Expression of angiopoietic factors in normal and type-I diabetes human placenta: a pilot study

Differences of Angiogenesis Factors in Tumor and Diabetes Mellitus

Angiogenesis, as a process occurring under the regulation of a variety of factors, is one of the important ways of vascular development. It coexists in a variety of pathological and physiological processes. Now a large number of studies have proved that tumor growth, metastasis, and various vascular complications of diabetes are closely related to angiogenesis, and an increasing number of studies have shown that there are many common factors between the two. But angiogenesis is the opposite of the two: it is enhanced in tumors and suppressed in diabetes. Therefore, this review discusses the causes of the phenomenon from the expression of various factors affecting angiogenesis in these two diseases and their effects on angiogenesis in the relevant microenvironment, as well as the application status of these factors or cells as therapeutic targets in the treatment of these two diseases.

Gestational diabetes mellitus is associated with increased pro-migratory activation of vascular endothelial growth factor receptor 2 and reduced expression of vascular endothelial growth factor receptor 1

Placentas from gestational diabetes mellitus (GDM) are often hypervascularized; however, participation of vascular endothelial growth factor (VEGF) and its receptors in this placental adaptation is unclear. We aimed to test whether changes in phosphorylation of tyrosine 951 or tyrosine 1175 (pY951 or pY1175) of the vascular endothelial growth factor receptor 2 (KDR) are associated with the proangiogenic state observed in placentas from GDM. We obtained placental samples from women with normal pregnancies (n = 24) or GDM (n = 18). We measured the relative expression of markers for endothelial cell number (CD31, CD34), VEGF, vascular endothelial growth factor receptor 1 (Flt-1), KDR, pY951 and pY1175 of KDR in placental homogenate. Immunohistochemistry of placental blood vessels were performed using CD34. Proliferation and migration of human umbilical vein endothelial cells (HUVEC) obtained from normal pregnancy and GDM were determined in absence or presence of conditioned medium (CM) harvested from GDM or normoglycemic HUVEC cultures. GDM was associated with more CD31 and CD34 protein compared to normal pregnancy. High number, but reduced area of placental blood vessels was found in GDM. Reduced Flt-1 levels (mRNA and protein) are associated with reduced KDR mRNA, but higher KDR protein levels in placentas from GDM. No significant changes in Y951-or Y1175-phosphorylation of KDR in placentas from GDM were found. GDM did not alter proliferation of HUVECs, but enhanced migration. Conditioned medium harvested from GDM HUVEC cultures enhanced KDR protein amount, tube formation capacity and cell migration in HUVEC isolated from normoglycemic pregnancies. The data indicate that GDM is associated with reduced expression of Flt-1 but high pro-migratory activation of KDR reflecting a proangiogenic state in GDM.

A preliminary evaluation of VEGF-A, VEGFR1 and VEGFR2 in patients with well-controlled type 2 diabetes mellitus

OBJECTIVE

Decompensated chronic hyperglycemia often leads to late microvascular complications such as retinopathy, diabetic foot syndrome, and diabetic kidney disease. The aim of this study was to determine the concentration of vascular endothelial growth factor A (VEGF-A) and its receptors in patients with well-controlled diabetes.

METHODS

The study was conducted on 31 patients with well-controlled type 2 diabetes without micro- or macroangiopathy. Thirty healthy volunteers were enrolled in a control group. Serum concentrations of VEGF-A, VEGF receptors 1 and 2 (VEGFR1 and VEGFR2), fasting glucose, and lipid profiles were measured, and the plasma concentration of glycated hemoglobin (HbA1c) was determined.

RESULTS

No significant differences were observed between the concentration of VEGF-A, VEGFR1 or VEGFR2 in the subject group and that in the control group. Positive correlations were noted between the levels of VEGF-A, VEGFR2, and triglyceride, and there was a negative correlation between the levels of VEGFR2 and high-density lipoprotein (HDL)-cholesterol in the study group.

CONCLUSIONS

The concentrations of VEGF-A and its receptors 1 and 2 in patients with well-controlled diabetes are comparable to those of healthy individuals, which may indicate that appropriate control of glucose levels delays the occurrence of vascular complications. A negative correlation between VEGFR2 and HDL-cholesterol levels, and positive correlations between VEGF-A, VEGFR2, and triglyceride levels, suggest that lipid abnormalities occurring in diabetes may be involved in the modulation of angiogenesis.

