U A, Papassotiriou I, Michalakakou K, Fessatou S, Fandridis E, Papachristou G, Terpos E: Higher levels of synovial fluid osteoprotegerin (OPG) and improved serum ratio of receptor activator of nuclear factorkappaB ligand (RANKL) to OPG correlate with disease severity in patients with main knee osteoarthritis. Clin Biochem 2008, 41:746-749. 18. Nelson AE, Fang F, Shi XA, Kraus VB, Stabler T, Renner JB: Failure of serum transforming growth factor-beta (TGF-beta1) as a biomarker of radiographic LIGHT Proteins Storage & Stability osteoarthritis at the knee and hip: a cross-sectional evaluation inside the Johnston County Osteoarthritis Project. Osteoarthritis Cartilage 2009, 17:772-776. 19. Niehrs C: Function and biological roles of the Dickkopf loved ones of Wnt modulators. Oncogene 2006, 25:7469-7481. 20. Grotewold L, Theil T, R her U: Expression pattern of Dkk-1 through mouse limb improvement. Mech Dev 1999, 89:151-153. 21. Grotewold L, R her U: Bmp, Fgf and Wnt signalling in programmed cell death and chondrogenesis throughout vertebrate limb development: the role of Dickkopf-1. Int J Dev Biol 2002, 46:943-947.Conclusions This study has revealed a significant reduce in plasma Dkk-1 of OA sufferers and illustrated a pronounced inverse correlation together with the degree of radiographic severity in individuals with primary knee OA. The data of this study assistance the finding that Dkk-1 might be a helpful prognostic parameter to reflect the disease severity of primary knee OA. Additionally, Dkk-1 levels in plasma have been straight correlated with those in synovial fluid. This study has been the very first to investigate such a correlation and additional studies might be needed to define the mechanisms underlying this association. Added investigations will be necessary to shed light on the feasible role of Dkk-1 involved within the pathogenesis of chronic degenerative joint disorder, with the aim of building successful pharmacological agents to delay the progression to osteoarthritis.Abbreviations ANCOVA: evaluation of co-variance; ANOVA: evaluation of variance; BMI: physique mass index; CI: self-assurance intervals; DKK-1: Dickkopf-1; ELISA: enzyme-linked immunosorbent assay; KL: Kellgren and Lawrence; LDL: low-density lipoprotein; LRP: low-density lipoprotein receptor-related proteins; OA: osteoarthritis; ROC: receiver-operating characteristic; SD: standard deviation; SPSS: statistical package for social sciences; WNT: Wingless. Acknowledgements This study was supported by the Ratchadapiseksompotch Fund, Faculty of Medicine, Chulalongkorn University, the Thailand Analysis Fund, the Commission on Greater Education, along with the National Study Council of Thailand. The authors also would like to thank Prof. Yong Poovorawan and Ms. Petra Hirsch for reviewing the manuscript, Ms. Piyanuch Bumrungpanichthaworn for technical help, Mr.Wasan Punyasang for statistical tips, and also the Chulalongkorn Healthcare Investigation Center (ChulaMRC) for kindly CD326/EpCAM Proteins Storage & Stability providing facilities. Author facts 1 Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. 2Department of Orthopaedics, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. Authors’ contributions SH was responsible for the conception and style from the study, the analysis and interpretation of the data, and drafting in the manuscript. AT, PY, and SN performed operations, acquired sufferers, and contributed to the sample collection. NS and ST assisted sample collection and data evaluation. All authors have read and approved the f.