79 MicroRNAs of extracellular vesicles secreted by embryos as an early biomarker of competence

Extracellular vesicles (EVs), including exosomes and microvesicles, are secreted by different cell types and participate in cellular communication by carrying molecules as microRNAs (miRNAs) that can interfere with gene expression of target cells. Extracellular vesicles have become relevant as a mechanism of embryo-maternal communication. The aim of this study was to evaluate miRNA content in EVs secreted after embryonic genome activation, by bovine embryos with different developmental potential. Bovine embryos were produced invitro and cultured in group until Day 3.5 in synthetic oviductal fluid (SOF) medium. Only 8-16-cell embryos were cultured individually in EVs-depleted SOF until Day 5. The SOF was EV depleted by ultrafiltration. Culture media (CM) were collected at Day 5 and embryos continued in culture until Day 7 with fresh SOF. Collected media were conserved individually and identified with the corresponding embryo. Then, CM were classified according to capacity of its embryo to reach blastocyst stage at Day 7: G1-CM (blocked embryos in 8-16 cell) and G2-CM (embryos that reach blastocyst stage). The EV isolation was carried out using the protocol described by Mellisho et al. (2017). Recovered EVs were evaluated by nanoparticle tracking analysis (NTA), Transmission electron microscopy and the presence of surface markers (CD9, CD63, CD81, and CD40L). After NTA, individual CM were pooled to organise 3 replicates of 10CM each, for G1 and G2. The whole miRNA isolation, library preparation, and sequencing was performed by Norgen Biotek facilities (Canada). The quality of libraries was analysed using the FastQC program platform followed by Trimmomatic to remove remnant adapters. For the miRNA library it accepted reads with value above 30 Phreads and 22 to 30bp length. The reads were mapped against the reference genome ARS-UCD1.2 using Bowtie2 software and miRDeep2 mapper, and the gene counts were calculated using HTSeq. Differential expression analysis was performed in EdgeR package. To expand this information, principal component analysis, Heatmap, and Volcano plot were plotted and pathway enrichment analysis was conducted. The NTA, transmission electron microscopy, and flow cytometry confirmed the presence of exosomes and microvesicles in isolated EVs. According to NTA, the mean size of EVs was 102.1-176.2nm and concentration of 8.4×107-8.6×108 particlesmL−1 in G1 and G2, respectively. We identified 96 miRNAs significantly expressed across the samples. Only eight miRNAs in EVs were differentially expressed between groups (G2 vs. G1). The bta-miR-103, bta-miR-502a, bta-miR-100, and bta-miR-1 were up-regulated (Log2 fold-change>1), whereas bta-miR-92a, bta-miR-140, bta-miR-2285a, and bta-miR-222 were down-regulated (Log2 fold-change<1). The more significant (P-value<0.01) up-regulated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were fatty acid biosynthesis and metabolism, lysine degradation, gap junction, and signaling pathways regulating pluripotency of stem cells. The EVs secreted by embryos to culture environment carry miRNAs that can reflect the molecular state of their parental cell. This lets us suggest culture media derived-EVs and their miRNA cargo as early biomarkers to select more competent bovine embryos. This research was supported by FONDECYT, Chile (1170310).

52 Blocking of embryonic development by nanoparticles derived from endometrial and oviductal cells isolated with an Amicon filter system

