Gene Expression of Plasminogen Activator Inhibitor–1 (PAI–1) in Human Ciliary Processes and Determination of PAI–1 in Human Aqueous Humor

Abstract

Abstract: : Purpose: The present study was performed to detect the gene expression encoding for Plasminogen Activator Inhibitor–1 (PAI–1) in human ciliary processes and to determine the activity of PAI–1 in human aqueous humor. Methods: Total mRNA was extracted from human ciliary processes, which were isolated from freshly enucleated human eyes (n=8). Reverse transcribed PAI–1 mRNA was measured by real–time RT–PCR (TaqMan^® PCR). In addition, we determined the concentration of PAI–1 in the supernatants of serum–free cultured human ciliary processes (n=8). To detect PAI–1 in human aqueous humor we analyzed a total of 55 samples of aqueous humor (50–200 µl) obtained from patients undergoing cataract surgery. In 30 samples the activity of PAI–1 was determined by using a specific chromogenic test (Coatest^® PAI–1). On the other hand the total concentration of PAI–1 (n=25) was measured by using an enzyme–linked immunosorbent assay (Zymutest^® PAI–1 Ag). Results: PAI–1 mRNA was localized in human ciliary processes. The PAI–1 concentrations in supernatants of serum–free cultured human ciliary processes ranged from 43.1 to 152.3 ng/ml. The mean of PAI–1 activity in human aqueous humor was 15.88 ± 2.69 AU/ml with a range of 6.5 to 19.0 AU/ml. The quantity of PAI–1 in human aqueous humor ranged from 0.03 to 1.83 ng/ml (mean 0.42 ± 0.47 ng/ml). Conclusions: PAI–1 is a main regulator of the fibrinolytic system. PAI–1 inhibits tissue plasminogen activator and urokinase–type plasminogen activator resulting in reduced plasminogen activity and attenuated fibrinolysis and proteolysis. Our results confirm earlier results in mice and indicate that PAI–1 is also produced by human ciliary processes. The presence of PAI–1 in human aqueous humor indicate that the fibrinolytic system is physiologically found in the anterior segment of the eye. Therefore, stimulation of PAI–1 production may be involved in intraocular inflammation, wound healing processes and increased outflow obstruction.

Keywords: ciliary body • wound healing • aqueous