Heparan sulfate facilitates FGF and BMP signaling to drive mesoderm differentiation of mouse embryonic stem cells

Heparan Sulfate Chain-Conjugated Laminin-E8 Fragments Advance Paraxial Mesodermal Differentiation Followed by High Myogenic Induction from hiPSCs

Human-induced pluripotent stem cells (hiPSCs) have great therapeutic potential. The cell source differentiated from hiPSCs requires xeno-free and robust methods for lineage-specific differentiation. Here, a system is described for differentiating hiPSCs on new generation laminin fragments (NGLFs), a recombinant form of a laminin E8 fragment conjugated to the heparan sulfate chains (HS) attachment domain of perlecan. Using NGLFs, hiPSCs are highly promoted to direct differentiation into a paraxial mesoderm state with high-efficiency muscle lineage generation. HS conjugation to the C-terminus of Laminin E8 fragments brings fibroblast growth factors (FGFs) bound to the HS close to the cell surface of hiPSCs, thereby facilitating stronger FGF signaling pathways stimulation and initiating HOX gene expression, which triggers the paraxial mesoderm differentiation of hiPSCs. This highly efficient differentiation system can provide a roadmap for paraxial mesoderm development and an infinite source of myocytes and muscle stem cells for disease modeling and regenerative medicine.

Vascular Heparan Sulfate and Amyloid-β in Alzheimer's Disease Patients

Alzheimer's disease (AD) is a debilitating neurodegenerative disease characterized by the accumulation of extracellular amyloid-β peptides (Aβ) within the cerebral parenchyma and vasculature, which is known as cerebral amyloid angiopathy (CAA). This study utilized confocal imaging to investigate heparan sulfate (HS) expression within the cerebrovasculature and its associations with Aβ, gender, and ApoE4 genotype in AD. Our investigation revealed elevated levels of HS in the cerebrovasculature of AD patients with severe CAA. Additionally, these patients exhibited higher HS colocalization with Aβ in the cerebrovasculature, including both endothelial and vascular smooth muscle cell compartments. Intriguingly, a reversal in the polarized expression of HS within the cerebrovasculature was detected in AD patients with severe CAA. Furthermore, male patients exhibited lower levels of both parenchymal and cerebrovascular HS. Additionally, ApoE4 carriers displayed heightened cerebrovascular Aβ expression and a tendency of elevated cerebrovascular HS levels in AD patients with severe CAA. Overall, these findings reveal potential intricate interplay between HS, Aβ, ApoE, and vascular pathology in AD, thereby underscoring the potential roles of cerebrovascular HS in CAA development and AD pathology. Further study of the underlying mechanisms may present novel therapeutic avenues for AD treatment.

Glycan Modifications as Regulators of Stem Cell Fate

Glycosylation is a process where proteins or lipids are modified with glycans. The presence of glycans determines the structure, stability, and localization of glycoproteins, thereby impacting various biological processes, including embryogenesis, intercellular communication, and disease progression. Glycans can influence stem cell behavior by modulating signaling molecules that govern the critical aspects of self-renewal and differentiation. Furthermore, being located at the cell surface, glycans are utilized as markers for stem cell pluripotency and differentiation state determination. This review aims to provide a comprehensive overview of the current literature, focusing on the effect of glycans on stem cells with a reflection on the application of synthetic glycans in directing stem cell differentiation. Additionally, this review will serve as a primer for researchers seeking a deeper understanding of how synthetic glycans can be used to control stem cell differentiation, which may help establish new approaches to guide stem cell differentiation into specific lineages. Ultimately, this knowledge can facilitate the identification of efficient strategies for advancing stem cell-based therapeutic interventions.

A precise design strategy for a cell-derived extracellular matrix based on CRISPR/Cas9 for regulating neural stem cell function

The extracellular matrix (ECM) is a natural microenvironment pivotal for stem cell survival, as well as proliferation, differentiation and metastasis, composed of a variety of biological molecular complexes secreted by resident cells in tissues and organs. Heparan sulfate proteoglycan (HSPG) is a type of ECM protein that contains one or more covalently attached heparan sulfate chains. Heparan sulphate chains have high affinity with growth factors, chemokines and morphogens, acting as cytokine-binding domains of great importance in development and normal physiology. Herein, we constructed endogenous HSPG2 overexpression in mouse embryonic fibroblasts based on the CRISPR/Cas9 synergistic activation mediator system and then fabricated a cell-derived HSPG2 functional ECM (ECMHSPG2). The ECMHSPG2 is capable of enriching basic fibroblast growth factor (bFGF), which binds more strongly than the negative control ECM. With a growing bFGF concentration, ECMHSPG2 could better maintain neural stem cell (NSCs) stemness and promote NSC proliferation and differentiation in culture. These findings provide a precise design strategy for producing a specific cell-derived ECM for biomaterials in research and regenerative medicine.

A Spatiotemporal Compartmentalization of Glucose Metabolism Guides Mammalian Gastrulation Progression

Gastrulation is considered the sine qua non of embryogenesis, establishing a multidimensional structure and the spatial coordinates upon which all later developmental events transpire. At this time, the embryo adopts a heavy reliance on glucose metabolism to support rapidly accelerating changes in morphology, proliferation, and differentiation. However, it is currently unknown how this conserved metabolic shift maps onto the three-dimensional landscape of the growing embryo and whether it is spatially linked to the orchestrated cellular and molecular processes necessary for gastrulation. Here we identify that glucose is utilised during mouse gastrulation via distinct metabolic pathways to instruct local and global embryonic morphogenesis, in a cell type and stage-specific manner. Through detailed mechanistic studies and quantitative live imaging of mouse embryos, in parallel with tractable in vitro stem cell differentiation models and embryo-derived tissue explants, we discover that cell fate acquisition and the epithelial-to-mesenchymal transition (EMT) relies on the Hexosamine Biosynthetic Pathway (HBP) branch of glucose metabolism, while newly-formed mesoderm requires glycolysis for correct migration and lateral expansion. This regional and tissue-specific difference in glucose metabolism is coordinated with Fibroblast Growth Factor (FGF) activity, demonstrating that reciprocal crosstalk between metabolism and growth factor signalling is a prerequisite for gastrulation progression. We expect these studies to provide important insights into the function of metabolism in other developmental contexts and may help uncover mechanisms that underpin embryonic lethality, cancer, and congenital disease.

