Effect of Wasabi Leafstalk (Wasabia japonica MATSUM.) Extract on Bone Metabolism in Mouse Calvaria Tissue Culture

Abstract

The effect of wasabi leafstalk (Wasabia japonica MATSUM.) extract on bone metabolism in a tissue culture system using mouse calvaria in vitro was investigated. The calvaria tissues obtained from normal mice were cultured for 48 h at 37°C in 5% CO₂/95% air in Dulbecco's modified Eagle's medium (high glucose, 4.5g/dl) containing either vehicle or wasabi leafstalk extract (10, 50 and 250 μg/ml of medium). Wasabi leafstalk extract was obtained from a homogenate with 20% ethanol. The presence of wasabi leafstalk extract (10 μg/ml) caused a significant increase in calcium content and alkaline phosphatase activity in the bone tissues. With higher concentrations (50 and 250 μg/ml), however, the effect was weakened. The bone deoxyribonucleic acid (DNA) content was not significantly altered by the presence of wasabi leafstalk extract (10 and 50 μg/ml). The wasabi leafstalk extract-induced increase in bone calcium content was completely prevented by the coexistence of cycloheximide (10^-6 M), an inhibitor of protein synthesis, suggesting that the effect of wasabi leafstalk extract is based on a newly synthesized protein component. Meanwhile, the anabolic effect on bone calcium content was not seen in the presence of the ethanol extract (50 μg/ml) from loquat leaf, cherry leaf, dried shiitake, gabaron tea, green tea (sencha), muskmelon, satsuma mandarin, tomato, blueberry, and soy bean. The present study demonstrates that wasabi leafstalk extract has an anabolic effect on bone calcification, in vitro.