Improving ovarian stimulation protocols for IVF in baboons: Lessons from humans and rhesus monkeys

Generation of cynomolgus monkey fetuses with intracytoplasmic sperm injection based on the MII-stage oocytes acquired by personalized superovulation protocol

Background

Mature oocytes at the metaphase II status (MII-stage oocytes) played an important role in assisted reproductive technology in non-human primates.

Objectives

In order to improve the proportion of MII-stage oocytes retrieval, three different superovulation protocols were performed on 24 female cynomolgus monkeys.

Methods

All the monkeys received once-daily injection of follicle-stimulating hormone (25 international unit [IU]) on day 3 of the menstruation, 3-day intervals, twice daily for 8–12 days until the time of human chorionic gonadotropin (1,500 IU) injection, on the 14–17th day of menstruation collecting oocytes. The difference between protocol I and protocol II was that 0.1 mg the gonadotropin-releasing hormone agonist was injected on day 1 of the menstruation, while the difference between personalized superovulation protocol and protocol II was that oocytes could be collected on the 14–17th day of menstrual cycle according to the length of each monkey.

Results

The total number of oocytes harvested using the personalized superovulation protocol was much higher than that using protocol I (p < 0.05), and the proportion of MII-stage oocytes was significantly greater than that from either superovulation protocol I or II (p < 0.001 and p < 0.01 respectively), while the proportion of immature oocytes at the germinal vesicle was less than that from superovulation protocol I (p < 0.05).

Conclusions

The personalized superovulation protocol could increase the rate of MII-stage oocytes acquired, and successfully develop into embryos after intracytoplasmic sperm injection, and eventually generated fetus.

Superovulatory responses in cynomolgus monkeys (Macaca fascicularis) depend on the interaction between donor status and superovulation method used

The current study was performed to investigate the effect of oocyte donor status, including age and body weight, on metaphase II (MII) oocyte recovery using two superovulation methods in cynomolgus monkeys. The use of Method A [recombinant gonadotrophin (75 IU/kg, 3 ×, 3-day intervals) and human chorionic gonadotropin (hCG)] led to great increases in ovary size and the mean number of MII oocytes retrieved in age- and body-weight-dependent manner; in contrast, both the parameters were similar in Method B [recombinant gonadotrophin (60 IU, twice daily, 6 days), recombinant gonadotropin and recombinant human luteinizing hormone (rhLH) (60 IU, twice daily, 3 days), and hCG]. Importantly, Method A showed maximal MII oocyte recovery rate in > 60-month-old or 4.5–5.0-kg female monkeys, whereas Method B was equally effective regardless of the donor age and body weight. These results indicate that superovulatory responses depend on the interaction between oocyte donor status and the superovulation method used in cynomolgus monkeys.

Utility of animal models for human embryo culture: nonhuman primates

Nonhuman primates are the closest relatives to humans and therefore our most evolutionary close cousins. While marvelous insights are gleaned from studying rodents and other systems, it is impossible to envision how those mechanistic findings can be responsibly translated to the clinic without the appropriate use of nonhuman primates. Thankfully, noninvasive technologies now permit nonhuman primate studies without endangering the model itself. Work with primates is predicted to continue to lead the fields of reproductive and regenerative medicine for the rest of the twenty-first century.

In vitro oocyte maturation and preantral follicle culture from the luteal-phase baboon ovary produce mature oocytes

