RESUMO
The objective of this work was to determine if specific circulating microRNA (miRNA) differed due to pregnancy status in heifers. Blood samples were collected from heifers 21 d after receiving an in vitro-produced embryo. Pregnancy status was diagnosed 21 d after embryo transfer, equivalent to day 28 of gestation, with rectal ultrasonography. Blood samples from 10 pregnant and 10 nonpregnant heifers were then evaluated for miRNA expression. There were five different miRNAs quantified using delta-delta Ct and qPCR methodology. These miRNAs had previously been associated with early pregnancy in cattle. The miRNA Let-7d-5p was decreased in nonpregnant as compared to pregnant females (P < 0.05). There were no changes in 16-5p, 16-1-3p, 16-2-3p, and 26a-5p associated with pregnancy (P > 0.05). Results demonstrate an opportunity to identify and study the differential expression of miRNAs from the blood of pregnant cows. The Let-7d-5p miRNA is a potential early pregnancy marker and is critical to better understand the early relationships of the cellular and molecular interactions of the cow and embryo.
MicroRNAs are critical molecules in cell homeostasis and can bind their target in the cellular cytoplasm by miRNA recognition of the 3ʹUTR sequence in the messenger RNA (mRNA) or other RNAs and inhibiting the mRNA translation. This molecular mechanism is called gene silencing. These miRNAs are stable in blood and can be useful as biomarkers of early pregnancy in the bovine. We demonstrated a decrease in the miRNAs, Let-7d-5p, at day 21 post embryo transfer for nonpregnant samples contrasted with pregnant blood samples (P < 0.05). This research opens new methodologies to study and understand miRNAs circulating in blood of pregnant vs. nonpregnant cows at early stages.
