Differences in Gene Expression Profiles between the chorion-attached and non-chorion-attached endometrium at the mid-gestation of female rabbit
The placenta, the complex of fetal membrane (the chorion is attached to the endometrium) and endometrium, is a highly specialized temporary organ responsible for the normal progression of pregnancy in mammals. Therefore, the endometrium was divided into two function regions: chorion-attached (CA) and non-chorion-attached (NCA) region. However, the difference in gene expression profiles between the CA and NCA endometrial tissue of mid-gestation still are unknown. The objective of this study was to reveal gene expressed profiles of the CA and NCA endometrium from the mid-gestational female rabbits, and to screen the differentially expressed genes (DEGs) to imply major physiological events of endometrial at mid-gestation. RNA-seq showed that a total of 12320 genes were co-expressed in the CA and NCA endometrium, and 646 DEGs were identified. Enrichment analysis of the DEGs revealed the top overrepresented gene ontology (GO) term and pathways were related to immune regulation, cellular adhesions. Furthermore, the expression levels of DEGs related to immune regulation of chemokines and their receptors, extracellular matrix (ECM) and Integrin, were compared between the CA and NCA endometrium. Overall, there was hardly difference in the expression levels of immune regulation genes (chemokines and their receptors) between the CA and NCA endometrium, while the concentration of IL-8, IL-6 and IL-1ß in the CA endometrium was higher than that in the serum and the NCA endometrium, which suggested immune cytokines were accumulated in the endometrium of maternal-fetal interface. Meanwhile, the expression level of genes related to cellular adhesions (ECM-integrin) in the NCA endometrium was significantly higher than that in the CA endometrium, and high abundance of Integrin ß and THBS1 were localized in the luminal epithelium of the NCA endometrium, but not in the CA endometrium. Conclusions: Our study revealed the gene expression profiles of the CA and the NCA endometrium at mid-gestation, and provides an implication of chemokine and ECM-Integrin involved in immune regulation and adhesive barrier at the endometrium. Overall design: Three sexually mature female rabbits (2.50 ± 0.15kg) underwent synchronous estrus processing followed by mating. On the 14th day of gestation, samples from the uterine endometrial tissue and placenta, together with the junction of the allantochorial membrane and endometrium  were collected and stored in liquid nitrogen. Sampling accuracy was evaluated by hematoxylin-eosin staining. Transcriptomics analysis was performed by PTM Biolab Ltd. Co. (Hangzhou, China). Animals were housed in individual cages under a 14-h light and 10-h dark regimen at a temperature of 16°C to 25°C, and fed ad libitum on a standard diet. All experimental procedures were approved by the Animal Ethics Monitoring Committee of Sichuan Agricultural University and carried out in accordance with the Guidelines of Animal Welfare in China.