Upregulation of proteasome activity by 18α-GA promotes proliferation of late-passage BMSCs in vitro

AIM: To investigate the effect of 18 alpha-glycyrrhetinic acid (18α-GA) on delaying the senescent progress and promoting the proliferation in late-passage bone marrow mesenchymal stem cells (BMSCs). METHODS: Late-passage BMSCs were incubated with 2.0 mg /L 18α-GA or the same volume of DMSO for 30 d, and the cells were harvested to determine the proteasome activity. The expression of senescence-related proteins p53, p21 and p16 was detected by senescence-associated β-galactosidase (SA-β-Gal) staining and Western blot. The cell proliferation, the expression level of cell cycle-related proteins and cell cycle distribution of the cells were measured by CCK-8 assay, BrdU incorporation, Western blot and flow cytometry. RESULTS: Compared with DMSO group, the proteasome activity in 18α-GA group increased significantly by about 0.2 times (P<0.01). SA-β-Gal-positive cells in 18α-GA group decreased, and cell staining was lighter. The contents of p53 and p21 in 18α-GA group were decreased (P<0.05). The results of CCK-8 assay showed that the A value in 18α-GA group was 0.3 times higher than that in DMSO group (P<0.01). BrdU incorporation showed the increased proliferation in 18α-GA group compared with DMSO group (P<0.05). The cells in G₁ phase in 18α-GA group decreased significantly compared with DMSO group, while the cells in S phase increased significantly (P<0.05). The expression level of cyclin D1 in 18α-GA group was 2.8 times higher than that in DMSO group (P<0.01), and the CDK4 level was 1.4 times higher than that in DMSO group (P<0.05). CONCLUSION: Activation of the proteasome activity by 18α-GA delays the aging process in the BMSCs and promotes the cell proliferation via up-regulation of the cell cycle-related proteins.