Cell-derived Platelets Research Articles

Generation of Functioning Platelets from Mature Megakaryocytes Derived from CD34+ Umbilical Cord Blood Cells.

Clinically patients with thrombocytopenia are in urgent need of platelet transfusion, thus it is necessary to produce the platelets in large scale in vitro to meet the clinical needs. In this study, we developed efficient protocol to generate functioning platelets by differentiating umbilical cord blood (CB)-derived CD34+ cells into mature megakaryocytes. Under our condition, up to 85% of mature megakaryocytes were generated from CB-derived CD34+ cells, and over 75% CD42b+CD62p+ platelets were produced. The megakaryocytes at day 12 after the differentiation had the similar gene expression pattern to natural mature megakaryocytes, and AMPK and insulin signal pathway were activated to inhibit the apoptosis and benefit platelet release. There were up to 72% of the platelets that could bind with PAC1, which is the highest rate of CB CD34+ cell-derived platelets to play function in vitro to date. The recovery of hemostasis and coagulation was similar in thrombocytopenia mice injected with CB CD34+ cell-derived platelets and with human blood-derived platelets, respectively, and it is the first time to demonstrate that human CB CD34+ cell-derived platelets were functional invivo. Therefore, our findings open a new avenue to provide an in vitro efficient approach to generate functional platelets for clinical applications.

Autophagy-enabled protein degradation: Key to platelet activation and ANGII production in patients with type 2 diabetes mellitus

BackgroundType 2 diabetes mellitus (T2DM) presents a thrombotic environment, contributing to diabetic macroangiopathy and microangiopathy. In this study, the regulation of microthrombosis in T2DM was assessed. MethodsPlatelets from T2DM patients and healthy controls were analyzed using 4D label-free proteomics and bioinformatics. The role of autophagy in T2DM platelet activation and conversion of platelet-derived angiotensinogen (AGT) was investigated. ResultsThe results showed that complement and coagulation cascades, platelet activation, metabolic pathways, endocytosis, autophagy, and other protein digestion-related pathways were enriched. The levels of the key protein AGT were increased in T2DM platelets. Chloroquine (CQ) inhibited ADP- or arachidonic acid (AA)-stimulated platelet aggregation and granule release in a dose-dependent manner, while the effects were less pronounced or even reversed for the proteasome inhibitor PYR-41 and the endocytosis inhibitor Pitstop 2. This indicated the dependence of platelet activation and the accompanying protein digestion on the autophagy-lysosome pathway. Mitophagy occurred in fresh T2DM platelets and ADP- or storage-stimulated platelets; mitophagy was inhibited by CQ. However, the mitophagy inhibitor Mdivi-1 failed to show effects similar to those of CQ. AGT, which could be transformed into ANGII in vitro by ADP-stimulated platelets, was upregulated in T2DM platelets and in MEG-01 cell-derived platelets cultured in a high-glucose medium. Finally, microthrombosis was alleviated as indicated by a reduction in the levels of red blood cells in the liver, spleen, heart, and kidney tissues of db/db mice treated with CQ or valsartan. ConclusionIn platelets, macroautophagy promotes protein digestion, subsequently facilitating platelet activation, ANGII-mediated vasoconstriction, and microthrombosis. Our results suggested that lysosome is a promising therapeutic target for antithrombotic treatment in T2DM.

Osteogenic effects and safety of human induced pluripotent stem cell-derived megakaryocytes and platelets produced on a clinical scale

