Culture of megakaryocytes and platelets from subcutaneous adipose tissue and a preadipocyte cell line

The localization, origin, and impact of platelets in the tumor microenvironment are tumor type-dependent

BACKGROUND

How platelets interact with and influence the tumor microenvironment (TME) remains poorly characterized.

METHODS

We compared the presence and participation of platelets in the TME of two tumors characterized by highly different TME, PyMT AT-3 mammary tumors and B16F1 melanoma.

RESULTS

We show that whereas firmly adherent platelets continuously line tumor vessels of both AT-3 and B16F1 tumors, abundant extravascular stromal clusters of platelets from thrombopoietin-independent origin were present only in AT-3 mammary tumors. We further show that platelets influence the angiogenic and inflammatory profiles of AT-3 and B16F1 tumors, though with very different outcomes according to tumor type. Whereas thrombocytopenia increased bleeding in both tumor types, it further caused severe endothelial degeneration associated with massive vascular leakage, tumor swelling, and increased infiltration of cytotoxic cells, only in AT-3 tumors.

CONCLUSIONS

These results indicate that while platelets are integral components of solid tumors, their localization and origin in the TME, as well as their impact on its shaping, are tumor type-dependent.

Integrative transcriptomic, evolutionary, and causal inference framework for region-level analysis: Application to COVID-19

We developed an integrative transcriptomic, evolutionary, and causal inference framework for a deep region-level analysis, which integrates several published approaches and a new summary-statistics-based methodology. To illustrate the framework, we applied it to understanding the host genetics of COVID-19 severity. We identified putative causal genes, including SLC6A20, CXCR6, CCR9, and CCR5 in the locus on 3p21.31, quantifying their effect on mediating expression and on severe COVID-19. We confirmed that individuals who carry the introgressed archaic segment in the locus have a substantially higher risk of developing the severe disease phenotype, estimating its contribution to expression-mediated heritability using a new summary-statistics-based approach we developed here. Through a large-scale phenome-wide scan for the genes in the locus, several potential complications, including inflammatory, immunity, olfactory, and gustatory traits, were identified. Notably, the introgressed segment showed a much higher concentration of expression-mediated causal effect on severity (0.9–11.5 times) than the entire locus, explaining, on average, 15.7% of the causal effect. The region-level framework (implemented in publicly available software, SEGMENT-SCAN) has important implications for the elucidation of molecular mechanisms of disease and the rational design of potentially novel therapeutics.

Generation of HLA Universal Megakaryocytes and Platelets by Genetic Engineering

Patelet transfusion refractoriness remains a relevant hurdle in the treatment of severe alloimmunized thrombocytopenic patients. Antibodies specific for the human leukocyte antigens (HLA) class I are considered the major immunological cause for PLT transfusion refractoriness. Due to the insufficient availability of HLA-matched PLTs, the development of new technologies is highly desirable to provide an adequate management of thrombocytopenia in immunized patients. Blood pharming is a promising strategy not only to generate an alternative to donor blood products, but it may offer the possibility to optimize the therapeutic effect of the produced blood cells by genetic modification. Recently, enormous technical advances in the field of in vitro production of megakaryocytes (MKs) and PLTs have been achieved by combining progresses made at different levels including identification of suitable cell sources, cell pharming technologies, bioreactors and application of genetic engineering tools. In particular, use of RNA interference, TALEN and CRISPR/Cas9 nucleases or nickases has allowed for the generation of HLA universal PLTs with the potential to survive under refractoriness conditions. Genetically engineered HLA-silenced MKs and PLTs were shown to be functional and to have the capability to survive cell- and antibody-mediated cytotoxicity using in vitro and in vivo models. This review is focused on the methods to generate in vitro genetically engineered MKs and PLTs with the capacity to evade allogeneic immune responses.

Platelet production using adipose-derived mesenchymal stem cells: Mechanistic studies and clinical application

