GnRH agonist Lupron® (leuprolide acetate) pre-treatments prevent ovulation in response to gonadotropin stimulation in the clouded leopard (Neofelis nebulosa)

Reproductive biology and biotechnologies in wild felids

Conservation strategies in natural habitats as well as in breeding centers are necessary for maintaining and reinforcing viable populations of wild felids. Among the fundamental knowledge that is required for conservation breeding, a solid understanding of reproductive biology is critical for improving natural breeding and enhance genetic diversity. Additionally, it offers the opportunity to develop assisted reproductive technologies (ARTs) in threatened and endangered species. Conservation breeding and reproductive biotechnologies of wild felids have advanced in the past decade. It has been clearly shown that female felids have species and individual patterns of reproductive cycles and respond differently to exogenous hormones. In males, several species still have poor semen quality often due to the loss of genetic diversity in small populations. To overcome the challenges of natural breeding (incompatibility between individuals or suboptimal environment) and mitigate inbreeding, artificial insemination, embryo production and embryo transfer have been further developed in 24 wild cat species. Major factors limiting ART success are inconsistent responses to ovarian stimulation, variable quality of gametes and embryos, and preparation of recipient females. Additional approaches including stem cell technologies have been explored for future medical applications. However, there still is a critical need for better knowledge of feline reproductive biology and improvement of ARTs efficiency to increase the genetic diversity and create sustainable populations of wild felids.

Induction of synchronous oestrus but not ovulation after pre-treatment with the GnRH agonist, Lucrin® Depot, in the tammar wallaby

We investigated the capacity for pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) to induce synchronous oestrus and ovulation in the tammar wallaby (Notamacropus eugenii) after follicular suppression with Lucrin® Depot, a one-month GnRH agonist. On Day 0 pouch young were removed (RPY) to reactivate a normal oestrous cycle and then two groups were treated with vehicle (Control; n = 5 and Superovulation (SOvn); n = 5) and two groups were treated with 7.5 mg of Lucrin Depot (Lucrin; n = 6; Lucrin+SOvn, n = 6). On Day 20 RPY the SOvn and Lucrin+SOvn Group received 20 IU of PMSG, which was followed on Day 23 RPY with 500 IU of hCG. The Lucrin+SOvn females underwent a more synchronous oestrus with 5 of 6 mating on Day 26 RPY while the SOvn (n = 5/5) and Control (n = 5/5) Groups copulated over two days, between Day 25-27 RPY and Day 27-29 RPY respectively. Mating plugs were not detected in any of the females in the Lucrin Group by Day 31 RPY. Autopsy on Day 31 RPY confirmed all females in each treatment group had undergone a reactivated cycle as evidenced by the presence of a large corpus luteum (CL) in one ovary. At autopsy the females in the Lucrin+SOvn Group had highly stimulated reproductive tracts, and their ovaries contained many follicles >3 mm; 14 ± 2.1 and 15.3 ± 2.1 follicles >3 mm in the CL-bearing ovary and contralateral ovary respectively. Similarly, females in the SOvn Group had 11.4 ± 2.4 and 17.4 ± 1.9 follicles >3 mm in each respective ovary. Uterine flushing and ovarian histology confirmed that females in Lucrin+SOvn and SOvn Groups had not ovulated, but normal oocytes were present in the follicles. By comparison, the Control Group had ovulated with a single embryo being recovered from the uterus of 4 of 5 females. In contrast to all groups, females in the Lucrin Group showed follicular suppression (all follicles <1.5 mm) and an unstimulated reproductive tract. We conclude that a suppression plus stimulation regimen using Lucrin Depot followed by PMSG and hCG has the capacity to synchronise oestrus, and that 20 IU of PMSG stimulates the development of antral follicles >3 mm in both ovaries. However, a single 500 IU treatment of hCG on Day 23 RPY was not able to induce ovulation in the tammar wallaby.

