Angiogenesis and the expression of vascular endothelial growth factor in endometrium and placenta

Vascular effects of estrogen and progestins and risk of coronary artery disease: importance of timing of estrogen treatment

The effects of estrogen and progestins on the vascular wall have drawn major medical attention, and significant controversy over various studies has been developed. Several experimental and observational studies have shown cardioprotective effects; however, prospective randomized trials showed an increase in cardiovascular events in postmenopausal women on estrogen/ medroxyprogesterone acetate treatment. The most significant parameter for cardiovascular benefit of estrogen seems to be the interval since the onset of menopause. In the early postmenopausal years, estrogen has beneficial effects on the vascular wall by inhibition of atherosclerosis progression, whereas in the late postmenopause, adverse effects like upregulation of the plaque inflammatory processes and plaque instability may develop. The effects of progestins on the cardiovascular system are not as clear and may differ according to the choice of progestins that is used. The aim of this review is to summarize the effects of estrogen and progestins on the vascular wall and their clinical implications.

Expression of vascular endothelial growth factor and assessment of microvascular density with CD 34 and endoglin in proliferative endometrium, endometrial hyperplasia, and endometrial carcinoma

The aim of this study was to compare vascular endothelial growth factor (VEGF), CD 34, and endoglin expressions as markers of angiogenesis in proliferative endometrium (PE), endometrial hyperplasia (EH), and endometrial carcinoma (EC) and to find the possible impact of angiogenesis on malign transformation. Formalin-fixed, paraffin-embedded tissues from 12 patients with PE, 23 patients with simple EH and complex EH with atypia, and 31 patients with EC were included. A semiquantitative scoring system was used to assess the intensity and degree of staining of VEGF. Microvessel density (MVD) was assessed with endoglin and anti-CD 34 in most vascular areas. VEGF expression was significantly higher in EC and EH than PE, but there was no difference between EC and EH. According to CD 34 staining, there were no differences in MVD between groups. However, mean MVD counts assessed by endoglin were significantly higher in EC than PE and EH. Although VEGF expression in EC was significantly higher, it did not correlate with other measures of angiogenesis. MVD using endoglin seemed to reflect neoplastic angiogenesis better than CD 34

Vasculogenesis and angiogenesis in the early human placenta

Vasculogenesis and angiogenesis are two consecutive processes during blood vessel development in the human placenta. While vasculogenesis, which is the formation of first blood vessels, is achieved by differentiation of pluripotent mesenchymal cells into haemangiogenic stem cells. The subsequent step, angiogenesis, is characterized by development of new vessels from already existing vessels. In this review, we aim to give an overview of vasculogenesis and angiogenesis during the first trimester of human placental development. Recent studies have shown that at the very early stages of placental development, cytotrophoblasts trigger vasculogenesis and angiogenesis, whereas as pregnancy progresses Hofbauer and stromal cells take over the task of triggering blood vessel development. Important growth factors in this scenario are the vascular endothelial growth factor (VEGF) family and their receptors, as well as Tie-1 and Tie-2. This review depicts the molecular and morphological steps of vasculogenesis and angiogenesis, which can give further insights into human placental development and maturation disorders.

Quantitative cellular and molecular analysis of the effect of progesterone withdrawal in a murine model of decidualization

The endometrium is a dynamic tissue that undergoes periodic growth, remodeling and breakdown under the influence of ovarian steroid hormones. To investigate the molecular mechanisms underlying these processes, we used a murine model to mimic the decidualization and regression observed in humans. Ovariectomized mice were treated sequentially with steroid hormones, and subsequently, to induce decidualization, oil was injected into the uterine lumen. The animals were then divided into progesterone-maintained and progesterone-withdrawal groups. In the latter group, a process similar to menstruation was induced. The uterine tissues were collected at several time-points after the induction of decidualization. Histological analysis demonstrated that decidualization and tissue degeneration were successfully induced with similar features to those observed during the human menstrual cycle. Immunohistochemical, morphometric, and microarray-based techniques were used to study the cellular and molecular changes. The volume fractions of leukocytes, macrophages, and neutrophils, but not endothelial cells, increased in decidualized uteri and decreased after major tissue degradation was completed. The microarray data show that the levels of many transcripts that encode immune-related factors changed during the time-course used for this model, and the transcript levels of many of these factors paralleled the changes observed in the volume fractions of the immune cells. The results of the present study suggest that this model is a useful alternative to the use of non-human primates. Our findings also show that immune cells are recruited into the menstruating endometrium, and that immune-related genes are regulated in the uterus throughout menstruation.

Concentration of circulating endothelial progenitor cells (EPC) in normal pregnancy and in pregnant women with diabetes and hypertension

OBJECTIVE

The aim of the present study was to analyze the concentrations of endothelial precursor cells (EPCs) during the 3 trimesters of normal pregnancy and to compare the EPC counts in women with normal pregnancy, gestational diabetes, and gestational hypertension.

STUDY DESIGN

The study was conducted on 21 pregnant women with single pregnancies (age range, 22 to 35 years). EPCs were quantified by flow cytometry. The subjects were divided into 3 groups, each consisting of 7 subjects: patients with gestational diabetes; patients with gestational hypertension; patients with normal pregnancy.

RESULTS

A progressive increase was found in the concentrations of EPCs during pregnancy in healthy women. In the third trimester of pregnancy, the number of CD34+ cells was significantly lower in patients with gestational diabetes than in hypertensive patients and controls; no significant differences were found between the levels of circulating CD34+ cells in hypertensive patients and those in controls. There were no significant differences between the diabetic and hypertensive patients for the percentage of cells expressing CD133 and VEGFR2, whereas in both groups the percentage of CD133+/VEGFR2+ elements was significantly higher than in the healthy control subjects.

CONCLUSION

Our findings confirm that EPCs isolated from the maternal circulation increase gradually throughout the gestational trimesters. These cells were derived from the endothelial cells lineage, as demonstrated by CD133+/VEGFR2+ cell assay. Moreover, the concentration of EPCs in pregnant women with gestational diabetes and hypertension differs from that in subjects with a normal pregnancy, CD34+ cells being reduced but CD133+/VEGFR2+ cell concentrations being increased. These results not only substantiate recent insights into the mechanisms regulating maternal vascular modifications during pregnancy but also throw light upon the activation of different patterns in the mobilization of endothelial progenitor cells during pathologic states in which endothelial disorders occur.

Expression of vascular endothelial growth factor receptor types 1, 2 and 3 in placenta from pregnancies complicated by hypertensive disorders

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) family receptors (VEGFR) in placentas from pregnancies complicated by hypertensive disorders of different clinical severity. Placental tissue from women with gestational hypertension, pre-eclampsia, pre-eclampsia with haemolysis, elevated liver enzymes and low platelets (HELLP syndrome) and normotensive women, as a control group, was examined. Immunohistochemical techniques, reverse transcription–polymerase chain reaction and western blot were used to evaluate receptor expression. In cases with gestational hypertension, as well as in control cases, VEGFR-1 and VEGFR-3 immunoreactivity was detected in all placental components, whereas in placentas from the pre-eclampsia and pre-eclampsia with HELLP syndrome groups, VEGFR-1 and VEGFR-3 immunoreactivity was detected only in some portions of trophoblast and/or some vessels and/or clusters of stromal cells. In the control group, VEGFR-2 immunoreactivity was observed only in the vessels, whereas the hypertensive groups showed VEGF-2 immunoreactivity also in trophoblast and stromal cells. The mRNA levels of the three receptors in the group with gestational hypertension were higher with respect to those in the control group. Placentas from pregnancies with pre-eclampsia showed lowest mRNA expression levels, whereas placentas from women with pre-eclampsia plus HELLP syndrome showed higher mRNA expression levels with respect to the three other groups. Receptor protein levels were lower in pathological cases compared with levles in the control group. These findings demonstrate a dysregulation of placental expression of VEGF family receptors related to the degree of clinical severity of the hypertensive disorder.

