158 ASTAXANTHIN EFFECTS ON MATURATION, FERTILIZATION, AND DEVELOPMENT OF PORCINE OOCYTES CULTURED UNDER HEAT STRESS

Abstract

Heat stress can engender various disorders in reproductive functions such as impairment of oocyte maturation, fertilization, and embryonic development. Astaxanthin, an extremely common carotenoid, is a typical fat-soluble antioxidant that scavenges ROS and blocks lipid peroxidation. Moreover, astaxanthin has been shown to improve the development of embryos exposed to heat stress by a reduction in stress-inducible genes. This study was conducted to investigate the effects of astaxanthin supplementation on the meiotic competence, fertilization, and development of porcine oocytes exposed to high temperature (41°C) during maturation culture. Cumulus–oocyte complexes (COC) collected from ovaries were transferred into maturation medium supplemented with astaxanthin (0, 0.25, 0.5, or 1.0 ppm) and were then cultured for 46 h at 41°C or 38.5°C. After maturation culture, the COC were subjected to IVF and embryo culture to evaluate the fertility and development of oocytes. The total cell number and DNA fragmentation in the blastocysts were assessed using terminal deoxynucleotidyl transferase dUTP nick end labelling and Hoechst 33342 staining. The total numbers of oocytes matured at 41°C and 38.5°C in each treatment group were 432 to 470 and 426 to 444, respectively. Data were analysed using ANOVA, followed by Fisher's protected least significant difference test. Exposure to elevated temperatures during maturation culture significantly reduced the proportions of oocytes that reached metaphase II. When the COC were cultured in the maturation medium supplemented with 0.5 and 1.0 ppm of astaxanthin under heat stress conditions (41°C), the supplementation of astaxanthin significantly improved the proportions of maturation, fertilization, and blastocyst formation compared with the control group (0 ppm) (50–52%, 45–55%, and 11–12% v. 17, 25, and 6%, respectively). The supplementation of the maturation medium with 0.25 ppm of astaxanthin improved only blastocyst formation (9.6%). Similarly, the supplementation of astaxanthin at 1.0 ppm improved the proportions of maturation, fertilization, and blastocyst formation of oocytes matured at 38.5°C s compared with the control group (67, 57, and 18% v. 48, 33, and 12%, respectively). However, no beneficial effect of astaxanthin supplementation was found in the total cell number or DNA fragmentation in the blastocysts, irrespective of culture temperature. Our findings show that the supplementation of astaxanthin to maturation medium improves maturation, fertilization, and embryo development of porcine oocytes exposed to heat stress during maturation culture.