Baffled-flow culture system enables the mass production of megakaryocytes from human embryonic stem cells by enhancing mitochondrial function
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ABSTRACT: Human embryonic stem cells (hESCs) have become an ideal cell source for the ex vivo generation of megakaryocyte (MK) and platelet products for clinical applications. However, an ongoing challenge is to establish scalable culture systems to maximize the yield of stem cell-derived MKs that release platelets. We defined a specific dynamic 3D manufacturing system that could remarkably facilitate megakaryopoiesis and increase the yield of platelet-producing MKs from hESCs within a 12-day induction period. Additionally, an increased number of > 16N ploidy MKs, proplatelets, and platelets were generated from induced cells harvested on day 12 using the specific dynamic culture method. The specific dynamic culture method significantly enhanced endothelium-to-hematopoietic transition and early hematopoiesis. More importantly, MK fate was significantly facilitated in a specific dynamic manner during early hematopoiesis. Mechanistically, this dynamic culture significantly enhanced mitochondrial function via the oxidative phosphorylation pathway and caused differentiation skewing of hESCs toward megakaryopoiesis. We defined a specific dynamic culture system in a baffled-flow manner that enabled the mass production of MKs from hESCs within 12 days. This study can aid in the automatic and scalable production of MKs from stem cells using baffled-flow bioreactors and assist in the manufacturing of hESC-derived MK and platelet products.
Project description:The hematopoietic system gives rise to a heterogeneous population of terminally differentiated cells that reside in the bone marrow (BM) to fulfill their roles in immunity, blood clotting and tissue oxygenation. Hematopoietic stem and progenitor cells are at the apex of a hierarchically organized maturation cascade constantly replenishing the pool of differentiated cells to maintain blood cell homeostasis. The bone marrow microenvironment is functionally compartmentalized by heterogeneous niche cells that provide physical and soluble signals to spatio-temporally organize hematopoiesis. Megakaryocytes (MKs) are niche cells of hematopoietic origin that support hematopoietic stem cell (HSCs) homeostasis and generate circulating platelets. Platelet production involves the release of MK fragments while their cell body is entirely consumed in a process termed thrombopoiesis. Consequently, replenishment of fragmented MKs from MK progenitors (termed megakaryopoiesis) is required to ensure sufficient platelet production, but also to maintain MK homeostasis within the HSC niche. Here, we used intravital imaging of the megakaryocytic lineage to identify the spatio-temporal patterns of megakaryopoiesis during steady state and thrombocytopenia. We show that MK consumption during thrombopoiesis is compensated by immediate and local proliferation of MK progenitors. MK homeostasis is controlled by plasmacytoid dendritic cells (pDCs) that scan the BM and secrete Interferon alpha (INFa) upon detection of exhausted megakaryocytes to trigger megakaryopoiesis. We identified local pDC-derived INFa release as a physiological inflammatory stimulus of the bone marrow niche that synchronizes megakaryopoiesis and thrombopoiesis to maintain homeostasis of MKs and platelets in steady state and under stress. Viral infection with SARS-CoV-2 can manipulate pDC-driven MK proliferation leading to inappropriate megakaryopoiesis, which has been associated with thrombotic complications during COVID-19.
Project description:Platelet homeostasis is essential for vascular integrity and immune defense. While the process of platelet formation by fragmenting megakaryocytes (thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of megakaryocytes (MKs) by their progenitor cells (megakaryopoiesis) remains unclear. Here we use intravital imaging to track the cellular dynamics of megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as homeostatic sensors that monitor the bone marrow for apoptotic MKs and deliver IFN- to the MK niche triggering local on-demand proliferation and maturation of MK progenitors. This fine-tuned coordination between thrombopoiesis and megakaryopoiesis is crucial for MK and platelet homeostasis in steady state and stress. However, excessive activation of pDCs, such as by viral infections, can disturb this homeostatic circuit. Accordingly, we show that pDCs activated by SARS-CoV2 drive inappropriate megakaryopoiesis. Together, we uncover a hitherto unknown pDC-dependent homeostatic circuit that involves innate immune sensing and demand-adapted release of inflammatory mediators to maintain tissue homeostasis of the megakaryocytic lineage.
