Tissue regression-related changes in connexin 43 and zonula occludens 1 gene and protein expression in the hen oviduct

A growing body of evidence has highlighted the involvement of intercellular junctions in the remodeling of various tissues in physiological and pathological conditions. In this study, the hypothesis was that the expression of connexin 43 (Cx43 protein/GJA1 gene) and zonula occludens 1 (ZO1), crucial molecules of gap junctions and tight junctions, respectively, changes in the regressing oviduct of non-laying hens. Accordingly, the mRNA transcript and protein abundance of Cx43 and ZO1 and their protein localization in the oviduct of hens subjected to a fasting-induced pause in egg laying were examined. All oviductal parts (the infundibulum, magnum, isthmus, shell gland, and vagina) were harvested on the sixth day of the experiment from the control (laying) hens and hens that had been fasted for five consecutive days (non-laying). qRT-PCR, western blotting, and immunofluorescence were applied to examine gene expression, protein abundance, and protein localization, respectively. Fasting caused a decrease in the oviduct weight, concomitantly with histological changes in the oviductal wall, including epithelial thinning, tubular gland degeneration, and disorganization of tissue architecture. Segment-specific expression patterns of Cx43 and ZO1 genes were observed, with the lowest mRNA transcript and protein abundance being noted in the magnum. In the fasted hens, GJA1 mRNA transcript abundance did not change in the oviductal parts compared to the control hens; however, an increase in ZO1 mRNA level was observed in the shell gland. Cx43 protein abundance was reduced in the infundibulum and shell gland, whereas ZO1 protein abundance was increased in the shell gland of the fasted birds. Reduced and irregular immunoreactivity of Cx43 and ZO1 proteins was observed in the oviduct of the non-laying hens. The results demonstrate that fasting-induced oviductal tissue regression was accompanied by alterations in the expression and localization of Cx43 and ZO1 proteins, indicating the potential role of these proteins in the control of cell-cell communication, paracellular permeability, and mucosal barrier formation in the hen oviduct.