Lisbeth Vercruysse

Placental bed spiral arteries in the hypertensive disorders of pregnancy

Objective— The investigation of the histology of the placental bed spiral arteries in normal pregnancy and in pregnancies complicated by hypertension, with or without proteinura.

THE “GREAT OBSTETRICAL SYNDROMES” ARE ASSOCIATED WITH DISORDERS OF DEEP PLACENTATION

Defective deep placentation has been associated with a spectrum of complications of pregnancy including preeclampsia, intrauterine growth restriction, preterm labor, preterm premature rupture of membranes, late spontaneous abortion, and abruptio placentae. The disease of the placental vascular bed that underpins these complications is commonly investigated with targeted biopsies. In this review, we critically evaluate the biopsy technique to summarize the salient types of defective deep placentation, and propose criteria for the classification of defective deep placentation into 3 types based on the degree of restriction of remodeling and the presence of obstructive lesions in the myometrial segment of the spiral arteries.

Agonistic Autoantibodies to the AT1 Receptor in a Transgenic Rat Model of Preeclampsia

We used rats transgenic for the human angiotensinogen (hAogen) gene and the human renin (hRen) gene and crossed the strains to produce a model of preeclampsia in the dams. The female (n=9) hAogen × male hRen cross had severe (telemetry-measured) hypertension and albuminuria, which developed during the last trimester of pregnancy and subsided after delivery. The converse cross (n=9) and control (n=9) SD rats did not. We demonstrated that the female hAogen × male hRen cross had agonistic antibodies capable of activating the angiotensin (Ang) II AT1 receptor (AT1R-AA) and defined the epitope on the receptor’s second extracellular loop. The phenomenon also occurs in humans with preeclampsia. The rats displayed renal histology reminiscent of preeclampsia, including fibrin deposition confined to the glomeruli. The complement system was activated in glomeruli and IgG deposits were present that may represent AT1R-AA. Finally, we observed an atherosis-like lesion in the spiral arteries of the placental bed, which we called placental-bed arteriolosclerosis. Our model may be relevant to preeclampsia in humans.

Immunolocalization of tumour necrosis factor-α (TNF-α) in the placental bed of normotensive and hypertensive human pregnancies

Abstract To identify tumour necrosis factor (TNF)-γ immunopositive cells, third trimester human placental bed biopsies were selected from nine normotensive control women, 16 severely pre-eclamptic patients and seven patients with pre-existing hypertension with superimposed pre-eclampsia. In addition, five first and early second trimester specimens were included in the study. Immunostaining was performed with a mouse IgGI monoclonal antibody (J1 D9) reactive specifically with human TNF-α (1 : 300 ascitic fluid), using a biotin-streptavidin-peroxidase technique. Variable staining of stromal cells was noted in all biopsies. Specimens of early pregnancy showed marked immunostaining for TNF-a on proliferating tips of anchoring villi, invasive interstitial cytotrophoblast (but not the multinuclear giant cells), and endovascular trophoblast invading the spiral arteries. At term, weak staining was found in trophoblast incorporated within spiral artery walls. In biopsies from pre-eclamptic patients, spiral arteries without physiological change showed very little staining except in atherotic vessels where the infiltrated lipophages often showed intense immunolabelling. The marked presence of TNF-a in extravillous cytotrophoblast of young specimens is suggestive of a role in early invasion. Immunostaining of foam cells in non-invaded spiral arteries in pre-eclampsia at or near-term indicates a potential role of this cytokine in the development of atherotic lesions.

Interaction of interstitial trophoblast with placental bed capillaries and venules of normotensive and pre-eclamptic pregnancies

While endovascular trophoblast invasion of the human placental bed spiral arteries has been studied extensively, no information is available on the interaction between interstitially invading trophoblast and uterine capillaries and venules. Placental bed biopsies of eight normotensive and 15 pre-eclamptic patients were double-immunostained for cytokeratin and the endothelial marker CD31, providing satisfactory staining results in six and 10 biopsies, respectively. Interstitial trophoblast tissue density did not differ between the two series of biopsies, implying that this pathway of invasion is not impaired in pre-eclampsia. Both groups showed a similar incidence of approach of non-arterial vascular structures by perivascular trophoblast. Differences in CD31 staining intensity were noticed in different vascular cross-sections. Lower staining intensity was related to the presence of perivascular trophoblast. Because of the identity of CD31 with the platelet-endothelial cell adhesion molecule (PECAM)-1, the trophoblast-dependent downregulation of CD31 may play a role in the control of leukocytic traffic within the placental bed. The phenomena described in this paper did not show any difference between the normotensive and pre-eclamptic patients, implying that interaction of interstitial trophoblast with venous and capillary structures is not related to the pathogenesis of pre-eclampsia.

