Different pattern of interleukin-1β-(IL-1β), interleukin-1 receptor antagonist- (IL-1ra) and interleukin-1 receptor type I-(IL-1R tI) mRNA-expression in single preimplantation mouse embryos at various developmental stages

The interleukin-1 (IL-1) system has been shown to play an important role in human and murine embryo implantation. Recent studies have documented immunohistochemical evidence of interleukin-1β (IL-1β), interleukin-1 receptor antagonist (IL-1ra) and interleukin-1 receptor type I (IL-1R tI) in human preimplantation embryos and protein levels of interleukin-1α (IL-1α), IL-1β and IL1ra in human preimplantation embryo culture fluid have been correlated with successful implantation and pregnancy. Our aim in this study was to detect IL-1β, IL-1ra and IL-1R tI mRNA in single preimplantation mouse embryos and to describe the frequency of positive mRNA-expression at different developmental stages. B6C3F1-mice, 12 weeks old were pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-stimulated and mated. Animals were sacrificed at day 0.5, and zygotes were flushed from the tubes and cultured in HAMs-F10 medium. 2-cell- (2C-), 8-cell- (8C-), morula- (M-), early blastocyst- (EB-) and hatching blastocyst- (HB-) stage embryos were examined by one round of reverse transcriptase (RT) followed by two rounds of polymerase chain reaction (PCR) carried out on individual mouse embryos for β-actin (internal standard), IL-1β, IL-1ra and IL-1R tl-mRNAs. The frequencies of positive mRNA-expressions were as follows (2C/8C/M/EB/HB); β-actin: 91/96/100/100/98%; IL-1b: 0/0/2.5/6.25/19; IL-1ra; 0/5/30/41/74% and IL-1R tI: 0/0/10/20/25%. The incidence of IL-1ra mRNA expression increased with developmental stage. IL-1ra mRNA seems to be expressed in a very high percentage (74%) of embryos near the time of implantation, whereas the percentage of IL-1β-mRNA positive embryos is surprisingly low (19%).