... humanchondrocytes and that the levels are upregulated by the proin-flammatory cytokines IL-1β and TNF -α, an effect previouslyobserved on chondrocytes by Xiang and colleagues [12] and on other cell types ... study design, acquisition of data, analysis and interpretation of data, statistical analysis, and manuscriptpreparation. NA participated in acquisition of data, analysis and interpretation of ... analysis, and manuscriptpreparation. JMP and JPP participated in study design, analy-sis and interpretation of data, and manuscript preparation. NDparticipated in study design and in analysis...