardiac cell function and survival is not fully understood due to complexity of the in vivo inflammatory microenvironment. Understanding the key cells involved and how they communicate with one another is of paramount importance for the development of effective clinical treatments. Here, novel in vitro myocardial inflammation models were developed to examine how both direct and indirect interactions with polarized macrophage subsets present in the post-MI microenvironment affect cardiomyocyte function. The indirect model using conditioned medium from polarized macrophage subsets allowed examination of the effects of macrophage-derived factors on stem cell-derived cardiomyocyte function for up to 3 days. The results from the indirect model demonstrated that pro-inflammatory macrophage-derived factors led to a significant downregulation of cardiac troponin T (cTnT) and sarcoplasmic/endoplasmic reticulum calcium ATPase (Serca2) gene expression. It also demonstrated that inhibition of macrophage-secreted matricellular protein, osteopontin (OPN), led to a significant decrease in cardiomyocyte store-operated calcium entry (SOCE). In the direct model, stem cell-derived cardiomyocytes were co-cultured with polarized macrophage subsets for up to 3 days. It was demonstrated that anti-inflammatory macrophages significantly increased cardiomyocyte Ca²⁺ fractional release while macrophages independent of their subtypes led to significant downregulation of SOCE response in cardiomyocytes. This study describes simplified and controlled in vitro myocardial inflammation models, which allow examination of potential beneficial and deleterious effects of macrophages on cardiomyocytes and vise versa. This can lead to our improved understanding of the inflammatory microenvironment post-MI, otherwise difficult to directly investigate in vivo or by using currently available in vitro models.

Generation of Blastocyst-like Structures from Mouse Embryonic and Adult Cell Cultures

A single mouse blastomere from an embryo until the 8-cell stage can generate an entire blastocyst. Whether laboratory-cultured cells retain a similar generative capacity remains unknown. Starting from a single stem cell type, extended pluripotent stem (EPS) cells, we established a 3D differentiation system that enabled the generation of blastocyst-like structures (EPS-blastoids) through lineage segregation and self-organization. EPS-blastoids resembled blastocysts in morphology and cell-lineage allocation and recapitulated key morphogenetic events during preimplantation and early postimplantation development in vitro. Upon transfer, some EPS-blastoids underwent implantation, induced decidualization, and generated live, albeit disorganized, tissues in utero. Single-cell and bulk RNA-sequencing analysis revealed that EPS-blastoids contained all three blastocyst cell lineages and shared transcriptional similarity with natural blastocysts. We also provide proof of concept that EPS-blastoids can be generated from adult cells via cellular reprogramming. EPS-blastoids provide a unique platform for studying early embryogenesis and pave the way to creating viable synthetic embryos by using cultured cells.

Bioengineered microenvironment to culture early embryos

The abnormalities of early post-implantation embryos can lead to early pregnancy loss and many other syndromes. However, it is hard to study embryos after implantation due to the limited accessibility. The success of embryo culture in vitro can avoid the challenges of embryonic development in vivo and provide a powerful research platform for research in developmental biology. The biophysical and chemical cues of the microenvironments impart significant spatiotemporal effects on embryonic development. Here, we summarize the main strategies which enable researchers to grow embryos outside of the body while overcoming the implantation barrier, highlight the roles of engineered microenvironments in regulating early embryonic development, and finally discuss the future challenges and new insights of early embryo culture.

Effects of cigarette smoke components on myocardial differentiation of mouse embryonic stem cells

The heart is the first organ formed in the developing fetus, and abnormal development of the heart is a major cause of fetal death. The adverse effects of cigarette smoke on the heart have been well established, but it is not well understood how cigarette smoke components regulate signaling molecules and cardiac specific functions during the early differentiation stage of the embryonic heart. In this study, we identified changes in the size of mouse embryoid bodies (mEBs) in response to treatment with cigarette smoke extract (CSE) via regulation of HDAC2, p53, p21, and cyclin D1 protein expression, which are cardiac differentiation and cell-cycle markers, respectively. In addition, exposure of mouse embryonic stem cells (mESCs) to cigarette smoke components inhibited myocardial differentiation and development through the expression of HDAC1, HDAC2, GATA4, NKX2-5, TBX5, HAND1, and Troponin I. Long-term exposure studies showed that CSE and nicotine may delay the development of mouse cardiomyocytes from mESCs and inhibit the contractibility, which is a fundamental function of the heart. Taken together, these findings suggest that cigarette smoke components, including nicotine, may affect abnormal myocardial differentiation and development.

