Under–expression of endothelin 1 RNA in pterygium blood vessels may be related to pterygium pathogenesis

Abstract

Abstract: : Purpose:To evaluate the role of endothelin 1 (ET1) in the pathogenesis of pterygium by comparing the levels of ET1 and endothelin converting enzyme 1 (ECE1) between pterygium and autologous conjunctival tissues. Methods:All procedures were approved by an IRB, and informed consent obtained. In a prospective study, 7 pairs of pterygia and superior bulbar conjunctival tissues taken from the same eyes during a pterygium surgery with free conjunctival autograft transplantation were immediately put in liquid nitrous (–196°C) and later stored at –80°C. Reverse transcriptase polymerase chain reaction (RT–PCR) process was then applied to quantify the levels of ET1, ECE1, and platelet endothelial cell adhesion molecule–1 (PECAM1, a marker of blood vessels density). Total RNA was extracted from the tissues and was later converted to complementary DNA (cDNA). cDNA was multiplied using PCR with the specific primers for ET1, ECE1, PECAM1 and GPDH (house keeping gene, which serves as a reference for the DNA quantity). The DNA product was put on an agarose gel for electrophoresis and each band was read for intensity. ET1, ECE1 and PECAM1 bands intensity were divided by that of the GPDH. Paired t tests were used to compare between the ratios of ET1/GPDH, ECE1/GPDH and PECAM1/GPDH in the pterygia and conjunctival tissues. P<0.05 was considered statistically significant. Results:ET1/GPDH, ECE1/GPDH and PECAM1/GPDH ratios were 1.15± 0.1 (mean ± standard error), 1.54 ± 0.1, and 2.7 ± 0.22 in the pterygia tissues, as compared to 1.32 ± 0.045, 1.33 ± 0.13 and 1.15 ± 0.06 in the conjunctival tissues, respectively. While no differences were found in the ratios of ET1/GPDH and ECE1/GPDH between pterygia and conjunctival tissues (P>0.1), PECAM1/GPDH ratio was 2.35 times greater in the pterygia as compared to the conjunctivas (P<0.01). Conclusions:Since endothelial cells are the main producers of ET1 and ECE1, these findings suggest that the concentrations of ET1 and ECE1 RNA in pterygium blood vessels are significantly lower than those in the vessels of the conjunctiva. Further studies are needed.

Keywords: Pterygium • conjunctiva • cornea: basic science