Role of Urokinase-type Plasminogen Activator in the Precontact Sperm-egg Communication and Fertility of Mice in vitro

TLDR: UPA could induce SC of mice sperm in vitro through the uPAR on its membrane, enhance the capability of egg inducing SC, and promote spermatozoa to fertilize eggs, and enhance the fertility success correspondingly.

Abstract: Objective To explore the role of urokinase-type plasminogen activator(uPA) in precontact sperm-egg communication and fertility of mice in vitro.Methods Firstly, sperm chemotaxis (SC) induced by uPA was assayed by measuring the sperm densities in capillaries with a descending gradient or no gradient of uPA respectively. Secondly, the role of uPAR that exists in sperm plasma membrane in SC was studied by examining the change of sperm density in capillary after incubating spermatozoa with anti-uPAR antibody. Thirdly, SC induced by eggs, which had been treated with uPA, PAI-1 and anti-uPAR beforehand respectively, was assayed to study the role of uPA in PSEC. Lastly, the fertilization capability of spermatozoa treated with uPA was examined by counting the number of fertilized eggs.Results 1)The density of spermatozoa that migrated down the gradient of uPA into the capillary was significantly lower than that into the capillary containing no-gradient uPA. 2) When uPAR of spermatozoa was inhibited by anti-uPAR antibody, the density of spermatozoa that migrated into the capillary with ascending gradient of uPA decreased correspondingly. 3) The density of spermatozoa attracted by eggs, which were treated with uPA beforehand, increased significantly than that of attracted by non-treated eggs. On the contrary, the sperm density decreased correspondingly when the egg was treated with PAI-1. 4) The number of fertilized eggs increased significantly after the spermatozoa used here was treated with uPA beforehand.Conclusion uPA could induce SC of mice sperm in vitro through the uPAR on its membrane, enhance the capability of egg inducing SC, and promote spermatozoa to fertilize eggs. Thus, uPA may act as an attractant in PSEC, increase the chance encounter of spermatozoa and eggs, therefore, enhance the fertility success correspondingly.This study, in some degree, provides an evidence that uPA may be used as a new medicine and diagnostic reagent for male infertility.