Bleomycin in vitro exposure decreases markers of human male gamete competence.

Objective: To investigate the in vitro impact of bleomycin on human sperm deoxyribonucleic acid (DNA) integrity, functionality, and morphology, with the aim of elucidating the underlying mechanism and anticipating potential repercussions on patients' reproductive function.

Design: Controlled laboratory-based in vitro investigation.

Setting: University and clinical in vitro fertilization treatment center.

Patient(s): Surplus human ejaculate donated for research by 45 reproductive-age participants exhibiting normozoospermic sperm parameters after clinical semen analysis. None of the participants had received a cancer diagnosis or undergone radiotherapy, chemotherapy, or both.

Intervention(s): After clinical semen analysis, sperm samples were centrifuged, diluted in sperm preparation medium, and exposed to bleomycin (100 μg/mL) for 2 hours at 37 °C in a humidified incubator with 5% CO₂.

Main outcome measure(s): In vitro human sperm competence was evaluated by comparing raw sperm, sperm incubated with sperm preparation medium, and sperm exposed to bleomycin. Competence indicators included sperm motility, vitality, DNA and acrosome integrity, and mitochondrial membrane potential. Transmisson electron microscopy was employed to correlate the ultrastructural morphological findings with functional assays.

Result(s): Exposure to bleomycin for 2 hours in vitro significantly decreased sperm vitality, motility, and chromatin condensation compared with raw and control sperm. It also significantly increased sperm DNA fragmentation and the proportion of sperm with low mitochondrial membrane potential. Additionally, bleomycin significantly retarded the acrosomal response compared with control but did not affect the formation of intracellular and extracellular reactive oxygen species. Bleomycin-induced ultrastructural morphological changes supported the detected functional alterations.

Conclusion(s): Bleomycin negatively impacts male gamete competency in humans. Healthcare professionals should vigilantly monitor and further investigate the gonadotoxicity effects of bleomycin, in addition to its recognized lung toxicity. Meanwhile, it is recommended that patients with cancer undergoing bleomycin-containing chemotherapy regimens receive guidance on fertility preservation strategies.