Insulin promotes preantral follicle growth and antrum formation through temporal expression of genes regulating steroidogenesis and water transport in the cat

The aims of the present study were to determine the effects of insulin, invitro, on: (1) the viability and growth of domestic cat ovarian follicles; (2) mRNA expression of genes regulating steroidogenesis (cytochrome P450 family 17 subfamily, A polypeptide 1 (Cyp17a1), cytochrome P450 family 19 subfamily, A polypeptide 1 (Cyp19a1) and steroidogenic acute regulatory protein (Star)) and water transport (aquaporins (AQPs) Aqp1, Aqp3, Aqp7, Aqp9); and (3) steroid production (17β-oestradiol (E2), progesterone (P4), androstenedione (A4)). Cat secondary follicles were isolated from ovarian cortices and cultured in 0 (Control), 1 or 10µgmL-1 insulin for 14 days (Day 0=culture onset). Follicle and oocyte viability (based on neutral red staining), diameter and antrum formation were assessed every 72h and at the end of incubation (Day 14). Expression of steroidogenic and water transport genes was evaluated on Days 0, 6 and 12, and E2, P4 and A4 concentrations in the culture medium were determined on Day 12. By Day 14, 1 and 10µgmL-1 insulin had significantly promoted (P<0.05) both antrum formation in a mean (±s.e.m.) 26.9±9.0% and 78.0±10.0% of follicles respectively, and follicle growth (diameter 151.4±4.5 and 169.9±10.5µm respectively) compared with Control (antrum formation in 3.3±3.3% of follicles and follicle diameter 129.1±6.6µm). High insulin (10µgmL-1) treatment increased follicle viability compared with Control (86.0±9.8% vs 38.1±10.9% respectively; P<0.05). However, insulin had no beneficial effect (P>0.05) on oocyte diameter. Cyp17a1 expression on Days 6 and 12 was higher (P<0.05) in follicles cultured in the low (1µgmL-1) compared with high (10µgmL-1) insulin treatment, with no significant difference between low or high insulin vs Control groups. Star expression was higher (P<0.01) in the low insulin compared with Control group on Day 6, but Star was undetectable in the high insulin group by Day 12. Compared with high insulin, low insulin increased (P<0.05) Aqp1 expression on Day 6, but there were no significant differences between these two groups on Day 12. In contrast, high insulin decreased (P<0.05) Aqp9 transcript levels compared with Control. Only P4 production was affected by insulin, with P4 concentrations in the medium being higher (P<0.05) in the low compared with high insulin and Control groups. In summary, the findings indicate that insulin promotes cat ovarian follicle growth and survival invitro, including enhanced antrum formation, with the likely mechanism involving temporal expression of Cyp17a1, Star and Aqp9 genes.

GnRH-agonist implants suppress reproductive function and affects ovarian LHR and FSHR expression in prepubertal female cats

Effect of a GnRH-agonist (deslorelin) was studied on reproductive function and ovarian luteinizing hormone receptor (LHR) and follicle stimulating hormone receptor (FSHR) expression in prepubertal female cats that were either implanted with 4.7-mg deslorelin (implanted: n = 6) or not (controls: n = 18) or ovariohysterectomized at prepubertal age (prepubertal OVH: n = 6). Body weights, fecal estradiol, and sexual behavior of implanted and control cats were monitored for 48 weeks followed by collection of ovaries and uteri. Ovaries and uteri were collected from control cats at follicular, luteal, and inactive stage (n = 6/group) and from prepubertal OVH cats at prepubertal age. Ovaries and uteri were analyzed for anatomical/histological characteristics. Ovaries were also analyzed for LHR and FSHR expression. Statistical analysis showed higher (P ≤ 0.05) body weight in control than implanted cats only during 22nd to 26th weeks of the study. Estrus was observed in control cats only. Deslorelin reduced (P ≤ 0.05) ovarian weight and number of antral follicles but did not affect endometrial thickness and gland diameter. However, myometrial thickness of implanted cats was significantly lower than control cats at follicular and luteal stage. Ovarian LHR mRNA expression was lower (P ≤ 0.05) in implanted cats than control cats at follicular stage. FSHR mRNA and LHR protein expression did not differ among the three groups. FSHR protein expression was lower (P ≤ 0.05) in prepubertal OVH cats and was not affected by deslorelin. In conclusion, deslorelin suppresses reproductive function in prepubertal female cats for at least 48 weeks possibly through a change in the ovarian mRNA expression of LHR.

