Localization of mRNA for basic fibroblast growth factor in human placenta

Molecular and cellular underpinnings of normal and abnormal human placental blood flows

Abnormal placental function is well-established as a major cause for poor pregnancy outcome. Placental blood flow within the maternal uteroplacental compartment, the fetoplacental circulation or both is a vital factor in mediating placental function. Impairment in flow in either or both vasculatures is a significant risk factor for adverse pregnancy outcome, potentially impacting maternal well-being, affecting immediate neonatal health and even influencing the long-term health of the infant. Much remains unknown regarding the mechanistic underpinnings of proper placental blood flow. This review highlights the currently recognized molecular and cellular mechanisms in the development of normal uteroplacental and fetoplacental blood flows. Utilizing the entities of preeclampsia and fetal growth restriction as clinical phenotypes that are often evident downstream of abnormal placental blood flow, mechanisms underlying impaired uteroplacental and fetoplacental blood flows are also discussed. Deficiencies in knowledge, which limit the efficacy of clinical care, are also highlighted, underscoring the need for continued research on normal and abnormal placental blood flows.

Stimulatory effects of fibroblast growth factor 2 on proliferation and migration of uterine luminal epithelial cells during early pregnancy

Fibroblast growth factor 2 (FGF2) is a mitogen that induces proliferation, differentiation, and migration of cells, as well as angiogenesis and carcinogenesis via autocrine or paracrine actions. Fibroblast growth factor 2 expression is abundant in porcine conceptuses and endometrium during the estrous cycle and peri-implantation period of pregnancy. However, its intracellular actions in uterine epithelial cells have not been reported. The results of this study indicated abundant expression of FGFR1 and FGFR2 predominantly in uterine luminal and glandular epithelia during early pregnancy and that their expression decreased with increasing parity of the sows. Treatment of porcine uterine luminal epithelial (pLE) cells with FGF2 increased proliferation and DNA replication based on increases in proliferating cell nuclear antigen (PCNA) and initiation of G1/S phase progression. In addition, FGF2 increases phosphorylation of AKT, P70S6K, S6, ERK1/2, JNK, P38, and P90RSK in a time-dependent manner, and increases in their expression was suppressed by Wortmannin (a phosphatidylinositol 3-kinase [PI3K] inhibitor), U0126 (an ERK1/2 inhibitor), SP600125 (a JNK inhibitor), and SB203580 (a P38 inhibitor) based on western blot analyses. Also, the abundance of cytoplasmic p-AKT protein was decreased by Wortmannin and U0126, and p-ERK1/2 protein was reduced only by U0126. Furthermore, inhibition of each signal transduction protein reduced the ability of FGF2 to stimulate proliferation and migration of pLE cells. Collectively, these results indicate that activation of FGFR1 and FGFR2 by uterine- and endometrial-derived FGF2 stimulates PI3K/AKT and mitogen-activated protein kinase pathways for development of the porcine uterus and improvement of litter size.

Fibroblast growth factor 2 induces proliferation and distribution of G2 /M phase of bovine endometrial cells involving activation of PI3K/AKT and MAPK cell signaling and prevention of effects of ER stress

Fibroblast growth factor 2 (FGF2) is abundantly expressed in conceptuses and endometria during pregnancy in diverse animal models including domestic animals. However, its intracellular mechanism of action has not been reported for bovine endometrial cells. Therefore, the aim of this study was to identify functional roles of FGF2 in bovine endometrial (BEND) cell line which has served as a good model system for investigating regulation of signal transduction following treatment with interferon-tau (IFNT) in vitro. Results of present study demonstrated that administration of FGF2 to BEND cells increased their proliferation and regulated the cell cycle through DNA replication by an increase of PCNA and Cyclin D1. FGF2 also increased phosphorylation of AKT, P70S6K, S6, ERK1/2, JNK, and P38 in BEND cells in a dose-dependent manner, and expression of each of those transcription factors was inhibited by their respective pharmacological inhibitor including Wormannin, U0126, and SP600125. In addition, the increase in proliferation of BEND cells and activation of the protein kinases in response to FGF2 was suppressed by BGJ398, a FGFR inhibitor. Furthermore, proliferation of BEND cells was inhibited by tunicamycin, but treatment of BEND cells with FGF2 restored proliferation of BEND cells. Consistent with this result, the stimulated unfolded protein response (UPR) regulatory proteins induced by tunicamycin were down-regulated by FGF2. Results of this study suggest that FGF2 promotes proliferation of BEND cells and likely enhances uterine capacity and maintenance of pregnancy by activating cell signaling via the PI3K and MAPK pathways and by restoring ER stress through the FGFR.

