A mesoderm-derived precursor for mesenchymal stem and endothelial cells

Genome-wide analysis of epigenetic dynamics across human developmental stages and tissues

BACKGROUND

Epigenome is highly dynamic during the early stages of embryonic development. Epigenetic modifications provide the necessary regulation for lineage specification and enable the maintenance of cellular identity. Given the rapid accumulation of genome-wide epigenomic modification maps across cellular differentiation process, there is an urgent need to characterize epigenetic dynamics and reveal their impacts on differential gene regulation.

METHODS

We proposed DiffEM, a computational method for differential analysis of epigenetic modifications and identified highly dynamic modification sites along cellular differentiation process. We applied this approach to investigating 6 epigenetic marks of 20 kinds of human early developmental stages and tissues, including hESCs, 4 hESC-derived lineages and 15 human primary tissues.

RESULTS

We identified highly dynamic modification sites where different cell types exhibit distinctive modification patterns, and found that these highly dynamic sites enriched in the genes related to cellular development and differentiation. Further, to evaluate the effectiveness of our method, we correlated the dynamics scores of epigenetic modifications with the variance of gene expression, and compared the results of our method with those of the existing algorithms. The comparison results demonstrate the power of our method in evaluating the epigenetic dynamics and identifying highly dynamic regions along cell differentiation process.

Comparison of human isogeneic Wharton's jelly MSCs and iPSC-derived MSCs reveals differentiation-dependent metabolic responses to IFNG stimulation

Variability among donors, non-standardized methods for isolation, and characterization contribute to mesenchymal stem/stromal cell (MSC) heterogeneity. Induced pluripotent stem cell (iPSCs)-derived MSCs would circumvent many of current issues and enable large-scale production of standardized cellular therapy. To explore differences between native MSCs (nMSCs) and iPSC-derived MSCs (iMSCs), we developed isogeneic lines from Wharton’s jelly (WJ) from the umbilical cords of two donors (#12 and #13) under xeno-free conditions. Next, we reprogrammed them into iPSCs (iPSC12 and iPSC13) and subsequently differentiated them back into iMSCs (iMSC12 and iMSC13) using two different protocols, which we named ARG and TEX. We assessed their differentiation capability, transcriptome, immunomodulatory potential, and interferon-γ (IFNG)-induced changes in metabolome. Our data demonstrated that although both differentiation protocols yield iMSCs similar to their parental nMSCs, there are substantial differences. The ARG protocol resulted in iMSCs with a strong immunomodulatory potential and lower plasticity and proliferation rate, whereas the TEX protocol raised iMSCs with a higher proliferation rate, better differentiation potential, though weak immunomodulatory response. Our data suggest that, following a careful selection and screening of donors, nMSCs from umbilical’s cord WJ can be easily reprogrammed into iPSCs, providing an unlimited source of material for differentiation into iMSCs. However, the differentiation protocol should be chosen depending on their clinical use.

Characterization and Therapeutic Application of Mesenchymal Stem Cells with Neuromesodermal Origin from Human Pluripotent Stem Cells

Rationale: Mesenchymal stem cells (MSC) hold great promise in the treatment of various diseases including autoimmune diseases, inflammatory diseases, etc., due to their pleiotropic properties. However, largely incongruent data were obtained from different MSC-based clinical trials, which may be partially due to functional heterogeneity among MSC. Here, we attempt to derive homogeneous mesenchymal stem cells with neuromesodermal origin from human pluripotent stem cells (hPSC) and evaluate their functional properties.

Methods: Growth factors and/or small molecules were used for the differentiation of human pluripotent stem cells (hPSC) into neuromesodermal progenitors (NMP), which were then cultured in animal component-free and serum-free induction medium for the derivation and long-term expansion of MSC. The resulted NMP-MSC were detailed characterized by analyzing their surface marker expression, proliferation, migration, multipotency, immunomodulatory activity and global gene expression profile. Moreover, the in vivo therapeutic potential of NMP-MSC was detected in a mouse model of contact hypersensitivity (CHS).

Results: We demonstrate that NMP-MSC express posterior HOX genes and exhibit characteristics similar to those of bone marrow MSC (BMSC), and NMP-MSC derived from different hPSC lines show high level of similarity in global gene expression profiles. More importantly, NMP-MSC display much stronger immunomodulatory activity than BMSC in vitro and in vivo, as revealed by decreased inflammatory cell infiltration and diminished production of pro-inflammatory cytokines in inflamed tissue of CHS models.

Conclusion: Our results identify NMP as a new source of MSC and suggest that functional and homogeneous NMP-MSC could serve as a candidate for MSC-based therapies.

iPSC- and mesenchymoangioblast-derived mesenchymal stem cells provide greater protection against experimental chronic allergic airways disease compared with a clinically used corticosteroid

The airway remodeling (AWR) associated with chronic allergic airways disease (AAD)/asthma contributes to irreversible airway obstruction. This study compared and combined the antiremodeling and other effects of induced pluripotent stem cell and mesenchymoangioblast-derived mesenchymal stem cells (MCA-MSCs) with the corticosteroid dexamethasone (Dex) in experimental chronic AAD/asthma. Female BALB/c mice subjected to 11 wk of ovalbumin (Ova)-induced chronic AAD were intranasally administered MCA-MSCs (1 × 10⁶ cells/mouse; once weekly on wk 10 and 11), Dex (0.5 mg/ml; once daily for 2 wk), or both combined. MCA-MSC detection and changes in airway inflammation (AI), AWR, and airway hyperresponsiveness (AHR) were measured at the end of wk 11. Mice with chronic AAD had significant AI, goblet cell metaplasia, epithelial damage/thickening, aberrant TGF-β1 levels, subepithelial myofibroblast accumulation, airway/lung fibrosis, and AHR (all P < 0.001 vs. healthy controls). MCA-MSCs were detected in the lungs up to 5-7 d postadministration and demonstrated modest anti-inflammatory but striking antifibrotic effects against Ova-induced AAD, effectively decreasing AHR by 70-75% (all P < 0.05 vs. Ova alone). In comparison, Dex predominantly demonstrated anti-inflammatory effects, decreasing AHR by ∼30%. Combining MCA-MSCs with Dex provided equivalent protection to that offered by either therapy alone. MCA-MSCs reduce chronic AAD-induced AWR and AHR to a greater extent than Dex and may act as a suitable adjunct therapy to corticosteroid treatment of asthma.-Royce, S. G., Mao, W., Lim, R., Kelly, K., Samuel, C. S. iPSC- and mesenchymoangioblast-derived mesenchymal stem cells provide greater protection against experimental chronic allergic airways disease compared with a clinically used corticosteroid.

Cymerus™ iPSC-MSCs significantly prolong survival in a pre-clinical, humanized mouse model of Graft-vs-host disease

The immune-mediated tissue destruction of graft-vs-host disease (GvHD) remains a major barrier to greater use of hematopoietic stem cell transplantation (HSCT). Mesenchymal stem cells (MSCs) have intrinsic immunosuppressive qualities and are being actively investigated as a therapeutic strategy for treating GvHD. We characterized Cymerus™ MSCs, which are derived from adult, induced pluripotent stem cells (iPSCs), and show they display surface markers and tri-lineage differentiation consistent with MSCs isolated from bone marrow (BM). Administering iPSC-MSCs altered phosphorylation and cellular localization of the T cell-specific kinase, Protein Kinase C theta (PKCθ), attenuated disease severity, and prolonged survival in a humanized mouse model of GvHD. Finally, we evaluated a constellation of pro-inflammatory molecules on circulating PBMCs that correlated closely with disease progression and which may serve as biomarkers to monitor therapeutic response. Altogether, our data suggest Cymerus iPSC-MSCs offer the potential for an off-the-shelf, cell-based therapy to treat GvHD.