Endovascular trophoblast invasion, spiral artery remodelling and uteroplacental haemodynamics in a transgenic rat model of pre-eclampsia

The aim of the present study was to evaluate the depth of endovascular trophoblast invasion and associated remodelling of spiral arteries in a transgenic model of pre-eclampsia in the rat, a species showing a comparable deep invasion during normal pregnancy as the human. Pre-eclamptic (PE) transgenic rats (TGR) (hAngiotensinogen female x hRenin male) and non-PE reversely mated (RM) TGR rats were compared to normal Sprague-Dawley rats (C). Day 18 implantation sites were collected and the presence of endovascular trophoblast, fibrinoid, endothelial and smooth muscle cells were evaluated in spiral arteries in three parallel layers in the mesometrial triangle using an image analysis system (KS-400). In a separate group of animals peak-systolic and end-diastolic velocities were measured by Doppler in uterine and arcuate arteries, and the resistance indices (RI) were calculated. In PE and RM rats, the entire mesometrial triangle contained significantly more endovascular trophoblast and vascular fibrinoid deposits than the C group. No difference was found between the groups in the overall amount of smooth muscle surrounding the lumen, but in the PE and RM groups significantly more muscle was present in parts of the contours covered by trophoblast. There was significantly less CD31-positive endothelium in the total lumen contours of the PE and RM groups than in the C group, but in parts of the contours covered by trophoblast more residual endothelium was present in both TGR groups. Comparison of the three layers indicated deeper invasion in both the PE and RM groups than in the C group. By Doppler analysis of the proximal uterine artery the RI was found to be significantly lower in the PE and the RM group than in the C group. In the arcuate artery, the RI was significantly lower in the PE group as compared to the RM and C groups. We conclude that in this transgenic PE rat model there is deeper endovascular invasion of spiral arteries and decreased RI of uterine arteries at day 18 of pregnancy.

Fetal-Maternal Conflict, Trophoblast Invasion, Preeclampsia, and the Red Queen

The much publicized conflict hypothesis for understanding fetal-maternal interaction during pregnancy often invokes a ‘battle’ metaphor, rather than a well orchestrated interplay occurring as a series of well controlled moves and counter-moves as happens in a game of chess. Such stepwise interaction is particularly obvious in the spiral artery remodelling process, and it would be interesting to trace the history of the successive steps in histological adaptation throughout primate phylogeny. The restricted invasion observed in a few species on a ‘lower’ evolutionary scale suggests a tendency of progressive deeper invasion during primate evolution. Unfortunately, our knowledge of invasive processes in the placental bed in nonhuman primates is highly inadequate. A paradigm underscoring the stepwise interaction between mother and fetus may be provided by the Red Queen hypothesis, which is a useful model to explain co-evolutionary processes between different species. The apparent association between preeclampsia and restricted endovascular trophoblast invasion, combined with the absence of the disease in primate species showing shallow invasion, suggests that preeclampsia may result from a failure in one or more interactive steps necessary for deeper invasion. Evidence for a genetic component invokes the puzzling question as to why “preeclampsia genes” are not eliminated from human populations. As in other fields of medicine, a proper understanding of Darwinian selection processes may throw some light on the causes of preeclampsia.

