MicroRNAome of Porcine Conceptuses and Trophoblasts: Expression Profile of microRNAs and Their Potential to Regulate Genes Crucial for Establishment of Pregnancy1

Abstract

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.

Implantation and Establishment of Pregnancy in the Pig

“…Changes in endometrial transcriptome during early stages of conceptus attachment to uterine LE are just beginning to widen our understanding of the critical factors involved with establishment and maintenance of pregnancy in the pig (Samborski et al 2013 ;Chen et al 2015 ;Kiewisz et al 2014 ). The emergence of microRNAs as posttranscriptional players in regulating gene function has added a new area of investigation to enhance understanding of conceptus-endometrial interactions (Krawczynski et al 2015 ). Utilization of CRISPR technology will now allow knockout of select genes in research to determine the network of endometrial and conceptus factors, such as estrogen and IL1B2, that are critical for establishment of pregnancy.…”

Extracellular Vesicles: Decoding a New Language for Cellular Communication in Early Embryonic Development

“…This suggests that embryos can create their own niche in vitro , by releasing intercellular communication factors that enhance survival (Paria and Dey, 1990; Wydooghe et al, 2015). In this context, a variety of cultured embryos (porcine, bovine, human, rabbit) secrete particular miRNAs whose presence has been consistently associated with embryonic robustness, and could be used as biomarkers for embryonic quality (Berardi et al, 2012; Goossens et al, 2013; Maraghechi et al, 2013; Kropp et al, 2014; Rosenbluth et al, 2014; Krawczynski et al, 2015; Liu et al, 2015). …”

Placentation, maternal–fetal interface, and conceptus loss in swine

“…Many miRNAs and their pregnancy specific roles have since been identified in many species, including pigs [70][71][72]. MicroRNAs have been reported to affect many reproductive parameters in pigs including oocyte and embryo development [73][74][75], implantation and placentation [43,75] [77] and litter size [78]. Recently, our group has investigated the Tristetraprolin family (TIS11/TTP) of RNA-binding proteins which have been found to bind to pro-and antiinflammatory cytokines, notably TNF-α, IFN-γ and granulocyte macrophage colony stimulating factor (GM-CSF) to mediate their degradation [79].…”

“…The second wave occurs around mid-gestation (gd50 to 70 of the 114 day porcine gestation). During this period, increased fetal growth may result in some conceptus 75 attachment sites (CAS) exceeding their uterine space and ultimately ending up with conceptus arrest [10][11][12]. Although fetal loss in pig pregnancy has been a topic of interest for last two decades, the contributing causes to porcine spontaneous conceptus loss are still not well understood.…”