This study aimed to develop a more suitable ovarian stimulation procedure for cynomolgus macaques (Macaca fascicularis). Macaques were divided into 4 groups, 7AG, 8AG, 7AN, and 8AN, according to the ovarian stimulation procedure administered (i.e., administration of either a gonadotropin-releasing hormone agonist [GnRH-a] or GnRH antagonist [GnRH-ant]) and the number of menstruations (≤ 7 times or ≥ 8 times) in the previous year. In both procedures, oocyte growth and maturation were induced by administration of human follicle-stimulating hormone and human chorionic gonadotropin. The mean numbers of metaphase II mature and metaphase I premature oocytes collected from the 7AG, 8AG, 7AN, and 8AN groups were 12.1 and 10.4, 12.0 and 13.8, 9.1 and 8.3, and 15.5 and 8.8, respectively (P>0.05). The fertilization rates of the 7AN and 8AN groups (85.3% and 74.7%) tended to be higher compared with those in the 7AG and 8AG groups (59.1% and 47.3%; P>0.05). The 8AN group yielded 19.9 zygotes, which was the largest number per macaque, compared with the other three groups. Furthermore, regarding the decreases in body weight between the start of the procedures and the time of oocyte collection, those of the 7AN and 8AN groups were significantly smaller than those of the 7AG and 8AG groups (P<0.05), suggesting that the procedure involving GnRH-ant reduced the burden on the macaques. Thus, controlled ovarian stimulation using a GnRH-ant has some advantages for cynomolgus macaques compared with that using a GnRH-a.
Keywords: GnRH analogue; body weight; cynomolgus macaque; oocyte; ovarian stimulation.