Oxygen levels affect oviduct epithelium functions in air-liquid interface culture.

Key reproductive events such as fertilization and early embryonic development occur in the lumen of the oviduct. Since investigating these processes in vivo is both technically challenging and ethically sensitive, cell culture models have been established to reproduce the oviductal microenvironment. Compartmentalized culture systems, particularly air-liquid interface cultures (ALI; cells access the culture medium only from the basolateral cell side), result in highly differentiated oviduct epithelial cell cultures. The oxygen (O) tension within the oviduct is 4-10% across species, and its reduced O content is presumed to be important for early reproductive processes. However, cell culture models of the oviduct are typically cultivated without O regulation and therefore at about 18% O. To investigate the impact of O levels on oviduct epithelium functions in vitro, we cultured porcine oviduct epithelial cells (POEC) at the ALI using both physiological (5%) and supraphysiological (18%) O levels and two different media regimes. Epithelium architecture, barrier function, secretion of oviduct fluid surrogate (OFS), and marker gene expression were comparatively assessed. Under all culture conditions, ALI-POEC formed polarized, ciliated monolayers with appropriate barrier function. Exposure to 18% O accelerated epithelial differentiation and significantly increased the apical OFS volume and total protein content. Expression of oviduct genes and the abundance of OVGP1 (oviduct-specific glycoprotein 1) in the OFS were influenced by both O tension and medium choice. In conclusion, oviduct epithelial cells can adapt to a supraphysiological O environment. This adaptation, however, may alter their capability to replicate in vivo tissue characteristics.