Concise Review: Mesenchymal Stem Cells Derived from Human Pluripotent Cells, an Unlimited and Quality-Controllable Source for Therapeutic Applications

Despite the long discrepancy over their definition, heterogeneity, and functions, mesenchymal stem cells (MSCs) have proved to be a key player in tissue repair and homeostasis. Generally, somatic tissue-derived MSCs (st-MSCs) are subject to quality variations related to donated samples and biosafety concern for transmission of potential pathogens from the donors. In contrast, human pluripotent stem cells (hPSCs) are unlimited in supply, clear in the biological background, and convenient for quality control, genetic modification, and scale-up production. We, and others, have shown that hPSCs can differentiate in two dimensions or three dimensions to MSCs (ps-MSCs) via embryonic (mesoderm and neural crest) or extraembryonic (trophoblast) cell types under serum-containing or xeno-free and defined conditions. Compared to st-MSCs, ps-MSCs appear less mature, proliferate faster, express lower levels of inflammatory cytokines, and respond less to traditional protocols for st-MSC differentiation to other cell types, especially adipocytes. Nevertheless, ps-MSCs are capable of immune modulation and treatment of an increasing number of animal disease models via mitochondria transfer, paracrine, exosomes, and direct differentiation, and can be potentially used as a universal and endless therapy for clinical application. This review summarizes the progress on ps-MSCs and discusses perspectives and challenges for their potential translation to the clinic. Stem Cells 2019;37:572-581.

NOTCH Activation at the Hematovascular Mesoderm Stage Facilitates Efficient Generation of T Cells with High Proliferation Potential from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) offer the potential to serve as a versatile and scalable source of T cells for immunotherapies, which could be coupled with genetic engineering technologies to meet specific clinical needs. To improve T cell production from hPSCs, it is essential to identify cell subsets that are highly enriched in T cell progenitors and those stages of development at which NOTCH activation induces the most potent T cells. In this study, we evaluated the efficacy of T cell production from cell populations isolated at different stages of hematopoietic differentiation, including mesoderm, hemogenic endothelium (HE), and multipotent hematopoietic progenitors. We demonstrate that KDR^hiCD31^- hematovascular mesodermal progenitors (HVMPs) with definitive hematopoietic potential produce the highest numbers of T cells when cultured on OP9-DLL4 as compared with downstream progenitors, including HE and multipotent hematopoietic progenitors. In addition, we found that T cells generated from HVMPs have the capacity to expand for 6-7 wk in vitro, in comparison with T cells generated from HE and hematopoietic progenitors, which could only be expanded for 4-5 wk. Demonstrating the critical need of NOTCH activation at the HVMP stage of hematopoietic development to establish robust T cell production from hPSCs may aid in establishing protocols for the efficient off-the-shelf production and expansion of T cells for treating hematologic malignancies.

Arterial identity of hemogenic endothelium: a key to unlock definitive hematopoietic commitment in human pluripotent stem cell cultures

Human pluripotent stem cells (hPSCs) have been suggested as a potential source for the de novo production of blood cells for transfusion, immunotherapies, and transplantation. However, even with advanced hematopoietic differentiation methods, the primitive and myeloid-restricted waves of hematopoiesis dominate in hPSC differentiation cultures, whereas cell surface markers to distinguish these waves of hematopoiesis from lympho-myeloid hematopoiesis remain unknown. In the embryo, hematopoietic stem cells (HSCs) arise from hemogenic endothelium (HE) lining arteries, but not veins. This observation led to a long-standing hypothesis that arterial specification is an essential prerequisite to initiate the HSC program. It has also been established that lymphoid potential in the yolk sac and extraembryonic vasculature is mostly confined to arteries, whereas myeloid-restricted hematopoiesis is not specific to arterial vessels. Here, we review how the link between arterialization and the subsequent definitive multilineage hematopoietic program can be exploited to identify HE enriched in lymphoid progenitors and aid in in vitro approaches to enhance the production of lymphoid cells and potentially HSCs from hPSCs. We also discuss alternative models of hematopoietic specification at arterial sites and recent advances in our understanding of hematopoietic development and the production of engraftable hematopoietic cells from hPSCs.

BMI1 enables interspecies chimerism with human pluripotent stem cells

Human pluripotent stem cells (hPSCs) exhibit very limited contribution to interspecies chimeras. One explanation is that the conventional hPSCs are in a primed state and so unable  to form chimeras in pre-implantation embryos. Here, we show that the conventional hPSCs undergo rapid apoptosis when injected into mouse pre-implantation embryos. While, forced-expression of BMI1, a polycomb factor in hPSCs overcomes the apoptosis and enables hPSCs to integrate into mouse pre-implantation embryos and subsequently contribute to chimeras with both embryonic and extra-embryonic tissues. In addition, BMI1 also enables hPSCs to integrate into pre-implantation embryos of other species, such as rabbit and pig. Notably, BMI1 high expression and anti-apoptosis are also indicators for naïve hPSCs to form chimera in mouse embryos. Together, our findings reveal that the apoptosis is an initial barrier in interspecies chimerism using hPSCs and provide a rational to improve it.

Generation of Mesenchymal Stem Cells from Human Embryonic Stem Cells in a Complete Serum-free Condition

Mesenchymal stem cells (MSC) have been derived from a variety of tissues, and cultured either in animal serum-containing (SC) or serum-free (SF) media. We have previously derived MSC from human embryonic stem cells via an intermediate trophoblast step (named EMSC), which also have immunosuppressive and therapeutic effects on animal models of autoimmune disease. To promote the clinical application of this new source of MSC, we report here EMSC derived and cultured in a SF medium MesenCult (SF-EMSC) in comparison with a SC medium (SC-EMSC). SF-EMSC derived in MesenCult also expressed typical MSC markers CD73, CD90, and CD105, and manifested multipotency to differentiate to osteocytes, chondrocytes, and adipocytes. Comparably, CD105⁺ cells reached 90% about one week slower in the SF than SC conditions, and the proliferation rate was slightly faster for SF-EMSC than SC-EMSC at later passages. Both SF- and SC-EMSC responded similarly to the inflammatory stimulus IFNγ. However, the inflammatory cytokines IL-6 and IL-8 were expressed much less in SF-EMSC than SC-EMSC. Furthermore, knockdown of P16^INK4A in both SF- and SC-EMSC reduced replicative senescence. Together, our results suggest that EMSC can be generated in a complete SF condition, and SF-EMSC are largely similar to SC-EMSC. However, it takes longer time to derive EMSC in the SF than SC conditions, and the SF-EMSC proliferate faster at later passages and produce less of the inflammatory cytokines IL-6 and IL-8 than SC-EMSC. This study provides important information for production of clinically applicable EMSC.