Human iPSC-derived brain organoids: A 3D mini-brain model for studying HIV infection

The brain is one of the important reservoir sites for HIV persistent/latent infection that often leads to HIV-associated neurocognitive disorders (HAND). However, HIV dynamics in the brain is an understudied area and little is known about mechanisms underlying the development and progression of HAND. This issue is mainly due to the lack of suitable in vitro models that can recapitulate the cellular and molecular complexity of the human brain. Hence, there is an urgent need for such models to study HIV neuropathogenesis and to develop therapeutics for HAND. The emergence of three-dimensional (3D) brain organoids generated from induced pluripotent stem cells (iPSCs) has now provided a clinically relevant in vitro model to study HIV brain infection and neuropathogenesis. Recently, there have been a noticeable number of publications that demonstrate the feasibility and advantages of this model for studies of neurobiology and brain disorders as well as HIV infection. Here, we describe the development of iPSC-derived human microglia-containing brain organoids, including advantages/challenges, and focus on their applicability for modeling HIV brain infection.

Heparan sulfate proteoglycan in Alzheimer's disease: aberrant expression and functions in molecular pathways related to amyloid-β metabolism

Alzheimer's disease (AD) is the most common form of dementia. Currently, there is no effective treatment for AD, as its etiology remains poorly understood. Mounting evidence suggests that the accumulation and aggregation of amyloid-β peptides (Aβ), which constitute amyloid plaques in the brain, is critical for initiating and accelerating AD pathogenesis. Considerable efforts have been dedicated to shedding light on the molecular basis and fundamental origins of the impaired Aβ metabolism in AD. Heparan sulfate (HS), a linear polysaccharide of the glycosaminoglycan family, co-deposits with Aβ in plaques in the AD brain, directly binds and accelerates Aβ aggregation, and mediates Aβ internalization and cytotoxicity. Mouse model studies demonstrate that HS regulates Aβ clearance and neuroinflammation in vivo. Previous reviews have extensively explored these discoveries. Here, this review focuses on the recent advancements in understanding abnormal HS expression in the AD brain, the structural aspects of HS-Aβ interaction, and the molecules involved in modulating Aβ metabolism through HS interaction. Furthermore, this review presents a perspective on the potential effects of abnormal HS expression on Aβ metabolism and AD pathogenesis. In addition, the review highlights the importance of conducting further research to differentiate the spatiotemporal components of HS structure and function in the brain and AD pathogenesis.

Heparan sulfate proteoglycans in cancer: Pathogenesis and therapeutic potential

The heparan sulfate proteoglycans (HSPGs) are glycoproteins that consist of a proteoglycan "core" protein and covalently attached heparan sulfate (HS) chain. HSPGs are ubiquitously expressed in mammalian cells on the cell surface and in the extracellular matrix (ECM) and secretory vesicles. Within HSPGs, the protein cores determine when and where HSPG expression takes place, and the HS chains mediate most of HSPG's biological roles through binding various protein ligands, including cytokines, chemokines, growth factors and receptors, morphogens, proteases, protease inhibitors, and ECM proteins. Through these interactions, HSPGs modulate cell proliferation, adhesion, migration, invasion, and angiogenesis to display essential functions in physiology and pathology. Under physiological conditions, the expression and localization of HSPGs are finely regulated to orchestrate their physiological functions, and this is disrupted in cancer. The HSPG dysregulation elicits multiple oncogenic signaling, including growth factor signaling, ECM and Integrin signaling, chemokine and immune signaling, cancer stem cell, cell differentiation, apoptosis, and senescence, to prompt cell transformation, proliferation, tumor invasion and metastasis, tumor angiogenesis and inflammation, and immunotolerance. These oncogenic roles make HSPGs an attractive pharmacological target for anti-cancer therapy. Several therapeutic strategies have been under development, including anti-HSPG antibodies, peptides and HS mimetics, synthetic xylosides, and heparinase inhibitors, and shown promising anti-cancer efficacy. Therefore, much progress has been made in this line of study. However, it needs to bear in mind that the roles of HSPGs in cancer can be either oncogenic or tumor-suppressive, depending on the HSPG and the cancer cell type with the underlying mechanisms that remain obscure. Further studies need to address these to fill the knowledge gap and rationalize more efficient therapeutic targeting.

Regulation of stem cell fate by HSPGs: implication in hair follicle cycling

Heparan sulfate proteoglycans (HSPGs) are part of proteoglycan family. They are composed of heparan sulfate (HS)-type glycosaminoglycan (GAG) chains covalently linked to a core protein. By interacting with growth factors and/or receptors, they regulate numerous pathways including Wnt, hedgehog (Hh), bone morphogenic protein (BMP) and fibroblast growth factor (FGF) pathways. They act as inhibitor or activator of these pathways to modulate embryonic and adult stem cell fate during organ morphogenesis, regeneration and homeostasis. This review summarizes the knowledge on HSPG structure and classification and explores several signaling pathways regulated by HSPGs in stem cell fate. A specific focus on hair follicle stem cell fate and the possibility to target HSPGs in order to tackle hair loss are discussed in more dermatological and cosmeceutical perspectives.

Neural progenitor cell-derived extracellular matrix as a new platform for neural differentiation of human induced pluripotent stem cells

The culture microenvironment has been demonstrated to regulate stem cell fate and to be a crucial aspect for quality-controlled stem cell maintenance and differentiation to a specific lineage. In this context, extracellular matrix (ECM) proteins are particularly important to mediate the interactions between the cells and the culture substrate. Human induced pluripotent stem cells (hiPSCs) are usually cultured as anchorage-dependent cells and require adhesion to an ECM substrate to support their survival and proliferation in vitro. Matrigel, a common substrate for hiPSC culture is a complex and undefined mixture of ECM proteins which are expensive and not well suited to clinical application. Decellularized cell-derived ECM has been shown to be a promising alternative to the common protein coatings used in stem cell culture. However, very few studies have used this approach as a niche for neural differentiation of hiPSCs. Here, we developed a new stem cell culture system based on decellularized cell-derived ECM from neural progenitor cells (NPCs) for expansion and neural differentiation of hiPSCs, as an alternative to Matrigel and poly-l-ornithine/laminin-coated well plates. Interestingly, hiPSCs were able to grow and maintain their pluripotency when cultured on decellularized ECM from NPCs (NPC ECM). Furthermore, NPC ECM enhanced the neural differentiation of hiPSCs compared to poly-l-ornithine/laminin-coated wells, which are used in most neural differentiation protocols, presenting a statistically significant enhancement of neural gene expression markers, such as βIII-Tubulin and MAP2. Taken together, our results demonstrate that NPC ECM provides a functional microenvironment, mimicking the neural niche, which may have interesting future applications for the development of new strategies in neural stem cell research.

