| Gestation is the whole process of fetal growth and development in uterus. This is a complicated physiological process regulated by many factors. Studies on maternal-fetal interface give significant insight to organ transplantation and tumor therapy.The maternal-fetal interface is composed of decidual tissue, trop hob lasts, lymphocytes, and cytokines. Normal pregnancy is characterized by Th2 predominance at maternal-fetal interface. Human embryo implantation involves a complicated network of molecular signaling that is modulated by endocrine and paracrine pathways. The trop hob last cell at maternal-fetal interface, a special epithelial cell, has high ability in proliferation and invasion and is vital to embryo implantation and placenta formation. During early human pregnancy, extravillous trop hob last cells (EVT) from placenta invade uterine decidual spiral arterioles and mediate the vascular remodeling. As a result, more blood is supplied to the placenta due to low blood pressure and high blood flow. This is essential to facilitate the normal growth and development of the fetus. Failure of invasion to uterus wall may result in clinical pregnancy complications, such as pre-eclampsia, fetal growth restriction, and spontaneous abortion. In contrast, excess invasion may lead to gestational trophoblastic disease.Embryo implantation and placentation are dynamic cellular events that require not only synchrony between the maternal environment and the embryo, but also complicated cell-cell communication amongst the implanting blastocyst and the receptive endometrium. A multitude of factors including endocrine regulators, oxygen concentration, and immune cells contribute to the regulation of EVT functions. Although EVT have strong ability of invasion, it rarely exhibits infinite proliferation and distant metastasis. This indicates that adhesion and invasion of the trophoblast keep dynamic balance due to regulation of cytokines directly or indirectly.Interleukins are a series of bioactive molecules that regulate many important biological functions. These involve delivering message among cells, activating immune system, mediating the activation, proliferation and differentiation of T/B cells, non-specific regulation of immune response, and mediating inflammation. Interleukin-33 (IL-33) is a new member of the IL-1 superfamily of cytokines (expressed by mainly stromal cells) and associates with many diseases. Moreover, IL-33 decreases the expression of E-cadhenrin among cells, and promotes migration of cancer cells.In our previous report, IL-33 and its receptor ST2 have been verified to express in villi and decidua tissue during the first trimester of pregnancy. IL-33 is also evidenced to promote the proliferation and invasion of decidua stromal cells by up-regulating CCL2/CCR2 via the signaling pathway of NF-κB and ERK1/2. Moreover, IL-33 secreted by macrophage at maternal-fetal interface is found to active trophoblast cells via AKT and ERK1/2 signaling pathways, promote the proliferation of trophoblast cells, and play an essential role in formation of placenta. Up to date, the effect of IL-33 on the biological function of trophoblasts, e.g. adhesion and invasion, has not been investigated. In the present study, we aimed to investigate the effect of IL-33 on the adhesion and invasion of trophoblasts, and to explore the corresponding mechanism.1. Expression of IL-33 and its receptor ST2 at maternal-fetal interfaceTo explore the expression of IL-33 and its receptor ST2 at maternal-fetal interface, eight normal pregnant women were chosen. The fresh placenta tissues were collected in the process of cesarean delivery operation. IL-33 and ST2 were examined by immunohistochemical technology. As a result, both IL-33 and ST2 were co-expressed at maternal-fetal interface. IL-33 was primary expressed in nucleus of trophoblast cells, whereas ST2 mainly in cell cytoplasm and membrane of trophoblast cells and stromal cells. These results indicate that IL-33/ST2 probably plays an important role in the formation and function of placenta, and IL-33 may regulate the biological function of trophoblast cells through autocrine and paracrine.2. Effect of IL-33 on adhesion and invasion of trophoblast cellTo investigate the effect of IL-33 on the adhesion and invasion of trophoblast cells, the expression of ST2 was tested in cell lines of JEG-3, JAR, Be Wo, and HTR-8 cell by flow cytometry. Next, the adhesion of trophoblast cells was tested by matrix adhesion kit after treating with rhIL-33 for 48 h. Then the invasion of trophoblast cells in the presence of rhIL-33 was evaluated by transwell. As a result, ST2 expression was observed in JAR, Be Wo and JEG-3 cell line. The highest expression was found in BeWo cell, whereas lowest expression was detected in HTR8 cell. According to previous research, JEG-3 spheroids showed the highest incidence of attachment and the greatest amount of invasion into the underlying endometrial stroma. Therefore, JEG-3 cell line was chosen in this study. After treatment with rhIL-33, the adhesion of JEG-3 cell was significantly decreased in the matrix of Fibronectin, Laminin I, Collagen IV and Fibrinogen. Additionally, the invasion of JEG-3 was decreased in the presence of rhIL-33. These results suggest that IL-33 may regulate the degree of trophoblast cells invasion at maternal-fetal interface by adjusting adhesion and invasion, thus is benefit for the formation of placenta and maintain normal pregnancy.3. Effect of IL-33 on the expression of adhesion related moleculesTo further explore the mechanism of the effect of IL-33 on trophoblast cells’ adhesion, the expression of adhesion related molecules were evaluated in JEG-3 cell with rhIL-33 by flow cytometry. These molecules include integrins, E-cadherin, CD62L, and CD44. The molecules of high expression in trophoblast cell line JEG-3 involve integrin α3β1, integrin α5β1, integrin α6β1, and E-cadherin, whereas integrin α4β1, and CD62L are mid or low expressed, and CD44, and integrin αvβ3 are not expressed. In the presence of rhIL-33, the expression of integrin α4β1 and CD62L are evidently decreased, implying that IL-33 may decrease the adhesion of trophoblast cells through down-regulating these molecules.Conclusively, both IL-33 and its receptor ST2 are expressed in trophoblast cells, which may regulate the biological function of trophoblast cells by autocrine and paracrine. Using JEG-3 cell (a trophoblast cell line with high adhesion and invasion ability), the presence of rhIL-33 is found to decrease the adhesion and invasion of trophoblast cells. The possible mechanism is that IL-33 decreases the expression of adhesion related molecules such as integrin α4β1 and CD62L. By clarifying the function of IL-33 in trophoblast cells, the present study provides insight into the rational design of strategy to cure the gestation related diseases, such as recurrent spontaneous abortion and pregnancy trophoblast diseases. |
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