IntroductionPlatelet-rich plasma obtained by centrifuging peripheral blood can promote osteogenesis owing to its abundant growth factors but has drawbacks, including rapid growth factor loss and inconsistent effects depending on donor factors. To overcome these issues, we were the first in the world to use freeze-dried human induced pluripotent stem cell-derived megakaryocytes and platelets (S-FD-iMPs) and found that they have osteogenesis-promoting effects. Since turbulence was found to activate platelet biogenesis and iPS cell-derived platelets can now be produced on a clinical scale by a device called VerMES, this study examined the osteogenesis-promoting effect and safety of clinical-scale FD-iMP (V-FD-iMPs) for future human clinical application. MethodWe administered either S-FD-iMPs, V-FD-iMPs, or saline along with artificial bone to the lumbar spine of 8-week-old male Sprague–Dawley rats (n = 4 each) and evaluated bone formation by computed tomography (CT) and pathology. Next, we administered V-FD-iMPs or saline along with artificial bone to the lumber spines of 5-week-old male New Zealand White rabbits (n = 4 each) and evaluated the bone formation by CT and pathology. Rats (n = 10) and rabbits (n = 6) that received artificial bone and V-FD-iMPs in the lumbar spine were also observed for 6 months for adverse events, including infection, tumor formation, and death. ResultsBoth V-FD-iMPs and S-FD-iMPs significantly enhanced osteogenesis in the lumber spines of rats in comparison with the controls 8 weeks postoperatively, with no significant differences between them. Furthermore, V-FD-iMPs vigorously promoted osteogenesis in the lumber spines of rabbits 8 weeks postoperatively. In rats and rabbits, V-FD-iMPs showed no adverse effects, including infection, tumor formation, and death, over 6 months. ConclusionThese results suggest that V-FD-iMPs promote safe osteogenesis.

A let-7 microRNA-RALB axis links the immune properties of iPSC-derived megakaryocytes with platelet producibility

We recently achieved the first-in-human transfusion of induced pluripotent stem cell-derived platelets (iPSC-PLTs) as an alternative to standard transfusions, which are dependent on donors and therefore variable in supply. However, heterogeneity characterized by thrombopoiesis-biased or immune-biased megakaryocytes (MKs) continues to pose a bottleneck against the standardization of iPSC-PLT manufacturing. To address this problem, here we employ microRNA (miRNA) switch biotechnology to distinguish subpopulations of imMKCLs, the MK cell lines producing iPSC-PLTs. Upon miRNA switch-based screening, we find imMKCLs with lower let-7 activity exhibit an immune-skewed transcriptional signature. Notably, the low activity of let-7a-5p results in the upregulation of RAS like proto-oncogene B (RALB) expression, which is crucial for the lineage determination of immune-biased imMKCL subpopulations and leads to the activation of interferon-dependent signaling. The dysregulation of immune properties/subpopulations, along with the secretion of inflammatory cytokines, contributes to a decline in the quality of the whole imMKCL population.

Retraction Note: Human induced pluripotent stem cell-derived platelets loaded with lapatinib effectively target HER2+ breast cancer metastasis to the brain

Retraction Note: Human induced pluripotent stem cell-derived platelets loaded with lapatinib effectively target HER2+ breast cancer metastasis to the brain

Current status of platelet manufacturing in 3D or bioreactors.

Blood shortages for transfusion are global issues of grave concern. As in vitro manufactured platelets are promising substitutes for blood donation, recent research has shown progresses including different cell sources, different bioreactors, and three-dimensional materials. The first-in-human clinical trial of cultured platelets using induced pluripotent stem cell-derived platelets began in Japan and demonstrated its quality, safety, and efficacy. A novel bioreactor with fluid motion for platelet production has been reported. Herein, we discuss various cell sources for blood cell production, recent advances in manufacturing processes, and clinical applications of cultured blood.

RETRACTED ARTICLE: Human induced pluripotent stem cell-derived platelets loaded with lapatinib effectively target HER2+ breast cancer metastasis to the brain

Prognosis of patients with HER2+ breast-to-brain-metastasis (BBM) is dismal even after current standard-of-care treatments, including surgical resection, whole-brain radiation, and systemic chemotherapy. Radiation and systemic chemotherapies can also induce cytotoxicity, leading to significant side effects. Studies indicate that donor-derived platelets can serve as immune-compatible drug carriers that interact with and deliver drugs to cancer cells with fewer side effects, making them a promising therapeutic option with enhanced antitumor activity. Moreover, human induced pluripotent stem cells (hiPSCs) provide a potentially renewable source of clinical-grade transfusable platelets that can be drug-loaded to complement the supply of donor-derived platelets. Here, we describe methods for ex vivo generation of megakaryocytes (MKs) and functional platelets from hiPSCs (hiPSC-platelets) in a scalable fashion. We then loaded hiPSC-platelets with lapatinib and infused them into BBM tumor-bearing NOD/SCID mouse models. Such treatment significantly increased intracellular lapatinib accumulation in BBMs in vivo, potentially via tumor cell-induced activation/aggregation. Lapatinib-loaded hiPSC-platelets exhibited normal morphology and function and released lapatinib pH-dependently. Importantly, lapatinib delivery to BBM cells via hiPSC-platelets inhibited tumor growth and prolonged survival of tumor-bearing mice. Overall, use of lapatinib-loaded hiPSC-platelets effectively reduced adverse effects of free lapatinib and enhanced its therapeutic efficacy, suggesting that they represent a novel means to deliver chemotherapeutic drugs as treatment for BBM.

