| Abstract |
To generate the huge number of platelets required for thrombocytopenia patients (200-300 billion per transfusion) ex vivo, megakaryopoiesis and thrombopoiesis must be both considered for substantial improvement. For the former, our key measure is to expand the immortalized megakaryocyte cell lines (imMKCLs) derived from pluripotent stem cells, embryonic stem cells or induced pluripotent stem cells (iPSCs) (Cell Stem Cell, 2014). For the latter, there have been an idea of bioreactors where shedding of platelets is promoted by flow-dependent shear stress as previously observed in bone marrow studies (Science, 2007; J Exp Med, 2015; etc.), but there have been no satisfactory prototype using flow-chamber system based alone on shear stress. We have recently found turbulent flow is critically involved in platelet shedding from mouse bone marrow megakaryocytes in vivo, thereby to develop a novel bioreactor system for ex vivo platelet generation. The bioreactor system, VerMES in 8L scale, achieved 100 billion-order platelet generation with intact function including normal hemostasis capability in mouse and rabbit models with thrombocytopenia (Cell, 2018). Meanwhile, we have recently recognized that remodeling of imMKCL megakaryocytes is required for intact/healthy platelet generation ex vivo, which could be regulated by such turbulent energy (Cell, 2018 and unpublished results). Question is what is sensing of “turbulent energy” in imMKCL/bioreactor system? Here we show that unique sensing system in imMKCL plays important roles, whereby HDAC6 and related signaling pathways regulate sensing machinery and downstream change of membrane structure of imMKCL towards platelet shedding.
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