Osteoprotective Effect of Radix Scutellariae in Female Hindlimb-Suspended Sprague-Dawley Rats and the Osteogenic Differentiation Effect of Its Major Constituent

A number of medicinal herbs have demonstrated therapeutic effects for the prevention and treatment of disuse-induced osteoporosis. As a common ingredient in proprietary traditional Chinese medicines, the anti-osteoporosis effects of Radix Scutellariae extract (RSE, 50 mg/kg/day) were evaluated in a hindlimb suspended rat model. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry, and the micro-architecture observed by MicroCT assay with bone biomechanical properties evaluated by a three-point bending test. To elucidate potential mechanisms, the osteogenic differentiation effect of baicalin as the most abundant ingredient in RSE was investigated in rat bone marrow derived mesenchymal stem cells (rBMSC). After drug administration for 42 days, tibia-BMD was significantly increased to 0.176 ± 0.007 and 0.183 ± 0.011 g/cm(2) and f-BMD was enhanced to 0.200 ± 0.017 and 0.207 ± 0.021 g/cm(2) for RSE and ALE treatment, respectively, whereas tibia-BMD and femur-BMD of the HLS group were 0.157 ± 0.009 and 0.176 ± 0.008 g/cm(2). Deterioration of bone trabecula microstructure was improved by RSE and ALE with increased morphological parameters such as bone volume fraction, trabecular thickness, and trabecular number, as well as connectivity density compared to the HLS group (p < 0.01). A three-point bending test suggested that bone mechanical strength was also enhanced by RSE and ALE treatments with increased maximum stress, young’s modulus, maximum load, and stiffness compared to those of the HLS group (p < 0.05). Besides, serum TRACP levels were significantly suppressed by RSE and ALE treatments. Furthermore, in vitro studies demonstrated that baicalin significantly increased ALP activities and the formation of mineralized nodules in rBMSC. Conclusively, supplementation of RSE could significantly prevent weightlessness induced osteoporosis, which might attribute to the osteogenic differentiation enhancement effect of baicalin.