The mesenchymoangioblast, mesodermal precursor for mesenchymal and endothelial cells

Mesenchymoangioblast (MB) is the earliest precursor for endothelial and mesenchymal cells originating from APLNR+PDGFRα+KDR+ mesoderm in human pluripotent stem cell cultures. MBs are identified based on their capacity to form FGF2-dependent compact spheroid colonies in a serum-free semisolid medium. MBs colonies are composed of PDGFRβ+CD271+EMCN+DLK1+CD73- primitive mesenchymal cells which are generated through endothelial/angioblastic intermediates (cores) formed during first 3-4 days of clonogenic cultures. MB-derived primitive mesenchymal cells have potential to differentiate into mesenchymal stromal/stem cells (MSCs), pericytes, and smooth muscle cells. In this review, we summarize the specification and developmental potential of MBs, emphasize features that distinguish MBs from other mesenchymal progenitors described in the literature and discuss the value of these findings for identifying molecular pathways leading to MSC and vasculogenic cell specification, and developing cellular therapies using MB-derived progeny.

Alternative splicing links histone modifications to stem cell fate decision

BACKGROUND

Understanding the embryonic stem cell (ESC) fate decision between self-renewal and proper differentiation is important for developmental biology and regenerative medicine. Attention has focused on mechanisms involving histone modifications, alternative pre-messenger RNA splicing, and cell-cycle progression. However, their intricate interrelations and joint contributions to ESC fate decision remain unclear.

RESULTS

We analyze the transcriptomes and epigenomes of human ESC and five types of differentiated cells. We identify thousands of alternatively spliced exons and reveal their development and lineage-dependent characterizations. Several histone modifications show dynamic changes in alternatively spliced exons and three are strongly associated with 52.8% of alternative splicing events upon hESC differentiation. The histone modification-associated alternatively spliced genes predominantly function in G2/M phases and ATM/ATR-mediated DNA damage response pathway for cell differentiation, whereas other alternatively spliced genes are enriched in the G1 phase and pathways for self-renewal. These results imply a potential epigenetic mechanism by which some histone modifications contribute to ESC fate decision through the regulation of alternative splicing in specific pathways and cell-cycle genes. Supported by experimental validations and extended datasets from Roadmap/ENCODE projects, we exemplify this mechanism by a cell-cycle-related transcription factor, PBX1, which regulates the pluripotency regulatory network by binding to NANOG. We suggest that the isoform switch from PBX1a to PBX1b links H3K36me3 to hESC fate determination through the PSIP1/SRSF1 adaptor, which results in the exon skipping of PBX1.

CONCLUSION

We reveal the mechanism by which alternative splicing links histone modifications to stem cell fate decision.

Mesenchymal Stromal/Stem Cells in Regenerative Medicine and Tissue Engineering

As a result of over five decades of investigation, mesenchymal stromal/stem cells (MSCs) have emerged as a versatile and frequently utilized cell source in the fields of regenerative medicine and tissue engineering. In this review, we summarize the history of MSC research from the initial discovery of their multipotency to the more recent recognition of their perivascular identity in vivo and their extraordinary capacity for immunomodulation and angiogenic signaling. As well, we discuss long-standing questions regarding their developmental origins and their capacity for differentiation toward a range of cell lineages. We also highlight important considerations and potential risks involved with their isolation, ex vivo expansion, and clinical use. Overall, this review aims to serve as an overview of the breadth of research that has demonstrated the utility of MSCs in a wide range of clinical contexts and continues to unravel the mechanisms by which these cells exert their therapeutic effects.

Biphasic modulation of insulin signaling enables highly efficient hematopoietic differentiation from human pluripotent stem cells

Background

Hematopoietic lineage cells derived from human pluripotent stem cells (hPSCs) hold great promise for the treatment of hematological diseases and providing sufficient cells for immune therapy. However, a simple, cost-effective method to generate large quantities of hematopoietic stem/progenitor cells (HSPCs) is not yet available.

Methods

We established a monolayer, chemically defined culture system to induce hematopoietic differentiation from hPSCs in 8 days.

Results

We found that insulin-free medium allowed hPSCs to leave pluripotency promptly and preferably enter the vascular lineage. Addition of insulin during the later stage of differentiation was essential for the efficient induction of hemogenic endothelium and the emergence of large numbers of CD34⁺CD43⁺ HSPCs, while no insulin condition preferably permits endothelial differentiation. Global transcriptome profiling revealed that HSPCs differentiated using our protocol were similar to embryoid body-derived HSPCs. HSPCs obtained from our differentiation system formed robust erythroid, granulocyte and monocyte/macrophage colonies in CFU assay, and can be induced to generate functional macrophages with robust phagocytic ability.

Conclusion

Our results demonstrated that proper manipulation of insulin-mTOR signaling can greatly facilitate HSPC formation. This finding can be further exploited to formulate cost-effective differentiation medium to generate large quantities of cells of desired blood lineages for regenerative medicine.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0934-x) contains supplementary material, which is available to authorized users.

MSX2 Initiates and Accelerates Mesenchymal Stem/Stromal Cell Specification of hPSCs by Regulating TWIST1 and PRAME

The gap in knowledge of the molecular mechanisms underlying differentiation of human pluripotent stem cells (hPSCs) into the mesenchymal cell lineages hinders the application of hPSCs for cell-based therapy. In this study, we identified a critical role of muscle segment homeobox 2 (MSX2) in initiating and accelerating the molecular program that leads to mesenchymal stem/stromal cell (MSC) differentiation from hPSCs. Genetic deletion of MSX2 impairs hPSC differentiation into MSCs. When aided with a cocktail of soluble molecules, MSX2 ectopic expression induces hPSCs to form nearly homogeneous and fully functional MSCs. Mechanistically, MSX2 induces hPSCs to form neural crest cells, an intermediate cell stage preceding MSCs, and further differentiation by regulating TWIST1 and PRAME. Furthermore, we found that MSX2 is also required for hPSC differentiation into MSCs through mesendoderm and trophoblast. Our findings provide novel mechanistic insights into lineage specification of hPSCs to MSCs and effective strategies for applications of stem cells for regenerative medicine.

GATA2 Is Dispensable for Specification of Hemogenic Endothelium but Promotes Endothelial-to-Hematopoietic Transition

The transcriptional factor GATA2 is required for blood and hematopoietic stem cell formation during the hemogenic endothelium (HE) stage of development in the embryo. However, it is unclear if GATA2 controls HE lineage specification or if it solely regulates endothelial-to-hematopoietic transition (EHT). To address this problem, we innovated a unique system, which involved generating GATA2 knockout human embryonic stem cell (hESC) lines with conditional GATA2 expression (iG2-/- hESCs). We demonstrated that GATA2 activity is not required for VE-cadherin+CD43-CD73+ non-HE or VE-cadherin+CD43-CD73- HE generation and subsequent HE diversification into DLL4+ arterial and DLL4- non-arterial lineages. However, GATA2 is primarily needed for HE to undergo EHT. Forced expression of GATA2 in non-HE failed to induce blood formation. The lack of GATA2 requirement for generation of HE and non-HE indicates the critical role of GATA2-independent pathways in specification of these two distinct endothelial lineages.