Three-dimensional ultrasound assessment of endometrial receptivity: a review

Three-dimensional ultrasound (3D US) is a new imaging modality, which is being introduced into clinical practice. Although this technique will not probably replace two-dimensional ultrasound, it is being increasingly used. It has been reported that 3D US is a very high reproducible technique. The endometrium has been paid special attention when using this technique. The aim of this paper is to address some technical aspects of 3D US and to review critically its current status in evaluating endometrial function with special focus in its role in predicting pregnancy in assisted reproductive techniques. In spontaneous cycles endometrial volume grows during follicular phase remaining constant through the luteal phase. Endometrial vascularization increases during follicular phase peaking 2-3 days before ovulation, decreasing thereafter and increasing again during mid and late luteal phase. Data from studies analysing the role of 3D US for predicting IVF outcome are controversial. An explanation for these controversial findings might be different design of reported studies, specially the timing of ultrasound evaluation.

Photonic Monitoring in Real Time of Vascular Endothelial Growth Factor Receptor 2 Gene Expression under Relaxin-Induced Conditions in a Novel Murine Wound Model

Relaxin is known to promote vascular endothelial growth factor (VEGF) expression in reproductive tissue, and successful wound healing depends on good vascularization of wound sites, a process that relaxin may facilitate. Thus, the objective of this study was to evaluate the efficacy of relaxin on the development of vascular tissue at wound sites in a novel VEGF receptor 2-luc (VEGFR2-luc) transgenic mouse wound model by monitoring the rate of VEGFR2-luc-mediated gene expression using bioluminescence and real-time imaging. To this end, 12 FVB/N VEGFR2-luc transgenic male mice were assigned to treatments (six per group): saline alone or relaxin (1 g/6 h/14 days) administered intraperitoneally (i.p.). On day 0, a set of full-thickness wounds (6-mm punch) were generated under anesthesia on the dorsal aspect of each mouse. Photonic emissions were recorded (5-min collection of photons) from wound sites 10 min after the administration of luciferin (150 mg/kg i.p.) on day 0 and on days 1, 2, 4, 7, 9, 11, and 14 postwounding to quantify luciferase activity using an IVIS 100 biophotonic imaging system. Animals were sacrificed (three per group) on day 7 or 14, and wound tissue specimens were recovered for molecular and histologic analyses. Although photonic emission from wound sites increased (P < .001) over time with peak values obtained by day 7, no significant (P > .05) effect of relaxin treatment on VEGFR2-luc gene expression was noted at wound sites. Whereas measuring relaxin's effect on angiogenesis indirectly via the VEGFR2 model was not successful, photonic imaging provides an exciting new tool using alternative models (i.e., VEGF-luc mouse) to study relaxin-induced gene expression in normal (i.e., wound healing) or tumorigenic tissues in real time.

Recent advances in endometrial angiogenesis research

This review summarises recent research into the mechanisms and regulation of endometrial angiogenesis. Understanding of when and by what mechanisms angiogenesis occurs during the menstrual cycle is limited, as is knowledge of how it is regulated. Significant endometrial endothelial cell proliferation occurs at all stages of the menstrual cycle in humans, unlike most animal models where a more precise spatial relationship exists between endothelial cell proliferation and circulating levels of oestrogen and progesterone. Recent stereological data has identified vessel elongation as a major endometrial angiogenic mechanism in the mid-late proliferative phase of the cycle. In contrast, the mechanisms that contribute to post-menstrual repair and secretory phase remodelling have not yet been determined. Both oestrogen and progesterone/progestins appear to have paradoxical actions, with recent studies showing that under different circumstances both can promote as well as inhibit endometrial angiogenesis. The relative contribution of direct versus indirect effects of these hormones on the vasculature may help to explain their pro- or anti-angiogenic activities. Recent work has also identified the hormone relaxin as a player in the regulation of endometrial angiogenesis. While vascular endothelial growth factor (VEGF) is fundamental to endometrial angiogenesis, details of how and when different endometrial cell types produce VEGF, and how production and activity is controlled by oestrogen and progesterone, remains to be elucidated. Evidence is emerging that the different splice variants of VEGF play a major role in regulating endometrial angiogenesis at a local level. Intravascular neutrophils containing VEGF have been identified as having a role in stimulating endometrial angiogenesis, although other currently unidentified mechanisms must also exist. Future studies to clarify how endometrial angiogenesis is regulated in the human, as well as in relevant animal models, will be important for a better understanding of diseases such as breakthrough bleeding, menorrhagia, endometriosis and endometrial cancer.

The effect of epidermal growth factor on production of vascular endothelial growth factor by amnion-derived (WISH) cells

Our objective was to clarify the physiological role of vascular endothelial growth factor (VEGF) by amnion-derived (WISH) cells. WISH cells were cultured, and the effect of epidermal growth factor (EGF), mitogen-activated protein (MAP) kinase kinase or extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitors (U0126) or phosphatidylinositol (PI) 3-kinase on the production of VEGF was examined. VEGF was assayed by ELISA. The activation of MAP kinase and akt, which is phosphorylated by PI 3-kinase, were detected by Western blot analysis using anti-phosphorylated MAP kinase antibody and anti-phosphorylated akt antibody. In the time course of VEGF production following EGF treatment, VEGF production showed a significant increase only after 16 (p < 0.01)-32h (p < 0.01). EGF increased the production of VEGF by WISH cells in a dose-dependent manner. The MAP kinase and akt activity were determined by treatment with EGF. VEGF production was significantly decreased following pretreatment with U0126 or wortmannin for two hours before treatment with EGF (p < 0.01, p < 0.01). WISH cells appeared to produce VEGF via a mechanism involving tyrosine kinase activation of EGF receptor and MAP kinase or PI 3-kinase. It is suggested that VEGF may contribute to the neovascularization and proliferation of the placenta and gestational tissue, and EGF may play an important role in regulation of VEGF production in the placenta.

Cyclooxygenase-2 inhibitors decrease vascular endothelial growth factor expression in colon cancer cells by enhanced degradation of Sp1 and Sp4 proteins

Cyclooxygenase 2 (COX-2) inhibitors, such as celecoxib (Cel), nimesulfide (NM), and NS-398 [NS; N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulfonamide] and other nonsteroidal anti-inflammatory drugs inhibit colon cancer growth and angiogenesis; however, the mechanism of this response is not well defined. Treatment of SW-480 colon cancer cells with Cel, NS, or NM decreased vascular endothelial growth factor (VEGF) mRNA and immunoreactive protein expression. This was also accompanied by decreased transactivation in cells transfected with constructs containing VEGF gene promoter inserts. Deletion analysis of the VEGF promoter indicated that decreased VEGF expression by COX-2 inhibitors was associated with the proximal -131 to -47 GC-rich region of the VEGF promoter that binds Sp proteins. Treatment of SW-480 cells with Cel, NM, and NS also decreased Sp1 and Sp4 protein expression but not that of Sp2 or Sp3. Similar results were observed in RKO, HT-29, and DLD colon cancer cells demonstrating comparable responses in COX-2-expressing and -nonexpressing colon cancer cell lines. COX-2 inhibitors do not affect Sp1 or Sp4 mRNA levels in SW-480 cells; however, decreased expression of both proteins was accompanied by increased protein ubiquitination and inhibited by the proteasome inhibitor gliotoxin. These results suggest that the antiangiogenic activity of COX-2 inhibitors in colon cancer cells is linked to activation of proteasome-dependent degradation of Sp1 and Sp4 proteins.

Endometrial Angiogenesis: From Physiology to Pathology

Numerous factors have been implicated in angiogenesis. This article concentrates on the expression of the major angiogenic factors, namely, vascular endothelial growth factor (VEGF) and the angiopoietins in the human endometrium. Particular emphasis is placed on the expression of the angiopoietins and their physiological and pathological expression.

Modulation of vascular endothelial growth factor and thymidine phosphorylase in normal human endometrial stromal cells

OBJECTIVE

To study the regulation of vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP), two angiogenic factors, in cultured endometrial stromal cells. The effects of steroids, E2, and P, the gonadotropin, hCG, and hypoxia were investigated.

DESIGN

Quantitative experimental study.

SETTING

Academic medical department.

PATIENT(S)

Women undergoing hysterectomy for benign causes.

INTERVENTION(S)

Endometrial cells were collected from subjects and cultured.

