Embryo-maternal communication mediated by extracellular vesicles in the early stages of embryonic development is modified by in vitro conditions

Extracellular vesicles (EVs) have become important in embryo-maternal communication during early development. The aim of this study was to evaluate the effect of an in vitro system on early bidirectional embryo-maternal communication mediated by EVs. For this purpose, two experiments were performed: one to evaluate the effect of embryonic EVs on maternal cells and the second to determine the effect of maternal EVs on early embryonic development. For the first in vitro (IVP) and in vivo (IVV) experiments, bovine blastocysts were selected and individually cultured for 48 h to collect embryonic EVs secreted during days 7-9 of embryonic development. Embryonic EVs were added to the medium of in vitro-cultured bovine endometrial cells to evaluate their effect on the expression pattern of genes associated with endometrial function and response to interferon tau (IFNT). Non-classical interferon-stimulated genes (ISGs) were only induced by in vitro-derived embryos. In the second experiment, EVs released by endometrial cells cultured in vitro (EVC) and collected from uterine fluid (EV-UF) of cows in the early luteal phase were added to the culture medium of bovine embryos produced in vitro during days 5-9 of development. The effect of maternal in vitro or in vivo-derived EVs differs in the quality of bovine embryos produced in vitro during the pre-implantation period. The expression of IFNT in bovine embryos is increased by the effect of EV-UF treatment. Additionally, EV-UF treatment induces a sustained increase in diameter during embryonic development and a tendency towards a greater number of expanded and hatched blastocysts. However, some genes related to embryo quality are induced by EVC treatment.

In vitro preconditioning of equine adipose mesenchymal stem cells with prostaglandin E2, substance P and their combination changes the cellular protein secretomics and improves their immunomodulatory competence without compromising stemness

Mesenchymal stem cells (MSC) are modern tools in regenerative therapies of humans and animals owed to their immunomodulatory properties, which are activated in a pro-inflammatory environment. Different preconditioning strategies had been devised to enhance the immunomodulatory properties of MSC. In this research, we evaluated the immunological attributes of equine adipose MSC (eAMSC) before and after preconditioning in vitro with prostaglandin E₂ (PGE₂), substance P (SP), their combination and IFNγ. PGE₂/SP was the best combination to keep or enhance the mesodermal lineage differentiation of eAMSC. Alongside with this, preconditioning of eMSC with PGE₂ and SP did not affect expression of stemness MSC surface phenotype: CD90⁺, CD44⁺, MHC class I⁺, MHC class II^- and CD45^-, assessed by cytometry. Both naïve and preconditioned eAMSC expressed genes related with immune properties, such as MHC-I, PTGES, IL6, IL1A, TNFα and IL8 assessed by qPCR. Only TNFα was under expressed in treated cells, while the other markers were either overexpressed or not changed. In no cases MHC-II expression was detected. The antiproliferative effect of preconditioned eAMSC exposed to activated peripheral blood mononuclear cells (PBMC) showed that SP treatment significantly inhibited proliferation of LPS stimulated PBMC. When eAMSC were stimulated with Poly I:C, all the treatments significantly inhibited proliferation of stimulated PBMC (p < 0.05). Direct contact (coculture) between the preconditioned eAMSC and PBMC, induced a shift of significantly more (CD4/CD25/FOXP3)⁺ T-regulatory PBMC than naïve eAMSC. In the experiments of this research, we investigated the secreted proteomic profile of naïve and preconditioned eAMSC, 42 up-regulated and 40 down-regulated proteins were found in the proteomic assay. Our proteomic data revealed profound changes in the secretory pattern of MSC exposed to different treatments, compared to naïve eAMSC as well as among treatments. In overall, compared to naïve cells, the protein profile of preconditioned cells resembled the mesenchymal-epithelial transition (MET). Here we showed that the combined use of PGE₂ and SP provoked in overall the highest expression of anti-inflammatory markers as well as lead to an increased acquisition of a T-regulatory phenotype in preconditioned eAMSC without affecting their "stemness".

128 Next-generation RNA sequencing of horse adipose and endometrial mesenchymal stem cells from the same donors unveils striking differences in their transcriptomic pattern

