Icariine Restores LPS-Induced Bone Loss by Downregulating miR-34c Level

Bacteria-induced inflammatory responses cause excessive bone resorption in chronic inflammatory diseases such as septic arthritis, osteomyelitis, and orthopedic implant failure. Icariine has been reported to facilitate the bone healing and reduce the occurrence of osteoporosis in clinical, moreover, laboratory studies which have proved that Icariine promotes the proliferation and differentiation of osteoblasts in vitro. The present study aimed to evaluate the effects of Icariine on lipopolysaccharide (LPS)-induced bone loss via an osteogenic-in vitro model and to elucidate the underlying molecular mechanisms. Here, we showed that Icariine restored LPS-induced bone loss in a dose-dependent manner without any cytotoxicity even at 100 μM in an osteogenic-in vitro model. Interestingly, Icariine restored the protein expression of Runx2, a key transcription factor for osteogenesis, but had no effect on its mRNA expression level. MiRNA-34c was dramatically upregulated after LPS stimulation; however, Icariine preincubation reversed miRNA-34c level. Western blot analysis showed that overexpression of miR-34c markedly inhibited the expression of osteogenic gene makers such as alkaline phosphatase (ALP), Runx2, OPN, and BMP2. ALP activity analysis and Alizarin Red S staining exhibited that both Icariine-induced osteogenic differentiation and mineral nodule formation were significantly inverted by overexpression of miR-34c. Western blot results also showed that Icariine notably inhibited LPS-induced phosphorylation of JNKs, p38, IkBα, IKKβ, and p65. Taken together, our studies suggested that Icariine restored LPS-induced bone loss by downregulating miR-34c level and suppressing JNKs, p38, and NF-kB pathways, which highlighted the potential use of Icariine as a therapeutic agent in the treatment of bacteria-induced bone loss diseases.