Interleukin-1 receptor antagonist prevents embryonic implantation by a direct effect on the endometrial epithelium  Carlos Simón, M.D., Diana Valbuena, M.D., Jan Krüssel, M.D., Alejandra Bernal, Ph.D., Christopher R Murphy, Ph.D., Tim Shaw, Ph.D., Antonio Pellicer, M.D., Mary Lake Polan, M.D., Ph.D.  Fertility and Sterility  Volume 70, Issue 5, Pages 896-906 (November 1998) DOI: 10.1016/S0015-0282(98)00275-1

FIGURE 1 Mouse blastocysts obtained after uterine flushing on day 8 of pregnancy. Nonpregnant uteri from IL-1ra–injected and noninjected animals were flushed. (A), A total of 32 morphologically normal-appearing blastocysts at different stages (early, expanded, and hatched) were recovered from the IL-1ra–treated group. (B), Only three blastocysts were obtained from the noninjected group. Note that the trophoectoderm appears darker, spherical, and retracted, with no surrounding zona pellucida. Fertility and Sterility 1998 70, 896-906DOI: (10.1016/S0015-0282(98)00275-1)

FIGURE 2 Pregnancies obtained after transfer of delayed blastocysts to pseudopregnant animals. Six pseudopregnant females had transfer on day 4. Five blastocysts were transferred into each horn. Blastocysts flushed from day-4 pregnant mice were placed in the right uterine horn, and blastocysts flushed from IL-1ra–treated animals at day 8 of pregnancy (Fig. 1) were transferred into the left uterine horn of the same animal. (A), In one of six animals, pregnancy was achieved, as demonstrated by the presence of three gestational sacs at day 19. Two sacs corresponded to blastocysts obtained from IL-1ra–treated animals (left horn) and one sac was derived from normal blastocysts. (B), Embryos obtained from these three gestational sacs were morphologically normal, with cardiac activity at the time of uterine incision. Fertility and Sterility 1998 70, 896-906DOI: (10.1016/S0015-0282(98)00275-1)

FIGURE 3 Indirect immunofluorescence localization of immunoreactive endometrial β3 integrin in response to IL-1ra treatment. (A), Negative control by deletion of the first antibody. (B, C), Mouse uteri obtained at day 8 of pregnancy from noninjected animals. (Original magnifications, ×200 and ×400, respectively.) Moderate staining for β3 is localized in the apical region of the luminal epithelium and stroma. (D, E), Mouse endometrium obtained at day 8 of pregnancy from IL-1ra–injected animals. (Original magnifications, ×200 and ×400, respectively.) Staining for β3 is absent in the endometrial epithelium. (F, G), Mouse uteri obtained at day 8 of pregnancy from IL-1ra + IL-1β–injected animals. (Original magnifications, ×200 and ×400, respectively.) Intense staining is present in the basal region of the endometrial epithelium, with moderate staining throughout the epithelium and stroma. Fertility and Sterility 1998 70, 896-906DOI: (10.1016/S0015-0282(98)00275-1)

FIGURE 4 TEM at day 4 of pregnancy in control animals versus IL-1ra–treated animals. (A), Control uteri (noninjected) generally show a flattened surface profile with irregular flattened projections and a few low microvilli, as is usual on day 4 of pregnancy in the mouse. (B), IL-1ra–injected animals have endometrium with numerous and longer microvilli covering the cell surface, which is characteristic of the early days (days 1–2) of pregnancy. (Original magnification, ×20,000.) Fertility and Sterility 1998 70, 896-906DOI: (10.1016/S0015-0282(98)00275-1)

FIGURE 5 Percentage of positive mRNA expression of α1, α2, α3, α4, α5, α6, αv, β3, and vascular cell adhesion molecule-1 (VCAM-1) in mouse uteri from control and IL-1ra–treated animals. ∗ Statistically significant difference between the groups (P<0.005). Fertility and Sterility 1998 70, 896-906DOI: (10.1016/S0015-0282(98)00275-1)