Earlier we successfully isolated and characterised endometrial (eMSC) and adipose (aMSC) mesenchymal stem cells from the same donors. Mesenchymal stem cells share biological traits but display different surface marker phenotype and migration ability. Here we extended our research to their mRNA signature using next-generation sequencing. The RNA from cells (3 biological replicates from each cell type and 3 technical replicates) at 90% confluence was extracted using a total RNA extraction kit and sent for mRNA-Seq (Norgen, Ontario, Canada; Illumina Sequencing Platform NextSEqn 500). Raw 76-bp single-end reads were aligned against the EquCab3 genome using RNA-STAR aligner. Counts were filtrated at a minimum of 5. Pairwise comparisons between the cell types were the input for gene ontology enrichment analysis. Only genes differentially expressed (DE) with 5 folds change (FC; P&lt;0.05) were analysed. For DE analysis, eMSC were set as control and compared with aMSC. Unsupervised hierarchical clustering of the global gene expression signatures was done to compare the samples from each line using principal component analysis (PCA) and EdgeR: v3.20.9. Gene expression was normalized using FPKM. The heat map was built using R studio with G-plot package. A total of 14,896 transcripts with at least 5 reads were found; of these, 1598 were DE: 627 up-regulated (FC range: 2 to 236×) and 971 down-regulated (FC range: 2 to 464×) in eMSC. There was a marked dispersion in the FC of up- and down-regulated genes (&gt;50×: 8 and 13; &gt;20×, &lt;50×: 9 and 17; &gt;10×, &lt;20×: 29 and 63; &gt;5×, &lt;10×: 91 and 130 and &gt;2×, &lt;5×: 490 and 748, respectively). Only genes DE with FC at least 5× were used for gene ontology and PCA analysis. Though 14,058 genes were common to both cell types, specific set of genes were found only in eMSC (n=162) or aMSC (n=676). Among the top 50 genes overexpressed in eMSC, several genes key for stem cell growth, immune response, migration and angiogenesis were found: TRIL, CXCL8, PDGF-D, SEMA5A, PTGS2, FGD, LAMA2, IL36G. In the top 50 down-regulated genes, some pivotal for osteoblast, adipogenic and neural differentiation were dramatically down-regulated (GPM6B, SCARA5 and NOTCH3 or NEFM, respectively), but no genes involved in immune rejection or stem cell proliferation were found. In gene ontology, the categories represented the most were cellular, developmental, metabolic, and immune system processes, as well as biological regulation, response to stimuli, organellar biogenesis, locomotion, localization and biological adhesion. Heat map and PCA analysis showed that one individual cell line from each type diverged markedly from the shared pattern. Individual variability of the donors may impinge upon the results; nevertheless, striking differences in the mRNA portfolio of eMSC and aMSC were detected. The importance and potential biological role of several of the genes and processes named above will be discussed in detail elsewhere. This work was supported by grant FONDECYT REGULAR 1150757 and the Government of Chile.

184 ISOLATION AND CHARACTERIZATION OF BOVINE ENDOMETRIAL STEM CELLS

Adult mesenchymal stem cells had been isolated from various tissues of different species, including endometrial tissue of humans, mice, and pigs, but not from cattle. The aim of our work was to identify such cells in the bovine endometrium and to establish a model system in which to test inducers of differentiation and recruiters of stem cell niches, for potential therapeutic use in this and other species, such as horses. We searched for endometrial stem cells in healthy cycling cows and in cattle with clinical (C) or subclinical (SC) endometritis. For this, the uterine tracts of slaughtered cows were collected at early (Days 2 to 5; ELF) and late luteal phases (Days 11 to 15; LLF) of the oestrus cycle of healthy cows. For endometritis-diseased cattle, uterine biopsies were taken in live animals. In all cases, markers of stemness, inflammation, uterine function, and housekeeping were studied both at mRNA and protein level, by RT-qPCR and Western blot/immunohistochemistry respectively. In addition, cell primary cultures were established in vitro from all the animals (n = 4 for ELF, n = 4 for LLF; n = 4 for C and n = 4 for SC). We found that the endometrium of the majority of studied animals expressed embryonic stem cell markers, OCT4 and SOX2, but not or little NANOG, as well as CD44, c-Kit, and STAT3, all markers of mesenchymal stem cells. The expression profile of these markers was not related to the stage of the oestrus cycle; however there was a statistically significant reduction in the expression of embryonic stem cell markers in ill animals, being the lowest in clinically ill and intermediate in subclinical endometritis, (P < 0.05 and Pearson correlation coefficient 0.92). For markers of multipotency (mesenchymal), the expression was lower in clinical endometritis (P < 0.05). In conclusion, the expression profile of stem cell markers is indicative of the presence of stem cells in the bovine endometrium. At the protein level, we verified our findings for OCT4, SOX2, and CD44 using Western blot and immunohistochemistry. In general, there was a concordance between mRNA and protein profiles. Inflammatory markers showed a pattern characteristic for each of the studied stages. In order to have an ultimate criterion of the presence of stem cells, we tested the differentiation potential of the isolated cell lines, upon induction towards chondrogenic, osteogenic, and adipogenic lineages. We found that all the cell lines tested (n = 8) displayed mesenchymal differentiation potential as demonstrated by specific staining and gene expression markers. At present, work is in progress to isolate pure stem cell populations from these primary cultures to further characterise these cells. Conclusion: we showed for the first time the presence and differentiation potential of endometrial stem cells in cattle. This can have an effect on the development of new therapeutic approaches to combat uterine diseases, such as endometritis or endometriosis (in horses). This work was supported by grant FONDECYT REGULAR 1110642, from the Government of Chile.