LAUSR

One cause of thrombocytopenia in astronauts after spaceflight is decreased platelet production. To increase our understanding of thrombopoiesis in humans while in space, we investigated the effects of simulated microgravity, achieved using a random positioning machine (RPM), on megakaryoblastic cells (MEG-01 cell line). Exposure of MEG-01 cells to simulated microgravity for up to one week significantly increased cellular apoptosis compared to the static group (1 g-control). Flow cytometry analysis of the cell cycle revealed a significant increase in the percentage of cells in the G0/G1 phase after one week of RPM-exposure compared to the static group. Additionally, after one week, a difference in morphology was detected between the cells of the static group and the cells exposed to microgravity conditions. The expression of the CD33 surface marker was significantly decreased after a one week of microgravity exposure compared to the 1 g-control. We, therefore, concluded that in MEG-01 cells, simulated microgravity induces apoptosis, inhibits cell cycle progression of cells from G0/G1 into S phase, decreases cell proliferation, and decreases the expression of surface markers. We believe that, with insufficient physiological compensation, these changes under microgravity conditions may lead to disorders of megakaryocytes differentiation and/or decreased platelet production. It should also be noted that the human cell line MEG-01 could be a useful model for studying the effects of simulated microgravity on platelet production because of their ability to generate platelet-like particles.