title: 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.
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China.
authors.forename: Zhi-Yun
authors.initials: ZY
authors.lastname: Feng
authors.forename: Zhen-Nian
authors.initials: ZN
authors.lastname: He
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism*; D000071116:ADAMTS5 Protein; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D053244:Osteoprotegerin / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013388:Succinimides / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000097792:Tissue Inhibitor of Metalloproteinase-4
chemical_list: D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; D048049:Extracellular Signal-Regulated MAP Kinases; D005452:Fluoresceins; D020929:Mitogen-Activated Protein Kinase Kinases; D053244:Osteoprotegerin; D013388:Succinimides; D019714:Tissue Inhibitor of Metalloproteinases; D048051:p38 Mitogen-Activated Protein Kinases; D000097792:Tissue Inhibitor of Metalloproteinase-4; C087165:5-(6)-carboxyfluorescein diacetate succinimidyl ester; C518696:Adamts5 protein, rat
keywords: osteoprotegerin; proliferation; chondrocyte; mitogen-activated/extracellular    signal-regulated    kinase    kinase; ADAMTS-5; tissue inhibitor of metalloproteinase-4