Effect of porcine oviductal fluid-derived extracellular vesicle supplementation on in vitro embryonic developmental competence and the production efficiency of cloned pigs

Abstract

Extracellular vesicles (EVs) derived from oviductal epithelial cells help with fertilization and embryo development. Although the effects of EVs on the developmental competence of somatic cell nuclear transfer (SCNT) embryos are known, their impact on the production efficiency of cloned pigs in surrogate mothers is unclear. We evaluated the effects of porcine oviductal fluid-derived EVs (oEVs) on the in vitro development of SCNT embryos and production efficiency in cloned pigs. Embryos were treated with isolated and characterized oEVs for 48 h, corresponding to the residence time of fertilized embryos in the oviduct. In both parthenogenetic activation (PA) and SCNT embryos, oEV-treated groups exhibited higher rate of blastocyst formation than the controls. Gene expression analysis revealed increased expression of genes essential for early embryonic development in four-cell stage SCNT embryos, including those involved in pluripotency (POU5F1; POU class 5 homeobox 1), genome stability (Zinc finger and SCAN domain containing 4), and DNA damage response (Checkpoint kinase 1). Additionally, gene expression analysis of blastocysts from SCNT embryos showed increased expression of pluripotency (POU5F1) and Wnt signal transduction (Axis inhibition protein 2). Transfer of day-2 in vitro cultured SCNT embryos into surrogate mothers revealed no significant difference in production efficiencies between the control and experimental groups. Thus, enhanced early embryonic developmental competence observed in vitro following oEV treatment of PA or SCNT embryos did not translate into improved production efficiency of cloned pigs following embryo transfer to surrogate mothers. Hence, the impact of oEV treatment on live birth outcomes requires further investigation.