EFFECTS OF SIMULATED MICROGRAVITY ON CELL CYCLE IN HUMAN ENDOTHELIAL CELLS

摘要

Endothelial cells, playing crucial role in pathogenesis of many diseases, are highly sensitive to low gravity conditions. In this study, we analyzed changes in the cell cycle after the endothelial-like EA.hy926 cells exposure to simulated microgravity using 3D-clinostat (Dutch Space, Astrium Company, NL). EA.hy926 cells were seeded in OptiCell cell culture system, mounted in a 3D-clinostat, and cultured at 37°C in a humidified atmosphere of 95% air and 5% CO_2. The cell cycle distribution of EA.hy926 cells was analyzed by propidium iodide staining of cellular DNA content, and flow cytometry FACSCalibur. The percentages of cell population in G0/G1, S or G2 phases were calculated from histograms by the Cell Quest software. Cell cycles determined by flow cytometry showed, that percentage of the cells in the G0/G1 phase after 24 and 96 h of clinorotation were significantly increased as compared to control group, however, after 120 h and 168 h of clinorotation, the difference was not significant. Under normal conditions percentage of the cells in the G0/G1 phase was 65.5%, 70.4% and 76.4%, 81.4% after 24, 96 and 120, 168 h, respectively, whereas after 24, 96 h and 120, 168 h of clinorotation it made 76.6%, 87.2% and 74.1%, 80.6 %, respectively. Percentage of the cells in the S phase significantly decreased from 25.5% to 15.0% and from 22.0% to 7.9% after 24 and 96 h, while after 120 h and 168 h of clinorotation the difference was not significant. Thus, we showed that simulated microgravity inhibits the cell cycle progression of human EA.hy926 cells from the G0/G1 to the S phase. We observed an effect of a hibernation-like state, when the growth of the cells in the clinorotation group slowed, but did not stop. Our results confirm the experiments, which showed the ability of cells to adapt to changes in the gravitational field. However, our data also showed that endothelial EA.hy926 cells were less resistant to stress as compared to the human neuroblastoma cells SHSY-5Y, which we examined in a previous study. Our experiments support the conclusion, that the adverse effects of simulated microgravity have various impacts on different kinds of cells.