Decidual Macrophages Are Significantly Increased in Spontaneous Miscarriages and Over-Express FasL

Decidual macrophages (DM) are the second most abundant population
in the fetal-maternal interface. Their role has been so far
identified as being local immuno-modulators favoring the maternal
tolerance to the fetus. Herein we investigated tissue samples from
11 cases of spontaneous miscarriages and from 9 cases of elective
terminations of pregnancy. Using immunohistochemistry and dual
immunofluorescence we have demonstrated that in spontaneous
miscarriages the DM are significantly increased. Additionally, we
noted a significant up-regulation of macrophage FasL expression.
Our results further support a dual role for DM during pregnancy and
miscarriages. We hypothesize that the baseline DM population in
normal pregnancy is in line with an M2 phenotype supporting the
ongoing gestation. In contrast, during spontaneous miscarriages,
the increased FasL-expressing population could be a part of an M1
phenotype participating in Fas/FasL-related apoptosis. Our results
highlight a new aspect of macrophage biology in pregnancy
physiology and pathophysiology. Further studies with larger samples
are needed to verify the current results and evaluate their
clinical impact.