Department of Animal Sciences, University of Wisconsin-Madison Madison, WI, USA ; Department of Obstetrics and Gynecology, University of Wisconsin-Madison Madison, WI, USA.
Department of Obstetrics and Gynecology, University of Wisconsin-Madison Madison, WI, USA.
Front Genet. 2014 Apr 24;5:91. doi: 10.3389/fgene.2014.00091. eCollection 2014.
MicroRNAs (miRNA) are short non-coding RNAs which act to regulate expression of genes driving numerous cellular processes. These RNAs are secreted within exosomes from cells into the extracellular environment where they may act as signaling molecules. In addition, they are relatively stable and are specifically expressed in association to certain cancers making them strong candidates as biological markers. Moreover, miRNAs have been detected in body fluids including urine, milk, saliva, semen, and blood plasma. However, it is unknown whether they are secreted by embryonic cells into the culture media. Given that miRNAs are expressed throughout embryonic cellular divisions and embryonic genome activation, we hypothesized that they are secreted from the embryo into the extracellular environment and may play a role in the developmental competence of bovine embryos. To test this hypothesis, bovine embryos were cultured individually from day 5 to day 8 of development in an in vitro fertilization system and gene expression of 5 miRNAs was analyzed in both embryos and culture media. Differential miRNA gene expression was observed between embryos that developed to the blastocyst stage and those that failed to develop from the morula to blastocyst stage, deemed degenerate embryos. MiR-25, miR-302c, miR-196a2, and miR-181a expression was found to be higher in degenerate embryos compared to blastocyst embryos. Interestingly, these miRNAs were also found to be expressed in the culture media of both bovine and human pre-implantation embryos. Overall, our results show for the first time that miRNAs are secreted from pre-implantation embryos into culture media and that miRNA expression may correlate with developmental competence of the embryo. Expression of miRNAs in in vitro culture media could allow for the development of biological markers for selection of better quality embryos and for subsequent successful pregnancy.
微小 RNA（miRNA）是一种短的非编码 RNA，可调节驱动多种细胞过程的基因表达。这些 RNA 从细胞内的外泌体中分泌到细胞外环境中，在那里它们可能作为信号分子发挥作用。此外，它们相对稳定，并且与某些癌症特异性表达，使它们成为生物标志物的有力候选物。此外，已经在包括尿液、牛奶、唾液、精液和血浆在内的体液中检测到 miRNAs。然而，尚不清楚它们是否由胚胎细胞分泌到培养基中。鉴于 miRNA 在整个胚胎细胞分裂和胚胎基因组激活过程中表达，我们假设它们是从胚胎分泌到细胞外环境中的，并且可能在牛胚胎的发育能力中发挥作用。为了验证这一假设，我们在体外受精系统中从第 5 天到第 8 天对牛胚胎进行了单独培养，并分析了胚胎和培养基中 5 种 miRNA 的基因表达。在发育到囊胚阶段的胚胎和未能从桑葚胚发育到囊胚阶段的胚胎（称为退化胚胎）之间观察到差异表达的 miRNA 基因。与囊胚胚胎相比，退化胚胎中 miR-25、miR-302c、miR-196a2 和 miR-181a 的表达更高。有趣的是，这些 miRNA 也在牛和人着床前胚胎的培养基中表达。总的来说，我们的研究结果首次表明，miRNA 从着床前胚胎分泌到培养基中，并且 miRNA 表达可能与胚胎的发育能力相关。miRNA 在体外培养物中的表达可能为选择质量更好的胚胎和随后成功妊娠开发生物标志物。
