[Role of growth factors in the regulation of embryo development and implantation].

Although it has been reported that growth factor and extracellular matrix (ECM) play an important role in the control of cell proliferation and differentiation in general, their involvement in the regulation of early embryogenesis and implantation is poorly understood. In order to clarify the mechanism underlying establishment and maintenance of pregnancy, the effect of EGF, TGF-alpha, TGF-beta, TN (tenascin) on the development of preimplantation embryo and endometrial function were investigated. 1. Growth factors in early embryogenesis. EGF did not exert any significant effect on the development of mouse 2-cell embryo in vitro. RT-PCR revealed the presence of EGFmRNA in blastocyst and 2-cell embryo, in which it may be derived from maternal genome. PA-1 cells, human teratocarcinoma-derived cell line, share biochemical characteristics with embryo developed at and beyond blastocyst stage. Anti-EGF antibody but not EGF exerted inhibitory effect on DNA synthesis in PA-1 cell, which produced and secreted immunoreactive and bioactive EGF and contained high-affinity EGF receptor. These results indicate that autocrine/paracrine mechanism of EGF action may be a key regulation of embryo development at and beyond blastocyst stage. 2. Growth factors and ECM in implantation. The luminal fluid in DES-stimulated mouse uterus contained high concentrations of EGF and TGF-alpha. In vivo administration of EGF, like estrogen, stimulated uterine epithelial proliferation as well as progesterone receptor levels. In vivo administration of anti-EGF antibody or anti-TGF-alpha antibody significantly reduced estrogen-induced labelling index in castrated mouse uterus. The concomitant administration of TGF-beta 1 and TGF-beta 2 with estrogen further stimulated DNA synthesis in the mouse uterus than estrogen alone. These results suggest that growth factors partly may be a mediator of estrogen actions on the uterine cell proliferation and the induction of progesterone receptor, which are important preparative steps for implantation. Northern blotting and in situ hybridization using cDNA probe for mouse prepro EGF revealed the presence of prepro EGFmRNA in the early pregnant mouse uterus, especially in stroma/decidua in Day 6 of pregnancy. EGF and TGF-alpha significantly stimulated trophoblast outgrowth of the mouse blastocyst in vitro in supplementation with 0.1% of fetal bovine serum. The specific binding of EGF was detected in the outgrown trophoblastic cells and inner cell mass of cultured blastocysts by autoradiography. From these findings, it may be possible that EGF produced in stromal/decidual cells exerts stimulatory effect on trophoblast outgrowth, playing an important role in the interaction between embryo and endometrium.(ABSTRACT TRUNCATED AT 400 WORDS)