Inhibitory Effects of Tannic Acid on Osteoblast Differentiation in MC3T3-E1 Cells

This study examined the effects of tannic acid on osteoblast differentiation using MC3T3-E1 preosteoblast cells.Osteoblast differentiation was induced with ascorbic acid and β-glycerophosphate.The alkaline phosphatase (ALP) activity, mineralized nodule formation, osteoblast differentiation-related gene and protein expression, and runt-related transcription factor 2 (Runx2) promoter activity were analyzed after a tannic acid treatment.Tannic acid did not significantly affect cell viability at 1 μM, whereas cell viability was significantly reduced (P<0.001)at concentrations of 2 μM and above.Therefore, 1 μM tannic acid was used in subsequent experiments.On the other hand, the tannic acid treatment significantly reduced (P<0.01)ALP activity and mineralized matrix formation compared with the control group.In addition, tannic acid suppressed the expression of osteoblast differentiation-related markers, including Runx2, and decreased Runx2 promoter activity.These findings suggest that tannic acid inhibits osteoblast differentiation, at least in part, by suppressing Runx2-associated transcriptional regulation.This study provides fundamental information on the biological effects of tannic acid on osteoblast differentiation and may help to understand the role of polyphenolic compounds in bone metabolism.