Bovine Oviduct Epithelial Cells Dedifferentiate Partly in Culture, While Maintaining their Ability to Improve Early Embryo Development Rate and Quality

<jats:title>Contents</jats:title><jats:p>There are convincing arguments to suggest that the success of early reproductive events is reliant on a satisfactory dialogue between gametes–embryo and the oviduct epithelium. The aim of this study was to develop and characterize an <jats:italic>in vitro</jats:italic> model to study these interactions. Cattle zygotes produced <jats:italic>in vitro</jats:italic> were cultured in either <jats:styled-content style="fixed-case">SOF</jats:styled-content> or <jats:styled-content style="fixed-case">TCM</jats:styled-content>‐199 in the presence or absence of bovine oviduct cell monolayers (<jats:styled-content style="fixed-case">BOEC</jats:styled-content>), under 20% or 5% O<jats:sub>2</jats:sub>. The embryonic development rate and its quality (cell numbers, cryosurvival) were evaluated, as were the <jats:styled-content style="fixed-case">BOEC</jats:styled-content> contents in 11 candidate transcripts (real‐time <jats:styled-content style="fixed-case">PCR</jats:styled-content>) at different time points. A <jats:styled-content style="fixed-case">BOEC</jats:styled-content> co‐culture did indeed increase the rate of development in both media under 5% O<jats:sub>2</jats:sub> (41 vs 27% and 28 vs 10% of Day 8 blastocysts in <jats:styled-content style="fixed-case">SOF</jats:styled-content> and <jats:styled-content style="fixed-case">TCM</jats:styled-content>‐199, respectively; p < 0.05). The effect of <jats:styled-content style="fixed-case">BOEC</jats:styled-content> on the developmental rate was more pronounced under 20% O<jats:sub>2</jats:sub> (35 vs 6% and 27 vs 4% of Day 8 blastocysts in <jats:styled-content style="fixed-case">SOF</jats:styled-content> and <jats:styled-content style="fixed-case">TCM</jats:styled-content>‐199, respectively; p < 0.05). <jats:styled-content style="fixed-case">BOEC</jats:styled-content> significantly increased the embryonic cell count in <jats:styled-content style="fixed-case">TCM</jats:styled-content>‐199 (122.5 ± 11.1 vs 70.3 ± 9.6; p < 0.05) and embryonic cryosurvival in both media. The expression levels of <jats:styled-content style="fixed-case">SOD</jats:styled-content>,<jats:styled-content style="fixed-case"> FGF</jats:styled-content>2 and <jats:styled-content style="fixed-case">TGF</jats:styled-content>‐<jats:italic>β</jats:italic>1 in <jats:styled-content style="fixed-case">BOEC</jats:styled-content> remained steady during culture, although <jats:styled-content style="fixed-case">mRNA</jats:styled-content> levels of <jats:styled-content style="fixed-case">OGP</jats:styled-content>, C3, <jats:styled-content style="fixed-case">PGR</jats:styled-content> and <jats:styled-content style="fixed-case">ESR</jats:styled-content>2 were clearly reduced, suggesting a dedifferentiation of <jats:styled-content style="fixed-case">BOEC</jats:styled-content> during culture. However, <jats:styled-content style="fixed-case">SSP</jats:styled-content>1 and <jats:styled-content style="fixed-case">GPX</jats:styled-content>4 transcripts were slightly increased during culture, this rise becoming significant by the end of the culture period. In conclusion, our co‐culture system with bovine oviduct epithelial cells used for the development of bovine zygotes produced <jats:italic>in vitro</jats:italic> enhanced blastocyst formation and above all the quality of the resulting embryos, which was associated with specific transcriptomic changes.</jats:p>