Pentosan Polysulphate (PPS), a Semi-Synthetic Heparinoid DMOAD With Roles in Intervertebral Disc Repair Biology emulating The Stem Cell Instructive and Tissue Reparative Properties of Heparan Sulphate

This review highlights the attributes of pentosan polysulphate (PPS) in the promotion of intervertebral disc (IVD) repair processes. PPS has been classified as a disease modifying osteoarthritic drug (DMOAD) and many studies have demonstrated its positive attributes in the countering of degenerative changes occurring in cartilaginous tissues during the development of osteoarthritis (OA). Degenerative changes in the IVD also involve inflammatory cytokines, degradative proteases and cell signalling pathways similar to those operative in the development of OA in articular cartilage. PPS acts as a heparan sulphate (HS) mimetic to effect its beneficial effects in cartilage. The IVD contains small cell membrane HS-proteoglycans (HSPGs) such as syndecan, and glypican and a large multifunctional HS/chondroitin sulphate (CS) hybrid proteoglycan (HSPG2/perlecan) that have important matrix stabilising properties and sequester, control and present growth factors from the FGF, VEGF, PDGF and BMP families to cellular receptors to promote cell proliferation, differentiation and matrix synthesis. HSPG2 also has chondrogenic properties and stimulates the synthesis of extracellular matrix (ECM) components, expansion of cartilaginous rudiments and has roles in matrix stabilisation and repair. Perlecan is a perinuclear and nuclear proteoglycan in IVD cells with roles in chromatin organisation and control of transcription factor activity, immunolocalises to stem cell niches in cartilage, promotes escape of stem cells from quiescent recycling, differentiation and attainment of pluripotency and migratory properties. These participate in tissue development and morphogenesis, ECM remodelling and repair. PPS also localises in the nucleus of stromal stem cells, promotes development of chondroprogenitor cell lineages, ECM synthesis and repair and discal repair by resident disc cells. The availability of recombinant perlecan and PPS offer new opportunities in repair biology. These multifunctional agents offer welcome new developments in repair strategies for the IVD.

Proteoglycans and Glycosaminoglycans in Stem Cell Homeostasis and Bone Tissue Regeneration

Stem cells maintain a subtle balance between self-renewal and differentiation under the regulatory network supported by both intracellular and extracellular components. Proteoglycans are large glycoproteins present abundantly on the cell surface and in the extracellular matrix where they play pivotal roles in facilitating signaling transduction and maintaining stem cell homeostasis. In this review, we outline distinct proteoglycans profiles and their functions in the regulation of stem cell homeostasis, as well as recent progress and prospects of utilizing proteoglycans/glycosaminoglycans as a novel glycomics carrier or bio-active molecules in bone regeneration.

Dermatan-4-O-Sulfotransferase-1 Contributes to the Undifferentiated State of Mouse Embryonic Stem Cells

Mouse embryonic stem cells (mESCs) have the properties of self-renewal and pluripotency. Various signals and growth factors maintain their undifferentiated state and also regulate their differentiation. Glycosaminoglycans are present on the cell surface and in the cell matrix as proteoglycans. Previously, we and other groups reported that the glycosaminoglycan heparan sulfate contributes to both maintenance of undifferentiated state and regulation of mESC differentiation. It has been shown that chondroitin sulfate is needed for pluripotency and differentiation of mESCs, while keratan sulfate is a known marker of human ESCs or induced pluripotent stem cells. We also found that DS promotes neuronal differentiation from mESCs and human neural stem cells; however, the function of DS in the maintenance of mESCs has not yet been revealed. Here, we investigated the role of DS in mESCs by knockdown (KD) or overexpression (O/E) of the dermatan-4-O-sulfotransferase-1 (D4ST1) gene. We found that the activity of the ESC self-renewal marker alkaline phosphatase was reduced in D4ST1 KD mESCs, but, in contrast, increased in D4ST1 O/E mESCs. D4ST1 KD promoted endodermal differentiation, as indicated by an increase in Cdx2 expression. Conversely, Cdx2 expression was decreased by D4ST1 O/E. Wnt signaling, which is also involved in endodermal differentiation, was activated by D4ST1 KD and suppressed by D4ST1 O/E. Collectively, these results demonstrate that D4ST1 contributes to the undifferentiated state of mESCs. Our findings provide new insights into the function of DS in mESCs.

Heparan sulfate inhibits transforming growth factor β signaling and functions in cis and in trans to regulate prostate stem/progenitor cell activities

Prostate stem/progenitor cells (PrSCs) are responsible for adult prostate tissue homeostasis and regeneration. However, the related regulatory mechanisms are not completely understood. In this study, we examined the role of heparan sulfate (HS) in PrSC self-renewal and prostate regeneration. Using an in vitro prostate sphere formation assay, we found that deletion of the glycosyltransferase exostosin 1 (Ext1) abolished HS expression in PrSCs and disrupted their ability to self-renew. In associated studies, we observed that HS loss inhibited p63 and CK5 expression, reduced the number of p63+- or CK5+-expressing stem/progenitor cells, elevated CK8+ expression and the number of differentiated CK8+ luminal cells and arrested the spheroid cells in the G1/G0 phase of cell cycle. Mechanistically, HS expressed by PrSCs (in cis) or by neighboring cells (in trans) could maintain sphere formation. Furthermore, HS deficiency upregulated transforming growth factor β (TGFβ) signaling and inhibiting TGFβ signaling partially restored the sphere-formation activity of the HS-deficient PrSCs. In an in vivo prostate regeneration assay, simultaneous loss of HS in both epithelial cell and stromal cell compartments attenuated prostate tissue regeneration, whereas the retention of HS expression in either of the two cellular compartments was sufficient to sustain prostate tissue regeneration. We conclude that HS preserves self-renewal of adult PrSCs by inhibiting TGFβ signaling and functions both in cis and in trans to maintain prostate homeostasis and to support prostate regeneration.

Heparan Sulfate Facilitates Spike Protein-Mediated SARS-CoV-2 Host Cell Invasion and Contributes to Increased Infection of SARS-CoV-2 G614 Mutant and in Lung Cancer

The severe acute respiratory syndrome (SARS)-like coronavirus disease (COVID-19) is caused by SARS-CoV-2 and has been a serious threat to global public health with limited treatment. Cellular heparan sulfate (HS) has been found to bind SARS-CoV-2 spike protein (SV2-S) and co-operate with cell surface receptor angiotensin-converting enzyme 2 (ACE2) to mediate SARS-CoV-2 infection of host cells. In this study, we determined that host cell surface SV2-S binding depends on and correlates with host cell surface HS expression. This binding is required for SARS-Cov-2 virus to infect host cells and can be blocked by heparin lyase, HS antagonist surfen, heparin, and heparin derivatives. The binding of heparin/HS to SV2-S is mainly determined by its overall sulfation with potential, minor contribution of specific SV2-S binding motifs. The higher binding affinity of SV2-S G614 mutant to heparin and upregulated HS expression may be one of the mechanisms underlying the higher infectivity of the SARS-CoV-2 G614 variant and the high vulnerability of lung cancer patients to SARS-CoV-2 infection, respectively. The higher host cell infection by SARS-CoV-2 G614 variant pseudovirus and the increased infection caused by upregulated HS expression both can be effectively blocked by heparin lyase and heparin, and possibly surfen and heparin derivatives too. Our findings support blocking HS-SV2-S interaction may provide one addition to achieve effective prevention and/treatment of COVID-19.

