Débats actuels sur l’immunologie de la prééclampsie. Comptes rendus du sixième colloque international de La Réunion (décembre 2008)

Expression of placental glycans and its role in regulating peripheral blood NK cells during preeclampsia: a perspective

Preeclampsia is a pregnancy-related multisystem disorder characterized by altered trophoblast invasion, oxidative stress, exacerbation of systemic inflammatory response, and endothelial damage. The pathogenesis includes hypertension and mild-to-severe microangiopathy in the kidney, liver, placenta, and brain. The main mechanisms involved in its pathogenesis have been proposed to limit trophoblast invasion and increase the release of extracellular vesicles from the syncytiotrophoblast into the maternal circulation, exacerbating the systemic inflammatory response. The placenta expresses glycans as part of its development and maternal immune tolerance during gestation. The expression profile of glycans at the maternal-fetal interface may play a fundamental role in physiological pregnancy changes and disorders such as preeclampsia. It is unclear whether glycans and their lectin-like receptors are involved in the mechanisms of maternal-fetal recognition by immune cells during pregnancy homeostasis. The expression profile of glycans appears to be altered in hypertensive disorders of pregnancy, which could lead to alterations in the placental microenvironment and vascular endothelium in pregnancy conditions such as preeclampsia. Glycans with immunomodulatory properties at the maternal-fetal interface are altered in early-onset severe preeclampsia, implying that innate immune system components, such as NK cells, exacerbate the systemic inflammatory response observed in preeclampsia. In this article, we discuss the evidence for the role of glycans in gestational physiology and the perspective of glycobiology on the pathophysiology of hypertensive disorders in gestation.

Hypertensive pathologies and egg donation pregnancies: Results of a large comparative cohort study

OBJECTIVE

To determine whether egg donation (ED) pregnancies are at higher risk of pregnancy-induced hypertension (PIH) than those achieved by autologous assisted reproductive technology (ART; controls).

DESIGN

Anonymous comparative observational matched cohort study.

SETTING

Assisted reproductive technology centers.

PATIENT(S)

Two hundred seventeen ED and 363 control singleton pregnancies matched at 7-8 weeks (pregnancy date, parity, cycle type [fresh/frozen] and women's age). According to French practice, all women were under 45.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Percentage of PIH for ED versus controls.

RESULT(S)

The groups were comparable (mean age, 34.5). PIH was more frequent during ED pregnancies (17.8% vs. 5.3%), as was preeclampsia (11.2% vs. 2.8%) and eclampsia (1.8% vs. 0.0%). In multivariate analyses, PIH risk increased with ED (odds ratio [OR], 3.92; 95% confidence interval [CI], 1.93-7.97) and women's age (OR, 1.08; 95% CI, 1.00-1.16). No significant effect of previous pregnancies or cycle rank/type was observed.

CONCLUSION(S)

This study had sufficient power to detect doubling of the PIH rate. It was demonstrated that the risk of PIH was tripled for ED versus controls. Even in young women, ED is a risk factor for PIH. An immunological explanation seems most likely, that is, the fetus is fully allogeneic to its mother. This risk must be acknowledged to inform couples and provide careful pregnancy monitoring.

C3F gene mutation is involved in the susceptibility to pre-eclampsia

OBJECTIVE

The aim of this study was to analyze the functional polymorphism of exon 3 of the gene of complement component C3 (rs 2230199) to identify the potential involvement of the mutated gene C3F in the genesis of pre-eclampsia.

MATERIEL AND METHODS

It is a comparative case-control study conducted in the university center of maternity and neonatology of Monastir with collaboration of high institute of biotechnology (Tunisia) on a period of 2 years. Two hundred and fifty patients and 96 newborns divided into pre-eclampsia group (150 parturients with pre-eclampsia and 48 newborns) and control group (100 parturients with normal pregnancy and their 48 infants) are taken. Each patient and control were sampled for the phenotypic study and the molecular analysis. The ARMS-PCR (amplification refractory mutation system) was the standard procedure in our study. A simple observation let to distinguish three cases of genotypes: SS, FF and SF.

