In vivo effect of interleukin-1beta and interleukin-1RA on oocyte cytoplasmic maturation, ovulation, and early embryonic development in the mare

In recent years, evidence has accumulated to suggest that cytokines are important regulators of the ovarian function. Interleukin-1 (IL-1), one major cytokine, as well as receptors (IL-1R1 and IL-1R2) and antagonist (IL-1RA) have been demonstrated to be produced in the ovary of several species [1, for review]. Recently, we demonstrated the presence of IL-1β mRNA in equine cumulus-oocyte complexes and granulosa cells, whereas immunoreactive IL-1β has been observed in equine follicular fluids [2,3].In vitro studies have shown that IL-1β regulates some cellular activities of granulosa and theca cells, such as steroidogenesis [4,5], as well as synthesis of proteases [6-8] and prostaglandins [9,10]. Moreover, it has been demonstrated that IL-1β promotes the ovulation process in the rat [11], the rabbit [12] and the mare [13]. IL-1β increases in vitro the germinal vesicle breakdown of oocytes in the rabbit model [12], as well as in vivo in the mare [13], demonstrating a beneficial role of IL-1β in oocyte nuclear maturation. These observations led to conclude that IL-1 may be a paracrine factor that is involved in ovulation and in oocyte nuclear maturation. In 1994, Takehara et al., demonstrated that IL-1β can facilitate in vitro fertilization in the rabbit, suggesting that IL-1 may be involved in oocyte cytoplasmic maturation and could improve fertilization. In the mare, no data is available on the effect of IL-1β on oocyte cytoplasmic maturation or fertilization rates. Nevertheless, a better knowledge of regulating factors involved in these processes would help to improve the embryo production in this species.In this context, the objectives of the present study were to investigate in vivo in the mare, the potential role of IL-1β on oocyte cytoplasmic maturation, ovulation and embryo development.All animal procedures were approved by the Agricultural Agency and Scientific Research Agency (approval number A37801) and conducted in accordance with guidelines for Care and Use