title: Increased apelin serum levels and expression in human chondrocytes in osteoarthritic patients.
abstract: Apelin is a recently discovered hormone secreted by adipocytes. The aim of this study, therefore, was to evaluate the distribution of apelin in paired serum and synovial fluid (SF) of osteoarthritis (OA) patients, as compared to that in healthy controls, and to characterise the expression profile of apelin and its cognate receptor APJ in human chondrocytes. Apelin levels in serum and SF were analysed by enzyme-linked immunosorbent assay (ELISA). Expression of apelin and APJ in human chondrocytes was determined by real-time quantitative polymerase chain reaction (PCR). Apelin was found to be present in OA SF, and concentrations were positively correlated with the severity of OA. OA serum exhibited significantly elevated levels of apelin (2.18 ± 0.22 ng/ml) as compared to normal serum (1.31 ± 0.12 ng/ml) (p < 0.05), and serum apelin levels exceeded those in paired SF (p < 0.001). The apelin and APJ transcripts were identified in chondrocytes, and levels were significantly higher in OA cartilage than in healthy donors. These findings suggest that apelin may contribute to the onset and/or progression of OA, and may provide new insights into the pathophysiology of OA.
authors.affiliation: Department of Orthopedic Surgery, The Second Hospital of Medical College, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: Peng-fei
authors.initials: PF
authors.lastname: Hu
authors.forename: Jing-li
authors.initials: JL
authors.lastname: Tang
authors.forename: Wei-ping
authors.initials: WP
authors.lastname: Chen
authors.forename: Jia-peng
authors.initials: JP
authors.lastname: Bao
authors.forename: Li-dong
authors.initials: LD
authors.lastname: Wu
mesh_terms: D000368:Aged; D000073861:Apelin; D019902:Chondrocytes / Q000378:metabolism*; D018450:Disease Progression; D005260:Female; D015870:Gene Expression; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010003:Osteoarthritis / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology; D012720:Severity of Illness Index; D013582:Synovial Fluid / Q000378:metabolism
chemical_list: C115436:APLN protein, human; D000073861:Apelin; D036341:Intercellular Signaling Peptides and Proteins