In vitro Generation of Megakaryocytes and Platelets.

Platelets, the tiny anucleate cells responsible for stopping bleeding through thrombosis, are derived from hematopoietic stem cells through a series of differentiation steps. Thrombocytopenia, characterized by abnormally low blood platelet counts, may arise from cancer therapies, trauma, sepsis, as well as blood disorders, and could become a life-threatening problem. Platelet transfusion is the most effective strategy to treat thrombocytopenia, however, the source of platelets is in great shortage. Therefore, in vitro generation of platelets has become an important topic and numerous attempts have been made toward generating platelets from different types of cells, including hematopoietic stem cells, pluripotent stem cells, fibroblast cells, and adipose-derived cells. In this review, we will detail the efforts made to produce, in the in vitro culture, platelets from these different cell types. Importantly, as transfusion medicine requires a huge number of platelets, we will highlight some studies on producing platelets on a large scale. Although new methods of gene manipulation, new culture conditions, new cytokines and chemical compounds have been introduced in platelet generation research since the first study of hematopoietic stem cell-derived platelets nearly 30 years ago, limited success has been achieved in obtaining truly mature and functional platelets in vitro, indicating the studies of platelets fall behind those of other blood cell types. This is possibly because megakaryocytes, which produce platelets, are very rare in blood and marrow. We have previously developed a platform to identify new extrinsic and intronic regulators for megakaryocytic lineage development, and in this review, we will also cover our effort on that. In summary, stem cell-based differentiation is a promising way of generating large-scale platelets to meet clinical needs, and continuous study of the cellular development of platelets will greatly facilitate this.

