Search

Uterine natural killer cells are important for uteroplacental development and pregnancy maintenance. Their role in pregnancy disorders, such as preeclampsia, is unknown. We reduced the number of natural killer cells by administering rabbit anti-asialo GM1 antiserum in an established rat preeclamptic model (female human angiotensinogen×male human renin) and evaluated the effects at the end of pregnancy (day 21), compared with preeclamptic control rats receiving normal rabbit serum. In 100% of the antiserum-treated, preeclamptic rats (7/7), we observed highly degenerated vessel cross sections in the mesometrial triangle at the end of pregnancy. This maternal uterine vasculopathy was characterized by a total absence of nucleated/living cells in the vessel wall and perivascularly and prominent presence of fibrosis. Furthermore, there were no endovascular trophoblast cells within the vessel lumen. In the control, normal rabbit serum-treated, preeclamptic rats, only 20% (1/5) of the animals displayed such vasculopathy. We confirmed the results in healthy pregnant wild-type rats: after anti-asialo GM1 treatment, 67% of maternal rats displayed vasculopathy at the end of pregnancy compared with 0% in rabbit serum-treated control rats. This vasculopathy was associated with a significantly lower fetal weight in wild-type rats and deterioration of fetal brain/liver weight ratio in preeclamptic rats. Anti-asialo GM1 application had no influence on maternal hypertension and albuminuria during pregnancy. Our results show a new role of natural killer cells during hypertensive pregnancy in maintaining vascular integrity. In normotensive pregnancy, this integrity seems important for fetal growth., (© 2016 American Heart Association, Inc.)

Pregnant women who subsequently develop preeclampsia are highly sensitive to infused angiotensin (Ang) II; the sensitivity persists postpartum. Activating autoantibodies against the Ang II type 1 (AT(1)) receptor are present in preeclampsia. In vitro and in vivo data suggest that they could be involved in the disease process. We generated and purified activating antibodies against the AT(1) receptor (AT(1)-AB) by immunizing rabbits against the AFHYESQ epitope of the second extracellular loop, which is the binding epitope of endogenous activating autoantibodies against AT(1) from patients with preeclampsia. We then purified AT(1)-AB using affinity chromatography with the AFHYESQ peptide. We were able to detect AT(1)-AB both by ELISA and a functional bioassay. We then passively transferred AT(1)-AB into pregnant rats, alone or combined with Ang II. AT(1)-AB activated protein kinase C-α and extracellular-related kinase 1/2. Passive transfer of AT(1)-AB alone or Ang II (435 ng/kg per minute) infused alone did not induce a preeclampsia-like syndrome in pregnant rats. However, the combination (AT(1)-AB plus Ang II) induced hypertension, proteinuria, intrauterine growth retardation, and arteriolosclerosis in the uteroplacental unit. We next performed gene-array profiling of the uteroplacental unit and found that hypoxia-inducible factor 1α was upregulated by Ang II plus AT(1)-AB, which we then confirmed by Western blotting in villous explants. Furthermore, endothelin 1 was upregulated in endothelial cells by Ang II plus AT(1)-AB. We show that AT(1)-AB induces Ang II sensitivity. Our mechanistic study supports the existence of an "autoimmune-activating receptor" that could contribute to Ang II sensitivity and possible to preeclampsia.

Preeclampsia is a common and potentially lethal pregnancy complication for women and offspring. Women who develop preeclampsia also run a long-term augmented risk of cardiovascular disease and premature death, and two theories are discussed. Women developing preeclampsia and persons developing cardiovascular disease may have common risk factors, which are unmasked by the "stress" of pregnancy. Alternatively, a new risk factor might occur de novo during the preeclamptic pregnancy. In preeclampsia, lipid deposition in walls of the maternal uterine arteries leading to the placenta, named spiral arteries, regularly occurs. These vascular lesions resemble early stages of atherosclerosis and are named "acute atherosis" and is thought to regress after delivery. The mechanisms that contribute to acute atherosis in preeclampsia are largely unknown, but are related to the impaired vascular remodeling of the spiral arteries in the first half of pregnancy. One striking feature is that the development of these "atherosclerosis-like" lesions requires a few months in pregnancy and may be partly linked to invasion of trophoblasts (specialized fetally derived placenta cells). We summarize normal and pathological vessel remodeling in pregnancy and discuss similarities and differences between preeclampsia and arteriosclerosis. The transient appearance of acute atherosis of uterine wall spiral arteries seen in pregnancy complications and the molecular interaction between trophoblast, smooth muscle and vascular cells could add important elements to explain arteriosclerosis and stenosis in cardiovascular disease. Further understanding of the process underlying spiral artery atherosis in the months of pregnancy may cast light on development of cardiovascular disease later in life.

The renin-angiotensin (Ang) system is important during placental development. Dysregulation of the renin-Ang system is important in preeclampsia (PE). Female rats transgenic for the human angiotensinogen gene crossed with males transgenic for the human renin gene develop the PE syndrome, whereas those of the opposite cross do not. We used this model to study the role of Ang II in trophoblast invasion, which is shallow in human PE but deeper in this model. We investigated the following groups: PE rats, opposite-cross rats, Ang II-infused rats (1000 ng/kg per day), and control rats. Ang II infusion increased only circulating Ang II levels (267.82 pg/mL), opposite cross influenced only uteroplacental Ang II (13.52 fmol/mg of protein), and PE increased both circulating (251.09 pg/mL) and uteroplacental (19.24 fmol/mg of protein) Ang II. Blood pressure and albuminuria occurred in the models with high circulating Ang II but not in the other models. Trophoblast invasion increased in PE and opposite-cross rats but not in Ang II-infused rats. Correspondingly, uterine artery resistance index increased in Ang II-infused rats but decreased in PE rats. We then studied human trophoblasts and villous explants from first-trimester pregnancies with time-lapse microscopy. Local Ang II dose-dependently increased migration by 75%, invasion by 58%, and motility by 282%. The data suggest that local tissue Ang II stimulates trophoblast invasion in vivo in the rat and in vitro in human cells, a hitherto fore unrecognized function. Conceivably, upregulation of tissue Ang II in the maternal part of the placenta represents an important growth factor for trophoblast invasion and migration.