Dermatan sulphate promotes neuronal differentiation in mouse and human stem cells

Dermatan sulphate (DS), a glycosaminoglycan, is present in the extracellular matrix and on the cell surface. Previously, we showed that heparan sulphate plays a key role in the maintenance of the undifferentiated state in mouse embryonic stem cells (mESCs) and in the regulation of their differentiation. Chondroitin sulphate has also been to be important for pluripotency and differentiation of mESCs. Keratan sulphate is a marker of human pluripotent stem cells. To date, however, the function of DS in mESCs has not been clarified. Dermatan 4 sulfotransferase 1, which transfers sulphate to the C-4 hydroxyl group of N-acetylgalactosamine of DS, contributes to neuronal differentiation of mouse neural progenitor cells. Therefore, we anticipated that neuronal differentiation would be induced in mESCs in culture by the addition of DS. To test this expectation, we investigated neuronal differentiation in mESCs and human neural stem cells (hNSCs) cultures containing DS. In mESCs, DS promoted neuronal differentiation by activation of extracellular signal-regulated kinase 1/2 and also accelerated neurite outgrowth. In hNSCs, DS promoted neuronal differentiation and neuronal migration, but not neurite outgrowth. Thus, DS promotes neuronal differentiation in both mouse and human stem cells, suggesting that it offers a novel method for efficiently inducing neuronal differentiation.

An analysis of osteoporosis in patients with hereditary multiple exostoses

We analyzed osteoporosis in 20 HME patients. According to the T-score of BMD, 30% and 67.5% of the patients fell in the range of osteopenia in the lumbar spine and femoral neck. Our results indicate HME patients have low bone mass. They do not have abnormal bone metabolism.

INTRODUCTION

There are few reports of osteoporosis in hereditary multiple exostoses (HME) patients. Therefore, the purpose of this study was to analyze osteoporosis in HME patients.

METHODS

This retrospective cohort study included 20 patients diagnosed with HME. Patients underwent bone mineral density (BMD) measurement of the lumbar spine (n = 20) and femoral neck (n = 40). Bone metabolic parameters, including serum osteocalcin and urinary cross-linked N-telopeptide of type 1 collagen (NTx), were analyzed in all subjects. EXT1 and EXT2 genes were sequenced using genomic DNA. We also examined the correlation between genotype and BMD Z-score and T-score.

RESULTS

The mean BMD values of the lumbar spine were 1.085 ± 0.116 g/cm² (n = 11) in male and 1.108 ± 0.088 g/cm² (n = 9) in female. The mean BMD values of the femoral neck area were 0.759 ± 0.125 g/cm² (n = 22) in male and 0.749 ± 0.115 g/cm² (n = 18) in female. Z-score of most HME patients show < 0, indicating that these patients tend to have low bone mass compared with the age-matched population. According to the T-score of BMD, 30% (6 of 20) and 67.5% (27 of 40) of the patients fell in the range of osteopenia in the lumbar spine and femoral neck areas, respectively. Serum osteocalcin and urinary NTx were in the normal range in most patients. There was no significant correlation between genotypes and Z-score.

CONCLUSION

HME patients have low bone mass, especially in the femoral neck area. They do not have abnormal bone metabolism, and there was no correlation between genotypes and Z-score.

Heparan Sulfate Proteoglycans: Key Mediators of Stem Cell Function

Heparan sulfate proteoglycans (HSPGs) are an evolutionarily ancient subclass of glycoproteins with exquisite structural complexity. They are ubiquitously expressed across tissues and have been found to exert a multitude of effects on cell behavior and the surrounding microenvironment. Evidence has shown that heterogeneity in HSPG composition is crucial to its functions as an essential scaffolding component in the extracellular matrix as well as a vital cell surface signaling co-receptor. Here, we provide an overview of the significance of HSPGs as essential regulators of stem cell function. We discuss the various roles of HSPGs in distinct stem cell types during key physiological events, from development through to tissue homeostasis and regeneration. The contribution of aberrant HSPG production to altered stem cell properties and dysregulated cellular homeostasis characteristic of cancer is also reviewed. Finally, we consider approaches to better understand and exploit the multifaceted functions of HSPGs in influencing stem cell characteristics for cell therapy and associated culture expansion strategies.

Heparin mimics and fibroblast growth factor-2 fabricated nanogold composite in promoting neural differentiation of mouse embryonic stem cells

The replacement therapy or transplantation using neural cells, which differentiated from stem cells, has emerged as a promising strategy for repairing damaged neural tissues and helping functional recovery in the treatment of neural system diseases. The challenge, however, is how to control embryonic stem cell fate so that neural differentiation can be efficiently directed to enrich a neuron cell population, and meanwhile to maintain their bioactivities. This is a key question and has a very significant impact in regenerative medicine. Here we proposed a new neural-differentiation inductive nanocomposite, containing gold nanoparticles (AuNPs), poly(2-methacrylamido glucopyranose-co-3-sulfopropyl acrylate) (PMS), and basic fibroblast growth factor (FGF2), for the high efficient directional neural-specific differentiation of mouse embryonic stem cells (mESCs). In this AuNP-PMS/FGF2 composite, PMS, playing as the high-active mimic of heparin/heparan sulfate (HS), is covalently anchored to AuNPs and bound with FGF2 on the surface of nanoparticles, forming a HS/FGF2 complex nanomimics to facilitate its binding to FGF receptor (FGFR) and promote high neural-inductive activity of mESCs. The stability, bioactivity and biocompatibility of the composite are investigated in this study. The results showed that the AuNP-PMS/FGF2 composite could maintain a long-term stability at room temperature for at least 8 days, and greatly promote the neural differentiation of mESCs. Compared with the other materials, the AuNP-PMS/FGF2 composite could significantly stimulate the expression of the specific neural differentiation markers (nestin and β3-tubulin), while obviously down-regulate the mRNA production of pluripotency marker Oct-4 in mESCs. Moreover, the promotion effect of the composite on neuronal maturation marker β3-tubulin expression achieved maximally at the low concentration of FGF2 (4 ng/mL), which suggested the high efficiency of AuNP-PMS/FGF2 composite in neural differentiation of mESCs. Meanwhile, both mESCs and L929 cells showed desirable growth during the incubation with AuNP-PMS/FGF2 composite. The AuNP-PMS/FGF2 system presents a new way to achieve HS/FGF2 complex nanomimics efficiently for the neural differentiation of mESCs.

