Isolation,in vitro maturation,and fertilization of germinal vesicle oocytes obtained from the intact murine ovary

The purpose of this investigation was to attempt to develop a process, utilizing a murine model, which would allow more efficient harvesting from the intact ovary and maturation in vitro of germinal vesicle (GV) oocytes. The recovery process yielded 25.5±4.5 (±SE) cumulusfree GV oocytes per animal. Treatment groups included culture medium (CM) supplemented with either estradiol (E₂), follicle stimulating hormone (FSH), human chorionic gonadotropin (hCG), or prolactin (PRL). Among the hormone-free controls 83.2±1.6% of oocytes underwent GV breakdown, whereas 25.3±2.6% developed to the first polar body stage (PB-1) following 18 hr of incubation (n=29 trials). Oocytes progressing to the PB-1 stage were inseminated in vitro. In vitro fertilization (IVF) of pooled in vitro matured (IVM) PB-1 oocytes (judged by two-cell formation) was 19.9%, which was significantly lower than in the group of in vivo matured oocytes (74.7%). E₂ significantly increased the percentage of GV breakdown (control, 76.8±2.5%; E₂ at 10 ng/ml, 92.9±2.5%,P<0.001; E₂ at 100 ng/ml, 93.7±2.1%,P<0.001; and E₂ at 1 g/ml, 86.7±3.3%,P<0.05) but not PB-1 formation. Neither FSH nor hCG significantly increased GV breakdown or PB-1 formation. Prolactin treatment resulted in an increased percentage of PB-1 formation (control, 25.3±2.5%; PRL at 2 g/ml, 35.0±2.9%; and PRL at 20 g/ml, 34.1±1.9%;P<0.01), fertilization (control, 15.3±5.1%; PRL, 33.6±8.5;P<0.01), and subsequent development (control, 3.5±2.3%; PRL, 18.8±5.6%;P<0.01). We conclude that recovery and IVM of GV oocytes is feasible, however, further work is necessary to define optimal conditions.