title: Down-regulation of adiponectin receptors in osteoarthritic chondrocytes.
abstract: The objective of this study was to investigate the expression of adiponectin receptors (AdipoR1, R2, and T-cadherin) in both normal subjects and patients with knee osteoarthritis (OA). We used immunofluorescence to assess expression of adiponectin receptors in the chondrocytes of normal subjects (n = 3) and OA patients (n = 3). We also studied mRNA expression of adiponectin receptors in both groups by real-time polymerase chain reaction (real-time PCR). Finally, we utilized Western blotting to confirm the presence of adiponectin receptors. As compared with osteoarthritic chondrocytes, normal chondrocytes showed stronger immunoreactivity for AdipoR1, AdipoR2, and T-cadherin. The expression levels of both AdipoR1 and AdipoR2 mRNA were significantly lower in the osteoarthritic chondrocytes compared with those in the normal chondrocytes, 19 ± 2 and 36 ± 3 % of normal chondrocytes, respectively (P < 0.001). T-cadherin mRNA expression levels of the osteoarthritic chondrocytes were also lower than those in the normal chondrocytes, but not statistical significant (P = 0.072). The expression levels of AdipoR1 and AdipoR2 protein were significantly higher in the normal chondrocytes compared with those in the osteoarthritic chondrocytes (P < 0.001, P < 0.01, respectively). T-cadherin protein expression level of the normal chondrocytes was also higher than those in the osteoarthritic chondrocytes, but the difference is not statistical significant (P = 0.114). Expression of adiponectin receptors protein in normal and osteoarthritic chondrocytes is consistent with its mRNA expression levels. In conclusion, we report for the first time down-regulation of adiponectin receptors (AdipoR1, R2, and T-cadherin) in osteoarthritic chondrocytes. Decreased adiponectin receptors in OA may reduce the tissue sensitivity to adiponectin, thus lost the protection from adiponectin in the progression of OA.
authors.affiliation: Department of Orthopedics, Jinling Hospital, Southern Medical University, Nanjing, 210002, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Cai
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Wang
authors.forename: Chuanzhi
authors.initials: C
authors.lastname: Xiong
authors.forename: Lianqi
authors.initials: L
authors.lastname: Yan
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Yongchao
authors.initials: Y
authors.lastname: Fang
authors.forename: Jianning
authors.initials: J
authors.lastname: Zhao
mesh_terms: D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D019902:Chondrocytes / Q000378:metabolism*; D015536:Down-Regulation; D006801:Humans; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054419:Receptors, Adiponectin / Q000235:genetics / Q000378:metabolism*
chemical_list: C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D015820:Cadherins; C099972:H-cadherin; D012333:RNA, Messenger; D054419:Receptors, Adiponectin