Chemical Signals in Embryo-Maternal Dialogue: Role of Growth Factors

Abstract

In 1947, Corner described that the uterine chamber is actually a less favorable place for early embryos than, say, the anterior chamber of the eye, except when the hormones of the ovary act upon it and change it to a place of superior efficiency for its new functions (1). More recent is the realization that initiation and establishment of pregnancy result from an intimate interaction between the developing embryo and the differentiating uterus. However, although conceptually realized, the nature and timing of such a two-way dialogue between the blastocyst and the uterus are still challenging questions. The establishment of early pregnancy is a conglomeration of several synchronized and precisely controlled embryonic and maternal components: (i) the migration, spacing, and orientation of the embryo within the uterus, (ii) development of the embryo to the blastocyst stage and differentiation of the uterus to the receptive state, (iii) apposition and adhesion of the trophoblast with the uterine epithelium followed by attachment to the uterus, and (iv) increased capillary permeability and blood flow in the uterine vascular bed (2). These events are primarily dependent on temporal and cell type-specific interactions between progesterone and estrogen. However, the molecular and cellular mechanisms involved in these steroid hormone-regulated processes are not clearly understood.