Differential expression of genes linked to the leukemia inhibitor factor signaling pathway during the estrus cycle and early pregnancy in the porcine endometrium

Allogeneic Embryos Disregulate Leukemia Inhibitory Factor (LIF) and Its Receptor in the Porcine Endometrium During Implantation

Despite its advantages for pig breeding, embryo transfer (ET) has a major handicap: high embryo mortality during the pre- and implantation period, probably caused by divergent phenomena of tolerance between the immunologically unrelated (i.e., allogeneic) embryos and the recipient sow. Thus, to reach a similar maternal tolerance as in conventional breeding by artificial insemination (AI) would be the key to ET-success. For this reason, we studied the expression of the leukemia inhibitory factor (LIF) cytokine and its receptor in the pig endometrium during the implantation period (days 18 and 24) in sows subjected to ET (AL group) vs. post-cervical-AI controls (Hemi-AL group). Quantification of expression was performed at both mRNA (rt-qPCR) and protein (WB) levels. The expression of endometrial LIF on day 24 was considerably lower in ET than in AI pregnancies. Correlations between endometrial mRNA levels of LIF and LIF-R showed that, contrary to early AI-pregnancies, ET-pregnancies lack an inverse relation between cytokine and receptor levels. In conclusion, ET-pregnancies lack sufficient endometrial levels of LIF to develop adequate immunotolerance mechanisms to prevent the rejection of allogeneic ET-embryos.

lncRNA/mRNA profiling of endometriosis rat uterine tissues during the implantation window

Endometriosis is associated with changes in long non-coding RNA (lncRNA) and mRNA expression, but the exact changes during the implantation window are unknown. Therefore, this study aimed to explore the lncRNA and mRNA expression profiles in the uterus of rats with endometriosis during the implantation window. A total of 35 non-pregnant female rats were randomized to the endometriosis (n=13), adipose tissue control (n=8) and blank control (n=14) groups. On the 5th day of pregnancy, the rats were sacrificed to obtain uterine tissues. lncRNA and mRNA were analyzed using gene chips. A total of five differentially expressed lncRNA and four mRNA were validated by reverse transcription-quantitative (RT-q)PCR. Immunohistochemistry and western blotting were used to determine the expression of the ADAM metal-lopeptidase with thrombospondin type 1 motif 7 (Adamts7), tumor protein p53 (Tp53), distal-less homeobox 3 (Dlx3) and pyrimidinergic receptor P2Y6 (P2ry6) proteins. There were 115 upregulated lncRNAs, 51 downregulated lncRNAs, 97 upregulated mRNAs and 85 downregulated mRNAs in the endometriosis group. RT-qPCR confirmed the trends for five lncRNAs and four mRNAs (Adamts7, Tp53, Dlx3 and P2ry6). The relative protein expression levels of Adamts7, P2ry6, Dlx3 and TP53 were significantly different in the endometriosis group (P<0.05 vs. controls). Bioinformatics predicted the co-expression relationship of the selected five lncRNA and four mRNA. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes predicted that Adamts7, P2ry6, Dlx3 and TP53 were involved in endometriosis-related inflammation and reproductive pathways. In conclusion, the changes in the expression of lncRNAs, mRNAs and proteins (Adamts7, P2ry6, Dlx3 and TP53) may possibly affect endometrial receptivity in rats with endometriosis during the implantation window, probably resulting in implantation failure of the embryo.

Annexin A8 (ANXA8) regulates proliferation of porcine endometrial cells via Akt signalling pathway

