Preeclampsia is associated with reduced serum levels of placenta growth factor

Genetic Deletion of Placenta Growth Factor in Mice Alters Uterine NK Cells

Placenta growth factor (PlGF; formerly PGF), a vascular endothelial growth factor gene family member, is expressed in human implantation sites by maternal uterine NK (uNK) and fetal trophoblast cells. Lower than normal concentrations of blood and urinary PlGF have been associated with impending onset of pre-eclampsia, a hypertensive disease of late human gestation characterized by limited intravascular trophoblast invasion. In pregnant rodents, delivery of the PlGF antagonist sFlt-1 or S-endoglin induces pre-eclampsia-like lesions. Mice genetically deleted in PlGF reproduce, but neither their implantation sites nor their uNK cell development are described. We combined real-time PCR of endometrium from nonpregnant and gestation day (gd)6-18 C57BL6/J (B6) mice with immunohistology to analyze PlGF expression in normal mouse pregnancy. To estimate the significance of uNK cell-derived PlGF, PlGF message was quantified in mesometrial decidua from pregnant alymphoid Rag2 null/common gamma chain null mice and in laser capture-microdissected B6 uNK cells. Histopathologic consequences from PlGF deletion were also characterized in the implantation sites from PlGF null mice. In B6, decidual PlGF expression rose between gd8-16. uNK cells were among several types of cells transcribing PlGF in decidualized endometrium. Immature uNK cells, defined by their low numbers of cytoplasmic granules, were the uNK cells displaying the greatest number of transcripts. PlGF deletion promoted the early differentiation high numbers of binucleate uNK cells (gd8) but had no other significant, morphometrically detectable impact on implantation sites. Thus, in mice, PlGF plays an important role in successful uNK cell proliferation and/or differentiation.

Changes in circulating level of angiogenic factors from the first to second trimester as predictors of preeclampsia

OBJECTIVE

This study was undertaken to assess changes in placenta growth factor and soluble fms-like tyrosine kinase-1 as predictors of preeclampsia.

STUDY DESIGN

Nested case-control study of 154 preeclampsia cases delivered preterm and 190 delivered at term, and 392 controls.

RESULTS

Comparing the lowest and highest quartile of placenta growth factor increase from first to second trimester, the odds for preterm preeclampsia was 13.8 (95% CI, 4.4-43.2) higher for women with the lowest increase. Compared with controls, women with preterm preeclampsia had lower soluble fms-like tyrosine kinase-1 in the first, but higher in second trimester. Comparing highest and lowest quartile of increase, the odds for preterm preeclampsia was 9.2 (95% CI 3.4-25.0) higher for women with highest increase. Low placenta growth factor and high soluble fms-like tyrosine kinase-1 increase combined yielded extremely high relative risk of preterm preeclampsia (odds ratio, 35.3, 95% CI, 7.6-164.2), compared with the combination of high (placenta growth factor) and low (soluble fms-like tyrosine kinase-1) increase.

CONCLUSION

Low placenta growth factor and high soluble fms-like tyrosine kinase-1 increase from first to second trimester are strong predictors of preeclampsia.

Analysis of the gene regulatory program induced by the homeobox transcription factor distal-less 3 in mouse placenta

Dlx3, a homeodomain transcription factor, is essential for placental development in the mouse. The Dlx3(-/-) mouse embryo dies at embryonic d 9.5-10 putatively due to placental failure. To develop a more comprehensive understanding of the gene profile regulated by Dlx3, microarray analysis was used to determine differences in gene expression within the placenta of Dlx3(+/+) and Dlx3(-/-) mice. Array analysis revealed differential expression of 401 genes, 33 genes in which signal to log ratio values of null/wild-type were lower than -0.5 or higher than 0.5. To corroborate these findings, quantitative real-time PCR was used to confirm differential expression for 11 genes, nine of which displayed reduced expression and two with enhanced expression in the Dlx3(-/-) mouse. Loss of Dlx3 resulted in a marked reduction (>60%) in mRNA expression of placental growth factor (Pgf), a member of the vascular endothelial growth factor family. Consistent with these results, Pgf secretion from placental explants tended to be reduced in the Dlx3(-/-) mice, compared with wild type. To investigate mechanisms of Dlx3 regulation of Pgf gene transcription, we cloned 5.2 kb of the Pgf 5' flanking sequence for use in reporter gene assays. Expression of the Pgf promoter luciferase reporter containing at least three Dlx3 binding sites was increased markedly by overexpression of Dlx3 supporting the conclusion that Dlx3 may have a direct effect on Pgf promoter activity. These studies provide a novel view of the transcriptome regulated by Dlx3 in mouse placenta. Dlx3 is specifically required for full expression and secretion of Pgf in vivo. Moreover, in vitro studies support the conclusion that Dlx3 is sufficient to directly modulate expression of the Pgf gene promoter in placental cells.

Angiogenic growth factors in maternal and fetal serum in pregnancies complicated by intrauterine growth restriction

The present study was performed to compare serum concentrations of maternal and fetal angiogenic growth factors in IUGR (intrauterine growth restriction) and normal pregnancy at the time of delivery. VEGF (vascular endothelial growth factor), PlGF (placental growth factor), sFlt-1 (soluble fms-like tyrosine kinase 1), sKDR (soluble kinase domain receptor) and bFGF (basic fibroblast growth factor) were measured by ELISA in serum from a maternal peripheral vein, the umbilical vein and the umbilical arteries in 15 women with pregnancies complicated by IUGR and 16 controls (women with normal pregnancies). In IUGR, sFlt-1 was increased, and PlGF and sKDR were decreased, in both maternal serum and serum from the umbilical vein. Additionally, bFGF was increased in serum from the umbilical vein of women with pregnancies complicated by IUGR. No significant differences in growth factor concentrations between the groups were found in serum from the umbilical artery. In both groups, levels of VEGF were higher and levels of sFlt-1 were lower in serum from the umbilical vein and umbilical artery compared with maternal serum. PlGF levels were found to be lower in serum from the umbilical vein compared with maternal serum in both groups, whereas PlGF levels in serum from the umbilical artery were significantly lower only in the control group. These findings suggest an imbalance of angiogenic and anti-angiogenic factors in IUGR, with formation of an anti-angiogenic state in maternal and, to a lesser extent, umbilical vein blood. The placenta appears to play a central role in the release of sFlt-1 into maternal and umbilical blood. Umbilical artery blood was unaffected in IUGR, indicating that the fetus does not contribute to changes in angiogenic growth factor concentrations.

Low urinary placental growth factor is a marker of pre-eclampsia

Recent reports of increased serum levels of soluble fms-like tyrosine kinase 1 (sFlt-1) and decreased levels of placental growth factor (PlGF) suggest the key role of angiogenic factors in development of pre-eclampsia. PlGF is excreted in urine, and reduced urinary level has been suggested as a marker of this condition as well as help in its prediction. We measured urinary PlGF and creatinine values in 69 pregnant women (35 with pre-eclampsia and 34 normotensive controls). Over 70% patients had severe pre-eclampsia. Compared to controls, the urinary PlGF and PlGF/creatinine levels were significantly reduced in women with pre-eclampsia. The hospital stay was longer and fetal outcomes poorer in this group. Three normotensive women who showed very low levels developed pre-eclampsia 2-6 weeks later. Reduced urinary PlGF level in a pregnant woman is a marker of pre-eclampsia. The value of reduced urinary PlGF levels in predicting pre-eclampsia in currently normotensive pregnant women needs to be evaluated. A simple predictive test is likely to be of value in the developing countries.

