Comparative maturation of cynomolgus monkey oocytes in vivo and in vitro

Young, adult cynomolgus monkeys were given recombinant human (rh) gonadotropins to stimulate the development of multiple follicles, and oocytes were aspirated 0, 12, 24, or 36 h after injection of an ovulatory dose of rhCG. The nuclear status of oocytes was determined at the time of recovery and after culture for a total elapsed time of 40–44 hours after hCG.Priming with hCG significantly increased the number of oocytes harvested, especially after delaying aspiration for 24 h or longer. Nuclear maturation after the full period in culture was also enhanced by priming: 71.5, 83.6, and 94.6% of oocytes collected at 0, 12, and 24 h hCG had progressed to MII by the end of the culture period, compared to 87.8% of oocytes that were retrieved at 36 h. A large proportion of oocytes reaching the MII stage had either or both abnormal spindles (>40%) and misaligned chromosomes (>60%), judging by immunofluorescence microscopy, but these abnormalities were independent of culture time. The mitochondria were evenly distributed throughout the cytoplasm at all stages of maturation. Importantly, there was no microscopic evidence that the duration of culture had any injurious effects on the cells.In conclusion, the evidence supports this non-human primate as a model for human IVM and the practice of priming with hCG to promote developmental potential.In vitro maturation (IVM) is a culture technology that enables a high proportion of fully-grown oocytes at the germinal vesicle (GV) stage to reach metaphase II (MII). When mature, the oocytes may be fertilised in vitro and they become available for transfer to a physiologically synchronised reproductive tract after reaching the cleavage or blastocyst stage. While pregnancy rates after IVM can be impressively high in some laboratory and farm animal species [1-6], applications for human reproductive medicine are just now gathering momentum.The first human birth reported after IVM was achieved after controlled ovarian stimulation [7]. More t