Incubation of semen with human follicular fluid improves the antioxidant status and quality of spermatozoa after freezing-thawing.

Graphical abstract:

Abstract: The sperm freezing-thawing procedure is the most commonly used technique in clinics to preserve male fertility before any pathological destruction of the testis. Therefore, most studies are currently focused on optimizing this method to achieve high-quality semen after thawing. During cryopreservation, oxidative stress-induced damage affects sperm structures and decreases their fertility potential. The use of antioxidants in freezing media can protect sperm against oxidative damage. We designed this study to evaluate whether incubation of semen with human follicular fluid, which contains a wide variety of enzymatic and nonenzymatic antioxidants, can prevent the negative effects of freezing-thawing on human spermatozoa. Human semen was divided into three groups i) the 0-hour group (before freezing), ii) the control group (after freezing-thawing), and iii) the FF group (after freezing with 50% follicular fluid). The sperm motility, viability, integrity of the plasma membrane and DNA, mitochondrial membrane potential, malondialdehyde level, total antioxidant capacity, and catalase activity were assessed in these three groups. The findings showed a significant decrease in sperm motility, viability, plasma membrane and DNA integrity, mitochondrial membrane potential, total antioxidant capacity, and catalase activity and a significant increase in malondialdehyde level in the control group compared with the 0-hour group. The FF group displayed a considerable increase in sperm parameters, total antioxidant capacity, and catalase activity and a significant decrease in malondialdehyde level compared with the control group. Follicular fluid can be considered an effective supplement to improve antioxidant indices and sperm parameters during freezing-thawing.

Lay summary: Sperm freezing is a useful method in clinics to preserve fertility in people who are affected by some problems such as diseases or chemotherapy which decrease their fertility. Although various studies are focused on optimizing this method, some challenges decrease the efficiency of this method. Oxidative stress has been reported as one of the mechanisms inducing negative effects on sperm during freezing-thawing. Therefore, the use of cryoprotectants and also some antioxidants has been suggested to increase sperm quality during freezing-thawing. In this study, we used human follicular fluid before freezing to assess sperm parameters. Our results showed that follicular fluid with antioxidant properties and other proper factors can have positive effects on human sperm during freezing-thawing and could be proposed to be added to the sperm freezing medium to improve sperm parameters, although this suggestion needs to be confirmed by further experiments.