Concentration-Dependent Type 1 Interferon-Induced Regulation of MX1 and FABP3 in Bovine Endometrial Explants

SIMPLE SUMMARY: Low fertility rates in high-yielding cows have been reported for many years. Due to its impact on animal welfare, this topic is relevant to the dairy industry, veterinary medicine, and consumers. This study was designed to apply a highly defined model to simulate complex mechanisms that occur in the inner layer of the uterus (endometrium) during pregnancy recognition. Samples were taken from animals with healthy uteri at the slaughterhouse and challenged in vitro. The endometrial gene expression of selected target genes differed according to the differing concentrations of the challenging admixtures. The findings indicated that the bovine embryonic pregnancy signal might compete with similar infection-associated signals for binding capacity at the receptor level, which might be relevant to pregnancy outcomes. In conclusion, an endometrial explant model was successfully applied to answer questions related to fertility in dairy cattle. According to the 3R principle (replacement, reduction, refinement), further studies could lead to new diagnostic and therapeutic strategies for tackling subfertility in dairy cows without the need for animal experiments. ABSTRACT: The inadequate maternal recognition of embryonic interferon τ (IFNτ) might explain subfertility in cattle. This study aimed at modeling the inducibility of type 1 interferon receptor subunits 1/2 (IFNAR1/2), mimicking competition between IFNτ and infection-associated interferon α (IFNα), and simulating type 1 interferon pathways in vitro. Endometrial explants (n = 728 from n = 26 healthy uteri) were collected at the abattoir, challenged with IFNτ and/or IFNα in different concentrations, and incubated for 24 h. Gene expression analysis confirmed the inducibility of IFNAR1/2 within this model, it being most prominent in IFNAR2 with 10 ng/mL IFNα (p = 0.001). The upregulation of interferon-induced GTP-binding protein (MX1, classical pathway) was higher in explants treated with 300 ng/mL compared to 10 ng/mL IFNτ (p < 0.0001), whereas the non‑classical candidate fatty acid binding protein 3 (FABP3) exhibited significant downregulation comparing 300 ng/mL to 10 ng/mL IFNτ. The comparison of explants challenged with IFNτ + IFNα indicated the competition of IFNτ and IFNα downstream of the regulatory factors. In conclusion, using this well-defined explant model, interactions between infection-associated signals and IFNτ were indicated. This model can be applied to verify these findings and to mimic and explore the embryo–maternal contact zone in more detail.