Explant culture: An advantageous method for isolation of mesenchymal stem cells from human tissues

Mesenchymal stem cell (MSC) research progressively moves towards clinical phases. Accordingly, a wide range of different procedures were presented in the literature for MSC isolation from human tissues; however, there is not yet any close focus on the details to offer precise information for best method selection. Choosing a proper isolation method is a critical step in obtaining cells with optimal quality and yield in companion with clinical and economical considerations. In this concern, current review widely discusses advantages of omitting proteolysis step in isolation process and presence of tissue pieces in primary culture of MSCs, including removal of lytic stress on cells, reduction of in vivo to in vitro transition stress for migrated/isolated cells, reduction of price, processing time and labour, removal of viral contamination risk, and addition of supporting functions of extracellular matrix and released growth factors from tissue explant. In next sections, it provides an overall report of technical highlights and molecular events of explant culture method for isolation of MSCs from human tissues including adipose tissue, bone marrow, dental pulp, hair follicle, cornea, umbilical cord and placenta. Focusing on informative collection of molecular and methodological data about explant methods can make it easy for researchers to choose an optimal method for their experiments/clinical studies and also stimulate them to investigate and optimize more efficient procedures according to clinical and economical benefits.

Influence of Maternal Diabetes on Placental Fibroblast Growth Factor-2 Expression, Proliferation, and Apoptosis

OBJECTIVE

Type I diabetes mellitus during pregnancy is associated with dysregulation of the oxygen and glucose metabolic pathways, both of which affect placental villous growth and function. Alteration of placental development in women with diabetes may contribute to the increased risk of preeclampsia, macrosomia, or fetal growth restriction.

METHODS

To evaluate placental growth in the setting of maternal diabetes, immunohistochemical techniques were used to examine fibroblast growth factor-2 (FGF-2) expression, cell proliferation (Ki67), and apoptosis (Apo-Tag) in placentas from diabetic and nondiabetic patients.

RESULTS

Immunostaining for FGF-2 in placentas from diabetic women demonstrated an increase in intensity within the villous stroma and syncytiotrophoblast (P<.05). Associated with these changes in FGF-2 expression, placentas from diabetic women showed no change in villous mitotic activity but did show decreased stromal compartment apoptosis. When expressed as a ratio of Ki67-positive:Apo-Tag-positive nuclei as an index of relative cell turnover, the stromal compartment showed a significant trend towards decreased nuclei turnover (P<.05), suggesting relative tissue growth in diabetic patients.

CONCLUSION

Increased FGF-2 expression and decreased stromal cell compartment turnover in the diabetic placenta might be a compensatory mechanism in response to the altered physiologic milieu of maternal diabetes on placental function.

Imbalance of expression of bFGF and PK1 is associated with defective maturation and antenatal placental insufficiency

OBJECTIVE

Defective placental maturation is associated with restricted functional capacity and adverse perinatal fetal outcomes. The aim of the study was a comparative analysis of the role of mRNA expression of various angiogenic factors in placental maturation defects.

STUDY DESIGN

We examined the mRNA expression patterns of prokineticin 1 (PK1), its receptors (PKRs), basic-fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in tissue from third-trimester placentae that exhibited delayed or accelerated villous maturation.

RESULTS

The expression of PK1 and PKR2 was elevated in placental tissue exhibiting accelerated maturation and a predominant differentiation of terminal villi. The opposite was found in tissue exhibiting delayed maturation and deficiency of the terminal villi. In addition, low expression of bFGF correlated with the predominant differentiation of terminal villi, whereas the opposite was observed when terminal villi were deficient. The expression of VEGF, PIGF, and PKR1 showed no significant differences between the groups.

CONCLUSION

Defective placental maturation is associated with an imbalance of expression of bFGF and PK1. Our results demonstrate an involvement of the PK1/PKR2-signalling pathway in the regulation of the functional adequate capillarization in late pregnancy. We propose the bFGF/PK1-ratio as a monitor of placental function and a possible indicator of latent clinical problems, such as placental dysfunction leading to fetal hypoxia.

Pregnancy-associated retinal diseases and their management

Pregnancy-associated retinal diseases are conditions that may occur uniquely in pregnancy or, more commonly, general conditions that may worsen or alter during pregnancy as a result of hematologic, hormonal, metabolic, cardiovascular, and immunologic changes. Diabetic retinopathy (DR) is by far the most common retinal condition that is altered by pregnancy. However, there are currently no widely accepted, precise clinical guidelines regarding its management during pregnancy. At present it is not possible to predict who will regress and who will progress without treatment. Some of the variation in progression of DR in pregnancy may be a result of well-known risk factors such as hypertension or inadequate glycemic control prior to pregnancy. Other pregnancy-associated retinal diseases are relatively uncommon, and their treatments are poorly characterized. Pre-existing conditions include the white dot syndromes, such as punctuate inner choroidopathy and ocular histoplasmosis syndrome, as well as chorioretinal neovascularization from many other etiologies. Retinal and chorioretinal disorders that can arise during pregnancy include central serous chorioretinopathy and occlusive vasculopathy such as retinal artery occlusion (Purtschers-like retinopathy) and retinal vein occlusion. There remains a small group that appear to be unique to pregnancy, with pre-eclampsia- and eclampsia-associated retinopathy, disseminated intravascular coagulopathy, or amniotic fluid embolism being the best described. In angiogenic retinal diseases outside of pregnancy, the use of anti-vascular endothelial growth factor (anti-VEGF agents) has proven helpful. There are no safety data about the use of anti-VEGF agents during pregnancy, and conventionally the proposed interventions have been laser photocoagulation and systemic or intravitreal injections of steroids. Most of the literature on the treatment of pregnancy associated-chorioretinal neovascularization is anecdotal.