Female cancer patients who seek fertility preservation but cannot undergo ovarian stimulation and embryo preservation may consider 1) retrieval of immature oocytes followed by in vitro maturation (IVM) or 2) ovarian tissue cryopreservation followed by transplantation or in vitro follicle culture. Conventional IVM is carried out during the follicular phase of menstrual cycle. There is limited evidence demonstrating that immature oocyte retrieved during the luteal phase can mature in vitro and be fertilized to produce viable embryos. While in vitro follicle culture is successful in rodents, its application in nonhuman primates has made limited progress. The objective of this study was to investigate the competence of immature luteal-phase oocytes from baboon and to determine the effect of follicle-stimulating hormone (FSH) on baboon preantral follicle culture and oocyte maturation in vitro. Oocytes from small antral follicle cumulus-oocyte complexes (COCs) with multiple cumulus layers (42%) were more likely to resume meiosis and progress to metaphase II (MII) than oocytes with a single layer of cumulus cells or less (23% vs. 3%, respectively). Twenty-four percent of mature oocytes were successfully fertilized by intracytoplasmic sperm injection, and 25% of these developed to morula-stage embryos. Preantral follicles were encapsulated in fibrin-alginate-matrigel matrices and cultured to small antral stage in an FSH-independent manner. FSH negatively impacted follicle health by disrupting the integrity of oocyte and cumulus cells contact. Follicles grown in the absence of FSH produced MII oocytes with normal spindle structure. In conclusion, baboon luteal-phase COCs and oocytes from cultured preantral follicles can be matured in vitro. Oocyte meiotic competence correlated positively with the number of cumulus cell layers. This study clarifies the parameters of the follicle culture system in nonhuman primates and provides foundational data for future clinical development as a fertility preservation option for women with cancer.

Acceptability of preclinical research on nonhuman primates in reproductive medicine: the patient perspective

The attitude of patients with reproductive disorders regarding the use of nonhuman primates (NHPs) in preclinical reproductive research and its determinants was examined. A survey was conducted on 299 patients with fertility problems and/or endometriosis in a European fertility center (RR = 80%). The main outcome measure was the attitude toward reproductive research on NHPs. In total, 70.6% accept and 29.4% reject NHP research. Factors significantly positively related to acceptance are confidence in researchers and previous pregnancy. Factors significantly negatively related to acceptance include having a pet, membership of a nature organization, vegetarian, and having lived abroad. To the best of our knowledge, this study is the first on patients' perspective on NHP research. The majority of the patients accept reproductive research on NHPs. Trust in researchers was the most important positively related factor; therefore, researchers are advised to actively try to gain the trust of patients and the public.

Assisted Reproductive Technologies (ART) with baboons generate live offspring: a nonhuman primate model for ART and reproductive sciences

Human reproduction has benefited significantly by investigating nonhuman primate (NHP) models, especially rhesus macaques. To expand the Old World monkey species available for human reproductive studies, we present protocols in baboons, our closest Old World primate relatives, for assisted reproductive technologies (ART) leading to live born offspring. Baboons complement rhesus by confirming or modifying observations generated in humans often obtained by the study of clinically discarded specimens donated by anonymous infertility patient couples. Here, baboon ART protocols, including oocyte collection, in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), preimplantation development to blastocyst stage, and embryo transfer techniques are described. With baboon ART methodologies in place, motility during baboon fertilization was investigated by time-lapse video microscopy (TLVM). The first ART baboons produced by ICSI, a pair of male twins, were delivered naturally at 165 days postgestation. Genetic testing of these twins confirmed their ART parental origins and demonstrated that they are unrelated fraternal twins not identicals. These results have implications for ART outcomes, embryonic stem cell (ESC) derivation, and reproductive sciences.

Separate and combined effects of caffeine and dbcAMP on olive baboon (Papio anubis) sperm

BACKGROUND

Improvement of baboon sperm capacitation is necessary for achieving high in vitro fertilization (IVF) rates in baboons. In this study, we evaluated separate and combined effects of caffeine and dbcAMP on baboon sperm capacitation.

METHODS

Sixteen male baboons (n = 16) were electroejaculated. Each sperm sample was divided into two aliquots: one for chemical activation and the other untreated control. Group 1: dbcAMP (n = 6); Group 2: caffeine (n = 6) and Group 3: combination of caffeine and dbcAMP (n = 4). In each aliquot, sperm motility after 30 minutes of incubation was evaluated as well as zona pellucida (ZP) binding ability after overnight incubation with 4-5 ZP from unfertilized human oocytes.

RESULTS

Sperm motility and ZP binding ability in all chemically activated groups increased significantly as compared to their respective controls (P < 0.05).

CONCLUSION

Combined and separate effects of caffeine and dbcAMP increases baboon sperm motility and ZP binding ability and may improve baboon IVF.