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 int ermittent phases of junction disassembly and reassembly. Although primary S ertoli cells cultured in vitro can be used to study junction reassembly, an in vitro model to study the events of junction disassembly is still lackin g. We have assessed whether the CdCl2-induced inter-Sertoli tight junction (TJ) permeability barrier disruption in vitro can fill this gap. When Serto li cells (1.2 X 10(6) cells/cm(2)) were cultured on Matrigel-coated bicamer al units to allow the assembly of inter-Sertoli TJs, it was manifested by a steady rise in transepithelial electrical resistance across the Sertoli ce ll epithelia. Exposure of these cells on day 1 (i.e. 24h after their isolat ion) to CdCl2, at 5-10 muM for 8 h could perturb the inter-Sertoli TJ assem bly dose dependently without any apparent cytotoxicity. Likewise, when cell s were exposed to CdCl2 (0.1-5 muM) on day 4 for 8 h after inter-Sertoli TJ s were already assembled, CdCl2 also perturbed the maintenance of inter-Ser toli TJ permeability barrier dose dependently without signs of cell cytotox icity. Although the perturbed inter-Sertoli TJs were not capable of reseali ng 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 chan ges in cellular gene expression of occludin and urokinase plasminogen activ ator, which mimicked their patterns during inter-Sertoli TJ assembly in vit ro without CdCl2 treatment. Based on these results, it is apparent that CdC l2-induced inter-Sertoli TJ disassembly is a potential in vitro model to st udy the events of junction disassembly.