Scalable Generation of Mesenchymal Stem Cells from Human Embryonic Stem Cells in 3D

Human embryonic stem cell (hESC) derived mesenchymal stem cells (EMSC) are efficacious in treating a series of autoimmune, inflammatory, and degenerative diseases in animal models. However, all the EMSC derivation methods reported so far rely on two-dimensional (2D) culture systems, which are inefficient, costive and difficult for large-scale production. HESC, as an unlimited source, can be successively propagated in spheroids. Here, we demonstrate that hESC spheroids can directly differentiate into MSC spheroids (EMSC_Sp) within 20 days in one vessel without passaging and the system is scalable to any desired size. EMSC_Sp can further differentiate into osteocytes and chondrocytes in spheres or demineralized bone matrix. EMSC_Sp also retains immune-modulatory effects in vitro and therapeutic effects on two mouse models of colitis after dissociation. Compared to EMSC differentiated in monolayer, EMSC_Sp-derived cells have faster proliferation and higher yield and develop less apoptosis and slower senescence. Thus, the 3D differentiation system allows simple, cost-effective, and scalable production of high-quality EMSC and subsequently bone and cartilage tissues for therapeutic application.

A human bone marrow mesodermal-derived cell population with hemogenic potential

The presence, within the human bone marrow, of cells with both endothelial and hemogenic potential has been controversial. Herein, we identify, within the human fetal bone marrow, prior to establishment of hematopoiesis, a unique APLNR+, Stro-1+ cell population, co-expressing markers of early mesodermal precursors and/or hemogenic endothelium. In adult marrow, cells expressing similar markers are also found, but at very low frequency. These adult-derived cells can be extensively culture expanded in vitro without loss of potential, they preserve a biased hemogenic transcriptional profile, and, upon in vitro induction with OCT4, assume a hematopoietic phenotype. In vivo, these cells, upon transplantation into a fetal microenvironment, contribute to the vasculature, and generate hematopoietic cells that provide multilineage repopulation upon serial transplantation. The identification of this human somatic cell population provides novel insights into human ontogenetic hematovascular potential, which could lead to a better understanding of, and new target therapies for, malignant and nonmalignant hematologic disorders.

Hyperstimulation of CaSR in human MSCs by biomimetic apatite inhibits endochondral ossification via temporal down-regulation of PTH1R

In adult bone injuries, periosteum-derived mesenchymal stem/stromal cells (MSCs) form bone via endochondral ossification (EO), whereas those from bone marrow (BM)/endosteum form bone primarily through intramembranous ossification (IMO). We hypothesized that this phenomenon is influenced by the proximity of MSCs residing in the BM to the trabecular bone microenvironment. Herein, we investigated the impact of the bone mineral phase on human BM-derived MSCs' choice of ossification pathway, using a biomimetic bone-like hydroxyapatite (BBHAp) interface. BBHAp induced hyperstimulation of extracellular calcium-sensing receptor (CaSR) and temporal down-regulation of parathyroid hormone 1 receptor (PTH1R), leading to inhibition of chondrogenic differentiation of MSCs even in the presence of chondroinductive factors, such as transforming growth factor-β1 (TGF-β1). Interestingly rescuing PTH1R expression using human PTH fragment (1-34) partially restored chondrogenesis in the BBHAp environment. In vivo studies in an ectopic site revealed that the BBHAp interface inhibits EO and strictly promotes IMO. Furthermore, CaSR knockdown (CaSR KD) disrupted the bone-forming potential of MSCs irrespective of the absence or presence of the BBHAp interface. Our findings confirm the expression of CaSR in human BM-derived MSCs and unravel a prominent role for the interplay between CaSR and PTH1R in regulating MSC fate and the choice of pathway for bone formation.

Application of small molecule CHIR99021 leads to the loss of hemangioblast progenitor and increased hematopoiesis of human pluripotent stem cells

Improving our understanding of the intricacies of hematopoietic specification of induced or embryonic human pluripotent stem cells is beneficial for many areas of research and translational medicine. Currently, it is not clear whether, during human pluripotent stem cells hematopoietic differentiation in vitro, the maturation of definitive progenitors proceeds through a primitive progenitor (hemangioblast) intermediate or if it develops independently. The objective of this study was to investigate the early stages of hematopoietic specification of pluripotent stem cells in vitro. By implementing an adherent culture, serum-free differentiation system that utilizes a small molecule, CHIR99021, to induce human pluripotent stem cells toward various hematopoietic lineages, we established that, compared with the OP9 coculture hematopoietic induction system, the application of CHIR99021 alters the early steps of hematopoiesis such as hemangioblasts, angiogenic hematopoietic progenitors, and hemogenic endothelium. Importantly, it is associated with the loss of hemangioblast progenitors, loss of CD43⁺ (primitive hematopoietic marker) expression, and predominant development of blast-forming unit erythroid colonies in semisolid medium. These data support the hypothesis that the divergence of primitive and definitive programs during human pluripotent stem cells differentiation precedes the hemangioblast stage. Furthermore, we have shown that the inhibition of primitive hematopoiesis is associated with an increase in hematopoietic potential, which is a fruitful finding due to the growing need for lymphoid and myeloid cells in translational applications.

Functional Heterogeneity of Endothelial Cells Derived from Human Pluripotent Stem Cells

Specification of endothelial cells (ECs) into arterial, venous, and lymphatic cells is a crucial process of vascular development, and expanding our knowledge about EC specification from human pluripotent stem cells (hPSCs) will aid the design of optimal strategies for producing desired types of ECs for therapies. In our prior studies, we revealed that hPSC-derived VE-cadherin(V)⁺CD31⁺CD34⁺ ECs are heterogeneous and include at least three major subsets with distinct hemogenic properties: V⁺CD43/235a^-CD73^- hemogenic endothelial progenitors (HEPs), V⁺CD43^loCD235a⁺73^- angiogenic hematopoietic progenitors (AHPs), and V⁺CD43/235a^-73⁺ non-HEPs. In this study, using angiogenesis assays, we demonstrated that ECs within these subsets have distinct endothelial colony- and tube-forming properties, proliferative and migratory properties, and endothelial nitric oxide synthase and inflammatory cytokine production potentials. Culture of isolated subsets in arterial, venous, and lymphatic conditions revealed that AHPs are skewed toward lymphatic, HEPs toward arterial, and non-HEPs toward venous differentiation in vitro. These findings suggest that selection and enhancement of production of a particular EC subset may aid in generating desirable EC populations with arterial, venous, or lymphatic properties from hPSCs.

Specification and Diversification of Pericytes and Smooth Muscle Cells from Mesenchymoangioblasts

Elucidating the pathways that lead to vasculogenic cells, and being able to identify their progenitors and lineage-restricted cells, is critical to the establishment of human pluripotent stem cell (hPSC) models for vascular diseases and development of vascular therapies. Here, we find that mesoderm-derived pericytes (PCs) and smooth muscle cells (SMCs) originate from a clonal mesenchymal progenitor mesenchymoangioblast (MB). In clonogenic cultures, MBs differentiate into primitive PDGFRβ⁺ CD271⁺CD73⁻ mesenchymal progenitors, which give rise to proliferative PCs, SMCs, and mesenchymal stem/stromal cells. MB-derived PCs can be further specified to CD274⁺ capillary and DLK1⁺ arteriolar PCs with a proinflammatory and contractile phenotype, respectively. SMC maturation was induced using a MEK inhibitor. Establishing the vasculogenic lineage tree, along with identification of stage- and lineage-specific markers, provides a platform for interrogating the molecular mechanisms that regulate vasculogenic cell specification and diversification and manufacturing well-defined mural cell populations for vascular engineering and cellular therapies from hPSCs.

Kumar et al. find that mesodermal pericytes and smooth muscle cells in human pluripotent stem cell cultures originate from a common endothelial and mesenchymal cell precursor, the mesenchymoangioblast. They show how different lineages of mural cells are specified from mesenchymoangioblasts and define stage- and lineage-specific markers for vasculogenic cells.

