MicroRNA profiling reveals oviductal extracellular vesicles as active players in embryo signaling and molecular snitches of embryo quality

Increasing evidence points at an active role of oviductal extracellular vesicles (oEVs) in the early embryo-maternal dialogue. However, it remains unclear whether oEVs participate in the oviductal recognition system of embryo quality. Hence, we examined whether oEVs molecular cargo secreted by bovine oviduct epithelial cells (BOEC) differs depending on the presence of good (G) or poor (P) embryos. An in vitro model, based on the co-culture of primary BOEC with in vitro produced embryos (IVP) was used, as follows: BOEC with G embryos (BGE); BOEC with P embryos (BPE); G embryos alone (GE); P embryos alone (PE); BOEC alone (B) and medium control (M). After 24h co-culture, oEVs were isolated from conditioned media, characterized and their RNA cargo was analyzed. MicroRNA profiling of oEVs and embryos was performed by RNA-sequencing. In oEVs, 84 miRNAs were identified, with 8 differentially abundant (DA) miRNAs for BGE vs. B and 4 for BPE vs. B (P-value <0.01). In embryos, 187 miRNAs were identified, with 12 DA miRNAs for BGE vs. BPE, 3 for G vs. P, 8 for BGE vs. GE, and 11 for BPE vs. PE (P-value <0.01). These results indicate that oEVs are active players in the oviductal recognition of embryo quality and point to potential miRNAs with signaling and supporting roles during early embryo development. Besides, differences in embryonic miRNA profiles evidence the impact of the lack of early embryo-maternal interactions in IVP.