Evaluation of trophoblast invasion in placental bed biopsies of the baboon, with immunohistochemical localisation of cytokeratin, fibronectin, and laminin

Abstract: Biopsies of placentas (n = 21), placental bed (n = 17) and decidua (n = 26) of various gestation periods (30 to 140 days) were used to study trophoblast invasion in the baboon. Application of immunohistochemical staining for cytokeratin allowed proper identification of trophoblast. Earlier reports showing restricted trophoblast invasion in this species were confirmed by the finding that endovascular trophoblast was present in only one third of biopsies containing spiral arteries. Moreover, immunostaining for cytokeratin revealed that in several arteries only a few isolated trophoblastic cells were present, while the vessel had not undergone the normal physiological change. Trophoblast invasion could only be detected within decidual, but not in myometrial, segments of spiral arteries. Interstitial trophoblast invasion was very limited and multinuclear giant cells were absent. Immunohistochemical staining suggested a contribution of laminin to the fibrinoid deposition within the physiologically changed spiral arteries, while fibronectin was present intracellularly in the invaded trophoblast. Because of differences in the trophoblast invasion pattern, the baboon cannot be regarded as a satisfactory experimental model to explore results of inadequate endovascular trophoblast invasion which, in the human, leads to pregnancy complications such a preeclampsia.

Changes in endovascular trophoblast invasion and spiral artery remodelling at term in a transgenic preeclamptic rat model

As a follow-up to our previous study which revealed a surprisingly deeper endovascular trophoblast (ET) invasion on day 18 in a transgenic preeclamptic (PE) rat model (hAngiotensinogen female symbol x hRenin male symbol) compared to non-PE controls, we examined further changes in ET invasion and associated spiral artery (SA) remodelling at term (day 21). PE transgenic rats and non-PE reversely mated (RM) transgenic rats were compared to normal SD rats (C). Sections were stained to visualize trophoblast, fibrinoid, vascular smooth muscle (VSM) and endothelium. SA were evaluated in three depth levels in the mesometrial triangle (MT) using the KS-400 image analysis system. In separate transgenic rats, Doppler ultrasound was performed in uterine arteries, and the resistance indices (RI) were calculated. Although for the whole MT differences in ET invasion were no longer significant between the PE and C, indicating a partial catching up in C rats, there was still significantly more ET in the deepest level in the PE group as compared to the C and RM groups. At the same time the SA walls in PE rats contained significantly more fibrinoid (versus RM and C) and VSM (versus C). In all SA cross-sections, re-endothelialisation was prominent, but significantly different between PE and C group. The Doppler results showed a significantly lower RI in the arcuate uterine artery of the PE group compared to the C group. There was no evidence of elimination of deeply invaded ET at term, previously considered as a possible mechanism for restriction of vascular remodelling in human PE. The differences in vascular remodelling, previously described on day 18 by histology and Doppler data, were maintained on day 21, but there was extensive endothelial repair in the three groups. Atherosis-like lesions were observed in the three groups, most frequently in the RM group, but were never associated with placental infarcts.

Deep trophoblast invasion and spiral artery remodelling in the placental bed of the chimpanzee

Deep trophoblast invasion is usually considered to be a unique feature of human placentation as compared to other primates. Because of the occasional occurrence of preeclampsia in great apes, which in the human is associated with impaired deep invasion, this uniqueness may be questioned. The availability of two well-documented pregnant chimpanzee uteri in the Hubrecht Collection (Museum für Naturkunde, Berlin) allowed us to evaluate the extent of trophoblast invasion in this species. By adjusting currently used protocols, we obtained successful immunohistochemical staining for cytokeratin and α-actin, as well as Ulex europaeus agglutinin 1 (UEA1) lectin staining, in this archival material. In both specimens interstitial trophoblast invasion had occurred in both decidua and myometrium. Because of a lack of published data on fetal growth for this species, fetal sizes (7cm and 13cm) could not be strictly related to gestational ages and thus be compared with the time-course of human trophoblast invasion. However, since the earlier specimen did not show any endovascular trophoblast invasion in spiral arteries - in contrast to pregnant human uteri with equivalent fetal sizes - endovascular migration seems to begin at a different gestational age in the chimpanzee. In the later specimen endovascular trophoblast was associated with spiral artery remodelling in the inner myometrium, and this invasion was extended to include a radial artery, which at that stage still showed relatively intact vascular smooth muscle and elastic lamina. We conclude that invasion depth and spiral artery remodelling are basically similar in chimpanzees and humans, although the seemingly different time of onset may have implications for uteroplacental oxygen supply and fetal development.