In vitro maturation of oocytes from a marsupial, the tammar wallaby (Macropus eugenii)

This study examined the competence of oocytes from the tammar wallaby, Macropus eugenii to mature in vitro. Oocytes were collected from follicles > 1 mm diameter 24 h after pregnant mare serum gonadotrophin (PMSG) treatment and incubated in Eagle's minimum essential medium supplemented with 10% fetal calf serum, at 35 degrees C in 5% CO2 in air for 24, 36, or 48 h. Oocytes were incubated either granulosa cell-intact or granulosa cell-free or in the presence of 10 IU ml-1 PMSG or 10 micrograms ml-1 porcine luteinizing hormone (LH) + 10 micrograms ml-1 porcine follicle stimulating hormone (FSH). The ability of oocytes recovered from small (< 1.5-mm-diameter) and large (> or = 1.5 mm-diameter) follicles to mature in vitro was also examined. The nuclear status of oocytes was assessed using the DNA-specific dye Hoechst 33342. Initially, all oocytes examined contained a germinal vesicle. After 24 h of culture, 60% of oocytes had progressed to metaphase I or anaphase I. After 36 h, approximately 20% of oocytes possessed metaphase II chromosomes, and 20% of oocytes were at metaphase I or anaphase I. At the completion of the 48 h culture period, 40% of oocytes had completed maturation to the metaphase II stage. In vitro oocyte maturation after 48 h was not affected by the presence of granulosa cells, PMSG, or LH and FSH. More oocytes from large follicles (55%) completed maturation by 48 h than from small follicles (20%). Approximately 50% of oocytes remained at the GV stage at all times under all conditions.(ABSTRACT TRUNCATED AT 250 WORDS)