Is cadmium chloride-induced inter-sertoli tight junction permeability barrier disruption a suitable in vitro model to study the events of junction disassembly during spermatogenesis in the rat testis?

The events of germ cell movement during spermatogenesis are composed of intermittent phases of junction disassembly and reassembly. Although primary Sertoli cells cultured in vitro can be used to study junction reassembly, an in vitro model to study the events of junction disassembly is still lacking. We have assessed whether the CdCl2-induced inter-Sertoli tight junction (TJ) permeability barrier disruption in vitro can fill this gap. When Sertoli cells (1.2 X 10(6) cells/cm(2)) were cultured on Matrigel-coated bicameral units to allow the assembly of inter-Sertoli TJs, it was manifested by a steady rise in transepithelial electrical resistance across the Sertoli cell epithelia. Exposure of these cells on day 1 (i.e. 24h after their isolation) to CdCl2, at 5-10 muM for 8 h could perturb the inter-Sertoli TJ assembly dose dependently without any apparent cytotoxicity. Likewise, when cells were exposed to CdCl2 (0.1-5 muM) on day 4 for 8 h after inter-Sertoli TJs were already assembled, CdCl2 also perturbed the maintenance of inter-Sertoli TJ permeability barrier dose dependently without signs of cell cytotoxicity. Although the perturbed inter-Sertoli TJs were not capable of resealing even after the removal of CdCl2, the presence of testosterone (T) at 1 x 10(-9) M allowed resealing of the inter-Sertoli TJ barrier after CdCl2 was removed, whereas the presence of 2 x 10(-7) M testosterone even protected Sertoli cells from CdCl2-induced damage. More important, the reassembly of inter-Sertoli TJs after CdCl2-induced TJ disruption was accompanied by changes in cellular gene expression of occludin and urokinase plasminogen activator, which mimicked their patterns during inter-Sertoli TJ assembly in vitro without CdCl2 treatment. Based on these results, it is apparent that CdCl2-induced inter-Sertoli TJ disassembly is a potential in vitro model to study the events of junction disassembly.