In vivo biodistribution and kinetics of siRNA lipoplexes after single systemic administration. Arthritic DBA/1 mice were injected intravenously with 10 μg Cy3-siRNA formulated with the cationic liposome, RPR209120/DOPE, and a DNA carrier, as described in “siRNA lipoplexes treatment.” As controls, mice were injected with a nonfluorescent control siRNA (siCT). Tissue biodistribution and mononuclear cell uptake of the Cy3-siRNAs was evaluated by flow cytometry from 4 hours to day 6 after injection using anti-CD11b (A-B), -CD11c (C-D), -B220, -CD4 (E), or anti-CD146 mAbs (F). Representative dot plots showing Cy3-positive cells for the indicated phenotypic markers and organs are shown from CT siRNA- (left panels) or Cy3-siRNA- (right panels) lipoplex-injected mice at day 2 after administration. (B-D) Histograms show percentages of Cy3-siRNA uptake within the gated CD11b (B) and CD11c (D) positive cells from the indicated time points. Data are representative of 2 independent experiments, with 3 mice enrolled in each group.