Extract of Curculigo capitulata Ameliorates Postmenopausal Osteoporosis by Promoting Osteoblast Proliferation and Differentiation

Abstract

Postmenopausal osteoporosis (PMOP) is a bone disease characterized by bone thinning and an increased risk of fractures due to estrogen deficiency. Current PMOP therapies often result in adverse side effects. The traditional medicinal plant Curculigo capitulata is commonly used to strengthen bones and support kidney function, but its role in treating PMOP is not well understood. This study aims to investigate the therapeutic effects of the total extract of Curculigo capitulata (Eocc) on PMOP and to explore the underlying mechanisms. The major components of the extract were identified using HPLC. Transcriptomics was employed to predict potential targets. An osteogenic differentiation model of MC3T3-E1 cells was used in vitro. The osteogenic potential of the Eocc was assessed through CCK-8 cell viability assays, alkaline phosphatase (ALP) staining, Alizarin Red staining, Western blotting, and qPCR. MCF-7 and HEK-293 cells were utilized to evaluate the estrogen-like activity of Eocc. Apoptosis rates were detected by flow cytometry. In vivo, a bilateral ovariectomized mouse model of PMOP was used to further validate the in vitro findings through histopathological analysis and WB results. The results demonstrated that the Eocc promoted the proliferation of MC3T3-E1 cells, increased ALP activity, and stimulated the formation of osteogenic mineralized nodules. It also upregulated the expression of osteogenic markers (Runx2, OCN, OPN, and BSP) at both the protein and mRNA levels. The Eocc induced the activation of ERα both in vitro and in vivo, initiating the Src/PI3K/AKT signaling pathway, leading to the phosphorylation of GSK3β and subsequent osteogenesis. The activation of this pathway also stimulated the phosphorylation of mTOR and p70S6K while downregulating cleaved caspase-3 and caspase-9. Additionally, the Eocc reduced apoptosis during osteogenic differentiation and promoted cell proliferation. These findings suggest that the Eocc facilitates osteoblast proliferation and differentiation, improving bone integrity in PMOP mice, and may represent a promising therapeutic candidate for managing PMOP.