Osteogenic Activity of Yellow Flag Iris (Iris pseudacorus) Extract Modulating Differentiation of Osteoblasts and Osteoclasts

Abstract

Bone integrity is maintained through a balance between bone formation by osteoblasts and bone resorption by osteoclasts. Imbalance of the process results in metabolic bone diseases such as osteoporosis. This study investigated the yellow flag iris extract (YFIE) and revealed its anti-osteoporotic effects in osteoblastic MC3T3-E1 mouse cells and RAW 264.7 murine macrophages. When osteoblasts were treated with 1–20 μg/ml YFIE in an osteogenic medium, the bone nodule formation by calcium deposits was markedly enhanced during differentiation. Consistently, YFIE stimulated alkaline phosphatase activity and collagen type I secretion with a substantial effect on osteoblast proliferation. On the other hand, RAW 264.7 macrophages were pre-incubated with 1–20 μg/ml YFIE for 5 days in the presence of receptor activator of nuclear factor-κB ligand (RANKL). Non-toxic YFIE markedly attenuated the differentiation of macrophages to multi-nucleated osteoclasts. YFIE diminished RANKL-elevated tartrate-resistant acid phosphatase activity and bone resorption. In addition, the YFIE treatment retarded RANKL-induced cathepsin K production and carbonic anhydrase II expression, both of which are involved in bone resorption. Therefore, YFIE potentially posesses therapeutic agents that may prevent osteoporosis through promoting bone formation and reducing bone resorption.