Objective To develop an apoptosis model of nucleus pulposus cells in cell culture.Methods To mimic the nutrient-deficient microenvironment of degenerative intervertebral disc,nucleus pulposus cells derived from infant SD rat disc were cultured under serum limiting conditions.Nucleus pulposus cells were cultured in culture medium contai-ning 1%, 3%, 5%, 8%and 10%fetal bovine serum( FBS) respectively to select the optimum FBA concentration.Apoptosis was assessed by flow cytometry, Western blot,cell counting kit, and immunofluorescence technique.Results The flow cy-tometry revealed that apoptosis rate of the nucleus pulposus cells increased with decreasing concentration of FBS, and 3%FBS used in the experimental group was the most effective concentration to induce apoptosis(P<0.05).Western blot dem-onstrated significantly higher expression of Bax and caspase-3 enzyme in the 3%FBS group than in the 10%FBS group, while bcl-2 activity decreased.The results of CCK-8 test indicated that the nucleus pulposus cells got slower proliferation in the medium containing 3%FBS.Immunofluoresence analysis showed that FAS expression was significantly higher in the 3%FBS group than in the 10%FBS group.Conclusions 3%FBS condition may induce apoptosis in the nucleus pulposus cells and compromise the cell function to induce intervertebral disc degeneration.The caspase family should be involved in the process.

Objective: To investigate the expression of histone methyltransferase G9a in gastric cancer tissues and its correlation to prognosis, and to observe the effect of G9a inhibitor on the proliferation and apoptosis of gastric cancer cells. Methods: The expression level of G9a in gastric cancer tissues and its correlation to prognosis were analyzed by using the Kaplan-Meier Plotter and Oncomine database. Human gastric cancer cell line SGC-7901 and MKN-45 were selected as study subject. The expression level of G9a protein was detected by Western blotting. The morphological change of gastric cancer cells after the treatment of G9a inhibitor BIX01294 was observed. CCK-8 proliferation experiment and plate colony formation assay were used to examine the proliferation ability and clone formation rate of gastric cancer cells. The changes of cell apoptosis were detected by Annexin-V staining. Results: G9a was highly expressed in gastric cancer tissues (P<0.01), and the high expression of G9a was positively correlated with poor prognosis of gastric cancer patients (P<0.01). After the treatment of BIX01294, the morphology of gastric cancer cells was changed, the volume of gastric cancer cells reduced, the intercellular connections disappeared, and even the apoptotic manifestations appeared, such as the shrinking,, becoming round and cast-off etc. BIX01294 could significantly inhibit the proliferation and colony formation but promote the apoptosis of gastric cancer cells (all P<0.05). Conclusion: Histone methyltransferase G9a was highly expressed in gastric cancer tissues, and its high expression level was positively correlated with poor prognosis. The proliferation of gastric cancer cells was obviously inhibited while the apoptosis was significantly promoted after inhibiting G9a expression.