MAIN OUTCOME MEASURE(S)

The secretion of VEGF in supernatant media and the numbers of cells expressing VEGF or TP.

RESULT(S)

Estradiol increased VEGF secretion and the number of cells that contained VEGF and TP, and those effects were inhibited by hCG. Human chorionic gonadotropin alone could increase number of cells that expressed VEGF and TP. Hypoxia increased both VEGF secretion and number of cells containing VEGF and TP. Progesterone had no observed effect on VEGF secretion or number of VEGF- or TP-containing cells.

CONCLUSION(S)

Vascular endothelial growth factor and TP are present in stromal cells of normal endometrium, and E2 may interact with gonadotropins to regulate angiogenic compounds to modulate stromal functioning.

Implantation and Pregnancy Following In Vitro Fertilization and the Effect of Recombinant Human Relaxin Administration in Macaca fascicularis1

Implantation and early pregnancy, and the potential effects of the reproductive-hormone relaxin, were examined in the cynomolgus macaque (Macaca fascicularis) following in vitro fertilization and embryo transfer. Mature oocytes were collected from regularly cycling, female cynomolgus monkeys subjected to ovarian superovulation using recombinant human FSH and hCG. Oocytes fertilized in vitro were cultured to the 4- to 8-cell stage, slow-cooled, and stored in liquid nitrogen before thawing and embryo transfer. Regularly cycling recipients were administered recombinant human relaxin or vehicle for 21 days through the peri-implantation period (Day 0 = pump implantation), during which time the thawed embryos were transferred (Day 7). Endometrial thickness and the number of gestational sacs were monitored by ultrasound at three time points (Days 7, 21, and 28). The number of days of placental sign (implantation bleeding) in pregnant females and menses in nonpregnant females were also recorded. Implantation (gestational sacs/embryo transferred) and multiple pregnancy (multiple gestations/ pregnant recipient) rates were slightly higher in relaxin-treated recipients compared to vehicle-treated recipients. Administration of relaxin was associated with increased implantation bleeding in pregnant females. Endometrial thickness was increased in relaxin-treated recipients at Days 7 and 28 compared to Day 0, but these differences were not observed at the same time points in vehicle-treated females. Systemic administration of recombinant human relaxin in an in vitro fertilization/embryo transfer setting was associated with effects consistent with a role for this hormone in endometrial physiology in primates.

The effect of insulin-like growth factor-I on production of vascular endothelial growth factor by amnion-derived (WISH) cells

OBJECTIVE

Our objective was to clarify the modulation of vascular endothelial growth factor (VEGF) by amniotic cells.

DESIGN

Amnion-derived (WISH) cells were cultured, and the effect of insulin-like growth factor (IGF), mitogen-activated protein (MAP) kinase kinase and/or extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitors (U0126), and phosphatidylinositol (PI) 3-kinase inhibitors (wortmannin) on the production of VEGF was examined. VEGF was assayed using ELISA. The activations of MAP kinase and akt, which is phosphorylated by PI 3-kinase, were detected by Western blot analysis using anti-phosphorylated MAP kinase antibody and anti-phosphorylated akt antibody.

RESULTS

In the time course of VEGF production following IGF-I treatment, VEGF production showed significant increases only at 16 and 32 h (p < 0.01). Also, IGF-I increased the production of VEGF by WISH cells in a dose-dependent manner. The MAP kinase and akt activities were recognized by treatment with IGF-I and suppressed by U0126 and wortmannin, respectively. When WISH cells were pretreated for 2 h with U0126 and wortmannin and then treated with IGF-I for 16 h, the production of VEGF was significantly decreased in a dose-dependent manner (p < 0.01, p < 0.01, respectively).

CONCLUSIONS

WISH cells appeared to produce VEGF via a mechanism involving tyrosine kinase interaction with IGF-I receptor, resulting in MAP kinase and PI 3-kinase activation. It is suggested that VEGF may contribute to the neovascularization and proliferation of the placenta and gestational tissue, and IGF-I may play an important role in the modulation of VEGF production in the placenta.

Soluble vascular endothelial growth factor receptor-1 (sFlt-1) is increased throughout gestation in patients who have preeclampsia develop

OBJECTIVE

This study was undertaken to analyze prospectively circulating vascular endothelial growth factor (VEGF) and its soluble receptor, (s) Flt-1, throughout normotensive and preeclamptic pregnancies and to assess the importance of these proteins in the development of preeclampsia.

STUDY DESIGN

In this longitudinal cohort study, serum samples were collected from recruited subjects throughout pregnancy at 12, 20, 30, and 37 weeks and in the 24 hours before and after delivery. Subjects were divided retrospectively into normotensive and preeclamptic groups. Circulating VEGF and sFlt-1 concentrations were analyzed by radioimmunoassay and enzyme-linked immunosorbent assay, respectively.

RESULTS

Circulating sFlt-1 and VEGF significantly increased as gestation progressed and both were further elevated in preeclampsia compared with normotensive pregnancy. Soluble Flt-1 concentrations were elevated early in gestation and were significantly increased at 30 weeks' gestation in those who subsequently developed preeclampsia.

CONCLUSION

These results indicate a definite association between elevated sFlt-1 concentrations and the onset of preeclampsia suggesting that sFlt-1 is linked with disease pathogenesis.

Expression of IGR-IR and VEGF and trophoblastic proliferative activity in placentas from pregnancies complicated by IUGR

Intrauterine growth retardation (IUGR) is recognized as an important cause of low birth weight and elective preterm delivery. IUGR is associated with multiple causative factors, including placental dysfunction. The aim of this prospective study was to investigate the role of trophoblastic proliferative activity and type I insuline-like growth factor receptor (IGF-IR) and vascular endothelial growth factor (VEGF) expressions in the pathogenesis of IUGR. Immunohistochemistry using VEGF, IGF-IR, and Ki-67 antibodies was performed on formalin-fixed placental tissues of third-trimester pregnancies complicated by IUGR (n = 19) and pregnancies with appropriately grown fetuses (n = 27). In addition, histopathological examination of the placentas was performed, and histological findings were categorized into three groups: utero-placental vascular pathologies (UPVP), coagulation-related pathologies, and chronic inflammation. Statistical analysis revealed that villous trophoblastic IGF-IR immunostaining was significantly weaker in placentas with IUGR (p < 0.001), whereas trophoblastic Ki-67 proliferative index and VEGF immunoscoring did not show any significant difference. Histologically, UPVP and chronic inflammation were significant findings in placentas with IUGR (p = 0.04 and p = 0.04, respectively). In addition, placentas were significantly smaller in the IUGR group (p < 0.001). We conclude that villous trophoblastic IGF-IR expression may play a significant role in the pathogenesis of IUGR, and histopathological examination of placentas in pregnancies complicated by IUGR may yield significant findings. In contrast, based on our findings, trophoblastic proliferation and VEGF expression are unlikely to be significant parameters in the pathogenesis of IUGR.

Hypoxia simultaneously inhibits endostatin production and stimulates vascular endothelial growth factor production by cultured human endometrial stromal cells

Hypoxia downregulated the concentration of endostatin in the culture media of human endometrial stromal cells but did not affect the messenger (m)RNA expression of collagen XVIII. Both mRNA and protein expression of vascular endothelial growth factor were upregulated in a hypoxic condition.

Intravascular neutrophils partially mediate the endometrial endothelial cell proliferative response to oestrogen in ovariectomised mice

The aim of this study was to investigate the role of intravascular neutrophils in initiating endothelial cell proliferation following oestrogen treatment in ovariectomised mouse endometrium. Uterine tissues were collected from ovariectomised C57/CBA female mice 24 h after oestrogen treatment with or without systemic neutrophil depletion. Neutropenia was achieved with either an in-house anti-neutrophil serum (ANS) or Gr-1 monoclonal antibody. All mice received an i.p. injection of bromodeoxyuridine (BrdU) 4 h prior to dissection to allow visualisation of proliferating cells using immunocytochemistry. Endometrial sections were immunostained for BrdU, vascular endothelial growth factor (VEGF), and neutrophils (using ANS). Oestrogen treatment of ovariectomised mice significantly increased the number of intravascular neutrophils, whereas induction of neutropenia with either ANS or Gr-1 in conjunction with oestrogen treatment prevented this increase. Oestrogen treatment of ovariectomised mice also significantly increased the number of intravascular VEGF-positive cells; however, whereas induction of neutropenia with ANS significantly reduced this increase, Gr-1 did not. In both studies, neutropenia significantly reduced, but did not eliminate, the amount of endometrial endothelial cell proliferation. These results suggest a role for neutrophils in endometrial angiogenesis following acute oestrogen treatment; however, the presence of VEGF-positive cells even after induction of neutropenia suggests that more than one type of leukocyte may be involved.