First Trimester Markers for Pre-Eclampsia: Placental vs. Non-Placental Protein Serum Levels

BACKGROUND/AIM

Parallel investigation, in a matched case-control study, of the association of different first-trimester markers with the risk of subsequent pre-eclampsia (PE).

METHOD

The levels of different first trimester serum markers and fetal nuchal translucency thickness were compared between 52 cases of PE and 104 control women by non-parametric two-group comparisons and by calculating matched odds ratios.

RESULTS

In univariable analysis increased concentrations of inhibin A and activin A were associated with subsequent PE (p < 0.02). Multivariable conditional logistic regression models revealed an association between increased risk of PE and increased inhibin A and translucency thickness and respectively reduced pregnancy-associated plasma protein A (PAPP-A) and placental lactogen . However, these associations varied with the gestational age at sample collection. For blood samples taken in pregnancy weeks 12 and 13 only, increased levels of activin A, inhibin A and nuchal translucency thickness, and lower levels of placenta growth factor and PAPP-A were associated with an increased risk of PE.

CONCLUSIONS

Members of the inhibin family and to some extent PAPP-A and placental growth factor are superior to other serum markers, and the predictive value of these depends on the gestational age at blood sampling. The availability of a single, early pregnancy 'miracle' serum marker for PE risk assessment seems unlikely in the near future.

Evaluation of placenta growth factor and soluble Fms-like tyrosine kinase 1 receptor levels in mild and severe preeclampsia

OBJECTIVE

The purpose of this study was to determine if maternal serum concentrations of placenta growth factor (PlGF) and soluble Fms-like tyrosine kinase 1 receptor (s-Flt1) are more abnormal in patients with severe preeclampsia compared with mild preeclampsia.

STUDY DESIGN

Serum samples were collected from 32 control patients and 80 patients with mild or severe preeclampsia. PlGF and s-Flt1 concentrations were quantitated by enzyme-linked immunosorbent assay (ELISA). Results are expressed as median (Q1-Q3) unless stated otherwise. After normalization, serum markers were compared using one-way analysis of covariance (ANCOVA).

RESULTS

Patients with preeclampsia had decreased levels of PlGF (75.1 +/- 14 vs 391 +/- 54 pg/mL, P < .0001) and elevated s-Flt1 concentration (1081 +/- 108 vs 100.1 +/- 26.9 pg/mL, P < .0001) compared with the respective controls (mean +/- SEM). PlGF concentration was lower in patients with mild preeclampsia compared with severe, respectively (67 pg/mL [39-158] vs 24 pg/mL [4-57], P < .02). s-Flt1 was not different between mild and severe preeclampsia (674 pg/mL [211-1297] vs 1015 pg/mL [731-1948], P = .08).

CONCLUSION

PlGF and s-Flt1 serum levels are abnormal in patients with preeclampsia compared with controls, but only PlGF is more abnormal in severe preeclampsia compared with mild preeclampsia.

Pre-eclampsia and Fetal Growth Restriction: How Morphometrically Different is the Placenta?

Both pre-eclampsia (PET) and fetal growth restriction (FGR) pose a heavy burden on fetal and maternal health and may disrupt pregnancy outcome. Using design based stereological techniques, placental vascular and villous morphology were assessed to determine the individual role played by both PET and FGR on placental growth during the third trimester. The following placentas delivered between 25 and 41 weeks of gestation were included into the study; controls (n=16), PET (n=20), FGR (n=17) and PET-FGR (n=16). Each placenta was uniformly randomly sampled and the sampled tissue processed to paraffin. Sections were stained with a CD34 antibody and the following morphometric parameters estimated: volumes, surface areas, length, diameters and the shape factor of the villous (terminal and intermediate) and vascular placental features. For stereologically estimated parameters pure PET had an effect on IVS and terminal villi volume only. FGR alone or when coexisting with PET contributed towards significant reductions in volumetric and surface area terminal villous and vascular features. FGR factors also contributed towards a significant reduction in the lengths of all parameters estimated and in the terminal villi diameter. Additionally, FGR was associated with a significant difference in shape factor indices for both intermediate and terminal villi. This study has shown that PET on its own has limited influence on the placental morphology studied, since the vascular features estimated do not differ stereologically from age matched normal controls. However, placental morphology is different between PET and PET-FGR and between PET-FGR and FGR. PET and FGR may have a cumulative effect on placental villous and vascular morphology as seen in the PET-FGR but there is no synergistic effect. These morphological abnormalities may have major physiological implications in terms of placental function and fetal growth.

Correlations of placental perfusion and PlGF protein expression in early human pregnancy

OBJECTIVE

The purpose of this study was to investigate temporal correlations between maternal serum placenta growth factor levels and placental perfusion in early human pregnancies.

STUDY DESIGN

Systolic umbilical artery Doppler blood flow velocity indices at fetal and placental insertion sites were measured between 7 and 22 weeks of gestation from normal singleton pregnancies. Maternal serum placenta growth factor levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Maternal serum placenta growth factor levels showed an exponential increase at approximately 14 weeks of gestation. Placenta perfusion, as estimated by systolic Doppler blood flow indices, significantly increased with gestational age (P < .0001). There was a close association between placenta growth factor expression levels and evidence of increased placenta perfusion (P < .033).

CONCLUSION

The significant increase in serum placenta growth factor coincides with the increased perfusion of the maternal/fetal interface at approximately 12 to 14 weeks of gestation. Correlation of placenta growth factor expression and placental perfusion suggests that placenta growth factor may contribute to assuring adequate vascular development/function of the placenta early in gestation.

Vascular endothelial growth factor and placenta growth factor in intrauterine growth-restricted fetuses and neonates

The angiogenic factors vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) are respectively up- and downregulated by hypoxia. We aimed to study circulating levels of the above factors in intrauterine growth restriction (IUGR) and to correlate their levels with the customized centiles of the infants. The study included 25 IUGR and 25 appropriate for gestational age (AGA) full-term, singleton infants and their mothers. Maternal (MS), fetal (UC), and neonatal day 1 (N1) and 4 (N4) blood was examined. MS and N1 PlGF, as well as UC VEGF levels correlated with the customized centiles of the infants (r = 0.39, P = .007, r = 0.34, P = .01, and r = −0.41, P = .004, resp). Furthermore, UC, N1, and N4 VEGF levels were higher in girls (r = 0.36, P = .01, r = 0.33, P = .02, and r = 0.41, P = .005 resp). In conclusion, positive and negative correlations of examined factors with the customized centiles of the infant could rely on placental function and intrauterine oxygen concentrations—both being usually lower in IUGR cases—while higher VEGF levels in girls should possibly be attributed to the stimulating action of estrogens.

