| Purpose: Notch signaling pathway plays crucial roles in regulation of cellproliferation, differentiation and cell fate decision in multiple tissues and celltypes. This study was designed to test the effects of enhanced Notch activity oncorneal epithelium homeostasis and wound healing using the transgenic micethat overexpressed an activated Notch1, NICD, in cornea epithelium.Methods: The studies were performed on R26fN1-ICD transgenic micethat carry a NICD cDNA whose expression is prevented by a "Lox-STOP-Lox"cassette. When this transgenic mouse is bred to a mouse strain carrying a Crerecombinase expression cassette driven by a tissue-specific keratin14(K14)promoter, the floxed "STOP" cassette is excised and the NICD is expressed incornea epithelium. The expression level of NICD and its downstream targetgenes, Hes1and Hey1in the transgenic corneal epithelium was examined byqPCR. The phenotypes and morphology of transgenic corneal epithelium werecompared with that of WT controls. The proliferation rate of epithelial cellswas assessed by BrdU incorporation and the differentiation statues wereexamined by K14, p63, K12and ZO-1immunoreactivity at either normaldevelopmental condition or after corneal epithelial debridement. The cornealepithelial response to wound healing was studied by fluorescent stainingmacroscopically and by H&E staining at microscope level at0,6,12,18, and24hours post injury.Results: Although overexpression of NICD in cornea epithelium led toupregulation of its downstream targets, i.e., hes1and hey1, this did not altercorneal epithelial cell proliferation and differentiation. However, woundhealing induced Notch activity and overexpression of NICD promoted cornealepithelial wound healing, which was in agreement with more rapid early proliferation response in NICD transgenic mice than in the wild type controlmice.Conclusions: These findings further demonstrate the functional role ofNotch signaling in corneal epithelium wound healing response.
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