Superovulatory response to a low dose single-daily treatment of rhFSH dissolved in polyvinylpyrrolidone in rhesus monkeys

In vitro matured oocytes have a higher developmental potential than in vivo matured oocytes after hormonal ovarian stimulation in Callithrix jacchus

BACKGROUND

The common marmoset, Callithrix jacchus, is an invaluable model in biomedical research. Its use includes genetic engineering applications, which require manipulations of oocytes and production of embryos in vitro. To maximize the recovery of oocytes suitable for embryo production and to fulfil the requirements of the 3R principles to the highest degree possible, optimization of ovarian stimulation protocols is crucial. Here, we compared the efficacy of two hormonal ovarian stimulation approaches: 1) stimulation of follicular growth with hFSH followed by triggering of oocyte maturation with hCG (FSH + hCG) and 2) stimulation with hFSH only (FSH-priming).

METHODS

In total, 14 female marmosets were used as oocyte donors in this study. Each animal underwent up to four surgical interventions, with the first three performed as ovum pick-up (OPU) procedures and the last one being an ovariohysterectomy (OvH). In total, 20 experiments were carried out with FSH + hCG stimulation and 18 with FSH-priming. Efficacy of each stimulation protocol was assessed through in vitro maturation (IVM), in vitro fertilization (IVF) and embryo production rates.

RESULTS

Each study group consisted of two subgroups: the in vivo matured oocytes and the oocytes that underwent IVM. Surprisingly, in the absence of hCG triggering some of the oocytes recovered were at the MII stage, moreover, their number was not significantly lower compared to FSH + hCG stimulation (2.8 vs. 3.9, respectively (ns)). While the IVM and IVF rates did not differ between the two stimulation groups, the IVF rates of in vivo matured oocytes were significantly lower compared to in vitro matured ones in both FSH-priming and FSH + hCG groups. In total, 1.7 eight-cell embryos/experiment (OPU) and 2.1 eight-cell embryos/experiment (OvH) were obtained after FSH + hCG stimulation vs. 1.8 eight-cell embryos/experiment (OPU) and 5.0 eight-cell embryos/experiment (OvH) following FSH-priming. These numbers include embryos obtained from both in vivo and in vitro matured oocytes.

CONCLUSION

A significantly lower developmental competence of the in vivo matured oocytes renders triggering of the in vivo maturation with hCG as a part of the currently used FSH-stimulation protocol unnecessary. In actual numbers, between 1 and 7 blastocysts were obtained following each FSH-priming. In the absence of further studies, FSH-priming appears superior to FSH + hCG stimulation in the common marmoset under current experimental settings.

Long-term effects of repeated superovulation on the uterus and mammary gland in rhesus monkeys

PURPOSE

The aim of this study is to evaluate the effect of repeated controlled ovarian hyperstimulation (COH) on the structure and function of the uterus and mammary gland.

METHODS

Three adult female rhesus monkeys were superovulated up to four times, and three spontaneously ovulating monkeys were used as controls. After a 5-year period, the uterus and mammary gland tissue samples were collected for examination of their structure and function. Further, the expression of certain tumor markers was examined to assess the cancer risk for each organ.

RESULTS

Expression of Wnt7a (associated with the functional/developmental status of the uterus) was significantly decreased in the uterus of superovulated monkeys, and decreased expression of proliferation marker PCNA was found in uterine cells. Meanwhile, abnormal Golgi-derived secretory vesicles with an irregular shape were observed in the mammary glands of the superovulated monkeys, and decreased PCNA expression together with increased expression of caspase-3 (an apoptosis marker) was indicated in the mammary cells. The expression of tumor molecular markers of the uterus and mammary gland was not significantly different between the two groups.

CONCLUSIONS

Repeated COH affects the expression of the uterine development-related gene several years later, and uterine cells exhibited a low proliferation status. The ultrastructure of the mammary gland epithelial cells was abnormal, and the cells exhibited both low proliferation and high apoptosis status. Cancer risk for these organs was not observed. Given that primates are the closest relatives of humans, the results obtained from this study provide more intuitive information for optimization of clinical COH.

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.

Efficient production of cynomolgus monkeys with a toolbox of enhanced assisted reproductive technologies

The efficiency of assisted reproductive technologies (ARTs) in nonhuman primates is low due to no screening criterions for selecting sperm, oocyte, and embryo as well as its surrogate mothers. Here we analyzed 15 pairs of pregnant and non-pregnant cynomolgus monkeys, each pair of which received embryos from one batch of fertilized oocytes, and found ratio of endometrial to myometrial thicknesses in abdominal ultrasonic transverse section of uterus is a reliable indicator for selection of recipients for embryo transfer. We performed 305 ovarian stimulations in 128 female cynomolgus monkeys and found that ovarian stimulation can be performed in a whole year and repeated up to six times in the same monkey without deteriorating fertilization potential of eggs until a poor response to stimulation happened. Fertilization can be efficiently achieved with both conventional and piezo-driven intracytoplasmic sperm injection procedures. In semen collection, semen quality is higher with the penile robe electrical stimulus method compared with the rectal probe method. Moreover, caesarean section is an effective strategy for increasing baby survival rates of multiple pregnancies. These findings provide a practical guidance for the efficient use of ARTs, facilitating their use in genetic engineering of macaque monkeys for basic and translational neuroscience research.

Transgenic rhesus monkeys produced by gene transfer into early-cleavage-stage embryos using a simian immunodeficiency virus-based vector

The development of transgenic technologies in monkeys is important for creating valuable animal models of human physiology so that the etiology of diseases can be studied and potential therapies for their amelioration may be developed. However, the efficiency of producing transgenic primate animals is presently very low, and there are few reports of success. We have developed an improved methodology for the production of transgenic rhesus monkeys, making use of a simian immunodeficiency virus (SIV)-based vector that encodes EGFP and a protocol for infection of early-cleavage-stage embryos. We show that infection does not alter embryo development. Moreover, the timing of infection, either before or during embryonic genome activation, has no observable effect on the level and stability of transgene expression. Of 70 embryos injected with concentrated virus at the one- to two-cell stage or the four- to eight-cell stage and showing fluorescence, 30 were transferred to surrogate mothers. One transgenic fetus was obtained from a fraternal triple pregnancy. Four infant monkeys were produced from four singleton pregnancies, of which two expressed EGFP throughout the whole body. These results demonstrate the usefulness of SIV-based lentiviral vectors for the generation of transgenic monkeys and improve the efficiency of transgenic technology in nonhuman primates.