Fig. 1

Time and treatment-dependent phagocytosis of monosodium urate monohydrate (MSU) crystals by differentiated human THP-1 macrophages using flow cytometry and impact of recombinant human proteoglycan-4 (rhPRG4) or bovine submaxillary mucin (BSM) treatments following 2 and 4-h incubations. Quantitative determination of MSU phagocytosis was performed using the percentage of cells in the P2 region of interest. Data represent the mean ± S.D. of four independent experiments. *p < 0.001; **p < 0.01; ***p < 0.05. a Representative flow cytometry scatterplot of untreated human THP-1 macrophages. b Representative flow cytometry scatterplot of MSU-treated THP-1 macrophages for 2 h. c Representative flow cytometry scatterplot of MSU + rhPRG4 (100 μg/ml)-treated THP-1 macrophages for 2 h. d Representative flow cytometry scatterplot of MSU + BSM (25 μg/ml)-treated THP-1 macrophages for 2 h. e Representative flow cytometry scatterplot of MSU-treated THP-1 macrophages for 4 h. f Representative flow cytometry scatterplot of MSU + rhPRG4 (100 μg/ml)-treated THP-1 macrophages for 4 h. g Representative flow cytometry scatterplot of MSU + BSM (25 μg/ml)-treated THP-1 macrophages for 4 h. h Representative flow cytometry scatterplot of rhPRG4 (100 μg/ml)-treated THP-1 macrophages for 4 h. i Representative flow cytometry scatterplot of BSM (25 μg/ml)-treated THP-1 macrophages for 4 h. j Phagocytosis of MSU crystals by THP-1 macrophages was higher in following 4-h incubation compared to 2-h incubation. k rhPRG4 treatment reduced MSU phagocytosis by THP-1 macrophages at 4 h compared to BSM