scholarly journals Generating Large Numbers of Human Megakaryocytes from Pluripotent Stem Cells

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4289-4289
Author(s):  
Jaspreet Gill ◽  
Leon Lin ◽  
Marta A. Walasek ◽  
Stephen J. Szilvassy ◽  
Wing Chang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Lines ◽  
Pluripotent Stem Cells ◽  
Culture System ◽  
Method Development ◽  
Immunofluorescence Microscopy ◽  
Dna Ploidy ◽  
Scale Up ◽  
Embryonic Stem ◽  
Hematopoietic Stem

Abstract The process of hemostasis and blood coagulation relies heavily on a sufficient supply of platelets (PLTs, also known as thrombocytes) within a person's bloodstream. Platelet transfusion is an effective treatment for thrombocytopenia-related diseases, yet paucity of supply and limited shelf-life (5 - 7 days) remain challenging. PLTs are generated by the proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs) into megakaryocytes (MKs), a rare subset of large polyploid bone marrow cells. Methods to produce MKs in vitro by inducing mesodermal specification and hematopoietic differentiation of human pluripotent stem cells (hPSCs) could provide a reliable and safe supply of PLTs for transfusion and would also be amenable to gene editing for generation of HLA-null universal PLTs. Culture methods to generate hPSC-derived MKs and PLTs have been described, yet published protocols lack standardization, are PSC line dependent and/or promote differentiation of other lineages, resulting in low MK cell yields and purity. The use of feeder cells and/or viral vectors also limits the clinical and scale-up applicability. Here, we describe an efficient feeder cell-free and serum-free culture system that promotes the selective differentiation of hPSCs from multiple ES and iPS lines into polyploid MKs with high purity and yields and ability to generate platelets. The 17-day protocol includes two stages: a 12-day stage to differentiate hPSCs into megakaryocytic-biased HSPCs through endothelial-to-hematopoietic transition (H-phase), and a 5-day stage to further differentiate HSPCs into mature MKs (MK-phase). at the start of the H-phase, hPSC aggregates were plated in mTeSR TM media on Matrigel ®-coated plates at 16 aggregates (100 - 200 µm in diameter, ~100 cells per aggregate) per cm 2 to allow attachment overnight (Day -1). The cells were then cultured in mesoderm-induction medium for 3 days (Day 0 - 3), and subsequently in hematopoietic specification medium for 9 days (Day 3 - 12). During this phase, PSC-derived HSPCs emerged from an adherent layer of endothelial cells and were released into suspension. On day 12 these nonadherent cells were harvested and seeded at 1 - 3.5 × 10 5 cells/mL in MK maturation medium containing thrombopoietin (TPO) and other hematopoietic growth factors and cultured for 5 additional days (MK-phase, Day 12 - 17). At the end of H-phase (day 12) and MK-phase (day 17) the cells were counted and assessed for HSPC markers (CD34/CD45), the erythroid marker glycophorin A (GlyA), MK markers (CD41a/CD42b), DNA ploidy profile and PLT production by flow cytometry and immunofluorescence microscopy. Two embryonic stem (ES) cell lines (H1 and H9), and two induced pluripotent stem (iPS) cell lines (WLS-1C and STiPS-R038) were used in this study. At the end of H-phase (Day 12), on average 48% (range: 34 - 72%) of cells released into suspension co-expressed CD41a and CD42b markers, with an average yield of 93 CD41a +CD42b + cells per seeded hPSC (range: 30 - 200, n = 4 for H9/1C, n = 3 for H1/R038). The cells also expressed CD34 (average of 78% CD34 + cells) and GlyA (average of 71% GlyA + cells), indicating that the H-phase may support differentiation of PSCs to megakaryocyte-erythroid progenitors. At the end of MK-phase (Day 17), on average 82% of the cells expressed CD41a (range: 70 - 99%), 62% of the cells co-expressed CD41a and CD42b (range: 40 - 85%), and an average of 253 CD41a +CD42b + cells were generated per seeded hPSC (range: 70 - 700 MKs, n = 11 for H1/H9/R038, n = 7 for 1C). Of note, less than 5% of cells expressed GlyA, showing that the culture system is specific for megakaryocytic differentiation. The DNA ploidy profile of the CD41a +CD42b + cells generated on Day 17 showed that on average 26% and 9% of cells had 4N and 8N+ DNA ploidy, respectively (n = 11). Multinucleated MKs could also be readily observed by immunofluorescence microscopy. These PSC-derived MKs produced an average of 3.5 PLTs (range: 1 - 10 PLTs, n = 11) based on viable CD41a +CD45 -GlyA - PLT-like particles with a similar size and CD41 expression as control PLTs prepared from fresh blood. In conclusion, we have developed a simple two-step, yet robust serum- and feeder-free culture system for generating high numbers of hPSC-MKs that are large, polyploid, and capable of shedding PLTs. This culture method provides a platform to study thrombopoiesis and is amenable to scale-up method development. Disclosures No relevant conflicts of interest to declare.

