Ramie leaf Extract Alleviates Bone Loss in Ovariectomized Rats—The Involvement of ROS and Its Associated Signalings

Ramie leaf (Boehmeria nivea L.) has been traditionally used to treat gynecological and bone-related disorders. This study aims to evaluate the effect of Ramie leaf extracts (RLE) against osteoporosis in ovariectomized (OVX) rats. Female SD rats aged seven weeks were randomly assigned into five OVX and a sham-operated (sham) group. OVX subgroups include OVX, vehicle-treated OVX group; E2, OVX with 100 μg/kg 17β-estradiol; and RLE 0.25, 0.5, and 1, OVX rats treated with 0.25, 0.5, and 1 g/kg/day RLE, respectively. Two weeks into the bilateral ovariectomy, all the rats were orally administered with or without RLE daily for 12 weeks. OVX rats administered with RLE showed higher bone density, relatively low tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, and lower reactive oxygen species (ROS) within bone tissues compared to vehicle-treated OVX rats. Furthermore, supplementation of RLE improved bone mineral density (BMD) and bone microstructure in the total femur. RLE prevented RANKL-induced osteoclast differentiation and expression of osteoclastogenesis-related genes such as Cal-R, MMP-9, cathepsin K, and TRAP in RANKL-induced RAW264.7 cells. Moreover, RLE administration lowered the intracellular ROS levels by reducing NADPH oxidase 1 (NOX-1) and 4-hydroxynonenal (4HNE). These results suggest that RLE alleviates bone mass loss in the OVX rats by inhibiting osteoclastogenesis, where reduced ROS and its associated signalings were involved.