Chelating agents in combination with rosmarinic acid for boar sperm freeze-drying

The presence of DNA protective agents in the medium is necessary to maintain sperm functionality after freeze-drying procedure. The objective of this study was to investigate the effect of chelating agents, ethylene diaminetetraacetic acid (EDTA) and ethylene glycoltetraacetic acid (EGTA), in combination with rosmarinic acid (RA) on DNA integrity of freeze-dried boar sperm. We also examined the effect of these agents on the in vitro developmental ability of porcine oocytes following sperm injection (ICSI). Heterospermic mix, obtained from ejaculated sperm of three boars, was freeze-dried in two different chelating agents' media: 50mM EDTA or 50mM EGTA, and in these media supplemented with 105μM of rosmarinic acid. Frozen-thawed sperm was used as control. After rehydration, samples were subjected to DNA damage detection using Sperm Chromatin Dispersion test. ICSI was performed to verify the ability of freeze-dried sperm to participate in embryonic development. Five replicated trials were carried out for each group. In the presence of rosmarinic acid, the percentage of spermatozoa with DNA damage decreased significantly (p=0.010), without differences between the two chelating agents combination. EDTA solution preserves more efficiently DNA integrity of boar sperm than EGTA solution (p=0.002). There were no significant differences among the studied groups related to the blastocyst formation rate. Results suggested that the addition of rosmarinic acid to the medium improves sperm DNA integrity after freeze-drying, but does not promote fertilization and blastocyst development. We also observed a similar percentage of embryos production with freeze-dried and with frozen-thawed sperm.