Azkargorta M, et al. - Researchers investigated the difference, if any, in the protein composition of the endometrial fluid aspirate (EFA) obtained the day of embryo transfer in in vitro fertilization (IVF) cycles achieving and not achieving pregnancy. In implantative and non-implantative IVF cycles, findings revealed the existence of a differential protein expression pattern in the comparative analysis.

Methods

• From a total of 110 women undergoing IVF (corresponding to 50 implantative and 60 non-implantative IVF cycles), EFA was analyzed for the differences in the protein expression patterns.
• Researchers used a high-throughput differential proteomic approach to analyze the Discovery (38 patients) and Validation (42 patients) sample cohorts.
• In an additional cohort of 30 patients, they validated the differential expression of glycogen phosphorylase B (PYGB) by western blotting.
• The study was conducted for a period of 18 months.
• The study population was comprised of 110 women aged 18–40 years old, undergoing their first or second IVF/ intracytoplasmic sperm injection cycle, with normal uterus and endometrium, and 1–2 good quality embryos, and embryo transfer being performed on Day 3.
• They performed endometrial fluid aspiration immediately before the embryo transfer.
• They initially divided the samples (80) into two independent cohorts and used liquid chromatography–mass spectrometry to perform the analysis.
• They used the first cohort for the discovery and the second for the validation of the results.
• For the in-solution tryptic digestion of the proteins present in the samples, they used filter-aided sample preparation, it was followed by label-free mass spectrometry analysis.
• Using different bioinformatic tools, including GSEA, IPA and GO analysis, they thoroughly analyzed the lists of differential proteins to unravel the molecular features of receptivity.

Results

• In order to strengthen the reliability of the results, researchers carried out a false discovery rate-based correction of the t-test P-values.
• The deregulation of important processes governing receptivity, such as antimicrobial response, cell–cell interaction, immune response and inflammatory signaling, among others, were noted via functional analyses.
• Overall, there were eight proteins that were commonly deregulated in both studied datasets and for confirmatory analysis, brain form glycogen phosphorylase (PYGB) was selected.