Megakaryocytes (MKs) are platelet progenitor stem cells found in the bone marrow. Platelets obtained from blood draws can be used for therapeutic applications, especially platelet transfusion. The needs for platelet transfusions for clinical situation is increasing, due in part to the growing number of patients undergoing chemotherapy. Platelets obtained from donors, however, have the disadvantages of a limited storage lifespan and the risk of donor-related infection. Extensive effort has therefore been directed at manufacturing platelets ex vivo. Here, we review ex vivo technologies for MK development, focusing on human adipose tissue-derived mesenchymal stem/stromal cell line (ASCL)-based strategies and their potential clinical application. Bone marrow and adipose tissues contain mesenchymal stem/stromal cells that have an ability to differentiate into MKs, which release platelets. Taking advantage of this mechanism, we developed a donor-independent system for manufacturing platelets for clinical application using ASCL established from adipose-derived mesenchymal stem/stromal cells (ASCs). Culture of ASCs with endogenous thrombopoietin and its receptor c-MPL, and endogenous genes such as p45NF-E2 leads to MK differentiation and subsequent platelet production. ASCs compose heterogeneous cells, however, and are not suitable for clinical application. Thus, we established ASCLs, which expand into a more homogeneous population, and fulfill the criteria for mesenchymal stem cells set by the International Society for Cellular Therapy. Using our ASCL culture system with MK lineage induction medium without recombinant thrombopoietin led to peak production of platelets within 12 days, which may be sufficient for clinical application.

Thromboxane-Dependent Platelet Activation in Obese Subjects with Prediabetes or Early Type 2 Diabetes: Effects of Liraglutide- or Lifestyle Changes-Induced Weight Loss

Thromboxane (TX)-dependent platelet activation and lipid peroxidation, as reflected in vivo by the urinary excretion of 11-dehydro-TXB₂ and 8-iso-prostaglandin (PG)F_2α, play a key role in atherothrombosis in obesity and type 2 diabetes mellitus (T2DM) since the earlier stages. Thirty-five metformin-treated obese subjects with prediabetes or newly-diagnosed T2DM were randomized to the glucagon-like peptide receptor agonist (GLP-RA) liraglutide (1.8 mg/day) or lifestyle counseling until achieving a comparable weight loss (−7% of initial body weight), to assess whether changes in subcutaneous (SAT) and visceral (VAT) adipose tissue distribution (MRI), insulin sensitivity (Matsuda Index) and beta-cell performance (multiple sampling OGTT beta-index), with either intervention, might affect TX-dependent platelet activation, lipid peroxidation and inflammation. At baseline, Ln-8-iso-PGF_2α (Beta = 0.31, p = 0.0088), glycosylated hemoglobin (HbA1c) (Beta = 2.64, p = 0.0011) Ln-TNF-α (Beta = 0.58, p = 0.0075) and SAT (Beta = 0.14, p = 0.044) were significant independent predictors of 11-dehydro-TXB₂. After achievement of the weight loss target, a comparable reduction in U-11-dehydro-TXB₂ (between-group p = 0.679) and 8-iso-PGF-_2α (p = 0.985) was observed in both arms in parallel with a comparable improvement in glycemic control, insulin sensitivity, SAT, high-sensitivity C-reactive protein (hs-CRP). In obese patients with initial impairment of glucose metabolism, the extent of platelet activation is related to systemic inflammation, isoprostane formation and degree of glycemic control and abdominal SAT. Successful weight loss, achieved with either lifestyle changes or an incretin-based therapy, is associated with a significant reduction in lipid peroxidation and platelet activation.

Megakaryocytes and platelets from a novel human adipose tissue-derived mesenchymal stem cell line

The clinical need for platelet transfusions is increasing; however, donor-dependent platelet transfusions are associated with practical problems, such as the limited supply and the risk of infection. Thus, we developed a manufacturing system for platelets from a donor-independent cell source: a human adipose-derived mesenchymal stromal/stem cell line (ASCL). The ASCL was obtained using an upside-down culture flask method and satisfied the minimal criteria for defining mesenchymal stem cells (MSCs) by The International Society for Cellular Therapy. The ASCL showed its proliferation capacity for ≥2 months without any abnormal karyotypes. The ASCL was cultured in megakaryocyte induction media. ASCL-derived megakaryocytes were obtained, with a peak at day 8 of culture, and ASCL-derived platelets (ASCL-PLTs) were obtained, with a peak at day 12 of culture. We observed that CD42b⁺ cells expressed an MSC marker (CD90) which is related to cell adhesion. Compared with peripheral platelets, ASCL-PLTs exhibit higher levels of PAC1 binding, P-selectin surface exposure, ristocetin-induced platelet aggregation, and ADP-induced platelet aggregation, as well as similar levels of fibrinogen binding and collagen-induced platelet aggregation. ASCL-PLTs have lower epinephrine-induced platelet aggregation. The pattern of in vivo kinetics after infusion into irradiated immunodeficient NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ mice was similar to that of platelet concentrates. ASCL-PLTs have similar characteristics to those of peripheral platelets and might have an additional function as MSCs. The establishment of the ASCL and its differentiation into ASCL-PLTs do not require gene transfer, and endogenous thrombopoietin is used for differentiation. The present protocol is a simple method that does not require feeder cells, further enhancing the clinical application of our approach.