Endometrial angiopoietin expression and modulation by thrombin and steroid hormones: a mechanism for abnormal angiogenesis following long-term progestin-only contraception

The angiopoietins (Ang) are endothelial cell-related factors necessary for the development and maintenance of all vessels. Altering the expression of these proteins would be expected to result in aberrant angiogenesis. Indeed the fragile endometrial vasculature and bleeding observed in women treated with long-term progestin-only contraceptives has been associated with changes in the expression of Ang-1 and Ang-2. Since bleeding would result in thrombin formation, we have assessed the effects of thrombin on the expression of the Angs in human endometrial cells. This study shows that thrombin significantly reduces the expression of Ang-1 protein and mRNA expression in human endometrial stromal cells (HESCs) and minimally decreases the production of Ang-2 protein in human endometrial endothelial cells (HEECs). Hence the presence of thrombin due to aberrant bleeding could affect the angiogenic potential of the endometrium, creating a feed forward loop resulting in more thrombin, weak vasculature, and more bleeding. In addition, since the exact localization of Ang in the human endometrium remains a subject of controversy, we have addressed this issue in an in vivo system by analyzing the expression of Angs by microdissection of HESCs, HEECs, and human endometrial glandular epithelial cells followed by real time, quantitative RT-PCR.

Biology of primate relaxin: a paracrine signal in early pregnancy?

Relaxin is a peptide hormone that exerts numerous effects in a variety of tissues across a broad range of species. Although first identified more than 75 years ago interest in relaxin biology has waxed and waned over the years consistent with peaks and troughs of new experimental data on its wide-ranging biological effects and advances in relaxin enabling technologies. Recent insights into species-dependent differences in relaxin biology during pregnancy have once again stimulated a relative surge of interest in the study of relaxin's reproductive biology. Identification and pharmacological characterization of orphaned relaxin receptors and exploration of its paracrine effects on pregnancy using genomic and proteomic technologies have succeeded in fueling current interest in relaxin research. Primates and non-primate vertebrates exhibit very disparate profiles of relaxin genomics, proteomics and functional biology. Non-human primates appear to exhibit a very close similarity to humans with respect to relaxin reproductive biology but the similarities and subtle differences are only just beginning to be understood. We, and others, have shown that relaxin produces significant changes to the non-human primate endometrium during the peri-implantation period that are consistent with relaxin's long perceived role as a paracrine modulator of pregnancy. The purpose of this review is to summarize the reproductive biology of relaxin in non-human primates with a specific emphasis on the paracrine role of ovarian and endometrial relaxin during embryo implantation and early pregnancy.

VEGF expression in the placenta from pregnancies complicated by hypertensive disorders

OBJECTIVE

To determine the expression of VEGF in the placental tissue from pregnancies complicated by hypertension disorders of different clinical severity.

DESIGN

Prospective cohort study.

SETTING

Polyclinic of Careggi, University of Florence, Italy.

SAMPLE

Placentas from women with gestational hypertension (n= 20), pre-eclampsia (n= 20) and pre-eclampsia with HELLP syndrome (n= 20) and from normotensive women (n= 20), as control group (gestational age comprised between 35 and 38 weeks).

METHODS

An immunohistochemical technique and a quantitative analysis to measure mRNA levels (RT-PCR) were employed.

MAIN OUTCOME MEASURES

Intensity of immunoreactivity and mRNA levels in the placental components. Differences between the data.

RESULTS

VEGF immunoreactivity was observable in all the placental components in the gestational hypertension cases as in the control ones. In the cases with pre-eclampsia and pre-eclampsia with HELLP syndrome, some placental components were not immunoreactive. However, the VEGF positive components of all the pathological groups showed a higher intensity of reactivity with respect to that of the control group. The levels of VEGF mRNA were higher in the gestational hypertension cases and lower in the cases of pre-eclampsia with HELLP syndrome with respect to the control ones; in the cases of pre-eclampsia, the levels were the same as the control ones.

CONCLUSION

The different expression of VEGF in the placenta of the pathological cases is probably related to haemodynamic changes that take place in these disorders, in order to attempt restoration of a normal uteroplacental flow.

Effect of tibolone and its metabolites on vascular endothelial growth factor isoforms 121 and 165 and thrombospondin-1 mRNA in Ishikawa cells

OBJECTIVE

To compare the mRNA expression of vascular endothelial growth factor (VEGF) 121 and 165 isoforms and thrombospondin-1 (TSP-1) after incubation with tibolone and tibolone metabolites 3alpha-hydroxytibolone, 3beta-hydroxytibolone, Delta4-tibolone, and 17beta-estradiol (E2) in cultured Ishikawa cells.

DESIGN

Ishikawa cells (immortalized from a well-differentiated human adenocarcinoma cell line) were cultured in vitro to confluence. Tibolone, 3alpha-hydroxytibolone, 3beta-hydroxytibolone, Delta4-tibolone and E2 at concentrations of 1.0, 0.1 and 0.01 micromol/L were added to confluent cells and further cultured for an additional 24 h. Control cells were treated with medium in absence of hormone. Total RNA was extracted from control and treated Ishikawa cells. After reverse transcription, VEGF, TSP-1 and the housekeeping gene, beta-actin cDNAs, were amplified in a polymerase chain reaction spiked with 33p-dCTP. Relative abundance of VEGF 121 and 165 isoforms and TSP-1 mRNA was measured by scintillation spectroscopy.

RESULTS

E2, tibolone, 3alpha-hydroxytibolone, and 3beta-hydroxytibolone increased both VEGF 121 and 165 mRNA compared with the control. However, Delta4-tibolone had no effect on either VEGF 121 or 165 mRNA compared with the control. Delta4-Tibolone increased TSP-1 mRNA expression compared with control levels. E2, tibolone, 3alpha-hydroxytibolone, and 3beta-hydroxytibolone did not increase TSP-1 mRNA expression at any concentration.

CONCLUSIONS

Tibolone and the 3alpha- and 3beta-tibolone metabolites with E2 increased VEGF 121 and 165 isoforms. Conversely, Delta4-tibolone, which is reported to have progestational-like activity, did not stimulate VEGF 121 and VEGF 165 but increased TSP-1 mRNA synthesis in cultured Ishikawa cells. We hypothesize, based on these data, that the clinical finding of no endometrial growth in women using tibolone may be partly related to alterations in these angiogenic factors.

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.

Changes in vascular endothelial growth factor production associated with decidualization by human endometrial stromal cells in vitro

BACKGROUND

The aim of this study was to clarify changes in the expression of vascular endothelial growth factor (VEGF) during decidualization by endometrial stromal cells (ESCs) in vitro.

METHODS

ESCs were separated by enzymic digestion and filtration, and were cultured with RPMI 1640 in 10% fetal calf serum (FCS) and treated with medroxyprogesterone acetate (MPA) and dibutyryl-cyclic adenosine monophosphate (db-cAMP) to induce decidualization in vitro. The levels of prolactin (PRL) in the culture media were measured by enzyme immunoassay (EIA) and the levels of VEGF were measured by enzyme-linked immunosorbent assay (ELISA). The expression of VEGF mRNA by ESCs and decidualized cells was analyzed by Northern blot analysis.

RESULTS

In treated cells, PRL production was significantly increased due to treatment with both db-cAMP (0.5 mmol/L) and MPA (100 nmol/L). VEGF mRNA expression was detected without any stimulation by ESCs. VEGF production was also significantly greater in cells treated with db-cAMP (0.5 mmol/L) and MPA (1 nmol/L or 100 nmol/L) than in control cells. VEGF mRNA was also increased in association with decidualization in vitro.

