OBJECTIVETo investigate the effect of simulated microgravity on the proliferation of human monocytic cells THP-1 and the expression of tissue factor (TF) mRNA.

METHODSTHP-1 cells were cultured under a simulated microgravity environment using the rotating cell culture system (RCCS). The changes in the cell proliferation after microgravity culture were assessed by cell counting and cell cycle analysis with flow cytometry. RT-PCR was used to detect the changes in the expression of TF mRNA in THP-1 cells.

RESULTSCulture under simulated microgravity resulted in a significant decrease in the cell number of THP-1 cells in comparison with that of the control cells (P<0.01). After a 24-h culture under microgravity, the G0-Gl phase cells increased from the control level of (46.57∓1.64)% to (67.64∓2.71)% (P<0.05). The cells in both groups showed a low level of TF mRNA expression in the absence of LPS stimulation. A 4-h stimulation with LPS caused up-regulated expression of TF mRNA in both cells, but the microgravity group showed a significantly smaller increase in the expression (2.301∓0.179) than the control group (9.210∓1.328) (P<0.05).

CONCLUSIONMicrogravity can inhibit the proliferation of THP-1 cells and suppress the cellular expression of TF mRNA.