Uterine EGF Ligand-Receptor Signalling and Its Role in Embryo-Uterine Interactions during Implantation in the Mouse

The implantation process is a complex interaction between embryonic and uterine cells. Major critical events of the implantation process are: (i) synchronized development of the preimplantation embryo to the blastocyst stage and establishment of the receptive uterus; (ii) increased capillary permeability in the receptive uterus at the site of blastocyst apposition; (iii) localized decidualization of the uterine stroma immediately following blastocyst attachment; and (iv) controlled invasion of the stroma by the embryonic trophoblast (1). These events are primarily dependent upon temporal and cell type-specific interactions between progesterone (P4) and estrogen (E). However, the molecular and cellular mechanisms involved in these P4/E regulated processes are not clearly understood. One emerging concept is that P4/E effects in the uterus and/or the embryo are transduced by growth factors which function in an autocrine/paracrine manner. These growth factors are likely to be central elements in the regulation of the implantation process. This manuscript will focus on the role of growth factors, especially of epidermal growth factor (EGF), on embryo-uterine interactions during the peri-implantation period.