Background: Infertility, defined as the inability to conceive after one year of unprotected intercourse, affects a significant portion of the population. Assisted reproductive technologies (ART) offer treatment options in which sperm processing is a critical step. This process usually takes about an hour and involves separating sperm from other components of the seminal fluid. However, exposure to external factors during this step can cause oxidative stress and reduce sperm quality. Therefore, the use of antioxidants is recommended to reduce oxidative stress and increase the success of ART. N-acetylcysteine (NAC), a potent antioxidant containing thiol groups, effectively neutralizes free radicals and protects sperm from oxidative damage. Objective: Given that some normal, fertile men may benefit from ART, this study aims to evaluate the effect of NAC on the quality, biochemical properties, and reactive oxygen species levels of normal human sperm during one hour of in vitro incubation. Materials and Methods: After liquefaction, semen samples from 30 fertile men were divided into 2 groups: control (no treatment, 1-hr incubation) and NAC-treated (50 μM NAC, 1-hr incubation). The study assessed sperm parameters, including motility, viability, DNA and chromatin integrity, plasma membrane integrity, and mitochondrial membrane potential. Additionally, total antioxidant capacity, malondialdehyde, and reactive oxygen species levels were evaluated. Results: In the NAC group, compared to the control group, there was a significant increase in the mean percentages of total and progressive sperm motility, chromatin and DNA integrity, cytoplasmic integrity, mitochondrial membrane potential, and total antioxidant capacity levels (p < 0.001). Conversely, the mean percentage of non-progressive sperm motility (p < 0.001), as well as malondialdehyde (p = 0.005) and reactive oxygen species levels (p = 0.01), were significantly lower in the NAC group compared to the control group. Conclusion: We concluded that NAC improves sperm quality during in vitro incubation by increasing motility, integrity, mitochondrial function, and antioxidant capacity while reducing oxidative stress markers. These findings suggest NAC is a valuable antioxidant supplement for improving sperm quality and increasing ART success rates.