Ex vivo Engineering of Platelets

Platelet transfusion is necessary for patients in thrombocytopenic states. Due to short shelf life of platelet product, the shortage of blood donors in the younger population as the consequence of aging societies in developed countries and platelet transfusion refractoriness (PTR) caused by alloimmune response, the risk of platelet product shortage has been a concern. Therefore, many attempts to substitute donor-dependent platelet product have been proposed. Induced pluripotent stem cell (iPSC) derived-platelet like particle product (which we refer as iPS-platelets) is aimed to provide measures against alloimmune PTR as well as to complement the current blood donor-dependent system.To generate the huge number of platelets required for transfusion into thrombocytopenia patients (200-300 billion per transfusion) ex vivo, megakaryopoiesis and subsequent platelet biogenesis process from megakaryocytes needed to be both substantially elucidated in mechanical systems. For the former, our key measure is to expand the immortalized megakaryocyte cell lines (imMKCLs) derived from iPSCs, whereby c-MYC, BMI-1, and Bcl-XL are overexpressed under doxycycline-inducible system to regulate proliferation of megakaryocyte progenitors (Cell Stem Cell, 2014). For the latter, in vivovisualization of mouse bone marrow revealed the presence of turbulence adjacent to megakaryocytes actively releasing platelets, which prompted us to utilize a unique turbulent flow-incorporated bioreactor to produce iPS-platelets. Furthermore, we succeeded in identifying turbulent energy and shear stress as essential physical parameters and further determined the optimal values, thereby to enable efficient and intact ex vivoplatelet manufacture, as exemplified by lowered Annexin V binding values in iPS-platelets, comparable with donor-human platelets. Simultaneously, we developed a culture medium cocktail including a thrombopoietin (TPO) mimetic small compound, an ADAM10/17 inhibitor for the maintenance of GPIb-alpha expression on platelets, an arylhydrocarbon receptor inhibitor, and a ROCK inhibitor for feeder cell-independent megakaryocyte maturation (Stem Cells Transl Med, 2017; Blood Adv, 2017; Blood Adv, 2018). By scaling up of the bioreactor, 100 billion iPS-platelets were produced in 8 L scale. In vitro and in vivo evaluation of iPS-platelets showed the functionality comparable with blood donor-derived platelets (Cell, 2018), including the newly developed thrombocytopenia rabbit model (Transfusion, 2017). Meanwhile, an iPS cell-derived human leukocyte antigen (HLA) class-I-null imMKCL as a universal HLA platelet source is potentially the best solution for alloimmune PTR. However, the immunogenic properties are still unclear, especially regarding natural killer (NK) cells that attack HLA-downregulated cells. Therefore, we evaluated the immunological reaction between HLA-null platelets and NK cells by using our newly developed alloimmune PTR in vivo model in which human NK cells are highly reconstituted in MISTRG mice (Suzuki and Sugimoto et al.,manuscript in revision). This pre-clinical study model should provide a proof-of concept for the clinical application of HLA-null iPS-platelets as a universal platelet product for future transfusion. References Nakamura S, et al. Expandable Megakaryocyte Cell Lines Enable Clinically Applicable Generation of Platelets from Human Induced Pluripotent Stem Cells. Cell Stem Cell. 2014, 14, 535-548.Hirata S, et al. Selective Inhibition of ADAM17 Efficiently Mediates Glycoprotein IbαRetention During Ex Vivo Generation of Human Induced Pluripotent Stem Cell-Derived Platelets. Stem Cells Transl Med. 2017, 6, 720-730.Aihara A, et al. Novel TPO receptor agonist TA-316 contributes to platelet biogenesis from human iPS cells. Blood Adv. 2017, 1, 468-476.Seo H, Chen SJ, et al. A β1-tubulin-based megakaryocyte maturation reporter system identifies novel drugs that promote platelet production. Blood Adv. 2018, 2, 2262-2272.Ito Y, Nakamura S, et al. Turbulence Activates Platelet Biogenesis to Enable Clinical Scale Ex Vivo Production. Cell. 2018, 174, 636-648.Watanabe N, et al. Refined methods to evaluate the in vivo hemostatic function and viability of transfused human platelets in rabbit models. Transfusion. 2017, 57, 2035-2044. Disclosures Eto: Megakaryon Co. Ltd.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Our published results that include some drugs, i.e., TA-316 (Blood Advances, 1(7):468-476, 2017), KP457 (Stem Cells Transl Med, 6(3):720-730, 2017), and SR1 (Cell, 174(3):636-648, 2018)

VI. iPS Cell-derived Platelets

血小板は止血に不可欠な血球成分であり，重度の血小板減少症には輸血が行われてきた．iPS（induced pluripotent stem）細胞から製造される血小板は，社会の高齢化に伴う献血ドナー不足や輸血不応症等を解決するものと期待され，巨核球株の樹立や新規薬剤・バイオリアクターの開発によって臨床スケールでの製造が可能となり，臨床応用が始まりつつある．今後は，早期の普及によってiPS細胞応用医療を牽引し，輸血医療を大きく発展させることが期待される．

Reconstitution of the hematopoietic system and clinical applications of iPS cells

Human iPS cells are somatic cells reprogrammed to the pluripotent state. Because of their pluripotent nature, iPS cells are now commonly used to model several developmental processes including hematopoiesis in vitro. The in vitro models can be used to study the mechanisms regulating not only normal hematopoiesis but also hematological diseases ranging from monogenic congenital disorders to genetically multifactorial malignancies. Those disease models can also be used to investigate novel treatments through procedures including high throughput drug screening. The possible clinical applications of iPS cell-derived hematopoietic cells include immunotherapy with T lymphocytes, NK cells and macrophages, and transfusion therapy with platelets and red blood cells. Platelets have now been produced from iPS cells in quantities sufficient for clinical use. By developing expandable immortalized megakaryocyte cell lines (imMKCLs), several novel drugs and turbulence-incorporated bioreactors, efficient and scalable generation of platelets was achieved. This review summarizes the current status of iPS cell research in hematopoiesis with details on iPS cell-derived platelets.

