Total nuclear histone deacetylase (HDAC) and histone deacetylase (HAT) activity in synovial tissues. (a) Nuclear HDAC activity in synovial tissues that were obtained from rheumatoid arthritis (RA, n = 14) patients was significantly increased compared to that from normal controls (n = 3) and osteoarthritis (OA, n = 12). In the box (interquartile range, IQR) and whisker (maximum and minimum) plots, the horizontal line inside the box denoted median and the filled circles denote outliers outside IQR ± 1.5 × IQR. * = P < 0.05 versus normal controls, ** = P < 0.05 versus OA. (b) Nuclear HAT activity was measured in synovial tissues that were obtained from normal controls (n = 3), OA (n = 5) and RA patients (n = 5). There was no significant difference between normal controls, OA and RA synovial tissues.