Heparanase promotes myeloma stemness and in vivo tumorigenesis

Heparanase is known to enhance the progression of many cancer types and is associated with poor patient prognosis. We recently reported that after patients with multiple myeloma were treated with high dose chemotherapy, the tumor cells that emerged upon relapse expressed a much higher level of heparanase than was present prior to therapy. Because tumor cells having stemness properties are thought to seed tumor relapse, we investigated whether heparanase had a role in promoting myeloma stemness. When plated at low density and grown in serum-free conditions that support survival and expansion of stem-like cells, myeloma cells expressing a low level of heparanase formed tumor spheroids poorly. In contrast, cells expressing a high level of heparanase formed significantly more and larger spheroids than did the heparanase low cells. Importantly, heparanase-low expressing cells exhibited plasticity and were induced to exhibit stemness properties when exposed to recombinant heparanase or to exosomes that contained a high level of heparanase cargo. The spheroid-forming heparanase-high cells had elevated expression of GLI1, SOX2 and ALDH1A1, three genes known to be associated with myeloma stemness. Inhibitors that block the heparan sulfate degrading activity of heparanase significantly diminished spheroid formation and expression of stemness genes implying a direct role of the enzyme in regulating stemness. Blocking the NF-κB pathway inhibited spheroid formation and expression of stemness genes demonstrating a role for NF-κB in heparanase-mediated stemness. Myeloma cells made deficient in heparanase exhibited decreased stemness properties in vitro and when injected into mice they formed tumors poorly compared to the robust tumorigenic capacity of cells expressing higher levels of heparanase. These studies reveal for the first time a role for heparanase in promoting cancer stemness and provide new insight into its function in driving tumor progression and its association with poor prognosis in cancer patients.

Heparan sulfate proteoglycans: The sweet side of development turns sour in mucopolysaccharidoses

Heparan sulfate proteoglycans (HSPGs) are complex carbohydrate-modified proteins ubiquitously expressed on cell surfaces, extracellular matrix and basement membrane of mammalian tissues. Beside to serve as structural constituents, they regulate multiple cellular activities. A critical involvement of HSPGs in development has been established, and perturbations of HSPG-dependent pathways are associated with many human diseases. Recent evidence suggest a role of HSPGs in the pathogenesis of mucopolysaccharidoses (MPSs) where the accumulation of undigested HS results in the loss of cellular functions, tissue damage and organ dysfunctions accounting for clinical manifestations which include central nervous system (CNS) involvement, degenerative joint disease and reduced bone growth. Current therapies are not curative but only ameliorate the disease symptoms. Here, we highlight the link between HSPG functions in the development of CNS and musculoskeletal structures and the etiology of some MPS phenotypes, suggesting that HSPGs may represent potential targets for the therapy of such incurable diseases.

Highly sulfated hyaluronic acid maintains human induced pluripotent stem cells under feeder-free and bFGF-free conditions

Human induced pluripotent stem (hiPS) cells are attracting attention as a tool for regenerative medicine. However, several problems need to be overcome for their widespread and safe use, for example, the high cost of maintaining hiPS cells and the possibility of xenogeneic cell contamination in hiPS cell cultures. One of the main contributors to the high cost of maintaining hiPS cells is basic fibroblast growth factor (bFGF), which is essential for such cultures. Xenogeneic contamination can occur because of the use of mouse-derived feeder cells to culture hiPS cells. To overcome the problems of cell culture cost and xenogeneic contamination, we have developed a novel culture method in which the undifferentiated state and pluripotency of hiPS cells can be maintained under feeder-free and bFGF-free conditions. Our new approach involves the addition to the culture medium of highly sulfated hyaluronic acid (HA-HS), in which the hydroxyl groups of d-glucuronic acid (GlcA) and N-acetyl-d-glucosamine (GlcNAc) are chemically sulfated. HA-HS promotes bFGF signaling and maintains the undifferentiated state and pluripotency of hiPS cells under feeder-free and bFGF-free conditions. By contrast, non-sulfated hyaluronic acid and low sulfated hyaluronic acid do not maintain the undifferentiated state and pluripotency of hiPS cells. These results indicate that the maintenance of hiPS cells under feeder-free and bFGF-free conditions is an HA-HS specific effect. This study is the first to demonstrate the effects of sulfated hyaluronic acid on mammalian pluripotent stem cells, and provides a novel method for maintaining hiPS cells using HA-HS.

Proteoglycans and glycosaminoglycans as regulators of cancer stem cell function and therapeutic resistance

In contrast to the bulk of the tumor, a subset of cancer cells called cancer stem cells (CSC; or tumor-initiating cells) is characterized by self-renewal, unlimited proliferative potential, expression of multidrug resistance proteins, active DNA repair capacity, apoptosis resistance, and a considerable developmental plasticity. Due to these properties, CSCs display increased resistance to chemo- and radiotherapy. Recent findings indicate that aberrant functions of proteoglycans (PGs) and glycosaminoglycans (GAGs) contribute substantially to the CSC phenotype and therapeutic resistance. In this review, we summarize how the diverse functions of the glycoproteins and carbohydrates facilitate acquisition and maintenance of the CSC phenotype, and how this knowledge can be exploited to develop novel anticancer therapies. For example, the large transmembrane chondroitin sulfate PG NG2/CSPG4 marks stem cell (SC) populations in brain tumors. Cell surface heparan sulfate PGs of the syndecan and glypican families modulate the stemness-associated Wnt, hedgehog, and notch signaling pathways, whereas the interplay of hyaluronan in the SC niche with CSC CD44 determines the maintenance of stemness and promotes therapeutic resistance. A better understanding of the molecular mechanisms by which PGs and GAGs regulate CSC function will aid the development of targeted therapeutic approaches which could avoid relapse after an otherwise successful conventional therapy. Chimeric antigen receptor T cells, PG-primed dendritic cells, PG-targeted antibody-drug conjugates, and inhibitory peptides and glycans have already shown highly promising results in preclinical models.

Modeling large protein-glycosaminoglycan complexes using a fragment-based approach

Glycosaminoglycans (GAGs), a major constituent of the extracellular matrix, participate in cell-signaling by binding specific proteins. Structural data on protein-GAG interactions are crucial to understand and modulate these signaling processes, with potential applications in regenerative medicine. However, experimental and theoretical approaches used to study GAG-protein systems are challenged by GAGs high flexibility limiting the conformational sampling above a certain size, and by the scarcity of GAG-specific docking tools compared to protein-protein or protein-drug docking approaches. We present for the first time an automated fragment-based method for docking GAGs on a protein binding site. In this approach, trimeric GAG fragments are flexibly docked to the protein, assembled based on their spacial overlap, and refined by molecular dynamics. The method appeared more successful than the classical full-ligand approach for most of 13 tested complexes with known structure. The approach is particularly promising for docking of long GAG chains, which represents a bottleneck for classical docking approaches applied to these systems. © 2019 Wiley Periodicals, Inc.