1S-B1-2Backscattered-electron Imaging for Ultrastructural Evaluation of the Blood Platelet Profile: with a Provision of Human iPS Cell-derived Platelets Production for Clinical Transfusion

1S-B1-2Backscattered-electron Imaging for Ultrastructural Evaluation of the Blood Platelet Profile: with a Provision of Human iPS Cell-derived Platelets Production for Clinical Transfusion

Selective Inhibition of ADAM17 Efficiently Mediates Glycoprotein Ibα Retention During Ex Vivo Generation of Human Induced Pluripotent Stem Cell-Derived Platelets.

Donor‐independent platelet concentrates for transfusion can be produced in vitro from induced pluripotent stem cells (iPSCs). However, culture at 37°C induces ectodomain shedding on platelets of glycoprotein Ibα (GPIbα), the von Willebrand factor receptor critical for adhesive function and platelet lifetime in vivo, through temperature‐dependent activation of a disintegrin and metalloproteinase 17 (ADAM17). The shedding can be suppressed by using inhibitors of panmetalloproteinases and possibly of the upstream regulator p38 mitogen‐activated protein kinase (p38 MAPK), but residues of these inhibitors in the final platelet products may be accompanied by harmful risks that prevent clinical application. Here, we optimized the culture conditions for generating human iPSC‐derived GPIbα+ platelets, focusing on culture temperature and additives, by comparing a new and safe selective ADAM17 inhibitor, KP‐457, with previous inhibitors. Because cultivation at 24°C (at which conventional platelet concentrates are stored) markedly diminished the yield of platelets with high expression of platelet receptors, 37°C was requisite for normal platelet production from iPSCs. KP‐457 blocked GPIbα shedding from iPSC platelets at a lower half‐maximal inhibitory concentration than panmetalloproteinase inhibitor GM‐6001, whereas p38 MAPK inhibitors did not. iPSC platelets generated in the presence of KP‐457 exhibited improved GPIbα‐dependent aggregation not inferior to human fresh platelets. A thrombus formation model using immunodeficient mice after platelet transfusion revealed that iPSC platelets generated with KP‐457 exerted better hemostatic function in vivo. Our findings suggest that KP‐457, unlike GM‐6001 or p38 MAPK inhibitors, effectively enhances the production of functional human iPSC‐derived platelets at 37°C, which is an important step toward their clinical application. Stem Cells Translational Medicine 2017;6:720–730

Stem cells, megakaryocytes, and platelets.

Stem cells are an important tool for the study of ex-vivo models of megakaryopoiesis and the production of functional platelets. In this manuscript, we review the optimization of megakaryocyte and platelet differentiation and discuss the mechanistic studies and disease models that have incorporated stem cell technologies. Mechanisms of cytoskeletal regulation and signal transduction have revealed insights into hierarchical dynamics of hematopoiesis, highlighting the close relationship between hematopoietic stem cells and cells of the megakaryocyte lineage. Platelet disorders have been successfully modeled and genetically corrected, and differentiation strategies have been optimized to the extent that utilizing stem cell-derived platelets for cellular therapy is feasible. Studies that utilize stem cells for the efficient derivation of megakaryocytes and platelets have played a role in uncovering novel molecular mechanisms of megakaryopoiesis, modeling and correcting relevant diseases, and differentiating platelets that are functional and scalable for translation into the clinic. Efforts to derive megakaryocytes and platelets from pluripotent stem cells foster the opportunity of a revolutionary cellular therapy for the treatment of multiple platelet-associated diseases.