Meso-Endothelial Bipotent Progenitors from Human Placenta Display Distinct Molecular and Cellular Identity

The existence of bipotential precursors for both mesenchymal and endothelial stem/progenitor cells in human postnatal life is debated. Here, we hypothesized that such progenitors are present within the human term placenta. From a heterogeneous placental single-cell suspension, a directly flow-sorted CD45^-CD34⁺CD144⁺CD31Lo population uniquely differentiated into both endothelial and mesenchymal colonies in limiting dilution culture assays. Of interest, these bipotent cells were in vessel walls but not in contact with the circulation. RNA sequencing and functional analysis demonstrated that Notch signaling was a key driver for endothelial and bipotential progenitor function. In contrast, the formation of mesenchymal cells from the bipotential population was not affected by TGFβ receptor inhibition, a classical pathway for endothelial-mesenchymal transition. This study reveals a bipotent progenitor phenotype in the human placenta at the cellular and molecular levels, giving rise to endothelial and mesenchymal cells ex vivo.

Embryonic Stem Cell-Derived Mesenchymal Stem Cells (MSCs) Have a Superior Neuroprotective Capacity Over Fetal MSCs in the Hypoxic-Ischemic Mouse Brain

Human mesenchymal stem cells (MSCs) have huge potential for regenerative medicine. In particular, the use of pluripotent stem cell‐derived mesenchymal stem cells (PSC‐MSCs) overcomes the hurdle of replicative senescence associated with the in vitro expansion of primary cells and has increased therapeutic benefits in comparison to the use of various adult sources of MSCs in a wide range of animal disease models. On the other hand, fetal MSCs exhibit faster growth kinetics and possess longer telomeres and a wider differentiation potential than adult MSCs. Here, for the first time, we compare the therapeutic potential of PSC‐MSCs (ES‐MSCs from embryonic stem cells) to fetal MSCs (AF‐MSCs from the amniotic fluid), demonstrating that ES‐MSCs have a superior neuroprotective potential over AF‐MSCs in the mouse brain following hypoxia‐ischemia. Further, we demonstrate that nuclear factor (NF)‐κB‐stimulated interleukin (IL)‐13 production contributes to an increased in vitro anti‐inflammatory potential of ES‐MSC‐conditioned medium (CM) over AF‐MSC‐CM, thus suggesting a potential mechanism for this observation. Moreover, we show that induced pluripotent stem cell‐derived MSCs (iMSCs) exhibit many similarities to ES‐MSCs, including enhanced NF‐κB signaling and IL‐13 production in comparison to AF‐MSCs. Future studies should assess whether iMSCs also exhibit similar neuroprotective potential to ES‐MSCs, thus presenting a potential strategy to overcome the ethical issues associated with the use of embryonic stem cells and providing a potential source of cells for autologous use against neonatal hypoxic‐ischemic encephalopathy in humans. Stem Cells Translational Medicine2018;7:439–449

Transcriptionally and Functionally Distinct Mesenchymal Subpopulations Are Generated from Human Pluripotent Stem Cells

Various mesenchymal cell types have been identified as critical components of the hematopoietic stem/progenitor cell (HSPC) niche. Although several groups have described the generation of mesenchyme from human pluripotent stem cells (hPSCs), the capacity of such cells to support hematopoiesis has not been reported. Here, we demonstrate that distinct mesenchymal subpopulations co-emerge from mesoderm during hPSC differentiation. Despite co-expression of common mesenchymal markers (CD73, CD105, CD90, and PDGFRβ), a subset of cells defined as CD146^hiCD73^hi expressed genes associated with the HSPC niche and supported the maintenance of functional HSPCs ex vivo, while CD146^loCD73^lo cells supported differentiation. Stromal support of HSPCs was contact dependent and mediated in part through high JAG1 expression and low WNT signaling. Molecular profiling revealed significant transcriptional similarity between hPSC-derived CD146⁺⁺ and primary human CD146⁺⁺ perivascular cells. The derivation of functionally diverse types of mesenchyme from hPSCs opens potential avenues to model the HSPC niche and develop PSC-based therapies.

The utility of stem cells in pediatric urinary bladder regeneration

Pediatric patients with a neurogenic urinary bladder, caused by developmental abnormalities including spina bifida, exhibit chronic urological problems. Surgical management in the form of enterocystoplasty is used to enlarge the bladder, but is associated with significant clinical complications. Thus, alternative methods to enterocystoplasty have been explored through the incorporation of stem cells with tissue engineering strategies. Within the context of this review, we will examine the use of bone marrow stem cells and induced pluripotent stem cells (iPSCs), as they relate to bladder regeneration at the anatomic and molecular levels. The use of bone marrow stem cells has demonstrated significant advances in bladder tissue regeneration as multiple aspects of bladder tissue have been recapitulated including the urothelium, bladder smooth muscle, vasculature, and peripheral nerves. iPSCs, on the other hand, have been well characterized and used in multiple tissue-regenerative settings, yet iPSC research is still in its infancy with regards to bladder tissue regeneration with recent studies describing the differentiation of iPSCs to the bladder urothelium. Finally, we examine the role of the Sonic Hedgehog signaling cascade that mediates the proliferative response during regeneration between bladder smooth muscle and urothelium. Taken together, this review provides a current, comprehensive perspective on bladder regeneration.

Mesenchymal Stem Cells as Endogenous Regulators of Inflammation

This chapter discusses the regulatory role of endogenous mesenchymal stem cells (MSC) during an inflammatory response. MSC are a heterogeneous population of multipotent cells that normally contribute towards tissue maintenance and repair but have garnered significant scientific interest for their potent immunomodulatory potential. It is through these physicochemical interactions that MSC are able to exert an anti-inflammatory response on neighbouring stromal and haematopoietic cells. However, the impact of the chronic inflammatory environment on MSC function remains to be determined. Understanding the relationship of MSC between resolution of inflammation and autoimmunity will both offer new insights in the use of MSC as a therapeutic, and also their involvement in the pathogenesis of inflammatory disorders.

Mesenchymal Stem Cells in Cardiology

Cardiovascular disease (CVD) accounts for more deaths globally than any other single disease. There are on average 1.5 million episodes of myocardial infarction (heart attack) each year in the United States alone with roughly one-third resulting in death. There is therefore a major need for developing new and effective strategies to promote cardiac repair. Intramyocardial transplantation of mesenchymal stem cells (MSCs) has emerged as a leading contender in the pursuit of clinical intervention and therapy. MSCs are potent mediators of cardiac repair and are therefore an attractive tool in the development of preclinical and clinical trials. MSCs are capable of secreting a large array of soluble factors, which have had demonstrated effects on pathogenic cardiac remolding, fibrosis, immune activation, and cardiac stem cell proliferation within the damaged heart. MSCs are also capable of differentiation into cardiomyocytes, endothelial cells, and vascular smooth muscle cells, although the relative contribution of trilineage differentiation and paracrine effectors on cardiac repair remains the subject of active investigation.

