Fig. 1

Homing of BMSCs to the silica-injured lung. a A diagram of experimental protocol. Rats were monitored using an in vivo imaging system at 1 h, 6 h, 24 h, 3 days, 15 days, and 30 days after transplantation of DiR-BMSCs. b Cytotoxicity of DiR in vitro. Relative cell viabilities of BMSCs were measured after being incubated with various doses DiR for 24 h, 48 h, and 72 h. Up to 5 μg/ml, DiR did not change cell viability. **p < 0.01 compared with 0 μg/ml group. c Whole-body imaging was monitored with the in vivo imaging system. DiR fluorescence intensity reached a peak at 6 h, declined dramatically by day 3, reduced over a long period (at least 15 days), and disappeared by day 30. BMSCs were predominantly distributed to the liver region in the DiR-BMSCs + control group, while many cells were accumulated in the thoracic (lung) region in the DiR-BMSCs + silica group. Scale bar = 5 cm. d, e Quantification of the fluorescence intensity in the whole body and in the lung. Much more cells were accumulated in the thoracic (lung) region in the DiR-BMSCs + silica group compared with the DiR-BMSCs + control group. The data were presented as the means ± SD. **p < 0.01 versus the DiR-BMSCs + control group