Single cell census of human kidney organoids shows reproducibility and diminished off-target cells after transplantation

Human iPSC-derived kidney organoids have the potential to revolutionize discovery, but assessing their consistency and reproducibility across iPSC lines, and reducing the generation of off-target cells remain an open challenge. Here, we profile four human iPSC lines for a total of 450,118 single cells to show how organoid composition and development are comparable to human fetal and adult kidneys. Although cell classes are largely reproducible across time points, protocols, and replicates, we detect variability in cell proportions between different iPSC lines, largely due to off-target cells. To address this, we analyze organoids transplanted under the mouse kidney capsule and find diminished off-target cells. Our work shows how single cell RNA-seq (scRNA-seq) can score organoids for reproducibility, faithfulness and quality, that kidney organoids derived from different iPSC lines are comparable surrogates for human kidney, and that transplantation enhances their formation by diminishing off-target cells.

Single cell census of human kidney organoids shows reproducibility and diminished off-target cells after transplantation

Human iPSC-derived kidney organoids have the potential to revolutionize discovery, but assessing their consistency and reproducibility across iPSC lines, and reducing the generation of off-target cells remain an open challenge. Here, we profile four human iPSC lines for a total of 450,118 single cells to show how organoid composition and development are comparable to human fetal and adult kidneys. Although cell classes are largely reproducible across time points, protocols, and replicates, we detect variability in cell proportions between different iPSC lines, largely due to off-target cells. To address this, we analyze organoids transplanted under the mouse kidney capsule and find diminished off-target cells. Our work shows how single cell RNA-seq (scRNA-seq) can score organoids for reproducibility, faithfulness and quality, that kidney organoids derived from different iPSC lines are comparable surrogates for human kidney, and that transplantation enhances their formation by diminishing off-target cells.

Prediction and control of symmetry breaking in embryoid bodies by environment and signal integration

During early embryogenesis, mechanical constraints and localized biochemical signals co-occur around anteroposterior axis determination and symmetry breaking. Their relative roles, however, are hard to tease apart in vivo Using brachyury (Bra), a primitive streak and mesendoderm marker in mouse embryoid bodies (EBs), we studied how contact, biochemical cues and neighboring cell cues affect the positioning of a primitive streak-like locus and thus determine the anteroposterior axis. We show that a Bra-competent layer must be formed in the EB before Bra expression initiates, and that Bra onset locus position is biased by contact points of the EB with its surrounding, probably through modulation of chemical cues rather than by mechanical signaling. We can push or pull Bra onset away from contact points by introducing a separate localized Wnt signal source, or maneuver Bra onset to a few loci or to an isotropic peripheral pattern. Furthermore, we show that Foxa2-positive cells are predictive of the future location of Bra onset, demonstrating an earlier symmetry-breaking event. Our analysis of factors affecting symmetry breaking and spatial fate choice during this developmental process could prove valuable for in vitro differentiation and organoid formation.

Leveraging Biomaterial Mechanics to Improve Pluripotent Stem Cell Applications for Tissue Engineering

A primary goal in tissue engineering is to develop functional tissues by recapitulating salient features of complex biological systems that exhibit a diverse range of physical forces. Induced pluripotent stem cells (iPSCs) are promising autologous cell sources to execute these developmental programs and their functions; however, cells require an extracellular environment where they will sense and respond to mechanical forces. Thus, understanding the biophysical relationships between stem cells and their extracellular environments will improve the ability to design complex biological systems through tissue engineering. This article first describes how the mechanical properties of the environment are important determinants of developmental processes, and then further details how biomaterials can be designed to precisely control the mechanics of cell-matrix interactions in order to study and define their reprogramming, self-renewal, differentiation, and morphogenesis. Finally, a perspective is presented on how insights from the mechanics of cell-matrix interactions can be leveraged to control pluripotent stem cells for tissue engineering applications.