RESULTS

In the control group, 56% of parturients had the genotype SS, 38%, the genotype SF and 6%, FF genotype. In the pre-eclamptic population, SS, SF, and FF genotypes were determined, respectively, 40, 45.30 and 14.60% of the patients. There is a sharp increase in the frequency of the FF genotype in pre-eclamptic patients compared to controls (14.60 vs. 6%). The difference was statistically significant (p = 0.01). The frequencies of C3S and alleles C3F determined in controls (respectively, 74 and 26%) were different from those identified in pre-eclamptic patients (respectively, 62.60 and 37.30%). This difference was statistically significant (p = 0.005). The C3S and C3F allele frequencies determined in control newborns (respectively, 83.33 and 16.66%) were slightly different from those identified in newborn issued from pre-eclamptic patients (respectively, 80.2 and 19.79%), but the difference was not statistically significant (p = 0.67).

CONCLUSION

The gene polymorphism of complement component C3 was significantly associated with the onset of pre-eclampsia. These results should be confirmed by other studies looking at larger scale to consider this gene as a new biomarker with predictive potential therapeutic consequences.

Sera from early-onset, severely preeclamptic women directly modulate HLA-E expression in the EA.hy296 endothelial cell line

The expression of endothelial HLA-E in the context of the systemic inflammatory response observed in preeclampsia has not been established. An experimental study was designed to determine the effect of the sera of pregnant women on the expression of HLA-E in EA.hy296 endothelial cells. First, measurements of protein fractions were performed in sera from early-onset, severely preeclamptic women without HELLP syndrome, in which there was no significant difference in total proteins between the groups, but a reduced level of plasma albumin and an increase in α1-globulin were observed in both groups of pregnant women compared with non-pregnant women. Measurements of colloid osmotic pressure (COP) using a recalculated albumin/globulin ratio formula determined only a significant decrease in COP in all pregnant groups compared with non-pregnant women. The expression of membrane HLA-E was increased in EA.hy296 endothelial cells stimulated with sera of early-onset, severely preeclamptic women, while recombinant interferon-γ (IFN-γ) significantly reduced the expression of membrane HLA-E. Pro-inflammatory cytokines were measured by Luminex in the serum samples, and increased levels of tumor necrosis factor (TNF) and decreased levels of IFN-γ were observed in early-onset, severe preeclampsia compared with normal pregnancy. Moreover, soluble HLA-E was detected in these serum samples by Western blot and ELISA, but no significant difference was found. This raises the possibility that a systemic inflammatory response promotes a compensatory mechanism of COP balance in severe preeclampsia by release of inflammation-induced factors, including endothelial HLA-E. Evidence is now provided regarding HLA-E expression by EA.hy296 cells.

Cytokine production by non-stimulated peripheral blood NK cells and lymphocytes in early-onset severe pre-eclampsia without HELLP

Preeclampsia involves an exacerbated maternal inflammatory response that suggests a possible role of innate immunity. NK cells can promote this kind of response through cytokine production and the expression of activating or inhibitory receptors. The aims of the present study were to explore cytokine production by peripheral blood mononuclear cells, as well as cytotoxic ability and receptor expression for HLA-E and HLA-G molecules in peripheral natural killer (NK) cells of women with early-onset severe preeclampsia without HELLP (hemolysis, elevated liver enzyme levels and a low platelet count) syndrome. The expression of the ILT2, KIRDL4, NKG2A, and NKG2C receptors and of cytotoxic activity was measured in non-stimulated NK cells, whereas the intracellular expression of IL-4, IL-10, IL-13, IL-12, IFNγ, TNF and VEGF, was assessed in non-stimulated peripheral blood mononuclear cells subsets using flow cytometry. Circulating soluble HLA-G was also determined by ELISA. The intracellular cytokines tested were significantly higher in NK cell subsets from severely preeclamptic women compared with the control group. On the other hand, the percentage of NK cells expressing NKG2A or NKG2C and the cytotoxic activity of NK cells were significantly higher in severely preeclamptic women. Furthermore, there was a significant correlation between urine protein concentration and soluble human leukocyte antigen G (soluble HLA-G) in serum. We conclude that patients with early-onset severe preeclampsia without HELLP syndrome have increased NK cell function related to cytokine production, cytotoxicity and expression of lectin-like receptors such as NKG2.

[Sixty-nine consecutive cases of eclampsia: prodromes and circumstances]

OBJECTIVE

To specify clinical and biological characteristics of patients developing eclampsia, and identify atypical eclampsia without prior signs and symptoms of severe preeclampsia.