mRNA and protein expression of FGF-1, FGF-2 and their receptors in the porcine umbilical cord during pregnancy

The fibroblast growth factors (FGFs) are multifunctional proteins that, among other roles, regulate structural reorganization of uterine and placental vascular bed during pregnancy. Thus, we analyzed mRNA and protein expression and immunohistochemical localization of FGF-1 and FGF-2, and their receptors (FGFR-1 and FGFR-2) in the developing umbilical cord (UC) on days 40, 60, 75 and 90 of pregnancy and after the physiological delivery in the pig (day 114). qPCR analysis demonstrated an increase in FGF-1 and FGF-2 mRNA levels beginning on day 75 and on day 114 of pregnancy, respectively. In addition, significantly increased FGFR-1IIIc mRNA expression was also found on day 114. On the other hand, no significant changes in FGFR-2IIIb mRNA expression were observed. Western Blot analysis revealed a decrease in FGF-1 and FGFR-2 protein expression after day 40. Beside an increased protein expression of FGF-2 on day 60, no significant changes in FGFR-1 protein expression were detected. Immunohistochemical staining enabled detection of FGF-FGFR system, with different intensity of immunoreaction in endothelial and tunica media cells of the umbilical vessels and in allantoic duct and amniotic epithelium as well as in myofibroblasts. In conclusion, our results show that members of FGF-FGFR system are expressed specifically in UC structures. Furthermore their day of pregnancy-related expression suggest that they may be an important players during UC formation and development.

Angiogenesis in implantation

PROBLEM

Implantation failure and early pregnancy loss are common following natural conceptions and they are particularly important clinical hurdles to overcome following assisted reproduction attempts. The importance of adequate vascular development and maintenance during implantation has recently become a major focus of investigation.

MATERIALS AND METHODS

Review of current published literature was undertaken to summerize the cells and cell products that regulate tissue vascularity during implantation.

RESULTS

Vascular development at the maternal fetal interface can be regulated by a number of different cell types; two principal candidates are trophoblast and natural killer cells. A wide range of soluble factors, some with well established angiogenic functions as well as other more novel factors, can contribute to vascular development and maintenance at the maternal-fetal interface.

CONCLUSIONS

Robust vascular development occurs during implantation and early placentation of normal pregnancies. Studies to define the extent and mechanisms by which defects in vascularity contribute to human implantation failure and early miscarriage need to be undertaken.

Human placental protein/peptides stimulate melanin synthesis by enhancing tyrosinase gene expression

Placental protein/peptides as biological response modifier are well documented, but not much known about melanogenesis. We possibly for the first time, demonstrated melanogenesis in B16F10 mouse melanoma by a placental protein/peptide fraction (PPPF) prepared from a hydroalcoholic extract of fresh term human placenta. This study described the effect of PPPF on the induction of tyrosinase; the key enzyme of melanogenesis to investigate the basis of PPPF induced pigmentation in primary melanocyte and B16F10 melanoma. Tyrosinase induction by PPPF in B16F10 cells was found dose- and time dependent at the level of activity. Tyrosinase, at the level of transcription and protein expression when assessed by RT-PCR and Western blot analyses found to have considerable induction over untreated control. PPPF led to enhanced activation of tyrosinase promoter resulting higher transcription thus substantiating the role of PPPF as a stimulator of melanogenesis. Actinomycin D, the transcriptional inhibitor of protein synthesis, blocked the stimulatory action of PPPF since the induction of tyrosinase and melanin was markedly reduced in presence of this inhibitor. Thus the results suggested that PPPF mediated increase in tyrosinase expression occurred through transcriptional upregulation to stimulate melanogenesis in B16F10 cells and in primary melanocyte also.