CONCLUSIONS

VEGF production increased in association with decidualization in this in vitro study. Decidualization of ESCs may play a role in the induction of growth in the human fetus and/or placentation. The mechanism involved may include influencing the production of angiogenic growth factors such as VEGF.

Progestin-regulated expression of tissue factor in decidual cells: implications in endometrial hemostasis, menstruation and angiogenesis

Expression of tissue factor (TF), the primary initiator of hemostasis via thrombin formation, is induced during progesterone (P4)-stimulated decidualization of human endometrial stromal cells (HESCs), and remains elevated in decidualized HESCs of luteal and gestational endometrium. In HESC monolayers, progestins elevate TF mRNA and protein levels and estradiol (E2) plus progestin further enhance TF levels for weeks despite no response to E2 alone. This in vitro model mimics the chronic differential ovarian steroid upregulation of TF levels associated with in vivo decidualization. After incubation of HESCs with E2 plus progestin to elevate TF expression, the antiprogestin RU486 completely reversed this upregulation. Thus, progesterone withdrawal transformed decidualization-associated hemostasis of the luteal phase endometrium to the hemorrhagic milieu of menstruation. Transient transfections with TF promoter constructs containing SP and EGR-1 binding sites before and after inactivation by site-directed mutagenesis revealed that Sp1 mediates basal and progestin-enhanced TF transcriptional activity. Progesterone receptor involvement in TF expression was further confirmed since RU486 was a pure antagonist of progestin-enhanced TF mRNA and protein expression, and progestin-enhanced, but not basal, Sp1-mediated transcriptional activity. Enhanced TF mRNA and protein levels in HESCs require co-incubation with progestin and epidermal growth factor receptor (EGFR) agonist indicating that the EGFR mediates progestin-enhanced TF expression. A peak in the primary angiogenic agent, vascular endothelial growth factor (VEGF) in luteal phase endometrium may be indirectly regulated by P4. Neither E2, nor progestin, nor E2 plus progestin affected VEGF expression in glandular epithelial and stromal cells, whereas thrombin enhanced VEGF mRNA and protein levels in decidualized HESCs, but not in the epithelial cells. Transudation of clotting factors to perivascular decidual cell TF in the luteal phase would generate thrombin, enabling it to act as an autocrine enhancer of VEGF in decidualized HESCs. Abnormal uterine bleeding complicates long-term progestin only contraceptive use. After Norplant administration, endometrial VEGF levels are elevated and TF levels are selectively enhanced in decidualized HESCs at bleeding sites. Over-expressed VEGF causes blood vessels to become leaky, increasing clotting factor access to decidualized HESC-expressed TF to promote feed-forward thrombin and VEGF formation. Since thrombin and VEGF induce angiogenesis via separate endothelial cell receptors, they may synergize to elicit aberrant angiogenesis, and ultimately lead to focal bleeding.

Effect of p53 gene transfection on vascular endothelial growth factor expression in endometrial cancer cells

It has been reported that tumor suppressor gene p53 regulates vascular endothelial growth factor (VEGF) expression, but the relation between them in endometrial carcinoma remains unclear. We investigated VEGF expression in 11 endometrial carcinoma cell lines and the effect of p53 gene transfection on VEGF expression in the p53-mutated endometrial carcinoma cell line, HEC-50B. Immunoblotting for detecting VEGF, p53, and beta-actin was performed. Wild type p53 gene was transfected using the SuperFect method. The mean VEGF value of 0.8 +/- 0.3 (n = 6) in p53 wild-type group was significantly lower than the 1.6 +/- 0.8 (n = 5) that was found in the p53 mutant group (P < 0.05). Levels of VEGF in the culture medium were measured by enzyme immunoassay (EIA). VEGF levels in the p53 gene-transfected HEC-50B cells and the conditioned medium were decreased at 48 h after p53 gene transfection. VEGF expression was downregulated by p53 in endometrial carcinoma cells.

Effect of raloxifene, 17beta-estradiol, and progesterone on mRNA for vascular endothelial growth factor isoforms 121 and 165 and thrombospondin-1 in Ishikawa cells

OBJECTIVE

To compare the mRNA expression of vascular endothelial growth factor (VEGF) 121 and 165 isoforms and thrombospondin-1 (TSP-1) after raloxifene, 17beta-E(2), and P administration in cultured Ishikawa cells.

DESIGN

Prospective basic research study.

SETTING

Jones Institute for Reproductive Medicine, Eastern Virginia Medical School, Norfolk, Virginia.

PATIENT(S)

None.

INTERVENTION(S)

Ishikawa cells were cultured in vitro. Raloxifene, 17beta-E(2), and P at concentrations of 0.01, 0.1, and 1.0 microM were added to confluent cells.

MAIN OUTCOME MEASURES

The VEGF 121 and 165 isoforms and TSP-1 mRNA expression from treated Ishikawa cells were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULT(S)

17beta-Estradiol increased both VEGF 121 and 165 mRNA compared to control. Raloxifene did not increase either VEGF 121 or 165 mRNA above control values. Progesterone at all concentrations did not increase VEGF 121 isoform mRNA, whereas VEGF 165 isoform was minimally increased by P at the lowest concentration. Progesterone and raloxifene increased TSP-1 mRNA expression. 17beta-Estradiol did not stimulate TSP-1 mRNA expression at any concentration.

CONCLUSION(S)

Raloxifene did not stimulate VEGF 121 and 165, whereas it increased TSP-1 mRNA synthesis in Ishikawa cells. Our hypothesis is that raloxifene's lack of endometrial stimulation may be partly mediated by an antiangiogenic effect.

Pathophysiology of endometrial bleeding

OBJECTIVES

To review the morphological and molecular events responsible for uterine bleeding in health and disease.

METHODS

Review of pertinent literature focusing on the histology and pathophysiology of normal and abnormal uterine bleeding (AUB).

RESULTS

The seat of normal menstrual bleeding is located in the upper two-thirds of the endometrial mucosa and is recognized by tissue necrosis, disruption of microvasculature, migratory leukocytes and platelet/fibrin thrombi in microvessels. The molecular events responsible for tissue and vascular breakdown are related to the release of proteolytic lysosomal enzymes of endometrial cell and inflammatory cell origin. In cases of AUB, tissue breakdown is located in the superficial layer (subsurface) of the endometrium. It is either focal (breakthrough bleeding) or diffuse (withdrawal bleeding). It is initiated by either chronic endometritis and/or microerosions or vascular fragility due to structural abnormalities of microvessels. Endometritis and microerosions occur in otherwise normal endometrium, polyps, submucosal leiomyomata, atrophy and cancer (organic causes). Primary vascular alterations are found in hyperestrogenic-type endometria, i.e. anovulatory dysfunctional uterine bleeding (DUB) and progestational-type endometrium, i.e. progestational contraceptives and combined, continuous hormonal replacement therapy (HRT) (non-organic causes). Ovulatory DUB and coagulation disorders are not appreciated histologically. These are related to impaired vasoconstriction and fibrinolysis and impaired coagulation factors, respectively.

CONCLUSIONS

Histology may contribute to better understanding of the mechanisms of action that initiate, regulate and lead to AUB. Better insight may trigger in the development of therapeutic procedures that could either prevent or control vascular breakdown which results in unexpected uterine bleeding.

VEGF expression and its reguration by p53 gene transfection in endometrial carcinoma cells

Vascular endothelial growth factor (VEGF) that activates endothelial cell growth induces angiogenesis, which is indispensable to tumor igenesis and tumor progression. On the other hand, tumor suppressor gene p53 has been considered to regulate VEGF expression, but the detailed relationship between them remains unclear. In this study, we aimed to study VEGF expression in endometrial carcinoma cells and the effect of p53 gene transfection on VEGF expression using p53-mutated endometrial carcinoma cell line, HEC-50B. Immunoblotting for detecting VEGF protein, p53 protein and beta-actin was performed using 11 endometrial carcinoma cell lines. Levels of VEGF in the cultured media were measured by Enzyme immunoassay(EIA). Transfection of wild p53 gene was carried out by SuperFect method in HEC-50B cells, which had mutant p53 gene and did not express p53 protein. The results of immunoblotting were analyzed by NIH image and expressed as values. The results of EIA were expressed as the relative value. The VEGF value was 0.8 +/- 0.3 (n = 6) in p53-wild group, whereas in p53-mutant group it was 1.6 +/- 0.8 (n = 5). VEGF expression was correlated significantly with p53 status (P < 0.05). VEGF levels in p53 gene-transfected cells and the conditioned medium were decreased in 48 hours after p53 gene transfection. VEGF expression was down-regulated by p53 in endometrial carcinoma cells.

