Progestin Exposure Before Gonadotropin Stimulation Improves Embryo Development after In Vitro Fertilization in the Domestic Cat1

Abstract

This study investigated the influence of progestin priming and ovarian quiescence on response to exogenous gonadotropin stimulation in the cat. Because a subpopulation of cats routinely ovulated spontaneously, there also was the opportunity to examine the ovary's reaction to the added impact of endogenously secreted progestagen. Queens were given 1) equine chorionic gonadotropin (eCG) plus human chorionic gonadotropin (hCG) only (control; n ¼ 9 cats), 2) GnRH antagonist (antide) injections followed by eCG and hCG (n ¼ 9), and 3) a progestin implant (levonorgestrel) followed by eCG and hCG (n ¼ 9). Laparoscopy was used to assess ovarian activity and aspirate follicular oocytes that were graded on the basis of morphology. In five cats per treatment, half of the high-quality oocytes were assessed for glucose, pyruvate, and lactate metabolism as well as nuclear maturation. Remaining oocytes were inseminated in vitro, cultured, and examined at 72 h after insemination for cleavage. In the remaining four cats per treatment, all oocytes were inseminated in vitro and assessed at 72, 120, and 168 h after insemination for embryo developmental stage. Cats pretreated with progestin had more follicles and produced more embryos per donor (including at the combined morula/blastocyst stage) than controls or females treated with GnRH antagonist (P , 0.05). There were no differences among groups (P . 0.05) in oocyte carbohydrate metabolism, nuclear maturation metrics, or fertilization success, although there was a tendency toward improvements in all three (P , 0.2) in progestin-treated females. Interestingly, cats that spontaneously ovulated within 60 days of treatment onset also produced more embryos per cat than induced-ovulation counterparts (P , 0.05). Results indicate that prior exposure to exogenous progestin (via implant) or endogenous progestagen (via spontaneous ovulation) improves ovarian responsiveness to gonadotropins in the cat through a mechanism that is independent of the induction of ovarian quiescence. embryo, gonadotropin-releasing hormone, oocyte metabolism, ovary, progesterone

The use of altrenogest to avoid hyperestrogenism after eCG-hCG ovulation induction in southern tigrina (Leopardus guttulus)

“…In fact, this mechanism is not completely clear even for the domestic cat, although it has been shown that ovarian quiescence alone is not sufficient to enhance follicular responses to gonadotropins [14]. On the other hand, when quiescence is achieved by synthetic progestin exposure before treatment with gonadotropins, the ovaries appeared to respond more uniformly after ovulation induction, producing higherquality oocytes from more viable follicles in domestic cats [30]. These authors suggested a possible mechanism might include progestin actions at both the organ and cellular level.…”

“…On the ovary, progestins might promote a more efficient recruitment and growth of high-quality oocytes and reduce atresia of antral follicles, assigning a higher number of gonadotropin-receptive follicles [29,30]. At the cellular level, enhancements in follicular granulosa cell gonadotropin receptor populations, whether by increased numbers or enhanced sensitivity, could explain the improved responses to gonadotropins of females previously treated with progestins [29,30]. Further studies are needed to determine if one or both of these mechanisms function in ovarian responses to progestin pretreatment in felids, including in southern tigrinas.…”

“…Pelican et al [30] also showed that ovarian quiescence in response to exogenous progestins resulted in a number of beneficial effects, including increased follicle production, higher-quality oocytes, and more rapidly developing embryos in vitro, which is one more argument in favor of further investigating the use of progestins in AI protocols.…”

Absence of seasonal changes in FSHR gene expression in the cat cumulus–oocyte complex in vivo and in vitro

“…COCs from antral (O2 mm diameter) follicles were harvested 24 h post-hCG by laparoscopic aspiration according to our earlier descriptions (Pelican et al 2010). Recovery medium consisted of HEPES-buffered modified Ham's F10 (Irvine Scientific, Santa Ana, CA, USA) supplemented with 2 mmol/l L-glutamine, 1 mmol/l pyruvate, 100 IU/ml penicillin, 100 mg/ml streptomycin, 0.37 mg/ml heparin (sodium salt Grade 1A), and 4 mg/ml BSA (A9418; Pelican et al 2010, Crosier et al 2011. COCs with an expanded cumulus cell mass were rinsed in nonheparinized collection medium.…”

“…Oocytes were inseminated with conspecific spermatozoa collected, evaluated, and cryopreserved from two colony donors as described previously (Howard et al 1993, Pukazhenthi et al 1999. A 10 ml aliquot of 2!10 6 thawed and motile spermatozoa per milliliter was added to each 40 ml insemination drop (Spindler & Wildt 1999, Comizzoli et al 2003, Spindler et al 2006, Pelican et al 2010. To control for parthenogenetic activation, some drops were shaminseminated using 10 ml of sperm-free insemination medium (Comizzoli et al 2004).…”