216 EMBRYONIC AND INDUCED PLURIPOTENT STEM CELLS ANALOGOUS TO INNER CELL MASS-DERIVED LIF-DEPENDENT MOUSE EMBRYONIC STEM CELLS ESTABLISHED FROM THE DOMESTIC PIG, SUS SCROFA

2012 ◽  
Vol 24 (1) ◽  
pp. 220
Author(s):  
B. P. Telugu ◽  
T. Ezashi ◽  
A. Alexenko ◽  
S. Lee ◽  
R. S. Prather ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Induced Pluripotent Stem Cells ◽  
Cell Lines ◽  
Umbilical Cord ◽  
Pluripotent Stem Cells ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Induced Pluripotent

Authentic embryonic stem cells (ESC) may never have been successfully derived from the inner cell mass (ICM) of pig and other ungulates, despite over 25 years of effort. Recently, porcine induced pluripotent stem cells (piPSC) were generated by reprogramming somatic cells with a combination of four factors OCT4, SOX2, KLF4 and c-MYC (OSKM) delivered by lentiviral transduction. The established piPSC are analogous to FGF2-dependent human (h) ESC and murine “epiblast stem cells,” and are likely to advance swine as a model in biomedical research. Here, we report for the first time, the establishment of LIF-dependent, so called naïve type pluripotent stem cells (1) from the inner cell mass (ICM) of porcine blastocysts by up-regulating the expression of KLF4 and POU5F1; and (2) from umbilical cord mesenchyme (Wharton's jelly) by transduction with OSKM factors and subsequent culture in the presence of LIF-based medium with inhibitors that substitute for low endogenous expression of c-MYC and KLF4 and promote pluripotency. The 2 compounds that have been used in this study are, CHIR99021 (CH), which substitutes c-MYC by inhibiting GSK3B and activating WNT signalling and Kenpaullone (KP), which inhibits both GSK3B and CDK1 and supplants KLF4 function. The lentiviral vectors employed for introducing the re-programming genes were modified for doxycycline-mediated induction of expression (tet-on) and are ‘floxed’ for Cre-mediated recombination and removal of transgenes following complete reprogramming. Two LIF-dependent cell lines have been derived from the ICM cells of late d 5.5 in vitro produced blastocysts and four from umbilical cord mesenchyme recovered from fetuses at d 35 of pregnancy. The derived stem cell lines are alkaline phosphatase-positive, resemble mouse embryonic stem cells in colony morphology, cell cycle interval, transcriptome profile and expression of pluripotent markers, such as POU5F1, SOX2 and surface marker SSEA1. They are dependent on LIF signalling for maintenance of pluripotency, can be cultured over extended passage (>50) with no senescence. Of importance, the ICM-derived lines have been successful in their ability to form teratomas. The cells could be cultured in feeder free conditions on a synthetic matrix in the presence of chemically defined medium and can be coaxed to differentiate under xeno-free conditions. Currently, the piPSC lines are being investigated for their ability to give rise to teratomas and to produce a live offspring by nuclear transfer. Supported by Addgene Innovation Award, MO Life Sciences Board Grant 00022147 and NIH grant HD21896.