Constitutional abnormalities of IDH1 combined with secondary mutations predispose a patient with Maffucci syndrome to acute lymphoblastic leukemia

Maffucci syndrome is a nonhereditary disorder caused by somatic mosaic isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) mutations and is characterized by multiple enchondromas along with hemangiomas. Malignant transformation of enchondromas to chondrosarcomas and secondary neoplasms, such as brain tumors or acute myeloid leukemia, are serious complications. A 15-year-old female with Maffucci syndrome developed B-cell precursor acute lymphoblastic leukemia (BCP-ALL). A somatic mutation in IDH1 was detected in hemangioma and leukemic cells. KRAS mutation and deletion of IKZF1 were detected in leukemic cells. Patients with Maffucci syndrome may, therefore, be at risk of BCP-ALL associated with secondary genetic events that affect lymphocyte differentiation.

Structural and spatial chromatin features at developmental gene loci in human pluripotent stem cells

Higher-order chromatin organization controls transcriptional programs that govern cell properties and functions. In order for pluripotent stem cells (PSCs) to appropriately respond to differentiation signals, developmental gene loci should be structurally and spatially regulated to be readily available for immediate transcription, even though these genes are hardly expressed in PSCs. Here, we show that both chromatin interaction profiles and nuclear positions at developmental gene loci differ between human somatic cells and hPSCs, and that changes in the chromatin interactions are closely related to the nuclear repositioning. Moreover, we also demonstrate that developmental gene loci, which have bivalent histone modifications, tend to colocalize in PSCs. Furthermore, this colocalization requires PRC1, PRC2, and TrxG complexes, which are essential regulatory factors for the maintenance of transcriptionally poised developmental genes. Our results indicate that higher-order chromatin regulation may be an integral part of the differentiation capacity that defines pluripotency.

Prokineticin receptor-1-dependent paracrine and autocrine pathways control cardiac tcf21+ fibroblast progenitor cell transformation into adipocytes and vascular cells

Cardiac fat tissue volume and vascular dysfunction are strongly associated, accounting for overall body mass. Despite its pathophysiological significance, the origin and autocrine/paracrine pathways that regulate cardiac fat tissue and vascular network formation are unclear. We hypothesize that adipocytes and vasculogenic cells in adult mice hearts may share a common cardiac cells that could transform into adipocytes or vascular lineages, depending on the paracrine and autocrine stimuli. In this study utilizing transgenic mice overexpressing prokineticin receptor (PKR1) in cardiomyocytes, and tcf21ERT-cre^TM-derived cardiac fibroblast progenitor (CFP)-specific PKR1 knockout mice (PKR1^tcf−/−), as well as FACS-isolated CFPs, we showed that adipogenesis and vasculogenesis share a common CFPs originating from the tcf21⁺ epithelial lineage. We found that prokineticin-2 is a cardiomyocyte secretome that controls CFP transformation into adipocytes and vasculogenic cells in vivo and in vitro. Upon HFD exposure, PKR1^tcf−/− mice displayed excessive fat deposition in the atrioventricular groove, perivascular area, and pericardium, which was accompanied by an impaired vascular network and cardiac dysfunction. This study contributes to the cardio-obesity field by demonstrating that PKR1 via autocrine/paracrine pathways controls CFP–vasculogenic- and CFP-adipocyte-transformation in adult heart. Our study may open up new possibilities for the treatment of metabolic cardiac diseases and atherosclerosis.

Human haematopoietic stem cell development: from the embryo to the dish

Haematopoietic stem cells (HSCs) emerge during embryogenesis and give rise to the adult haematopoietic system. Understanding how early haematopoietic development occurs is of fundamental importance for basic biology and medical sciences, but our knowledge is still limited compared with what we know of adult HSCs and their microenvironment. This is particularly true for human haematopoiesis, and is reflected in our current inability to recapitulate the development of HSCs from pluripotent stem cells in vitro In this Review, we discuss what is known of human haematopoietic development: the anatomical sites at which it occurs, the different temporal waves of haematopoiesis, the emergence of the first HSCs and the signalling landscape of the haematopoietic niche. We also discuss the extent to which in vitro differentiation of human pluripotent stem cells recapitulates bona fide human developmental haematopoiesis, and outline some future directions in the field.

Double-edged sword of mesenchymal stem cells: Cancer-promoting versus therapeutic potential

Mesenchymal stem cells (MSCs) derived from adipose tissue, bone marrow, cord blood, and other tissues, have recently attracted much attention as potential therapeutic agents in various diseases because of their trans‐differentiation capacity. However, recent studies have suggested that MSCs also appear to contribute to tumor pathogenesis by supporting tumor microenvironments, increasing tumor growth, and eliciting antitumor immune responses. Although some studies suggest that MSCs have inhibitory effects on tumor development, they are overwhelmed by a number of studies showing that MSCs exert stimulatory effects on tumor pathogenesis. In the present review, we summarize a number of findings to provide current information about the therapeutic potential of MSCs in various diseases. We then discuss the potential roles of MSCs in tumor progression.

Inhibition of EZH2 Promotes Human Embryonic Stem Cell Differentiation into Mesoderm by Reducing H3K27me3

Mesoderm derived from human embryonic stem cells (hESCs) is a major source of the mesenchymal stem/stromal cells (MSCs) that can differentiate into osteoblasts and chondrocytes for tissue regeneration. While significant progress has been made in understanding of molecular mechanisms of hESC differentiation into mesodermal cells, little is known about epigenetic factors controlling hESC fate toward mesoderm and MSCs. Identifying potential epigenetic factors that control hESC differentiation will undoubtedly lead to advancements in regenerative medicine. Here, we conducted an epigenome-wide analysis of hESCs and MSCs and uncovered that EZH2 was enriched in hESCs and was downregulated significantly in MSCs. The specific EZH2 inhibitor GSK126 directed hESC differentiation toward mesoderm and generated more MSCs by reducing H3K27me3. Our results provide insights into epigenetic landscapes of hESCs and MSCs and suggest that inhibiting EZH2 promotes mesodermal differentiation of hESCs.

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Inhibiting EZH2 directs hESC differentiation to mesoderm and generates more MSCs

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H3K27me3 levels decrease on specific gene clusters as hESCs differentiate to MSCs

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EZH2 is downregulated as hESC differentiate to MSCs

microRNA Regulation of Skeletal Development

PURPOSE OF REVIEW

Osteogenesis is a complex process involving the specification of multiple progenitor cells and their maturation and differentiation into matrix-secreting osteoblasts. Osteogenesis occurs not only during embryogenesis but also during growth, after an injury, and in normal homeostatic maintenance. While much is known about osteogenesis-associated regulatory genes, the role of microRNAs (miRNAs), which are epigenetic regulators of protein expression, is just beginning to be explored. While miRNAs do not abrogate all protein expression, their purpose is to finely tune it, allowing for a timely and temporary protein down-regulation.

RECENT FINDINGS

The last decade has unveiled a multitude of miRNAs that regulate key proteins within the osteogenic lineage, thus qualifying them as "ostemiRs." These miRNAs may endogenously target an activator or inhibitor of differentiation, and depending on the target, may either lead to the prolongation of a progenitor maintenance state or to early differentiation. Interestingly, cellular identity seems intimately coupled to the expression of miRNAs, which participate in the suppression of previous and subsequent differentiation steps. In such cases where key osteogenic proteins were identified as direct targets of miRNAs in non-bone cell types, or through bioinformatic prediction, future research illuminating the activity of these miRNAs during osteogenesis will be extremely valuable. Many bone-related diseases involve the dysregulation of transcription factors or other proteins found within osteoblasts and their progenitors, and the dysregulation of miRNAs, which target such factors, may play a pivotal role in disease etiology, or even as a possible therapy.