Annexin A8 (ANXA8) gene, a member of the annexin family, encodes an anticoagulant protein involved in blood coagulation cascade and acts as an indirect inhibitor of the thromboplastin-specific complex. However, little is known about the function of ANXA8 in porcine endometrial cells so far. Here, ANXA8 mRNA was found to be abundant in porcine endometrium on days 11-13 of pregnancy. Real-time RT-PCR analysis indicated that the mRNA expression of the leukaemia inhibitory factor (LIF) and the epidermal growth factor (EGF) was upregulated by ANXA8 in porcine endometrial cells. Immunofluorescence technology and cell cycle analysis revealed that ANXA8 promoted the proliferation of endometrial cells, as evidenced by the abundant proliferating cell nuclear antigen (PCNA) expression and an increase in the S phase. Western blot analysis results indicated that ANXA8 activated the phosphorylation of the target protein kinase B (Akt) protein. Immunofluorescence technology results showed that the PCNA protein had no significant change in porcine endometrial cells with both ANXA8 overexpression and the addition of Akt inhibitor. Furthermore, the number of implantation sites was significantly reduced by injection of mus-siRNA-ANXA8 into the uterine horn of mice. Collectively, these results suggest that ANXA8 promotes the proliferation of endometrial cells through the Akt signalling pathway.

Leukemia inhibitory factor and its receptor: expression and regulation in the porcine endometrium throughout the estrous cycle and pregnancy

Objective

Leukemia inhibitory factor (LIF) binds to a heterodimeric receptor composed of LIF receptor (LIFR) and glycoprotein 130 (GP130) to transmit signals into the cell. LIF plays an important role in reproduction by regulating immune response, decidualization, and implantation in several species. However, the expression of LIF and LIFR in the endometrium throughout the estrous cycle and pregnancy in pigs is not fully understood.

Methods

We analyzed the expression of LIF and LIFR in the endometrium on days 0 (estrus), 3, 6, 9, 12, 15, and 18 of the estrous cycle, and days 12, 15, 30, 60, 90, and 114 of pregnancy, in conceptuses on days 12 and 15, and in chorioallantoic tissues on days 30, 60, 90, and 114 of pregnancy in pigs. We also determined the effects of estrogen and progesterone on the expression of LIF and LIFR in endometrial tissues.

Results

The expression of LIF increased in the endometrium during the late diestrus phase of the estrous cycle and during mid- to late- pregnancy, while the expression of LIFR increased during early pregnancy. The expression of LIF was induced by increasing doses of estrogen, whereas the expression of LIFR was induced by increasing doses of progesterone.

Conclusion

These results indicate that the expression of LIF and its receptor LIFR in the endometrium is regulated in a stage-specific manner during the estrous cycle and pregnancy, suggesting that LIF and its receptor signaling system may play critical roles in regulating endometrial function in pigs.

MicroRNAome of porcine conceptuses and trophoblasts: expression profile of micrornas and their potential to regulate genes crucial for establishment of pregnancy

Tightly coordinated, reciprocal embryo-maternal interactions affect gene expression during early pregnancy. Recently, microRNAs (miRNAs) have emerged as new players in the fine tuning of embryo development and implantation in mammals via posttranscriptional gene regulation mechanisms. Here, we integrated transcriptomic and computational approaches to profile miRNAs and miRNA synthesis and transport-related genes at different developmental stages of porcine conceptuses and trophoblast during early pregnancy in the pig. Using semiquantitative RT-PCR, we examined mRNA levels of 10 genes encoding proteins involved in miRNA synthesis and transport: DROSHA, DGCR8, XPO5, DICER1, TARBP2, TNRC6A, AGO1, AGO2, AGO3, and AGO4. Custom, multispecies microarrays were used to profile miRNAs. Prediction algorithms of miRNA-mRNA interactions allowed identification of target transcripts for the analyzed miRNAs. These included VEGF, LIF, PTGS2, and IL-6R, known to be crucial components of embryo-maternal interactions in the pig. Two selected miRNAs, miR-26a and miR-125b, were tested for the presence in the extracellular vesicles isolated from uterine luminal flushings during pregnancy. Results of in vitro study demonstrated that miRNAs, such as miR-125b, can regulate expression of genes crucial for embryo development and implantation in porcine endometrial luminal epithelial cells. For the first time, expression profiles of miRNAs and related genes in porcine conceptuses and trophoblast during maternal recognition of pregnancy and embryo implantation in the pig were described. Altogether, our results indicate potential roles of these small, noncoding RNAs in the early development of embryos and embryo-maternal cross-talk during early pregnancy in the pig.