Sperm immunization and rat spermatogenesis: Dysfunctional blood-testis barrier and perturbed Sertoli cell cytoskeleton

Abstract

Background: Male infertility may be due in part to autoimmune orchitis. Experimental models of autoimmune orchitis have yielded valuable information for understanding the underlying pathogenesis. However, previous rodent models show progressive inflammatory cell infiltration, thus differing from human cases. Objective: We have established an immunization procedure that induces defective spermatogenesis in rats. Here, we examined the affected testes to clarify the pathogenetic mechanism responsible. Materials and methods: Male rats received two subcutaneous injections of spermatozoa in LPS-supplemented oil-based adjuvant. The testes were collected when atrophy was detected by palpation in order to explore the acute phase of the defect. The blood-testis barrier (BTB) permeability was examined in a biotin tracer experiment. Testes were examined immunohistochemically using antibodies against TNFα+ and ED1 (a macrophage marker) to detect inflammatory cells. Antibodies against proteins related to tight and gap junctions, desmosomes, and the Sertoli cell cytoskeleton were also employed. The expression of junction-related molecules and vimentin was also examined by Western blotting and RT-PCR. Results: Immunohistochemistry revealed TNFα+ and ED1+ cells scattered in the interstitium. TNFα+ cells, but not ED1+ macrophages, were associated with seminiferous tubules in the affected testis. The tracer experiment demonstrated dysfunction of the BTB. Immunohistochemistry revealed delocalization of claudin 11 and tight junction protein 1. Positive immunoreactivity for connexin 43 (a major gap junction protein) and desmoglein 2 (a major desmosome protein) was reduced, probably resulting in germ cell exfoliation. F-actin and vimentin showed aberrant distribution in the seminiferous epithelium, and expression of vimentin was upregulated in the affected testis. Conclusion: The observed pathological characteristics demonstrate how inflammatory cells influence Sertoli cells, leading to impaired spermatogenesis, and suggest that this sperm immunization method provides a new rat model of autoimmune orchitis.