Effects of cytokines on VEGF expression and secretion by human first trimester trophoblast cell line

PROBLEM

The mechanism through which vascular endothelial growth factor (VEGF) regulation occurs at the feto-maternal interface is poorly understood. The aim of this study was to investigate the effects of various cytokines on VEGF expression and secretion by trophoblast cells.

METHOD OF STUDY

We investigated the effects of cytokines on VEGF expression in human first trimester trophoblast cell line by analyzing VEGF messenger RNA (mRNA) by reverse transcription-polymerase chain reaction and VEGF protein secretion by enzyme linked immunosorbent assay.

RESULTS

The trophoblast cells expressed VEGF mRNA constitutively and the main subtypes were identified as VEGF121 and VEGF165. When cultured in the presence of interferon (IFN)-gamma, interleukin (IL)- 1beta, tumor necrosis factor (TNF)-alpha, IL-2, or IL-10, VEGF mRNA expression was found to be significantly increased by IL-1beta, IFN-gamma and TNF-alpha but to be unaffected by IL-2 and IL-10. Moreover, VEGF secretion was most significantly increased by IFN-gamma treatment.

CONCLUSION

These results suggest that IL-1beta, IFN-gamma, and TNF-alpha may regulate the production of VEGF in early gestational trophoblasts.

Expression and localization of angiogenin in placenta: enhanced levels at term over first trimester villi

Human angiogenin, a 14-kDa non-glycosylated polypeptide with both angiogenic and ribonucleolytic activities, is implicated in angiogenesis, a complex process of proliferation and formation of new capillary blood vessels from existing blood vessels. Placental growth requires extensive angiogenesis, which develops its vascular structure in both fetal chorionic villi and maternal deciduas. In this study, we investigated the expression profiles of angiogenin in placental villi from early and late gestation at both mRNA and protein levels using explant cultures in vitro followed by RT-PCR, immunoblot, and immunohistochemical analyses. From functionally active placental explants, angiogenin was detected in conditioned media of all the samples from first trimester and term group. The mean levels of angiogenin produced by term villi were found to be 2.6-, 2.1-, and 2.2-fold higher (P < 0.01) than first trimester villi at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and first trimester villi seem to agree with its mRNA levels and immunoblot analysis; the expression in term villi was twice that in first trimester villi. The presence of angiogenin in placental villi and upregulation of its production towards term indicate that angiogenin production by the placenta is specific to the developmental stage. In conclusion, the observed changes in the localization and mRNA expression of angiogenin during placental development raise the possibility that it is involved in morphological and angiogenic changes in this endocrine organ vital to the successful fetal outcome during pregnancy.

Immunohistochemical analysis of alphavbeta5 and alphavbeta6 integrins in the endometrium and endometriosis

We performed a case-controlled study to study the immunoreactivity patterns and staining intensity of alphavbeta5 and alphavbeta6 integrins in ectopic and eutopic endometrium from women with endometriosis and compared them with those in normal control endometrium. Forty eutopic and ectopic samples from patients with endometriosis were compared with 12 control endometrial samples. Staining was evaluated using a computerized image analysis system by a blinded, independent observer. The immunoreactivity patterns for both alphavbeta5 and alphavbeta6 were very similar. In eutopic endometrium from women with or without endometriosis, the immunostaining intensity score for both integrins was stronger during the secretory than the proliferative phase. Immunoreactivity in endometriosis was greater than in eutopic endometrium. There were no significant menstrual cycle-related staining differences in endometriosis. The percentage of blood vessels immunolabeled was greater in endometriosis than eutopic endometrium from endometriosis patients and greater in eutopic endometrium from these patients compared with control endometrium. Ectopic tissue from patients with stages I and II endometriosis showed significantly higher staining intensity than ectopic tissue from patients with stages III and IV disease. Determination of the specific functional consequences of the differences observed in alphavbeta5 and alphavbeta6 integrin immunostaining may provide an increased understanding regarding the pathogenesis of endometriosis.

The three-dimensional feto-maternal vascular interrelationship during early bovine placental development: a scanning electron microscopical study

Both the fetal and maternal microvasculature of bovine placentomes was examined by scanning electron microscopy of vascular casts. So far the development of the vascular architecture of the bovine placentome in early gestation has only been studied 2-dimensionally due to technical difficulties arising from the fragility of the early placental blood vessels. Repeated experiments led to the selection of the microvascular corrosion casts presented here. The vasculature of the maternal compartment is supplied by large caruncular stalk or spiral arteries, which release short maternal stem arteries. In the 3rd month of gestation, these arteries branch into several arterioles at their base, thus providing the vascular framework for the lower part of the septal walls of the primary crypts. In the 4th month, due to progressive longitudinal growth of the stem arteries, branching into arterioles occurs not only at the base, but over the whole length of the stem arteries. These arterioles supply the capillary complexes of the septa which resemble the major part of the septal vasculature and face the secondary crypts. Further indentation results in the formation of tertiary crypt capillary complexes, encircling the earlier secondary unit. From the 6th month of gestation the architecture resembles the fully developed maternal placenta with stem arteries running directly to the fetal side to branch into 4 to 6 arterioles, which turn back to enter secondary and tertiary septa. Maternal venules, collecting the blood from the capillary bed of secondary and tertiary septa, converge onto stem veins leaving the caruncle via branches of the uterine vein. The fetal part of the placentome is supplied by the cotyledonary arteries, which branch into fetal stem arteries that are the tributary to single villous trees. Over their whole course towards the maternal side, these give off arterioles entering secondary villi. The tertiary or terminal villous vasculature consists of capillaries, which are organised in serial capillary loops. This system is progressively elaborated in the course of gestation. In the 4th month there are only finger-like loops, whereas from the 6th month large fan-like structures can be observed. In early gestation the maternal and fetal blood vessels meet predominantly in a countercurrent fashion, changing to the less efficient crosscurrent exchange when the tertiary unit develops. These results indicate the development of a highly elaborated fetomaternal villous-crypt exchange system, already established in the 1st half of gestation, thus meeting the increasing needs of the fetus.

Effects of the xenoestrogen bisphenol A on expression of vascular endothelial growth factor (VEGF) in the rat

Bisphenol-A (BPA) is used to produce polymers for production of polycarbonate and epoxy resins that are used in food containers and dental appliances. BPA binds to estrogen receptors and induces estrogenic activity in a number of biological systems. We recently reported that although Fisher 344 (F344) and Sprague-Dawley (S-D) rat strains exhibit different sensitivities to BPA at the level of vaginal epithelial cell proliferation, there was no difference in immediate early proto-oncogene expression between the two animal strains. In the present study we investigated the effects of BPA on expression of another estrogen-target gene, vascular endothelial growth factor (VEGF), in the uterus, vagina, and pituitary of F344 and S-D rats. Adult rats were ovariectomized and treated with BPA by intraperitoneal injection at concentrations of 0.02 to 150 mg/kg body wt. Expression of VEGF was monitored by RNase protection assay at 2 hr after treatment. There was a significant effect of dose of BPA on the type of VEGF isoform expressed in the uterus, vagina, and pituitary. BPA induced greater (P < 0.01) levels of VEGF164 and VEGF120+188 than VEGF110 levels. The lowest BPA dose that had a significant (P< 0.05) effect on VEGF expression compared with vehicle treatment was 37.5 mg/kg body wt.; dose-response curves did not differ between strains. This is the first report that the primary response of the uterus, vagina, and pituitary to BPA includes rapid induction of VEGF expression. Due to the capacity of VEGF to engage pleiotropic signaling pathways in other cellular systems, we suggest that modulation of VEFG may play a role in establishing the response of estrogen-target organs to estrogenic xenobiotics.

