In mammals, the reproductive system and autoimmunity regulate mutual functions. Importantly, systemic
autoimmune diseases are thought to cause
male infertility but the underlying pathological mechanism remains unclear. In this study, the morpho-function of the testes in BXSB/MpJ-Yaa mice was analyzed as a representative mouse model for systemic
autoimmune diseases to investigate the effect of excessive autoimmunity on spermatogenesis. At 12 and 24 weeks of age, BXSB/MpJ-Yaa mice showed
splenomegaly and increased levels of serum
autoantibodies, whereas no controls showed a similar autoimmune condition. In histological analysis, the enlarged lumen of the seminiferous tubules accompanied with scarce spermatozoa in the epididymal ducts were observed in some of the BXSB/MpJ-Yaa and BXSB/MpJ mice but not in C57BL/6N mice. Histoplanimetrical analysis revealed significantly increased residual bodies and apoptotic germ cells in the seminiferous tubules in BXSB/MpJ-Yaa testes without apparent
inflammation. Notably, in stage XII of the seminiferous epithelial cycles, the apoptotic germ cell number was remarkably increased, showing a significant correlation with the indices of systemic
autoimmune disease in BXSB/MpJ-Yaa mice. Furthermore, the Sertoli cell number was reduced at the early disease stage, which likely caused subsequent morphological changes in BXSB/MpJ-Yaa testes. Thus, our histological study revealed the altered morphologies of BXSB/MpJ-Yaa testes, which were not observed in controls and statistical analysis suggested the effects of an autoimmune condition on this phenotype, particularly the apoptosis of meiotic germ cells. BXSB/MpJ-Yaa mice were shown to be an efficient model to study the relationship between systemic
autoimmune disease and the local reproductive system.