The regulatory effect of high mobility group box 1 on cell generation cycle of rat class fibroblast-like synovial cells

Objective:To investigate the effect of high mobility group box (HMGB) 1 on cell generation cycle of RSC364 synoviocytes and possible mechanism.Methods:RSC364 cells induced by 10 μg/L HMGB1 were collected in 6 h,12 h and 24 h respectively,as well as normal control group cells in vitro.The cell cycle distribution state and the expression of Cyclin D1/CDK4 proteins were tested by flow cytometric analysis (FCM),and then the expression of PCNA and p21 proteins was detected by immunocytochemistry(ICC)staining.Results:HMGB1 was significant effective on cell cycle distribution and proliferation index (PI) of RSC364 cells in 12 h and 24 h.The number of cells in G0/G1 phase was down-regulated,whereas cells in G2/M phase was up-regulated.Thus PI increased as well [(68.00±1.42) and (69.61±5.86) in 6 h,12 h respectively].Compared with those of the normal group (53.83±4.95) and 6 h HMGB1 induced group (55.98±6.34),there were significantly statistical difference (P0.01 or 0.05).ICC staining showed that the positive signal expression of PCNA and p21 was located in nucleus.The number of positive cells of PCNA increased and that of p21 decreased in time-dependently.HMGB1 could up-regulate the expression of Cyclin D1 proteins in time-dependent manner,they were (1.42±0.02),(1.65±0.03) and ( 1.67±0.01) from 6 h to 24 h.Compared with that of normal group(1.00±0.01),there were significantly statistical difference (P0.01).HMGB1 could increased the expression of CDK4 protein also,they were (1.26±0.23),(1.29±0.07) and (1.26±0.03) respectively.Compared with that of normal group(1.00±0.25),there were significantly statistical difference either (P0.01).No changes discovered among culture of 6 h,12 h and 24 h.Conclusion:HMGB1 could promote the proliferation of RSC364 cells by up-regulating the protein expression of Cyclin D1/CDK4,and by down-regulating p21 protein expression.