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.

Effects of roxithromycin on tumor necrosis factor-alpha-induced vascular endothelial growth factor expression in human periodontal ligament cells in culture

BACKGROUND

Aberrant angiogenesis is associated with lesion formation in chronic periodontitis. However, little is known about the mediators that contribute to angiogenesis or about therapeutic agents that control the production of the mediators. Roxithromycin (RXM), which is a new 14-member macrolide antibiotic, has a wide antibacterial spectrum against oral pathogens and an immunomodulatory effect. In the present study, we examined the effects of RXM on tumor necrosis factor (TNF)-alpha-induced vascular endothelial growth factor (VEGF) in human periodontal ligament (HPDL) cells. In addition, the effect of RXM on VEGF expression in HPDL cells was examined.

METHODS

HPDL cells were plated at 5 x 10(5) cells/ml in 150 cm2 cell culture dishes. The confluent-stage cells were pretreated with or without 10 microg/ml of RXM or other antibiotics in 1% FBS-containing alpha-MEM for 24 hours, followed by simultaneous treatment with 10 ng/ml of TNF-alpha and 10 microg/ml of these antibiotics. After incubation for various periods, the culture supernatants and sediments were collected and analyzed by ELISA, Northern blot, and gel shift assays.

RESULTS

VEGF mRNA and its protein were constitutively expressed in HPDL cells, and the level of expression was markedly enhanced by stimulation with TNF-alpha. RXM strongly inhibited the expression of VEGF mRNA and the production of VEGF. Furthermore, RXM suppressed activation of transcription factors AP-1 and SP-1, which were critical factors in VEGF transcription, in TNF-alpha-stimulated HPDL cells.

CONCLUSION

These results indicate that TNF-alpha, one of the proinflammatory cytokines implicated in the pathogenesis of periodontitis, induces excess induction of VEGF in HPDL, which may account for increased angiogenesis in periodontitis lesions. Interestingly, the antibiotic roxithromycin inhibits TNF-mediated VEGF induction, suggesting its possible therapeutic utility in periodontitis and other chronic inflammatory conditions involving VEGF induction.

Expression of angiopoietin-2 by human endometrial endothelial cells: regulation by hypoxia and inflammation

The functional endometrial layer receives the implanting blastocyst, but is sloughed off during menstruation. Angiogenesis regulates growth and repair of cycling human endometrium. While vascular endothelial growth factor initiates angiogenesis, the angiopoietins (Angs) acting via the Tie2 receptor, are key regulators of subsequent angiogenic steps. This study is the first to localize Ang-2 and Tie2 in human endometrium and to study Ang-2 regulation in cultured human endometrial endothelial cells (HEECs). Immunohistochemistry revealed that expression of Ang-2 and Tie2 was absent from the glands, low in stromal cells, and intense in the endothelial cells. In contrast, only weak expression of Ang-1 was detected. The phase of the menstrual cycle did not appear to affect the expression of Ang-2 or Tie2. In vitro studies were carried out utilizing isolated HEECs, the most relevant model for endometrial microvascular biology studies. Both hypoxia and phorbol-myristate-acetate enhanced Ang-2 mRNA levels in HEECs. These results suggest that Ang-2 plays a role in endometrial pathologies complicated by impaired blood flow and inflammation.

Uteroplacental blood flow and placental vascular endothelial growth factor in normotensive and pre-eclamptic pregnancy

OBJECTIVE

To determine whether placental vascular endothelial growth factor (VEGF) is increased in pre-eclampsia.

DESIGN

Prospective cohort study.

SETTING

Royal Prince Alfred Hospital, Sydney, Australia.

SAMPLE

Eleven normotensive women and eight women with pre-eclampsia matched for age and gestation.

METHODS

Uterine artery Doppler ultrasound flow velocity profiles were recorded in the third trimester and resistance index calculated as (Vs-Vd)/Vs (Vs = peak systolic flow velocity, Vd = end diastolic flow velocity). Placental tissue at delivery was examined for VEGF distribution with avidin-biotin-peroxidase immunohistochemistry.

RESULTS

Uterine resistance index [median (range)] was significantly increased in pre-eclamptic women (normotensive: 0.42 (0.36-0.51); pre-eclampsia: 0.59 (0.40-0.75); P = 0.005). Notching of the uterine artery waveform, consistent with a high resistance circulation, was evident in early diastole in five women with pre-eclampsia but only one normotensive woman (P = 0.013). Placental VEGF was increased in women with pre-eclampsia in the decidual trophoblast (normotensive: 34% (4-59) cells stained for VEGF; pre-eclampsia: 58% (15-95); P = 0.033) and in the villous syncytiotrophoblast (normotensive: VEGF count 1.4 arbitrary units (1.1-2.1); pre-eclampsia: 1.8 arbitrary units (1.4-2.2); P = 0.041). Analysis indicated that uterine artery resistance index was directly correlated with placental VEGF staining, mean arterial pressure and birthweight.

CONCLUSIONS

Abnormal uterine artery Doppler ultrasound flow velocity profiles in pre-eclampsia indicate increased uteroplacental resistance. The associated increase in placental VEGF may represent a compensatory mechanism attempting to restore blood flow towards normal.

Expression and regulation of vascular endothelial growth factor in a first trimester trophoblast cell line

Embryo implantation and development are critically dependent upon the spatial and temporal regulation of angiogenesis and localized vascular permeability. A key mediator of these effects is the endothelial cell mitogen vascular endothelial growth factor (VEGF). VEGF has been shown to promote endometrial vascular permeability, fetal vasculogenesis and placental, fetal and maternal angiogenesis. However, the mechanism through which this regulation occurs in the placenta is poorly understood. This study was conducted to determine if the pro-angiogenic cytokines, TNF-alpha and TGF-beta1, affect VEGF expression in human first trimester trophoblasts. Culture of a first trimester trophoblast cell line (HTR-8/SVneo), in the presence of either TNF-alpha or TGF-beta1, resulted in the expression of significant levels of VEGF in culture. The trophoblast cell line also showed a time-dependent and a dose-dependent increase in VEGF mRNA levels when cultured in the presence of either TNF-alpha or TGF-beta1. These results suggest that both TNF-alpha and TGF-beta1 may regulate the production of VEGF in early gestational trophoblasts and may therefore serve to modulate placental vascular permeability and angiogenesis that are necessary for embryo implantation and placentation.

Nutrient partitioning during pregnancy: adverse gestational outcome in overnourished adolescent dams

Appropriate nutrient partitioning between the maternal body and gravid uterus is essential for optimum fetal growth and neonatal survival, and in adult sheep nutrient partitioning during pregnancy generally favours the conceptus at the expense of the dam. However, recent studies using an overnourished adolescent sheep model demonstrate that the hierarchy of nutrient partitioning during pregnancy can be dramatically altered in young growing females. Overnourishing the adolescent dams to promote rapid maternal growth throughout pregnancy results in a major restriction in placental mass and leads to a significant decrease in birth weight relative to moderately-fed adolescents of equivalent gynaecological age. High maternal feed intakes are also associated with an increased incidence of non-infectious spontaneous abortion, a reduction in gestation length and colostrum production, and a higher incidence of neonatal mortality. The present paper examines the putative role of a variety of endocrine regulators of nutrient partitioning in this unusual model system, where the dam is overnourished while the stunted placenta restricts nutrient supply to the fetus. The central role of nutritionally-mediated alterations in placental growth and development in setting the subsequent pattern of nutrient partitioning between the maternal body, placenta and fetus is examined, and critical periods of sensitivity to alterations in maternal nutritional status are defined. Finally, the consequences of this form of inappropriate nutrient partitioning on the growth and development of the fetus and neonate are described with particular emphasis on the reproductive axis.

Levels of vascular endothelial growth factor are elevated in patients with ectopic pregnancy: is this a novel marker?

OBJECTIVE

To determine serum levels of vascular endothelial growth factor (VEGF) and evaluate their capacity to serve as a marker for the diagnosis of ectopic pregnancy (EP).

