118 COMPARISON OF TRANSCRIPTOME PROFILES FROM ENDOMETRIAL CARUNCLES AND PERIPHERAL BLOOD MONONUCLEAR CELLS REVEAL COMMON AND TISSUE-SPECIFIC BIOLOGICAL PROCESSES REGULATED AT IMPLANTATION IN SHEEP

Abstract

In mammals, implantation is associated with major changes in gene profiles in the female reproductive tract. Molecular signatures of the endometrium have also been shown to vary according to the ability of the embryo to develop to term. Nevertheless, analysing endometrial gene patterns during implantation is incompatible with the maintenance of pregnancy. Therefore early determination of pregnancy issue requires a noninvasive method. Peripheral blood mononuclear cells (PBMC) could represent such an alternative but their reaction to the presence of an implanting embryo has to be investigated. The aim of this study was to investigate gene expression profiles of endometrial caruncular tissue (CAR) and PBMC collected from pregnant ewes (n = 4) and nonpregnant ewes inseminated with inactivated sperm (n = 4) at Day 15 after oestrus. Differentially expressed genes (DEG) were identified using an ovine custom-designed array derived from the ovine 15K Agilent array (Ruscanu et al. 2013 J. Virol. 87, 9333–9343). Data were normalized by Loess and analysed by a linear model in the Limma R package. P-values were corrected using the Benjamini and Hochberg procedure. Comparing pregnancy versus nonpregnancy led to the identification of 2826 DEG in CAR (P < 0.05) and 396 DEG in PBMC (P < 0.10; 265 DEG common with CAR). Ingenuity Pathway Analysis (IPA; Ingenuity Inc., Mountain View, CA, USA) analysis of the 396 PBMC-related DEG revealed 72 overrepresented biological functions (P < 0.001). Among the 15 most overrepresented functions, 13 were common between CAR and PBMC and were mostly related to the immune system, as “infectious disease”, “cell-to-cell signalling and interaction”, “immunological disease”, “immune cell trafficking and inflammatory response”. Using the downstream effect analysis (DEA) of IPA, we identified 163 functions predicted to be increased and 8 functions predicted to be decreased for the CAR DEG dataset, whereas 12 functions were predicted to be increased and 40 functions predicted to be decreased for the PBMC DEG dataset. Interferon (IFN) signalling was strongly present in both datasets, with 44% of PBMC DEG and 29% of CAR DEG found to be related to IFN type I response according to the Interferome database (www.interferome.org). A selection of 12 DEG was validated by qRT-PCR in CAR, intercaruncular areas, and PBMC using 8 pregnant and various groups of nonpregnant ewes (n = 7–9/group). Our data show that PBMC transcriptome is influenced by early pregnancy in sheep, including a major impact of IFN type I such as IFN tau, the signal of maternal recognition of pregnancy. Identifying relevant circulating biomarkers reflecting the quality of the embryo will require further investigation.

The authors thank UCEA team (INRA), B. Jost (IGBMC) and F. Moreews (Sigenae).