Impact of post-thaw supplementation of semen extender with antioxidants on the quality and function variables of stallion spermatozoa

Abstract

During cryopreservation procedures, the spermatozoa are exposed to physical and chemical stressors that generate an increase in the intracellular concentration of reactive oxygen species (ROS). If ROS concentrations are too great, this can lead to a state of oxidative stress that are detrimental to sperm quality. The aim of this study was to ascertain the profile the ROS production and assess the effects of post-thaw supplementation of a semen extender with different antioxidant compounds on the quality and function variables of frozen-thawed stallion spermatozoa incubated in vitro. Frozen-thawed stallion spermatozoa (2 × 10⁶ cells/mL) were incubated with three different antioxidants (MnTBAP, NAC and FeTPPS) for 4 h at 38 °C. An untreated sperm suspension and a fresh sample were included as controls. Plasma membrane integrity (SYBR-14/PI), intracellular ROS concentration (DHE and ROS-ID™ total ROS/Superoxide Detection Kit), lipid peroxidation (BODIPY), DNA damage (TUNEL) and mitochondrial membrane potential (ΔΨm; TMRE/SYTOX) were evaluated by flow cytometry and fluorescence microscopy. In addition, sperm motility was evaluated using the ISAS system. Evaluations were performed at 0 and 4 h of incubation. The results indicate that superoxide anion is the main ROS produced by frozen-thawed stallion spermatozoa and that the use of MnTBAP improved sperm motility and viability, decreased the lipid peroxidation and DNA damage. In conclusion, this study provides relevant data to improve in vitro incubations conditions and to establish futures therapies using MnTBAP after thawing with the aim being to overcome the deleterious effects of semen cryopreservation and consequently preserve the stallion sperm quality through avoiding oxidative stress.

Keywords: Antioxidants; Cryopreservation; Oxidative stress; Stallion sperm.