Phillyrin Prevents Ovariectomy-Induced Osteolysis by Inhibiting Osteoclast Differentiation

Postmenopausal osteoporosis is a metabolic disease caused by an imbalance between osteoclasts and osteoblasts. At present, the drug strategy for treating postmenopausal osteoporosis has some limitations and is unable to satisfy the demands of patients. Phillyrin (Phil) is an herbal extract from Forsythiae Fructus, with an inhibitory effect on osteolysis. In this study, we described the role of Phil in ovariectomy-induced osteoporosis and its effect on osteoclast differentiation in vitro. Eighteen female C57BL/6 mice were randomly divided into three groups: sham group (sham surgery and injection with 0.9% normal saline), ovariectomized group (ovariectomy and injection with 0.9% normal saline), and Phil group (ovariectomy and injecting Phil with 100 mg/kg for 2 days). Mice were sacrificed after 6-week Phil administration and femurs were harvested for microcomputed tomography (micro-CT) and histomorphology analyses. In vitro, we used different concentrations of Phil to study its effect on osteoclastogenesis. The results showed that the BV/TV, Tb.Th, and Tb.N in trabecular bone were increased in the Phil group compared with the OVX group, and the trabecular bone mass was remarkably decreased in the OVX group compared with the sham group. The number of osteoclasts was increased in the OVX group compared to the sham group, and the number and area of osteoclasts were decreased in the Phil group compared to the control group. Compared with the OVX group, the number and area of osteoclasts were reduced in the Phil group. In conclusion, Phil could inhibit the formation of osteoclasts, promote the growth of bone trabecular, and relieve osteoporosis caused by ovariectomy, with a certain clinical adoption value.