The role of Wnt signaling members in the uterus and embryo during pre-implantation and implantation.

Wnt family members are best known for their roles in cell fate determination, differentiation, proliferation and apoptosis during embryonic development. Wnt signaling becomes effective during these cellular processes through the proper interaction between its ligands, receptors, effectors and inhibitors. Here we review Wnt signaling in terms of embryonic development to the blastocyst stage implantation with emphasis on endometrial changes that are critical for receptivity in the uterus. The relationship between Wnt signaling and implantation clearly reveals that, Wnt family members are critical for both early embryonic development and changing of the endometrium before implantation. Specific Wnt signaling pathway members are demonstrated to be critical for endometrial events such as decidualization and endometrial gland formation in addition to cyclic changes in the endometrium controlled by reproductive hormones. In conclusion, specific roles of Wnt members and associated factors for both uterine function and embryonic development should be further investigated with respect to the efficiency of human ARTs.