Growing porcine oocytes from early antral follicles can acquire meiotic and developmental competence under suitable culture conditions, but at lower rates compared to full-grown oocytes. We postulated that estradiol-17β (E2 ) supported the acquisition of meiotic and developmental competence as well as cumulus-expansion ability during growth culture. Growing oocytes from early antral follicles (1.2 to 1.5 mm in diameter) were grown in vitro for 5 days in a medium containing 0, 10(-7) , 10(-6) , 10(-5) or 10(-4) mol/L E2 ; after in vitro maturation, 35, 58, 47, 74 and 49% of oocytes matured to metaphase II, 25, 79, 77, 90 and 97% acquired cumulus-expansion ability, and 23, 54, 63, 89 and 64% were fully surrounded by cumulus cells, respectively. Following maturation, electro-stimulation was applied to the oocytes grown with 10(-5) mol/L E2 . After 6 days of culture, in vitro-grown oocytes developed to the blastocyst stage at a rate similar to that for full-grown oocytes (31% and 40%, respectively). Therefore, we suggest that the use of E2 during growth culture improves the meiotic and developmental competence of oocytes, cumulus-expansion ability, and cumulus cell attachment to the oocytes.
Keywords: blastocyst; electro-stimulation; estradiol-17β; in vitro growth; porcine oocyte.
© 2014 Japanese Society of Animal Science.