Plastrum Testudinis Extracts Promote BMSC Proliferation and Osteogenic Differentiation by Regulating Let-7f-5p and the TNFR2/PI3K/AKT Signaling Pathway.

BACKGROUND/AIMS: Plastrum testudinis extracts (PTE) show osteoprotective effects on glucocorticoid-induced osteoporosis in vivo and in vitro. However, the underlying molecular mechanism of PTE in promoting osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is unclear.

METHODS

BMSC proliferation was investigated using the Cell Counting Kit-8 assay. BMSC differentiation and osteogenic mineralization were assayed using alkaline phosphatase and Alizarin red staining, respectively. The mRNA expression levels of Let-7f-5p, Tnfr2, Traf2, Pi3k, Akt, β-catenin, Gsk3β, Runx2, and Ocn were measured using real time quantitative polymerase chain reaction. Protein levels of TNFR2, TRAF2, p-PI3K, p-AKT, p-β-CATENIN, and p-GSK3β were analyzed by western blotting. The functional relationship of Let-7f-5p and Tnfr2 was determined by luciferase reporter assays.

RESULTS

The optimum concentration for PTE was 30 μg/ml. PTE significantly promoted BMSC osteogenic differentiation and mineralization after 7 and 14 days in culture, respectively. The combination of PTE and osteogenic induction exhibited significant synergy. PTE upregulated Let-7f-5p, β-catenin, Runx2, and Ocn mRNA expression, and downregulated Tnfr2, Traf2, Pi3k, Akt, and Gsk3β mRNA expression. PTE inhibited TNFR2, TRAF2, and p-β-CATENIN protein expression, and promoted p-PI3K, p-AKT, and p-GSK3β protein expression. In addition, Tnfr2 was a functional target of Let-7f-5p in 293T cells.

CONCLUSIONS

Our results suggested that PTE may promote BMSC proliferation and osteogenic differentiation via a mechanism associated with the regulation of Let-7f-5p and the TNFR2/PI3K/AKT signaling pathway.