Silencing glycosaminoglycan functions in mouse embryonic stem cells with small molecule antagonists

Glycosylation is a ubiquitous post-translational modification that decorates proteins and lipids with glycans. These glycans can play critical roles in regulating biological events, and therefore, the discovery of strategies that target these molecules represent an important advancement toward understanding and controlling glycan-mediated cellular phenotypes. We describe the use of a small molecule, surfen, to temporarily silence the functions mediated by heparan sulfate glycosaminoglycans in mouse embryonic stem cells. Surfen binds heparan sulfate to antagonize growth factor interactions, thereby inhibiting signal transduction events that lead to differentiation. The strategies outlined in this chapter allow the characterization of resulting antagonistic effects caused by glycan-small molecule binding events toward maintaining embryonic stem cell pluripotency, curbing differentiation, and inhibiting signaling events.

A mutant-cell library for systematic analysis of heparan sulfate structure-function relationships

Heparan sulfate (HS) is a complex linear polysaccharide that modulates a wide range of biological functions. Elucidating the structure-function relationship of HS has been challenging. Here we report the generation of an HS-mutant mouse lung endothelial cell library by systematic deletion of HS genes expressed in the cell. We used this library to (1) determine that the strictly defined fine structure of HS, not its overall degree of sulfation, is more important for FGF2-FGFR1 signaling; (2) define the epitope features of commonly used anti-HS phage display antibodies; and (3) delineate the fine inter-regulation networks by which HS genes modify HS and chain length in mammalian cells at a cell-type-specific level. Our mutant-cell library will allow robust and systematic interrogation of the roles and related structures of HS in a cellular context.

Embryonic Stem Cell Engineering with a Glycomimetic FGF2/BMP4 Co-Receptor Drives Mesodermal Differentiation in a Three-Dimensional Culture

Cell surface glycans, such as heparan sulfate (HS), are increasingly identified as co-regulators of growth factor signaling in early embryonic development; therefore, chemical tailoring of HS activity within the cellular glycocalyx of stem cells offers an opportunity to control their differentiation. The growth factors FGF2 and BMP4 are involved in mediating the exit of murine embryonic stem cells (mESCs) from their pluripotent state and their differentiation toward mesodermal cell types, respectively. Here, we report a method for remodeling the glycocalyx of mutant Ext1^-/- mESCs with defective biosynthesis of HS to drive their mesodermal differentiation in an embryoid body culture. Lipid-functionalized synthetic HS-mimetic glycopolymers with affinity for both FGF2 and BMP4 were introduced into the plasma membrane of Ext1^-/- mESCs, where they acted as functional co-receptors of these growth factors and facilitated signal transduction through associated MAPK and Smad signaling pathways. We demonstrate that these materials can be employed to remodel Ext1^-/- mESCs within three-dimensional embryoid body structures, providing enhanced association of BMP4 at the cell surface and driving mesodermal differentiation. As a more complete understanding of the function of HS in regulating development continues to emerge, this simple glycocalyx engineering method is poised to enable precise control over growth factor signaling activity and outcomes of differentiation in stem cells.

Multiple roles of epithelial heparan sulfate in stomach morphogenesis

Heparan sulfate proteoglycans (HSPGs) have been shown to regulate various developmental processes. However, the function of heparan sulfate (HS) during the development of mammalian stomach has not been characterized yet. Here, we investigate the role of epithelial HS in embryonic stomach by examining mice deficient in the glycosyltransferase gene Ext1 We show that HS exhibits a specific and dynamic expression pattern in mouse embryonic stomach. Depletion of the epithelial HS leads to stomach hypoplasia, with phenotypic differences in the gastric mucosa between the forestomach and hindstomach. In the posterior stomach, HS depletion disrupts glandular stomach patterning and cytodifferentiation via attenuation of Fgf signaling activity. Inhibition of Fgf signaling in vitro recapitulates the patterning defect. Ligand and carbohydrate engagement assay (LACE) reveals a diminished assembly of Fgf10 and Fgfr2b in the mutant. In the anterior stomach, loss of epithelial HS leads to stratification and differentiation defects of the multilayered squamous epithelium, along with reduced Hh and Bmp signaling activity. Our data demonstrate that epithelial HS plays multiple roles in regulating mammalian stomach morphogenesis in a regional-specific manner.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

Heparin, Heparan Sulphate and the TGF-β Cytokine Superfamily

Of the circa 40 cytokines of the TGF-β superfamily, around a third are currently known to bind to heparin and heparan sulphate. This includes TGF-β1, TGF-β2, certain bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs), as well as GDNF and two of its close homologues. Experimental studies of their heparin/HS binding sites reveal a diversity of locations around the shared cystine-knot protein fold. The activities of the TGF-β cytokines in controlling proliferation, differentiation and survival in a range of cell types are in part regulated by a number of specific, secreted BMP antagonist proteins. These vary in structure but seven belong to the CAN or DAN family, which shares the TGF-β type cystine-knot domain. Other antagonists are more distant members of the TGF-β superfamily. It is emerging that the majority, but not all, of the antagonists are also heparin binding proteins. Any future exploitation of the TGF-β cytokines in the therapy of chronic diseases will need to fully consider their interactions with glycosaminoglycans and the implications of this in terms of their bioavailability and biological activity.

EXTL3 mutations cause skeletal dysplasia, immune deficiency, and developmental delay

Volpi et al. demonstrate that hypomorphic EXTL3 mutations cause abnormalities of heparan sulfate composition, affect signaling in response to growth factors and cytokines, and perturb thymopoiesis, resulting in a novel genetic disease associating skeletal dysplasia, T cell immunodeficiency, and neurodevelopmental delay.

We studied three patients with severe skeletal dysplasia, T cell immunodeficiency, and developmental delay. Whole-exome sequencing revealed homozygous missense mutations affecting exostosin-like 3 (EXTL3), a glycosyltransferase involved in heparan sulfate (HS) biosynthesis. Patient-derived fibroblasts showed abnormal HS composition and altered fibroblast growth factor 2 signaling, which was rescued by overexpression of wild-type EXTL3 cDNA. Interleukin-2–mediated STAT5 phosphorylation in patients’ lymphocytes was markedly reduced. Interbreeding of the extl3-mutant zebrafish (box) with Tg(rag2:green fluorescent protein) transgenic zebrafish revealed defective thymopoiesis, which was rescued by injection of wild-type human EXTL3 RNA. Targeted differentiation of patient-derived induced pluripotent stem cells showed a reduced expansion of lymphohematopoietic progenitor cells and defects of thymic epithelial progenitor cell differentiation. These data identify EXTL3 mutations as a novel cause of severe immune deficiency with skeletal dysplasia and developmental delay and underline a crucial role of HS in thymopoiesis and skeletal and brain development.

