Transcriptional Profiling of Porcine Blastocysts Produced In Vitro in a Chemically Defined Culture Medium

Liquid storage of porcine in vitro-produced blastocysts; a practical approach for short storage

Commercial application of embryo transfer in pig breeding is dependent on the storage of embryos. The aim of this study was to assess the embryo quality of in vitro-produced blastocysts after 3 h liquid storage at 37°C in CO2-free medium by evaluating morphology, in vitro developmental capacity and apoptosis. Blastocysts at days 5 and 6 post-fertilization were randomly allocated to the storage group (HEPES-buffered NCSU-23 medium including bovine serum albumin in a portable embryo transport incubator at 37°C) or a control group (porcine blastocyst medium in a conventional culture incubator). Thereafter, blastocysts were evaluated for morphology and stained to assess apoptosis straight after the 3 h storage period or after a further 24 h conventional incubation. There was no significant difference between the storage and control group after 3 h storage and the further 24 h conventional incubation for any of the parameters, nor for apoptosis straight after the 3 h storage. Embryos that reached the blastocyst stage at day 5 showed less apoptosis (6.6% vs 10.9%, P = 0.01) and a trend for a higher rate of developmental capacity (70.6% vs 51.5%, P = 0.089) than embryos reaching the blastocyst stage on day 6. In conclusion, in vitro-produced porcine blastocysts can be stored for 3 h at physiological temperature in transportable incubators using a CO2-independent medium without compromising quality.

Oviductal Extracellular Vesicles Enhance Porcine In Vitro Embryo Development by Modulating the Embryonic Transcriptome

Oviductal extracellular vesicles (oEVs) have been identified as important components of the oviductal fluid (OF) and have been pointed to as key modulators of gamete/embryo-maternal interactions. Here, we determined the functional impact of oEVs on embryo development and the embryonic transcriptome in porcine. Experiment 1 examined the effect of oEVs and OF on embryo development. In vitro-produced embryos were cultured with oEVs or OF for 2 or 7 days using an in vitro sequential system or without supplementation (control). Experiment 2 analyzed transcriptomic alterations of EV-treated embryos versus control and the oEVs RNA cargo by RNA-sequencing. Two days of EV treatment enhanced embryo development over time when compared to other treatments. Different RNA expression profiles between embryos treated with EVs for two or seven days and untreated controls were obtained, with 54 and 59 differentially expressed (DE) genes and six and seven DE miRNAs, respectively. In oEV RNA cargo, 12,998 RNAs and 163 miRNAs were identified. Integrative analyses pointed to specific oEV components that might act as modulators of the embryonic transcriptome, such as S100A11, ANXA2 or miR-21-5p. Overall, the findings suggested that oEVs could be a potential strategy to improve porcine IVP outcomes, particularly by using two days of EV treatment.