254 DEVELOPMENTAL COMPETENCE OF MOUSE OOCYTES AFTER IN VITRO GROWTH, NUCLEAR TRANSFER, AND IN VITRO FERTILIZATION

Long-term effects of in vitro maturation of oocytes and in vitro culture of fertilized eggs have been reported in ruminants, mice, and humans. However, effects of in vitro oocyte growth are unknown. Although a large number of non-growing oocytes can be a gamete resource, very few oocytes ever acquire competence to support full-term development after in vitro growth. The objective of the study was to evaluate different culture conditions and the long-term effects of in vitro oocyte growth on the production of offspring. Oocytes of newborn, 10-day-old, and adult BDF1 (C57BL/6N × DBA2) mice were cultured for 22, 11, and 1 day(s), respectively. The results showed that alpha-MEM medium was superior to Waymouth medium in oocyte growth (68.6 ± 3.87 µm vs. 61.7 ± 3.26 µm, respectively; P 0.05). When the donor oocytes attained a diameter of 50–60 µm, the reconstituted oocytes also could develop into pups (7/33); however, their efficiency was significantly reduced when compared with that of the reconstituted oocytes from the control GV (P < 0.05). On the other hand, the weight of the offspring depended on the duration of culture, and offspring from non-growing oocytes (1.48 ± 0.17 g) were heavier than those of the IVF control (1.25 ± 0.14 g; P < 0.05). In conclusion, we have demonstrated that using a nuclear transfer technique combined with in vitro growth of oocytes was sufficient to produce functional oocytes, and long-term culture for oocyte growth did not affect the nucleic ability of oocytes to develop to term; however, fetal growth may be susceptible to the duration of culture.