Platelet production from induced pluripotent stem cells

Ex vivo production of human platelets has been pursued as an alternative measure to resolve limitations in the supply and safety of current platelet transfusion products. To this end, induced pluripotent stem cells (iPSCs) are considered an ideal global source, as they are not only pluripotent and self-renewing, but are also available from basically any person, have relatively few ethical issues, and are easy to manipulate. From human iPSCs, megakaryocyte (MK) lines with robust proliferation capacity have been established by the introduction of specified sets of genes. These expandable MKs are also cryopreservable and thus would be suitable as master cells for good manufacturing practice (GMP)-grade production of platelets, assuring availability on demand and safety against blood-borne infections. Meanwhile, developments in bioreactors that physically mimic the in vivo environment and discovery of substances that promote thrombopoiesis have yielded competent platelets with improved efficiency. The derivation of platelets from iPSCs could further resolve transfusion-related alloimmune complications through the manufacturing of autologous products and human leukocyte antigen (HLA)-compatible platelets from stocked homologous HLA-type iPSC libraries or by manipulation of HLAs and human platelet antigens (HPAs). Considering these key advances in the field, HLA-deleted platelets could become a universal product that is manufactured at industrial level to safely fulfill almost all demands. In this review, we provide an overview of the ex vivo production of iPSC-derived platelets toward clinical applications, a production that would revolutionize the blood transfusion system and lead the field of iPSC-based regenerative medicine.

Platelet generation in vivo and in vitro

Platelet (PLT) transfusion, which is the primary cell therapy for thrombocytopenia, has been a source of concern in recent years due to its limitations of donor-dependent supply and soaring costs. In vitro platelet generation on an industrial scale is a possible solution requiring exploration. The technology of platelet generation ex vivo has been widely studied across the world, though the mechanisms of physiological thrombopoiesis and platelet biology function in vivo still remain elusive today. Various culture systems have been studied, most of which proved quite inefficient in generating functional platelets ex vivo, so there is still a long way to reach our ultimate goal of generating a fully functional platelet in vitro on an industrial scale. This review integrates the latest research into physiological platelet biogenesis and ex vivo-platelet/megakaryocyte (MK) generation protocols with a focus on the ability to generate PLT/MK in large quantities, summarizes current culture systems based on induced human pluripotent stem cells and adipose-derived stem cells, and discusses significant challenges that must be overcome for these approaches to be perfected.

Human adipose tissue-derived stromal cells can differentiate into megakaryocytes and platelets by secreting endogenous thrombopoietin

Essentials Manufacturing platelets from a donor-independent source is highlighted in transfusion medicine. We examined the differentiation of adipose tissue-derived stromal cells (ASCs) into platelets. Endogenous thrombopoietin (TPO) induced ASCs differentiation into megakaryocytes and platelets. TPO secretion from ASCs was due to an interaction of transferrin with its receptor CD71.

SUMMARY

Background Ex vivo production of megakaryocytes (MKs) and platelets from a donor-independent source is currently of intense interest in transfusion medicine. Adipose tissue-derived stromal cells (ASCs) constitute an attractive candidate cell source, because inducing these cells into MK lineages requires no gene transfer and only endogenous transcription factors containing p45NF-E2/Maf, an MK-inducing factor. Objectives To examine whether ASCs differentiate into MK lineages by using endogenous thrombopoietin (TPO), a primary cytokine that drives MK lineages. Methods TPO levels were measured by quantitative real-time PCR and ELISA. To investigate the effects of endogenous TPO on MK and platelet production, surface marker expression and functions for platelets were analyzed in ASC-derived cells cultured in the presence or absence of recombinant TPO. Based on a screening test, the role of transferrin receptor CD71 in TPO production and MK differentiation was examined with anti-CD71 antibody, small interfering RNA (siRNA) against CD71 (siRNA-CD71), and CD71-positive/negative cells. Results ASCs secreted TPO during MK differentiation, and the endogenous TPO facilitated MK and platelet production from ASCs. TPO secretion from ASCs occurred in a transferrin-dependent manner. ASCs treated with anti-CD71 antibody or transfected with siRNA-CD71 produced markedly less TPO. The TPO levels and MK yield were significantly higher when CD71-positive ASCs were used than when CD71-negative ASCs were used. Conclusions CD71 might be an appropriate marker for MK progenitor cells among human ASCs, because of the higher capacity of CD71-positive cells to produce TPO and their ability to differentiate into MKs. These findings could help to establish an efficient method for platelet production.

