124 CHANGES IN GENE EXPRESSION FOLLOWING EXPOSURE OF BOVINE ENDOMETRIAL EPITHELIAL CELLS (bEEC) TO ESCHERICHIA COLI LPS; THEIR POSSIBLE EFFECT ON IMPLANTATION

Abstract

Lipopolysaccharide (LPS) is a component of the outer membrane of gram-negative bacteria and is involved in postpartum uterine infection in cattle. Lipopolysaccharide causes inflammation of the endometrium and the activation of immune and pro-inflammatory pathways in uterine cells has been well documented. This study was performed to investigate the effects of LPS on epithelial cells from whole-genome information, and this abstract focuses on genes and pathways involved in the regulation of implantation. Following in vitro culture of bovine endometrial epithelial cells (bEEC), passage 4 epithelial cell samples from 3 cows were exposed to 0, 2, and 8 µg mL⁻¹ LPS (Sigma L2630, Escherichia coli O111:B4, Sigma Chemical Co., St. Louis, MO, USA) for 24 h. At time 0 and at 24 h for each LPS dosage, RNA was extracted by using the All prep DNA/RNA Universal kit (Qiagen, Valencia, CA, USA). Samples were analysed by RNA sequencing performed in the SciLife Laboratory in Uppsala. Differentially expressed genes (DEG) were identified by using Ensemble genes as a reference. No DEG were found between 2 and 8 µg mL⁻¹ LPS-treated samples and at 24 h 2035 DEG were identified (Benjamini-Hochberg adjusted P-value < 0.05) between controls and samples treated with 2 µg mL⁻¹ LPS. Gene ontology analysis did show that DEG were associated to immune response (up), response to stress and external stimuli (up), catalytic activity (up), cell cycle, anatomical structures especially cell membrane, and adhesion (down) pathways. In the latest, numerous specific genes in relation with implantation were highly deregulated. This includes down-regulation of 8 members of the cadherin superfamily. On the contrary, 4 members of the mucin family were strongly up-regulated by LPS (MUC1, MUC13, MUC16, F1MUC1). Molecules such as plakophilins and desmogleins involved in desmosomes, in tight junctions, and in the control of cell adhesion were also deregulated. Specific changes occurred in immune response related with implantation [strong up-regulation of the immunoglobulin superfamily members such ICAM1 (or CD54) and down-regulation of ALCAM]. A set of 10 molecules belonging to the family of integrins and their binding partners were also deregulated [for instance, down-regulation of osteopontin (SPP1)]. In addition, LPS deregulated a large set of genes binding the above molecules (such as galectins LGALS1, S3, S9) and more than 20 transcripts coding for cytokines and their receptors. A large series of interferon-induced genes (IFITS) and genes coding for interferon-induced trans membrane proteins (IFITM) were highly up-regulated by LPS. This may be of functional importance due to the fact that all those genes are normally up-regulated by interferon tau from embryonic origin. The above results show that the function of endometrial epithelial cells is profoundly affected by LPS and that most of the key signals involved in implantation are deregulated. It is likely that these LPS-induced changes strongly perturb lately endometrial responsiveness to embryos at the time of implantation.

Research was done with the financial support of FP7 project “Prolific” and RMUTSV (Thailand).