https://orcid.org/0000-0001-9355-7753
Abstract
Objective
Endothelial dysfunction is a major feature of preeclampsia. sVE-cadherin plays a role in the preservation and regulation of the endothelial barrier. For that reason, to evaluation of sVE-cadherin may help elucidate the disease pathophysiology of preeclampsia.
Methods
The sample size was calculated as a minimum of 46 pregnant women for each group based on serum sVE-Cadherin levels in a pilot study of 10 preeclamptic and 10 control groups. Hundred-twenty pregnancies complicated with early-onset (n = 60) and late-onset (n = 60) preeclampsia were compared with 120 gestational-age (GA)-matched (±1 week) uncomplicated pregnancies. The venous blood sampling was performed upon preeclampsia diagnosis prior to the onset of the labor in the preeclampsia group and the matching (±1 week) pregnancy week in the control group. Demographic and biochemical parameters were evaluated.
Results
Mean serum sVE-Cadherin was significantly higher in women with EOPE compared to that of the GA-matched control group (5.86 ± 1.57 ng/mL vs. 2.28 ± 0.80 ng/mL, p < 0.001), in women with LOPE compared to that of the GA-matched control group (3.11 ± 0.97 ng/mL vs. 1.69 ± 0.87 ng/mL, p < 0.001), and in women with EOPE compared to that of LOPE group (5.86 ± 1.57 ng/mL vs. 3.11 ± 0.97 ng/mL, p < 0.001) after correction for GA. Serum sVE-Cadherin positively correlated with systolic and diastolic blood pressure and a negative correlation with gestational age at sampling.
Conclusion
The serum level of sVE-Cadherin was higher in women with preeclampsia than that of GA-matched healthy pregnant women, in women with EOPE compared to that of LOPE. sVE-Cadherin is an important marker in early-onset pre-eclampsia with severe clinical findings.
Introduction
Endothelium, which was regarded as a mechanical barrier until the 1970s, is now considered an organ that has a role in providing hemostasis, maintaining optimal vascular permeability and tonus, regulating inflammation, and controlling angiogenesis [Citation1–3]. One of these functions, maintaining optimal vascular permeability, is performed by transcellular and paracellular pathways. Transcellular permeability is provided by windows in the cell membrane and vesiculovacuolar organelles within the cell, while paracellular permeability is provided by the opening and closing of endothelial junctions [Citation4–6]. There are two types of junctions in the endothelium: tight and adherence junctions. An essential component of adherence junctions is VE-cadherin synthesized by endothelial cells, and it can be detected in serum in its soluble form [Citation7].
Vascular endothelial (VE)-cadherin is the most crucial transmembrane adhesion molecule, weighing 150 kDa, located in the adherence junctions between endothelial cells, and plays a role in the preservation and regulation of the endothelial barrier [Citation8]. It is a dimeric protein with an intra- and extracellular region [Citation9]. The function of VE-cadherin is regulated in three ways: endocytosis of VE-cadherin as a whole, shedding of the extracellular region into circulation, and reorganization of VE-cadherin on the cell membrane. These reorganizations disrupt VE-cadherin-mediated endothelial cell-cell adhesion and barrier integrity, leading to vascular effluence, tissue edema, as well as organ dysfunction. Clinically, it is not possible to evaluate the overall endocytosis or cell membrane reorganization of VE-cadherin. However, measurement of the circulating extracellular region of VE-cadherin, soluble vascular endothelial (sVE)-cadherin, can be used to assess endothelial adherence junction damage [Citation7]. In the review by Blaise et al. [Citation10], the increase in serum levels of sVE- cadherin was observed in many diseases (atherosclerosis, rheumatoid arthritis, Henoch-Schönlein purpura, Behçet’s disease), and it was argued that this substance was a marker of endothelial dysfunction. Endothelial dysfunction is a major feature of preeclampsia. For that reason, evaluation of sVE-cadherin may help elucidate the disease pathophysiology of preeclampsia.
Although serum levels of sVE-cadherin have been evaluated in many diseases associated with endothelial dysfunction, there are no studies in preeclampsia patients. In the present study, serum levels of sVE-cadherin were investigated in preeclampsia and control pregnant women for the first time in the literature.
