Endocrine Abstracts

Successful implantation requires the synchronisation of viable embryonic development with endometrial receptivity. The mechanisms allowing for the initiation of crosstalk remain elusive, however recent studies have revealed alterations in endometrial microRNAs (miRs) in women suffering repeated implantation failure (RIF). We hypothesised that the IGF1 receptor (IGF1R) is involved in implantation, and that miR145, which is elevated in RIF endometrium and predicted to target IGF1R, influences epithelial receptivity. We have used an in vitro model to study the effect of miR145 on IGF1R expression and early implantation events.

Overexpression of miR-145 in Ishikawa cells reduced the level of IGF1R protein (western blotting), but not mRNA (RT-qPCR). 3′UTR luciferase reporter assays demonstrated that miR-145 directly regulates IGF1R mRNA.

Mouse embryos co-cultured with Ishikawa cells were observed to attach over a period of 24 h. Stability of attachment was impaired upon overexpression of miR-145 or specific reduction of IGF1R (siRNA).

To demonstrate functional IGF1R at the cell surface, we transferred embryo-sized beads coated with IGF1 to cell monolayers and observed attachment. Knockdown of IGF1R decreased the interaction, demonstrating receptor specificity. Similarly, impaired attachment was observed after miR-145 overexpression.

To determine if IGF1R mediates the functional effect of miR-145 overexpression on attachment, we prevented the interaction between miR-145 and IGF1R using miR-target protectors, and reversed the effect of miR-145 overexpression.

The data show that miR-145 influences embryo attachment by regulating IGF1R in endometrial epithelial cells, suggesting the two have opposing effects in regulating implantation.