The expression of TNFα-stimulating gene (TSG)-6 in mesenchymal stem cells (MSCs) injected into rats intravenously. A. The expressions of TSG-6 in MSCs accumulated in the lung and the spleen. A1. The majority of MSCs accumulated in the lung expressed TSG-6 within 12 hours, as observed by immunofluorescence microscopy. Red symbolizes red fluorescent protein (RFP); Green symbolizes TSG-6. Magnification: × 600, × 1800. A2. The majority of MSCs accumulated in the spleen did not express TSG-6, as observed by immunofluorescence microscopy. Red symbolizes RFP; Green symbolizes TSG-6. Magnification: × 600, × 1800. B. The serum TSG-6 concentration was evaluated by enzyme-linked immunosorbent assay (ELISA). Serum TSG-6 level was increased at 4 hours after intravenous injection of MSCs, compared with the medium-injected group. There was no difference between the group injected with MSCs intraperitoneally and the medium-injected group. Three independent samples were placed in three replicate wells. * compared with the medium-injected group, P <0.05; # compared with the normal group, P <0.05. TNFα, tumor necrosis factor α.