The Regulatory Mechanism Of Human First-trimester Trophoblast Cells And Decidual Stromal Cells On Peripheral And Decidual NK Cells

The embryo expresses foreign antigens to mother, and thus has been viewed as allograft, and induction of maternal immune tolerance toward the fetus becomes an important event in the maintenance of pregnancy. The excessive activation of maternal immuno-competent cells against embryo antigen results in rejection to the fetus and pregnancy wastage. The mechanisms of maternal-fetal immune regulation during pregnancy and improvement of the pregnant outcome are of great interest for researchers in reproductive medicine.The maternal-fetal interface is the core part of maternal-fetal immune network. The maternal-fetal interface is composed of trophoblasts and maternal decidual cells. The cell composition in the decidua is very complicated and special. Decidual stromal cells (DSCs) population accounts for75%in all the decidual cells of the early pregnancy, and decidual immune cells (DICs) account for15%. DICs have an unusual composition:more than70percent of them are CD56brightCD16-NK.We propose to investigate the role of CXCL12/CXCR4signal in the regulation of maternal-fetal functional cells on peripheral NK and decidual NK cells, leading to Th2bias and maternal-fetal immune tolerance.1. The differential functional phenotype of human peripheral and decidual NKWe isolated peripheral NK cells from normal pregnancy woman’s peripheral blood and decidual NK cells from normal early pregnancy decidual tissue, and then used FCM to determine the cytokine expression and cytotoxicity of peripheral and decidual NK cells. It has been found that the peripheral NK cells express higher activated receptor CD16and NKp44, and lower level of inhibitory receptor KIR2DL1compared to the decidual NK cells. Higher level of Thl cytokine TNF-α was observed in peripheral NK cells than that of decidual NK cells. However, Th2cytokines were expressed significantly higher in decidual NK cells than that of peripheral NK cells. Similarly, the cytotoxicity of peripheral NK cells is higher than that of decidual NK cells. NK cells are the predominant lymphocytes in decidual tissue during the first trimester pregnancy. This phenotype in decidual NK cells presents an important factor contributing to immunotolerance at maternal-fetal interface in the early pregnancy.2. The functional modulation of human first-trimester trophoblast cells and decidual stromal cells on peripheral and decidual NK cells.The first-trimester human trophoblast cells and DSCs was isolated and identified as our previous study. After co-cultured respectively with trophoblast cells, DSCs or trophoblasts-DSCs unit for48hours, the peripheral and decidual NK cells were collected and analyzed by FCM and cytotoxicity assay, respectively. We found that the first-trimester human trophoblast cells and DSCs could modulate the phenotype, Thl/Th2cytokine expression and cytotoxicity of peripheral and decidual NK cells, contributing to maternal-fetal immune tolerance.3. CXCL12/CXCR4is involved in the functional modulation of human first-trimester trophoblast cells and decidual stromal cells on peripheral and decidual NK cellsAfter isolation and culture of human first-trimester trophoblast cells and DSCs, the secretion of CXCL12by these cells was determined by ELISA. The supernatant was collected from human first-trimester trophoblast cells, DSCs, and their coculture. Peripheral and decidual NK cells were pre-treated with CXCR4antagonist, then co-cultured with trophoblasts, DSCs, or trophoblasts and DSCs coculture for48h. Human peripheral and decidual NK cells were harvested and the phenotype, Thl/Th2cytokine expression and cytotoxicity of NK cells were examined by FCM and LDH release assay, respectively. It was found that human recombinant CXCL12could enlarge, and CXCR4blockage abrogate the modulation of trophoblast cells and DSCs on the peripheral and decidual NK cells. The effect of trophoblast cells and DSCs on peripheral and decidual NK cells is via the CXCL12/CXCR4signal pathway.4. MAPK signal pathway is involved in the functional modulation of human first-trimester trophoblast cells and decidual stromal cells on peripheral and decidual NK cellsPeripheral NK cells were pre-treated with JUNK1/2/MAPK signal pathway inhibitor SP600125, P38/MAPK signal pathway inhibitor SB202190and ERK/MAPK signal pathway inhibitor U0126, then detect the phenotype, Thl/Th2cytokine expression and cytotoxicity of NK cells. We found that blocking JUNK1/2/MAPK and ERK/MAPK signal pathway can abrogate the modulation of trophoblast cells and DSCs on the peripheral and decidual NK cells. MAPK signal pathway is involved in the functional modulation of human first-trimester trophoblast cells and decidual stromal cells on peripheral and decidual NK cells.