The proteomic analysis of bovine embryos developed in vivo or in vitro reveals the contribution of the maternal environment to early embryo

Abstract

Background Despite many improvements with in vitro culture systems, the quality and developmental ability of mammalian embryos produced in vitro are still lower than their in vivo counterparts. Though previous studies have evidenced differences in gene expression between in vivo- and in vitro-derived bovine embryos, there is no comparison at the protein expression level. Results A total of 38 pools of grade-1 quality bovine embryos at the 4–6 cell, 8–12 cell, morula, compact morula, and blastocyst stages developed either in vivo or in vitro were analyzed by nano-liquid chromatography coupled with label-free quantitative mass spectrometry, allowing for the identification of 3,028 proteins. Multivariate analysis of quantified proteins showed a clear separation of embryo pools according to their in vivo or in vitro origin at all stages. Three clusters of differentially abundant proteins (DAPs) were evidenced according to embryo origin, including 463 proteins more abundant in vivo than in vitro across development and 314 and 222 proteins more abundant in vitro than in vivo before and after the morula stage, respectively. The functional analysis of proteins found more abundant in vivo showed an enrichment in carbohydrate metabolism and cytoplasmic cellular components. Proteins found more abundant in vitro before the morula stage were mostly localized in mitochondrial matrix and involved in ATP-dependent activity, while those overabundant after the morula stage were mostly localized in the ribonucleoprotein complex and involved in protein synthesis. Oviductin and other oviductal proteins, previously shown to interact with early embryos, were among the most overabundant proteins after in vivo development. Conclusions The maternal environment led to higher degradation of mitochondrial proteins at early developmental stages, lower abundance of proteins involved in protein synthesis at the time of embryonic genome activation, and a global upregulation of carbohydrate metabolic pathways compared to in vitro production. Furthermore, embryos developed in vivo internalized large amounts of oviductin and other proteins probably originated in the oviduct as soon as the 4–6 cell stage. These data provide new insight into the molecular contribution of the mother to the developmental ability of early embryos and will help design better in vitro culture systems.

Cathepsin-L Secreted by High-Quality Bovine Embryos Exerts an Embryotrophic Effect In Vitro

“…Another study reported the presence of procathepsin-L in in-vitro- and in-vivo-derived bovine embryos, starting from the 8-cell and 4-cell stages, respectively. In both cases, expression of procathepsin-L peaked at the blastocyst stage and no significant differences were obtained between in vitro and in vivo embryos [ 66 ]. Likewise, studies in human and marmoset embryos reported the expression of cathepsin-L starting from the zygote, up to the blastocyst stage, with highest expression at the blastocyst stage [ 67 , 68 ].…”

Associations of the Single Bovine Embryo Growth Media Metabolome with Successful Pregnancy

“…The dominant hexose in growth media is glucose, and, as expected, both ET-P BL and ET-NP BL blastocysts consumed a fraction of it in our experiment. Glucose serves as a substrate for ATP and NADPH production once the biosynthesis gears up after the initial embryo cleavages [21]. In some studies, the level of glucose consumption has been linked to the quality and success of pregnancy [22].…”

Pre-Implantation Bovine Embryo Evaluation—From Optics to Omics and Beyond

“…Proteomic analyses of pre-implantation embryos have been carried out to study early lineage specification [ 204 ], EGA [ 203 ], stage-specific proteome dynamics during pre-implantation development [ 203 , 205 ], differences between IVP and IVD embryos [ 206 ], proteomes of the blastocoel fluid [ 207 ], primitive yolk sac fluid [ 208 ], and trophectoderm [ 209 ], and to identify embryotrophic factors in the secretome that can serve as biomarkers of high-quality embryos [ 210 ].…”