Autoimmune regulator deficiency causes sterile epididymitis and impacts male fertility through disruption of inorganic physiology

Autoimmune regulator (AIRE), a transcription factor expressed by medullary thymic epithelial cells, is required for shaping the self-antigen tolerant T cell receptor repertoire. Humans with mutations in AIRE suffer from Autoimmune Polyglandular Syndrome Type 1 (APS-1). Among many symptoms, men with APS-1 commonly experience testicular insufficiency and infertility, but the mechanisms causing infertility are unknown. Using an Aire-deficient mouse model, we demonstrate that male subfertility is caused by sterile epididymitis characterized by immune cell infiltration and extensive fibrosis. In addition, we reveal that the presence of autoreactive immune cells and inflammation in epididymides of Aire-deficient mice are required for iron (Fe) deposition in the interstitium, which is brought on by macrophages. We further demonstrate that male subfertility is associated with a decrease in metals zinc (Zn), copper (Cu), and selenium (Se) which serve as cofactors in several antioxidant enzymes. We also show increase in DNA damage of epididymal sperm of Aire-/- animals as a key contributing factor to subfertility. The absence of Aire results in autoimmune attack of the epididymis leading to fibrosis, Fe deposition, and Cu, Zn and Se imbalance, ultimately resulting in sperm DNA damage and subfertility. These results highlight the requirement of Aire to promote immune tolerance throughout the epididymis, disruption of which causes an imbalance of inorganic elements with resulting consequence on male fertility. Key pointsBreakdown of epididymal self-tolerance promotes disruption of inorganic elements. Autoimmunity causes interstitial fibrosis resulting in sperm DNA damage and subfertility. Elevated interstitial iron and macrophages contribute to fibrosis.