Expression analysis of regulatory microRNAs in bovine cumulus oocyte complex and preimplantation embryos

Abstract

MicroRNAs (miRNAs) are small endogenous molecules that are involved in a diverse of cellular process. However, little is known about their abundance in bovine oocytes and their surrounding cumulus cells during oocyte development. To elucidate this situation, we investigated the relative expression pattern of sets of miRNAs between bovine oocyte and the surrounding cumulus cells during in vitro maturation using miRNA polymerase chain reaction (PCR) array. Results revealed that a total of 47 and 51 miRNAs were highly abundant in immature and matured oocytes, respectively, compared with their surrounding cumulus cells. Furthermore, expression analysis of six miRNAs enriched in oocyte miR-205, miR-150, miR-122, miR-96, miR-146a and miR-146b-5p at different maturation times showed a dramatic decrease in abundance from 0 h to 22 h of maturation. The expression of the same miRNAs in preimplantation stage embryos was found to be highly abundant in early stages of embryo development and decreased after the 8-cell stage to the blastocyst stage following a typical maternal transcript profile. Similar results were obtained by localization of miR-205 in preimplantation stage embryos, in which signals were higher up to the 4-cell stage and reduced thereafter. miR-205 and miR-210 were localized in situ in ovarian follicles and revealed a spatio-temporal expression during follicular development. Interestingly, the presence or absence of oocytes or cumulus cells during maturation was found to affect the expression of miRNAs in each of the two cell types. Hence, our results showed the presence of distinct sets of miRNAs in oocytes or cumulus cells and the presence of their dynamic degradation during bovine oocyte maturation.

MicroRNA-378 regulates oocyte maturation via the suppression of aromatase in porcine cumulus cells

“…These findings were supported by a recent in vivo study showing that miR-378 expression in granulosa cells is dependent on the stage of follicular development and is inversely correlated to the levels of estradiol in the follicular fluid (41). The expression of microRNAs in ovarian cumulus cells has been reported recently (1,35); however, the specific roles in this cell type have only begun to be explored. In the current study, we developed a method to overexpress miR-378 exclusively in the cumulus cells of COCs.…”

MicroRNAs in spent blastocyst culture medium are derived from trophectoderm cells and can be explored for human embryo reproductive competence assessment

“…This interaction could determine the establishment of phase synchrony, ultimately aiming to create a hospitable environment for competent embryos at the implantation site, which is a prerequisite for successful implantation. Several studies have already illustrated dynamic changes in miRNA expression in gametes and during early embryonic development of mammalian species (10)(11)(12)(13)(14). Other studies have recently reported that the human endometrial epithelium releases exosomes into the uterine cavity.…”

Efectos de los RNAm maternos sobre la maduración del ovocito y el desarrollo embrionario temprano en mamíferos

“…Dentro los miRNAs que Tesfaye et al (151) encontraron, destacan aquéllos que estando presentes ya desde el ovocito maduro después de la fertilización; permanecen presentes hasta estadios previos a la activación del genoma embrionario; dentro de estos se encuentran el miR-145, miR-208, miR-207 y miR-125a. Aunado a lo anterior, Abd El Naby et al (152) identificaron que los miR-205, miR-150, miR-96, miR-122, miR-146a y miR-146b-5p se expresan de forma constante en el ovocito bovino y su expresión empieza a caer después de 8 h de maduración in vitro de los ovocitos, pero permanecen después de la fertilización hasta los estadios de 4 células, donde empiezan a decaer abruptamente en el estadio de 8 células. En concordancia con esto, Miles et al (153) demostraron que los miR-let7b, miR-let7i y miR106a se expresan de forma específica durante el proceso de maduración de ovocitos bovinos.…”

“…Inside the miRNAs that Tesfaye et al (151) found, are those who being already present from the mature oocyte after fertilization, remain present until stages prior to the activation of the embryonic genome; these include the miR-145, miR-208, miR-207 and miR-125a. Coupled with the above, Abd El Naby et al (152) identified that the miR-205, miR-150, miR-96, miR-122, miR-146a and miR-146b-5p are expressed consistently in the bovine oocyte and its expression begins to fall after 8 h of in vitro maturation of oocytes, but remain after fertilization until the 4-cells stage, where they begin to decline abruptly in the 8-cell stage. Consistent with this, Miles et al (153) showed that the miR-let7b, miR-let7i and miR-106a are expressed specifically during the process of maturation of bovine oocytes.…”