119 QUANTITATIVE PROTEOME ANALYSIS OF ENDOMETRIUM FROM PREGNANT AND NONPREGNANT PIGS

In mammals, an efficient exchange of molecular signals between the embryo and the maternal environment plays a crucial role for the implantation and development of early embryos as well as for recognition and maintenance of pregnancy. So far, only a few molecular signals involved in this process have been identified. To address the underlying biochemical processes in pigs at the protein level, we performed a quantitative proteome study with endometrial tissue samples from non-pregnant and pregnant (Day 14) sows. Endometrium samples (lamina epithelialis, lamina propria and tela submucosa; n = 4 per group) were taken from sites of embryonic attachment and from comparable locations in nonpregnant animals. Proteome data were generated by iTRAQ labelling and nano-LC-MS/MS measurements of tryptic endometrium peptides on a high-resolution Orbitrap XL mass spectrometer. To further address and visualize protein isoforms, LC-MS/MS experiments were complemented by 2D gel-based analyses. To enhance the accuracy of protein quantification, the 2D fluorescence difference gel electrophoresis (2D-DIGE) technique was used, including internal pooled standards for inter-gel matching and normalization. The statistical and bioinformatics analysis of 2D-DIGE and iTRAQ data revealed 14 proteins being significantly altered in abundance (fold-change values >1.5, maximum fold-change 13; P < 0.05) between the endometrium proteomes of pregnant and non-pregnant animals. Several of the affected proteins are already known to play an important role in embryo-maternal communication in other species; for example, signal transducer and activator of transcription 1 (STAT1), a protein mediating the cellular response of cells to interferons (IFN) or aldose reductase (AKR1B1), for which a key role in the synthesis of endometrial prostaglandin F is supposed. Several other proteins showing alterations in abundance between pregnant and nonpregnant endometrial tissues were not described previously and represent new and interesting targets for further functional studies addressing their role during early pregnancy.