Regulation of inflammatory markers over prolonged culture. Fold change in mRNA expression of inflammatory genes in fibroblast-like synoviocytes (FLS), determined by real-time RT-PCR between passages 2 and 8 (P2 to P8). Expression of mRNA was measured at 16 hr for (a) IL-6, (b) chemokine ligand 2 (CCL-2), (c) vascular cell adhesion molecule 1 (VCAM-1) and (d) intercellular adhesion molecule 1 (ICAM-1). For each gene product data were normalized for levels of the housekeeping gene 18S rRNA and are presented as fold change in expression (± standard error) relative to the P2 control. *P < 0.05 versus passage 2. #P < 0.05 versus passage 3. Results shown are the combined duplicates of two K/BxN FLS.