Abstract
OBJECTIVE: To investigate the effects of sperm deoxyribonucleic acid (DNA) damage on fertilization and embryo development using a mouse cryptorchidism model of sperm DNA damage induction.

MATERIALS AND METHODS: Male ICR mice (aged 5-6 weeks) underwent cryptorchidism on their left testicles and sham operations on their right testicles. Spermatogenesis and sperm DNA fragmentation were assessed after 1, 2, and 4 weeks using hematoxylin-eosin staining, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assays. Intracytoplasmic sperm injection into the oocytes of BDF1 females (aged 4-6 weeks) was performed using DNA-damaged sperm and normal sperm, and the fertilization rates and embryonic development were compared.

RESULTS: The testicular weight and size gradually decreased after induction of cryptorchidism, with progressive reduction of spermatogenesis and increased DNA damage after 1, 2, and 4 weeks. After intracytoplasmic sperm injection, the fertilization and blastocyst development rates were significantly lower in the cryptorchidism group; however, about one quarter of the embryos arising from DNA-damaged sperm continued to develop.

CONCLUSION: This was an in vivo animal study to evaluate the effects of sperm DNA damage using a cryptorchidism model. Sperm DNA damage increased significantly over time after cryptorchidism. This model could be useful in investigating male factor infertility and evaluating the biologic effects of paternal DNA damage on fertilization and future embryonic development.