Proteomic analysis of the human receptive versus non-receptive endometrium using differential in-gel electrophoresis and MALDI-MS unveils stathmin 1 and annexin A2 as differentially regulated.

BACKGROUND The transcriptome of the endometrium throughout the menstrual cycle has been described in recent years. However, the proteomic of the window of implantation remains unknown. The aim of this study was to compare the proteome of the human endometrium in the pre-receptive phase versus the receptive phase by identifying and quantifying the proteins differentially expressed using differential in-gel electrophoresis (DIGE) and mass spectometry (MS). METHODS Endometrial biopsies were collected at days 2 (pre-receptive) and 7 (receptive) after the urinary luteal hormone surge in the same menstrual cycle from eight fertile women (corresponding to days 16 and 21 of the menstrual cycle). Proteins were extracted and labeled with CyDye DIGE fluorofores and separated using two-dimensional gel electrophoresis. RESULTS Image analysis using the DeCyder software followed by protein identification by matrix-assisted laser desorption/ionization-MS and database searching revealed 32 differentially expressed proteins, although only annexin A2 and stathmin 1 were consistently regulated in the two experiments performed. Validation and localization of annexin A2 and stathmin 1 were performed by western blot and immunohistochemistry. Annexin A2 and stathmin 1 were investigated using an endometrial refractoriness model. The results highlight the key potential of these proteins as possible targets for human endometrial receptivity and interception. CONCLUSION This study shows that the human endometrium has a differential proteomic repertoire during the window of implantation. Consequently, we identified annexin A2 and stathmin 1 as differentially expressed molecules in the receptive endometrium.