Aqueous extract of Petasites japonicus leaves promotes osteoblast differentiation via up-regulation of Runx2 and Osterix in MC3T3-E1 cells

Background/objectives: Petasites japonicus Maxim (P. japonicus) has been used as an edible and medicinal plant and contains many bioactive compounds. The purpose of this study is to investigate the effect of P. japonicus on osteogenesis.

Materials/methods: The leaves and stems of P. japonicus were separated and extracted with hot water or ethanol, respectively. The total phenolic compound and total polyphenol contents of each extract were measured, and Alkaline Phosphatase (ALP) activity of each extract was evaluated to determine their effect on bone metabolism. To investigate the effect on osteoblast differentiation of the aqueous extract of P. japonicus leaves (AL), which produced the highest ALP activity among the tested extracts, collagen content was measured using the Sirius Red staining method, mineralization using the Alizarin Red S staining method, and osteocalcin production through enzyme-linked immunosorbent assay analysis. Also, real-time reverse transcription polymerase chain reaction was performed to investigate the mRNA expression levels of Runt-related transcriptional factor 2 (Runx2) and Osterix.

Results: Among the 4 P. japonicus extracts, AL had the highest values in all of the following measures: total phenolic compounds, total Polyphenols, and ALP activity, which is a major biomarker of osteoblast differentiation. The AL-treated MC3T3-E1 cells showed significant increases in induced osteoblast differentiation, collagen synthesis, mineralization, and osteocalcin production. In addition, mRNA expressions of Runx2 and Osterix, transcription factors that regulate osteoblast differentiation, were significantly increased.

Conclusions: These results suggest that AL can regulate osteoblasts differentiation, at least in part through Runx2 and Osterix. Therefore, it is highly likely that P. japonicus will be useful as an alternate therapeutic for the prevention and treatment of osteoporosis.

MC3T3-E1 cell; Osterix; Petasites japonicas (butterbur); Runt-related transcriptional factor 2; osteoblast.