Embryo response to different progesterone concentrations during superovulation of Holstein heifers: a transcriptomic...

This study aimed to evaluate the impact of high and low progesterone (P4) concentrations during superovulation on the transcriptome profile of early bovine embryos. A total of 63 post-pubertal Holstein heifers were randomly assigned to two experimental groups: High P4 (n = 32) and Low P4 (n = 31). Heifers underwent a pre-synchronization protocol followed by a protocol of superovulation that included the allocated P4 treatment. Embryos were collected 7d post-artificial insemination (AI) and assessed for developmental stage and quality grade. Embryos classified as good quality (High P4: n = 27; Low P4: n = 27 embryos) were randomly allocated in three biological replicates per treatment, with replicates balanced for stage of embryonic development. Total RNA was extracted from each replicate, and libraries were prepared and sequenced using the NovaSeq 6000 platform. Differential gene expression between treatment groups was determined through pairwise comparisons, with adjusted P-values calculated using the Benjamini-Hochberg correction. Ingenuity pathway analysis was used to identify upstream regulators, molecules, and networks influenced by the P4 treatment. Transcriptome analysis suggested that exposure to high or low concentrations of P4 during superovulation affects gene expression of 7d old embryos. These modifications were associated with downregulation of beta-estradiol and the WNT signaling pathway, as well as upregulation of trophoblast-related genes in High P4 embryos. Additionally, downregulation of genes related to neurological processes and differentiation was observed in High P4 embryos compared to Low P4. In conclusion, these transcriptional differences may be associated with distinct developmental competence of embryos following transfer.