Glucose, insulin, and oxygen interplay in placental hypervascularisation in diabetes mellitus

The placental vasculature rapidly expands during the course of pregnancy in order to sustain the growing needs of the fetus. Angiogenesis and vascular growth are stimulated and regulated by a variety of growth factors expressed in the placenta or present in the fetal circulation. Like in tumors, hypoxia is a major regulator of angiogenesis because of its ability to stimulate expression of various proangiogenic factors. Chronic fetal hypoxia is often found in pregnancies complicated by maternal diabetes as a result of fetal hyperglycaemia and hyperinsulinemia. Both are associated with altered levels of hormones, growth factors, and proinflammatory cytokines, which may act in a proangiogenic manner and, hence, affect placental angiogenesis and vascular development. Indeed, the placenta in diabetes is characterized by hypervascularisation, demonstrating high placental plasticity in response to diabetic metabolic derangements. This review describes the major regulators of placental angiogenesis and how the diabetic environment in utero alters their expression. In the light of hypervascularized diabetic placenta, the focus was placed on proangiogenic factors.

Markers of endothelial cell dysfunction are increased in human omental adipose tissue from women with pre-existing maternal obesity and gestational diabetes

OBJECTIVE

To determine the effect of maternal obesity and gestational diabetes mellitus (GDM) on the expression and release of genes involved in endothelial cell dysfunction in human placenta and omental adipose tissue.

MATERIALS/METHODS

Human placenta and omental adipose tissue were obtained from non-obese and obese normal glucose tolerant (NGT) women and women with GDM at the time of Caesarean section. Quantitative RT-PCR was performed to determine the level of expression. Tissue explants were performed to determine the release of proteins of interest.

RESULTS

There was no effect of pre-existing maternal obesity or GDM on placental gene expression or secretion of members of the VEGF family members (PLGF and VEGF-A expression and secretion; sFlt-1 release; VEGFR1 and VEGFR2 mRNA expression); FGFR1 mRNA expression, FGF2 mRNA expression and secretion; endoglin mRNA expression and secretion (sEng); and the adhesion molecules ICAM-1 and VCAM-1. On the other hand, in omental adipose tissue, pre-existing maternal obesity and GDM were associated with increased gene expression of PLGF, endoglin and ICAM-1 and increased secretion of PLGF, sFlt-1, FGF2, sEng and sICAM-1. There was, however, no effect of maternal pre-existing obesity and GDM on VEGF-A, VEGFR1, VEGFR2, FGFR1 and VCAM-1 expression or secretion.

CONCLUSIONS

This study demonstrated the presence of abnormal expression and secretion of angiogenic proteins and adhesion molecules in omental adipose tissue, but not placenta, from pregnant women with GDM and pre-existing maternal obesity. Increased angiogenic and adhesion molecules released from adipose tissue may affect angiogenesis, inflammation and or lipid and glucose metabolism in both mum and her offspring.

Circulating Vascular Growth Factor (VEGF) Angiopoietin-1 (Angi-1) and Soluble Tie-2 Receptor in Pregnancy Complicated with Pre-eclampsia: A Prospective Study

BACKGROUND

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. Although the etiology of preeclampsia (PE) is still unclear, recent studies suggest that its major phenotypes, high blood pressure and proteinuria, are due in part to the disturbed angiogenic process.

STUDY DESIGN

This study included the following groups: (1) women with normal pregnancies (n = 150), (2) patients with PE (n = 88), and (3) patients who delivered small growth for date (SGA) neonate (n = 50). Maternal serum concentrations of VEGF, Angi-1, and sTie-2 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

The median maternal serum concentration of sVEGF and sAngi-1 was lower in normal pregnant women as compared to that in PE and SGA and the differences were statistically significant (P < 0.01). In contrast, there is a significant reduction in sTie-2 levels in PE and SGA groups as compared to that in normal pregnancy group (P < 0.01). Serum VEGF and Angi-1 were significantly higher in the late onset PE subgroup as compared to that in the early onset PE (P < 0.01), but sTie-2 was not significantly different in the 2 subgroups (P > 0.05). Serum VEGF, sAngi-1, and sTie-2 were significantly higher and Tie-2 was significantly lower in the severe PE subgroup as compared to that of the milder PE subgroup (P < 0.01 for all).