scholarly journals Generation of CD34+CD43+ hematopoietic progenitors to induce thymocytes from human pluripotent stem cells

2021 ◽  
Author(s):  
Lea Flippe ◽  
Anne Gaignerie ◽  
Celine Serazin ◽  
Olivier Baron ◽  
Xavier Saulquin ◽  
...  
Keyword(s):  
Stem Cells ◽  
T Cells ◽  
Pluripotent Stem Cells ◽  
High Efficiency ◽  
Embryonic Stem ◽  
Human Pluripotent Stem Cells ◽  
Blood Type ◽  
Hematopoietic Stem ◽  
Similar Profile

Immunotherapy using primary T cells has revolutionized medical care in some pathologies in recent years but limitations associated to challenging cell genome edition, insufficient cell number production, the use of only autologous cells and lack of product standardization have limited its uses in the clinic. The alternative use of T cells generated in vitro from human pluripotent stem cells (hPSCs) offers great advantages by providing a self-renewing source of T cells that can be readily genetically modified and facilitate the use of standardized universal off-the-shelf allogeneic cell products and rapid clinic access. However, despite their potential, the feasibility and functionality of T-cells differentiated from hPSCs needs better comprehension before moving to the clinic. In this study, we generated human induced pluripotent stem cells from T-cells (T-iPSCs) allowing preservation of already recombined TCR, with the same properties as human embryonic stem cells (hESCs). Based on these cells, we differentiated with high efficiency hematopoietic progenitor stem cells (HPSCs), capable of self-renewal and differentiation into any cell blood type, and then DN3a thymic progenitors from several T-iPSC lines. To better comprehend differentiation, we analyzed the transcriptomic profiles of the different cell types and demonstrated that HPSCs differentiated from hiPSCs had a very similar profile to cord blood hematopoietic stem cells (HSCs). Furthermore, differentiated T-cell progenitors had a similar profile to thymocytes at the DN3a stage of thymic lymphopoiesis. Therefore, with this approach, we were able to regenerate precursors of therapeutic human T cells to potentially treat a wide number of diseases.

scholarly journals Experimental Limitations Using Reprogrammed Cells for Hematopoietic Differentiation

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Katharina Seiler ◽  
Motokazu Tsuneto ◽  
Fritz Melchers
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Pluripotent Stem Cells ◽  
Somatic Cells ◽  
Embryonic Stem ◽  
Clinical Settings ◽  
Hematopoietic Differentiation ◽  
Hematopoietic Stem ◽  
Induced Pluripotent

We review here our experiences with thein vitroreprogramming of somatic cells to induced pluripotent stem cells (iPSC) and subsequentin vitrodevelopment of hematopoietic cells from these iPSC and from embryonic stem cells (ESC). While, in principle, thein vitroreprogramming and subsequent differentiation can generate hematopoietic cell from any somatic cells, it is evident that many of the steps in this process need to be significantly improved before it can be applied to human cells and used in clinical settings of hematopoietic stem cell (HSC) transplantations.

Hematopoietic Differentiation of Human Embryonic Stem Cells in Vitro : Comparison of Three Cell Lines

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4787-4787
Author(s):  
Marion Brenot ◽  
Annelise Bennaceur-Griscelli ◽  
Marc Peschanski ◽  
Maria Teresa Mitjavila-Garcia
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Cell Lines ◽  
Human Embryonic Stem Cells ◽  
Hematopoietic Cells ◽  
Embryonic Stem ◽  
Embryoid Bodies ◽  
Hematopoietic Differentiation ◽  
Hematopoietic Stem

