Production of live offspring from mouse germinal vesicle-stage oocytes vitrified by a modified stepwise method, SWEID

Objective: To evaluate viability and subsequent developmental ability in mouse germinal vesicle (GV) oocytes ultrarapidly vitrified with serial stepwise exposure. Design: Experimental animal study. Setting: University-based research laboratory. Animal(s): Three- to 4-week-old female (C57BL/6J × CBA) F1 mice in a laboratory environment. Intervention(s): Vitrified and thawed GV oocytes were subjected to in vitro maturation, fertilization, and culture, some of which were transferred to recipients. Main Outcome Measure(s): Postthaw survival, maturation, cleavage, development to blastocysts, and live births. Result(s): In the single-step preequilibrium, the rates of postthaw survival, maturation to metaphase II, and development to blastocysts were 97.5%, 95.8%, and 23.7%, respectively. In the serial 10-step preequilibrium developed in this study, which is named SWEID, the corresponding rates were 98.6%, 92.6%, and 42.9%, respectively, showing a statistically significantly higher rate of development to blastocysts in the SWEID group than in the single-step group. Transfer of two-cell-stage embryos derived from the GV oocytes vitrified by SWEID resulted in the production of live offspring. Conclusion(s): This is the first report that shows live birth after cryopreservation of mouse GV oocytes using an ultrarapid vitrification. Our method, SWEID, may have advantage in allowing storage of female gametes toward advances in infertility treatment and reproductive biology.