Network of cytokines, integrins and hormones in human trophoblast cells.

Trophoblast cells of the developing embryo are unique not only for transporting oxygen and nutrients from the mother to the fetus but also for their array of other functions throughout the pregnancy beginning from the attachment of the blastocyst to the endometrium during the process of implantation, its well regulated invasion in the uterine tissue, proliferation, differentiation and immuno-endocrine functions which subsequently maintain the pregnancy. Using human trophoblast cells in culture, we have tried to understand the molecular mechanisms which regulate such a variety of functions for trophoblast cells. Our RT-PCR studies show that trophoblast cells express the laminin and collagen receptors: integrins alpha1 and alpha2, which are both stimulated by IL-1 and IL-6. These two cytokines, also synthesised by the trophoblast cells themselves, act in an autocrine/paracrine manner to induce their own expression. In addition, IL-1 expression seems to be modulated by a large variety of cytokines and growth factors usually present in the uterine milieu whereas IL-6 expression appears to be significantly stimulated by growth factors like EGF and bFGF only. Hormones like estrogen, progesterone and hCG exhibit a general negative modulation in the expression of IL-1 and IL-6. Since, both IL-1 and IL-6 are known to be involved in the proliferation, invasion and differentiation of trophoblast cells, they might be the key factors involved in trophoblast functions.