Fetal ezrin expression affects macrophages and regulatory T cells in mouse placental decidua

Ezrin is a cross-linker protein between membrane proteins and cytosolic actin, abundantly expressed in the placenta among the ERM protein family. Ezrin gene knockout mice exhibit fetal growth restriction after gestational day (GD) 15.5. This study aimed to clarify the effect of ezrin on immune cells that influence fetal growth and immune tolerance. Ezrin heterozygous knockout (Ez^+/-) mice were interbred, and the gene expressions and immune cell distributions in the placentas of wild-type (Ez^+/+) and ezrin knockout (Ez^-/-) fetuses were analyzed. IL-6 expression in the placenta of Ez^-/- fetuses was significantly higher than in Ez^+/+ fetuses at GD 15.5. The mRNA expression of IL-6 in the uterine decidua attached to Ez^-/- fetuses was higher compared to that attached to Ez^+/+ fetuses but not in the junctional zone and labyrinth. Classical M1 and M2 macrophages in the decidua were analyzed by flow cytometry using CD86 and CD206 as markers. M1 macrophages increased in the decidua attached to Ez^-/- mice compared to Ez^+/+ mice, while M2 macrophages did not increase. CD4-positive T cells showed a reduction in the decidua attached to Ez^-/- fetuses. Further analysis involved the subcutaneous administration of tacrolimus in pregnant Ez^+/- mice from GD 8.5 to GD 15.5, which prevented the decrease in fetal body weight and decidual CD4-positive T cells in Ez^-/- mice at GD 15.5. These results suggest that impaired expression of fetoplacental-derived ezrin induces inflammatory conditions in the uterine decidua through M1 polarization of macrophages, increased IL-6, and decreased CD4-positive T cells, including Treg cells.