Tropoelastin and Fibulin Overexpression in the Subepithelial Connective Tissue of Human Pterygium

Purpose: To evaluate possible changes in the collagen and elastic components of the subepithelial connective tissue of human pterygium. Design: Immunohistochemical study. Methods: Immunohistochemical staining using antitropoelastin, anti-fibulin-2, and anti-fibulin-3 antibodies was performed in 10 normal conjunctival and 20 pterygium specimens. Masson trichome staining also was performed to study subepithelial connective tissue. Sirius red staining was used to identify collagen type I and III components. Tropoelastin, fibulin-2, and fibulin-3 messenger ribonucleic acid (mRNA) expressions were analyzed in 9 conjunctival and 12 pterygium specimens by quantitative real-time polymerase chain reaction assay. Results: The subepithelial connective tissue and vessels were more predominant in pterygium compared with the normal conjunctival tissue. Amorphous subepithelial zones were observed in the areas of the pterygium tissue, but not in normal conjunctiva. Increased tropoelastin staining was seen in the pterygium tissue with areas of degenerative changes or immature formation of elastic fibers, as well an increase in tropoelastin mRNA, in contrast with fibulin-2 and fibulin-3 messenger levels. Fibulin-2 and fibulin-3 expression was colocalized in the subepithelial connective tissue and was distributed along blood and lymphatic vessels. Collagen type III, an immature form of collagen, was increased in the pathologic samples in association with a tissue remodeling process. Conclusions: Elastin metabolism is dysregulated in the pathogenesis of human pterygium with tropoelastin, fibulin-2, and fibulin-3 overexpression in the subepithelial connective tissue. [ABSTRACT FROM AUTHOR]