Optimization of superovulation induction by human menopausal gonadotropin in guinea pigs based on follicular waves and FSH‐receptor homologies

Abstract

The guinea pig represents an excellent animal model for the study of reproduction in humans and most domestic animals because unlike the mouse and rat, it undergoes a complete estrous cycle. In this study, we investigated the availability of ovarian oocytes during the estrous cycle, and the follicle stimulating hormone (FSH) receptor (FSH-R) homologies between guinea pigs and other species, in order to identify an effective gonadotropin and optimal time-of-application for the induction of superovulation in the guinea pig. The number of collectable ovarian oocytes showed biphasic changes with peaks at the midluteal and pre-ovulatory stages. On the other hand, the number of oocytes that matured in vitro remained constant ( approximately 10 oocytes) until day 14 post-ovulation and increased thereafter. The deduced amino acid sequence of the guinea pig FSH-R showed greater similarity to the primate FSH-R than to the rodent FSH-R, which suggests that commercially available human menopausal gonadotropin (hMG) may be a better inducer of superovulation in guinea pigs. Indeed, significantly more oocytes (5.4 +/- 1.6, range 0-17, n = 10) were obtained from hMG-treated guinea pigs at the pre-ovulatory stage than during spontaneous ovulation (3.6 +/- 0.1, n = 96; P < 0.05), whereas guinea pigs that received hMG at the midluteal stage (n = 3) did not ovulate. These results indicate that hMG is an effective, albeit stage-dependent, inducer of superovulation in the guinea pig, and that FSH-R homologies should be taken into account when choosing hormones for superovulation.

Morphologic observation and classification criteria of atretic follicles in guinea pigs

“…The guinea pig is an excellent animal model for studies of the reproductive system in humans and most domestic animals (Suzuki et al, 2003). Unlike other laboratorial rodents, guinea pigs have an extended estrous cycle of 16 to 18 d (Joshi et al, 1973;Trewin et al, 1998), cannot be superovulated by follicle-stimulating hormone (FSH) or equine chorionic gonadotropin (eCG) but rather with inhibin immunizations (Shi et al, 2000a), and have a full gestation of 68 d and a small litter size of 3.8 on average (van Kan et al, 2009).…”

Cell proliferation and apoptosis in the fetal and neonatal ovary of guinea pigs

“…The guinea pig is an excellent animal model for studies of the reproductive system of adult humans and most domestic animals (Suzuki et al, 2003). In mice and rats, comparable studies have revealed that follicular formation and development are initiated after birth (McGee and Hsueh, 2000).…”

“…Guinea pigs, unlike other rodents, i.e., rats, mice and hamsters, exhibit follicular formation and development in utero before birth, and thus have a long gestation period of approximately 70 days, similar to that of large animals (Shi et al, 1999;Suzuki et al, 2003;Sadeu et al, 2007). During pregnancy, fetal ovarian development begins with primordial germ cells (PGCs) migrating to and invading embryonic gonads, followed by primordial follicle assembly and development at different time points (Loffler and Koopman, 2002;Suh et al, 2002;Sawyer et al, 2002).…”

Induction of follicular luteinization by equine chorionic gonadotropin in cyclic guinea pigs

“…Exogenous gonadotropins, such as folliclestimulating hormone (FSH), luteinizing hormone (LH), equine chorionic gonadotropin (eCG), and human menopausal gonadotropin (hMG), can successfully induce superovulation in most mammalian species (Hudson et al, 1999;Miller et al, 1999;Singh and Madan, 1999;Suzuki et al, 2003;Brooke et al, 2007). Specifically, eCG or FSH can induce superovulation in rats (Popova et al, 2002), pigs (Manjarin et al, 2009), sheep (Cognie, 1999), and cattle (Small et al, 2009).…”

“…Guinea pigs, only ovulate a few oocytes (3.6±0.1) in one typical estrous cycle (Suzuki et al, 1993), and the majority of follicles are lost by atresia (Hermreck and Greenwald, 1964) in the four continuous stages (Wang et al, 2010b). Gonadotropins do not always reliably induce superovulation in guinea pigs (Suzuki et al, 2003), and the mechanism of ovulation remains poorly understood. Thus, to elucidate the ovarian response to gonadotropins in guinea pigs, we investigated follicular processes after administration of eCG.…”