HIF1α and HIF2α immunoreactivity in epithelial tissue of primary and recurrent pterygium by immunohistochemical analysis

PURPOSE: Hypoxia-inducible factors (HIFs) are considered to play a significant role in the pathogenesis of pterygium. The aim of this study was to investigate the relative expression or immunoreactivity of HIF1α and HIF2α in the epithelium of primary pterygium, recurrences and healthy conjunctiva. METHODS: Immunohistochemical staining was performed with antibodies against HIF1α and HIF2α, respectively, on 55/84 primary pterygium specimens, 6/28 recurrences and 20/20 control tissues (healthy conjunctiva). RESULTS: Immunohistochemical staining revealed lower epithelial immunoreactivity of HIF1α and HIF2α in both primary pterygium (11% and 38%) and recurrences (18% and 21%) when compared to healthy conjunctival tissue (46% and 66%). Differences between immunoreactivity of HIF1α and of HIF2α in primary pterygium and controls were each highly significant (p < .001). Within the group of primary pterygium, epithelial immunoreactivity of HIF2α (38%) was significantly higher than that of HIF1α (11%). In recurrent pterygium and healthy conjunctiva, immunoreactivity levels of HIF2α were higher than those of HIF1α as well; however, differences between both isoforms were not significant. CONCLUSION: Our study shows evidence that the higher expressed epithelial HIF2α, rather than HIF1α, and the balance between both HIF isoforms might be relevant factors associated with pathogenesis of primary pterygium. Modulation of HIF2α levels and activity may thus offer a new therapeutic approach to the treatment of advancing pterygium where the initial stage with its HIF1-peak has already passed.