Inhibition of the urokinase-type plasminogen activator by triplex-forming oligonucleotides in rat Sertoli cells: a new contraceptive alternative?

Hormonal Regulation of Urokinase- and Tissue-Type Plasminogen Activator in Mouse Sertoli Cells

A role for the plasminogen activator (PA) system has been postulated in mammalian gonads, considering the complex process of morphogenesis these organs undergo during their development. Our results show that mouse Sertoli cells under basal conditions produce both types of PA, tissue-type PA (tPA) and urokinase-type PA (uPA), and hormonal treatments increase the production of both enzymes. The increased enzyme secretion does not correlate with a parallel increase in their mRNAs. However, the proteolytic activity results from a balance between enzyme activity and inhibitors. Hormonal stimulation decreased the expression of the inhibitor PAI-1, suggesting that the increase in proteolytic activity might depend on the decreased production of PAI-1. The expression of the two enzymes and their inhibitor depends on the seminiferous epithelium stage. We observed higher uPA mRNA levels at stages VII-VIII and IX-XII, tPA peaks at stages VII-VIII, and PAI-1 mRNA levels decreased at stages VII-VIII and IX-XII. The testes from mice lacking the uPA gene (uPA-/-) presented statistically smaller sizes and weights. Histological analysis of uPA-/-animals showed tubular morphology defects and atypical residual bodies (RB), suggesting a defect in Sertoli cell phagocytosis. Moreover, we show lower sperm concentration and motility in uPA-/- mice. These data suggested an effective deficiency of testicular development in the absence of uPA.

Hepatocyte growth factor (HGF) regulates blood-testis barrier (BTB) in adult rats

We have studied the effects of HGF on BTB dynamics in adult rats. We demonstrate that, at stages VII-VIII of the epithelium wave when germ cells traverse the BTB, HGF reduces the levels of occludin and influences its distribution pattern and assembling. Moreover, we report that, at stages VII-VIII, HGF significantly increases the amount of active TGF-β and the amount of uPA present in the tubules. For the first time we report that, in the same stages, HGF reduces the amount of actin present in the BTB region, in which occludin levels are highest, and modifies the morphology of the actin cytoskeleton network. At the level of maximal intensity of occludin fluorescence, we report that HGF also modifies the colocalization of occludin and actin. Lastly, we demonstrate that HGF is maximally expressed at stages VII-VIII, whereas its levels fall in the subsequent stages.

Hepatocyte growth factor modulates Sertoli-Sertoli tight junction dynamics

In mammalian testes Sertoli cells form tight junctions whose function is fundamental for the maintenance of a normal spermatogenesis. Hepatocyte growth factor (HGF) is a cytokine influencing the cellular tight junctions either in normal or in tumor cells. We have previously demonstrated that HGF is expressed in the rat testis and influences many functional activities of somatic and germ cells. We now report that HGF decreases the levels of testicular occludin and influences the position of the molecule in the tight junctions as demonstrated by confocal microscopy analysis. In fact in the presence of the factor occludin was mainly localized in the suprabasal region of the tubules whereas in its absence occludin was prevalently localized in the basal region. Occludin production is known to be regulated by different cytokines including TGFbeta. We have investigated the role of HGF in the regulation of the levels of TGFbeta and we report that HGF significantly increases the amount of the active fraction of the factor without affecting the amount of the total TGFbeta. Urokinase type plasminogen activator (uPA) is closely related with the tight junctions and is one of the molecules able to activate the inactive TGF-beta. We found that HGF significantly increases the amount of uPA present in the testis suggesting that HGF regulates the amount of active TGFbeta via uPA levels. In conclusion we report that in the testis HGF regulates Sertoli-Sertoli tight junctions inducing a reduction and redistribution of occludin possibly modulating the levels of uPA and active TGFbeta.