GE were fixed in 4% paraformaldehyde and processed for paraffin embedment. After rehydration, tissue sections (5 μm) were stained with hematoxylin and eosin (H&E) for histological examination or processed for immunohistochemistry (IHC) to study expression of specific proteins. For IHC, after antigen retrieval, sections were incubated for 1 h with mouse antibodies against human involucrin (Novocastra), K10 (Santa Cruz Biotechnology), K13 (Monosan), vimentin (Dako), or Ki-67 (Dako) as previously described.3 (link),4 (link) Collagen type IV (Monosan) and laminin 5 (Dako) IHC were performed on cryosections without antigen retrieval. Hereafter, the sections were washed in PBS and incubated for 30 min with Envision (Dako), except for K13, which was incubated with PowerVision Poly-HRP (Leica Biosystems) for one hour. Next, the sections were incubated with AEC substrate for 10 minutes followed by hematoxylin staining. The microscopic slides were visualized and recorded with a Nikon Eclipse 80i. Contrast enhancement and quantification of reepithelialization on H&E sections were done with NIS-Elements software (Nikon Instruments Europe B.V.).