Wnt/β-catenin signaling has been known to influence bone formation and homeostasis. In this study, we investigated the canonical Wnt signaling regulation of osteogenic differentiation from periodontal ligament (PDL) fibroblasts. Stimulating PDL fibroblasts with lithium chloride (LiCl), a canonical Wnt activator, significantly increased mineralized nodule and alkaline phosphatase (ALP) activity in a time- and dose-dependent manner. LiCl up-regulated protein expression of osteogenic transcription factors, including the runt-related gene 2, Msx2, and Osterix 2, in the PDL fibroblasts. Treatment of these cells with LiCl also increased the mRNA levels of ALP, FosB, and Fra1 in a dose-dependent manner. Blockage of canonical Wnt signaling by treating the cells with DKK1 inhibited Wnt1-stimulated mRNA expression of these osteogenic factors. Furthermore, pretreatment with DKK1 reduced the ALP activity and matrix mineralization stimulated by Wnt1. Collectively, these results suggest that canonical Wnt signaling leads to the differentiation of PDL fibroblasts into osteogenic lineage with the attendant stimulation of osteogenic transcription factors.

These results suggest for the first time that ethanol extracts from PHCR seed have anti-inflammatory potential on LPS-stimulated macrophages through the down-regulation of ERK/p38- and NF-κB-mediated signalling pathways.

Little is known about the effects of mechanical forces on osteoclastogenesis by bone marrow macrophages (BMMs) in the absence of mechanosensitive cells, including osteoblasts and fibroblasts. In this study, we examined the effects of mechanical force on osteoclastogenesis by applying centrifugal force to BMMs using a horizontal microplate rotor. Our findings, as measured by an in vitro model system, show that tumor necrosis factor (TNF)-α is capable of inducing osteoclast differentiation from BMMs and bone resorption in the presence of macrophage-colony stimulating factor (M-CSF) and is further facilitated by receptor activator of nuclear factor-kappaB (NF-κB) ligand (RANKL). Application of force to BMMs accelerated TNF-α-induced osteoclastogenesis; this was inhibited either by anti-TNF-α or anti-TNF-α receptor but not by OPG. TNF-α also increased c-Fms expression at both mRNA and protein levels in BMMs. An anti-c-Fms antibody completely inhibited osteoclast differentiation and bone resorption induced by TNF-α but partially blocked osteoclastogenesis stimulated in combination with RANKL. These results suggest that TNF-α (in the presence of M-CSF) is capable of inducing osteoclastogenesis from BMMs, and that osteoclastogenesis is significantly stimulated by force application through the activation of c-Fms-mediated signaling. Overall, the present study reveals the facilitating effect of mechanical force on osteoclastic differentiation from BMMs without the addition of mechanosensitive cells.