Establishing reference values for both total soluble Fms-like tyrosine kinase 1 and free placental growth factor in pregnant women

It has been reported that the concentration of free placental growth factor (PIGF) is decreased and that of soluble fms-like tyrosine kinase 1 (sFlt-1) is increased before the onset of preeclampsia. However, no study has determined the reference values for sFlt-1 and free PIGF during pregnancy using a commercially available enzyme-linked immunosorbent assay (ELISA) kit. This longitudinal cohort study was undertaken to address this issue. Serum samples were collected from 148 women at 10, 18, 28, and 37 weeks of gestation. Preeclampsia occurred in 6 women: 4 women who delivered at <37 weeks of gestation, and 2 women who delivered at > or =37 weeks. The average and 90% confidence interval (90% CI) of the serum concentration of both sFIt-1 and free PIGF were determined in a total of 433 specimens from 148 subjects with 1 to 4 collections at 7 to 39 weeks of gestation, and were represented as quadric curves. The mean values (90% CI) of sFlt-1 (pg/ml) at 10, 18, 28, and 37 weeks of gestation were 413 (174-981), 296 (125-704), 413 (174-982), and 1,130 (477-2,690), respectively. The mean values (90% CI) of free PIGF (pg/ml) were 36 (14-89), 206 (83-515), 518 (207-1,290), and 354 (142-884), respectively. We also established the reference values for the ratio of sFlt-1/PIGF. These values may be useful for predicting the subsequent occurrence of preeclampsia.

Analysis of placental growth factor in placentas of normal pregnant women and women with hypertensive disorders of pregnancy

To investigate the expressions of placental growth factor (PLGF) in placenta with hypertensive disorders of pregnancy (HDP), 45 women with HDP and 20 normally pregnant women were studied. Among 45 women with HDP, there were 23 cases of severe preeclampsia and one case of eclampsia. The location and level of PLGF proteins was determined by immunohistochemistry and Western blot. The expression of PLGF mRNA in placenta was assessed by reverse transcriptional-polymerase chain reaction (RT-PCR). The results showed that: (1) The distribution of PLGF in placenta with HDP was similar to normal one, which was mainly in the cytoplasm of villous syncytiotrophoblast and villous stroma; (2) The expression of PLGF protein was significantly decreased in placentas with mild and severe preeclampsia compared to the normal ones (0.3 +/- 0.4 vs 0.6 +/- 0.4, 0.2 +/- 0.5 vs 0.6 +/- 0.4, P < 0.01). There were no differences between the gestational hypertension placenta and normal one (0.5 +/- 0.6 vs 0.6 +/- 0.4, P > 0.05); (3) The transcription levels of the PLGF mRNA in placentas with preeclampsia were significantly lower than in normal groups (3.33 +/- 0.39 vs 4.87 +/- 0.60, 1.97 +/- 0.29 vs 4.87 +/- 0.60, P < 0.01), and no differences were found between the gestational hypertension placenta and normal groups. These findings suggest that the abnormal expression of PLGF in placentas is related to the pathogenesis of HDP.

Circulating concentrations of sFlt1 (soluble fms-like tyrosine kinase 1) in fetal and maternal serum during pre-eclampsia

OBJECTIVE

We hypothesized that umbilical vein serum soluble fms-like tyrosine kinase 1 (sFlt1) concentration was augmented in pre-eclampsia. We also explored a possible association between fetal and maternal concentrations of sFlt1.

STUDY DESIGN

At cesarean delivery, maternal serum samples from pre-eclamptic (n=38) and uncomplicated (n=32) pregnancies were obtained, as well as umbilical vein serum and amniotic fluid samples. ELISA for human sFlt1, vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) were performed.

RESULTS

Median sFlt1 concentrations were elevated in pre-eclampsia compared to uncomplicated pregnancy, in umbilical venous serum (246 and 163 pg/mL, P=0.04), in maternal serum (9932 and 3417 pg/mL, P<0.001), as well as in amniotic fluid (51,040 and 33,490 pg/mL, P=0.03). A positive association between the fetal and maternal serum levels of sFlt1 was found in the pre-eclampsia group. Median PlGF concentration in the maternal serum was significantly lower in the pre-eclampsia group compared to the control group (82 pg/mL and 169 pg/mL, P<0.001).

CONCLUSIONS

sFlt1 concentration is elevated in the fetal circulation in pre-eclampsia, but at a much lower level than in the maternal circulation. The results of our study do not support a substantial fetal contribution to the elevated circulating maternal sFlt1 protein concentration in pre-eclampsia.

Circulating Angiogenic Factors in the Pathogenesis and Prediction of Preeclampsia

Preeclampsia is a major cause of maternal, fetal, and neonatal mortality worldwide. Although the etiology of preeclampsia is still unclear, recent studies suggest that its major phenotypes, high blood pressure and proteinuria, are due in part to excess circulating soluble fms-like tyrosine kinase-1 concentrations. Soluble fms-like tyrosine kinase-1 is an endogenous antiangiogenic protein that is made by the placenta and acts by neutralizing the proangiogenic proteins vascular endothelial growth factor and placental growth factor. High serum soluble fms-like tyrosine kinase-1 and low serum free placental growth factor and free vascular endothelial growth factor have been observed in preeclampsia. Abnormalities in these circulating angiogenic proteins are not only present during clinical preeclampsia but also antedate clinical symptoms by several weeks. Therefore, this raises the possibility of measuring circulating angiogenic proteins in the blood and the urine as a diagnostic and screening tool for preeclampsia. The availability of a test to predict preeclampsia would be a powerful tool in preventing preeclampsia-induced mortality, especially in developing nations, where high-risk specialists are limited. This review will summarize our current understanding of the role of circulating angiogenic proteins in the pathogenesis and clinical diagnosis/prediction of preeclampsia.

Human trophoblast function during the implantation process

The implantation process involves complex and synchronized molecular and cellular events between the uterus and the implanting embryo. These events are regulated by paracrine and autocrine factors. Trophoblast invasion and migration through the uterine wall is mediated by molecular and cellular interactions, controlled by the trophoblast and the maternal microenvironment. This review is focused on the molecular constituents of the human trophoblast, their actions and interactions, including interrelations with the uterine endometrium.

Serum Levels of Macrophage Colony Stimulating, Vascular Endothelial, and Placenta Growth Factor in Relation to Later Clinical Onset of Pre-Eclampsia and a Small-for-Gestational Age Birth

PROBLEM

The multisystem disorder of pre-eclampsia (PE) becomes manifest in late gestation, but the pathology originates in early pregnancy by the deleterious action of placental substances to the maternal endothelial system. These factors were searched for in the attempt to identify, as early as possible, the pregnancies with an increased risk of developing pre-eclampsia. The literature is equivocal regarding the usefulness of various markers including vascular endothelial growth factor (VEGF) and macrophage colony-stimulating factor (M-CSF). Results are often confounded by a varying fraction of pregnancies affected by foetal growth restriction (FGR) amongst the case and control groups.

METHOD OF STUDY

In a nested case-control study we compared the serum levels of M-CSF, VEGF, and placenta growth factor (PLGF) in 23 pregnancies with subsequent mild PE without FGR and nine FGR pregnancies without PE with 40 matched controls at 17, 25, and 33 weeks of gestation cross-sectionally and longitudinally.

RESULTS

VEGF levels were reduced in FGR but not in subsequently pre-eclamptic pregnancies at 17, 25, and 33 weeks. In contrast, PLGF was reduced in the PE but not in the FGR group. M-CSF did not differ between the three groups.

