86 Development of porcine embryos cultured in media irradiated with ultraviolet at 228 and 260 nm wavelengths

Ultraviolet (UV) irradiation is a convenient method of disinfecting gases and liquids. The spectral range of 200–230 nm, referred to as far-UV-C, is hypothesised to be as effective as the 254 nm UV-C irradiation of widely used mercury vapor lamps. Sterilization of the culture medium using UV-C not only reduces the potential adverse effects of microorganisms during cell and embryo culture but also may allow for long-term use. In the present study, we investigated the effects of medium directly irradiated with UV-C before in vitro culture on the development and quality of porcine IVF embryos. Furthermore, we examined the effects of UV-C irradiation on the composition of free amino acids in the medium. In the first embryo experiment, the culture media (porcine zygote medium (PZM-5) and porcine blastocyst medium (PBM)) were irradiated with 228 and 260 nm UV-C in a glass culture tube at a distance of 10 cm for 1 and 3 days. In the second embryo experiment, the culture medium was irradiated with 228 nm UV-C in a glass culture tube at a distance of 10 cm for 3, 7, and 14 days. After IVF, embryos were cultured in UV-C-irradiated media for 7 days. In the third experiment, free amino acid levels in the culture media (PZM-5 and PBM) irradiated with 228 and 260 nm UV-C for 3 days were analysed according to the instructions of the high-speed amino acid analyzer (LA8080, Hitachi Ltd). Medium with no UV-C irradiation was used as a control. Each experiment was performed three to five times. Data for embryo development and free amino acid analysis were evaluated using analysis of variance (ANOVA), followed by Fisher’s protected least significance test. In the first experiment, blastocyst formation rates from embryos cultured in media irradiated with 260 nm UV-C were significantly lower (P < 0.05) than those from embryos cultured in media irradiated with 228 nm UV-C, irrespective of the exposure duration. Furthermore, blastocyst formation rates from embryos cultured in media irradiated with 260 nm UV-C for 3 days were significantly lower (P < 0.05) than those of nonirradiated control embryos. In the second experiment, when embryos were cultured in culture media that had been irradiated with 228 nm UV-C for up to 14 days, there were no differences in blastocyst formation rates, total cell numbers, or percentage of apoptotic cells in the resulting blastocysts. In the third experiment, 228 nm UV-C irradiation did not affect the concentration of free amino acids in either culture media. However, 260 nm UV-C irradiation significantly increased the concentration of taurine in both culture media (PZM-5, 12.3 vs 1.0 mg/100 mL; and PBM, 13.6 vs 1.01 mg/100 mL, respectively, P < 0.05) and significantly decreased the concentration of methionine in PBM (0.51 vs 0.63 mg/100 mL, P < 0.05) as compared with the nonirradiated controls. In conclusion, culture media irradiated with 228 nm UV-C before in vitro culture had no detrimental effects on embryonic development or embryo quality, even though the media were irradiated for up to 14 days. Furthermore, 260 nm UV-C irradiation decreased embryo development and altered the composition of free amino acids in the medium.