Project description:Megakaryocyte (MK) differentiation is well described in morphologic terms but its molecular counterparts and the basis for platelet release are incompletely understood. We profiled mRNA expression in populations of primary mouse MKs representing successive differentiation stages. Genes associated with DNA replication are highly expressed in young MKs, in parallel with endomitosis. Intermediate stages are characterized by disproportionate expression of genes associated with the cytoskeleton, cell migration and G-protein signaling, whereas terminally mature MKs accumulate hemostatic factors, including many membrane proteins. We used these expression profiles to extract a reliable panel of molecular markers for MKs of early, intermediate or advanced differentiation, and establish its value using mouse models of defective thrombopoiesis resulting from absence of GATA-1, NF-E2 or tubulinß1. Computational analysis of the promoters of late-expressed MK genes identified new candidate targets for NF-E2, a critical transcriptional regulator of platelet release. One such gene encodes the kinase adaptor protein LIMS1/PINCH1, which is highly expressed in MKs and platelets and significantly reduced in NF-E2-deficient cells. Transactivation studies and chromatin immunoprecipitation implicate Lims1 as a direct target of NF-E2 regulation. Attribution of stagespecific genes, in combination with various applications, thus constitutes a powerful way to study MK differentiation and platelet biogenesis Experiment Overall Design: MK progenitors expand in mouse bone marrow or fetal liver cell preparations cultured with thrombopoietin, and mature over 5-6 days in vitro. After 3 days of culture, a significant fraction of cells shows features of committed MK progenitors, and numerous terminally mature, proplatelet-forming MKs appear by day 5. Because isolation of cell populations that correspond to sequential stages in MK differentiation is hindered by the lack of synchrony in primary MK cultures, we applied flow cytometry to harvest sub-populations that are substantially enriched for MKs with defined properties. High surface expression of the lineage marker CD41 identified MKs, whereas forward-scatter (FSC) properties distinguished cells on the basis of size. We collected thrombopoietic culture suspensions from days 3, 4 and 6, and sorted populations by flow cytometry. RNAs were prepared from sorted cells to probe Affymetrix MOE430A mouse oligonucleotide arrays.
Project description:Ex vivo production of induced megakaryocytes (MKs) and platelets from stem cells is an alternative approach for supplying transfusible platelets. However, it is still difficult to generate large numbers of MKs and platelets from cord blood hematopoietic stem cells. To optimize the differentiation efficiency of megakaryocytic cells from hematopoietic stem and progenitor cells (HSPCs), we first employed a platelet factor 4 (PF4)-promoter reporter and high-throughput screening strategy to screen for small molecules. We found that a small molecule, Ricolinostat, efficiently promoted the generation of CD34+CD41+ megakaryocyte progenitor cells (MkPs) and CD41+CD61+ MKs from cord blood HSPCs. Ricolinostat showed the capacity to enhance the cell fate commitment of MkPs from HSPCs and promoted the proliferation of CD34+CD41+ MkPs. Ricolinostat significantly increased the gene expression levels of key MK transcriptional factors, including HOXC6 and PCGF2. Notably, these megakaryocytic cells generated from Ricolinostat-induced HSPCs could differentiate into mature MKs and platelets. Additionally, RNA sequencing data suggested that Ricolinostat might enhance MkP fate mainly by inhibiting the secretion of IL-8 and decreasing the expression of IL-8 receptor CXCR2. Our study will help in the development of manufacturing protocols for large-scale generation of induced MKs and platelets for clinical application.
