Reproduction Abstracts

Introduction: Embryo implantation is a complex and highly regulated process. Toll-Like receptors (TLRs) play a strategic role in recognition of pathogens in female reproductive tract. Activation of TLRs in endometrial cells at the time of embryo implantation appears to have negative effect on implantation. Tribbles-2 (Trib2) protein is members of tribbles family of psuedokinase proteins, modulating TLR5 signal transduction pathway.Tribbles-2 knockout female mice are infertile. Accordingly, we hypothesized that Trib2 regulate embryo implantation via controllingTLR5 signalling pathway.

Methods: To investigate Trib2 protein involvement in embryo implantation, wild-type mouse embryos were transferred into the oviducts of Trib2 null, Trib2 heterozygotes and wild-types. Furthermore, the desired combination of the functional TLR5 signalling pathway and the functional Trib2 protein in different human endometrial cell-lines (RL95-2, Ishikawa and Ishikawa 3H12) and an epithelial cell-line (HEK293T) was compared. Finally, to test Trib2 importance for embryo implantation in human, we used an in vitro binding assay based on a 2D co-culture of endometrial and trophoblast (JAr) cells.

Results and Discussion: No embryo successfully implanted in the uterine horns of Trib2 null females indicating the involvement of Trib2 protein in the implantation process. None of the endometrial cells tested, showed the combination of a functional TLR5 signalling pathway and a functional Trib2 protein. In contrast, HEK293T cells had both these features. Knock down of trib2 gene expression using siTrib2 led to a significant further reduction in adhesion of Jar spheroids to the HEK293T monolayer in the presence of TLR5 agonist, Flagellin (P value < 0.0001). Our results demonstrated that Trib2 is essential for successful embryo implantation in mice. Though, HEK293T cells are from non-reproductive origin, the endogenous expression of both TLR5 and Trib2 proteins in this cell-line, made it the optimum model for inspecting the Trib2 functions in humans.