Curculigoside promotes osteogenic differentiation of ADSCs to prevent ovariectomized-induced osteoporosis

Background: Curculigoside is a natural phenolic glycoside compound produced by Curculigo orchioides Gaertn. This study aimed to explore the effects of curculigoside in promoting the osteogenic differentiation of adipose-derived stem cells (ADSCs) as well as the underlying mechanism.

Methods: ADSCs were treated with curculigoside at different concentrations (0 μmol/L, 1 μmol/L, 2.5 μmol/L, 5 μmol/L, 10 μmol/L, and 20 μmol/L), and cell viability was assessed by CCK-8 assay. Then, the Alkaline Phosphatase (ALP) activity was determined, and alizarin red S (ARS) staining was performed to measure the extracellular mineralization of curculigoside. Information about protein-chemical interactions is provided by the search tool for interactions of chemicals (STITCH) database. Then, LY294002 was administered to explore the mechanism by which curculigoside promotes the osteogenic differentiation of ADSCs. Western blot assays were performed to assess changes in the expression of osteogenic-related markers and the phosphorylation of PI3K and Akt. Finally, we established an ovariectomized (OVX)-induced osteoporosis mouse model and administered curculigoside to explore the effects of curculigoside in preventing bone loss in vivo.

Results: The CCK-8 assay indicated that curculigoside did not induce cytotoxicity at a concentration of 5 μmol/L after 48 h. The ALP and ARS results revealed that the induced group had higher ALP activity and calcium deposition than the control group. Moreover, the curculigoside group exhibited increased biomineralization, ALP activity, and ARS staining compared to the induced and control groups, and these effects were partially inhibited by LY294002. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that the target genes of curculigoside were mainly involved in the PI3K-Akt signaling pathway. PCR and western blot analysis showed that the expression of RUNX2, ALP, and Osterix was upregulated in curculigoside-treated ADSCs, but this effect was partially reversed by the PI3K Inhibitor LY294002. Moreover, the curculigoside-treated group exhibited significantly increased phosphorylation of Akt to P-AKT compared with the osteogenic induction group. After treatment with curculigoside, the mice had a higher bone volume than the OVX mice, suggesting partial protection from cancellous bone loss. In addition, when LY294002 was added, the protective effects of curculigoside could be neutralized.

Conclusions: Curculigoside could induce the osteogenic differentiation of ADSCs and prevent bone loss in an OVX model through the PI3K/Akt signaling pathway.