Generation of megakaryocytes and platelets from human subcutaneous adipose tissues

Recent advances in regenerative medicine have created a broad spectrum of stem cell research. Among them, tissue stem cell regulations are important issues to clarify the molecular mechanism of differentiation. Adipose tissues have been shown to contain abundant preadipocytes, which are multipotent to differentiate into cells including adipocytes, chondrocytes, and osteoblasts. In this study, we have first shown that megakaryocytes and platelets can be generated from adipocyte precursor cells. Human adipocyte precursor cells were cultured in conditioned media for 12 days to differentiate adipocytes, followed by 12 days of culture in media containing thrombopoietin. The ultrastructures of adipocyte precursor cell- and bone marrow CD34-positive cell-derived megakaryocytes and platelets were similar. In addition, adipocyte precursor cell-derived platelets exhibited surface expression of P-selectin and bound fibrinogen upon stimulation with platelet agonists, suggesting that these platelets were functional. This is the first demonstration that human subcutaneous adipocyte precursor cells can generate megakaryocyte and functional platelets in an in vitro culture system.

Metalloproteinase Regulation Determines Integrin αIIbβ3 Function and Enhances the Capacity of ES Cell-Derived Platelets.

To resolve the lack of sources for products used in blood transfusion therapy, the utilization of embryonic stem cells (ESCs) has been proposed. However, the use of ESC-derived cells has potential drawbacks including, immunological rejection and teratoma formation. Being fully differentiated cells lacking a nucleus, platelets can be irradiated to eliminate passenger ESCs and other lineages before transfusion. We previously established in vitro differentiation system whereby proplatelet-producing megakaryocytes can be derived from murine ESCs on OP9 stroma, but the platelets were generated with a low efficiency and exhibited weak agonist-induced integrin αIIbβ3 activation and spreading on immobilized fibrinogen. Here, we describe an improved method to obtain ESC-derived platelets of potential use for hemostasis and thrombosis in vivo. We generated a novel murine ESC line wherein the GPIbα promoter regulates EGFP expression as a marker (GP-G ESCs). The combination of flow cytometry with GP-G-derived embryoid bodies and OP9 co-culture enabled us to enrich integrin αIIb + c-kit + CD9 + Sca-1 − progenitors on day 5–6 of culture as a major fraction capable of differentiating into GFP+ mature megakaryocytes on day 8–10 in the presence of TPO. This strategy increased platelet production by 10-fold (P<0.01) compared to our previous report (PNAS, 2002, 99:12819). Interestingly, αIIb+platelets included 35–40% GPIbα-negative population besides GPIbα-positive on day 13–15, which was caused by an increased activity of matrix metalloproteinase (MMP) and TACE (ADAM17) to shed GPIbα in culture. Inhibition of MMP and TACE with GM6001 or TAP1 delayed the clearance rate on post transfusion recovery in vivo as transfused into a platelet-depleted mouse model. Maintaining GPIbα expression in the presence of MMP/TACE inhibitors restored the specific fibrinogen-bound to integrin αIIbβ3 and platelet spreading on fibrinogen as evidenced by the generation of filopodia and lamellipodia. Collectively, these results suggest that 1) ESC-derived αIIb+ c-kit + CD9+ Sca-1 − progenitors may contribute to enrich megakaryocytopoiesis at high efficiency; 2) inhibition of metalloproteinase activity to retain GPIbα expression is required for αIIbβ 3 integrin inside-out and outside-in signaling in ESC-derived platelets; and 3) these platelets may be useful alternatives for future clinical application.

Pathogenesis of Clostridium perfringens infection: mechanisms and mediators of shock.

Shock, a common complication of gas gangrene caused by Clostridium perfringens, is related to the elaboration of α- and θ-toxins in vivo. This study compared the relative potencies of θ- and α-toxins in a rabbit model and determined the role of endogenous mediators of toxin-induced shock. α-Toxin decreased cardiac index, mean arterial pressure, and heart rate and caused death in 83% of animals. θ-Toxin did not alter these parameters and caused death in only 25% of animals. α-Toxin also inhibited ex vivo cardiac contractility in a dose-dependent manner. Finally, both α-and θ-toxins were potent inducers of endothelial cell-derived platelet activating factor. α-Toxin, but not θ-toxin, also stimulated production of tumor necrosis factor by peripheral blood mononuclear cells. Thus, the fulminant nature of shock in patients with gas gangrene caused by C. perfringens is the sum of α-toxin's direct effects on myocardial contractility and both toxins' ability to induce production of potent endogenous mediators.