Previous studies in the human suggest that the interleukin-1 (IL-1) system, may be an important paracrine/autocrine mediator in local intercellular interaction in endometrial tissue. In this study we have determined that IL-1 receptor type I (IL-1R tI) is expressed at the messenger RNA (mRNA) and protein levels in glandular cells and its ligand, IL-1 beta has been localized by immunohistochemical methods in endothelial cells and isolated stromal cells in the human endometrium throughout the menstrual cycle. IL-1R tI mRNA was detected in glandular epithelium using both specific complementary DNA and complementary RNA 32P-labeled probes. Human glandular epithelium contains a 5.1-kilobase mRNA transcript throughout the complete menstrual cycle. Quantitative densitometric analysis of slot blot hybridization signals shows an increase of IL-1R tI mRNA in both early and mid-late secretory phases in comparison with the proliferative phase (P < 0.05). IL-1R tI protein was localized in endometrial glandular epithelial cells using both indirect immunofluorescence and avidin-biotin-peroxidase methods. However, more intense staining for IL-1R tI was observed in lumenal epithelial cells compared with the staining present deep in the endometrial glands. Using the same methods, IL-1 beta was detected in endothelial cells of spiral vessels and isolated stromal cells throughout the menstrual cycle, and an increased staining from proliferative to secretory phase was observed. The detection of IL-1R tI in the human endometrial epithelium and its ligand, IL-1 beta, in isolated stromal cells and endothelial cells, is another example of possible communication between the immune and reproductive systems with special relevance to human implantation.

Recent data support a role for apoptosis, under tight regulatory control by bcl-2, oxidative stress response, tumor suppressor, and CASP gene family members, in mediating granulosa cell demise during follicular atresia in the rodent and avian ovary. Herein we evaluated the occurrence of apoptosis in the human and baboon ovary relative to follicular health status, and analyzed expression of several cell death genes in these tissues.

The distribution of immunoreactive interleukin-1 receptor type I (IL-1R tI), IL-1 alpha, and IL-1 beta, and of macrophages, was investigated immunohistochemically in the mouse ovary during follicular growth, ovulation, and luteinization. For this purpose, an indirect immunofluorescence technique, using specific monoclonal antibodies against mouse IL-1R tI, mouse IL-1 alpha, IL-1 beta, and macrophage antigens (CD11b/CD18) was used with sections of paraffin-embedded ovaries from eCG and eCG/hCG-treated 12-wk-old B6C3F-1 female mice. During follicular development, IL-1 alpha, IL-1 beta, and IL-1R tI staining were confined to the theca-interstitial layer of growing follicles with one remarkable exception. Intense IL-1R tI still staining was present in the cytoplasm and plasma membrane of the murine oocyte. During ovulation, IL-1 alpha and IL-1 beta were still confined to the theca layer, but faint IL-1R tI staining was initiated in cumulus cells and in granulosa cells just before follicle rupture. Immediately after follicle rupture, granulosa cells stained positive for IL-1R tI, IL-1 alpha, and IL-1 beta. During luteinization, granulosa-luteal cells of the corpus luteum demonstrated strong IL-1R tI, IL-1 alpha, and IL-1 beta staining. Macrophages were detected in the theca layer and stroma, but never within the follicle before ovulation. Immediately after ovulation, there was a rapid entry of macrophages into the follicle, and macrophages were also present inside the corpus luteum. Our morphological results support a possible autocrine-paracrine role of the mouse ovarian IL-1 system in ovulation and luteinization.

We have investigated the relevance of interleukin-1 receptor type I (IL-1R tI) in the implantation process in vivo in a murine model. Indirect immunofluorescence experiments demonstrate that IL-1R tI is located in mouse endometrial lumenal epithelium with increased intensity in the periimplantation period, whereas IL-1 beta staining is located in the mouse placenta. PMSG/human CG (hCG)-stimulated and mated 12-week-old B6C3F-1 female mice were randomly allocated to three groups: A, control noninjected; B, buffer-injected animals; and C, animals injected ip with 20 micrograms recombinant human IL-1 receptor antagonist (rhIL-1ra) every 12 h beginning on pregnancy day 3. Injections were continued until day 9, and animals were killed 12 h after the last injection. Pregnancy rates in the three groups were: noninjected, 58.8% (10 of 17); buffer-injected, 73.7% (14 of 19); rhIL-1ra-injected, 6.7% (1 of 15), P = 0.0001155, Fisher exact test. To rule out the possibility that pregnancy failure was due to an embryotoxic effect of rhIL-1ra, 2-cell mouse embryos (n = 276) were flushed from the same group of animals used for in vivo experiments and cultured with increasing concentrations of rhIL-1ra: 0 microgram/ml (n = 91), 1 microgram/ml (n = 36), 50 micrograms/ml (n = 36), 100 micrograms/ml (n = 52), and 200 micrograms/ml (n = 61) rhIL-1ra. The percentages of 2-cell mouse embryos reaching the blastocyst stage after 72 h in culture were 85.7%, 91.6%, 94.4%, 96%, and 85.2%, respectively. We further cultured these blastocysts for 5 days on fibronectin-coated plates with or without 200 micrograms/ml rhIL-1ra. In both groups, hatching, attachment to fibronectin, outgrowth, and migration were documented to be similar. Furthermore, our longitudinal morphological study of embryonic implantation in control and rhIL-1ra-injected mice shows that the blockade of IL-1R tI interferes with the attachment of mouse blastocysts to maternal endometrium in vivo. In summary, we demonstrate that blockade of maternal endometrial IL-1R tI with IL-1ra prevents implantation in the mouse by interfering with embryonic attachment, without adverse effects on blastocyst formation, hatching, fibronectin attachment, outgrowth, and migration in vitro.