OP9 bone marrow stroma cells differentiate into megakaryocytes and platelets

Platelets are essential for hemostatic plug formation and thrombosis. The mechanisms of megakaryocyte (MK) differentiation and subsequent platelet production from stem cells remain only partially understood. The manufacture of megakaryocytes (MKs) and platelets from cell sources including hematopoietic stem cells and pluripotent stem cells have been highlighted for studying the platelet production mechanisms as well as for the development of new strategies for platelet transfusion. The mouse bone marrow stroma cell line OP9 has been widely used as feeder cells for the differentiation of stem cells into MK lineages. OP9 cells are reported to be pre-adipocytes. We previously reported that 3T3-L1 pre-adipocytes differentiated into MKs and platelets. In the present study, we examined whether OP9 cells differentiate into MKs and platelets using MK lineage induction (MKLI) medium previously established to generate MKs and platelets from hematopoietic stem cells, embryonic stem cells, and pre-adipocytes. OP9 cells cultured in MKLI medium had megakaryocytic features, i.e., positivity for surface markers CD41 and CD42b, polyploidy, and distinct morphology. The OP9-derived platelets had functional characteristics, providing the first evidence for the differentiation of OP9 cells into MKs and platelets. We then analyzed gene expressions of critical factors that regulate megakaryopoiesis and thrombopoiesis. The gene expressions of p45NF-E2, FOG, Fli1, GATA2, RUNX1, thrombopoietin, and c-mpl were observed during the MK differentiation. Among the observed transcription factors of MK lineages, p45NF-E2 expression was increased during differentiation. We further studied MK and platelet generation using p45NF-E2-overexpressing OP9 cells. OP9 cells transfected with p45NF-E2 had enhanced production of MKs and platelets. Our findings revealed that OP9 cells differentiated into MKs and platelets in vitro. OP9 cells have critical factors for megakaryopoiesis and thrombopoiesis, which might be involved in a mechanism of this differentiation. p45NF-E2 might also play important roles in the differentiation of OP9 cells into MK lineages cells.

Challenges and promises for the development of donor-independent platelet transfusions

Platelet transfusions are often a life-saving intervention, and the use of platelet transfusions has been increasing. Donor-derived platelet availability can be challenging. Compounding this concern are additional limitations of donor-derived platelets, including variability in product unit quality and quantity, limited shelf life and the risks of product bacterial contamination, other transfusion-transmitted infections, and immunologic reactions. Because of these issues, there has been an effort to develop strategies to generate platelets from exogenously generated precursor cells. If successful, such platelets have the potential to be a safer, more consistent platelet product, while reducing the necessity for human donations. Moreover, ex vivo-generated autologous platelets or precursors may be beneficial for patients who are refractory to allogeneic platelets. For patients with inherited platelet disorders, ex vivo-generated platelets offer the promise of a treatment via the generation of autologous gene-corrected platelets. Theoretically, ex vivo-generated platelets also offer targeted delivery of ectopic proteins to sites of vascular injury. This review summarizes the current, state-of-the-art methodologies in delivering a clinically relevant ex vivo-derived platelet product, and it discusses significant challenges that must be overcome for this approach to become a clinical reality.

Induction of functional platelets from mouse and human fibroblasts by p45NF-E2/Maf

Determinant factors leading from stem cells to megakaryocytes (MKs) and subsequently platelets have yet to be identified. We now report that a combination of nuclear factor erythroid-derived 2 p45 unit (p45NF-E2), Maf G, and Maf K can convert mouse fibroblast 3T3 cells and adult human dermal fibroblasts into MKs. To screen MK-inducing factors, gene expressions were compared between 3T3 cells that do not differentiate into MKs and 3T3-L1 cells known to differentiate into MKs. 3T3 cells transfected with candidate factors were cultured in a defined MK lineage induction medium. Among the tested factors, transfection with p45NF-E2/MafG/MafK lead to the highest frequency of CD41-positive cells. Adult human dermal fibroblasts transfected with these genes were cultured in MK lineage induction medium. Cultured cells had megakaryocytic features, including surface markers, ploidy, and morphology. More than 90% of MK-sized cells expressed CD41, designated induced MK (iMK). Infusion of these iMK cells into immunodeficient mice led to a time-dependent appearance of CD41-positive, platelet-sized particles. Blood samples from iMK-infused into thrombocytopenic immunodeficient mice were perfused on a collagen-coated chip, and human CD41-positive platelets were incorporated into thrombi on the chip, demonstrating their functionality. These findings demonstrate that a combination of p45NF-E2, Maf G, and Maf K is a key determinant of both megakaryopoiesis and thrombopoiesis.