Abstract Human embryonic stem cells (hES) isolated from the inner cell mass of a blastocyst have the ability to self renew indefinitely while maintaining their pluripotency to differentiate into multiple cell lineages. Therefore, hES represent an important source of cells for perspective cell therapies and serve as an essential tool for fundamental research, specifically for understanding pathophysiological mechanisms of human diseases for the development of novel pharmacological drugs. The generation of hematopoietic stem cells from hES may serve as an alternative source of cells for hematopoietic reconstitution following bone marrow transplantation and an interesting approach to understand early stages of hematopoietic development which are difficult to study in human embryos. Using two different methods, we have differentiated three hES cell lines (SA01, H1 and H9) into hematopoietic cells by generating embryoid bodies and co-culturing on the murine Op9 cell line. In both experimental approaches, we obtain cells expressing CD34 and when cultured in hematopoietic conditions, SA01 and H1 cell lines differentiate into various hematopoietic lineages as demonstrated by BFU-E, CFU-GM and CFU-GEMM colony formation, whereas H9 have almost exclusively granulo-macrophage differentiation. Cells composing these hematopoietic colonies express CD45, CD11b, CD31, CD41 and CD235 and staining with May Grundwald-Giemsa demonstrate neutrophil and erythrocyte morphology. These results demonstrate the capacity of hES to differentiate into mature hematopoietic cells in vitro. Nevertheless, there exist some quantitative and qualitative differences about hematopoietic differentiation between the hES cell lines used. However, we still have to evaluate their capacity to reconstitute hematopoiesis in vivo in an immune deficient mouse model. We will also be interested in developing in vitro methods to expand these hematopoietic precursor cells derived from hES which may be used as a viable source for future cell therapy.

Evidence That Human Very Small Embryonic-Like Stem Cells (VSELs) Are Mobilized by G-CSF Into Peripheral Blood: A Novel Strategy to Obtain Human Pluripotent Stem Cells for Regenerative Medicine.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1474-1474
Author(s):  
Satish Medicetty ◽  
Mariusz Z Ratajczak ◽  
Magdalena J Kucia ◽  
Ewa K. Zuba-Surma ◽  
Izabela Klich ◽  
...  
Keyword(s):  
Stem Cells ◽  
Regenerative Medicine ◽  
Pluripotent Stem Cells ◽  
Peripheral Blood ◽  
Embryonic Stem ◽  
Human Pluripotent Stem Cells ◽  
Employment Equity ◽  
Hematopoietic Stem ◽  
Equity Ownership ◽  
Novel Strategy

Abstract Abstract 1474 Poster Board I-497 We previously demonstrated that human cord blood contains a population of small (smaller in size than erythrocytes) CXCR4+CD133+CD34+SSEA-4+Oct-4+lin−CD45− cells (Leukemia 2007:21;297-303) and that these cells are mobilized into peripheral blood during tissue organ damage as seen for example in heart infarct (J. Am. Coll. Cardiol., 2009:53;1-9.) or stroke (Stroke. 2009:40;1237.). Similar cells were also reported in murine organs, and more importantly we described that these cells may differentiate in vitro into cells from all three germ layers (Leukemia 2006:20;857–869). To explore the possibility that human VSELs could become a source of pluripotent stem cells in regenerative medicine, our goal was to develop an efficient strategy to isolate these cells from adult patients. To test if VSELs similarly to their murine counterparts could be mobilized into peripheral blood after granulocyte colony stimulating factor (G-CSF) injection (Stem Cells 2008:26;2083-2092), we enrolled a group of young healthy donors who were mobilized for two consecutive days using G-CSF (480 μg/day subcutaneously). On the third day nucleated cells (TNC) were collected by apheresis. We evaluated number of VSELs in peripheral blood (PB) samples before and after G-CSF mobilization as well as the final number in the apheresis product. At least 1 million of TNC were acquired and analyzed by FACS Diva software. Three different fractions of non-hematopoietic stem cells enriched for VSELs (Lin−/CD45−/CD133+, Lin−/CD45−/CD34+, Lin−/CD45−/CXCR4+) as well as their CD45 positive hematopoietic counterparts were analyzed. The absolute numbers of cells from each population, contained in 1 μL of sample, were computed based on percent content of each population and TNC count for each individual sample. Results show that after G-CSF mobilization, human peripheral blood contains a population of lin− CD45− mononuclear cells that express CXCR4, CD34 and CD133 antigens. These lin− CD45− CXCR4+ CD133+ CD34+ cells are highly enriched for mRNA for intra-nuclear pluripotent embryonic transcription factors such as Oct-4, Sox2 and Nanog. More importantly we found that Oct-4 was expressed in nuclei of mobilized VSELs and that these cells also express the cell surface marker SSEA-4, the early embryonic glycolipid antigen commonly used as a marker for undifferentiated pluripotent human embryonic stem cells. We observed that these adult peripheral blood-derived VSELs are slightly larger than their counterparts identified in adult murine bone marrow, but are still very small. In addition, they also possess large nuclei containing embryonic-type unorganized euchromatin. Before G-CSF mobilization only very few VSELs were detectable in peripheral blood, whereas following G-CSF induced mobilization there was a very significant increase with in excess of 106 VSELs present in the apheresis product representing less than 0.01% of TNC. We postulate that while VSELs are relatively rare cells, they are mobilized into peripheral blood and that G-CSF induced mobilization could become a novel strategy to obtain human pluripotent stem cells for regenerative medicine. Disclosures: Medicetty: NeoStem Inc: Employment, Equity Ownership. Marasco: NeoStem Inc: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Rodgerson: NeoStem Inc: Employment, Equity Ownership.