Effect of deslorelin acetate treatment in oocyte recovery and in vitro embryo production in domestic cats

Objectives The present study investigated the effect of contraceptive treatment with deslorelin acetate on in vitro embryo production and oocyte recovery in domestic queens. Methods Twenty-one mature domestic cats were used. Eleven queens (treated group) and one tom were kept in an experimental cattery, and 10 queens were privately owned (control group). When in interestrus or diestrus (day 0) a deslorelin acetate implant (Suprelorin, 4.7 mg/animal) was inserted into the subcutaneous tissue of the interscapular region in all queens in the treated group. After 6 months of treatment, all animals were ovariohysterectomized, and the ovaries were used for in vitro embryo production. Percentage of cleavage was determined 18 h after oocyte insemination and blastocyst formation was assessed on the eighth day of culture. The rate of cumulus-oocyte complexes (COCs) recovery was analyzed by an unpaired t-test. The cleavage and blastocyst rates were expressed as percentages and analyzed by Fisher's exact test. All analyses were performed using GraphPad Prism v5.0, with P <0.05 set as the level of significance. Results In the treated group, we recovered 8.3 ± 1.15 grade I COCs per queen; the cleavage rate was 60% and the blastocyst rate was 36%. In the control group, we recovered 18.4 ± 3.21 grade I COCs per queen; the cleavage rate was 55.97% and the blastocyst rate was 34%. Forty percent of treated females did not produce any blastocysts. In the treated group, we observed a significant decrease in COC recovery. Although there was no significant difference in cleavage and blastocyst rates between groups, 40% of treated females did not produce any blastocysts. Conclusions Recovery of grade I COCs is negatively affected by deslorelin treatment in domestic cats. Regarding embryo production, new studies are still necessary to evaluate the success of this technique owing to the individual effect caused by deslorelin acetate.

Investigational hormone receptor agonists as ongoing female contraception: a focus on selective progesterone receptor modulators in early clinical development

INTRODUCTION

As efforts are made to continue to increase the safety of contraceptive methods, those without estrogen have attracted new attention. Progestin-only options are available in many delivery systems, but most cause disturbed bleeding patterns. For gynecologic patients, selective progesterone receptor modulators (SPRMs) have been approved for medical abortion, for ovulation suppression in emergency contraception, and for the treatment of heavy menstrual bleeding due to leiomyoma.

AREAS COVERED

This article discusses the role of SPRMs in controlling fertility on an ongoing basis with particular emphasis on mifepristone and ulipristal acetate (UPA), since none of the other compounds has progressed out of early Phase I - II testing. It also discusses important information about the mechanisms of action and safety of these two SPRMs.

EXPERT OPINION

Of all the investigational hormone agonist/antagonists, SPRMs have demonstrated the greatest potential as ongoing female contraceptives. They have the ability to suppress ovulation after initiation of the luteinizing hormone (LH) surge without affecting ovarian production of estrogen or inducing any significant metabolic changes. SPRMs may well be able to provide longer term contraception as oral agents, vaginal rings, and perhaps even intrauterine devices. UPA has the greatest promise. Current research needs to be expanded.

Estrus induction and synchronization in canids and felids

Indications for estrus induction in the dog and cat include potential missed breeding opportunities or conception failure, the treatment of primary or secondary anestrus, out-of-season breeding (feline) and synchronization of ovulation for embryo transfer programs. Reported methods for estrus induction in bitches and queens include the use of synthetic estrogens (diethylstilbesterol), dopamine agonists (bromocriptine and cabergoline), GnRH agonists (lutrelin, buserelin, fertirelin, deslorelin, and leuprolide), exogenous gonadotropins (LH, FSH, hCG, PMSG, and human menopausal gonadotropin) and opiate antagonists (naloxone). These methods vary widely in efficacy of inducing estrus as well as in the fertility of the induced estrus. The applicability of some of these methods for clinical practice is questionable. This review will summarize published reports on estrus induction in canids and felids, both wild and domestic, and provide an update on research using a long-acting injectable deslorelin preparation in bitches.