Dynamic changes in ovarian follicles measured by ultrasonography during gonadotropin stimulation in rhesus monkeys

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.

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.

Non-invasive translational Cynomolgus model for studying folliculogenesis and ovulation using color Doppler ultrasonography

BACKGROUND

In women, different events of folliculogenesis can be measured and evaluated using ultrasound (US) technology. The availability of a non-invasive translational non-human primate model to study these processes would represent a major contribution to further advance R&D efforts toward novel therapies in assisted reproduction.

METHODS

In our study, follicular growth and ovulation was measured in six cyclic Cynomolgus monkeys using abdominal Doppler US.

RESULTS

The mean follicular diameter on cycle day -6 (cycle day 0=day of ovulation) was 3.7mm that increased to 6.8mm on cycle day -1. After ovulation, the mean diameter decreased to 4.6mm, confirming ovulation. The mean percentage of follicular size reduction after ovulation was 31%.

CONCLUSION

Ultrasonography in combination with color-flow Doppler imaging was shown to be a useful, non-invasive translational method to measure ovarian follicular growth and occurrence and timing of follicular rupture in Cynomolgus monkeys.