CONCLUSION

Depending on which growth factor is found to be reduced, an early distinction can be made in terms of an increased risk for PE or FGR. Inconsistencies in the literature may reflect differences in PE disease severity between studies and the presence of a varying fraction of cases with FGR.

Soluble fms-like tyrosine kinase 1 is increased in preeclampsia but not in normotensive pregnancies with small-for-gestational-age neonates: relationship to circulating placental growth factor

CONTEXT

An excess of the soluble receptor, fms-like tyrosine kinase 1 (sFlt-1) may contribute to maternal vascular dysfunction in women with preeclampsia by binding and thereby reducing concentrations of free vascular endothelial growth factor and placental growth factor (PlGF) in the circulation. The putative stimulus for increased sFlt-1 during preeclampsia, placental hypoxia due to poor perfusion, is common to both preeclampsia and idiopathic intrauterine growth restriction. However, the latter condition occurs without maternal vascular disease.

OBJECTIVE

We asked whether, as with preeclampsia, sFlt-1 is increased and free PlGF is decreased in villous placenta and maternal serum of normotensive women with small-for-gestational-age (SGA) neonates.

STUDY DESIGN

This was a case-control study using banked samples. Groups of women with SGA neonates (birth weight centile < 10th) and women with preeclampsia were matched to separate sets of normal pregnancy controls based on gestational age at blood sampling (serum) or gestational age at delivery (placenta).

RESULTS

sFlt-1 levels were higher in preeclamptics than controls (serum, P < 0.0001; placental protein, P = 0.03; placental mRNA, P = 0.007) but not increased in SGA pregnancies. PlGF was lower in both preeclampsia (serum, P < 0.0001; placental protein, P = 0.05) and SGA (serum, P = 0.0008; placental protein, P = 0.03) compared with their controls. PlGF in preeclampsia and SGA groups did not differ.

CONCLUSIONS

These data are consistent with a role for sFlt-1 in the maternal manifestations of preeclampsia. In contrast to preeclampsia, sFlt-1 does not appear to contribute substantially to decreased circulating free PlGF in SGA pregnancies in the absence of a maternal syndrome.

Hypoxia-induced increase in soluble Flt-1 production correlates with enhanced oxidative stress in trophoblast cells from the human placenta

OBJECTIVE

Placental trophoblast cells (TCs) produce soluble Flt-1 (sFlt-1). Hypoxia induces placental oxidative stress and modulates trophoblast function. The aim of this study was to investigate whether hypoxia mediates TC sFlt-1 production and whether increased sFlt-1 production correlates with increased oxidative stress in placental TCs.

METHODS

Placentas were obtained immediately after delivery from normal pregnant women (n = 8). Placental TCs were isolated by Dispase digestion of villous tissue and purified by Percoll gradient centrifugation. Isolated TCs were cultured under normoxia (21% O2: 5% CO2/95% air) and hypoxia (2% O2/5% CO2/93% N2) conditions for 3 days in vitro. TC productions of sFlt-1, VEGF, and PlGF were measured by enzyme-linked immunosorbent assay (ELISA). Lipid peroxide production and superoxide dismutase (CuZn-SOD) levels were evaluated. Messenger RNA expressions of Flt-1, VEGF and PlGF were determined by RT-PCR. Messenger RNA expressions for superoxide dismutase (CuZn-SOD) and heme oxygenase-1 (HO-1) were also determined. Data are expressed as mean +/- SE. A p level less than 0.05 was considered statistically different.

RESULTS

Our results show that sFlt-1 production was significantly increased by TCs cultured under hypoxia condition that correlates with increased lipid peroxide production. We also found that under hypoxia condition: (1) the ratio of PlGF/VEGF production was reversed; (2) the ratio of lipid peroxides to superoxide dismutase production was increased. The increased mRNA expressions for Flt-1 and VEGF and the decreased mRNA expression for PlGF in TCs were consistent with the protein productions under hypoxia condition.

CONCLUSION

We concluded that upregulation of sFlt-1 and unbalanced PlGF/VEGF production associated with increased oxidative stress are consequences of hypoxia in placental TCs. Our results suggest that placental TCs are major sources of sFlt-1 and VEGF levels in the maternal circulation in women with preeclampsia.

Placenta growth factor levels in second-trimester maternal serum in Down syndrome pregnancy and in the prediction of preeclampsia

OBJECTIVES

To determine the levels of placenta growth factor (PlGF) in second-trimester maternal serum samples from pregnancies affected with fetal Down syndrome and from those that developed preeclampsia and to assess the utility of PlGF as a screening tool for these conditions.

METHODS

Residual second-trimester maternal serum samples were retrieved from freezer storage for 39 cases of Down syndrome and 44 pregnancies that later developed preeclampsia. Each case was matched to 5 control samples for gestational age at collection and duration of freezer storage. PlGF levels were measured in each sample by enzyme-linked immunosorbent assay (ELISA).

RESULTS

PlGF levels increased with gestational age between 15 and 20 gestational weeks. After adjusting for gestational-age effects, the median level of PlGF was 1.01 MoM in Down syndrome pregnancy and 0.74 MoM in pregnancies that developed preeclampsia, which were not significantly different from matched controls. The duration between sampling and onset of preeclampsia did not have an effect on the PlGF level.

CONCLUSION

PlGF levels are not significantly altered in second-trimester maternal serum samples from cases of Down syndrome or in pregnancies that develop preeclampsia.

Concentration of cord serum placenta growth factor in normal and diabetic pregnancies

OBJECTIVE

To investigate whether maternal diabetes or diabetes-related complications, such as macrosomia and chronic fetal hypoxia, are associated with altered placenta growth factor (PlGF) levels in cord serum.

DESIGN

Case-control study.

SETTING

Helsinki University Central Hospital, Helsinki, Finland.

POPULATION

Sixty-two normal pregnancies, 67 pregnancies complicated by type 1 diabetes and 28 pregnancies complicated by insulin-treated gestational diabetes.

METHODS

Cord serum PlGF concentration was measured by an enzyme-linked immunosorbent assay. Amniotic fluid erythropoietin concentration was measured by a chemiluminescent immunologic method. Umbilical artery gas variables were analysed with standard blood gas and pH electrodes.

MAIN OUTCOME MEASURE

PlGF concentration in cord serum at birth.

RESULTS

Cord serum PlGF concentration was similar in normal pregnancies [13.4 (1.0) ng/L], in pregnancies complicated by type 1 diabetes [15.1 (1.8) ng/L, P= 0.583 vs controls] and in pregnancies complicated by insulin-treated gestational diabetes [13.6 (0.9) ng/L, P= 0.991 vs controls]. Cord serum PlGF did not correlate with relative birthweight. In diabetic pregnancies, cord serum PlGF correlated negatively with amniotic fluid erythropoietin (r=-0.449, P < 0.0001) and positively with umbilical artery Po(2) (r= 0.333, P= 0.001). There was a trend toward lower cord serum PlGF levels in diabetic pregnancies with pre-eclampsia compared with those without any hypertensive disorders.

CONCLUSIONS

Maternal diabetes per se is not associated with altered PlGF levels in cord serum. The correlation between PlGF and indices of fetal hypoxia in diabetic pregnancies may be related to the role of PlGF in potentiating the angiogenic response to vascular endothelial growth factor in ischaemia.