DESIGN

Prospective, case-controlled study.

SETTING

A tertiary care center.

PATIENT(S)

Twenty women with EP, 10 women with normal intrauterine pregnancy, and 10 women with abnormal intrauterine pregnancy, all at comparable stages of gestation.

INTERVENTION(S)

Serum samples were obtained from all women.

MAIN OUTCOME MEASURE(S)

All samples were analyzed for VEGF, progesterone, and beta-hCG by specific methods.

RESULT(S)

Women with EP had higher serum levels of VEGF than women with normal intrauterine pregnancy and women with abnormal intrauterine pregnancy (median levels, 226.8 pg/mL, 24.4 pg/mL, and 59.4 pg/mL, respectively). With a cutoff level of 200 pg/mL, serum VEGF could distinguish intrauterine from extrauterine pregnancy with a sensitivity of 60%, specificity of 90%, and positive predictive value of 86%.

CONCLUSION(S)

The increased serum VEGF levels in women with EP may facilitate this challenging diagnosis and reduce maternal morbidity and mortality.

Increased serum levels of vascular endothelial growth factor in patients with renal cell carcinoma

Neovascularization, an essential event for the growth of solid tumors, is regulated by a number of angiogenic factors. One such factor, vascular endothelial growth factor (VEGF), is considered to exert a potent angiogenic activity, as indicated by immunohistochemical and molecular evidence. In this study we investigated the serum VEGF level (s-VEGF) in patients with renal cell carcinoma (RCC). s-VEGF in peripheral blood samples was analyzed in 40 RCC patients and 40 patients without cancer (controls) using a sandwich enzyme-linked immunoassay. In 20 RCC patients, serum samples were obtained separately from the bilateral renal veins. s-VEGF was also measured before, 4 and 8 weeks after nephrectomy in 11 patients. There were significant differences in s-VEGF between the RCC patients and the controls (207.3+/-32.9 vs. 71.5+/-9.1 pg/ml, mean+/-SE) (P<0.005), between the tumor-bearing renal veins and the contralateral ones (P<0.01), between the pre- and post-nephrectomy situations (P<0.01) and among the various parameters of tumor status such as tumor extent (P<0.001) and existence of metastasis (P<0.001). s-VEGF significantly correlated with the tumor volume obtained by a three-dimensional measurement (r=0.802, P<0.0001). The sensitivity and specificity of s-VEGF at the cut-off level of 100 pg/ml, as determined by the receiver-operating-characteristics curve, were 80.0% and 72.5%, respectively. The results indicate that tumor tissue of RCC liberates VEGF into the systemic blood flow and that s-VEGF is a possible marker for RCC.

Lack of correlation between vascular endothelial growth factor production and endothelial cell proliferation in the human endometrium

The role of vascular endothelial growth factor (VEGF) in endometrial angiogenesis was examined by measuring its production in human endometrial tissues from different stages of the menstrual cycle and relating these data to endothelial cell proliferation in the same tissues. Conditioned medium was collected from explant, and separated glandular epithelial and stromal cells cultured from 24 normal human endometrial biopsies and VEGF measured by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was also used to assess VEGF and the percentage of proliferating microvessels in the samples. Wide variation in results between individual endometrial samples at each stage of the menstrual cycle was observed for all parameters measured. There was no significant difference in VEGF secretion by explant, glandular epithelial or stromal cell cultures across the menstrual cycle, or in the percentage of proliferating vessels. VEGF immunostaining in the stroma was elevated during the early proliferative stage (P = 0.03). Epithelial cells secreted more VEGF than stromal cells (1.76 +/- 0.46 versus 0.46 +/- 0.06 ng per 10(5) cells; P = 0.002). There was no correlation between VEGF secreted by cultured explants, epithelial or stromal cells, VEGF immunostaining and the proportion of proliferating microvessels. These results show that the majority of endometrial VEGF is produced by glands, but neither total glandular nor stromal VEGF is correlated with endometrial endothelial cell proliferation. There is still no clear understanding on the regulation of human endometrial angiogenesis.

Placenta growth factor: potential role in pregnancy

PROBLEM

In spite of the known requirement for adequate vascularity during placentation, little is known regarding the regulation of angiogenic growth factor production by trophoblast. Placenta growth factor (PIGF) is a recently discovered angiogenic growth factor whose expression is relatively limited to trophoblast.

METHOD OF STUDY

Current literature of PIGF was reviewed, with emphasis on its expression, regulation, role in angiogenesis, and potential function(s) at the maternal-fetal interface.

RESULTS

PIGF is abundantly expressed by trophoblast, which implies that it could act in a paracrine manner to modulate vascular development, stability, and/or function within the decidua and placental villi. In addition, expression of the PIGF receptor, fms-like tyrosine kinase (flt-1) receptor, on trophoblast raises the potential for an autocrine role of PIGF in regulating trophoblast growth and/or function.

CONCLUSIONS

The potential for PIGF to influence both vascular endothelial cells and trophoblast suggests that aberrant trophoblast production of PIGF could compromise cellular function during gestation and contribute to the vascular and placental pathologies noted in many obstetric complications.

Time-course of the uterine response to estradiol-17beta in ovariectomized ewes: expression of angiogenic factors

Uterine expression of angiogenic factors (vascular endothelial growth factor [VEGF] and basic fibroblast growth factor [bFGF]) was evaluated in ovariectomized ewes at 0, 2, 4, 8, 24, 48, or 72 h after estradiol (E2) treatment. Endometrial VEGF mRNA increased more than 5-fold from 0 to 4 h, remained elevated at 8 h, and then declined through 72 h after E2 treatment. In contrast, endometrial bFGF mRNA remained constant from 0 to 4 h, increased 2.2-fold from 4 to 8 h, remained elevated at 24 h, and then declined through 72 h. Immunostaining for VEGF was present in myometrial and endometrial microvessels (arterioles, venules, and/or capillaries) and also in myometrial smooth muscle; the pattern of VEGF immunostaining followed that of mRNA expression, being elevated at 4 and 8 h after E2 treatment. Immunostaining for bFGF was present exclusively in uterine glands; the pattern of bFGF immunostaining also followed that of its mRNA, being elevated at 8 and 24 h after E2. On the basis of these observations, we suggest that VEGF and bFGF are probably important factors responsible for the dramatic uterine microvascular response that occurs 8 to 24 h after E2 treatment in ovariectomized ewes.

Vectorial secretion of vascular endothelial growth factor by polarized human endometrial epithelial cells

OBJECTIVE

To analyze directional vascular endothelial growth factor (VEGF) secretion in polarized human endometrial epithelial cell cultures. VEGF has distinct distribution patterns in human endometrium. Stromal cells are diffusely positive for VEGF messenger RNA and protein, whereas glandular epithelium shows focal VEGF immunostaining at the apical surface. The epithelial distribution suggests that VEGF is secreted into gland lumina, potentially influencing the nutrition and/or apposition of the developing blastocyst.

DESIGN

Controlled in vitro study of protein secretion by polarized endometrial epithelial cells established on polyethylene filters.

SETTING

University hospital.

PATIENT(S)

Endometrial biopsies were obtained from healthy, ovulatory women undergoing elective surgery.

INTERVENTION(S)

Primary endometrial epithelial cells were cultured.

MAIN OUTCOME MEASURE(S)

VEGF mRNA and protein production were measured in polarized cells. The vectorial secretion of VEGF was determined.

RESULT(S)

VEGF production by endometrial epithelial cells was verified by Northern blotting and immunoassays of conditioned media. The mean (+/-SD) apical secretion of VEGF was 3.9 +/- 1.4 ng per 10(5) cells every 48 hours and the mean (+/-SD) basal secretion was 0.8 +/- 0.2 ng per 10(5) cells every 48 hours. In contrast, the apical and basal secretion of a soluble cellular isoform of fibronectin were 2.76 +/- 0.96 ng per 10(5) cells every 48 hours and 2.64 +/- 1.79 ng per 10(5) cells every 48 hours, respectively.

CONCLUSION(S)

VEGF is secreted preferentially into the lumina of endometrial glands. Apical VEGF may be an endometrial signal for blastocyst development or implantation.