Melatonin Improves Sperm Quality in Asthenozoospermic Men by Preserving Acrosome Integrity, Reducing Inflammation, and Regulating Apoptosis-Related Genes and Proteins during Freeze-Thawing.

OBJECTIVE: Sperm freeze-thaw is a crucial technique in assisted reproductive technologies (ART), but it induces oxidative stress in sperm. Melatonin, a powerful antioxidant, reduces oxidative stress by penetrating mitochondria and neutralising free radicals. However, its protective role in the sperm of asthenozoospermic men during freeze-thaw remains poorly understood. This study examines the in vitro effects of melatonin on sperm quality in asthenozoospermic men during the freeze-thaw process. MATERIALS AND METHODS: In this experimental study, semen samples were collected from 30 asthenozoospermic men and divided into three groups: control group, freeze group, and freeze+melatonin (1 mM) group. Sperm parameters including mitochondrial membrane potential (MMP), plasma membrane integrity, acrosomal reaction, and DNA fragmentation were assessed. The levels of superoxide dismutase (SOD), glutathione peroxidase (GSH), total antioxidant capacity (TAC), malondialdehyde (MDA), reactive oxygen species (ROS), tumour necrosis factor-alpha (TNF-α), and interleukin-10 (IL-10) were estimated. Expressions of apoptosis-related genes and proteins, BAX and BCL-2, were also analysed. RESULTS: There was a significant decrease (P=0.004) in sperm parameters, MMP, plasma membrane and acrosome integrity, TAC, GSH, SOD, IL-10 levels, and Bcl-2 expression in the freeze group compared to the control group. Conversely, MDA, ROS, TNF-α, DNA fragmentation, and BAX expression significantly increased (P=0.010). However, all these parameters showed significant improvements in the freeze+melatonin group compared to the freeze group (P=0.019). CONCLUSION: Melatonin may improve sperm quality during freeze-thaw by increasing antioxidant defence, reducing inflammation via TNF-α/IL-10 modulation, inhibition of apoptosis through BAX/BCL-2 regulation, and preservation of acrosome integrity. These findings suggest that melatonin may have potential as a cryoprotectant in ART.