Bovine endometrial organoids: A new tool to study conceptus-maternal interactions in mammals

We developed a hormonally responsive organoid model of the bovine endometrium. Bovine glandular epithelial cells isolated from reproductive tracts were cultured in an extracellular matrix hydrogel (Cultrex 2) at 38.5˚C, 5% CO₂ (n=3). RNA was extracted and qPCR confirmed the presence of gland markers: leukemia inhibitory factor, mucin-1, insulin-like growth factor binding protein-1, kruppel-like factor-5 and forkhead box protein-A2. Organoids were imaged at specific time-points to monitor growth. Morphologically, organoids were spherical and fast-growing at passages 0 and 1, but this declined following passage 2. Passage 0 (n=3) organoids were treated with 1000 ng/ml recombinant ovine Interferon Tau (IFNT) or 10 μg/ml progesterone (P4) for 24 hours and analysed by RNASeq to assess hormone responsiveness. 373 transcripts were upregulated (padj<0.05 or log₂fold change >2) in response to P4 treatment, with downstream analysis showing significant overrepresentation (FDR<0.05) of genes associated with positive regulation of protein localisation to plasma membrane and cell periphery. Of the 240 genes significantly downregulated by P4 these were significantly overrepresented (FDR<0.05) in biological processes of cilium and cytoskeleton organisation. IFNT treatment resulted in significant upregulation of 414 genes and downregulation of 119 genes. The largest cluster associated with differentially expressed genes in response to IFNT is defence to virus and interferon signalling. Thirty genes were altered by both P4 treatment and IFNT treatment. Organoids were also shown to express conserved microRNAs, and it was possible to culture them in a microfluidics device - making them a useful model for a multitude of potential investigations.