FIG. 1.

Elastase-treated mice have fibrotic lung damage consistent with COPD. Mice were treated by nonsurgical intratracheal instillation of elastase (see Materials and Methods) and allowed to recover for 21 days posttreatment. Lung tissue samples from euthanized mice receiving vehicle (PBS) (A), elastase (B), or heat-inactivated (HI) elastase (C) were compared by hematoxylin-eosin staining of paraffin sections. COPD-like pulmonary damage was observed for the elastase-treated group that was not observed for either of the control groups. Magnification, ×4 for left panels and ×40 for right panels.