Exposure to zinc oxide nanoparticles affects testicular structure, reproductive development and spermatogenesis in parental and offspring male rats.

Background: This study aimed to comprehensively evaluate the toxicity exerted by zinc oxide nanoparticles (ZnO NPs) on rat testis and its effects on fertility and progeny development.

Methods: Different concentrations of ZnO NPs were administered by gavage to Sprague Dawley (SD) rats to examine the adverse effects resulting from pre- and post-natal exposure. Systemic distribution of ZnO NPs, developmental performance, sperm parameters, reproductive performance, histopathological examination, and sex hormone levels were determined scheduled in the experimental rats and their male offspring. The comparative cytotoxicity of the ZnO NPs was determined among C18-4, TM3, and TM4 cells. The toxicity exerted by ZnO NPs on germ cells and the effects on the expression of cytoskeleton and blood-testis barrier (BTB)-related proteins were also determined.

Results: After oral gavage, ZnO NPs mainly accumulated in the liver and testes of rats; 350 mg/kg ZnO NPs adversely affected the epididymal weight, sperm motility, and hormone levels but did not affect the fertility of rats. In addition, 350 mg/kg ZnO NPs significantly reduced the reproductive and developmental performance of offspring male rats. Testicular histopathological and electron microscopic ultrastructure examinations showed more significant abnormal structural changes than those observed in parental rats. The results of cell experiments further showed that ZnO NPs exerted cytotoxic effects on germ cells, and led to DNA damage, nucleoskeleton and cytoskeleton alterations, and could regulate actin changes through changes in LC3B.

Conclusions: It is possible that ZnO NPs act directly on TM4 cells by penetrating the BTB, causing damage to the cytoskeleton and disrupting the dynamic balance of the BTB, thereby destroying the microenvironment necessary for spermatogenesis, which may lead to poor reproduction in rats.