Rats harboring the human angiotensinogen and human renin genes develop preeclamptic features in pregnancy. The preeclamptic rats exhibit a deeper trophoblast invasion associated with a reduced resistance index by uterine Doppler. Doxycycline inhibits matrix metalloproteinase activity. We tested the hypothesis that matrix metalloproteinase inhibition reduces trophoblast invasion with subsequent changes in placental perfusion. Preeclamptic and pregnant control Sprague-Dawley rats were treated with doxycycline (30 mg/kg of body weight orally) from gestational day 12 until day 18. Placental perfusion was assessed using a micromarker contrast agent. The animals were euthanized on day 18 of pregnancy; biometric data were acquired, and trophoblast invasion was analyzed. Doxycycline resulted in intrauterine growth retardation and lighter placentas in both groups. Maternal body weight was not affected. As shown earlier, preeclamptic rats exhibited a deeper endovascular trophoblast invasion. However, doxycycline treatment reduced trophoblast invasion in the preeclamptic rats. The physiological spiral artery remodeling, as assessed by the deposition of fibrinoid and alpha-actin in the spiral artery contour, was significantly reduced by doxycycline. The vascularity index, as assessed by perfusion measurement of the placenta, was reduced after doxycycline treatment in preeclamptic rats. Thus, matrix metalloproteinase inhibition with doxycycline leads to reduced trophoblast invasion and associated reduced placental perfusion. These studies are the first to show that reducing trophoblast-induced vascular remodeling decreases subsequent placental perfusion. Our model allows the study of dysregulated trophoblast invasion and vascular remodeling in vivo to gain important insights into preeclampsia-related mechanisms.

We investigated intrauterine growth restriction, endothelial function, and uterine artery blood flow characteristics in a transgenic preeclampsia rat model with an activated renin-angiotensin system. We compared preeclamptic Sprague-Dawley (SD-PE) rats with normal pregnant Sprague-Dawley and nonpregnant Sprague-Dawley rats. We used transabdominal ultrasound and found that SD-PE rat embryos developed intrauterine growth restriction. Isolated uterine arteries from SD-PE rats incubated with phenylephrine exhibited an increased contractile response, whereas a single high dose of acetylcholine resulted in an impaired vasorelaxation compared with controls. Incremental acetylcholine doses increased relaxation of SD-PE vessels at low acetylcholine doses but caused a paradoxical contraction at higher acetylcholine doses. Indomethacin and a thromboxane-receptor antagonist (SQ 29,548) blocked this effect, suggesting maternal prostanoid-dependent endothelial dysfunction. SD-PE rats had a decreased prostacyclin (6-keto-prostaglandin F1alpha):thromboxane ratio in the serum compared with normal pregnant Sprague-Dawley rats or nonpregnant Sprague-Dawley. Surprisingly, the Doppler resistance index decreased during pregnancy in SD-PE compared with normal pregnant Sprague-Dawley rats, suggesting unimpaired uteroplacental flow in the uterine artery. Umbilical flow was unchanged with absent end-diastolic flow in all of the groups. Renin-angiotensin system activation-induced preeclampsia is associated with altered placentation, modified resistance index, and endothelial dysfunction. A disturbed prostacyclin:thromboxane ratio could be an important mediator.

Maternal spiral artery remodeling is the consequence of controlled trophoblast invasive interaction with the maternal cellular environment and is fundamentally important for successful placentation. In preeclampsia, trophoblast invasion is shallow, remodeling is incomplete, and vessels develop an inflammatory appearance, termed "acute atherosis." We noted that, in our preeclampsia, human renin-human angiotensinogen transgenic rat model, complement component 3 (C3), and tumor necrosis factor-alpha were upregulated and heavily expressed in atherotic uteroplacental vessels. We next used coculture involving human trophoblasts, rat vascular smooth muscle cells (VSMCs), and human VSMCs to observe VSMC-trophoblast regulatory interactions. Tumor necrosis factor-alpha induced complement C3 and interleukin-6 expression in VSMCs. We found that trophoblasts were able to reduce VSMC C3 and interleukin-6 expression after the VSMCs were stimulated with tumor necrosis factor-alpha. However, a direct VSMC-trophoblast cell-cell contact was necessary for this anti-inflammatory response. We also studied double-transgenic VSMCs that express inflammatory components and exhibit accelerated proliferation ("synthetic" phenotype). Trophoblasts could not downregulate C3 in these cells. We then examined uteroplacental tissues from preeclamptic and control patients. In control deciduas, only traces of C3 staining were observed, and vessels were thin walled without thrombus formation. In preeclampsia, the decidual vessels showed atherosis, thrombus formation, and C3 expression. Our data suggest that fetally derived trophoblasts require direct cell-cell contact with maternally derived VSMCs to downregulate VSMC C3 and interleukin-6 expression and to avoid atherosis. The findings also implicate C3 in the placental vasculopathy observed in 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 x 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 x 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.