Expression of Fas in osteoarthritis (OA) and control tenocytes. (a) Expression of Fas mRNA was analyzed by quantitative real-time PCR using the TaqMan® system (Applied Biosystems, Weiterstadt, Germany). Expression of Fas mRNA was seen in OA tenocytes (n = 5) and in control cells (n = 5), but expression levels were 7.2-fold higher in OA tenocytes than in control cells. (b) Expression levels of soluble Fas (sFas) in the cell culture supernatants of OA tenocytes (n = 5) and control cells (n = 5) as determined by ELISA. OA tenocytes showed 1.6-fold lower levels of sFas in their cell culture supernatants than did control tenocytes. Stimulation with tumour necrosis factor (TNF)-α over 24 hours resulted in a dose dependent upregulation of sFas in all tenocytes, but higher expression of sFas in the control tenocytes was seen consistently with all TNF-α concentrations. *P < 0.05, versus control.