p21(-/-) fibroblast-like synoviocytes (FLS) exhibit a faster growth rate than wild-type (WT) FLS, while both cell types migrate in a dose-dependent manner to rheumatoid arthritis (RA) synovial fluids (SFs). (a) Equal numbers of WT or p21(-/-) FLS were plated into a 24-well plate and allowed to grow. At various time points, cells were removed and quantified as described in the Materials and methods section. Bars represent the mean of triplicate wells ± standard error (SE). An asterisk indicates a statistically significant difference. (b) WT FLS were tested for their ability to migrate to different dilutions of RA SF. The sum of counts from three high power fields (HPFs) was determined, and bars represent the mean of those sums from quadruplicate wells ± SE. An asterisk indicates a statistically significant increase in chemotaxis relative to background migration to PBS.