Mechanism of abnormal elastin gene expression in the pinguecular part of pterygia

Elastodysplasia and elastodystrophy are two known manifestations in the con junctival, ie, pinguecular, part of pterygia, But the mechanisms are still not understood. The purpose of this study is to investigate the mechanism o f enhanced elastin gene expression in fibroblasts from the pinguecular part of pterygia, which is related to abnormal elastic fiber expression in the pinguecular part of pterygia, Elastin in surgical specimens of normal conju nctiva and the pinguecular part of pterygia from age-matched patients was d etected by immunohistochemical staining. Northern hybridization and quantif ication of radiolabeled tropoelastin were performed in conjunctival fibrobl asts cultured under different doses of ultraviolet (UV) B irradiation, and in cultured pinguecular fibroblasts from pterygia In vitro translation was also performed to analyze the tropoelastin production in. rabbit reticulocy te lysate, The level of tropoelastin in reticulolysates from W-treated conj unctival and pinguecular fibroblasts of pterygia was higher than in normal conjunctival fibroblasts, The coding sequence and 3'-untranslated region of tropoelastin mRNAs were amplified by reverse transcription-polymerase chai n reaction, and mutations were checked by DNA sequencing. Immunohistochemic al staining revealed elastin in pinguecular subepithelial connective tissue s of pterygia, but not in normal conjunctiva. Tropoelastin mRNA levels were not elevated in cultured pinguecular or conjunctival fibroblasts with or w ithout ultraviolet B irradiation. However, tropoelastin synthesis was enhan ced in culture medium of pinguecular and UV-irradiated con junctival fibrob lasts, but not in normal conjunctival fibroblasts, Direct DNA sequencing re vealed mutations in the 3'-untranslated region but not in the coding sequen ce of tropoelastin mRNA, in both pinguecular and UV-irradiated conjunctival fibroblasts, The increased expression of tropoelastin in pinguecular and U V-irradiated fibroblasts is not a result of increased levels of steady-stat e mRNA, but is a result of posttranscriptional modification of tropoelastin .