Inflammatory signs in repeatedly injected animals. In all parameters assessed, only those animals receiving multiple whole blood injections showed significant signs of inflammation. Joint swelling was significantly increased in this group when compared to all other groups (A). Arrows indicate the injections. Histopathological signs of chronic inflammation were likewise significantly increased in whole blood injected animals, but not those receiving blood compartments (B), while signs for joint destruction only showed a trend (C). Numerically, C-reactive protein levels were highest in whole blood injected animals, yet here, no statistical difference could be obtained between groups (D). Representative pictures of knee joint histology from the different groups are displayed in (E) to (H). An animal that received eight saline injections is shown in (E). Here, no inflammatory response is obvious. A specimen from a whole blood injected animal is displayed in (F), showing signs of synovitis and inflammation in the surrounding tissues as well as blood cells in the joint space. Plasma-injected animals (G) and those that received cellular compartments are shown in (H), revealing similar, yet milder pathology compared to whole blood. Pictures in the lower panel are magnifications of the indicated inset in the upper panel. Arrows indicate the (mild) inflammatory changes and intra-articular blood cells. Scale bars are 500 μm. Data are presented as means ± SEM. Data of those animals receiving saline in lithium-heparin which were included in the statistical analysis are not displayed in the figure for clarity.* P <0.05; ** P <0.01; *** P <0.001. BL, baseline; SEM, standard error of the mean; WB, whole blood.
Boettger et al. Arthritis Research & Therapy 2013 15:R148 doi:10.1186/ar4331