Hydrophilic cell-derived extracellular matrix as a niche to promote adhesion and differentiation of neural progenitor cells

Cell-derived extracellular matrix exhibits excellent adhesion performance for neural progenitor cell anchoring and residency, resulting in promoted proliferation of the stem cells to basal forebrain cholinergic neurons.

Glycosylation and stem cells: Regulatory roles and application of iPSCs in the study of glycosylation-related disorders

Glycosylation refers to the co- and post-translational modification of protein and lipids by monosaccharides or oligosaccharide chains. The surface of mammalian cells is decorated by a heterogeneous and highly complex array of protein and lipid linked glycan structures that vary significantly between different cell types, raising questions about their roles in development and disease pathogenesis. This review will begin by focusing on recent findings that define roles for cell surface protein and lipid glycosylation in pluripotent stem cells and their functional impact during normal development. Then, we will describe how patient derived induced pluripotent stem cells are being used to model human diseases such as congenital disorders of glycosylation. Collectively, these studies indicate that cell surface glycans perform critical roles in human development and disease.

Glycan Engineering for Cell and Developmental Biology

Cell-surface glycans are a diverse class of macromolecules that participate in many key biological processes, including cell-cell communication, development, and disease progression. Thus, the ability to modulate the structures of glycans on cell surfaces provides a powerful means not only to understand fundamental processes but also to direct activity and elicit desired cellular responses. Here, we describe methods to sculpt glycans on cell surfaces and highlight recent successes in which artificially engineered glycans have been employed to control biological outcomes such as the immune response and stem cell fate.

Glycans define the stemness of naïve and primed pluripotent stem cells

Cell surface glycans are tissue-specific and developmentally regulated. They function as essential modulators in cell-cell interactions, cell-extracellular matrix interactions, and ligand-receptor interactions, binding to various ligands, including Wnt, fibroblast growth factors, and bone morphogenetic proteins. Embryonic stem (ES) cells, originally derived from the inner cell mass of blastocysts, have the essential characteristics of pluripotency and self-renewal. Recently, it has been proposed that mouse and human conventional ES cells are present in different developmental stages, namely pre-implantation blastocyst and post-implantation blastocyst stages, also called the naïve state and the primed state, respectively. They therefore require different extrinsic signals for the maintenance of self-renewal and pluripotency, and also appear to require different surface glycans. Understanding of molecular mechanisms involving glycans in self-renewal and pluripotency of ES cells is increasingly important for potential clinical applications, as well as for basic research. This review focuses on the roles of glycans in the two different states of pluripotent stem cells, namely the naïve state and the primed state, and the transition between these two states.

Heparin Promotes Cardiac Differentiation of Human Pluripotent Stem Cells in Chemically Defined Albumin-Free Medium, Enabling Consistent Manufacture of Cardiomyocytes

Cardiomyocytes can be differentiated from human pluripotent stem cells (hPSCs) in defined conditions, but efficient and consistent cardiomyocyte differentiation often requires expensive reagents such as B27 supplement or recombinant albumin. Using a chemically defined albumin-free (E8 basal) medium, we identified heparin as a novel factor that significantly promotes cardiomyocyte differentiation efficiency, and developed an efficient method to differentiate hPSCs into cardiomyocytes. The treatment with heparin helped cardiomyocyte differentiation consistently reach at least 80% purity (up to 95%) from more than 10 different hPSC lines in chemically defined Dulbecco's modified Eagle's medium/F-12-based medium on either Matrigel or defined matrices like vitronectin and Synthemax. One of heparin's main functions was to act as a Wnt modulator that helped promote robust and consistent cardiomyocyte production. Our study provides an efficient, reliable, and cost-effective method for cardiomyocyte derivation from hPSCs that can be used for potential large-scale drug screening, disease modeling, and future cellular therapies. Stem Cells Translational Medicine 2017;6:527-538.

Minireview: Syndecans and their crucial roles during tissue regeneration

Syndecans are transmembrane heparan sulfate proteoglycans, with roles in development, tumorigenesis and inflammation, and growing evidence for involvement in tissue regeneration. This is a fast developing field with the prospect of utilizing tissue engineering and biomaterials in novel therapies. Syndecan receptors are not only ubiquitous in mammalian tissues, regulating cell adhesion, migration, proliferation, and differentiation through independent signaling but also working alongside other receptors. Their importance is highlighted by an ability to interact with a diverse array of ligands, including extracellular matrix glycoproteins, growth factors, morphogens, and cytokines that are important regulators of regeneration. We also discuss the potential for syndecans to regulate stem cell properties, and suggest that understanding these proteoglycans is relevant to exploiting cell, tissue, and materials technologies.

The role of heparan sulphate in development: the ectodermal story

Heparan sulphate (HS) is ubiquitously expressed and is formed of repeating glucosamine and glucuronic/iduronic acid units which are generally highly sulphated. HS is found in tissues bound to proteins forming HS proteoglycans (HSPGs) which are present on the cell membrane or in the extracellular matrix. HSPGs influence a variety of biological processes by interacting with physiologically important proteins, such as morphogens, creating storage pools, generating morphogen gradients and directly mediating signalling pathways, thereby playing vital roles during development. This review discusses the vital role HS plays in the development of tissues from the ectodermal lineage. The ectodermal layer differentiates to form the nervous system (including the spine, peripheral nerves and brain), eye, epidermis, skin appendages and tooth enamel.

Characterization of human bone morphogenetic protein gene variants for possible roles in congenital heart disease

Congenital heart disease (CHD) is a complex illness with high rates of morbidity and mortality. In embryonic development, the heart is the first formed organ, which is strictly controlled by gene regulatory networks, including transcription factors, signaling pathways, epigenetic factors and microRNAs. Bone morphogenetic protein (BMP)-2 and -4 are essential in cardiogenesis as they can induce the expression of transcription factors, NKX2-5 and GATA binding protein 4, which are important in the development of the heart. The inhibition of BMP-2 and 4- inhibits the late expression of NKX2-5 and affects cardiac differentiation. The aim of the present study was to investigate whether BMP-2 and -4 variations may be associated with CHD in Chinese Han populations. The rs1049007, rs235768 and rs17563 single nucleotide polymorphisms (SNPs), which are genetic variations located within the translated region of the BMP-2 and -4, were evaluated in 230 patients with CHD from the Chinese Han population and 160 non CHD control individuals. Statistical analyses were performed using the χ² test, implemented using SPSS software (version 13.0). The Hardy Weinberg equilibrium test was performed on the population using online Online Encyclopedia for Genetic Epidemiology studies software, and multiple-sequence alignments of the BMP proteins were performed using Vector NTI software. No statistically significant associations were identified between these genetic variations and the risk of CHD (rs1049007, P value=0.560; rs235768, P value=0.972; rs17563, P value=0.787). In addition, no correlation was found between the patients with CHD and the non-CHD control individuals. Therefore, the rs1049007, rs235768 and rs17563 genetic variations of BMP-2 were not associated with CHD in the Chinese Han population.

