Comparative Studies on the In Vitro: DISCUSSION(4)
The function of IGFBP-1 produced by the decidua is poorly understood. The IGFBPs either can enhance or inhibit insulin-like growth factor (IGF) action or could act independently of IGFs and bind to integrins through the IGFBP-1 RGD sequence. The involvement of IGFBP-1 in controlling trophoblast invasion has been suggested but remains unresolved. One possible mechanism supporting this concept involves the interaction of IGFBP-1 with in-tegrins. It has been shown that mouse primary trophoblast cells when cultured on extracellular matrix proteins appear to interact with fibronectin exclusively through the RGD recognition site. IGFBP-1 contains the RGD tripeptide sequence, which can bind to the a5p! integrin receptor. ventolin inhaler
Thus, it is possible that maternal IGFBP-1 may affect the interaction between placental trophoblast and extracellular matrix proteins in the endometrial stroma and modulate invasion into the maternal decidua. If IGFBP-1 is indeed involved in controlling the invasive process of the trophoblast, it would be logical to assume that high levels of this protein in the decidua would be required to regulate the highly invasive nature of the human trophoblast. The extravillous trophoblasts have been occasionally found as deep as the myometrial layer of the uterus. Invasion of the baboon trophoblast, as with most primates, is more superficial than that of the human and exhibits a limited area of decidualization that corresponds to areas of tropho-blast contact. Thus, the levels of IGFBP-1 required to regulate the invasion process in this species would be expected to be lower than the level in the human.