Initial differentiation of blastomeres in 4-cell human embryos and its significance for early embryogenesis and implantation

This brief review is devoted to the nature of early blastomere differentiation in human 4-cell embryos and its consequences for embryonic development. Precursor cells of inner cell mass, germline, and trophectoderm may be formed at this stage, the clearest evidence being available for trophectoderm. The sites of these precursor cells in the embryo could be ascertained using markers for animal and vegetal poles, observing specific cleavage planes, and assessing gene and protein expression. This opens new opportunities for studying 4-cell embryos and removing or replacing specific cells. Knowledge of the properties of individual blastomeres should help in improving assisted human reproduction, performing preimplantation genetic diagnosis, and perhaps establishing specific stem cell lines. Special attention is paid to well-characterized trophectoderm, the trophectoderm stem cell, and possible new forms of clinical application.

Fibroblast growth factor-10 and fibroblast growth factor receptors 1-4: expression and peptide localization in human decidua and placenta

The development of the chorionic villous tree into a complex and organized ramified tubular network can be termed branching morphogenesis. Studying the molecular mechanisms involved in this process may contribute to the understanding of pregnancy complications such as preeclampsia. We hypothesized that fibroblast growth factor-10 (FGF-10) and fibroblast growth factor receptors 1-4 (FGFR 1-4) are expressed in human decidual and placental tissues. We analyzed the expression of FGF-10 and FGFRs 1-4 in 1st, 2nd and 3rd trimester placentas, as well as in decidua. RT-PCR and immunohistochemistry were employed to study mRNA and protein expression. FGF-10 was expressed by decidual cells and by cytotrophoblasts of the cytotrophoblast columns during all three trimesters. FGFR 1-4 were expressed in the placenta but not in the decidua. Placental expression of FGFRs was temporally regulated: In 1st trimester placentas, FGFR 1-4 were expressed by Hofbauer cells, FGFR-1 and FGFR-4 were expressed in cytotrophoblast columns, and the latter was also expressed by syncytiotrophoblasts. Similar expression was seen in 2nd trimester placentas with additional expression of FGFR-1 in blood vessel walls. The expression of FGFR-1 and FGFR-4 in the 3rd trimester was comparable to that seen in the 2nd trimester. The expression of FGF-10, FGFR-1 and FGFR-4 in the maternal-fetal interphase suggests their role in decidual-trophoblast interaction. The abundance of FGFR expression in Hofbauer cells implies that mesenchymal-trophoblast interaction is important for regulation of villous development.

Placental growth by the estrogen-dependent angiogenic factors, vascular endothelial growth factor and basic fibroblast growth factor, throughout gestation

Angiogenesis is essential for the development and growth of the human placenta throughout gestation, under the influence of enriched estrogen. This prompted us to study the clinical implications of estrogen-dependent angiogenic factors derived from the human placenta. Fifty-eight women ranging from 6 to 41 weeks' gestational age (25 in the first trimester, 12 in the second trimester and 21 in the third trimester) underwent abortion and delivery. The levels of angiogenic factors in the placenta were determined by enzyme immunoassay, and the mRNA and protein of vascular endothelial growth factor (VEGF) variants were analyzed by reverse transcriptase-polymerase chain reaction and Western blotting, respectively. The levels of VEGF, especially VEGF165, and bFGF correlated with placental weights throughout gestation. Estrogen-dependent VEGF, especially VEGF165, and bFGF might work on growth via angiogenesis in the human placenta throughout all trimesters of gestation.

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

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

Aspects of human fetoplacental vasculogenesis and angiogenesis. II. Changes during normal pregnancy

In this second review, we describe the main morphological events which accompany the development of the fetoplacental vascular system throughout normal human pregnancy and summarize findings on the expression of angiogenic growth factors and their receptors. Fetoplacental vasculogenesis starts at day 21 after conception by formation of haemangioblastic cords. In the following phase of branching angiogenesis (day 32 to week 25 post conception), haemangioblastic cords develop into a richly branched villous capillary bed with low fetoplacental blood flow impedance. This period is characterized by high placental levels of VEGF but moderate PlGF expression. In week 15, large centrally located villi show regression of peripheral capillary nets. In parallel, some remaining central capillaries acquire a tunica media and transform into arteries and veins. Beginning at about week 25 in the newly formed peripheral villi, angiogenesis switches from branching to non-branching and this period is accompanied by a steep drop in VEGF and a slower decline in PlGF expression. As a consequence of this switch, long poorly branched capillary loops are formed in the periphery of the fetoplacental vascular trees. These increase fetoplacental impedance but blood flow still increases due to rising fetal blood pressure. The possible interactions between (a). the biphasic development of intraplacental oxygen tensions, (b). changes in VEGF and PlGF levels and (c). developing vascular geometry are discussed. Special attention is given to the obvious discrepancy between sudden elevation of intervillous oxygen tensions which is not coincident with the appearance of angiogenic growth factor peaks and the switch from branching to non-branching angiogenesis. Finally, we deal with methods of quantifying aspects of angiogenesis in the villous vascular system and summarize the main findings during uncomplicated human pregnancy.

