Expression of Beta–Microseminoprotein in Pterygium

Abstract

Abstract: : Purpose: Beta microseminoprotein (PSP94), a prostate associated protein, has been shown to be up–regulated in both pterygium tissues and the tears of pterygium patients. In this study, we have examined PSP94 expression by real time PCR, Western analysis and immunohistochemistry. Methods:Pterygium and conjunctiva (normal control) tissues were snap frozen in liquid nitrogen immediately upon surgical excision from patients. Total RNA and protein were extracted for both PCR and Western blotting procedures. Pterygium samples and their matched conjunctiva samples for immunohistochemistry were embedded in OCT medium and sectioned longitudinally at 5µm. Custom made rabbit polyclonal antibodies against PSP94 and cytokeratin 4 (Acris Antibodies GmbH) were used in the immunohistochemistry experiments. Results:Both real time PCR and Western blot analysis showed that PSP94 was up–regulated in pterygium. Immunohistochemical staining showed a preferential expression of PSP94 in the pterygium epithelium. Interestingly, the expression of PSP94 was higher in the posterior part of the pterygium closer to the bulbar conjunctiva compared to the anterior epithelium growing over the cornea. Further investigation showed that the pterygium epithelium of the anterior tip, growing over the cornea, stained negative for cytokeratin–4. Conclusions: Expression of PSP94 in messenger RNA level as well as the protein level was shown to be up–regulated in the pterygium epithelium compared to the conjunctival epithelium. Cytokeratin 4, which is expressed in normal conjunctival epithelium and mature corneal epithelium, was negatively stained in pterygium anterior epithelium. This result indicates that the anterior epithelium had lost its conjunctival epithelial characteristics. The unique localization of PSP94 in pterygium epithelium remains to be elucidated.

Keywords: Pterygium • immunohistochemistry