Abstract
In this study, the effects of geraniin on osteoprotegerin/receptor activator of nuclear factor-κB ligand(OPG/RANKL) in regulating the proliferation of osteoblasts and suppression of osteoclast-like cells (OLC) in OLC-osteoblast co-cultured system in vitro were investigated. Osteoblasts were cultured and identified with alkaline phosphatase (ALP), gomori stain, and mineralized nodule stain. OLCs were isolated from long bones of Sprague-Dawley (SD) rats and identified with tartrate-resistant acid phosphatase(TRAP) stain. Methyl thiazolyl tetrazolium assay was used to examine the proliferation of osteoblasts, and immunocytochemistry and in situ hybridization to analyze the expression OPG/RANKL in osteoblasts co-cultured with osteoclasts under the action of geraniin, respectively. Geraniin could regulate the proliferation of osteoblasts MC3T3-E1, decrease the number of OLC in OLC-osteoblast co-cultured system, and inhibit the bone resorption areas and resorption pits of OLC in vitro experiments. Geraniin could promote the mRNA and protein expression levels of OPG and suppress those of RANKL in osteoblasts. These results indicate that geraniin has a promoting effect on the proliferation of osteoblasts and an inhibitory effect on the osteoclastic bone-resorption through regulating OPG/RANKL signaling pathway in OLC-OB co-cultured system.
Highlights
Bone morphogenesis and remodeling involve the bone formation from osteoblasts (OB) and the bone resorption by osteoclasts (OC)
OPG and RANKL are the important members of tumor necrosis factor (TNF) family found in recent years
We investigated the effect of geraniin on OLCinduced bone resorption in vitro and the mRNA and protein expression of OPG and RANKL in rat osteoblasts
Summary
Bone morphogenesis and remodeling involve the bone formation from osteoblasts (OB) and the bone resorption by osteoclasts (OC). OPG and RANKL are the important members of tumor necrosis factor (TNF) family found in recent years. OPG is a new open reading frame and encoding a protein with 401 amino acid residues discovered in the analysis of fetal rat intestinal cDNA sequencing by Simonet et al (1997). OPG is thought to inhibit osteoclastogenesis by disrupting the cell-to-cell signaling between osteoblastic stromal cells and osteoclast progenitors. RANKL is a type II transmembrane protein, and highly expressed in bone and bone marrow. The findings of OPG and RANKL as well as the transgenic characteristics and gene-knockout animals indicate that the cytokine system is the necessary factor for osteoclastic biology (Kiechl et al, 2006)
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