Sequential Expression of VEGF and its Receptors in Human Placental Villi During Very Early Pregnancy: Differences Between Placental Vasculogenesis and Angiogenesis

Vascularization within the human placenta is the result of the de novo formation of vessels derived from pluripotent precursor cells in the mesenchymal core of the villi. Vascularization of placental villi starts at around day 21 post conception (p.c.) with a four somite embryo. At this stage progenitors of haemangiogenic cells differentiate to form first vessels. These progenitor cells are thought to be directly derived from mesenchymal cells rather than originating from fetal blood cells. We investigated the relation between differentiation of stromal cells towards endothelial cells and vascular structures and the expression pattern of the respective growth factors. Using transmission electron microscopy and immunohistochemistry (for VEGF, Flt-1, Flk-1, CD14, CD34, and CD68) the development of placental vasculogenesis during very early stages of pregnancy (days 22-48 p.c.) was studied. We found that VEGF is strongly expressed in villous cytotrophoblast cells and subsequently in Hofbauer cells while its receptors Flt-1 and Flk-1 are found on vasculogenic and angiogenic precursor cells. The developmental expression and secretion of VEGF suggests its involvement in recruitment, maintenance and formation of first angiogenic cells and vessels. Interactions between VEGF and Flk-1 and Flt-1 may regulate placental vasculogenesis and angiogenesis in a paracrine and autocrine manner. The sequential expression of growth factors in different cell types may point to the fact that placental vasculogenesis and angiogenesis are clearly distinct events.

Growth factor rescue of cytokine mediated trophoblast apoptosis

INTRODUCTION

Apoptosis can be induced in cytotrophoblasts and syncytiotrophoblast in culture by a combination of TNF-alpha and IFN-gamma (Yui et al., 1994a; Garcia-Lloret et al., 1996). This apoptotic action of TNF-alpha and IFN-gamma can be inhibited/'rescued' by EGF (Garcia-Lloret et al., 1996). Additional 'survival' factors have been sought which might protect cells against apoptosis induced by TNF-alpha/IFN-gamma. The survival factors investigated were bFGF, IGF-1, PDGF-AA, VEGF and PLGF. These cytokines were chosen specifically because in common with EGF, the receptors for these molecules are all direct protein tyrosine kinases.

MATERIALS AND METHODS

All the experiments were carried out using a standard cell culture protocol (Yui et al., 1994a, b; Garcia-Lloret et al., 1996). Apoptosis was induced using TNF-alpha/IFN-gamma, and rescue was attempted using the various cytokines. Apoptosis was identified using the TUNEL technique and quantified by counting 3000 cells in each experimental well.

RESULTS

As in previous studies EGF produced a complete inhibition of the apoptotic action of TNF-alpha/IFN-gamma. bFGF, IGF-1, and PDGF-AA produced a partial but significant inhibition of the apoptotic action of TNF-alpha/IFN-gamma. VEGF and PLGF in these experiments had no protective effects against TNF-alpha/IFN-gamma induced apoptosis.

DISCUSSION

Previous studies relating to EGF have been confirmed. bFGF, IGF-1, and PDGF have all been shown to provide partial protection against TNF-alpha/IFN-gamma induced apoptosis. VEGF and PLGF did not protect against apoptosis, and the mechanisms of action remain unclear.

Placental development in normal and compromised pregnancies-- a review

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

Angiogenesis and intrauterine growth restriction

Human placental development involves co-ordinated angiogenesis and trophoblast outgrowth that are compromised in intrauterine growth restriction. Adaptive angiogenesis in IUGR placental villi is a result of an imbalance in the orderly progression of the expression profile of vascular endothelial growth factor, placenta growth factor and angiopoietin during placental development. VEGF receptors and the angiopoietin receptor Tie-2 are expressed on trophoblast, and their activation leads to trophoblast proliferation, migration and production of nitric oxide. Thus, these vascular factors act as autocrine regulators of trophoblast behaviour in the development of the utero-/feto-placental circulation, an action independent of their well-established roles in vascular endothelium.

Angiopoietin-1 and angiopoietin-2 activate trophoblast Tie-2 to promote growth and migration during placental development