Biomaterial strategies for controlling stem cell fate via morphogen sequestration

This review explores the role of protein sequestration in the stem cell niche and how it has inspired the design of biomaterials that exploit natural protein sequestration to influence stem cell fate.

"GAG-ing with the neuron": The role of glycosaminoglycan patterning in the central nervous system

Proteoglycans (PGs) are a diverse family of proteins that consist of one or more glycosaminoglycan (GAG) chains, covalently linked to a core protein. PGs are major components of the extracellular matrix (ECM) and play critical roles in development, normal function and damage-response of the central nervous system (CNS). GAGs are classified based on their disaccharide subunits, into the following major groups: chondroitin sulfate (CS), heparan sulfate (HS), heparin (HEP), dermatan sulfate (DS), keratan sulfate (KS) and hyaluronic acid (HA). All except HA are modified by sulfation, giving GAG chains specific charged structures and binding properties. While significant neuroscience research has focused on the role of one PG family member, chondroitin sulfate proteoglycan (CSPG), there is ample evidence in support of a role for the other PGs in regulating CNS function in normal and pathological conditions. This review discusses the role of all the identified PG family members (CS, HS, HEP, DS, KS and HA) in normal CNS function and in the context of pathology. Understanding the pleiotropic roles of these molecules in the CNS may open the door to novel therapeutic strategies for a number of neurological conditions.

Retinoic Acid Induces Embryonic Stem Cell Differentiation by Altering Both Encoding RNA and microRNA Expression

Retinoic acid (RA) is a vitamin A metabolite that is essential for early embryonic development and promotes stem cell neural lineage specification; however, little is known regarding the impact of RA on mRNA transcription and microRNA levels on embryonic stem cell differentiation. Here, we present mRNA microarray and microRNA high-output sequencing to clarify how RA regulates gene expression. Using mRNA microarray analysis, we showed that RA repressed pluripotency-associated genes while activating ectoderm markers in mouse embryonic stem cells (mESCs). Moreover, RA modulated the DNA methylation of mESCs by altering the expression of epigenetic-associated genes such as Dnmt3b and Dnmt3l. Furthermore, H3K4me2, a pluripotent histone modification, was repressed by RA stimulation. From microRNA sequence data, we identified two downregulated microRNAs, namely, miR-200b and miR-200c, which regulated the pluripotency of stem cells. We found that miR-200b or miR-200c deficiency suppressed the expression of pluripotent genes, including Oct4 and Nanog, and activated the expression of the ectodermal marker gene Nestin. These results demonstrate that retinoid induces mESCs to differentiate by regulating miR-200b/200c. Our findings provide the landscapes of mRNA and microRNA gene networks and indicate the crucial role of miR-200b/200c in the RA-induced differentiation of mESCs.

Extracellular distribution of diffusible growth factors controlled by heparan sulfate proteoglycans during mammalian embryogenesis

During mouse embryogenesis, diffusible growth factors, i.e. fibroblast growth factors, Wnt, bone morphogenetic protein and Hedgehog family members, emanating from localized areas can travel through the extracellular space and reach their target cells to specify the cell fate and form tissue architectures in coordination. However, the mechanisms by which these growth factors travel great distances to their target cells and control the signalling activity as morphogens remain an enigma. Recent studies in mice and other model animals have revealed that heparan sulfate proteoglycans (HSPGs) located on the cell surface (e.g. syndecans and glypicans) and in the extracellular matrix (ECM; e.g. perlecan and agrin) play crucial roles in the extracellular distribution of growth factors. Principally, the function of HSPGs depends primarily on the fine features and localization of their heparan sulfate glycosaminoglycan chains. Cell-surface-tethered HSPGs retain growth factors as co-receptors and/or endocytosis mediators, and enzymatic release of HSPGs from the cell membrane allows HSPGs to transport or move multiple growth factors. By contrast, ECM-associated HSPGs function as a reservoir or barrier in a context-dependent manner. This review is focused on our current understanding of the extracellular distribution of multiple growth factors controlled by HSPGs in mammalian development.

Induction of primordial germ cell-like cells from mouse embryonic stem cells by ERK signal inhibition

Primordial germ cells (PGCs) are embryonic germ cell precursors. Specification of PGCs occurs under the influence of mesodermal induction signaling during in vivo gastrulation. Although bone morphogenetic proteins and Wnt signaling play pivotal roles in both mesodermal and PGC specification, the signal regulating PGC specification remains unknown. Coculture of mouse embryonic stem cells (ESCs) with OP9 feeder cells induces mesodermal differentiation in vitro. Using this mesodermal differentiation system, we demonstrated that PGC-like cells were efficiently induced from mouse ESCs by extracellular signal-regulated kinase (ERK) signaling inhibition. Inhibition of ERK signaling by a MAPK/ERK kinase (MEK) inhibitor upregulated germ cell marker genes but downregulated mesodermal genes. In addition, the PGC-like cells showed downregulation of DNA methylation and formed pluripotent stem cell colonies upon treatment with retinoic acid. These results show that inhibition of ERK signaling suppresses mesodermal differentiation but activates germline differentiation program in this mesodermal differentiation system. Our findings provide a new insight into the signaling networks regulating PGC specification.

Defining minimum essential factors to derive highly pure human endothelial cells from iPS/ES cells in an animal substance-free system

It is desirable to obtain unlimited supplies of endothelial cells for research and therapeutics. However, current methods of deriving endothelial cells from humans suffer from issues, such as limited supplies, contamination from animal substances, and lengthy/complicated procedures. In this article we developed a way to differentiate human iPS and ES cells to highly pure endothelial cells in 5 days. The chemically defined system is robust, easy to perform, and free of animal substances. Using the system, we verified that combined TGFβ and canonical Wnt agonists are essential and sufficient for iPS/ES cell-to-mesoderm transition. Besides, VEGF-KDR signaling alone is required for endothelial formation at high density while supplementation with FGF allows for colonial endothelial differentiation. Finally, anti-adsorptive agents could enrich the endothelial output by allowing selective attachment of the endothelial precursors. The system was validated to work on multiple iPS/ES cells lines to produce endothelial cells capable of forming capillary-like structures in vitro and integrating into host vasculature in vivo. In sum, the simple yet robust differentiation system permits the unlimited supply of human endothelial cells. The defined and animal substance-free nature of the system is compatible with clinical applications and characterization of endothelial differentiation in an unbiased manner.