Oral Presentation Australasian Extracellular Vesicles Conference 2018

New insights into human embryo implantation: Endometrial extracellular vesicles promote trophectoderm functions thus enhancing implantation potential (#24)

Lois Salamonsen 1 , Jemma Evans 1 , Richard Simpson 2 , David Greening 2
  1. Hudson Institute of Medical Research, Melbourne, VIC, Australia
  2. La Trobe Institute for Molecular Sciences, La Trobe University, Melbourne, VIC, Australia

To establish pregnancy, the human embryo enters the uterine cavity as a blastocyst, where its outer cellular layer, the trophectoderm, must first attach to and then traverse the endometrial surface epithelium, before invading through the endometrial stromal compartment and invading the blood vessels, to create the placenta within the first trimester.  The endometrium is only ‘receptive’ to implantation briefly during the mid-secretory progesterone-dominated phase of each menstrual cycle. Uterine fluid provides the microenvironment for implantation: most of its biologically active components arise from the endometrial glands or from the blastocyst itself in a conception cycle. 

We proposed that EVs of endometrial (e) origin, within this microenvironment in women, transfer of eEV cargo to the trophectodermal cells on the blastocyst surface, to improve implantation potential.

We identified/characterized EVs within human uterine fluid, and those derived from the human endometrial luminal epithelial cell line, ECC1.  Importantly, these EVs contained unique cohorts of both miRNA and proteins. Quantitative proteomic analyses demonstrated that hormonal stimuli of ECC1 cells to mimic the normal 28 day menstrual cycle, extensively altered programming of exosome content. While 663 common exosome proteins were identified, a further 254 proteins were packaged specifically under estrogen (E) stimulation and 126 proteins only when progesterone was also present (E+P); 35% (189) of these proteins are endometrial epithelial exosome specific and do not appear in existing exosomal databases.

Functionally, we demonstrated internalization of eEVs by both trophectodermal (TSC) and trophoblast cells (TC). In TC, take of eEVs enhanced their adhesive capacity and this was   significantly higher when the parent endometrial cells were treated with E+P, mimicking receptive endometrium. Both fibronectin and focal adhesion kinase (FAK) pathway members (total FAK and pFAK proteins) were increased in TC following eEV uptake. Importantly, in TSC cells formed into a spheroid of blastocyst size, adhesion, outgrowth and invasive capacity were all significantly increased. Further targeted studies may enable novel nano-diagnostics and nano-therapeutics to improve infertility, pregnancy loss and pre-eclampsia and possibly new methods for contraception.