Cyclooxygenase-2-expressing macrophages in human pterygium co-express vascular endothelial growth factor

PURPOSE To evaluate cyclooxygenase-2 (COX-2) expression and to characterize COX-2-expressing stromal cells in human pterygium. METHODS Primary pterygium tissue of Korean patients (eight males and nine females) was analyzed. The clinical characteristics were classified, and immunohistochemical staining using primary antibodies against cyclooxygenease-2, vascular endothelial growth factor-A, cluster of differentiation (CD)68, CD3, CD20, and leukocyte common antigen was performed. RESULTS COX-2 expression was detected in all pterygium tissues evaluated (17 primary pterygia). Diffuse expression of COX-2 in the epithelial layer was observed in nine samples. Infiltration of strongly positive COX-2 cells into the epithelial layer was a more common observation than diffuse epithelial COX-2 expression. Scattered COX-2-expressing cells in the stromal layer were found in all samples. Some COX-2-positive cells were found within microvessels. In addition to stromal COX-2-expressing cells, a few vascular endothelial cells strongly expressed COX-2; however most of the vessels were negative for COX-2 expression. Stromal COX-2-expressing cells were positive for the macrophage marker CD68 and co-expressed vascular endothelial growth factor. COX-2 expression in normal conjunctiva was not observed in seven control samples. CONCLUSIONS These COX-2- and vascular endothelial growth factor-expressing macrophages may have relevance to the pathogenesis of pterygium.