Dishevelled-2 modulates osteogenic differentiation of human synovial fibroblasts in osteoarthritis

Abstract

Dishevelled (Dvl)-2 represents one of the cytoplasmic proteins, which serves as a pivotal hub in signaling intermediates through a number of different signaling pathways associated with the Wnt family. The aim of the present study was to investigate the roles and mechanisms of Dvl-2 on synovial fibroblasts (SFBs) in osteoarthritis (OA). A Cell Counting kit-8 (CCK-8) assay was used to determine cell viability. An alkaline phosphatase (ALP) test kit was used to measure the activity of ALP. Western blot and reverse transcription-quantitative polymerase chain reaction analysis were used to evaluate the protein and mRNA expression, respectively. The results suggest that depletion of Dvl-2 significantly decreased the expression of osteoprotegerin (OPG) and ALP (P<0.05) and significantly increased the expression of receptor activator of nuclear factor-?B ligand (RANKL), ALP, osteonectin (ON), osteocalcin (OCN) and osterix (P<0.05). In addition, the depletion of Dvl-2 also significantly inhibited the expression of runt-related transcription factor 2 (Runx-2) and ?-catenin in SFBs (P<0.05). The effect of Dvl-2 over-expression was opposite to the effect of Dvl-2 silencing. The inactivation of Wnt3a reversed the effect of Dvl-2 silencing. In conclusion, the results indicate that Dvl-2 regulated osteogenic differentiation of SFBs in OA. and joint-level factors involving malalignment, injury, and abnormal loading of the joints (2). Though OA leads to great suffering to patients, seriously affects their life qualities, and further raises a serious burden on the entire social economy. However, there is no drug that is able to effectively delay or prevent the progression of OA. Joint replacement is the only medical treatment during the middle and late stages of OA diease. However, studies have shown that synovial inflammation plays a crucial role in the development and progression of OA. Due to the high expression of inflammatory mediators in early OA synovial tissues, acute synovitis may be the origin of OA (3). Synovial membrane is a special type of cementi-tious tissue that consists of a lining layer, a lining under-layer, and an outer edge of the lining fuses with the joint capsule (4). Synovial cells can be divided into macrophages, fibroblasts, and dendritic cells. In addition, synovial fibroblasts (SFBs) can secrete collagen, fibronectin, osteonectin (ON), and hyaluronic acid (5). It has also been reported that SFBs can generate multiple cytokines, involving osteoprotegerin (OPG) and receptor activator of nuclear factor-?B ligand (RANKL) (6,7). Hence, the SFBs from joints may become the key in OA joint treatment. As a prevalent membrane-bound glycoprotein, alkaline phosphatase (ALP) promotes the hydrolysis of phosphate monoesters at basic pH values (8). ALP is expressed in several osteocytes, including osteoblasts, osteoclasts, and bone marrow stromal cells (9-11). Studies have found that the activity of ALP was closely associated with the bone formation (12), mineral bone disorder (13), and osteogenic differentiation (14). Although ALP is expressed in many mammalian tissues and has been studied for several years, it is still little known. Moreover, regulatory mechanisms of ALP in the ossification of SFBs in OA are still little known to us.