Objective: To investigate the anti-apoptotic ability of synovium-derived mesenchymal stem cells (SMSCs) by comparing the apoptosis induced by tumor necrosis factor α (TNF-α) between SMSCs and bone marrow mesenchymal stem cells (BMSCs).
Methods: SMSCs and BMSCs were isolated with tissue adhering and density gradient centrifugation respectively, and cells at passages 3-5 were used in further experiments. After immunophenotype identification and differentiation induction, cells were divided into 4 groups. In the experimental groups, apoptosis of SMSCs and BMSCs were induced by 20 ng/mL TNF-α and 10 µg/mL cycloheximide, and cells were cultured in normal culture medium in the control groups. Cellular morphology were observed by inverted phase contrast microscope. After apoptosis induction for 24 hours, cell viability was determined by cell counting kit 8 assay and apoptotic index was detected by flow cytometer. Moreover, the level of Cleaved Caspase-8, 3 were determined by Western blot.
Results: Both SMSCs and BMSCs accorded with the definition criteria of MSCs according to results of immunophenotype identification and differentiation induction. After apoptosis induction, cells became shrinking and partially floated and cellular morphologies became worse than those in the control groups. After apoptosis induction for 24 hours, cell viabilities of SMSCs and BMSCs in the control groups were both 100%, and no apoptotic cells were observed. However, cell viabilities of SMSCs and BMSCs in the experimental groups were 60.13% ± 8.63% and 46.55% ± 10.54% respectively, which were both significantly lower than those in the control groups (P < 0.05), and cell viability in the SMSCs experimental group was significantly higher than that in the BMSCs experimental group (t = 3.152, P = 0.006). The apoptotic index was 36.54% ± 8.63% in the SMSCs experimental group and was 53.77% ± 11.52% in the BMSCs experimental group, both were significantly higher than the control groups (1.12% ± 0.24% and 1.35% ± 0.31%) (P < 0.05). What's more, it was significantly lower in SMSCs experimental group than that in BMSCs experimental group (t = 3.785, P = 0.001). Moreover, no expression of Cleaved Caspase-8, 3 was detected in the control groups. But the levels of Cleaved Caspase-8, 3 were significantly enhanced in the experimental groups and they were lower in SMSCs than in BMSCs (t = 13.870, P = 0.000; t = 7.309, P = 0.000).
Conclusion: TNF-α induced apoptosis is lower in SMSCs than in BMSCs, which means that SMSCs may have stronger anti-apoptosis ability than BMSCs.