Integrin Beta 8 (ITGB8) Regulates Embryo Implantation Potentially via Controlling the Activity of TGF-B1 in Mice

Integrins (ITGs) are mediators of cell-cell and cell-matrix interactions, which are also associated with embryo implantation processes by controlling the interaction of blastocyst with endometrium. During early pregnancy, ITGbeta8 (ITGB8) has been shown to interact with latent transforming growth factor (TGF) beta 1 (TGFB1) at the fetomaternal interface. However, the precise role of ITGB8 in the uterus and its association with embryo implantation has not been elucidated. Therefore, we attempted to ascertain the role of ITGB8 during the window of embryo implantation process by inhibiting its function or protein expression. Uterine plasma membrane-anchored ITGB8 was augmented at peri-implantation and postimplantation stages. A similar pattern of mRNA expression was also found during the embryo implantation period. An immunolocalization study revealed the presence of ITGB8 on luminal epithelial cells along with mild expression on the stromal cells throughout the implantation period studied; however, an intense fluorescence was noted only during the peri- and postimplantation stages. Bioneutralization and mRNA silencing of the uterine Itgb8 at preimplantation stage reduced the rate/frequency of embryo implantation and subsequent pregnancy, suggesting its indispensable role during the embryo implantation period. ITGB8 can also regulate the liberation of active TGFB1 from its latent complex, which, in turn, acts on SMAD2/3 phosphorylation (activation) in the uterus during embryo implantation. This indicates involvement of ITGB8 in the embryo implantation process through regulation of activation of TGFB1.