Gan-Lu-Yin (GLY), a traditional Chinese herbal medicine, shows
therapeutic effects on
periodontitis, but that mechanism is not well known. This study aims to clarify the precise mechanism by investigating the inhibitory effects of GLY extracts on osteoclastogenesis in vitro and on
bone resorption in
periodontitis in vivo. RAW264.7 cells are cultured with soluble
receptor activator of nuclear factor-kappa B (sRANKL) and GLY extracts (0.01-1.0 mg/mL), and stained for
tartrate-resistant acid phosphatase (TRAP) to evaluate osteoclast differentiation. Experimental
periodontitis is induced by placing a
nylon ligature around the second maxillary molar in rats, and rats are administered GLY extracts (60 mg/kg) daily for 20 days. Their maxillae are collected on day 4 and 20, and the levels of alveolar
bone resorption and osteoclast differentiation are estimated using micro-computed tomography (CT) and histological analysis, respectively. In RAW264.7 cells, GLY extracts significantly inhibit sRANKL-induced osteoclast differentiation at a concentration of more than 0.05 mg/mL. In experimental
periodontitis, administering GLY extracts significantly decreases the number of TRAP-positive osteoclasts in the alveolar bone on day 4, and significantly inhibits the
ligature-induced
bone resorption on day 20. These results show that GLY extracts suppress
bone resorption by inhibiting osteoclast differentiation in experimental
periodontitis, suggesting that GLY extracts are potentially useful for oral care in
periodontitis.