In vitro mimicking of estrous cycle stages based on a comprehensive porcine oviduct epithelial cell culture model

In conclusion, the mammalian oviduct epithelium plays a pivotal role in aspects of gamete transport, oocyte maturation, and development of preimplantation embryos. However, valid in vitro models for the oviduct epithelium are still missing. During the estrous cycle, oviduct epithelium is subjected to dynamic changes which points towards regulation by E2 and P4. Among the cyclic events, there have been conflicting reports on sperm binding and cilia activity during the estrous cycle. Besides, to date no method is available to provide information on fluid movement patterns driven by cilia. Thus, in this study we aimed to: 1. Validate a culture model of porcine oviduct epithelial cells (POEC). Based on our previously established protocol to isolate and cultivate polarized POEC [44], we focused on developing the first standardized, comprehensive in vitro model of porcine oviduct epithelium. To offer a dossier of validation, data on culture duration, medium supplementation, and cryopreservation of primary cell material was collected from increased numbers of donor animals. Furthermore, to check the characteristic maintenance of in vivo tissue, the model was tested for morphological and functional endpoints including: degree of polarization, ultrastructure, electrophysiology, secretion of mucins, and expression of markers. 2. Mimic the estrous cycle in vitro. After validating the POEC model, we focused on mimicking the estrous cycle stages in POEC, and thus to reveal the regulatory mechanisms of E2 and P4 on cyclic events, such as: cell differentiation, ciliogenesis, and gene expression. Furthermore, the sperm-epithelium binding was investigated during mimicked estrous stages. 3. Monitor cilia beating by fluid movement in POEC. Our last objective was to develop an in vitro approach, which could be used to monitor the cilia activity, as well as to reflect movement patterns of oviduct fluid during the simulated estrous cycle.