ObjectiveTo study the synergistic effect of p38MAPK and ERK1/2 in bone marrow mesenchymal stem cells (BMSCs), and to explore their influence on osteogenic differentiation in BMSCs cultures. MethodsMouse BMSCs were cultured in phenol red-free α-MEM containing osteogenic supplements (OS) for inducing osteogenic differentiation. The temporal sequence of osteogenic differentiation in BMSCs cultures was assayed by measuring alkaline phosphatase activity (ALP) and calcium deposition gene expression. The activation of p38MAPK and ERK1/2 was detected by western blotting using phospho-specific MAP kinase antibody. BMSCs were treated with the inhibitor of p38MAPK pathway(SB203580) or ERK1/2 pathway (PD98059), and osteogenic differentiation was measured. BMSCs were treated with SB203580 or sodium arsenite(ARS), a strong activator of p38MAPK, and the phosphorylation of ERK 1/2 was measured. BMSCs were treated with PP2A inhibitor, Okadaic acid(OA), the phosphorylation of ERK1/2 and osteogenic differentiation were measured. lmmunoprecipitation was used to test the binding interaction between PP2A and ERK1/2, and the effect of SB203580 on the interaction. ResultsTreatment of BMSCs with osteogenic supplements resulted in activation of p38MAPK and ERK1/2 that coincided with osteogenic differentiation. Inhibition of p38MAPK activation by SB203580, blocked the osteogenic differentiation, whereas inhibition of ERK1/2 activation by PD98059, enhanced the osteogenic differentiation in a dose-dependent manner.SB203580 treatment resulted in increased ERK1/2 phosphorylation. By contrast, ARS treatment resulted in decreased ERK1/2 phosphorylation. Inhibition of PP2A by OA resulted in increased ERK1/2 phosphorylation. OS-induced osteogenic differentiation was also attenuated by PP2A inhibition. Immunoprecipitation confirmed the association of PP2A with ERK1/2 in BMSCs cultures, which was decreased by SB203580 treatment. ConclusionThe present study demonstrates a synergistic effect between p38MAPK and ERK1/2 signaling pathways via PP2A in BMSCs cultures, which may regulate the osteogenic differentiation of BMSCs.

Objective: To investigate the regulation of curculigoside on osteogenic differentiation of MG63 and the protective effect on osteoporosis model mice. Methods: The effects of curculigoside on the survival rate of dexamethasone or H₂O₂ treated MG63 were detected by methyl thiazolyl tetrazolium (MTT). The specimens were divided into six groups: blank control group, blank administration group, model group (dexamethasone or H₂O₂ treatment group), low dose group (dexamethasone or H₂O₂+1.0 μmol/L curculigoside), medium dose group (dexamethasone or H₂O₂+2.5 μmol/L curculigoside) and high dose group (dexamethasone or H₂O₂+5.0 μmol/L curculigoside), the sample size of each group was 10. Western blotting was used to detect the expression of osteogenic differentiation-related proteins [type Ⅰ collagen, integrin β1, osteoblast-specific transcription factor (Osterix), osteocalcin and osteopontin] in MG63 cells after 1, 7 and 14 days incubated with 0, 1.0, 2.5 and 5.0 μmol/L of curculigoside. The sample size for each group at each time point was six. The experimental mice were divided into 4 groups: blank group, model group (dexamethasone treatment group), curculigoside low-dose group (dexamethasone+5 mg/kg curculigoside) and high-dose group (dexamethasone+45 mg/kg curculigoside), twenty each. After treatment, the tibia of the mice in each group were subjected to sacral HE staining. The number of osteoclasts was counted, and the levels of oxidative related factors in serum were determined by enzyme-linked immunosorbent assay (ELISA). Results: The MTT results showed that compared with the blank control group [(100±3.7)%], the cell survival rate decreased to (44.1±5.7)% after treatment with dexamethasone, and the survival rate increased to (79.7±3.8)% after treatment with 5.0 μmol/L of curculigoside. The cell survival rate decreased to (59.1±4.7)% after H₂O₂ treatment, and the survival rate increased to (80.8±3.5)% after treatment with 2.5 μmol/L of curculigoside. The results of Western blotting showed that the expression of type Ⅰ collagen and integrin β1 in MG63 cells was significantly increased after 1.0, 2.5 and 5.0 μmol/L of curculigoside for 1, 7 and 14 days compared with 0 μmol/L of curculigo side for the same period. After increasing (P<0.05), the expression of Osterix and osteocalcin was significantly increased after 1 day of incubation (P<0.05). However, compared with 0 μmol/L curculigoside treatment, the expression of osteopontin in MG63 cells was not significantly different after incubation with 1.0, 2.5, 5.0 μmol/L of curculigoside for 7 and 14 days (P>0.05). Compared with the blank group, the number of tibia osteoclasts in the osteoporosis model group increased. In the low-dose and high-dose groups of curculigoside, the tibia cortex was more continuous and the number of osteoclasts decreased. Compared with the blank group, the activity of oxygen in the osteoporosis model group was significantly increased (P<0.05), and superoxide dimutase and catalase were significantly decreased (P<0.05). Conclusions Curculigoside promotes the differentiation of MG63 cells by increasing the expression of osteoblast differentiation-related proteins, and has a certain therapeutic effect on dexamethasone-induced osteoporosis mice.