Purpose: To assess whether there are proteins in endometrial fluid aspirate (EFA) that predict implantation.
Methods: The population under study consisted of 285 women undergoing embryo transfer (ET). Endometrial fluid aspiration was performed immediately before ET. Results of proteomic analysis of EFA were compared between 33 cases who achieved pregnancy and 33 who did not. Samples were analysed by 2D electrophoresis and mass spectrometry. Blood samples were studied by ELISA Pregnancy rates and maternal complications were compared to those in women refusing aspiration.
Results: We found 23 proteins differentially expressed in the EFA in conception cycles: 4 up-regulated proteins and 19 down-regulated (FC = 0.31 0.78) (among others, arginase-1, actin B, PARK-7, cofilin-1, stathmin, annexin-2 and CAPZB). Among the five studied proteins that were differentially expressed in EFA, none was differentially expressed in serum. The aspiration procedure had no impact on pregnancy rate. No maternal complications were reported.
Conclusions: We found a very different protein profile in implantative cycles, the majority of proteins being down-regulated. This probably reflects a different endometrial functional status, more favourable to implantation. EFA proteomic analysis could be a useful tool in the planning ET strategies.
Keywords: Endometrial fluid; Endometrium; IVF; Implantation; Proteomics.