PATIENTS AND METHODS

This was a retrospective observational study conducted from January 1996 to December 2008 in a maternity type IIB in French Guiana. Data of patients who experienced eclampsia were collected from obstetric records.

RESULTS

Sixty-nine patients were selected among 21,525 patients who delivered during this period, corresponding to a prevalence of 3.2 ‰. The average patient age was 21 years (range from 12 to 45 years). Sixty-six percent of patients were nulliparous. The gestational age was greater than 37 weeks of gestation for 62% of patients, between 26 and 37 weeks of gestation for 36% and less than 26 weeks of gestation for 2% of patients. Two thirds of the patients had been examined less than a month before the eclamptic seizure, blood pressure was normal in 62% of cases. Seventy-four percent of patients had at least one Doppler study of the uterine and umbilical arteries velocimetry, the Dopplers studies were normal in 78% of cases. The eclampsia occurred in ante-, peri- and post-partum in 59, 6 and 35% of the cases, respectively 10% of patients were hospitalized for preeclampsia at the time of eclamptic seizure. Less than 10% of patients developed HELLP syndrome. One patient had died of aspiration pneumonia. Newborns had a mean birth weight over 2500 g in 88% of cases. During the follow-up period, 41% of the patients had subsequent pregnancies with 62% without hypertension, 24% complicated by recurrent gestational hypertension, 24% by preeclampsia and 4% by eclampsia.

DISCUSSION AND CONCLUSION

In a majority of the patients in our study, eclampsia was the main manifestation, and only 10% were preceded by severe preeclampsia. These results are comparable to recent studies, which found in their series that 40 to 60% of eclampsia manifested without preeclamptic prodromi. Eclampsia can occur after an unremarkable pregnancy, in women without risk factors, and then it is hardly predictable. Prenatal follow-up must be very cautious paying attention to any markers such as intermittent hypertension, functional symptoms or appearance of proteinuria.

Low neonatal birth weight as a possible predictive factor for the onset of postpartum eclampsia

OBJECTIVE

To report about a case of complicated late postpartum eclampsia where neonatal low birth weight could be considered a predictive factor of placental sufferance.

METHODS

A 25-year-old woman, without medical or familiar history for hypertension or cerebrovascular diseases, underwent a normal spontaneous delivery with neonatal birth weight of 2340 g (9th percentile). Eight days later the patient presented sudden headache and generalized tonic-clonic seizures.

RESULTS

Blood hypertension and alterations in laboratory studies were detected; a diagnosis of late postpartum eclampsia was made. A CT scan showed subarachnoid hemorrhage (Hunt and hess grade I, Fisher grade III). Serial cerebral angiograms did not show any intracranial vascular malformations; epilepsy and hypertension were successfully medically treated; and a repeat CT examination showed the gradual resolution of subarachnoid hemorrhage. Headache progressively disappeared.

CONCLUSIONS

Low neonatal birth weight could be linked to placental dysfunction and considered as a predictive factor for the onset of postpartum preeclampsia/eclampsia. We recommend a careful clinical and laboratory management of puerperium up to the first month postpartum, in particular in cases of "sine causa" neonatal low birth weight.

Implication of expression of osteopontin and its receptor integrin alphanubeta3 in the placenta in the development of preeclampsia

To investigate the expression of osteopontin (OPN) and its receptor integrin alphanubeta3 in the placental tissue from pregnant women complicated with preeclampsia, the expression of OPN and alphanubeta3 in the placenta of the pregnant women with preeclampsia and healthy pregnant women was detected by immunohistochemistry, Western blotting and RT-PCR. Our results showed that OPN and alphanubeta3 protein were expressed in the placenta from normal pregnant woman and those with preeclampsia. OPN was located in the placental syncytiotrophoblasts and the cytoplasm of capillary endothelial cells and integrin alphanubeta3 was mainly expressed on the surface of trophoblast cells. Expression of OPN and integrin alphanubeta3 in the placental tissue from preeclampsia subjects was significantly lower than that from the control group (P<0.05). Compared with the control group, expression of OPN in the placental tissue from preeclampsia group was significantly lower (P<0.05) but there was no significant difference in the expression of alphanu and beta3 between the preeclampsia group and the controls. It is concluded that OPN and its receptor integrin alphanubeta3 may be involved in the pathogenesis of preeclampsia.