Figure 5: Morphological examination of MSC homing and engraftment in the lungs. Paraffin sections of the lungs, 8 days post intubation with either PBS or PAO1, were immunohistochemically staining for EGFP expression. Panels A & B: Lung sections from the control animals received PBS intra-tracheal intubation and MSC intra-vascular infusion. Panels C-F: Lung sections from the experimental animals received PAO1 intra-tracheal intubation and MSC intra-vascular infusion. The EGFP-positive cells were stained brown (Red arrows). MSCs extravasated out of the blood vessel (C). MSCs engrafted into lung airway epithelia and underwent clonal expansion (D & E). MSCs engrafted into lung alveolar epithelia (F).