Prospective analysis of placenta growth factor (PlGF) concentrations in the plasma of women with normal pregnancy and pregnancies complicated by preeclampsia

OBJECTIVE

The aim of this study was to analyze if levels of plasma PlGF in the second half of pregnancy have predictive value for the identification of women destined to develop preeclampsia or another complication of pregnancy.

MATERIAL AND METHODS

A bank of 1.543 randomly collected plasma samples (22-29 weeks of gestation) was established and PlGF concentrations were quantitated in a prospective longitudinal study in all pregnant women who developed a complication of pregnancy in late gestation (177 of 1.543) and the same number of gestational age matched pregnancies with normal outcome.

RESULTS

Plasma PlGF levels in pregnant women rise steadily throughout pregnancy from the level of nonpregnant women (< 50 pg/mL) to levels exceeding 500 pg/mL after 30 weeks of gestation. Just 7.3% of pregnant women with normal outcome of pregnancy had PlGF levels of less than 200 pg/mL beyond 22 weeks of gestation (3.7% beyond 25 weeks of gestation). The rise in plasma PlGF in the second half of pregnancy was significantly attenuated in pregnancies that were complicated by preeclampsia in late gestation. Of all women who developed preeclampsia, 27.3% (12 of 44) had plasma PlGF levels below 200 pg/mL. The attenuation of the rise in plasma PlGF was not evident in other complications of pregnancy (transient hypertension, fetal retardation, pregnancy diabetes, premature contractions, proteinuria without hypertension, infections during pregnancy).

CONCLUSION

The rise in plasma PlGF levels observed in normal pregnancies is significantly attenuated in pregnancies complicated by preeclampsia. Yet, due to the low sensitivity and specificity, plasma PlGF levels in the second half of pregnancy have no predictive value for the identification of individual women destined to develop preeclampsia.

Aspects of human fetoplacental vasculogenesis and angiogenesis. I. Molecular regulation

Patterns of fetoplacental angiogenesis vary during gestation and in association with certain pregnancy pathologies. In a set of three linked reviews, we provide a survey of current knowledge about the molecular regulation, cellular players, qualitative and quantitative morphological features of the vascularization of human placental villi. Here, an account is given of the role played by hypoxia-inducible factor in mediating the effects of oxygen on production of growth factor ligands and receptors which regulate angiogenesis and vessel maturation. However, it should be noted that, for the human placenta early in gestation, the normal (i.e. physiological) partial pressure of O(2)is low but this does not mean that the tissue is hypoxic. Thus, the mechanisms of regulating angiogenic growth factor production may differ at this time in comparison to those found later in gestation or in other tissues or organs. The vasculature in the placenta is plastic and changes markedly as gestation progresses. This is controlled by the complex interplay between physical factors and chemical factors including oxygen, growth factors and growth inhibitors. The companion reviews describe morphological features of normal and pathological development of the human placenta in the context of the factors discussed here.

Aspects of human fetoplacental vasculogenesis and angiogenesis. III. Changes in complicated pregnancies

Patterns of fetoplacental angiogenesis vary not only during the course of a normal pregnancy but also in certain pregnancy pathologies. Here, we review some of the molecular and morphological events which occur in complicated pregnancies. The pregnancy complications are chosen in an attempt to represent the possible different origins (preplacental, uteroplacental, postplacental) of fetal hypoxia. Molecular events focus on reported changes in hypoxia-inducible factors, angiopoietins and the vascular endothelial, basic fibroblast and placenta growth factors and their receptors. Morphological changes focus on patterns of angiogenesis (branching and non-branching) and a consistent set of morphometric descriptors (covering measures of total capillary growth, villous capillarization and capillary size and shape in transverse section). Apart from some uncertainties due to lack of information, or failure to resolve fully the effects of intrauterine growth restriction and pre-eclampsia, alterations in the angiogenic growth factors and morphologies of capillaries and villi in different complicated pregnancies seem to conform reasonably well to those predicted by the fetal hypoxia paradigm. However, it is clear that future studies on the effects of different origins of fetal hypoxia should exercise more care in the choice and interpretation of relevant descriptors and take more account of the parallel effects of possible confounders. In addition, rather than comparing uncomplicated and complicated pregnancies only at term, more information about molecular and morphological events that occur throughout gestation would be extremely valuable. This includes further studies on changes in growth factor receptors, the less-well-documented angiogenic factors (e.g. angiogenin, angiostatin, endostatin) and the associations between endothelial cells and pericytes. A more integrated approach involving also parallel analysis of the effects of erythropoietin and other potential vasoactive factors on the behaviour and morphology of fetal vessels would be beneficial.

Deferential Regulation of Placenta Growth Factor (PlGF)-Mediated Signal Transduction in Human Primary Term Trophoblast and Endothelial Cells

Increasing evidence supports that many common obstetrical complications may involve the disruption of normal placental and/or uterine vascular function. Placenta growth factor (PlGF) is an angiogenic factor that is abundantly expressed in the placenta, with primary site of synthesis being trophoblast. Receptors for PlGF include products of the fms-like tyrosine kinase (flt-1) gene which is expressed in several cell types including endothelial cells and trophoblast. PlGF activation of flt-1 in trophoblast induces the stress activated protein kinase (SAPK) signal transduction pathways, JNK (c-Jun-N-Terminal Kinase) and p38, with little induction of the extracellular signal-regulated protein kinase (ERK)-1/2 pathways. In contrast, PlGF induces strong ERK-1/2 activation, but little JNK or p38 responses in human umbilical vein endothelial cells (HUVEC). To better understand the biochemical functions of PlGF in trophoblast, we studied upstream signal regulatory molecules to determine those that are responsible for directing the divergent PlGF signal transduction responses in these cell types. PlGF induced similar activation of Nck and PLC-gamma in trophoblast and HUVEC. In marked contrast, SHP-2 and Gab2 were strongly activated by PlGF in endothelial cells but not trophoblast. These results suggest a general role for Nck and PLC-gamma in mediating PlGF signal transduction responses independent of the different downstream MAPK pathways activated. However, SHP-2 and Gab2 are regulatory molecules involved in the PlGF induction of different terminal pathways in HUVEC and trophoblast.

Determinants of Placental Vascularity

PROBLEM

Vascular growth during implantation and placentation is critical for successful gestation and it is thought that vascular insufficiencies during placentation contribute to a number of obstetrical complications. However, relatively little is known regarding the regulation of angiogenesis in the placenta.

METHOD OF STUDY

We review literature concerning the potential significance of inadequate placental vascularity as a contributor to the obstetrical complications of spontaneous abortion, fetal growth restriction and preeclampsia. Gene expression assays were used to compare fluctuations of placenta growth factor (PlGF) and PlGF receptor expression in normal and preeclamptic trophoblast in vitro.

RESULTS

Studies have shown that common obstetrical complications manifest altered placental vascularity. Both intrinsic defects (gene knockouts) and extrinsic factors (O(2) tension, cytokines, etc) may be responsible for the defects. Some of these factors have been shown to influence trophoblast vascular endothelial growth factor (VEGF)/PlGF expression suggesting this particular family of angiogenic proteins play an important role in placental angiogenesis.

CONCLUSION

Placental vascularization reflects a complex interaction of regulatory factors. Understanding the regulation of vascular growth in the placenta will provide much needed insight into placenta-related vascular insufficiencies.