Human placental development involves coordinated angiogenesis and trophoblast outgrowth that are compromised in intrauterine growth restriction (IUGR). As Tie-2((-/-)) mice exhibit growth retardation and vascular network malformation, the expression of Tie-2 and its ligands, angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), were investigated in human placenta from normal pregnancies and those complicated by severe IUGR. Ribonucleotide protection assays showed no significant change in the expression of Ang-2 mRNA between gestationally matched normal and IUGR placentas; however, immunoblots revealed that Ang-2 protein was significantly decreased in IUGR, suggesting that this may contribute to the abnormal development of the villous vasculature. In situ hybridization studies showed that Ang-1 and Tie-2 were detected in the cyto/syncytiotrophoblast bilayer in first-trimester placenta, whereas Ang-2 mRNA was restricted to the cytotrophoblast, suggesting their role in trophoblast function. At term, Ang-1 mRNA and immunoreactive protein were restricted to the paravascular tissues of the primary stem villi, supporting its role in vessel maturation. In contrast, Ang-2 was expressed throughout the term villous core, perhaps to permit the developing placental vascular network to remain in a state of fluidity. As these studies also revealed that trophoblast, in addition to endothelial cells, expressed Tie-2 receptors, we investigated the potential role of Ang-1/Ang-2 on trophoblast proliferation, migration, and the release of NO. Using spontaneously transformed first-trimester trophoblast cell lines that exhibit cytotrophoblast-like (ED(27)) and extravillous trophoblast-like (ED(77)) properties, we show that the addition of Ang-2 (250 ng/ml) stimulated DNA synthesis in ED(27) trophoblast cells and triggered the release of NO. Ang-1 stimulated trophoblast (ED(77)) migration in a dose-dependent manner that was inhibited by recombinant Tie-2-FC. These data thus imply, for the first time, a specific role for angiopoietins as regulators of trophoblast behavior in the development of the utero/fetoplacental circulation, an action independent of their well-established roles in vascular endothelium.

Regulation of placental vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) and soluble Flt-1 by oxygen--a review

Morphological studies show poor placental vascular development and an increase in the mitotic index of cytotrophoblast cells in intrauterine growth restriction (IUGR). We hypothesized that the reported relatively high oxygen level in the intervillous space in contact with IUGR placental villi will limit angiogenesis by changes in vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) expression and function. Western immunoblot analysis demonstrates a diametric expression of PIGF and VEGF proteins throughout pregnancy, with P1GF levels increasing and VEGF levels decreasing, consistent with placental oxygenation. PIGF mRNA and protein is increased in IUGR as compared to gestationally matched normal placentae. Increasing oxygen tension upregulates P1GF protein in term placental villous explants, whereas hypoxia downregulates P1GF and VEGFR-1 (Flt-1) autophosphorylation in term trophoblast choriocarcinoma cell line (BeWo). Levels of soluble Flt-1 (sFlt-1) protein in supernatant of term villous explants were upregulated by 1 per cent hypoxia, whereas hyperoxia (40 per cent) decreased sFlt-1 levels, indicating that under conditions of increasing oxygen tension, PlGF function may remain unopposed. The addition of PlGF-1 to a spontaneously transformed first trimester cytotrophoblast cell line (ED27) stimulated cell proliferation while PlGF-2 had little effect. In contrast, the addition of PlGF-1 had little effect on endothelial cell proliferation while this was inhibited by PIGF-2. Taken together these changes provide a molecular explanation for the observed poor angiogenesis in the pathogenesis of IUGR.

Localization, quantification, and activation of platelet-activating factor receptor in human endometrium during the menstrual cycle: PAF stimulates NO, VEGF, and FAKpp125

Implantation is characterized by an inflammatory-like response with expansion of extracellular fluid volume, increased vascular permeability, and vasodilatation. These effects are believed to be mediated at the paracrine level by prostaglandin E2 and platelet-activating factor (PAF), but the cellular mechanism (or mechanisms) remains largely unknown. We demonstrate that PAF receptor (PAF-R) immunoreactivity and mRNA are detected in proliferative and secretory endometrial glands, however, the responsiveness of endometrium to physiological concentrations of PAF is confined predominantly to the secretory endometrium. Semiquantitative reverse transcription-polymerase chain reaction revealed that PAF-R transcript levels were highest in the mid-late proliferative and late secretory phases of the cycle. Interaction of PAF with its receptor resulted in the rapid release of nitric oxide (NO), increased expression of vascular endothelial growth factor (VEGF), and activation of FAKpp125, a focal adhesion kinase, demonstrating that the PAF-R is functionally active. Inhibition of NO synthesis by NG-monomethyl-L-arginine produced dose-dependent attenuation of PAF-evoked NO release, indicating NOS activation; the dependency of PAF-evoked NO release on PKC and extracellular Ca2+ was confirmed by PKC inhibitor Ro 31-8220 and by the removal of extracellular Ca2+. PAF up-regulated VEGF gene expression in a concentration- and time-dependent fashion in human endometrial epithelial cell lysates. Transcription of VEGF was rapidly followed by secretion of the protein. These data support our premise that this autocoid acts as an angiogenic mediator in the regeneration of the endometrium after menses and as a vasodilator to promote blastocyst attachment during the implantation process.

