Abstract: o study the expression and the immunohistochemical location of matrix metalloproteinases-3 (MMP-3), laminin (LN) and collagen Ⅲ(col Ⅲ) in the human pterygium. MethodsPrimary nasal pterygial tissues(15 eyes) and normal human conjunctival tissues(8 eyes) were determined by immunohistochemical staining, using monoclonal and polyconal antibodies specifically against MMP-3, LN and col Ⅲ. The intensity of reaction on individual sections was semiquantitatively graded. Special staining methods, such as Masson and the Van Gieson staining were used to study the distribution of collogen fibers and elastic fibers. ResultsBy HE staining, the subepithelial connective tissues and vessels in the pterygium were more prominent than normal conjunctival tissues. An amorphous subepithelial superficial hyalinized zone and coarse eosinophilic granular materials were observed in the pterygia, but they were not found in normal conjunctival specimens. Coarse fibers were visible only in the deeper subepithelial connective tissues of pterygial samples. With Masson′s staining, the dense staining of collagen fibers was also more prominent in the pterygium than in the subepithelial connective tissues of normal conjunctiva. Abnormal collagen fibers were visible in the deeper sub-epithelial connective tissues of pterygial samples. With Van Gieson staining, abnormal collagen fibers were visible in the deeper subepithelial connective tissues. Dark coarse elastic fibers were found in the abnormal fibers only in the subepithelial deep connective tissues of pinguecula in the pterygia but not in the conjunctiva. With immunohistochemistry staining, MMP-3 was strong in the pterygial epithelium, moderate in fibroblast　and absent from pterygial vascular walls. LN was strongly expressed in the blood vessel wall, moderately in the epithelial basement membrane and absent from the entire stroma. Antibodies against col Ⅲ reacted strongly in the entire pterygial stroma. Conclusions Components of ECM are changed in the pterygium: the sub-epithelial connective tissues and vessels are more prominent in the pterygia than in normal conjunctiva tissues, and abnormal fibers are visible only in the deeper subepithelial connective tissues. This study documents the overexpression of LN and col Ⅲ. They may play roles in cellular adherency, migration and angiogenesis. Also this study documents the overexpression of MMP3 which may degrade ECM in the pathogenesis of the pterygium.

Key words: Pterygium, Extracellular matrix, Matrix metalloproteinases-3, Laminin, Collagen