Intranasal administration of mesenchymoangioblast-derived mesenchymal stem cells abrogates airway fibrosis and airway hyperresponsiveness associated with chronic allergic airways disease

Structural changes known as airway remodeling (AWR) characterize chronic/severe asthma and contribute to lung dysfunction. Thus, we assessed the in vivo efficacy of induced pluripotent stem cell and mesenchymoangioblast-derived mesenchymal stem cells (MCA-MSCs) on AWR in a murine model of chronic allergic airways disease (AAD)/asthma. Female Balb/c mice were subjected to a 9-wk model of ovalbumin (Ova)-induced chronic AAD and treated intravenously or intranasally with MCA-MSCs from weeks 9 to 11. Changes in airway inflammation (AI), AWR, and airway hyperresponsiveness (AHR) were assessed. Ova-injured mice presented with AI, goblet cell metaplasia, epithelial thickening, increased airway TGF-β1 levels, subepithelial myofibroblast and collagen accumulation, total lung collagen concentration, and AHR (all P < 0.001 vs. uninjured control group). Apart from epithelial thickness, all other parameters measured were significantly, although not totally, decreased by intravenous delivery of MCA-MSCs to Ova-injured mice. In comparison, intranasal delivery of MCA-MSCs to Ova-injured mice significantly decreased all parameters measured (all P < 0.05 vs. Ova group) and, most notably, normalized aberrant airway TGF-β1 levels, airway/lung fibrosis, and AHR to values measured in uninjured animals. MCA-MSCs also increased collagen-degrading gelatinase levels. Hence, direct delivery of MCA-MSCs offers great therapeutic benefit for the AWR and AHR associated with chronic AAD.-Royce, S. G., Rele, S., Broughton, B. R. S., Kelly, K., Samuel, C. S. Intranasal administration of mesenchymoangioblast-derived mesenchymal stem cells abrogates airway fibrosis and airway hyperresponsiveness associated with chronic allergic airways disease.

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.

Mesenchymal stem cells and their therapeutic applications in inflammatory bowel disease

Mesenchymal stem or stromal cells (MSCs) are non-hematopoietic stem cells that facilitate tissue regeneration through mechanisms involving self-renewal and differentiation, supporting angiogenesis and tissue cell survival, and limiting inflammation. MSCs were originally identified and expanded in long-term cultures of cells from bone marrow and other organs; and their native identity was recently confined into pericytes and adventitial cells in vascularized tissue. The multipotency, as well as the trophic and immunosuppressive effects, of MSCs have prompted the rapid development of clinical applications for many diseases involving tissue inflammation and immune disorders, including inflammatory bowel disease. Although standard criteria have been established to define MSCs, their therapeutic efficacy has varied significantly among studies due to their natural heterogenicity. Thus, understanding the biological and immunological features of MSCs is critical to standardize and optimize MSCs-based therapy. In this review, we highlight the cellular and molecular mechanisms involved in MSCs-mediated tissue repair and immunosuppression. We also provide an update on the current development of MSCs-based clinical trials, with a detailed discussion of MSC-based cell therapy in inflammatory bowel disease.

iHMS: a database integrating human histone modification data across developmental stages and tissues

Background

Differences in chromatin states are critical to the multiplicity of cell states. Recently genome-wide histone modification maps of diverse human developmental stages and tissues have been charted.

Description

To facilitate the investigation of epigenetic dynamics and regulatory mechanisms in cellular differentiation processes, we developed iHMS, an integrated human histone modification database that incorporates massive histone modification maps spanning different developmental stages, lineages and tissues (http://www.tongjidmb.com/human/index.html). It also includes genome-wide expression data of different conditions, reference gene annotations, GC content and CpG island information. By providing an intuitive and user-friendly query interface, iHMS enables comprehensive query and comparative analysis based on gene names, genomic region locations, histone modification marks and cell types. Moreover, it offers an efficient browser that allows users to visualize and compare multiple genome-wide histone modification maps and related expression profiles across different developmental stages and tissues.

Conclusion

iHMS is of great helpfulness to understand how global histone modification state transitions impact cellular phenotypes across different developmental stages and tissues in the human genome. This extensive catalog of histone modification states thus presents an important resource for epigenetic and developmental studies.

Icariin-treated human umbilical cord mesenchymal stem cells decrease chronic liver injury in mice

Human umbilical cord mesenchymal stem cells (hUMSCs) have been shown to have multiple differentiation potentials. However, a key problem is that only a small number of hUMSCs can migrate to damaged tissue after transplantation. According to "The Theory of Kidney Essence" in Traditional Chinese Medicine, some traditional Chinese medicines used for tonifying the kidneys can be applied in promoting the differentiation and migration of stem cells in vivo. Our previous study demonstrated that icariin (ICA) could up-regulate the pluripotent genes of hUMSCs in vitro and induce cell migration in mice in an acute kidney injury model in vivo. The aim of this study was to investigate the effects of ICA-induced hUMSCs in chronic liver injury (CLI) caused by carbon tetrachloride (CCl4). CLI was induced by intraperitoneal injection of CCl4. ICA-treated hUMSCs were transplanted via intra-venous injection. The animals were followed for survival, biochemistry analysis and pathology. The results show that ICA-treated hUMSCs accelerate the recovery of liver function in mice with CLI. In addition, ICA-treated hUMSCs increase the anti-oxidant activities in liver and prevent the progression to hepatic fibrosis. Moreover, ICA induces the migration of hUMSCs to the injured liver tissue. In conclusion, these data demonstrate that ICA-treated hUMSCs exhibit recovery and protective properties in the mice model of CCl4-induced CLI.

Stromal Cell Subsets Directing Neonatal Spleen Regeneration

Development of lymphoid tissue is determined by interactions between stromal lymphoid tissue organiser (LTo) and hematopoietic lymphoid tissue inducer (LTi) cells. A failure for LTo to receive appropriate activating signals during embryogenesis through lymphotoxin engagement leads to a complete cessation of lymph node (LN) and Peyer's patch development, identifying LTo as a key stromal population for lymphoid tissue organogenesis. However, little is known about the equivalent stromal cells that induce spleen development. Here, by dissociating neonatal murine spleen stromal tissue for re-aggregation and transplant into adult mouse recipients, we have identified a MAdCAM-1⁺CD31⁺CD201⁺ spleen stromal organizer cell-type critical for new tissue formation. This finding provides an insight into the regulation of post-natal spleen tissue organogenesis, and could be exploited in the development of spleen regenerative therapies.

Dynamic epigenetic mode analysis using spatial temporal clustering

Background

Differentiation of human embryonic stem cells requires precise control of gene expression that depends on specific spatial and temporal epigenetic regulation. Recently available temporal epigenomic data derived from cellular differentiation processes provides an unprecedented opportunity for characterizing fundamental properties of epigenomic dynamics and revealing regulatory roles of epigenetic modifications.

Results

This paper presents a spatial temporal clustering approach, named STCluster, which exploits the temporal variation information of epigenomes to characterize dynamic epigenetic mode during cellular differentiation. This approach identifies significant spatial temporal patterns of epigenetic modifications along human embryonic stem cell differentiation and cluster regulatory sequences by their spatial temporal epigenetic patterns.

