A preliminary study on the use of a long-acting GnRH agonist prior to ovarian stimulation for oocyte retrieval in the western lowland gorilla

Birth of a western lowland gorilla (Gorilla gorilla gorilla) following in vitro fertilization and embryo transfer

A 21-year-old multiparous female exhibiting 31-41 day menstrual cycles was given hFSH (225 IU/day, Metrodin 75, from cycle day 3 through 9 (menses = day 1) and hCG (10,000 IU, Profasi, on day 10 to stimulate follicular development. At 35 h after hCG, under isoflurane (AErrane) anesthesia, follicles were aspirated by controlled suction under transvaginal ultrasound guidance. Metaphase II oocytes (n = 11) were placed in modified human tubal fluid (mHTF, 100 microliters) medium under oil at 37 degrees C in humidified 5% CO2. Frozen semen, collected by voluntary ejaculation, was thawed (70 degrees C H2O bath, 6 sec), diluted slowly, centrifuged, and resuspended in mHTF, and 160,000 motile spermatozoa/ml were added at 6 h after oocyte recovery. At 21 h postinsemination (p.i.) eight oocytes were at the two-cell stage, five were cryopreserved, and three were cultured to the six- to eight-cell stage in mHTF with granulosa cells before transcervical uterine transfer at 47 h p.i. using a Teflon catheter. Micronized progesterone (400 mg/d) was orally administered for 10 weeks posttransfer (p.t.). Ultrasound examination revealed a single fetus at 15 weeks p.t., and unassisted delivery of a live 1.37 kg female infant occurred at 29 weeks. Am. J. Primatol. 41:247-260, 1997.

Strategies for ovulation induction and oocyte retrieval in the lowland gorilla

PURPOSE

Ovulation induction and oocyte retrieval were performed in a lowland gorilla in an attempt to propagate and potentially cryopreserve embryos from an infertile animal and to advance techniques to help preserve this endangered species.

RESULTS

Following 34 days of leuprolide acetate suppression, human menopausal gonadotropins were administered for 14-days in a 32-year-old wild-born lowland gorilla. Ten oocytes were retrieved by transrectal ultrasound-guided aspiration. Other approaches to oocyte recovery were not feasible in this case. A serum estradiol concentration of 4700 pg/ml at the time of human chorionic gonadotropin administration did not induce ovarian hyperstimulation. Mature oocytes were recovered from follicles measuring 14 to 24 mm in diameter, with a corresponding average serum estradiol concentration of approximately 300 pg/ml for each mature follicle. Cryopreservation of a gorilla embryo was effected from cryopreserved gorilla spermatozoa.

CONCLUSIONS

Parameters for monitoring ovulation induction in the gorilla appear to be similar to those for humans. The results indicate that the use of a gonadotropin releasing hormone agonist and higher doses of gonadotropins than previously used in gorillas appear to improve oocyte recovery.

In vitro fertilization and gamete micromanipulation in the lowland gorilla

PURPOSE

Our purpose was to utilize current reproductive technologies to treat an infertile female lowland gorilla.

RESULTS

Following pituitary down-regulation with a gonadotropin releasing hormone agonist and follicular stimulation with human menopausal gonadotropins, transrectal ultrasound-guided aspiration of ovarian follicles yielded nine oocytes. Following failed fertilization with both epididymal and electroejaculated sperm, zona dissection and sperm injection were performed and produced one embryo, which was cryopreserved. Immature oocytes were obtained from ovarian sections and were either cultured in vitro or cryopreserved.

CONCLUSIONS

This report demonstrates that in vitro fertilization techniques, including pituitary suppression, ultrasound-guided aspiration, micromanipulation, and cryopreservation, can be used to assist reproduction in the lowland gorilla.

Hemizona assay for measuring zona binding in the lowland gorilla

The hemizona assay is a diagnostic test used to evaluate the binding potential of spermatozoa to zonae pellucida and has been used to predict fertilization potential in the human. In this study, frozen-thawed gorilla spermatozoa were coincubated with human hemizonae to evaluate tight binding and to assess the use of human zonae in evaluating sperm fertility. Matching hemizonae were incubated with human sperm to serve as a control. For evaluation of binding studies in a homologous system, matching halves of gorilla hemizonae were coincubated with both gorilla and human sperm. Whole, intact zonae of both human and gorilla oocytes were also coincubated with heterologous sperm to determine if penetration into the perivitelline space could occur. This study found that gorilla sperm bound well to both gorilla and human hemizonae, with a mean of 112.5 and 81.0 tightly bound sperm, respectively. Human sperm also bound to gorilla (mean 229.5) and human (mean 236.5) hemizonae. Following incubation with intact gorilla zonae, motile human sperm were found within the perivitelline space. However, gorilla sperm were not visible within the perivitelline space of nonviable human oocytes. These findings demonstrate that the zonae of nonviable human oocytes can be used to assess sperm binding of gorilla sperm. Studies continue for optimizing assay condition and correlation of findings with the fertility potential of gorilla sperm.