Understanding embryo development in farmed mammals: an asset for selecting tomorrow's animals

To meet the challenges of agro-ecological and climatic transition, we need to be able to select animals on a wide range of often highly heterogeneous criteria, such as thermoregulation, feed efficiency, resistance to parasites and pathogens, and reproductive problems. Phenotypic measurements must therefore be highly varied. However, some, such as measurements of response to viral infections, are difficult to perform on farm animals, and raise ethical, logistical and economic problems. The use of pluripotent embryonic stem (ES) cells is a promising way to overcome these difficulties. In vitro, ES cells can be used to obtain a wide variety of cell lineages representative of the variety of animal tissues, on which numerous high-throughput measurements can be performed in the laboratory. However, ES cell culture in farm animals remains difficult to implement. In order to optimize the derivation of ES cells from pig embryo cells, INRAE researchers, in collaboration with a German research team, have characterized the ES cells of the embryo and the molecules required for their survival and proliferation.

To achieve this, the researchers used a cutting-edge technology that enables them to study all the cellular information derived from genes (gene expression) on the scale of single cells. They characterized this information for 35,000 embryonic cells, derived from pig embryos aged between 5 and 11 days after fertilization (before implantation). Using statistical and artificial intelligence approaches, they were able to identify new subpopulations of embryonic cells, important for the secretion of molecules required for implantation, which then contribute to the development of the embryonic placenta. They also observed, in an original way, the existence of two types of embryonic ES cells: one very early and very labile, which is also found in humans before implantation, and another, later and more stable in time, which persists several days before implantation. The dynamics of these two cell populations have been associated with significant changes in the secretory activity of the maternal uterus. Thanks to the analysis of these 35,000 cells, the researchers were able to identify new biological molecules crucial to the biology of embryonic pluripotent cells.

These original results 1) provide a better understanding of the biology of the early mammalian embryo, mirroring current knowledge of human embryonic cells, and 2) optimize the conditions for derivation and culture of porcine embryonic pluripotent cells. These advances will make it possible to obtain porcine embryonic stem cell lines, which, from a small number of embryos, will enable better in vitro phenotyping of animal populations and make the link with genotypes, to better select tomorrow's animals and thus meet the major challenges of agro-ecological and climatic transitions.

To characterize gene expression in each embryo cell, the researchers used microfluidic droplet technology. Each cell is isolated in a droplet with reagents that enable the expression of its genes to be measured without interfering with other cells. Each cell is then analyzed to find those that are similar and group them into cell populations. It is then possible to compare cell populations and identify molecules produced by their genes that are important for their biology.

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• Hervé Acloque

Reference :

Adrien Dufour, Cyril Kurylo, Jan B Stöckl, Denis Laloë, Yoann Bailly, et al.. Cell specification and functional interactions in the pig blastocyst inferred from single-cell transcriptomics and uterine fluids proteomics. Genomics, 2024, 116 (2), pp.110780. ⟨10.1016/j.ygeno.2023.110780⟩