Conclusions

The results show that this approach is effective in capturing epigenetic modification patterns associated with specific cell types. In addition, STCluster allows straightforward identification of coherent epigenetic modes in multiple cell types, indicating the ability in the establishment of the most conserved epigenetic signatures during cellular differentiation process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1331-z) contains supplementary material, which is available to authorized users.

Priming of endothelial colony-forming cells in a mesenchymal niche improves engraftment and vasculogenic potential by initiating mesenchymal transition orchestrated by NOTCH signaling

The prospect of using endothelial progenitors is currently hampered by their low engraftment upon transplantation. We report that mesenchymal stem/stromal cells (MSCs), independent of source and age, improve the engraftment of endothelial colony forming cells (ECFCs). MSC coculture altered ECFC appearance to an elongated mesenchymal morphology with reduced proliferation. ECFC primed via MSC contact had reduced self-renewal potential, but improved capacity to form tube structures in vitro and engraftment in vivo Primed ECFCs displayed major differences in transcriptome compared to ECFCs never exposed to MSCs, affecting genes involved in the cell cycle, up-regulating of genes influencing mesenchymal transition, adhesion, extracellular matrix. Inhibition of NOTCH signaling, a potential upstream regulator of mesenchymal transition, in large part modulated this gene expression pattern and functionally reversed the mesenchymal morphology of ECFCs. The collective results showed that primed ECFCs survive better and undergo a mesenchymal transition that is dependent on NOTCH signaling, resulting in significantly increased vasculogenic potential.-Shafiee, A., Patel, J., Wong, H. Y., Donovan, P., Hutmacher, D. W., Fisk, N. M., Khosrotehrani, K. Priming of endothelial colony-forming cells in a mesenchymal niche improves engraftment and vasculogenic potential by initiating mesenchymal transition orchestrated by NOTCH signaling.

Vascular Transdifferentiation in the CNS: A Focus on Neural and Glioblastoma Stem-Like Cells

Glioblastomas are devastating and extensively vascularized brain tumors from which glioblastoma stem-like cells (GSCs) have been isolated by many groups. These cells have a high tumorigenic potential and the capacity to generate heterogeneous phenotypes. There is growing evidence to support the possibility that these cells are derived from the accumulation of mutations in adult neural stem cells (NSCs) as well as in oligodendrocyte progenitors. It was recently reported that GSCs could transdifferentiate into endothelial-like and pericyte-like cells both in vitro and in vivo, notably under the influence of Notch and TGFβ signaling pathways. Vascular cells derived from GBM cells were also observed directly in patient samples. These results could lead to new directions for designing original therapeutic approaches against GBM neovascularization but this specific reprogramming requires further molecular investigations. Transdifferentiation of nontumoral neural stem cells into vascular cells has also been described and conversely vascular cells may generate neural stem cells. In this review, we present and discuss these recent data. As some of them appear controversial, further validation will be needed using new technical approaches such as high throughput profiling and functional analyses to avoid experimental pitfalls and misinterpretations.

A portable platform for stepwise hematopoiesis from human pluripotent stem cells within PET-reinforced collagen sponges

Various systems for differentiating hematopoietic cells from human pluripotent stem cells (PSCs) have been developed, although none have been fully optimized. In this report, we describe the development of a novel three-dimensional system for differentiating hematopoietic cells from PSCs using collagen sponges (CSs) reinforced with poly(ethylene terephthalate) fibers as a scaffold. PSCs seeded onto CSs were differentiated in a stepwise manner with appropriate cytokines under serum-free and feeder-free conditions. This process yielded several lineages of floating hematopoietic cells repeatedly for more than 1 month. On immunohistochemical staining, we detected CD34+ cells and CD45+ cells in the surface and cavities of the CS. Taking advantage of the portability of this system, we were able to culture multiple CSs together floating in medium, making it possible to harvest large numbers of hematopoietic cells repeatedly. Given these findings, we suggest that this novel three-dimensional culture system may be useful in the large-scale culture of PSC-derived hematopoietic cells.

Brown-like adipose progenitors derived from human induced pluripotent stem cells: Identification of critical pathways governing their adipogenic capacity

Human induced pluripotent stem cells (hiPSCs) show great promise for obesity treatment as they represent an unlimited source of brown/brite adipose progenitors (BAPs). However, hiPSC-BAPs display a low adipogenic capacity compared to adult-BAPs when maintained in a traditional adipogenic cocktail. The reasons of this feature are unknown and hamper their use both in cell-based therapy and basic research. Here we show that treatment with TGFβ pathway inhibitor SB431542 together with ascorbic acid and EGF were required to promote hiPSCs-BAP differentiation at a level similar to adult-BAP differentiation. hiPSC-BAPs expressed the molecular identity of adult-UCP1 expressing cells (PAX3, CIDEA, DIO2) with both brown (ZIC1) and brite (CD137) adipocyte markers. Altogether, these data highlighted the critical role of TGFβ pathway in switching off hiPSC-brown adipogenesis and revealed novel factors to unlock their differentiation. As hiPSC-BAPs display similarities with adult-BAPs, it opens new opportunities to develop alternative strategies to counteract obesity.

Generating human hematopoietic stem cells in vitro -exploring endothelial to hematopoietic transition as a portal for stemness acquisition

Advances in cellular reprogramming technologies have created alternative platforms for the production of blood cells, either through inducing pluripotency in somatic cells or by way of direct conversion of nonhematopoietic cells into blood cells. However, de novo generation of hematopoietic stem cells (HSCs) with robust and sustained multilineage engraftment potential remains a significant challenge. Hemogenic endothelium (HE) has been recognized as a unique transitional stage of blood development from mesoderm at which HSCs arise in certain embryonic locations. The major aim of this review is to summarize historical perspectives and recent advances in the investigation of endothelial to hematopoietic transition (EHT) and HSC formation in the context of aiding in vitro approaches to instruct HSC fate from human pluripotent stem cells. In addition, direct conversion of somatic cells to blood and HSCs and progression of this conversion through HE stage are discussed. A thorough understanding of the intrinsic and microenvironmental regulators of EHT that lead to the acquisition of self-renewal potential by emerging blood cells is essential to advance the technologies for HSC production and expansion.

Mesenchymal Stem and Progenitor Cells in Normal and Dysplastic Hematopoiesis-Masters of Survival and Clonality?

Myelodysplastic syndromes (MDS) are malignant hematopoietic stem cell disorders that have the capacity to progress to acute myeloid leukemia (AML). Accumulating evidence suggests that the altered bone marrow (BM) microenvironment in general, and in particular the components of the stem cell niche, including mesenchymal stem cells (MSCs) and their progeny, play a pivotal role in the evolution and propagation of MDS. We here present an overview of the role of MSCs in the pathogenesis of MDS, with emphasis on cellular interactions in the BM microenvironment and related stem cell niche concepts. MSCs have potent immunomodulatory capacities and communicate with diverse immune cells, but also interact with various other cellular components of the microenvironment as well as with normal and leukemic stem and progenitor cells. Moreover, compared to normal MSCs, MSCs in MDS and AML often exhibit altered gene expression profiles, an aberrant phenotype, and abnormal functional properties. These alterations supposedly contribute to the “reprogramming” of the stem cell niche into a disease-permissive microenvironment where an altered immune system, abnormal stem cell niche interactions, and an impaired growth control lead to disease progression. The current article also reviews molecular targets that play a role in such cellular interactions and possibilities to interfere with abnormal stem cell niche interactions by using specific targeted drugs.