Micropreparative Cell Lysate Fractionation in Studying the Effect of Natural Killer Cells on Phenotype, Migration and Apoptosis of Trophoblast Cells in vitro

Abstract

Natural killer (NK) cells are a population of innate immune cells that have cytotoxic functions and are involved in protecting the body from viruses and transformed cells. Placental development is largely determined by the interaction of decidual NK cells and trophoblast cells. During pregnancy, NK cells accumulate around trophoblast cells, while regulating trophoblast proliferation, migration and invasion through the secretion of cytokines and growth factors. The trophoblast, in turn, secretes chemokines and expresses ligands for NK cell adhesion receptors. Thus, functional regulation of trophoblast and NK cells is reciprocal. Despite intensive research, the role of NK cells and methods for correcting their functional activity in reproduction remain controversial. The aim of this study was to assess the effect of NK cell lysate protein fractions on the phenotype, migration and apoptosis of trophoblast cells in an in vitro model experiment, using a new methodological approach. Chromatographic separation yielded six fractions with different protein cargoes. It was found that CD105 (endoglin) expression on the surface of JEG-3 trophoblast cells after their cultivation in the presence of high- (< 250 kDa) or low-molecular-weight (< 45 kDa) fractions of NK-92 whole-cell lysate was reduced compared to spontaneous expression, with the relative count of trophoblast cells with a CD105+ phenotype being also lowered. In addition, one of the low-molecular-weight fractions decreased TRAIL-R2 receptor expression by trophoblast cells. The high-molecular-weight fractions did not enable trophoblast cells to migrate completely through a semi-permeable membrane, with the area occupied by the migrated cells not exceeding the baseline control area. Moreover, the high-molecular-weight fraction containing the TGFβ dimer increased p-SMAD2/3 level in trophoblast cells 1 h after co-culture, followed by a decrease in the level of this phosphorylated form after 2 or more hours, and also elevated procaspase-3 level one day after co-culture. The data obtained hypothetically reflect the possible behavior of chorion cells under the influence of collapsing NK cells in the event of their death under both normal and pathological conditions caused by viral and bacterial infections, as well as other stress factors leading to reproductive pathology.