Expression of cell cycle cyclins in human megakaryoblast cell line exposed to simulated microgravity

Abstract

Background. Studies of weightlessness have shown that space flight causes serious physiological changes in a body. In mammalian cells, microgravity is able to induce and modulate key processes such as apoptosis, proliferation, migration, and adhesion. Despite growing interest to space biology and medicine, reports of cell cycle in microgravity remain controversial. Aim. This paper analyzes the expression of cell cycle cyclins in human megakaryoblastic leukemia cells exposed to simulated microgravity. Methods. Human megakaryoblastic leukemia (MEG-01) cells were seeded in culture flasks. Microgravity conditions were simulated using a Random Positioning Machine (RPM). Cells were placed at the center of the platform of the RPM (RPM group) and compared with a static control group (1 g). Cell cycle cyclin expression was analyzed by Western blotting and with a flow cytometer. Results. In the conditions of microgravity, MEG-01 showed comparable expression levels of cyclins E and D vs. the control group. However, concentrations of cyclins A and B increased during the first 96 h. Subsequently, concentrations of these cyclins decreased by 168 h compared to the previous time point and the control group. Conclusion. This study allowed a conclusion that MEG-01 cells exposed to RPM-modeled microgravity start proliferating and successfully finish the synthetic phase but stop in the G2 phase being unable to complete mitosis. However, at a later time (168 h), MEG-01 cells successfully adapt to the weightlessness conditions. In addition, the results are also consistent with reports of experiments on various cells under different conditions of simulated microgravity. Further studies of the effect of gravity on responses of megakaryocytes will provide insight into pathophysiology of human diseases acquired in extreme conditions.