Circulating angiogenic factors and the risk of preeclampsia

BACKGROUND

The cause of preeclampsia remains unclear. Limited data suggest that excess circulating soluble fms-like tyrosine kinase 1 (sFlt-1), which binds placental growth factor (PlGF) and vascular endothelial growth factor (VEGF), may have a pathogenic role.

METHODS

We performed a nested case-control study within the Calcium for Preeclampsia Prevention trial, which involved healthy nulliparous women. Each woman with preeclampsia was matched to one normotensive control. A total of 120 pairs of women were randomly chosen. Serum concentrations of angiogenic factors (total sFlt-1, free PlGF, and free VEGF) were measured throughout pregnancy; there were a total of 655 serum specimens. The data were analyzed cross-sectionally within intervals of gestational age and according to the time before the onset of preeclampsia.

RESULTS

During the last two months of pregnancy in the normotensive controls, the level of sFlt-1 increased and the level of PlGF decreased. These changes occurred earlier and were more pronounced in the women in whom preeclampsia later developed. The sFlt-1 level increased beginning approximately five weeks before the onset of preeclampsia. At the onset of clinical disease, the mean serum level in the women with preeclampsia was 4382 pg per milliliter, as compared with 1643 pg per milliliter in controls with fetuses of similar gestational age (P<0.001). The PlGF levels were significantly lower in the women who later had preeclampsia than in the controls beginning at 13 to 16 weeks of gestation (mean, 90 pg per milliliter vs. 142 pg per milliliter, P=0.01), with the greatest difference occurring during the weeks before the onset of preeclampsia, coincident with the increase in the sFlt-1 level. Alterations in the levels of sFlt-1 and free PlGF were greater in women with an earlier onset of preeclampsia and in women in whom preeclampsia was associated with a small-for-gestational-age infant.

CONCLUSIONS

Increased levels of sFlt-1 and reduced levels of PlGF predict the subsequent development of preeclampsia.

Evidence of a novel isoform of placenta growth factor (PlGF-4) expressed in human trophoblast and endothelial cells

Placenta growth factor (PlGF), a homodimeric glycoprotein that is homologous to vascular endothelial growth factor (VEGF), is mitogenic to endothelial cells and protects trophoblast from apoptosis. Alternative splicing of mature mRNA gives rise to three known isoforms of PlGF. PlGF is expressed by human trophoblast during normal pregnancy, however, it is not known which isoforms are produced. We have utilized RT-PCR to characterize PlGF isoform expression in normal human trophoblast and umbilical vein endothelial cells (HUVEC). Our results show that PlGF-1, PlGF-2, and PlGF-3 isoforms are expressed by trophoblast and HUVECs. In addition, both cell types also express a novel variant of PlGF, tentatively termed PlGF-4, which has not been previously reported. PlGF-4 consists of the same sequence of PlGF-3, plus the heparin binding domain previously thought to be present only in PlGF-2. Presence of the heparin binding domain in PlGF-4 suggests that this variant would remain cell membrane-associated and thus could influence trophoblast and endothelial cells in an autocrine manner.

Angiogenesis and vasculogenesis in pregnancy

An adequate nutrient and substrate supply is essential for normal intrauterine development of the fetus. Disturbances in uterine blood supply are associated with higher perinatal morbidity and mortality caused by preterm delivery, pre-eclampsia or intrauterine growth restriction. Adaptation of the uterine vasculature to the rising needs of the fetus occurs through both vasodilation and development of new vessels. Angiogenesis is the process of neovascularization from pre-existing blood vessels in response to hypoxia or substrate demands of tissues. The endometrium, decidua and placenta are sources rich of angiogenic growth factors. In general, the angiogenic process is initiated by growth factors such as bFGF, VEGF, or placental growth factor (PlGF). Through a complex signal transduction machinery mediated by respective receptor-tyrosine kinases, an increase in the permeability of the maternal vessels is achieved to permit growth and invasion of endothelial cells. Their chemotactic migration, formation of a vessel lumen, and functional maturation of new capillaries complete the angiogenic process that involves the expression of specific adhesion receptors and extracellular matrix-degrading proteases. During vasculogenesis, endothelial progenitor cells--angioblasts--form a primitive vascular network. This process occurs mainly during fetal development, although recruitment of angioblasts from bone marrow and peripheral blood in response to ischemic insult have been described in adults. Our recent data indicate a novel function for human chorionic gonadotropin (hCG), a hormonal factor of trophoblastic origin in uterine adaptation to early pregnancy as well as in tumor invasion and underline the importance of hCG as an yet unrecognized angiogenic factor. Although there are striking similarities between, on the one hand, tumor invasion and tumor-induced vascularization and, on the other hand, trophoblast invasion and placental development, our understanding of the different molecular and functional aspects of these two different processes, in particular, the self-limitation of the trophoblastic invasion and vessels formation during gestation might allow the establishment of new therapeutic strategies for the treatment of both tumor and pregnancy related pathology.

Factors regulating trophoblast migration and invasiveness: possible derangements contributing to pre-eclampsia and fetal injury

Impaired trophoblast invasiveness and spiral arterial remodelling, which results in poor placental perfusion during early pregnancy, is believed to cause fetal injury and growth retardation, and also endothelial cell activation/dysfunction in a susceptible mother, leading to clinical manifestations of pre-eclampsia. This article briefly reviews the regulatory roles of certain locally active factors in trophoblast migration and invasiveness. This background is then used to discuss and debate whether derangements or dysfunction of some of these factors can manifest as early serum markers predictive of the disease, as opposed to the intermediate and late stage markers which may reflect manifestations and consequences of the disease. Of particular significance are the observed derangements in uPA/uPAR/PAI system, IGFBP-1, HGF, HB-EGF and TGFbeta, factors which are known to regulate trophoblast migration and invasiveness in situ. An emphasis is placed on the need for longitudinal studies in order to identify predictive serum markers which may help strategies for prevention or amelioration of fetal injury and pre-eclampsia.

Prenatal screening, epidemiology, diagnosis, and management of preeclampsia

The cause of preeclampsia remains unknown. The disease manifests itself across a broad clinical spectrum from mild to severe, conferring vastly different morbidities and suggesting possibly different disease processes. Oxidative stress, endothelial dysfunction, maternal-fetal immune incompatibility, and abnormal placental implantation are among the suggested causes. The need for a marker or set of markers that allow for definitive diagnosis and assessment of future risk of preeclampsia is tremendous. Ultrasound techniques and several markers have been identified that are increased among patients with preeclampsia, but no test is highly sensitive. In the future, a combination of markers likely will be used to assess risk and, establish the diagnosis, and test treatment strategies. Such an approach would allow for more refined treatment studies of patients who are at highest risk for preeclampsia.

Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia

Preeclampsia, a syndrome affecting 5% of pregnancies, causes substantial maternal and fetal morbidity and mortality. The pathophysiology of preeclampsia remains largely unknown. It has been hypothesized that placental ischemia is an early event, leading to placental production of a soluble factor or factors that cause maternal endothelial dysfunction, resulting in the clinical findings of hypertension, proteinuria, and edema. Here, we confirm that placental soluble fms-like tyrosine kinase 1 (sFlt1), an antagonist of VEGF and placental growth factor (PlGF), is upregulated in preeclampsia, leading to increased systemic levels of sFlt1 that fall after delivery. We demonstrate that increased circulating sFlt1 in patients with preeclampsia is associated with decreased circulating levels of free VEGF and PlGF, resulting in endothelial dysfunction in vitro that can be rescued by exogenous VEGF and PlGF. Additionally, VEGF and PlGF cause microvascular relaxation of rat renal arterioles in vitro that is blocked by sFlt1. Finally, administration of sFlt1 to pregnant rats induces hypertension, proteinuria, and glomerular endotheliosis, the classic lesion of preeclampsia. These observations suggest that excess circulating sFlt1 contributes to the pathogenesis of preeclampsia.

Longitudinal serum concentrations of placental growth factor: evidence for abnormal placental angiogenesis in pathologic pregnancies

OBJECTIVE

Complicated pregnancies demonstrate abnormal decidual and placental villous vasculature. We examined maternal concentrations of vascular endothelial growth factor and placental growth factor in normal pregnancies and in pregnancies that were complicated by isolated idiopathic small-for-gestational-age (SGA) newborn infants, preeclampsia alone, or preeclampsia with SGA newborn infants at the time of clinical disease and before the onset of clinical signs.

STUDY DESIGN

Serum vascular endothelial growth factor and placental growth factor were measured by enzyme-linked immunosorbent assay in cross-sectional and longitudinal cohorts of pregnant nulliparous women. The results were compared by Wilcoxon tests or a mixed-models method, respectively.

RESULTS

In the cross-sectional study, serum placental growth factor was reduced in abnormal pregnancy relative to control subjects (SGA newborn infants, 18 [P =.04]; preeclampsia, 20; or preeclampsia with small- for-gestational-age newborn infants, 11 [P =.0001]) as early as 15 to 19 weeks of gestation in preeclampsia with SGA newborn infants. Vascular endothelial growth factor was <30 pg/mL in all serum specimens from pregnant women.

CONCLUSION

We postulate that decreased placental growth factor production results in abnormalities of placental angiogenesis through direct and indirect effects on other vasculotropic growth factors.

Levels of placenta growth factor in gestational trophoblastic diseases

OBJECTIVE

The aim of the current study was to investigate levels of placenta growth factor in the tissues and sera of the patients with gestational trophoblastic disease and to determine its usefulness for the treatment of gestational trophoblastic disease.

STUDY DESIGN

Placenta growth factor concentrations were measured in the tissue homogenates of 12 normal placentas, 33 complete hydatidiform moles, and 6 gestational choriocarcinomas. Serum placenta growth factor levels were determined in 59 women with normal pregnant course, in 30 women with complete hydatidiform mole, in 36 women with persistent gestational trophoblastic disease, and 100 nonpregnant healthy volunteers.

RESULTS

Serum and tissue placenta growth factor levels in the patients with mole tended to be decreased compared with the levels in normal pregnancy; the levels were increased significantly in patients with choriocarcinoma. When serum placenta growth factor levels were >20 pg/mL (normal upper limit in nonpregnant women), placenta growth factor-to-human chorionic gonadotropin ratios were increased significantly in patients with persistent gestational trophoblastic disease.

CONCLUSION

Serum placenta growth factor levels are not of any predictive value in patients with hydatidiform mole. However, elevated serum placenta growth factor levels with increased placenta growth factor-to-human chorionic gonadotropin ratios are suggestive of persistent gestational trophoblastic disease.

A longitudinal study of biochemical variables in women at risk of preeclampsia

OBJECTIVE

The purpose of this study was to characterize gestational profiles of biochemical markers that are associated with preeclampsia in the blood of pregnant women in whom preeclampsia developed later and to compare these markers with the markers of women who were delivered of small-for-gestational-age infants without preeclampsia and with women who were at low risk for the development of preeclampsia.

STUDY DESIGN

This was a prospective case control study. The subjects were women at risk of preeclampsia who were enrolled in the placebo arm of a clinical trial. Indices of antioxidant status, oxidative stress, placental and endothelial function, and serum lipid concentrations were evaluated from 20 weeks of gestation until delivery in 21 women in whom preeclampsia developed later, in 17 women without preeclampsia who were delivered of small-for-gestational-age infants, and in 27 women who were at low risk for the development of preeclampsia.

RESULTS

Ascorbic acid was reduced early in preeclampsia and small-for-gestational-age pregnancies. Leptin, placenta growth factor, the plasminogen activator inhibitor (PAI-1)/PAI-2 ratio, and uric acid were predictive of the development of preeclampsia.

CONCLUSION

Gestational profiles of several markers were abnormal in the group with preeclampsia, and some of the markers that may prove useful in the selective prediction of preeclampsia were identified.

Placental development in normal and compromised pregnancies-- a review

Intrauterine growth restriction (IUGR) is a significant cause of infant mortality and morbidity. It is now clear that IUGR infants exhibit higher rates of coronary heart disease, type 2-diabetes, hypertension and stroke as adults. Therefore, fetal growth not only impacts the outcome of the perinatal period, but also impacts adult well-being. The etiologies of IUGR are numerous, but are often associated with abnormalities in placental structure and function. The process of implantation and placentation requires the production of a plethora of growth factors, cell-adhesion molecules, extracellular matrix proteins, hormones and transcription factors. Many of these exhibit altered expression within the placenta of IUGR pregnancies. However, it has been difficult to fully assess their role during the development of placental insufficiency (PI) in the human, underscoring the need for animal models. Using an ovine model of PI-IUGR we have observed changes in the expression of vascular endothelial growth factor, placental growth factor, their common receptors, as well as angiopoietin 2 and its receptor, Tie 2. We found that changes in these growth factors can be associated with both acute and chronic changes in placental vascular structure and function. These studies and others are providing needed insight into the developmental chronology of placental insufficiency.

Hemochorial placentation in the primate: expression of vascular endothelial growth factor, angiopoietins, and their receptors throughout pregnancy

Vascular development and its transformation are necessary for successful hemochorial placentation, and vascular endothelial growth factor (VEGF), angiopoietins, and their receptors may be involved in the molecular regulation of this process. To determine the potential role of these putative regulators in a widely studied primate, the common marmoset, we investigated their mRNA expression and protein location in the placenta throughout pregnancy using in situ hybridization, Northern blot analysis, and immunocytochemistry. VEGF was localized in decidual and cytotrophoblast cells, and its highest expression was found in the maternal decidua. The Flt receptor was exclusively detected in the syncytial trophoblast with increasing expression in placentae from 10 wk to term. Soluble Flt (sFlt) was also detectable by Northern blot analysis. KDR receptor expression was restricted to mesenchymal cells during early placentation and to the fetoplacental vasculature during later placentation. KDR expression increased throughout pregnancy. Angiopoietin-1 (Ang-1) was localized in the syncytial trophoblast, being highly expressed in the second half of gestation. Ang-2 mRNA localized exclusively to maternal endothelial cells, and was highly expressed in 10-wk placentae. The Tie-2 receptor was found in cytotrophoblast cells and in fetal and maternal vessels. High Tie-2 levels were detected in the wall of chorion vessels at 14-wk, 17-wk, and term placentae. These results suggest that the processes of trophoblast invasion, maternal vascular transformation, and fetoplacental vascular differentiation and development are regulated by the specific actions of angiogenic ligand-receptor pairs. Specifically, 1) VEGF/Flt and Ang-1/Tie-2 may promote trophoblast growth, 2) VEGF/KDR and Ang-1/Tie-2 may support fetoplacental vascular development and stabilization, 3) sFlt may balance VEGF actions, and 4) Ang-2/Tie-2 may remodel the maternal vasculature.