Material and methods
This cross-sectional study was carried out in Istanbul Cerrahpasa University, University Hospital for Obstetrics and Gynecology, Istanbul, Turkey. Hundred-twenty pregnancies complicated with early-onset (n = 60) and late-onset (n = 60) preeclampsia were compared with 120 gestational-age (GA)-matched (±1 week) uncomplicated pregnancies. All the patients agreed to give informed consent. The study protocol was authorized by the Ethics Committee of Istanbul Cerrahpasa University, School of Medicine (Date/number: 04.04.2014, Number: 8879 and 11/03/2019 - 39712 83045809 − 604.01.02).
The inclusion criteria were age between 18 and 40 years old and singleton pregnancy. The control group’s GA-matching (±1 week) was performed according to the week of blood sampling in the study group.
Exclusion criteria were multifetal gestation, known fetal malformations, known acute or chronic systemic diseases, any known hypertensive disorders, any diabetes type, preterm labor, and prelabour rupture of membranes, and other known inflammatory disorders as well as infections, smoking and alcohol use, assisted reproductive technologies (ART) pregnancies.
The diagnosis of preeclampsia was made with the new beginning of hypertension (measured twice with an interval of a minimum of 4 h, blood pressure ≥140/90 mmHg) after the 20th gestational week (gestational week) and one or more of the followings: Proteinuria (300 mg/day or ≥0.3 protein to creatinine ratio) AND/OR maternal organ dysfunction such as acute kidney injury; liver involvement ± pain in the right upper quadrant or epigastric region; neurological impairment; or hematological complications [Citation11]. We further divided the preeclampsia into subgroups: EOPE (Early-onset Preeclampsia): delivery <34 + 0 gestational weeks, LOPE (Late-onset Preeclampsia): delivery ≥34 + 0 gestational weeks [Citation11].
AT performed the fetobiometrical examinations with Voluson 730 Pro ultrasonography (GE-Healthcare, General Electric, Zipf, Austria).
Blood sampling and biochemical methods for measurements
The venous blood sampling was performed upon preeclampsia diagnosis prior to the onset of the labor in the preeclampsia group and the matching (±1 week) pregnancy week in the control group. The biochemical examinations were performed in a blinded fashion. The venous blood samples were collected in serum tubes between 8:00 am and 10:00 am before breakfast at the time of recruitment and readily centrifuged at 1000 g for 15 min at 2–8 °C. The serum phase was obtained and stored at −80 °C until quantitative measurement using the Human Cadherin (sVE-Cadherin) ELISA kit, SL3097Hu, Sunlong Biotech, Hangzhou, China (Detection range: 0.8 ng/mL-50 ng mL, sensitivity: 0.1 ng/mL), strictly according to the manufacturer’s instructions. A standard automated plate reader (Thermo Scientific Microplate Reader, MA) was used for the optical density (wavelength of 450 nm).
Sample size calculation and statistical analyses
The sample size was calculated according to the serum sVE-Cadherin levels. Ten women with preeclampsia (4.02 ± 2.40 ng/mL) and ten women without preeclampsia (2.21 ± 1.83 ng/mL) were evaluated in a pilot study. Taking the α-error as 0.05 and the target power as 95%, we determined the minimum required sample size as 46 women in each group. The women included in the pilot study were excluded from the statistical analysis of the current study.
The Statistical Package for the Social Sciences (SPSS) software version 24.0 (SPSS Inc., Chicago, IL) was used for establishing the database and statistical calculations. The distribution’s normality of parametric variables was evaluated using the Shapiro-Wilk test. Age, BMI, WBC and platelet count, creatinine, and uric acid showed normal distributions. Systolic and diastolic arterial blood pressure (ABP), sVE-Cadherin, parity, GA at sampling, total bilirubin, urea, AST, and ALT showed non-homogeneous distributions. Univariate linear analysis with correction for GA was used to compare the sVE-Cadherin levels in EOPE and LOPE groups. A partial correlation test was performed to evaluate the correlations between sVE-Cadherin and relevant parameters with necessary corrections. The statistical significance threshold was accepted as <0.05.
