Downregulation of c-Myc in pterygium and cultured pterygial cells

Background: The aim of this study was to determine c-Myc expression in pterygial tissue and in cultured fibroblasts and epithelial cells of pterygia, using normal human conjunctival samples as a control. Methods: Expression of c-Myc in pterygium and normal human conjunctiva tissue was examined by immunohistochemical assay and Western blot. Fibroblasts and epithelial cells from primary pterygium and normal human conjunctiva were cultured in medium with or without transforming growth factor beta1 for up to 3 days. c-Myc protein expression was analysed by indirect immunofluorescence. Levels of c-Myc mRNA in fibroblasts were measured by reverse transcription polymerase chain reaction. Results: c-Myc protein expression was reduced in human pterygial tissue compared with normal human conjunctiva in immunohistochemical staining. The decrease was further verified by Western blot analysis. In primary cultured cells c-Myc expression as stained by immunofluorescence was reduced in both pterygial epithelial and fibroblast cells when compared with cultured normal human conjunctiva cells. In addition, compared with cells from normal conjunctiva, reduced levels of c-Myc mRNA were observed in both cultured pterygial epithelial and fibroblast cells. Increased c-Myc expression in pterygial cells, but not in normal conjunctival cells, was found when the cultured cells were treated with transforming growth factor beta1. This increase of c-Myc mRNA appeared to be time and transforming growth factor beta1 dose dependent. Conclusions: c-Myc expression is reduced in pterygium compared with normal conjunctiva. Transforming growth factor beta1 can elevate the downregulated c-Myc in cultured pterygial cells.