Fibroblast growth factor-2 and fibroblast growth factor receptor-1 mRNA expression and peptide localization in placentae from normal and diabetic pregnancies

Fibroblast growth factor-2 (FGF-2) is a potent mitogen expressed widely during embryogenesis and in tissues of the human fetus. It is recognized as an endothelial cell mitogen and is angiogenic in vivo. Expression of FGF-2 mRNA has also been shown within the human term placenta, and FGF-2 isolated from placental tissue, suggesting a role in placental growth including angiogenesis. The purpose of this study was to quantify and localize the sites of expression of FGF-2 and its high-affinity receptor, FGFR1, within placentae from normal term human pregnancies (n=8, 39-42 weeks), and pregnancies complicated by pregestational, type 1 diabetes (n=8, 36-40 weeks). Tissues were collected immediately following delivery and were either snap-frozen for RNA isolation, or fixed for either in situ hybridization using a 35S-labelled cRNAs encoding human FGF-2 or FGFR1, or immunocytochemistry using antibodies against human FGF-2 or FGFR1. Northern blot hybridization showed a significantly increased abundance of mRNAs for both FGF-2 and FGFR1 in placentae from diabetic women compared to those from normal women. In normal term placenta FGF-2 mRNA was present at low abundance in fetal villous tissue, in the vascular endothelium of blood vessels, and in the syncytiotrophoblast. FGF-2 mRNA was considerably more abundant in the syncytiotrophoblast and villous tissue of placentae from diabetic patients. Messenger RNA for FGFR1 was similarly distributed to that encoding FGF-2. Immunocytochemistry revealed abundant FGF-2 and FGFR1 peptides in villous vascular endothelial cells, and associated with the cell membranes of stromal tissues in placentae from control pregnancies. Little immunoreactive FGF-2 was present in the syncytiotrophoblast at term. In pregnancies complicated by diabetes intense staining for immunoreactive FGF-2 and for FGFR1 additionally existed in syncytiotrophoblast. The results suggest that FGF-2 acting as an autocrine agent contributes to placental angiogenesis, but may be released from the syncytium into the maternal circulation. Expression is elevated in placentae from diabetic pregnancies, and is particularly associated with the syncytiotrophoblast. This suggests a placental source for the elevated circulating maternal FGF-2 previously described in diabetic pregnancy.

Expression of syndecan-1 in human placenta and decidua

Syndecan-1 is a cell surface heparan sulphate proteoglycan, which binds to the extracellular matrix (ECM), growth factors and antithrombin III. The early expression of syndecan-1 during mouse embryonic development suggests a potential role in the communication between the embryo and the ECM of decidua. Using immunohistochemical methods, the present study showed that the expression of syndecan-1 in the trophoblast cells changes along trophoblast differentiation. The syncytiotrophoblasts in the chorionic villi exhibited an apical expression of syndecan-1. This suggests that the expression is restricted to non-migrating, non-proliferating trophoblasts. The mode of syndecan-1 expression by human placental trophoblasts is independent of gestational age. The expression is not changed in miscarriages. In pre-eclampsia, the staining for syndecan-1 on the villous syncytiotrophoblast is weaker compared to normal pregnancy, but in placental bed the expression is similar. The unique apical localization of syndecan-1 in chorionic villi, not detected in any other tissues, suggests a potential role in fetomaternal communication probably via growth factor binding and in anticoagulation of intervillous circulation.

Evidence for basic fibroblast growth factor as a crucial angiogenic growth factor, released from human trophoblasts during early gestation

The objective of this study was to clarify the possible angiogenesis-promoting factors from human trophoblasts in early stage gestation. The existence of angiogenic growth factors such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) in the condition medium from human villous trophoblasts was determined. Biological activity of angiogenic growth factors released by trophoblasts was examined using vascular endothelial cell lines. The condition medium from trophoblasts enhanced the growth of endothelial cells. Although cultured trophoblasts exhibited immunoreactive products for both bFGF and VEGF in the cytoplasm, only bFGF was detected in the condition medium by ELISA. The growth-enhancing activity of the condition medium was eliminated completely by the addition of anti-bFGF antibody but not with anti-VEGF antibody. Thus, trophoblastic cells seem to play an important role in extensive angiogenesis occurring in early gestation, mainly by releasing bFGF but not VEGF.

Pathogenetic implication of interleukin-2 expressed in preeclamptic decidual tissues: a possible mechanism of deranged vasculature of the placenta associated with preeclampsia

PROBLEM

The purpose of this study is to clarify whether IL-2 expressed in the decidua in preeclampsia affects the angiogenesis of the placenta.

METHOD OF STUDY

We investigated the angiogenic substances released from human trophoblasts obtained from early pregnancy that had been pretreated with either IL-2, non-activated lymphocytes from peripheral blood mononuclear cells (PBMCs), decidual lymphocytes, or these lymphocytes activated by lymphokine (LAK cells). Angiogenic activity was determined by evaluating the ability of growth-promotion of cultured human microvascular endothelial cells (HMvECs) using MTT assay.

