Cartilage regeneration after inhibition of endogenously produced IL-6. Cartilage regeneration cultures of three defect (CD) and three osteoarthritic (OA) donors with blockage of endogenous IL-6 with an activity-inhibiting antibody. (a-c) GAG content, GAG release and DNA content after 28 days of culture in IL-6 blocked samples depicted as percent of control samples (mean ± SD); a = P = 0.009. (d) Safranin-O staining of representative CD and OA chondrocyte donors regenerating either without (control; IgG isotype) or with inhibition (anti-IL-6) of endogenous IL-6. Scale bars indicate 50 μm.