Results
The comparisons of women with EOPE and women in the control group GA-matched for the EOPE group, and women with LOPE and women in the control group GA-matched for the LOPE group showed that there were no significant differences regarding the patient demographics (mean age, BMI, parity, and GA at sampling), the platelet count, AST, ALT, and total bilirubin ( and ).
Table 1. Demographic, clinical and laboratory features of the women with EOPE and women in the control group GA-matched for EOPE.
Table 2. Demographic, clinical and laboratory features of the women with LOPE and women in the control group GA-matched for LOPE.
Mean systolic and diastolic blood pressure, mean creatinine, uric acid, and urea levels were significantly higher in both preeclampsia groups compared to the GA-matched controls.
Mean serum sVE-Cadherin was significantly higher in women with EOPE compared to that of the GA-matched control group (5.86 ± 1.57 ng/mL vs. 2.28 ± 0.80 ng/mL, p < 0.001), in women with LOPE compared to that of the GA-matched control group (3.11 ± 0.97 ng/mL vs. 1.69 ± 0.87 ng/mL, p < 0.001), and with EOPE and LOPE groups (5.86 ± 1.57 ng/mL vs. 3.11 ± 0.97 ng/mL, p < 0.001) after correction for GA.
The correlation analysis of sVE-Cadherin and various parameters in all participants were presented in supplementary Table 1. Serum sVE-Cadherin positively correlated with systolic and diastolic blood pressure and a negative correlation with gestational age at sampling ().
Figure 1. Scatterplot analysis of the correlation between sVE-Cadherin and gestational age. The circles show the mean sVE-Cadherin value for that pregnancy week.
Discussion
In this study we found that, the serum level of sVE-Cadherin was higher in preeclamptic pregnant women, especially in early-onset preeclamptic cases, than healthy pregnant women. Also, we found that this elevation was positively correlated with systolic and diastolic pressure and negatively correlated with gestational age. These results indicate that, sVE-Cadherin is an important marker in early-onset pre-eclampsia with severe clinical findings.
There are no studies evaluating the serum level of sVE-Cadherin in hypertensive pregnant women or non-pregnant hypertensive patients. However, there are studies evaluating VE-cadherin level at tissue and cell level in preeclamptic, diabetic, and healthy pregnant women, and studies measuring serum sVE-Cadherin levels in diseases presenting with endothelial dysfunction other than hypertension [Citation12–19]. The results of these studies may help to analyze the results of the present study.
In normal pregnant women, the endothelium of the placental vessels is continuous and contains junctions that restrict the movement of large hydrophilic molecules along the paracellular slits [Citation12]. The primary regulator of paracellular permeability in placental capillaries is VE-cadherin [Citation9,Citation13,Citation14]. In one study it has been shown that the endothelial adhesion molecules, including VE-cadherin, are not sufficiently expressed in cytotrophoblasts invading the uterus of preeclamptic women [Citation15]. The decreased expression of VE-cadherin has been associated with abnormal placental development in these women [Citation16]. Another study shows that the placental expression of endothelial junction proteins such as CD31 and VE-cadherin does not change in preeclamptic pregnant women [Citation17]. It was found that, unlike normal pregnant women, adherence junctions in fetoplacental vessels of pregnant women with Type 1 diabetes mellitus characterized by endothelial dysfunction are excessively phosphorylated, and the immune reactivity of VE-cadherin and β-catenin is lost [Citation18]. According to these studies, it can be concluded that VE-cadherin expression, which is the main component of endothelial adherence junctions, is decreased in pregnant placentas complicated by diseases characterized by endothelial dysfunction, including preeclampsia. Accordingly, VE-cadherin expression should also decrease in vascular endothelial cells of preeclamptic pregnant women. Although it is difficult to measure this directly, it can be detected indirectly. CD-34 (+) and VE-cadherin (+) are used as indicators of endothelial progenitor cells (EPCs). Serum counts of these cells were found to be increased in preeclamptic pregnant women, which has been accepted as an effort to correct endothelial dysfunction [Citation19]. This is because EPCs are produced in the bone marrow and can differentiate into mature endothelial cells, create new capillary vessels, and generate paracrine molecules that assist in recovering the vascular wall [Citation20]. Numerous chemotactic factors and cytokines that emerge in case of endothelial damage and ischemia cause these cells to be released from the bone marrow into the bloodstream.