RESULTS

Trophoblasts pretreated with IL-2 or non-activated lymphocytes, irrespective of their origin, released angiogenic factor similar to those without pretreatment. However, trophoblasts pretreated with LAK cells released less angiogenic factor compared with those without pretreatment.

CONCLUSIONS

Interleukin-2 (IL-2) expressed in preeclamptic decidua might reduce the angiogenic substances arising from trophoblasts by inducing LAK-cells from decidual lymphocytes, which might be relevant to deranged vasculature of the placenta, a characteristic histology in preeclampsia.

Localisation of placenta growth factor (PIGF) in human term placenta

Placenta growth factor (PlGF) is a growth factor which belongs to the vascular endothelial growth factor (VEGF) family and is known to bind to the fms-like tyrosine kinase receptor (flt-1). Using Western blot analysis a 50 kDa band was identified in placental protein extract which corresponded to PlGF homodimer. Immunoreactive PlGF was localised to the vasculosyncytial membrane and in the media of large blood vessels of the placental villi, while staining within the mesenchyme was weak and diffuse. There was moderate staining for PlGF in discrete cells in the chorion and no staining in the epithelial layer of the amnion. The maternal decidual cells showed strong staining for PlGF immunoreactive protein. PlGF mRNA was predominantly expressed by the vasculosyncytial membrane of villous trophoblast, whilst there was no apparent expression of PlGF mRNA within the villous mesenchyme. These results suggest that PlGF may be an important paracrine factor for vascular endothelial cells in placental angiogenesis and an autocrine mediator of trophoblast function.

Localization of the angiotensin II and its receptor subtype expression in human endometrium and identification of a novel high-affinity angiotensin II binding site

Angiotensin (ANG) II is not only a potent vasoconstrictor but may also be involved in the regeneration of new blood vessels. In proliferative endometrium, ANG II-like immunoreactivity was detected in glandular epithelium and stroma with negligible staining around the vascular endothelium. In contrast, in secretory endometrium intense immunostaining was seen in the perivascular stromal cells around the endometrial spiral arterioles with negligible staining of the other cell types. Quantitative receptor autoradiography using the nonselective radioligand [125I]-ANG II and subtype selective competing compounds showed that endometrium contained predominantly AT2 receptors, with relatively low expression of AT1 receptors and a novel non-AT1/non-AT2 angiotensin II recognition site that was insensitive to AT1 or AT2 selective ligands. Levels of specific [125I]-ANG II receptor binding displayed cyclic changes during the menstrual cycle, reaching a maximum in early secretory endometrium and then decreasing in mid to late secretory endometrium to levels seen in early to mid proliferative endometrium. In situ hybridization showed AT1 receptor mRNA expression in the glands and in the endometrial blood vessels. The cyclic changes in ANG II-like immunoreactivity together with expression of both the known and the novel AT receptor subtypes imply that this octopeptide may play a dual role both in the control of the uterine vascular bed and also in the regeneration of the endometrium after endometrial shedding, acting as an angiogenic and mitogenic mediator.

Colocalisation of vascular endothelial growth factor and its Flt-1 receptor in human placenta

Vascular endothelial growth factor (VEGF) is an angiogenic protein which acts on both endothelial and trophoblast cells. In first trimester placenta, VEGF immunoreactive protein was detected in cytotrophoblast shell suggesting a role in the regulation of cytotrophoblast growth and differentiation as they also expressed VEGF receptor (flt-1) protein. VEGF and flt-1 immunoreactive proteins were expressed in Hofbauer cells within the villous mesenchyme, macrophages and in maternal decidual cells while weak VEGF immunoreactive protein was seen in syncytiotrophoblast surrounding the placental villi in first and second trimester placentae. At term, there was relatively weak VEGF and flt-1 immunostaining in the syncytiotrophoblast while intense VEGF immunostaining was seen in the Hofbauer and maternal decidual cells. Extravillous trophoblast showed immunostaining for flt-1 but no staining for VEGF. Both amnion and chorion expressed strong VEGF immunoreactivity throughout gestation. Smooth muscle cells surrounding the vein and arteries of the umbilical cord showed weak VEGF immunoreactivity while no immunoreactivity was localised in endothelial cells. VEGF stimulated parathyroid hormone-related protein (PTHrP) release (mean (+/- SD): basal, 0.96 +/- 0.03; 10 ng/ml VEGF165, 2.07 +/- 0.18 and 20 ng/ml VEGF165, 2.43 +/- 0.18 pmol/l/well of PTHrP1-86) in condition medium from immortalised first trimester trophoblast cell line. These results suggest that VEGF in addition to acting as an autocrine mitogen for trophoblast proliferation may also function as a paracrine mediator of vascular tone by releasing vasorelaxants from trophoblasts.