Depletion of aquaporin 1 decreased ADAMTS‑4 expression in human chondrocytes

Abstract

Inflammation serves an important role in the progression of osteoarthritis (OA), and IL-1β may act as a catabolic factor on cartilage, reducing the synthesis of primary cartilage components type II collagen and aggrecan. Aquaporin 1 (AQP1) is a 28-kDa water channel formed of six transmembrane domains on the cell membrane. AQP1 is highly expressed in the anus, gallbladder and liver, and is moderately expressed in the hippocampus, ependymal cells of the central nervous system and articular cartilage. It was hypothesized that AQP1 may be highly expressed in OA cartilage and that it may increase the expression of catabolic factors during inflammatory OA progression. Therefore, the present study evaluated AQP1 functions in human OA articular chondrocytes. Primary chondrocytes were isolated from human hip and knee cartilage tissues, cultured and transfected with AQP1-specific small interfering RNA with or without subsequent IL-1β treatment. In vitro explant culture from hip cartilages were also prepared. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to assess the expression of AQP genes in human articular cartilage, AQP1 immunohistochemistry of the cartilages and explant culture, as well as RT-quantitative PCR, western blotting and immunocytochemistry/immunofluorescence of OA chondrocytes to evaluate the expression of AQP1, and catabolic and anabolic factors. RT-PCR results demonstrated that AQP0, 1, 3, 7, 9, and 11 were expressed in OA chondrocytes. Immunohistochemistry revealed that AQP1 was highly expressed in the superficial to middle zones of OA articular cartilages. Additionally, AQP1 mRNA was significantly higher in OA cartilage and IL-1β treatment significantly increased AQP1 expression in hip explant cartilage. Furthermore, AQP1 downregulation decreased a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-4 expression in OA chondrocytes, though it did not affect other associated genes. Immunofluorescence showed that AQP1 and ADAMTS-4 were co-localized. These findings indicated that AQP1 depletion may decrease ADAMTS-4 expression in human OA chondrocytes. Therefore, regulating AQP1 expression may be a strategy to suppress catabolic factors during OA progression.

Effects of IL-1β-induced ADAMTS-4/-5 and TAK1 on the degradation of cartilage aggrecan in the progression of human osteoarthritis

“…The reasons may be that the expression of ADAMTS-4 was inducible and sensitive to IL-1β stimulation, while the expression of ADAMTS-5 was constitutive and insensitive to the induction of IL-1β. These results were consistent with previous studies on the effect of IL-1β on the expression of ADAMTS-4/-5 associated with individual differences and enzyme activity in human OA chondrocytes [37,38]. This result suggested that both ADAMTS-4/-5 contributed to the degradation of cartilage aggrecan in IL-1β-treated human OA chondrocytes, while ADAMTS-4 seemed more sensitive to IL-1β in vitro.…”

The Role of Inflammation in the Pathogenesis of Osteoarthritis

“…Similarly, MMP-13, MMP-3, MMP-2, and MMP-9 increased in the cell line model of osteoarthritis [26,28]. Furthermore, several studies have investigated the MMP-13 level in osteoarthritis patients, and consistent observation is obtained, whereby the MMP-13 level increased significantly in patients with osteoarthritis [30,48,59,[73][74][75][76][77][78]. MMP-13, as a collagenase, is responsible for the degradation of type II collagen [79], which is the main collagen type in articular cartilage [80].…”

“…Hou et al showed that chemokine CX3CL1 induces MMP-3 production in a concentration-dependent and timedependent manner using synovial fibroblasts from patients with osteoarthritis (OASFs) [9]. Other than that, several studies showed increased MMP-3 in osteoarthritis [47,48,53,73,78,82,83]. The induction of MMP-3 has been related to miR-149 and miR-454 expression in osteoarthritis [51,84].…”

The relationship between abnormal Core binding factor-β expression in human cartilage and osteoarthritis

“…The inflammatory markers, especially interleukins [ 27 ] (ILs) and matrix metalloproteinases [ 28 – 30 ] (MMPs) have been widely investigated. In previous studies, IL-1β has been shown to play a key role in the development and progression of OA [ 31 , 32 ]. The results of Özler K et al [ 33 ] showed that MMP-13 expression in the joint fluid of patients with severe KOA was significantly related to the WOMAC score.…”