OR36-4 miR-145 influences embryo implantation by regulating endometrial IGF1R expression

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: OR36-Ovarian & Uterine Function
Monday, June 17, 2013: 11:15 AM-12:45 PM
Presentation Start Time: 12:00 PM
Room 104 (Moscone Center)
Youn-Jung Kang1, Karen Forbes*2 and John D Aplin2
1University of Oxford, Oxford, United Kingdom, 2University of Manchester, Manchester, United Kingdom
Implantation defects are a major cause of infertility. In-vitro fertilisation (IVF) can help to overcome this problem in some women, however implantation success rates after IVF still only lie at around 30%. It is estimated that up to two-thirds of repeated implantation failures (RIF) are due to defects in endometrial receptivity, so increased understanding of the mechanisms that regulate interaction of the embryo with the endometrium is required. Growth factors produced by the embryo, including IGF-I, are known to influence embryo development, but the molecules responsible for appropriate endometrial receptivity remain to be established. Some microRNAs (miRs), including miR-145, are upregulated in the endometrium of women with RIF, suggesting a role in regulating receptivity. In this study we investigated the role of miR-145 in regulating embryo/endometrial interaction.

To overcome difficulties associated with investigating implantation in vivo, we utilised two in vitro models: mouse embryos, and a model in which the implanting embryo is replaced by embryo-sized beads (Affi-gel Blue; Bio-rad; 80–150μm). Beads preloaded with IGF-I (100ng/ml;2h) were transferred to human endometrial epithelial Ishikawa cells (as a model of the uterine luminal epithelium). Both mouse embryos and ligand-conjugated beads (but not control beads) attached to the apical surface of confluent cells. To examine whether miR-145 could influence this process, Ishikawa cells were transfected with a synthetic pre-miR-145 mimetic (100 nM) or negative control pre-miR for 48 h. Attachment of IGF-bearing beads or embryos was monitored microscopically and quantified using a stability scale. Embryos or IGF-I-loaded beads reached 70% on the scale when cells had been transfected with negative control pre-miR, but following miR-145-overexpression, the stability of embryos or beads was reduced by at least 80% relative to control. To explore the mechanism further, we investigated the gene targets of miR-145. Western blot analysis revealed that miR-145 overexpression decreased IGF1R expression to 14% of control.  IGF1R knockdown reduced bead attachment stability to 11% of the control level.

In summary, by utilising two novel in-vitro models of implantation,  we have begun to dissect the molecular mechanisms regulating embryo-endometrial attachement. Using this model we have revealed that IGF1R is a critical component within the endometrium that is required for successful implantation. Furthermore, IGF1R expression is closely regulated by miR-145. We hypothesise that miR-145 overexpression causes infertility by blocking embryo (IGF-I)–maternal (IGF1R) interactions at implantation.

Nothing to Disclose: YJK, KF, JDA

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: KF is supported by a University of Manchester Stepping Stone Fellowship