The success of development of invitro embryo production needs to mimic culture conditions in the maternal environment. Recently, it has been seen that extracellular vesicles (EVs) secreted by oviducal or endometrial cells may improve development and quality of embryos produced invitro. Extracellular vesicles are a mechanism of cellular communication; they carry molecules that are delivered into the target cells changing gene expression and function. Due to the size range and characteristics of EVs, they require specific methods for purification and characterisation. However, the possible contamination with other nanoparticles and their effect on embryo development have not been considered. Based on that, the goal of this work was to evaluate the effect on invitro bovine embryo development, of the addition to culture medium EVs secreted by oviducal and endometrial cells and isolated by centrifugation and concentrates with Amicon filters. For this purpose, cells were isolated from bovine oviduct and endometrium collected in local abattoir and primary cultures of epithelial and stromal cells were derived. The primary cultures from both sources were exposed or not to progesterone (P4; 15ngmL−1) for 4 days and then cultured for 24h in EV depleted media. The supernatant was harvested and EVs were isolated by serial centrifugations and subsequently concentrated by a 100 kDa Amicon filter system. The isolated EVs were characterised by transmission electron microscopy, nanoparticle tracking analysis, and flow cytometry. Oocytes were obtained from ovaries collected in the abattoir. The cumulus-oocyte complexes were matured invitro for 22h and subsequently fertilised for 18h. Presumptive zygotes were invitro cultured in synthetic oviducal fluid with EVs (1000ngmL−1 of total proteins) or not according to experimental group (1: EVs− (control); 2: EVs−OP4+; 3: EVs−OP4−; 4: EVs−EP4+ and 4: EVs−EP4−). Embryos were cultured for 7 days in 5% CO2, 5% O2, and 90% N2 (25 embryos/well in 4-well plates). At Day 7, embryo development was evaluated considering the blastocyst yield. Transmission electron microscopy showed typical structures and morphology of EVs and they were positive for CD9, CD63, and CD81 markers, and negative for CD40. According to nanoparticle tracking analysis, the mean size of EVs was 160±62nm and concentration of 3.29×1011 particlesmL−1 for oviducal and endometrial cells, respectively. A significant reduction of blastocyst rate was observed when embryos were cultured with cell-derived EVs; control: 152/44 (28.9%) vs. treatments with EVs; OP4+: 74/3 (4.1%), OP4−:76/2 (2.6%), EP4+: 74/6 (8.1%), and EP4−: 73/2 (2.7%) (P ≤ 0.01). Our results indicate that the use of nanoparticles, including EVs, isolated from cells of oviduct or endometrium, has a blocking effect on embryonic development and compromises the performance of blastocysts on Day 7 when used at concentrations of 1000ngmL−1 total protein, independent of the use or not of P4 and the source. These data provide insights regarding the use and protocols of acquiring exosomes for embryo supplementation. This research was supported by FONDECYT, Chile-1170310.

61 Extracellular vesicles from serum in culture media are internalized by bovine embryos produced in vitro

Extracellular vesicles (EV) are currently considered a mechanism of cell communication. These are secreted from different cell types, including embryos, to serve as mediators of short and long distance signals. EV can be identified in vivo in different biological fluids, as well as in vitro embryo culture medium. Usually, media used for embryo in vitro culture are supplemented with serum or other protein sources that favour cell proliferation and development. Serum and protein sources contain EV, including microvesicles and exosomes that in principle can be internalized by embryonic cells. The aim of this study was to evaluate if serum-derived EV are internalized by the embryo at different stages of the early development, and if EV from the serum are required for in vitro bovine embryo development. For that, it was first evaluated if EV depleted culture media affect embryo development up to the blastocyst stage; oocytes were in vitro matured for 22 to 23h and in vitro fertilized for 18h. Posteriorly, presumptive zygotes were in vitro cultured in groups (25 embryos/well in 4-well plates) in SOF or SOF depleted of EV for 8 days. To evaluate EV internalization, culture media was supplemented with labelled EV and confocal imaging was performed. The EV were obtained by ultrafiltration (centrifugal filter devices 100 kDa, Amicon; Millipore, Billerica, MA, USA) for 15min at 3000 rpm. Then, EV were stained with PKH67 dye and washed 3 times with PBS by ultrafiltration to remove excess dye. The EV labelled with PKH67 were resuspended in SOFaa depleted of EV (3×109 particles per 500µL) and supplemented for 24h at the 1-cell stage (Day 1 post IVF), 16 cells (Day 4 post IVF), and early blastocyst (Day 6 post IVF) in 5% CO2, 5% O2, and 90% N2. PBS with PKH67 dye was used as a control treatment. Hoechst 33343 was used to label the nuclei before washing with PBS and fixation with 0.4% paraformaldehyde. Images were acquired on a Zeiss (Zeiss, Jena, Germany) LSM 780 confocal microscope. There were no statistical differences on blastocyst rate at Day 8 between embryos cultured in SOF depleted of EV (19.5%) and control group (SOF; 22.7%; P>0.05). We observed punctuated green fluorescence near the embryo nuclei in the 3 stages studied in embryos supplemented with EV but not in the control treatment, which indicates that EV from serum are uptaken by embryonic cells in early development. Therefore, we demonstrated uptake of EV from fetal calf serum added to culture media, although its absence does not affect embryo development. Research was supported by FONDECYT, Chile (1170310).