TY - JOUR T1 - Do Changing Toll-like Receptor Profiles in Different Layers and Grades of Osteoarthritis Cartilage Reflect Disease Severity? JF - The Journal of Rheumatology JO - J Rheumatol DO - 10.3899/jrheum.121159 SP - jrheum.121159 AU - Gonçalo Barreto AU - Tarvo Sillat AU - Antti Soininen AU - Pekka Ylinen AU - Abdelhakim Salem AU - Yrjö T. Konttinen AU - Ahmed Al-Samadi AU - Dan C.E. Nordström Y1 - 2013/03/15 UR - http://www.jrheum.org/content/early/2013/03/13/jrheum.121159.abstract N2 - Objective Cartilage degeneration in osteoarthritis (OA) leads to release of potential danger signals. The aim of our study was to profile OA cartilage for the Toll-like receptor (TLR) danger signal receptors. Methods Osteochondral cylinders from total knee replacements were graded using OA Research Society International score and stained for proteoglycans, collagenase-cleaved type II collagen, and TLR 1–10, which were analyzed histomorphometrically. Results Grade 1 OA lesions contained 22%–55% TLR 1–9-positive cells in the surface zone, depending on the TLR type. In Grade 2 TLR, immunoreactivity was 60%–100% (p < 0.01) and it was even higher in Grades 3 and 4 (p < 0.01 vs Grade 1). TLR-positive cells in Grade 1 middle zone were low, 0–19.9%, but were 5.1%–32.7% in Grade 2 (p < 0.01) and 34%–83% in Grades 3–4 samples (p < 0.001). TLR values in Grade 5 were low (14.3%–28.7%; p < 0.001). In Grades 3–4 OA, cartilage matrix stained strongly for TLR. In Grade 1, COL2-3/4M was restricted to chondrocytes, but was increasingly seen in matrix upon progress of OA to Grade 4, and then declined. Conclusion Cells in the gliding surface zone are fully equipped with TLR in mild OA. Their proportion increases and extends to the middle or even the deep zone, reflecting OA progression. COL2A-3/4M staining suggests Endo180-mediated intake for intralysosomal degradation by cathepsins in Grade 1, but in higher grades this chondrocyte-mediated clearance fails and the matrix demonstrates extensive collagenase-induced damage. Detached and/or partially degraded matrix components can then act as endogenous danger signals (damage-associated molecular patterns or DAMP) and stimulate increasingly TLR-equipped chondrocytes to inflammation. At the peak inflammatory response, soluble TLR may exert negative feedback, explaining in part the low TLR levels in Grade 5 OA. ER -