scholarly journals Generation and Characterization of Erythroid Cells from Human Embryonic Stem Cells and Induced Pluripotent Stem Cells: An Overview

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Kai-Hsin Chang ◽  
Halvard Bonig ◽  
Thalia Papayannopoulou
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Induced Pluripotent Stem Cells ◽  
Human Embryonic Stem Cells ◽  
Pluripotent Stem Cells ◽  
Embryonic Stem ◽  
Erythroid Cells ◽  
Hematopoietic Stem ◽  
Induced Pluripotent

Because of the imbalance in the supply and demand of red blood cells (RBCs), especially for alloimmunized patients or patients with rare blood phenotypes, extensive research has been done to generate therapeutic quantities of mature RBCs from hematopoietic stem cells of various sources, such as bone marrow, peripheral blood, and cord blood. Since human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) can be maintained indefinitely in vitro, they represent potentially inexhaustible sources of donor-free RBCs. In contrast to other ex vivo stem-cell-derived cellular therapeutics, tumorigenesis is not a concern, as RBCs can be irradiated without marked adverse effects on in vivo function. Here, we provide a comprehensive review of the recent publications relevant to the generation and characterization of hESC- and iPSC-derived erythroid cells and discuss challenges to be met before the eventual realization of clinical usage of these cells.

Hematopoietic progenitor/stem cells immortalized byLhx2 generate functional hematopoietic cells in vivo

Blood ◽  
2002 ◽  
Vol 99 (11) ◽  
pp. 3939-3946 ◽  
Author(s):  
Perpétua Pinto do Ó ◽  
Karin Richter ◽  
Leif Carlsson
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Embryonic Stem Cells ◽  
Cell Lines ◽  
Embryonic Stem ◽  
Hematopoietic Progenitor Cell ◽  
Hematopoietic Progenitor ◽  
Generate Functional ◽  
Hematopoietic Stem

