Tumor Necrosis Factor α System in the Bovine Oviduct: A Possible Mechanism for Embryo Transport

Abstract

Active contractile pattern of the oviduct occurs during the periovulatory period for the movement of the gamete/embryo, which is strictly regulated by endocrine and paracrine/autocrine factors. In this review, an involvement of tumor necrosis factor α (TNFα) in the regulation of cow oviductal contraction is discussed. Oviductal epithelial cells express TNFα ligand and it's both receptor types; high expression during the follicular and postovulatory stages, while low expression during luteal stage and thus, TNFα system in the cow oviduct is most active during the periovularoty period. The immune cells present in large numbers in the oviduct during the periovulatory period of the estrus cycle, and these cells are also considered as another potential source for the TNFα in the oviduct. Using in vitro models, TNFα clearly stimulated local production and release of contraction related substances such as prostaglandins (PGs), endothelin-1 (ET-1) and angiotensin II (Ang II). Since these substances have been shown to activate directly the oviductal contraction in vitro, TNFα appears to stimulate the oviductal contraction during the periovulatory period and contribute to create an optimal local environment suitable for gamete/embryo transport. In addition, the ability of embryo to act as a source of TNFα in the oviduct cannot be excluded. To support this idea, the embryo at 2-4 cells stages indeed express TNFα, so that the minute quantities of TNFα secreted by the embryo may further acts locally to enhance the production of PG, ET-1 and Ang II in the oviduct, which may result in an active oviductal contraction in the microenvironment around the embryo. This may ensure the embryo to migrate into the uterus at the optimal time.