Uptake of acetylated low density lipoprotein (ac-LDL) by synovial cells.

Acetylated low dcnstity lipoprotein (ac-LDL) is known to be incorporated into monocyte/macrophages. We examined thc uptake of fluorescence-labeled ac-LDL as well as the surface expression of CD14 using flow cytometry, in order to identify macrophage-like type A synoviocytes in the synovium of patients with rheumatoid arthritis (RA) (n = 15) and osteoarthritis (OA) (n = 5). The mcan (±SD) percentage of ac-LDL uptake cells in RA synoviocytes (38.3±19.9%) was relatively higher than that in OA synoviocytes (16.6±8.7%) (p < 0.05). Also the proportion of ac-LDL incorporating cells paralleled, but was higher than, that of CD14 positive cells (r = 0.91, p < 0.001).This method is helpful in determining macrophage-like type A synoviocytes, and the presence of CD14-negativc macrophage-like synoviocytes has been revealed.