NATURAL KILLER CELL EFFECTS UPON ANGIOGENESIS UNDER CONDITIONS OF CONTACT-DEPENDENT AND DISTANT CO-CULTURING WITH ENDOTHELIAL AND TROPHOBLAST CELLS

Abstract

Regulation of angiogenesis in the utero-placental bed determines adequate trophoblast invasion, placenta formation and development, as well as successful course of pregnancy. Natural killer (NK) cells, macrophages and trophoblast have the most significant effect on angiogenesis. To date, the functions of cells participating in placenta formation have been described in detail, both individually (in vitrо) and in tissues (in situ). However, no models have yet been created that reflect the interactions of NK cells, trophoblast and endothelium during angiogenesis. It remains unclear, how each cell population contributes to placental angiogenesis regulation, and to the cross-regulation of participating cell functions. Therefore, the aim of this research was to study contact and distant effects of NK cells upon formation of tube-like structures through co-culture of endothelial and trophoblast cells influenced by various cytokines (bFGF, VEGF, PlGF, TGF-β, IL-8, IFNγ and IL-1β). Introduction of NK cells to the co-culture of endothelial and trophoblast cells under conditions of both contact and distance-dependent culturing did not change the length of tube-like structures formed by endothelial cells. During contact-dependent culturing of NK cells with co-culture of endothelial and trophoblast cells in presence of IL-1β, the length of tubule-like structures remained unchanged, compared with the length of tube-like structures formed under the same culturing conditions, but without the cytokine added. During distant culturing of NK cells with co-culture of endothelial and trophoblast cells in the presence of IL-1β, the length of tube-like structures increased as compared with those formed under the same culturing conditions but without the cytokine. During contact-dependent (but not distant) culturing of NK cells with the co-culture of endothelial and trophoblast cells in the presence of VEGF, the length of tube-like structures was greater than those formed under the same culturing conditions but without the cytokine. When used in a three-component cell system, the pro-inflammatory cytokine IFNγhad no effect upon angiogenesis. During distant (but not contact-dependent) culturing of NK cells with co-culture of endothelial and trophoblast cells in the presence of TGF-β, the length of tube-like structures was less than the length of tube-like structures formed under the same culturing conditions but without the cytokine. Under conditions of distant culturing, TGF-βtriggered a signal in NK cells that inhibited angiogenesis. Decreased length of tube-like structures under conditions of a three-component cell co-culture in the presence of the following pro-angiogenic factors was revealed: IL-8, PlGF (during contact-dependent culturing only) and bFGF (during both contact-dependent and distant culturing). Thus, the effects of cytokines upon angiogenesis in a three-component co-culture (NK cells, trophoblast and endothelium) differed from those revealed previously in single-component (endothelium only) and two-component (co-culture of endothelium and trophoblast) cell models. The results of these experiments indicated that regulation of placental cell interactions involved both cellular contacts and effects produced by cytokines.

Keywords

• endothelial cells
• trophoblast
• natural killer cells
• angiogenesis
• cytokines