Histology of tracheal tissues before and following culture ex vivo. (A-D) H&E stain demonstrating intact ciliated epithelium over a 48 h incubation period; little change in tissue integrity is seen at 48 h (D). (E-H) AB/PAS stain showing the presence of mucus-producing goblet cells; strong staining is evident in pre-cultured tissue (E), while a progressive decrease in staining is seen following 48 h of culture (H). (I-L) Caspase-3 immunostained sections demonstrating apoptosis; positive staining cells present in the epithelium and underlying tissue. Both cytoplasmic and nuclear staining is seen, with more intense nuclear staining evident at 48 h (L) (original magnification ×200).