Density of cells positive for typical clock proteins. A) Density of clock protein - positive cells in synovial tissue of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). *P < 0.05 vs. RA; aP < 0.10 vs. RA. B) Density of cells positive for BMAL-1 (left panel) and Period 1 (Per1, right panel) over time. Synovial tissue was obtained from healthy subjects (HS, green) and patients with OA (black) and RA (red) at different time points during the day (time of operation start was grouped at 8:00 am, 11:00 am, 1:00 pm and 3:00 pm). Symbols in A) and B) indicate the mean value of cellular density of 17 randomly chosen high power fields from stained tissue of one individual patient. For example, this staining included n = 12 healthy subjects at time point 8:00 am. The correlation coefficient of cubic regression is given.