Project description:Platelets are anucleated blood cells that are produced by their progenitor cell, the megakaryocyte (MK). Platelets are centrally positioned in hemostasis and thrombosis and, according to the recent findings, play key roles in innate immunity, inflammation, atherogenesis, and cancer metastasis. The quantitative and qualitative properties of platelets are crucial determinants of their hemostatic function. While the regulatory mechanisms of platelet number and size have been studied separately, critical questions remain regarding the interplay of platelet number and size in hemostasis. In this study, using a mouse model of irradiation (IR)-induced thrombocytopenia, we show that mature MKs (mMKs) are resistant to IR and maintain the nadir platelet levels post IR. To identify the phenotype switching and function variation in BM MKs post IR, we performed microarray expression profiling of MKs from the bone marrow of mice at 1- or 3-days post IR and control mice (Ctrl).
Project description:d9 and d12 Mks were either cultured statically or subjected to shear flow for 30 min; at d9, half the Mks were placed back in culture for 30 min (60 min time point) Megakaryocytes (Mks) are exposed to shear flow as they migrate from the bone marrow hematopoietic compartment into circulation thus releasing platelets and pro/preplatelets directly into the blood stream. Shear forces have been now established as promoting Mk maturation and platelet biogenesis. In order to understand the underlying mechanisms that modulate the response of Mks to shear forces, we carried out transcriptional analysis on immature and mature stem cell-derived Mks that were exposed to physiologically-relevant shear (2.5 dyn/cm2). In immature (d9) Mks, shear exposure upregulated genes related to growth and Mk maturation, while in mature (d12) Mks, it upregulated genes involved in apoptosis and intracellular transport. Following shear-flow exposure, 6 AP-1 transcripts (ATF4, JUNB, JUN, FOSB, FOS, and JUND) were upregulated at d9 and two AP-1 proteins (JunD and c-Fos) were upregulated both at d9 and d12. Our data show that MAPK signaling is linked to both the shear-stress response and AP-1 upregulation. JNK phosphorylation increased significantly following shear stimulation, while JNK inhibition reduced shear-induced JunD protein expression. Although p38 phosphorylation did not increase following shear flow, its inhibition reduced shear-induced JunD and c-Fos protein expression. JNK inhibition reduced fibrinogen binding of d9 and d12 platelet-like particle s (PLPs) and P-selectin expression at d12 PLPs, while p38 inhibition reduced fibrinogen binding of d12 PLPs. Here we show that mechanotransduction of shear forces in Mks results in JNK activation, AP-1 upregulation, and downstream transcriptional changes that promote maturation of immature Mks and platelet biogenesis in mature Mks. Two- and Three-condition experiment (flow vs. static culture condition, d9 vs. d12, and 30 min vs. 60 min at d9); Biological replicates: 3; Technical replicates: 1 (dye-swap)
Project description:Despite our growing understanding of embryonic immune development, rare early megakaryocytes (MKs) remain relatively understudied. Here we used single-cell RNA sequencing of human MKs from embryonic yolk sac (YS) and fetal liver (FL) to characterize the transcriptome, cellular heterogeneity, and developmental trajectories of early megakaryopoiesis. In the YS and FL, we found heterogeneous MK subpopulations with distinct developmental routes and patterns of gene expression that could reflect early functional specialization. Intriguingly, we identified a subpopulation of CD42b+CD14+ MKs in vivo that exhibit high expression of genes associated with immune responses and can also be derived from human embryonic stem cells (hESCs) in vitro. Furthermore, we identified THBS1 as an early marker for MK-biased embryonic endothelial cells. Overall, we provide important insights and invaluable resources for dissection of the molecular and cellular programs underlying early human megakaryopoiesis.
