Novel expression and localization of hypoxia inducible factor 1 alpha (HIF1α) and selected angiogenesis-related factors in the oviduct of laying and non-laying hens.

Egg formation and oviposition in hens depend on a network of blood vessels that supply the oviduct with all the essential molecules. This network develops during angiogenesis, a process involving many regulators, including hypoxia inducible factor 1 alpha (HIF1α), the vascular endothelial growth factor (VEGF) system, and the angiopoietin (ANGPT) system. Given the lack of information on HIF1α and angiogenesis in the avian oviduct, this study examined the expression of HIF1α, VEGFA and its receptors, ANGPT1 and ANGPT2 and their receptor mRNA transcript and protein abundances, as well as protein localization in the oviduct of laying and non-laying hens. A pause in laying was induced by fasting for five consecutive days. On day 6 of the experiment, tissues were harvested from control hens and hens that had been fasted. Quantitative RT-PCR and western blot analyses revealed changes in the expression of the examined factors between the distinct segments of the oviduct. In laying hens, the mRNA expression of genes related to angiogenesis was highest in the infundibulum, shell gland, and vagina and lowest in the magnum. In fasted hens, partial oviductal regression was accompanied by a decrease in mass, thinner epithelium, and degenerating tubular glands. Fasting also affected gene expression in oviductal parts, with the most pronounced upregulation occurring in the isthmus and vagina. The presence of both the unmodified and modified forms of HIF1α was detected, with higher abundances of the modified form observed in fasted hens. Immunoreactivity for HIF1α and VEGFA proteins was observed in all tissues of the oviductal wall, with strong immunopositive signals for HIF1α in the muscles and for VEGFA in the luminal epithelium and blood vessels. In the oviduct of fasted hens, immunoreactivity for HIF1α and VEGFA proteins was relatively stronger than in the oviduct of control hens. The results indicated that HIF1α and other factors associated with angiogenesis might play a role in regulating oviductal vascularization in hens, under both physiological conditions and fasting-induced regression. Furthermore, our findings provide novel insights into the involvement of HIF1α and angiogenesis-related factors in the function and remodeling of the avian oviduct.