Role of calcifying nanoparticles in the development of testicular microlithiasis in vivo

BACKGROUND: Calcifying nanoparticles (NPs) have been proven to be associated with a variety of pathological calcification and previously detected in semen samples from patients with testicular microlithiasis (TM). The present study was designed to test the hypothesis if human-derived NPs could invade the seminiferous tubules and induce TM phenotype. METHODS: The animals were divided into three groups. Normal saline (0.2 mL) was injected into the proximal right ductus deferens in group A as a control group. The experimental groups, B and C received Escherichia coli (10(6) cfu/mL, 0.2 mL) and human-derived NPs suspension (0.2 mL), respectively. Rats were euthanized in 2 batches at 2 and 4 weeks. Testicular pathology, ultrastructure and inflammatory mediators were assessed. RESULTS: Chronic inflammatory changes were observed at 2 weeks in both groups B and C. Moreover, the innermost layer of sperm cells were structurally impaired and a zone of concentrically layered collagen fibers around the human NPs body was formed in the lumen of the seminiferous tubule in group C only, in which TM phenotype of remarkable calcification surrounded by cellular debris within the seminiferous tubules was built at 4 weeks. CONCLUSIONS: The results obtained from our study suggested a potential pathogenic effect of NPs in the development of calcification within the seminiferous tubules, which should be addressed in the future studies.