CONCLUSION

Patients with PE and those with SGA fetuses have lower median serum concentrations of sTie-2 and higher sVEGF and sAngi-1 than women with normal pregnancies. These findings lend support to the hypothesis that circulating angiogenic proteins may have an important biologic role in PE.

Compressive force induces VEGF production in periodontal tissues

During orthodontic tooth movement, the activation of the vascular system in the compressed periodontal ligament (PDL) is an indispensable process in tissue remodeling. We hypothesized that compressive force would induce angiogenesis of PDL through the production of vascular endothelial growth factor (VEGF). We examined the localization of VEGF in rat periodontal tissues during experimental tooth movement in vivo, and the effects of continuous compressive force on VEGF production and angiogenic activity in human PDL cells in vitro. PDL cells adjacent to hyalinized tissue and alveolar bone on the compressive side showed marked VEGF immunoreactivity. VEGF mRNA expression and production in PDL cells increased, and conditioned medium stimulated tube formation. These results indicate that continuous compressive force enhances VEGF production and angiogenic activity in PDL cells, which may contribute to periodontal remodeling, including angiogenesis, during orthodontic tooth movement.

The levels of vascular endothelial growth factor-A and placental growth factor-2 in embryopathy associated with experimental diabetic gestation

The objective of this study was to investigate the role of vascular endothelial growth factor-A (VEGF-A) and placental growth factor-2 (PlGF-2) in fetal malformations associated with maternal diabetes. Diabetes was induced in female rats. Diabetic and control female rats were made pregnant. On Day 15 of gestation, rats were sacrificed and embryos and their placentas and membranes were dissected out of the uterine horns. Following morphological examination, embryos and their placentas and membranes were homogenized and used for assayed of VEGF-A and PlGF-2 levels. Embryos of diabetic mothers, exhibited significantly (P < 0.05) shorter crown-to-rump lengths, smaller weights, and heavier placental weights. Experimentally induced maternal diabetes was accompanied by decreased VEGF-A in embryos and associated structures. The levels of PlGF-2 in non-malformed embryos of diabetic gestation and their placentas were significantly (P < 0.05) lower than the average of controls. These results might indicate defective vascularization with a consequent morphological or anatomical anomalies or more subtle biochemical or metabolic changes. In diabetic mothers, a statistically significant (P < 0.05) decrease was noted in the level of VEGF-A in plasma of diabetic rats with a small non-significant decrease in PlGF-2. Like many other diabetic complications, diabetes-induced embryopathies might have vascular origin and correcting the disturbances in these angiogenic factors might help decrease the incidence of malformation in diabetic gestation.

Effect of impaired glucose tolerance during pregnancy on the expression of VEGF receptors in human placenta

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) receptors VEGFR-1, VEGFR-2 and VEGFR-3 in placentas from pregnancies complicated by altered glycaemia. Placentas from women with physiological pregnancies (Group 1), pregnancies complicated by minor degree of glucose intolerance (MDGI, Group 2) and by gestational diabetes mellitus (GDM) treated with insulin (Group 3) were collected. Immunohistochemistry, RT-PCR and western blot were employed to evaluate receptor expression. In the three study groups, VEGFR-1 immunoreactivity was detected in all the placental components. VEGFR-2 immunoreactivity was observed in the vessels of all the placentas from Groups 1 and 2, but only in some placentas of Group 3. VEGFR-3 reactivity was observed in all the components of Group 1; in Groups 2 and 3 reactivity was observed in some portions of the trophoblast or the whole trophoblast, and in the stroma. VEGFR-1 and VEGFR-2 mRNA levels in Groups 2 and 3 were significantly higher compared with Group 1, whereas those of VEGFR-3 were significantly lower. Receptor protein levels were significantly lower in Groups 2 and 3 compared with Group 1. These findings demonstrated dysregulation of expression of the three placental receptors, both in GDM and in MDGI.

