Understanding platelet generation from megakaryocytes: implications for in vitro–derived platelets

Abstract

Platelets are anucleate cytoplasmic discs derived from megakaryocytes that circulate in the blood and have major roles in hemostasis, thrombosis, inflammation, and vascular biology. Platelet transfusions are required to prevent the potentially life-threatening complications of severe thrombocytopenia seen in a variety of medical settings including cancer therapy, trauma, and sepsis. Platelets used in the clinic are currently donor-derived which is associated with concerns over sufficient availability, quality, and complications due to immunologic and/or infectious issues. To overcome our dependence on donor-derived platelets for transfusion, efforts have been made to generate in vitro–based platelets. Work in this area has advanced our understanding of the complex processes that megakaryocytes must undergo to generate platelets both in vivo and in vitro. This knowledge has also defined the challenges that must be overcome to bring in vitro–based platelet manufacturing to a clinical reality. This review will focus on our understanding of committed megakaryocytes and platelet release in vivo and in vitro, and how this knowledge can guide the development of in vitro–derived platelets for clinical application.

Neonatal expression of RNA-binding protein IGF2BP3 regulates the human fetal-adult megakaryocyte transition

“…However, PSC-derived megakaryocytes display poor platelet yields (42), and extensive profiling has shown these cells to be even more ontogenically primitive than human FL megakaryocytes, likely reflecting a yolk-sac stage (10). Thus, ontogenic manipulation has the potential to improve both yield and quality of ex vivo-derived platelets.…”

Towards the Manufacture of Megakaryocytes and Platelets for Clinical Application

“…These first results suggest the feasibility of MK transfusion as a strategy to treat thrombocytopenia. However, potential secondary loci of thrombopoiesis were observed infusing ex vivo generated human MK into mice, representing a potential risk for pulmonary diseases [16,18,26]. Nevertheless, the data generated within these clinical trials support the feasibility of using in vitro manufactured PLTs as a future alternative or complementary strategy to PLT donation.…”

“…In particular, PLTs should be analyzed for their ability to adhere and aggregate after activation and for their circulation time in macrophage-depleted animals, and for their ability to incorporate in developing mouse thrombi [18]. According to Sim et al [16], minimal quality criteria for in vitro derived PLTs should include the responsiveness to agonists using standard aggregometry, the function in thrombus formation in vivo, and the determination of PLT half-life.…”

Development of autologous blood cell therapies

“…Megakaryocytes – the precursor cells giving rise to platelets - undergo endomitosis, a process of DNA replication without cytokinesis, prior to terminal maturation [19]. Mature megakaryocytes become polyploid and an individual mature megakaryocyte can release up to 11,000 platelets [19–21]. While in vitro culture with thrombopoietin (TPO) can result in megakaryocyte differentiation from HSPCs, co-culture with human telomerase catalytic subunit gene-transduced stromal cells and various cytokines can lead to large-scale and more robust generation of platelets from HSPCs [10,22–24].…”