Derivation of developmentally competent oocytes by the culture of preantral follicles retrieved from adult ovaries: maturation, blastocyst formation, and embryonic stem cell transformation

Objective: To determine whether the preantral follicles in adult ovaries can generate developmentally competent oocytes after in vitro culture. Design: Prospective, animal-model study. Setting: Gamete and Stem Cell Biotechnology Laboratory, Seoul National University, Seoul, Korea. Animal(s): B6CBAF1 mice. Intervention(S): Preantral follicles collected from 8-week-old mice were cultured in vitro. Main Outcome Measure(s): Follicle development, embryogenesis, and embryonic stem cell characterization. Result(S): A mean of 50.3 preantral follicles were retrieved from one adult animal, which is significantly less than the number (88.7 follicles) retrieved from a prepubertal female. Extension of the culture period greatly improved oocyte maturation; increased follicular growth to the pseudo-antral (89%-91% vs. 32%) or mature oocyte stage (65%-77% vs. 13%) was observed after 12 or 13 days of culture compared with 9 days of culture. Blastocyst formation after parthenogenesis was detected in only one case; in comparison, the use of IVF yielded a large number of embryos that developed into blastocysts. A mean of 14.7 intrafollicular oocytes per animal were produced after 13 days of culture, and 41% of those developed into blastocysts after IVF. Embryonic stem cell-like colonies were established by subculturing the inner cell mass cells from the blastocysts. Conclusion(S): Developmentally competent oocytes can be generated by culturing adult preantral follicles. These results may help increase the feasibility of follicle culture systems. (Fertil Steril (R) 2009;92:1716-24. (C) 2009 by American Society for Reproductive Medicine.)