Experimental protocol and histological analysis of lung tissues from ApoA1 transgenic mice.

<p>(<i>A)</i> Silica was administered via the trachea to ApoA1 transgenic mice (6 to 8 weeks old) on day 0. The mice were given drinking water containing doxycycline to induce hApoA1 overexpression beginning on day 7 (ApoA1_D7 group) or 15 (ApoA1_D15 group) and continuing throughout the experiment. A third group of silica-treated transgenic mice, which received drinking water with no doxycycline during the experiment (Silica group), were sacrificed 7, 15, or 30 days after silica administration. The ApoA1_D7 and D15 mice were sacrificed 30 days after silica administration. (<i>B)</i> Hematoxylin and eosin staining of lung sections from the transgenic mice following silica administration and doxycycline treatment on day 7 (ApoA1_D7) or 15 (ApoA1_D15), and in those that received no doxycycline treatment (Silica group). Silica group D7, D15, and D30 correspond to mice sacrificed 7 (D7), 15 (D15), or 30 days (D30) after silica administration, respectively. Scale bar = 100 µm. (<i>C)</i> Quantification of the area occupied by silicotic nodules in the lung (<i>n</i> = 8/group). **<i>p<</i>0.01 compared with the Silica group (D30). (<i>D)</i> Polarizing light microscopic analysis showed silica particles in the alveolar space in the lungs of the Silica, ApoA1_D7, and ApoA1_D15 group mice. Scale bar = 20 µm. (<i>E)</i> Numbers of silica particles were observed at ×100 magnification using polarizing microscopy, and the number of silica particles in 20 fields per lung was counted (<i>n</i> = 8 mice/group).