Reproduction Abstracts

Exosomes are recognized as new mediators of intercellular cell signaling between neighboring cells and distant tissues, acting independently but synergistically with growth factors and hormones. Trophoblast and stromal cells of the villi were identified as a source of exosomal miRNAs released into the maternal circulation. In this study we hypothesized that miRNAs participating in the embryo–maternal dialog are released into the maternal blood stream during early pregnancy in pigs.

From our previous global transcriptomic experiments we selected 11 miRNAs (miR-1, miR-23b, miR-26a, miR-27a, miR-34a, miR-125b, miR-199a-5p, miR-199a-3p, miR-203b, miR-205, miR-302), showing differential expression in embryos/trophoblasts or endometrium, and tested them in maternal serum collected on day 16 of the estrous cycle and pregnancy (n=6/status) using either qRT-PCR and digital RT-PCR. Data were analyzed using PCR Miner and GraphPad Prism.

Among tested miRNAs only three (miR-1, miR-199a-5p, miR-302) were not detected in the maternal serum. qRT-PCR indicated different levels of miR-26a and miR-125b in pregnant and cyclic animals, showing elevated levels during pregnancy (P=0.003 and P=0.006, respectively). Digital RT-PCR analysis allowed detection of 766±159 vs 2057±494 copies/μl of miR-26a (P=0.002) and 2675±556 vs 6068±729 copies/μl of miR-125b (P=0.007) in cyclic and pregnant animals, respectively. Additionally, miR-23b showed increased levels in serum samples of pregnant animals (P=0.006; 151±33 vs 314±32 copies/μl). This data revealed altered profiles of miRNAs in the material circulation on day 16 of pregnancy, suggesting status-dependent release of miRNA into the maternal circulation of the pig. It seems likely that unique set of miRNAs are released into maternal circulation as a consequence of early embryo–maternal communication.