Overexpression of urokinase-type plasminogen activator in pterygia and pterygium fibroblasts

PURPOSE Urokinase-type plasminogen activator (uPA) is a protease involved in tissue remodeling and cell migration. Little is known about the expression of uPA in pterygium. The purpose of this study was to investigate the expression of uPA mRNA and activities in various stages of surgically excised pterygia specimens and cultured pterygium fibroblasts and to compare them with normal conjunctival tissues and fibroblasts. METHODS The expression of uPA mRNA and activity in 15 pterygium tissues and cultured fibroblasts from pterygium were measured using quantitative RT-PCR and zymography. Five normal conjunctiva specimens and cultured conjunctival fibroblasts were tested as the controls. RESULTS The expression of uPA mRNA and activities in pterygia and pterygium fibroblasts were significantly greater than those of the normal samples (p<0.05) and were closely related to the progression of pterygium. The amounts of uPA mRNA and activities in early, moderate, and advanced pterygia were 100%, 208%, and 311% and 100%, 157%, and 280% of the early stage specimens, respectively. The amounts of uPA mRNA and the activities in cultured pterygium fibroblasts isolated from early, moderate, and advanced pterygium specimens were 100%, 219%, and 457% and 100%, 198% and 355% of early stage fibroblasts, respectively. CONCLUSIONS Overexpression of uPA was present in pterygium and their fibroblasts. The expression of uPA by pterygium increased significantly following the progression of the pterygium. The increased expression of uPA may covert plasminogen to plasmin, degrade extracellular matrixes, stimulate cell migration, induce angiogenesis, and plays an important role in the development and progression of pterygium.