Abstract
Purpose: :
Pteryium is known to correlate with cumurative ultraviolet exposure on the corneal limbus. We previously reported epithelial cells at the leading edge of pterygial head lost epithelial characteristics, such as E-cadherin expression, and simultaneously upregulated mesenchymal markers, such as α-smooth muscle actin (SMA) and vimentin (Kato et al, IOVS 2007). This phenomenon is called epithelial-mesenchymal transition (EMT). We speculated that oxidative stress caused by ultraviolet exposure may induce EMT in the pterygial epithelium. Therefore, we investigated whether oxidative stress induces epithelial-mesenchymal transition (EMT) in cultured corneal epithelial cells.
Methods: :
TKE2 cells (mouse corneal epithelial cell line) were harvested in 75 mm2 flasks and cultured in 5% CO2 at 37oC using the defined KSFM medium with or without hydrogen peroxide (H2O2; 10~50 µM). After 7 days, RT-PCR, western blotting for α-SMA, E-cadherin, and immunohistochemistry for α-SMA, E-cadherin, and β-catenin were performed.
Results: :
By phasecontrast microscopy, TKE2 cells revealed enlarged, flattened and fusiform-like elongated contour after 7 days H2O2 stimulation. RT-PCR and western blotting showed upregulated expression of α-SMA in the cells stimulated with H2O2. Immunohistochemistry showed declined membrane staining for E-cadherin and β-catenin and increased staining for α-SMA in the H2O2 stimulated cells.
Conclusions: :
H2O2 caused EMT-like changes in cultured corneal epithelial cells. The present results may indicate that oxidative stress by ultraviolet exposure may cause EMT in the pathogenesis of pterygium.
Keywords: EMT (epithelial mesenchymal transition) • oxidation/oxidative or free radical damage • cornea: epithelium