Function and Dysfunction of Fibrinogen-Like Protein 2 in Reproductive Success and Preeclampsia

Title: Function and Dysfunction of Fibrinogen-Like Protein 2 in Reproductive Success and Preeclampsia
Authors: Robineau-Charette, Pascale
Date: 2021-04-14
Abstract: Fibrinogen-like protein 2 (FGL2) is a known immunomodulator and prothrombinase, expressed by several subsets of immune cells. This thesis explores its potential role during the establishment of pregnancy, in mice, as well as in trophoblast function and in an immune-mediated subtype of preeclampsia (PE), in humans. We first noticed a marked subfertility in Fgl2 knockout (ko) and Fgl2 overexpressing (tg) colonies, where litters were fewer and smaller. To explain this, we mapped spatiotemporal patterns of FGL2 expression in the female reproductive tract and through the estrous cycle. FGL2 is expressed in the ovarian stroma and theca cell layer, peaking shortly before ovulation. Fgl2 ko and tg mice do not show a defect in natural or induced ovulation. FGL2 is expressed in secretory cells of the oviductal epithelium, and Fgl2 ko mice have reduced fertilization efficiency. Fgl2 tg pups are noticeably small, and we find that a reduced ratio of glycogen cells in the junctional zone of their placenta partly explains this. We next investigated the role of FGL2 in trophoblast function, using BeWo and HTR-8/SVneo cell lines. Inflammatory cytokines increase FGL2 expression in BeWo, and FGL2 overexpression promotes syncytialization. We show that it therefore rescues the deleterious effect of inflammation on syncytium formation. In a large cohort of PE and non-PE human placentas, FGL2 is high in a subtype with immune activation, and low in a canonical, anti-angiogenic subtype. Its expression correlates with incidence of chronic inflammatory histopathological lesions, likely driven by immune rejection gene sets. High FGL2 also associates with a high incidence of fibrin deposition in the placenta. Overall, we conclude that FGL2 is involved in several steps of maternal immune adaptation, both before and after pregnancy. Its absence and excess both contribute to mouse subfertility. In the developing and mature placenta, FGL2 is increased by inflammation in the trophoblast and immune compartment of the mature placenta, as a physiological attempt to re-establish immune equilibrium and protect the ongoing pregnancy.
CollectionThèses, 2011 - // Theses, 2011 -