In vivo and in vitro effects of interleukin-1beta on equine oocyte maturation and on steroidogenesis and prostaglandin synthesis in granulosa and cumulus cells.

The researchers investigated the impact of a cellular signaler, interleukin-1, on the maturation of oocytes and the production of certain chemicals by two types of cells in horse ovaries: granulosa and cumulus cells. Their findings confirmed that interleukin-1 plays a role in oocyte maturation and influences the production of other hormones.

Experiments and Procedures

• The paper discusses two main experiments. In the first experiment, interleukin-1beta was directly introduced into a growing ovary follicle in a horse, which was later sampled. The follicular fluid was analyzed for content of steroids and prostaglandin-F2alpha. The granulosa cells were analyzed for presence and quantity of various proteins.
• In the second experiment, they cultured cumulus-oocyte complexes (COCs) from horse ovaries in different media groups. Each group had a different combination of factors added to it, including interleukin-1, EGF (epidermal growth factor) and IL-1RA (a blocker of interleukin-1). The researchers then examined the levels of specific proteins in the cumulus cells.

Main Findings

• Overall, they found that after introduction of either crude equine gonadotropin (a luteinising hormone) or interleukin-1beta, the levels of progesterone and prostaglandin F2-alpha increased, while the levels of estradiol decreased.
• In the second experiment, the researchers found that EGF increased the rate of in vitro (outside the body) maturation, while interleukin-1beta had only a limited effect on this. Interestingly, interleukin-1beta also reduced the EGF-induced maturation rate.
• Expression of certain proteins changed in response to the different factors. For instance, the level of Cox 2 mRNA increased in granulosa cells after administration of equine gonadotropin. In cumulus cells, the expressions of StAR and PR proteins decreased in group 2, while 3beta-HSD protein expression increased in groups 4 and 5.

Conclusions

• The findings confirm the involvement of interleukin-1 (as IL-1beta) in the maturation process of horse oocytes. Furthermore, the researchers demonstrated in vivo (inside the body) that IL-1beta affects the secretion of steroids and prostaglandin F2-alpha in the preovulatory follicle, having an impact on fertility and reproduction.