Deep anestrous mares under natural photoperiod treated with recombinant equine FSH (reFSH) and LH (reLH) have fertile ovulations and become pregnant

Superovulation, embryo recovery, and pregnancy rates from seasonally anovulatory donor mares treated with recombinant equine FSH (reFSH)

The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July-August in Argentina, South America) forty light breed donor mares, presenting follicles <10 mm in diameter and no CL at ultrasound examination (deep-anestrus), were randomly assigned (n = 10/group) to one of the following treatments: Group 1: twice daily intramuscular (IM) injections of 0.65 mg reFSH (AspenBio Pharma, CO), Group 2: once daily IM injection of 1.3 mg reFSH, Group 3: twice daily IM injection of 0.32 mg reFSH, and Group 4: once daily IM injection of saline (control). Treatment was administered until a follicle of 35 mm was observed or for a total period of 10 days. When the largest follicle reached ≥35 mm in diameter, treatment was discontinued and 2500 IU hCG was injected intravenously (IV) 36 h later. Mares receiving hCG were inseminated with fresh semen every 48 h until ovulation(s) were detected or one dose of frozen semen (250 × 10⁶ motile sperm) after the first ovulation was detected. Eight days after first ovulation, transcervical embryo recovery was performed. Recovered embryos were non-surgically transferred to anovulatory estrogen/progesterone treated recipients and pregnancy diagnosed by ultrasonography 7, 14 and 21 days later. All mares receiving reFSH, but none receiving saline control, responded to the treatment with follicular growth. On average, 6.5 days of reFSH treatment were required for mares to develop follicles of ovulatory size (>35 mm). Ovulations were detected in 80% of mares in Groups 1 and 2, 50% of mares in Group 3 and in none of Group 4 (Control). Among ovulating mares, no differences in number of ovulations, number of embryos recovered, or pregnancy rates were observed among reFSH treatments. Of treated mares, 6, 7, and 5 produced embryos in Groups 1, 2, and 3, respectively. The average embryo recovery rate per ovulated mare was 88%. The average embryo recovery rate per ovulation was 43%. Overall, a 59% pregnancy rate was achieved. These results indicate that treatment with reFSH during deep anestrus results in follicular development, ovulation of fertile oocytes, and production of embryos that established viable pregnancies after transfer. Also, a single daily administration of reFSH was as effective as two daily administrations, which allows for a simplified administration regimen.

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.