ABSTRACT
The recent identification of receptor activator of nuclear factor-kappaB ligand (RANKL)/RANK/osteoprotegerin (OPG) cytokine system has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK is responsible for osteoclast differentiation. In the present study, we evaluated whether soluble RANK (sRANK) could act as an antagonist of RANKL and down-regulate osteoclastogenesis and bone resorption in vitro. The prokaryotic expression vector coding for sRANK was constructed. Then the construct was introduced into E. coli Origami B (DE3) competent cells and recombinant sRANK was successfully produced and purified through affinity chromatography. sRANK reduced osteoclast-like cell (OLC) formation and resorption pit formation induced by parathyroid hormone (PTH) in a dose-dependent manner. In addition, sRANK significantly inhibited PTH-induced mRNA expression of carbonic anhydrase II and tartrate-resistant acid phosphatase in murine bone marrow cells as confirmed by using semi-quantitative RT-PCR. The down-regulation was highly correlated with the effect of sRANK on OLC formation from marrow cells. These data demonstrate the anti-resorptive effects of sRANK in vitro and highlight the potential of sRANK as a novel therapeutic approach to bone disorders characterized by enhanced bone resorption.
Subject(s)
Animals , Humans , Mice , Bone Marrow Cells , Cell Biology , Bone Resorption , Cell Differentiation , Cells, Cultured , Escherichia coli , Genetics , Metabolism , Osteoclasts , Cell Biology , Osteoprotegerin , Physiology , Parathyroid Hormone , Physiology , RANK Ligand , Physiology , Receptor Activator of Nuclear Factor-kappa B , Genetics , Physiology , Recombinant Proteins , Genetics , PharmacologyABSTRACT
<p><b>OBJECTIVE</b>To investigate the distribution of tetracycline-arginine-glycine-aspartate-tyrosine (T-RGDY) in mice and its effect on bone.</p><p><b>METHODS</b>125-labeled T-RGDY was studied for its distribution in mice and for its effects on bone by histomorphometry in ovariectomized rats.</p><p><b>RESULTS</b>The 125I-labeled T-RGDY was more concentrated in the osteoporotic bone than in the normal bone. Compared with ovariectomy group, the morphologic index such as trabecular bone volume/total tissue volume (TBV/TTV), TBV/sponge bone volume (SBV), and mean trabecular plate thickness (MTPT) in T-RGDY group significantly increased (P < 0.05). As compared with sham operation group, MTPT significantly increased in T-RGDY group (P < 0.05), while TBV/SBV and mean trabecular plate density significantly decreased (P < 0.05), and TBV/TYV and mean trabecular plate spacing were almost the same as those in sham operation group (P > 0.05).</p><p><b>CONCLUSION</b>T-RGDY may concentrate in bone tissue to a certain degree, which is closely related with the status of bone remodeling. T-RGDY may inhibit the bone loss caused by ovariectomy.</p>