Background Osteoclast precursor cells are constitutively differentiated into mature osteoclasts on bone tissues. We previously reported that the continuous stimulation of RAW264.7 precursor cells with compressive force induces the formation of multinucleated giant cells via receptor activator of nuclear factor κB (RANK)-RANK ligand (RANKL) signaling. Here, we examined the bone resorptive function of multinucleated osteoclasts induced by continuous compressive force. Material/Methods Cells were continuously stimulated with 0.3, 0.6, and 1.1 g/cm 2 compressive force created by increasing the amount of the culture solution in the presence of RANKL. Actin ring organization was evaluated by fluorescence microscopy. mRNA expression of genes encoding osteoclastic bone resorption-related enzymes was examined by quantitative real-time reverse transcription-polymerase chain reaction. Mineral resorption was evaluated using calcium phosphate-coated plates. Results Multinucleated osteoclast-like cells with actin rings were observed for all three magnitudes of compressive force, and the area of actin rings increased as a function of the applied force. Carbonic anhydrase II expression as well as calcium elution from the calcium phosphate plate was markedly higher after stimulation with 0.6 and 1.1 g/cm 2 force than 0.3 g/cm 2 . Matrix metalloproteinase-9 expression decreased and cathepsin K expression increased slightly by the continuous application of compressive force. Conclusions Our study demonstrated that multinucleated osteoclast-like cells induced by the stimulation of RAW264.7 cells with continuous compressive force exhibit high dissolution of the inorganic phase of bone by upregulating carbonic anhydrase II expression and actin ring formation. These findings improve our understanding of the role of mechanical load in bone remodeling.
The association between obesity and inflammation is well documented in epidemiological studies. Proteolysis of extracellular matrix (ECM) proteins is involved in adipose tissue enlargement, and matrix metalloproteinases (MMPs) collectively cleave all ECM proteins. Here, we examined the effects of C-reactive protein (CRP), an inflammatory biomarker, on the expression of MMPs and tissue inhibitors of metalloproteinases (TIMPs), which are natural inhibitors of MMPs, in adipocyte-differentiated 3T3-L1 cells. We analyzed the expression of Fcγ receptor (FcγR) IIb and FcγRIII, which are candidates for CRP receptors, and the effects of anti-CD16/CD32 antibodies, which can act as FcγRII and FcγRIII blockers on CRP-induced alteration of MMP and TIMP expression. Moreover, we examined the effects of CRP on the activation of mitogen-activated protein kinase (MAPK) signaling, which is involved in MMP and TIMP expression, in the presence or absence of anti-CD16/CD32 antibodies. Stimulation with CRP increased MMP-1, MMP-3, MMP-9, MMP-11, MMP-14, and TIMP-1 expression but did not affect MMP-2, TIMP-2, and TIMP-4 expression; TIMP-3 expression was not detected. Adipocyte-differentiated 3T3-L1cells expressed FcγRIIb and FcγRIII; this expression was upregulated on stimulation with CRP. Anti-CD16/CD32 antibodies inhibited CRP-induced expression of MMPs, except MMP-11, and TIMP-1. CRP induced the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK but did not affect SAPK/JNK phosphorylation, and Anti-CD16/CD32 attenuated the CRP-induced phosphorylation of p38 MAPK, but not that of ERK1/2. These results suggest that CRP facilitates ECM turnover in adipose tissue by increasing the production of multiple MMPs and TIMP-1 in adipocytes. Moreover, FcγRIIb and FcγRIII are involved in the CRP-induced expression of MMPs and TIMP-1 and the CRP-induced phosphorylation of p38, whereas the FcγR-independent pathway may regulate the CRP-induced MMP-11 expression and the CRP-induced ERK1/2 phosphorylation.
In the present study, experimental periodontitis was induced by ligature in Wistar rats that were not on highfat or high-carbohydrate diet. The metabolic and infl ammatory parameters in the serum were examined in order to assess the eff ect of periodontitis-induced infl ammation on metabolic syndrome in individual without the genetic and dietary risk factors. Ligature-induced experimental periodontitis increased monocyte chemoattractant protein-1 and triglyceride levels in the serum, as well as homeostasis model assessment of insulin resistance, based on the concentration of serum glucose and insulin in Wistar rats. Furthermore, elevated triglyceride levels and altered expression of genes associated with glucose and lipid metabolism were also observed in the liver of rats with experimental periodontitis, suggesting that the onset of periodontitis induced metabolic syndrome independent of genetic and dietary risk factors.
High-magnitude mechanical strain inhibits bone nodule formation by reducing expression of bone morphogenetic protein-2 (BMP-2), Runt-related transcription factor 2 (Runx2), and muscle segment homeobox 2 (Msx2). Mechanical strain also induces production of proinflammatory factor prostaglandin E 2 (PGE 2) by osteoblasts. We measured the effect of mechanical strain-induced PGE 2 production on bone nodule formation and expression levels of bone formation-related factors. Osteoblast-like cells isolated from fetal rat calvariae were loaded with 18% cyclic tension force (TF) for 48 h in the presence or absence of NS-398, a selective inhibitor of cyclooxygenase-2. To investigate the effect of TF-induced PGE 2 on bone formation, bone nodule area on day 21 was measured by von Kossa staining. BMP-2, Runx2, and Msx2 expression levels were examined at 1 day after TF loading. Bone nodule formation was significantly inhibited by TF but was restored to control level by PGE 2 inhibition. Furthermore, TF loadinginduced reductions in expressions of these factors were restored to control level by PGE 2 suppression. These results indicate that PGE 2 production induced by high-magnitude mechanical strain inhibits bone nodule formation by reducing expression levels of bone formation-related factors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.