Icariin recovers the osteogenic differentiation and bone formation of bone marrow stromal cells from a rat model of estrogen deficiency-induced osteoporosis.

A number of recent studies have suggested that icariin (ICA), a class of phytochemical with numerous biological activities, may exert protective effects against postmenopausal bone loss. However, it remains unclear whether ICA regulates or improves the osteoblastic function of bone marrow stromal cells (BMSCs) in the treatment and prevention of osteoporosis. In the present study, the osteogenic differentiation of BMSCs from ovariectomy (OVX) rats was found to be significantly decreased in vitro compared with that in rats that had undergone a sham operation. Treatment with ICA at a dose of 10-5 M was shown to restore the osteogenic differentiation of BMSCs in OVX rats. The results indicated that ICA restored the differentiation and mineralization capacity of OVX-BMSCs, which had been induced by estrogen deficiency. The effects of this compound on alkaline phosphatase (ALP) activity and calcium deposition were also measured at various time points. The number of colonies and areas that stained positive for ALP expression, and mineralized bone nodules were analyzed histochemically at 14 and 21 days after the osteogenic induction. The expression of the runt-related transcription factor 2 and osterix bone metabolism biomarker proteins and genes were detected by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression of factors involved in the estrogen signaling pathway, estrogen receptor α (ERα), progesterone receptor (PR) and trefoil factor 1 (PS-2), was also detected by western blotting and RT-qPCR. ICA enhanced the expression of ERα, PR, PS-2 in OVX‑BMSCs, but this effect was abrogated when ICI 182780, an ER antagonist was added. Transplantation of BMSCs into nude mice demonstrated that ICA restored the osteogenic capability of OVX‑BMSCs in vivo. Therefore, it may be that ICA acts through the estrogen pathway in order to improve and restore the osteogenic differentiation and mineralization of OVX‑BMSCs, which are inhibited by estrogen deficiency and increasing age.