Preeclampsia and small-for-gestational age are associated with decreased concentrations of a factor involved in angiogenesis: soluble Tie-2

OBJECTIVE

An anti-angiogenic state has been described in patients with preeclampsia, small-for-gestational age (SGA) fetuses and fetal death, and changes in the concentration of circulating angiogenic and anti-angiogenic factors can precede the clinical recognition of preeclampsia and SGA by several weeks. Gene deletion studies demonstrate that a selective group of endothelial growth factors are required for vascular development, including members of the vascular endothelial growth factor (VEGF) family, as well as angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), both ligands for the tyrosine kinase endothelial cell receptor Tie-2. These angiogenic factors have been proposed to promote angiogenesis in a coordinated and complementary fashion. Soluble Tie-2 (sTie-2) is the soluble form of the Tie-2 receptor, which is detectable in biological fluids. The purpose of this study was to determine whether patients with preeclampsia and mothers who deliver a SGA neonate have changes in the plasma concentrations of sTie-2.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) non-pregnant women (n = 40), (2) women with normal pregnancies (n = 135), (3) patients with preeclampsia (n = 112), and (4) patients who delivered an SGA neonate (n = 53). Maternal plasma concentrations of sTie-2 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median maternal plasma concentration of sTie-2 was lower in normal pregnant women than in non-pregnant women [median 16.0 ng/mL (range 5.0-71.6) vs. median 20.7 ng/mL (range 10.8-52.4), respectively; p = 0.01)). (2) Plasma sTie-2 concentrations in normal pregnancy changed significantly as a function of gestational age. (3) Patients with preeclampsia and those who delivered SGA neonates had a lower median maternal plasma concentration of sTie-2 than those with a normal pregnancy [preeclampsia: median 14.9 ng/mL (range 4.9-67.3); SGA: median 10.9 ng/mL (range 5.1-29.1); normal pregnancy: median 16.0 ng/mL (range 5.0-71.6); p = 0.048 and p < 0.001, respectively]. (4) Patients with SGA neonates had a lower median plasma concentration of sTie-2 than that of those with preeclampsia [median 10.9 ng/mL (range 5.1-29.1) vs. median 14.9 ng/mL (range 4.9-67.3), respectively; p < 0.001]. (5) Patients with early-onset preeclampsia (<or=34 weeks) had lower concentrations of sTie-2 than women with late-onset preeclampsia (>34 weeks) median of delta values: -0.13 ng/mL (range -0.47-0.58) vs. median of delta values: -0.09 ng/mL (range: -0.60-0.58), respectively; p = 0.043]. In contrast, there were no significant differences in the maternal plasma sTie-2 concentration between women with severe and mild preeclampsia (p = 0.6).

CONCLUSION

Patients with preeclampsia and those with SGA fetuses have lower median plasma concentrations of soluble Tie-2 than women with normal pregnancies.

An Angiopoietin-2 gene polymorphism in unexplained intrauterine fetal death: a multi-center study

OBJECTIVE

Angiopoietin-2 (Ang-2) is a potent regulator of angiogenesis and vascular tone. As vascular processes have been proposed to be involved in the pathogenesis of pregnancy associated complications such as late unexplained intrauterine fetal death (IUFD), we determined whether a common G/A polymorphism of the Ang-2 gene (ANGPT2) is associated with this condition.

METHODS

In a multicenter case-control study, we evaluated the common G/A polymorphism within exon 4 of the ANGPT2 gene using PCR in 90 women with IUFD and 90 healthy women with at least one uncomplicated full term pregnancy and no history of IUFD.

RESULTS

Genotype (p=0.2; OR=1.4 [0.8-2.6]) and allele frequencies (p=0.1; OR=1.4 [0.9-2.1]) of the ANGPT2 polymorphism did not differ between women with IUFD and healthy women. A multivariate regression analysis with smoking habits and preexisting diabetes as covariates did not change the results.

CONCLUSIONS

We are the first to report on a common polymorphism of the ANGPT2 gene in patients with late IUFD. The investigated ANGPT2 poylmorphism does not seem to be a candidate gene for IUFD in Caucasian women.