In Vitro Mimicking of Estrous Cycle Stages: Dissecting the Impact of Estradiol and Progesterone on Oviduct Epithelium

: We have previously mimicked the morphological and functional changes occurring in the oviduct epithelium during the estrous cycle in vitro by using an air-liquid interface (ALI) culture system and basolateral application of 17β-estradiol (E2) and progesterone (P4). In the current study we aimed to explore the transcriptomic changes elicited by E2 and P4 together during estrous cycle simulation and to dissect the individual effects of E2 and P4 on oviduct epithelium physiology. Primary porcine oviduct epithelial cells (POECs) (N = 6 animals) were cultured at the ALI. After differentiation for 11 days, we sequentially simulated diestrus (10 days) and estrus (2.5 days) by adding serum levels of E2 and P4 to the basolateral compartment either in combination (mix trial) or separately (P4 trial and E2 trial, respectively). Cell response was evaluated by microarray analysis (mix and P4 trials), quantitative RT-PCR, and histomorphometry (all trials). When we compared simulated diestrus with estrus stage in the mix trial, there were 169 (142 upregulated and 27 downregulated) differentially expressed genes (DEGs; fold change ≥1.5). In the P4 trial, 108 DEGs (83 upregulated and 25 downregulated) were detected. Gene enrichment analysis revealed that immune-related pathways were exclusively affected in the mix trial. In both mix and P4 trials, POECs exhibited in vivo-like morphological changes regarding epithelium height and portion of ciliated cells. However, E2 alone did not trigger morphological changes. We deduce that P4 mainly drives structural variations, and E2 is imperative for regulating immune function of the oviduct epithelium during estrous cycle.