Proliferative Activity and Cholesterol Ester Metabolism in Primary Culture of Human Pterygium Fibroblasts

Purpose: There is now increasing evidence that pterygium is a tumor-like tissue, and that cell growth, as well as DNA replication, is closely linked to cholesterol ester metabolism. Therefore, in the present study, primary cultures of human pterygium fibroblasts in vitro were utilized to investigate a possible correlation between cell growth and cholesterol ester metabolism in pterygial formation. Methods: Primary cultures of pterygium and normal conjunctiva fibroblasts were obtained from patients classified above grade 3 using micro-dissection surgery and from healthy donors, respectively. Expression of p53 and Ki-67 oncogenes was evaluated by immunostaining techniques. Growth kinetic studies were evaluated by growth curve, and 3H-thymidine incorporation. Cholesterol esterification was evaluated by 14C- oleate incorporated into cholesterol esters. Results: Pterygium fibroblasts revealed an increased expression of P53 and Ki-67 compared to normal cells. In addition they grow at faster rate than normal cells. In pterygium fibroblasts, cholesterol esterification increased as cells progressed from resting to proliferating phase. These results provide evidence that cholesterol esterification “per se” may be a limiting factor in determining pterygium cell cycle progression. These conclusions are consistent with the fact that, when fibroblasts are treated with potent inhibitors of cell growth such as pioglitazone and everolimus, the reduction of DNA synthesis caused by the drugs is accompanied by an extensive decrease of cholesterol esterification. Conclusions: This study indicates that pterygium has an altered metabolism of cholesterol esters, and thus that cholesterol esterification could be a potential pharmacological target for prevention and treatment of pterygium.