Comparable response of ccn1 with ccn2 genes upon arthritis: An in vitro evaluation with a human chondrocytic cell line stimulated by a set of cytokines

In order to mimic the initiation of inflammation, HCS-2/8 cells were treated with tumor necrosis factor (TNF)-α. To induce pro-inflammatory or reparative responses, TGF-β was employed. Effects of an anti-inflammatory glucocorticoid were also evaluated. After stimulation, expression levels of ccn1 and ccn2 were quantitatively analyzed. Surprisingly, not only ccn2, but also ccn1 expression was repressed upon TNF-α stimulation, whereas both mRNAs were uniformly induced by transforming growth factor (TGF)-β and a glucocorticoid.These results describing the same response during the course of inflammation suggest similar and co-operative roles of these 2 ccn family members in the course of arthritis.Osteoarthritis (OA) and rheumatoid arthritis (RA) are most common orthopaedic complexities among aged individuals [1]. Although they may be etiologically distinct each other, both are characterized by progressive destruction of articular cartilage, which is mainly caused by inflammatory stresses [1]. The most major problem in the therapeutics of these joint diseases is the difficulty in regenerating damaged articular cartilage. It is widely recognized that even a defect of 2 mm in diameter in normal articular cartilage may not be repaired naturally [2,3]. Therefore, cartilage regeneration is one of the most preferred subjects for the investigators in medical research field.In our previous report, we for the first time clarified that CCN2/connective tissue growth factor (CTGF) was capable of regenerating full-thickness defect in articular cartilage and promoted the repair of damaged cartilage in an OA model in vivo [2]. Also, expression of ccn2 in OA cases was reported [3]. As such, it is now quite clear that CCN2 is involved in inflammatory response and repair process of articular cartilage during arthritis. Therefore, it is of critical importance to investigate the regulation of ccn2 expression along with the course of joint inflammation.The CCN family is a novel group of pro