Enhancing effects of myricetin on the osteogenic differentiation of human periodontal ligament stem cells via BMP-2/Smad and ERK/JNK/p38 mitogen-activated protein kinase signaling pathway

Myricetin is a flavonoid that found in berries, onions, and red grapes. It has been reported to have various pharmacological effects such as anti-inflammation, anti-oxidant and anti-cancer activities. However, the underlying mechanisms of myricetin on osteogenic differentiation remain unknown in human periodontal ligament stem cells (hPDLSCs). In this study, we investigated the ability of myricetin to increase osteogenic differentiation and its underlying molecular mechanisms. Myricetin significantly increased cell proliferation, alkaline phosphatase (ALP) activity, and alizarin red-mineralization activity in hPDLSCs in a dose-dependent manner. Furthermore, myricetin dose-dependently increased osteogenic-related mRNA and protein levels. Interestingly, it enhanced osteogenesis by up-regulating bone morphogenetic protein-2 (BMP-2), which induced the expression of BMP receptor type IB, Smad-1/5/9. It also enhanced the phosphorylation of extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinases (MAPKs) and Smads. We confirmed that the treatment of myricetin increased phosphorylated GSK-3 beta and beta-catenin which is related to osteogenesis. In our studies, myricetin-induced increment of ALP activity was decreased by ERK (PD98059), JNK (SP600125), p38 (SB203580), and Smad 1/5/9 (LDN193189) inhibitors. ERK and p38 inhibitors showed the greatest inhibition among the four kinds of inhibitors. These results demonstrate that myricetin promoted osteogenic differentiation by the up-regulation of ALP activity and expression of osteogenic-related factors through BMP-2/Smad and ERK/JNK/p38 MAPK pathways.