Recombinant human gonadotropins for rhesus monkey superovulation: Age and the stimulation interval are determinant to the fecundity

The objective of this study was to analysis the key factors which may be determinative to Superovulation (SO) in rhesus monkey. Total 361 rhesus monkeys were stimulated with recombinant human gonadotropins and Ova Pick Up (OPU) was conducted by laparoscopic follicular aspiration. Number of total ova and oocytes at Metaphase I (MI) and Metaphase II (MII) (MI+MII) from each retrieval was calculated, MI+MII >= 10 was defined as effective SO-OPU while MI+MII<10 was defined as non-effective SO-OPU. Parameters including age, month in breeding season, stimulated times and stimulation interval were compared between effective and non-effective SO-OPU. The results showed that 5-10 years old rhesus monkeys were ideal oocytes donors while 3-4 years old and >10 years old monkeys included high rate of poor responders. SO conducted from late October to next February harvested similar fecundity while the rate of poor responders increased in March which imply proper SO breeding season should be from late October to next February. In addition, SO-OPU outcomes were gradually decreased along with the increased times of repeated stimulation. Further analysis showed that stimulation interval affected monkeys' response to recombinant ant human gonadotropins. When the interval was <2 menstrual cycles, the fecundity compromised significantly. In conclusion, the key determinative factors to SO-OPU should be animal's age and stimulation interval in rhesus monkey stimulated with recombinant human gonadotropins.