Hematopoietic stem cells (HSCs) are unique in their capacity to maintain blood formation following transplantation into immunocompromised hosts. Expansion of HSCs in vitro is therefore important for many clinical applications but has met with limited success because the mechanisms regulating the self-renewal process are poorly defined. We have previously shown that expression of the LIM-homeobox gene Lhx2 in hematopoietic progenitor cells derived from embryonic stem cells differentiated in vitro generates immortalized multipotent hematopoietic progenitor cell lines. However, HSCs of early embryonic origin, including those derived from differentiated embryonic stem cells, are inefficient in engrafting adult recipients upon transplantation. To address whetherLhx2 can immortalize hematopoietic progenitor/stem cells that can engraft adult recipients, we expressed Lhx2 in hematopoietic progenitor/stem cells derived from adult bone marrow. This approach allowed for the generation of immortalized growth factor–dependent hematopoietic progenitor/stem cell lines that can generate erythroid, myeloid, and lymphoid cells upon transplantation into lethally irradiated mice. When transplanted into stem cell–deficient mice, these cell lines can generate a significant proportion of circulating erythrocytes in primary, secondary, and tertiary recipients for at least 18 months. Thus, Lhx2immortalizes multipotent hematopoietic progenitor/stem cells that can generate functional progeny following transplantation into lethally irradiated hosts and can long-term repopulate stem cell–deficient hosts.

scholarly journals Expression Patterns of Cancer-Testis Antigens in Human Embryonic Stem Cells and Their Cell Derivatives Indicate Lineage Tracks

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Nadya Lifantseva ◽  
Anna Koltsova ◽  
Tatyana Krylova ◽  
Tatyana Yakovleva ◽  
Galina Poljanskaya ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Pluripotent Stem Cells ◽  
Expression Patterns ◽  
Embryonic Stem ◽  
Cancer Cell Lines ◽  
Cancer Testis Antigens ◽  
Hes Cells ◽  
Cancer Testis

Pluripotent stem cells can differentiate into various lineages but undergo genetic and epigenetic changes during long-term cultivation and, therefore, require regular monitoring. The expression patterns of cancer-testis antigens (CTAs) MAGE-A2, -A3, -A4, -A6, -A8, -B2, and GAGE were examined in undifferentiated human embryonic stem (hES) cells, their differentiated derivatives, teratocarcinoma (hEC) cells, and cancer cell lines of neuroectodermal and mesodermal origin. Undifferentiated hES cells and embryoid body cells expressed MAGE-A3, -A6, -A4, -A8, and GAGEs while later differentiated derivatives expressed only MAGE-A8 or MAGE-A4. Likewise, mouse pluripotent stem cells also express CTAs of Magea but not Mageb family. Despite similarity of the hES and hEC cell expression patterns, MAGE-A2 and MAGE-B2 were detected only in hEC cells but not in hES cells. Moreover, our analysis has shown that CTAs are aberrantly expressed in cancer cell lines and display low tissue specificity. The identification of CTA expression patterns in pluripotent stem cells and their derivatives may be useful for isolation of abnormally CTA-expressing cells to improve the safety of stem-cell based therapy.

scholarly journals RUNX1a Enhances Hematopoietic Lineage Commitment From Human Embryonic Stem Cells and Inducible Pluripotent Stem Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 347-347
Author(s):  
Dan Ran ◽  
Wei-Jong Shia ◽  
Miao-Chia Lo ◽  
Junbao Fan ◽  
David A. Knorr ◽  
...  
Keyword(s):  
Stem Cells ◽  
Flow Cytometry ◽  
Pluripotent Stem Cells ◽  
Blood Cells ◽  
Embryonic Stem ◽  
Lineage Commitment ◽  
Hematopoietic Differentiation ◽  
Flow Cytometry Analysis ◽  
Hematopoietic Stem

