PROBLEM: Impaired trophoblast invasion during the first trimester of pregna
ncy is linked to spontaneous abortion, and defective invasion in the second
trimester to hypertension + proteinuria (pre-eclampsia). Hypertension deve
loping during the third trimester of human pregnancy represents, in part, a
corrective response in the mother to provide adequate placental perfusion
for fetal growth when trophoblast has not to invaded and converted the myom
etrial porprtion of maternal spiral arteries into to low resistance-high ca
pacitance conduits. Deportation of vesicles from hypoxemic trophoblast is t
hought to cause hypertension plus proteinuria, vascular damage and a system
ic coagulopathy. Trophoblast invasion may be inhibited by local cytokines,
such as TGF-beta but Th1-type cytokines associated with pre-eclapmsia and s
pontaneous abortions (e.g., IL-1, TNF-alpha, IFN-gamma) are not known to in
hibit migration at in situ concentrations. Trophoblast invasion is also inh
ibited by the binding of surface integrins to fibronectin and fibrin, and f
ibrin production is stimulated by these Th1. cytokines via up-regulation of
prothrombinases(s) such as fgl2 which directly and via TNF-alpha -facilita
ted inflamation compromise trophoblast cell integrity. We, therefore, asked
if fgl2 expression and TNF-alpha are increased in first trimester human mi
scarriage and in third trimester pre-eclampsia.
METHODS: fgl2 mRNA was detected using in situ hybridization and fgl2 protei
n by immunohistochemistry. TNF-alpha mRNA and protein were similarly tested
. The techniques were validated using uterine sections from day 8.5 of CBA
x DBA/2 pregnancies, and then were applied to sections of placentae from no
rmal and pre-eclamptic pregnancies with and without intrauterine fetal grow
th restriction (IUGR). Fibrin was detectectd by immunohistochemistry.
RESULTS: Expression of fgl2 protein correlated with fgl2 mRNA expression in
mouse uteri and in placentae from normal human pregnancies. Increased expr
ession of fgl2 and TNF-alpha mRNA and protein, and increased fibrin deposit
ion was detected in placental trophoblast.
CONCLUSIONS: Activation of fgl2 prothrombinase by Th1-type cytokines in pre
gnancy may lead to spontaneous abortion, or in ongoing pregnancy, to pre-ec
lampsia and/or IUGR.