Simulated microgravity affects the proliferation and related genes expression in murine liver Kupffer cells

Abstract

Objective To investigate the effects of simulated microgravity on the proliferation and expression of related genes in murine liver Kupffer cells. Methods The rotary cell culture system (RCCS) was used to simulate the microgravity environment and culture the murine liver Kupffer cells, which were divided into simulated microgravity group (SMG) and normal gravity group (NG) at random, and were harvested after being cultured for 3, 5 and 7 days, respectively. The cell count and cell cycle were detected by hemocytometer and flow cytometry. The Kupffer cell’s expression of PCNA, Ki-67, ERK, CDK2 and Cyclin B were assayed by real-time fluorescent quantitative PCR (qPCR). Results After being cultured for 3 days, the number of Kupffer cells in SMG group were less than that in NG group (2.6±0.1 vs. 3.1±0.2, P<0.05), while after being cultured for 5 and 7 days, the number of Kupffer cells in SMG group were increased significantly compared with that in NG group (6.9±0.4 vs. 5.9±0.2, P<0.05; 8.4±0.3 vs. 6.5±0.3, P<0.05). The flow cytometry also revealed that at 3rd days of culture, the G0/G1 phase of Kupffer cells in SMG group was significantly higher than that in NG group (78.1±0.2 vs. 59.7±1.2, P<0.05), while the S phase and the G2/M phase were significantly lower than that in NG group (12.0±0.4 vs. 27.6±0.9, P<0.05; 9.9±0.3 vs. 12.7±0.4, P<0.05). In contrary, the G0/G1 phase of Kupffer cells being cultured for 5 days in SMG group was decreased (69.5±1.5 vs. 74.8±0.7, P<0.05), and the S phase and G2/M phase were increased (21.2±1.5 vs. 17.3±0.4, P<0.05; 9.3±0.4 vs. 7.9±0.4, P<0.05) significantly compared with those in NG group. After 7 days of culture, the G0/G1 phase of the SMG group was still decreased (73.9±1.9 vs. 81.7±1.3, P<0.05) while the S phase and the G2/M phase were also increased (18.9±1.9 vs. 12.1±0.8, P<0.05; 7.3±0.2 vs. 6.2±0.6) compared with the control. The qPCR assay showed that the expressions of PCNA, ki-67, ERK, CDK2 and Cyclin B in SMG were down-regulated at 3rd days of culture, and up-regulated from 5th to 7th days of culture compared with those of NG group. Conclusion The proliferation of murine liver Kupffer cells was depressed during microgravity stress period, and were then activated and enhanced through certain genes mediated modulation. Key words: Rotary cell culture system; Simulated microgravity; Liver; Kupffer cells; Proliferation; Genes