Optimal melatonin concentration to improve functional characteristics and fertilization capacity in thawed...

What is the optimal concentration of melatonin for improving sperm quality and function post-thawing during the cryopreservation process?

This study aimed to evaluate the seminal parameters, and the functional effects of melatonin supplementation at three different concentrations (0.01, 2 and 3 mM) on human spermatozoa post-thawing after cryopreservation by the slow freezing method. Semen analysis was performed before and after cryopreservation to determine cryosurvival rates post-thawing. Additional assessed sperm parameters included DNA fragmentation, mitochondrial status, lipoperoxidation, reactive oxygen species content, total antioxidant capacity, glutathione content, plasma membrane integrity, sperm acrosome integrity, and hyaluronan binding ability.

Notably, 2 mM melatonin significantly improved acrosome integrity (from 34.33 ± 12.55% to 36.33 ± 17.95%; P = 0.040), hyaluronic acid binding (from 87.1 ± 2.44% to 92.8 ± 1.97%; P = 0.002), and total antioxidant capacity (from 0.0117 ± 5.33 nmol/µl to 0.0130 ± 6.19 nmol/µl; P = 0.040), while higher concentrations did not yield additional benefits compared with the control group.

Based on functional tests, 2 mM melatonin is the optimal concentration to supplement sperm samples before cryopreservation by the slow freezing method to improve sperm quality and function characteristics.