Role of Endometrial Factors in Regulating Secretion of Components of the Immunoreactive Human Embryonic Interleukin-1 System during Embryonic Development1

Abstract

In the study reported here, we localized at the protein level the major components of the interleukin (IL)-1 system in the human embryo, and we investigated the endometrial factors influencing their secretion during embryonic development. To localize these components, we performed immunohistochemical experiments in 44 oocytes and 78 embryos. The following primary antibodies were used: monoclonal mouse anti-human IL-1 receptor type I (IL-1R tl), monoclonal mouse anti-human IL-1 beta, and polyclonal rabbit anti-human IL-1 receptor antagonist (IL-1ra). For embryo culture, human embryos at different developmental stages were cultured in 100-microliters drops of Ham's F-10 medium + 4 mg/ml BSA (n = 33), in 100-microliters drops of Menezo B2 culture medium (n = 18), or in wells with 1 ml of Menezo B2 culture medium (n = 8). For embryo coculture, endometrial stromal cells (ESC) and endometrial epithelial cells (EEC) were isolated from human secretory endometrium and cultured until confluence in 75% Dulbecco's Modified Eagle's Medium and 25% MCDB-105 containing antibiotics and supplemented with 10% charcoal-Dextran-treated fetal bovine serum. Individual human embryos were cocultured with experimental EEC and ESC (n = 23 and n = 4, respectively) for 5 days in 600-microliters drops of Menezo B2 medium, and conditioned medium was removed every 24 h. Human embryos were also cultured with EEC-conditioned medium (n = 9). IL-1 alpha, IL-1 beta, and IL-1ra levels were determined by ELISA in the 24-h culture- or coculture-conditioned media. Immunostaining confirmed the presence of IL-1 beta, IL-1ra, and IL-1R tl in oocytes and embryos in all stages analyzed, with no statistical differences. IL-1 alpha, IL-1 beta, and IL-1ra were absent in conditioned media of cultured embryos and embryos cocultured with ESC. However, when human embryos were cocultured with EEC or with EEC-conditioned medium alone, two different populations of embryos were observed: IL-1 producers (57% and 56%) and IL-1 nonproducers (43% and 44%, respectively). Finally, the IL-1 profile of a single human embryo cocultured with maternal EEC which successfully implanted and developed is presented, this pattern being similar to that described in the IL-1 producer population. These results demonstrate the presence of the IL-1 system in the human embryo. However, the selective release of IL-1 only when embryos were cocultured with EEC or EEC-conditioned medium indicates an obligatory role of the endometrium in the regulation of the embryonic IL-1 system. Furthermore, the differential embryonic production of IL-1 may be related to the implantation capability of the embryos.

Involvement of Interleukin-1 and the Interleukin-1 Receptor Antagonist in In Vitro Embryo Development Among Women Undergoing In Vitro Fertilization–Embryo Transfer

“…Del los Santos et al have also found that antagonism of IL-1 activity by IL-1ra in early embryo development appears to be beneficial (9). Del los Santos demonstrated in a single embryo that developed into a blastocyst that antagonism of the IL-1 system occurred with development of the embryo (i.e., the IL-1α+IL-1β/IL-1ra decreased as the embryo progressed from the 4-cell to the blastocyst stage).…”

“…IL-1 receptors are located on the early human embryo (3)(4)(5)(6). Thus, there exists the potential for interactions between serum IL-1 with the early embryo.…”

Hsa-miR-30d, secreted by the human endometrium, is taken up by the pre-implantation embryo and might modify its transcriptome

“…During the implantation process, the blastocyst regulates the expression and secretion of integrins β3, α4 and α1 (Simón et al, 1997), the interleukin-1 (IL-1) system (De los Santos et al, 1996), chemokines IL-8, MCP-1 and RANTES (CaballeroCampo et al, 2002), leptin (Cervero et al, 2004;González et al, 2000) and hCG (Licht et al, 2001;Paiva et al, 2011) by the endometrial epithelium during the window of implantation (WOI), the period when the endometrium is receptive to a blastocyst. The EF, a viscous fluid secreted by the endometrial glands into the uterine cavity, nurtures the embryo and constitutes the microenvironment in which the first bidirectional dialogue between the maternal endometrium and the embryo occurs during the WOI (Cha et al, 2012(Cha et al, , 2013Thouas et al, 2014;Tranguch et al, 2005).…”

Molecular mechanisms of membrane interaction at implantation

“…Moreover, embryo-derived interleukin-1 (IL-1) can initiate the up-regulation of epithelial avb3 at the specific site of embryo attachment. In vitro experiments showed that IL-1 was secreted only when embryos were cocultured with endometrial epithelial cells, and that once secreted, IL-1 bound and activated endometrial IL-1 receptor type I (De los Santos et al, 1996;Simon et al, 1997, Van Sinderen et al, 2013. The consensus of opinion, therefore, is that IL-1 may function as a paracrine factor, to regulate avb3 in the endometrial epithelium during implantation.…”