The effects of vitamin E supplementation on sperm parameters, chromatin integrity, and gene expression before and after freezing in aged mice.

Objective: Some age-related testicular changes, such as Sertoli cell vacuolization and blood-testis barrier breakdown, reduce total sperm production and male fertility. Therefore, this study investigated the effect of vitamin E on restoring testicular function in aged mice. Sperm cryo-resistance was also assessed.

Methods: Twenty-eight 48-week-old male Naval Medical Research Institute mice were divided into four groups for a daily gavage of vitamin E: the control group received distilled water, while the three treatment groups were administered 100, 200, and 400 mg/kg, respectively, for 4 weeks. Subsequently, semen analyses, DNA fragmentation index (DFI), and protamine deficiency tests were conducted. Testicular histology, tissue antioxidant enzyme activity, and gene expression levels were also assessed.

Results: The two higher dosages of vitamin E were associated with a higher sperm count, greater progressive motility, and improved sperm morphology (p<0.05). These benefits were also evident after sperm freezing (p<0.05). Although chromatin abnormalities increased following vitrification, the treatment groups showed better outcomes (p<0.05). The tubular diameter, epithelium height, and luminal diameters remained unchanged with age. The tissue antioxidant capacity was greater in the groups receiving the high doses of vitamin E. Additionally, significant increases in inhibitor of DNA binding protein-4 (Id4) and GDNF family receptor alpha-1 (Gfra1) expression were observed in the higher vitamin E dosage groups, and promyelocytic leukemia zinc finger protein (Plzf) expression was notably present in the 400 mg/kg treatment group compared to the control group (p<0.05).

Conclusion: Antioxidant supplementation might enhance reproductive outcomes in aging males. The observed effects included improved sperm cryo-resistance, which is advantageous for future applications such as sperm freezing or fertility preservation.