Tissue Regression-Related Alterations in the Expression of Adherens and Tight Junction Proteins in the Hen Oviduct

Intercellular junctions are involved in the regulation of epithelial function and remodeling in the female reproductive system; however, their importance in the avian oviduct is poorly known. The aim of this study was: first, to provide information on the expression and localization of key tight (occludin, claudin 1, 4, 5, junctional adhesion molecule [JAM] 2, 3) and adherens (E-cadherin, β-catenin) junction proteins in the hen oviduct, and second, to compare expression and localization of these molecules between laying and subjected to fasting-induced pause in laying hens. Tissue samples from all oviductal segments, i.e., infundibulum, magnum, isthmus, shell gland, and vagina were collected on the sixth day of the experiment from the control hens and hens that had been fasted for five consecutive days. Specific oviductal part-dependent expression patterns of examined genes (by quantitative real-time polymerase chain reaction [qRT-PCR]) and/or proteins (by Western blotting) were found, with the highest mRNA transcript and protein abundances in the infundibulum, shell gland, and vagina, and the lowest in the magnum. Fasting-induced partial regression of the oviduct was accompanied by alterations in mRNA transcript and protein abundances of examined molecules. Reduced staining intensity of immunoreaction (analyzed by immunofluorescence) for occludin, E-cadherin, and β-catenin proteins was observed in the oviduct of non-laying hens. Our results indicate the potential involvement of these proteins in controlling intercellular communication, cell signaling, paracellular permeability, and mucosal barrier functionality, which impact the functioning of the hen oviduct. Furthermore, our observations provide novel insights into the molecular composition of tight and adherens junctions and its contribution to the remodeling of the oviduct during its regression induced by fasting.