Cartilage regeneration with addition of IL-6. Cartilage regeneration cultures of three healthy (H) and three osteoarthritic (OA) donors with addition of rhIL-6 (10 ng/mL) and rhIL-6Rα (25 ng/mL). (a-c) GAG content, GAG release and DNA content of IL-6 supplemented samples depicted as percentage of control samples (mean ± SD); a = P = 0.009, b = P < 0.001. (d) Safranin-O staining of neocartilage generated by chondrocytes from healthy and osteoarthritic donors without or with addition of rhIL-6. Scale bars indicate 50 μm.