Osteoprotegerin promotes the proliferation of chondrocytes and affects the expression of ADAMTS-5 and TIMP-4 through MEK/ERK signaling

Abstract

The involvement of osteoprotegerin (OPG) in bone metabolism has previously been established; however, whether OPG regulates chondrocytes directly and exerts precise cellular and molecular effects on chondrocytes remains to be determined. Thus, the present study aimed to investigate the direct effect of OPG on the viability, proliferation and functional consequences of chondrocytes. Primary chondrocytes were isolated from the knee of Sprague-Dawley rats. Passage 1 chondrocytes were identified by toluidine blue staining and used in the experiments. The cell proliferation induced by OPG at various concentrations was measured by a Cell Counting kit-8 (CCK-8) assay. Following pretreatment with mitogen-activated/extracellular signal-regulated kinase kinase (MEK) inhibitor U0126, extracellular signal-regulated kinase (ERK) inhibitor PD098059, and P38 mitogen-activated protein kinase (P38MAPK) inhibitor SB203580 for 30 min, chondrocytes were treated with OPG, and CCK-8 was performed. The cellular signals of MAPKs, including ERK, P38MAPK and c-Jun N-terminal protein kinase (JNK), were investigated by western blot analysis following treatment with OPG. The functional consequences following treatment with soluble OPG were analyzed by qPCR and western blot analysis. OPG increased chondrocyte proliferation with maximal effect at 10 ng/ml, and induced the phosphorylation of MEK and ERK but not P38MAPK or JNK. Suppression of ERK activity via PD098095 inhibited OPG-induced chondrocyte proliferation. Administration of OPG significantly downregulated ADAMTS‑5 and upregulated tissue inhibitor of metalloproteinase (TIMP)-4 production, but had no effect on the expression of TIMP-1, -2 and -3, insulin-like growth factor I, transforming growth factor-β, basic fibroblast growth factor, bone morphogenetic protein-2, collagen II, aggrecan and ADAMTS-4. Suppression of ERK activity via PD098095 inhibited the alteration of ADAMTS-5 and TIMP-4 expression induced by OPG. OPG therefore regulated the proliferation of chondrocytes via MEK/ERK signaling, and directly affected chondrocytes by influencing the expression profile of ADAMTS-5 and TIMP-4.

Effects of miR-145 on the inhibition of chondrocyte proliferation and fibrosis by targeting TNFRSF11B in human osteoarthritis

“…the dual-luciferase reporter assay further suggested that TNFRSF11B was a direct target of miR-145 in chondrocytes. TNFRSF11B, as a key regulator of the process of chondrogenesis, has been reported to be important in chondrocyte formation (18)(19)(20). In the present study, the overexpression of miR-145 repressed the expression of TNFRSF11B in C-20/A4 and CH8 cells and, as expected, interference of the expression of TNFRSF11B decreased chondrocyte growth and fibrosis.…”

Adenovirus-mediated osteoprotegerin ameliorates cartilage destruction by inhibiting proteoglycan loss and chondrocyte apoptosis in rats with collagen-induced arthritis

“…We previously revealed that OPG is able to suppress ADAMTS-5 expression in vitro (Feng et al 2013). In this study, we further demonstrated that the number of ADAMTS-5-positive cells in cartilage is reduced significantly by Ad-OPG treatment in vivo.…”

“…We previously found that OPG could inhibit ADAMTS-5 expression in chondrocytes in vitro (Feng et al 2013). In this study, we discovered that the ADAMTS-5-positive cells spreaded all over the full thickness of cartilage with the number increasing significantly in the cartilage of rats treated with a vehicle (Fig.…”

Mitral valve endothelial cells secrete osteoprotegerin during endothelial mesenchymal transition

“…The apparent loss of SDC4 could be due to protein destabilization after Hep I pre-treatment or the specific antibody used may require heparan sulphate to completely bind SDC4. Finally, since extracellular signal-regulated kinase 1 and 2 (ERK) phosphorylation was previously documented upon OPG treatment[13, 16], we analysed if Hep I could also block this phosphorylation. As shown in Figure 4G - bottom panels, Hep I pre-treatment were able to block ERK activation.…”