The cell adhesion molecule, VCAM-1, is selectively elevated in serum in pre-eclampsia: does this indicate the mechanism of leucocyte activation?

Placental pathologic features of preterm preeclampsia

OBJECTIVE

Our purpose was to compare the incidence and interrelationships of uteroplacental vasculopathy and chronic inflammatory and placental vasoocclusive lesions in preeclampsia and spontaneous delivery before 32 weeks' gestation.

STUDY DESIGN

Review of singleton live-born nonanomalous infants born at 22 to 32 weeks' gestation identified 76 cases of preeclampsia and 353 cases of spontaneous prematurity (spontaneous premature membrane rupture [n = 192], preterm labor, intact membranes [n = 161]). Histologic lesions were considered as belonging to one of five major pathophysiologic groups: (1) uteroplacental vascular lesions and related villous lesions, (2) chronic inflammatory lesions, (3) coagulation-related lesions, (4) acute inflammatory lesions, and (5) unclassified lesions. Contingency table analyses considered p < 0.05 significant. Factor analysis extracted combinations of related variables.

RESULTS

More frequent in preeclampsia versus spontaneous prematurity were chronic uteroplacental vasculitis (29% vs 20%, p < 0.05), chronic villitis (20% vs 3%, p < 0.001), avascular villi (39% vs 16%, p < 0.001), and "hemorrhagic endovasculitis" (9% vs 2.5%, p < 0.03). In the preeclampsia cases factor analysis extracted 13 categories of related lesions. Four categories contained uteroplacental vascular lesions. Five categories included lesions related to chronic inflammation, and eight included lesions related to coagulation. Four categories loaded lesions from one major pathophysiologic group only. Three categories loaded lesions from all three pathophysiologic groups. Unclassified lesions loaded into two factor categories that were unrelated to the other lesions.

CONCLUSIONS

Chronic inflammatory and placental vasoocclusive lesions are more common in preterm preeclampsia than in spontaneous prematurity. Immunopathologic processes and coagulation may be involved in the pathophysiologic mechanisms of preterm preeclampsia independent of uteroplacental vascular pathologic features.

Nitric oxide concentrations are increased in the fetoplacental circulation in preeclampsia

OBJECTIVE

The aim of this study was to measure serum concentrations of total nitrites, as an index of nitric oxide synthesis, in the maternal and fetal circulations of normal pregnancies and in pregnancies complicated by preeclampsia.

STUDY DESIGN

We studied 32 women with preeclampsia and 36 with uncomplicated pregnancies. Maternal venous blood samples were collected from all of the patients, and umbilical venous blood was collected from 13 of the preeclamptic group and 17 of the control group. Serum nitric oxide concentrations were determined with the Greiss reaction by measuring combined oxidation products of nitric oxide, serum nitrite and nitrate after reduction with nitrate reductase.

RESULTS

There were no significant differences in maternal serum nitrite concentrations between the groups (control group 29.8 +/- 1.07 mumol/L, preeclamptic group 29.5 +/- 1.06 mumol/L). Significantly higher serum nitrite concentrations were found in umbilical venous serum in the preeclamptic group compared with the control group (34.59 +/- 1.12 mumol/L vs 23.90 +/- 1.05 mumol/L, p < 0.01).

CONCLUSIONS

Total nitrites are increased in the fetoplacental circulation in preeclampsia. These results support the hypothesis that increased nitric oxide production may be a compensatory response to improve blood flow or may play a role in limiting platelet adhesion and aggregation.

Pre-eclampsia: physiology and immunological aspects

Pre-eclampsia is a frequent, unpredictable syndrome which is dangerous for both mother and foetus. The concept of placental ischemia has gained wide acceptance among the numerous theories put forward to explain the illness. The setting up of preeclampsia seems to be scheduled in two steps: (1) an absolute or relative placental ischemia due to vascular diseases or hypertrophic placenta, or most often secondary to implantation defect, particularly anomaly with the invasive trophoblast; (2) a diffuse endothelial disease. The connection between these two steps is incompletely disclosed. The authors demonstrate that the maternal immune system which is strongly stressed during all the stages of normal gestation is implicated in pre-eclampsia. Its role is probably not univocal. Foeto-trophoblastic antigens could be poorly recognised. This defect of recognition could lead to the abnormalities of trophoblastic invasion observed in pre-eclampsia. Pre-eclampsia does not seem to be accompanied by an immunological rejection of the foetus. Some genetically predisposed patients do not have a sufficiently competent immune system to neutralise one or more of the toxic products released by the ischemic placenta. Certain types of pre-eclampsia could be auto-immune, with the auto-antibodies directed against certain types of phospholipids or trophoblastic constituents. A disequilibrium between oxidation and anti-oxidation mechanisms involving neutrophils could lead to aggression of the endothelium which is observed in pre-eclampsia. Pre-eclampsia could represent a form of immuno-dystrophy, with the excessive production of adverse cytokines locally, directed against the trophoblast. Without directly implicating the immune system as the trigger of pre-eclampsia, it seems that its role is unclear. In some cases it develops protective mechanisms which, when overwhelmed or inadequate, allows pre-eclampsia to occur. In other cases it can form part of the cascade of aggressions leading to the abnormalities encountered. The integration of these abnormalities in the pathophysiological models, could help improve the classification of pre-eclampsia. This attempt will lead to a more adapted preventive and therapeutic management of pre-eclampsia.