Phospholipase D in the human ocular surface and in pterygium

Purpose: Pterygium is a fibro-vascular disease of unknown etiology characterized by proliferation and advancement of tissue onto the cornea. Phospholipase Ds (PLDs) are members of an important class of enzymes involved in inflammation and differentiation. In cultured corneal epithelial cells, these enzymes play a role in wound healing, and in other contexts, they suppress apoptosis and increase cell motility. We aimed to study the presence of PLD subtypes in native ocular surface tissue and pterygium. Methods: This study involved paired control or uninvolved conjunctival and pterygium tissues from 6 patients. Reverse transcription semi quantitative and quantitative polymerase chain reactions were performed to assess transcript levels for PLD1-5 in normal conjunctiva and pterygium tissue. Immunofluorescent staining by using antibodies against PLD1/2 was used to study the expression and tissue distribution. Western blots were performed for protein detection and to confirm the specificity of the antibodies used. Results: PLD1, 2, 3, and 4 transcripts were detected in normal conjunctiva tissue, and types 2, 3, and 4 were upregulated in pterygium. Immunofluorescent staining showed the presence of phospholipase-D1/2 in normal cornea, conjunctival, and pterygial epithelia. In normal cornea and conjunctival epithelia, the expression was mainly localized to the nuclei of the basal and suprabasal epithelial cells, whereas in pterygium, this expression was limited to the cytoplasm and peri-plasma membrane regions. Western blot confirmed the presence of PLD1/2 in proteins extracted from pterygium and conjunctiva tissue. Conclusions: PLD subtypes are present in human ocular surface epithelium. PLD may be involved in pterygium pathogenesis.