Abstract Abstract 347 Both human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) are pluripotent stem cells (hPSCs) with potential to differentiate into all types of somatic cells. Patients suffering from blood disorders can be cured with hematopoietic cell transplantations (HCT). Technical advancements in hPSC production and handling have revolutionized their potential applications in regenerative medicine and provided enormous hope for patients who may need HCT. hiPSCs derived from autologous cells could provide unlimited leukocyte antigen matched blood cells on a patient-specific basis. A remaining hurdle in this process remains the need for efficient and effective generation of specific blood cells from hPSCs for therapeutic use. Transcription factors play key roles in regulating maintenance, expansion, and differentiation of blood cells from hPSCs. Studies have shown that transcription factor RUNX1 is required for the formation of definitive blood cells. There are several alternatively spliced isoforms of the RUNX1 protein, including the shortest form RUNX1a and two longer forms RUNX1b and RUNX1c. Based on known properties of RUNX1 proteins, we hypothesized that RUNX1a promotes the production of therapeutic hematopoietic stem cells from hPSCs. By employing ectopic expression of RUNX1a on different human ESC and iPSC lines (H9, BC1, iCB5) under a defined hematopoietic differentiation system, we aimed to identify function of RUNX1a on lineage commitment and molecular mechanisms of RUNX1 activity in differentiation of PSCs to hematopoietic cells. We demonstrated that expression of endogenous RUNX1a parallels lineage commitment and hematopoietic emergence from hPSCs. During differentiation process RUNX1a enhanced the expression of several mesoderm and hematopoietic differentiation related factors, including KDR, SCL, GATA2, and PU.1. In addition, over-expression of RUNX1a in embryoid bodies (EBs) showed more efficient and earlier emergence of typical sac structures, which predicts cell lineage commitment and germ layer development at the early stage of EB differentiation. At day 7, EBs derived from hPSCs was dissociated into single cells for flow cytometry analysis. The mean frequency of CD31+CD34+CD45− and total CD34+ cells with hemato-endothelial cell features are 35.1% and 67.1% from RUNX1a-overexpressing EBs, and 8.7% and 24.1% from vector control EBs. Immunohistochemistry analysis of EBs at day 9 of differentiation confirmed that expression of RUNX1a accelerated mesoderm commitment and emergence of hemato-endothelial precursors. Flow cytometry analysis on EBs collected at days 9, 11, 13 showed that ectopic RUNX1a induced a robust increase in the frequency of hematopoietic progenitor cells in all hPSC lines examined. At Day 9, RUNX1a-overexpressing EBs generated 48.5% CD43+CD45+ cells, 45.1% CD34+CD45+ cells, and 8.5 folds higher CD43+ cells than vector EBs. Later at Day 13, 80% CD45+ and 75% CD43+/CD34+CD45+ hematopoietic stem/progenitor cells (HSPCs) achieved from dissociated EBs. In liquid culture, RUNX1a HSPC showed strong expansion and high percentage of CD235a+CD45− (20%) and CD71+CD235a+ (16%), markers for erythroid populations. Flow cytometry and western blots on RUNX1a-EB formed colonies showed significantly higher β-globin production than that of the vector, suggesting expression of RUNX1a in HSPC enhanced definitive hematopoiesis. RUNX1a-hPSCs derived HSPCs possess self-renewal capability and are capable of differentiating into multi-lineages ex vivo. Furthermore HSPCs generated from RUNX1a-EBs possessed the capacity of interacting with surrogate niche and showed long-term repopulation ability under LTC-IC (Long-Term Culture-Initiating Cell Assay) condition. Colonies generated from HSPC of RUNX1a-EBs after 3 week bulk LTC-IC culture showed 300 folds higher than vector control. RUNX1a-hPSCs derived CD34+CD45+ cells could maintain a non-adherent population in ouldCD45+ sEBsND THIS SENTENCE5 week culture on stromal cell M210. In summary we identified that RUNX1a enhances derivation of definitive hematopoietic cells from human PSCs. Our study provides an important and useful system to enhance specificity and efficiency of generating functional blood cells and further differentiated cells from human PSCs, which may provide valuable source for future clinical applications in patients with hematologic disorders. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Mettl3 Mediated m6A Modification Is Essential in Fetal Hematopoiesis

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 3825-3825 ◽  
Author(s):  
Yimeng Gao ◽  
Radovan Vasic ◽  
Toma Tebaldi ◽  
Yuanbin Song ◽  
Rhea Teng ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Regulation Of Gene Expression ◽  
Embryonic Stem ◽  
Rna Modification ◽  
Hematopoietic Stem ◽  
Human Cd34

