Abstract
An inflammatory-like process and vascular remodeling represent the main changes that occur in decidua in the early phase of pregnancy. These changes are partly induced by trophoblast cells that colonize the decidua and are also contributed by the complement system, which can easily be activated as a result of tissue remodeling. Local control by several complement regulators including surface-bound and soluble molecules is critical to prevent complement-mediated tissue damage in normal pregnancy. C7 expressed on the endothelial cells (ECs) surface has been recognized as a novel complement regulator involved in the control of the proinflammatory effect of the terminal complement complex. The protective role of placental complement regulators in pregnancy is underscored by the recent finding of an association of preeclampsia with mutations in the genes encoding for some of these proteins. Complement components produced at feto-maternal interface serve an important function in placental development. C1q synthesized by decidual ECs and expressed on the cell surface is particularly important in this regard because it acts as a molecular bridge between endovascular trophoblast and ECs. C1q is also produced by extravillous trophoblast and is used to favor trophoblast migration through the decidua. Defective expression of C1q by trophoblast is associated with impaired trophoblast invasion of decidua and may have important implications in pregnancy disorders such as preeclampsia characterized by reduced vascular remodeling.
Highlights
During the early phase of pregnancy the endometrium of the uterus undergoes profound changes and transforms into decidua, a newly formed tissue that plays a critical role for successful embryo implantation and regular fetal growth
These changes are partly induced by trophoblast cells that colonize the decidua and are contributed by the complement system, which can be activated as a result of tissue remodeling
C1q synthesized by decidual endothelial cells (ECs) and expressed on the cell surface is important in this regard because it acts as a molecular bridge between endovascular trophoblast and ECs
Summary
During the early phase of pregnancy the endometrium of the uterus undergoes profound changes and transforms into decidua, a newly formed tissue that plays a critical role for successful embryo implantation and regular fetal growth. The decidua provides a physical anchorage for the implanted embryo tightly attached to the maternal tissue by means of anchoring villi surrounded by an outer layer of trophoblasts that form cell columns. A vigorous response may be mounted against paternal antigens expressed on trophoblasts leading to potential deleterious effects on fetal survival. To avoid these undesired consequences, different strategies are developed to prevent an immunologic attack of the mother against the fetus while keeping intact the protective function against harmful pathogens. Hormonal changes contribute to the development of inflammation in maternal decidua in the early pregnancy as suggested by the observation that a similar process, though less intense, occurs in non-pregnant www.frontiersin.org
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