The first study evaluating the serum level of sVE-cadherin was conducted in 2004 with coronary atherosclerosis patients (patient groups with acute myocardial infarction, angina pectoris, and previous myocardial infarction) [Citation21]. Serum levels in these patients were higher compared to those in healthy patients. Although it was accepted as a marker of the disease, it was concluded that VE-cadherin was insufficient to reveal disease severity. However, in many systemic vasculitides characterized by inflammation (such as rheumatoid arthritis, Behçet’s disease, Henoch-Schönlein purpura, hemolytic uremic syndrome, chronic spontaneous urticaria), the serum level of sVE-cadherin was found to be higher than healthy individuals and was also found to be associated with the severity of the disease [Citation22–26]. In patients with chronic venous insufficiency characterized by endothelial dysfunction, as the disease severity increased, the serum level of sVE-cadherin decreased, contrary to what was expected [Citation27]. This decrease was attributed to this molecule’s sequestration on endothelial cell surface due to inflammatory mediators and ROS [Citation28,Citation29]. In the present study, the serum level of sVE-cadherin was higher in the preeclampsia patient group than the healthy pregnant group, similar to most of the studies mentioned above. This elevation was associated with the severity of the disease, consistent with other studies except the study conducted on patients with coronary atherosclerosis. The fact that the serum level of sVE-cadherin was positively correlated with systolic and diastolic pressure in the present study and the higher serum level in early preeclampsia compared to late preeclampsia supports the correlation of this molecule with the severity of the disease. The absence of a difference in the serum level of sVE-Cadherin in individuals with inflammatory skin diseases than healthy individuals suggests that this molecule is a marker of systemic endothelial dysfunction rather than local [Citation24].
In a study conducted on 240 people aged 18–24 years, the serum level of sVE-Cadherin was associated with increased systolic pressure, a component of metabolic syndrome [Citation30]. This association suggests that endothelial functions are interrelated and that sVE-Cadherin, a marker of endothelial dysfunction, can be used to predict hypertension. In the present study, systolic and diastolic blood pressure levels, which are characteristic findings of endothelial dysfunction, were positively correlated with the serum level of sVE-Cadherin. Preeclamptic pregnant women are young patients at risk of metabolic syndrome, and this risk is higher in early-onset preeclamptic patients. In correlation with the severity of the disease, the serum level of sVE-Cadherin was higher in early-onset preeclamptic women.
In our study, the serum level of sVE-Cadherin was negatively correlated with gestational age in the preeclampsia and non-preeclampsia groups. In healthy pregnant women, there is no increased endothelial dysfunction; for that reason, there is no increase in sVE-Cadherin due to endothelial damage. Hemodilution and lesser EPC activity may also contribute to keeping the sVE-Cadherin levels low during the late pregnancy. Therefore, evaluation of the sVE-Cadherin levels in the first trimester may help better explore the change of sVE-Cadherin during the physiological pregnancy.
In the light of the above information, it can be speculated that in pre-eclampsia, which is characterized by endothelial dysfunction, VE-cadherin expression at the placental tissue level decreases, whereas sVE-Cadherin level increases due to the increase in bone marrow-derived EPC activity to repair endothelial damage in the maternal circulation.
The strengths of this study are that it is the first study conducted in preeclamptic pregnant women, and the limitations are that placental VE-cadherin expression and perinatal outcomes were not evaluated.
In conclusion, the serum level of sVE-Cadherin was higher in preeclamptic pregnant women, especially in early-onset preeclamptic cases, than healthy pregnant women. We found that this elevation was positively correlated with systolic and diastolic pressure and negatively correlated with gestational age. sVE-Cadherin is an important marker in early-onset pre-eclampsia with severe clinical findings. But, more comprehensive studies are needed to investigate the relationship between increased vascular permeability as a finding of endothelial dysfunction in preeclamptic pregnancies and serum levels of the sVE-Cadherin.
Supplemental Material
Download MS Word (15.9 KB)Acknowledgments
We want to thank our beloved nurse Medine Eltutan from our pregnancy outpatient clinic in Istanbul Cerrahpasa University Hospital, for her kind support and dedication during the patient recruitment.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.
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References
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