Abstract N6-methyladenosine (m6A) is the most abundant RNA modification, with key roles in RNA metabolism and regulation of gene expression. Recent studies have elucidated a role for m6A in normal hematopoiesis and myeloid malignancies. Constitutive deletion of the m6A methyltransferase Mettl3 in zebrafish enforces endothelial identity during the endothelial-to-hematopoietic transition, thus precluding normal developmental emergence of HSPCs. Studies conducted in human CD34+ cells, as well as human and murine AML cell lines have suggested that loss of METTL3 results in resolution of differentiation blockade, and impaired engraftment in murine transplantation assays. However, the effects of METTL3 deletion on hematopoietic stem cells in the context of an intact hematopoietic hierarchy in vivo have not yet been extensively characterized. To study the effects of Mettl3 deletion on the hematopoietic system in vivo, we generated Vav-Cre METTL3-/- (VCM3-/-) mice. Deletion of Mettl3 resulted in embryonic lethality, evidenced by skewing of Mendelian ratios at birth. Occasional stillborn VCM3-/- pups were smaller than wildtype littermates, and exhibited pallor, pancytopenia, and dramatically reduced marrow cellularity. To study the effects of Mettl3 deletion on embryonic hematopoiesis, we isolated fetal liver (FL) at embryonic day 14.5 for analysis. At E14.5, expected Mendelian ratios were preserved. Western blot and qPCR confirmed loss of Mettl3 expression in VCM3-/- mice. Reduction of total m6A levels in VCM3-/- mice was confirmed by ELISA. Flow cytometry for hematopoietic markers demonstrated a significant increase in the total number and frequency of Lin-Sca+c-Kit+ (LSK) cells in E14.5 VCM3-/- FL, with an increase in the frequency of HPC-1 (CD48+CD150-) and HPC-2 (CD48+CD150+) cells. To determine the function of VCM3-/- FL cells, we performed colony forming and transplantation assays. VCM3-/- FL cells demonstrated reduced colony forming ability in methylcellulose culture, and colonies that did arise were morphologically abnormal. VCM3-/- FL cells were also deficient in hematopoietic rescue assays, with all lethally irradiated recipient mice dying by day 14 post-transplant. Transplantation of CFSE labeled cells confirmed that absence of Mettl3 -/- hematopoiesis was not attributable to a homing defect. Competitive transplantation of VCM3-/- FL with Pep3b bone marrow similarly resulted in almost total loss of peripheral blood and bone marrow VCM3-/- engraftment, whereas mice transplanted with VCM3+/+ FL maintained chimerism at 8 weeks. Interestingly, VCM3-/- FL cells and FL LSK cells displayed no differences in apoptotic rate or cell cycle. To determine the mechanism underlying the observed phenotypes, we first performed RNA sequencing of VCM3+/+ and VCM3-/- FL LSK. Mettl3 deletion resulted in the increased expression of 701 transcripts, and reduced expression of 1395 transcripts. Gene ontology (GO) analysis revealed that upregulated genes were enriched for mitochondrial function, ribosome and ribonucleoprotein complex proteins and downregulated genes for cell adhesion and developmental processes. M6A RNA modification affects mRNA stability and translation. To determine the effect of m6A depletion on the hematopoieitic stem and progenitor cell proteome we are in the process of validating changes in protein levels of select genes essential in hematopoiesis. Previously, studies have demonstrated that deletion of METTL3 in human CD34+ hematopoietic cells and AML cell lines promote myeloid differentiation. Interestingly, we see a similar depletion of myeloid progenitors in VCM3-/- FL, with an increased percentage of mature myeloid CD11b+ cells. However, these results also coincide with an increased fraction of LSK HSPCs at E14.5. Interestingly, this resembles the METTL3 knockout phenotype in embryonic stem cells, which results in a reinforced naïve pluripotent state with impaired differentiation. Our ongoing studies seek to determine the role of m6A in FL HSC maintenance and differentiation. Disclosures No relevant conflicts of interest to declare.

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