DNA damage in human pterygium: One-shot multiple targets

PURPOSE Little is known about DNA damage in human pterygium, and no data about DNA damage involvement as a potential angiogenic factor are available. We studied, with immunohistochemistry, the presence and localization of thymine dimers in the epithelial and stromal components of the human primary pterygium and its recurrences with a special emphasis on the vascular network and its interactions with the p53 tumor suppressor gene protein. METHODS Thirty-five primary human pterygium, three recurrences, and three normal bulbar conjunctiva were included in the present study. Formalin-fixed, paraffin-embedded tissues were submitted for immunohistochemical analysis with antithymine dimers and p53 antibodies. Thymine dimer and p53 nuclear staining was assessed in the epithelial and stromal components of pterygial tissues and normal counterparts. RESULTS Thymine dimers were present in the epithelial and stromal components of human pterygium and its recurrences. The thymine dimers were detected in the epithelial component of the human pterygium with a higher density and intensity in the basal layer of the epithelium. Small blood vessels' endothelial cells showed positive reaction for antithymine dimer antibodies together with isolated positive expression found in the nuclei of perivascular cells. For the recurrent pterygium, dimer expression was found only in the subepithelial fibrovascular layer components and in scattered cells from the basal layer of the epithelium. P53 expression was positive in 38.5% of the cases in the epithelial compartment, and in two cases, scattered p53 positive endothelial, fibroblast-like, and perivascular cells were detected in the fibrovascular compartment. CONCLUSIONS Thymine dimers in human pterygium and its recurrences suggest that DNA damage is involved not only in pterygium epithelial and fibrous proliferation but also in angiogenesis and lymphangiogenesis from this ocular lesion in a still incomplete elucidated pathogenic mechanism.