In vivo and in vitro effects of interleukin-1beta on equine oocyte maturation and on steroidogenesis and prostaglandin synthesis in granulosa and cumulus cells.
Résumé
We analysed the effect of interleukin-1 on oocyte maturation and on steroid and prostaglandin production by equine granulosa and cumulus cells. In Experiment 1, interleukin-1 beta (IL-1 beta) was injected into the growing dominant follicle, which was punctured 38 h later. Follicular fluid was assayed for steroids and prostaglandin-F2 alpha (PGF2 alpha). Granulosa cells were analysed for 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), progesterone receptor (PR), cyclooxygenase 1 and 2 (Cox 1 and Cox 2) and steroidogenic acute regulatory protein (StAR) mRNAs. In Experiment 2, cumulus-oocyte complexes (COCs) were collected from slaughterhouse ovaries and cultured in different media: control group (TCM199+BSA); Group 2 (+IL-1 beta); Group 3 (+EGF); Group 4 (+EGF+IL-1 beta); and Group 5 (+EGF+IL-1 beta+IL-1RA). Cumulus cells were analysed for 3 beta-HSD, PR, Cox 1, Cox 2 and StAR mRNAs. After injections of crude equine gonadotropin (CEG; LH effect) or IL-1 beta, progesterone and PGF2a levels increased, whereas 17 beta-oestradiol decreased. EGF induced an increase in the rate of in vitro maturation (P < 0.05), whereas IL-1 beta had a limited effect. IL-1 beta significantly decreased the rate of EGF-induced oocyte maturation (P < 0.05). Cox 2 mRNA level increases in granulosa cells after CEG injection (P = 0.07). In cumulus cells, StAR and PR mRNAs were lower in Group 2 and 3 beta-HSD mRNA was higher in Groups 4 and 5. These data confirm that IL-1 is involved in equine oocyte in vitro maturation. We demonstrated in vivo that IL-1 beta has an effect on steroids and PGF2 alpha secretion in the preovulatory follicle.