Project description:Megakaryocyte (MK) differentiation is well described in morphologic terms but its molecular counterparts and the basis for platelet release are incompletely understood. We profiled mRNA expression in populations of primary mouse MKs representing successive differentiation stages. Genes associated with DNA replication are highly expressed in young MKs, in parallel with endomitosis. Intermediate stages are characterized by disproportionate expression of genes associated with the cytoskeleton, cell migration and G-protein signaling, whereas terminally mature MKs accumulate hemostatic factors, including many membrane proteins. We used these expression profiles to extract a reliable panel of molecular markers for MKs of early, intermediate or advanced differentiation, and establish its value using mouse models of defective thrombopoiesis resulting from absence of GATA-1, NF-E2 or tubulinß1. Computational analysis of the promoters of late-expressed MK genes identified new candidate targets for NF-E2, a critical transcriptional regulator of platelet release. One such gene encodes the kinase adaptor protein LIMS1/PINCH1, which is highly expressed in MKs and platelets and significantly reduced in NF-E2-deficient cells. Transactivation studies and chromatin immunoprecipitation implicate Lims1 as a direct target of NF-E2 regulation. Attribution of stagespecific genes, in combination with various applications, thus constitutes a powerful way to study MK differentiation and platelet biogenesis Keywords: expression profiling differentiation megakaryocyte
Project description:The role of ABCC4, an ATP-binding cassette transporter, in the process of platelet formation, megakaryopoiesis, is unknown. Here, we show that ABCC4 is highly expressed in megakaryocytes (MKs). Mining of public genomic data (ATAC-seq and genome wide chromatin interactions, Hi-C) revealed that key megakaryopoiesis transcription factors (TFs) interacted with ABCC4 regulatory elements and likely accounted for high ABCC4 expression in MKs. Importantly these genomic interactions for ABCC4 ranked higher than for genes with known roles in megakaryopoiesis suggesting a role for ABCC4 in megakaryopoiesis. We then demonstrate that ABCC4 is required for optimal platelet formation as in vitro differentiation of fetal liver derived MKs from Abcc4-/- mice exhibited impaired proplatelet formation and polyploidization, features required for optimal megakaryopoiesis. Likewise, a human megakaryoblastic cell line, MEG-01 showed that acute ABCC4 inhibition markedly suppressed key processes in megakaryopoiesis and that these effects were related to reduced cAMP export and enhanced dissociation of a negative regulator of megakaryopoiesis, protein kinase A (PKA) from ABCC4. PKA activity concomitantly increased after ABCC4 inhibition which was coupled with significantly reduced GATA-1 expression, a TF needed for optimal megakaryopoiesis. Further, ABCC4 protected MKs from 6-mercaptopurine (6-MP) as Abcc4-/- mice show a profound reduction in MKs after 6-MP treatment. In total, our studies show that ABCC4 not only protects the MKs but is also required for maximal platelet production from MKs, suggesting modulation of ABCC4 function might be a potential therapeutic strategy to regulate platelet production.
Project description:The role of ABCC4, an ATP-binding cassette transporter, in the process of platelet formation, megakaryopoiesis, is unknown. Here, we show that ABCC4 is highly expressed in megakaryocytes (MKs). Mining of public genomic data (ATAC-seq and genome wide chromatin interactions, Hi-C) revealed that key megakaryopoiesis transcription factors (TFs) interacted with ABCC4 regulatory elements and likely accounted for high ABCC4 expression in MKs. Importantly these genomic interactions for ABCC4 ranked higher than for genes with known roles in megakaryopoiesis suggesting a role for ABCC4 in megakaryopoiesis. We then demonstrate that ABCC4 is required for optimal platelet formation as in vitro differentiation of fetal liver derived MKs from Abcc4-/- mice exhibited impaired proplatelet formation and polyploidization, features required for optimal megakaryopoiesis. Likewise, a human megakaryoblastic cell line, MEG-01 showed that acute ABCC4 inhibition markedly suppressed key processes in megakaryopoiesis and that these effects were related to reduced cAMP export and enhanced dissociation of a negative regulator of megakaryopoiesis, protein kinase A (PKA) from ABCC4. PKA activity concomitantly increased after ABCC4 inhibition which was coupled with significantly reduced GATA-1 expression, a TF needed for optimal megakaryopoiesis. Further, ABCC4 protected MKs from 6-mercaptopurine (6-MP) as Abcc4-/- mice show a profound reduction in MKs after 6-MP treatment. In total, our studies show that ABCC4 not only protects the MKs but is also required for maximal platelet production from MKs, suggesting modulation of ABCC4 function might be a potential therapeutic strategy to regulate platelet production.