Raised maternal serum placenta growth factor concentration during the second trimester is associated with Down syndrome

OBJECTIVES

To compare early second-trimester maternal serum placenta growth factor concentrations in Down syndrome pregnancies and those in normal pregnancies.

METHODS

A case-control study was performed to evaluate the maternal serum placenta growth factor concentrations in 36 Down syndrome and 320 normal pregnancies with matched gestational age during the second trimester. For the detection of serum concentrations of placenta growth factor, a quantitative sandwich enzyme immunoassay technique (R & D Systems Inc., Minneapolis, Minnesota, USA) was performed.

RESULTS

Using a multiple linear regression model, maternal serum placenta growth factor level was associated with gestational age (p<0.001) and the existence of Down syndrome pregnancy (p<0.001). After converting maternal serum placenta growth factor concentrations of each analyte to multiples of the appropriate gestational median (MoM), placenta growth factor MoM (p<0.001) was revealed to be an independent variable for Down syndrome pregnancies after adjusting for the effects of maternal age (p<0.001), free beta-hCG (p<0.001) and AFP (p=0.014) by multivariate logistic regression analysis.

CONCLUSIONS

Maternal serum placenta growth factor concentration was elevated in Down syndrome pregnancies during the early second trimester. Placenta growth factor might be a novel marker for maternal serum Down syndrome screening.

Low maternal serum levels of placenta growth factor as an antecedent of clinical preeclampsia

OBJECTIVE

Maternal serum placenta growth factor levels have been shown to be significantly reduced in women with established preeclampsia. However, the temporal change in serum placenta growth factor levels before the clinical onset of preeclampsia is not known.

STUDY DESIGN

Serum samples were collected from patients at the first prenatal (5-15 weeks' gestation), second-trimester (16-20 weeks' gestation), and third-trimester (26-30 weeks' gestation) visits. Serum placenta growth factor levels were determined and analyzed according to pregnancy outcome.

RESULTS

Maternal placenta growth factor levels during normal gestation increased dramatically from the first to the third trimester. At the same gestational time points, in contrast, significantly lower serum placenta growth factor levels were found in patients in whom mild or severe preeclampsia eventually developed (P <.01). Low maternal serum placenta growth factor levels during early gestation were associated with a significant odds ratio for development of preeclampsia (P <.005).

CONCLUSION

Relatively decreased levels of serum placenta growth factor occur before the onset of clinical preeclampsia, which suggests that placenta growth factor measurement could be used to discriminate those pregnancies predisposed to development of preeclampsia.

Placenta growth factor is not an early marker for the development of severe preeclampsia

OBJECTIVE

Our purpose was to determine whether plasma concentrations of placenta growth factor may be used as a marker for women who ultimately have severe preeclampsia.

STUDY DESIGN

We performed a nested case-control study to compare plasma concentrations of placenta growth factor in women with severe preeclampsia with the concentrations in normotensive pregnant control subjects. Plasma samples were collected at <20 weeks' gestation and again in the third trimester. Twenty-two women who ultimately had severe preeclampsia were matched for gestational age at delivery with 22 normotensive control subjects. Placenta growth factor concentrations were measured by a specific antigen capture enzyme-linked immunosorbent assay. Comparisons were made by using the Mann-Whitney U test for nonparametric data such as placenta growth factor concentrations. The Student t test was used for parametric data.

RESULTS

A total of 880 pregnant women were screened. Severe preeclampsia developed in 22, for an incidence of 2.5%. As expected, women with severe preeclampsia had significantly higher systolic and diastolic blood pressures, and their infants had lower birth weights. Placental weights at delivery were similar between those with severe preeclampsia and control subjects (659 vs 699 g; P =.51). During the third trimester, the median placenta growth factor concentrations were significantly lower in women with severe preeclampsia than in normotensive control subjects (125 vs 449 pg/mL; P =.003). When samples drawn at <20 weeks' gestation were compared, there was no difference between the group with severe preeclampsia and those who remained normotensive (98.8 vs 56.34 pg/mL; P =.15).

CONCLUSION

During the third trimester, patients with severe preeclampsia have decreased maternal concentrations of placenta growth factor. This difference is not seen earlier in pregnancy. Lower concentrations of placenta growth factor may be a result of severe preeclampsia rather than a causal factor. Placenta growth factor is not a good marker for the subsequent development of severe preeclampsia.

Angiogenesis during implantation, and placental and early embryonic development

Angiogenesis, the development of new capillaries from pre-existing vessels, is induced by inflammation, wound healing, immune reactions and neoplasia, and is required for tumour growth and progression. Angiogenesis participates in a wide range of ovulatory-related and non-ovulatory-related reproductive processes. We present a review of current data pertaining to angiogenesis of pregnancy, with specific emphasis on implantation and placental and embryonic development in both normal physiology processes and various pathological conditions. To this goal, MEDLINE, Current Contents and Index Medicus were searched for studies published between 1966 and August 1999. Pertinent studies (including human and animal models) pertaining to angiogenesis of implantation and placental and embryonic development were reviewed. Current literature supports that angiogenesis is an essential physiological component of implantation, and placental and embryonic development. Angiogenesis also actively participates in abnormal implantation, and various pathological processes of the placenta including those observed in association with pre-eclampsia, growth restriction, maternal anaemia in the first-trimester and other hypoxia-related conditions during pregnancy. Finally, administration of an angiogenesis inhibitor (AGM-1470) in mice has been shown to result in complete failure of embryonic growth due to interference with decidualization, placental and yolk sac formation, and embryonic vascular development.

Reductions of vascular endothelial growth factor and placental growth factor concentrations in severe preeclampsia

OBJECTIVE

The aim of this study was to determine whether plasma concentrations of vascular endothelial growth factor and placental growth factor are altered in women with severe preeclampsia.

STUDY DESIGN

We performed a case-control study to compare plasma concentrations of vascular endothelial growth factor and placental growth factor between women with severe preeclampsia and normotensive women admitted for delivery. Twenty-one women with severe preeclampsia were matched for gestational age and ethnicity with 21 normotensive women. Vascular endothelial growth factor and placental growth factor concentrations were measured with a specific antigen-capture enzyme-linked immunosorbent assay.

RESULTS

Women with severe preeclampsia demonstrated significantly lower plasma concentrations of both vascular endothelial growth factor (6.36 +/- 3.96 pg/mL vs 18.65 +/- 5.98 pg/mL; P <.0001) and placental growth factor (138 +/- 119 pg/mL vs 531 +/- 340 pg/mL; P <.0001) than did women with normotensive pregnancy. Logistic regression analysis showed an independent association between plasma vascular endothelial growth factor concentration and plasma placental growth factor concentration and preeclampsia.

CONCLUSION

Patients with severe preeclampsia had decreased maternal serum concentrations of both vascular endothelial growth factor and placental growth factor.