Oxygen-mediated regulation of gelatinase and tissue inhibitor of metalloproteinases-1 expression by invasive cells

The relative expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) is an important determinant in trophoblast invasion of the uterus and tumor invasion and metastasis. Our previous studies have shown that low oxygen levels increase the in vitro invasiveness of trophoblast and tumor cells. The present study examined whether changes in oxygen levels affect TIMP and MMP expression by cultured trophoblast and breast cancer cells. Reverse zymographic analysis demonstrated reduced TIMP-1 protein secretion by HTR-8/SVneo trophoblast cells as well as MDA-MB-231 and MCF-7 breast carcinoma cells cultured in 1% vs 20% oxygen for 24 h. While gelatin zymography revealed no changes in the levels of MMP-9 secreted by HTR-8/SVneo trophoblasts cultured under various oxygen concentrations for 24 h, human MDA-MB-231 breast carcinoma cells displayed increased MMP-9 secretion and human MCF-7 breast cancer cells exhibited reduced secretion of this enzyme when cultured under similar conditions. In contrast, MMP-2 levels remained unchanged in all cultures incubated under similar conditions. Western blot analysis of MMP-9 protein in cell extracts confirmed the results of zymography. To assess the contribution of enhanced MMP activity to hypoxia-induced invasion, the effect of an MMP inhibitor (llomastat) on the ability of MDA-MB-231 cells to penetrate reconstituted extracellular matrix (Matrigel) was examined. Results showed that MMP inhibition significantly decreased the hypoxic upregulation of invasion by these cells. These findings indicate that the increased cellular invasiveness observed under reduced oxygen conditions may be due in part to a shift in the balance between MMPs and their inhibitors favoring increased MMP activity.

Effects of matrix proteins on the expression of matrix metalloproteinase-2, -9, and -14 and tissue inhibitors of metalloproteinases in human cytotrophoblast cells during the first trimester

The activity of matrix metalloproteinases (MMPs) specifies the ability of the trophoblast cell to degrade extracellular matrix (ECM) substrates. Usually the process of normal human placentation involves a coordinated interaction between the fetal-derived trophoblast cells and their microenvironment in the uterus. In this study, the effects of ECM proteins on the expression of MMP-2, -9, and -14 (membrane-type MMP-1); and the production of tissue inhibitors of metalloproteinase (TIMP) types -1, -2, and -3 have been investigated. Cytotrophoblast cells at 9 or 10 wk of gestation were cultured on various ECM coated dishes under serum-free conditions. Gelatin zymography analysis showed that cells grown on fibronectin (FN), laminin (LN), and vitronectin (VN) secreted more MMP-9 (about 1.5- to 3-fold more) than cells cultured on collagen I (Col I), whereas the secretion of MMP-9 by cells cultured on collagen IV (Col IV) was only half that by the cells on Col I. Northern Blot analysis gave the same results as zymography, indicating that expression of the MMP-9 gene in cytotrophoblast cells can be affected by matrix proteins. There was no significant difference in the expression of MMP-2 either at protein or mRNA levels among the cells cultured on the different matrix substrates. The expression of MMP-14 was regulated in a manner similar to that of MMP-2. Using ELISA, we detected higher levels of TIMP-1 in the culture medium of cells grown on VN, LN, and FN compared with that grown on Col I. But the expression of TIMP-3 mRNA was remarkably inhibited by VN, and ECM proteins had no effect on TIMP-1 and TIMP-2 mRNA expression. It was also observed that cultured cytotrophoblast cells expressed the corresponding receptors for the tested matrix proteins, such as integrins alpha(1), alpha(5), alpha(6), beta(1), and beta(4). Furthermore, the adhesiveness of cytotrophoblast cells on Col I, Col IV, FN, and LN was increased by 62%, 45%, 21%, and 22%, respectively, when compared with adhesiveness on VN. Isolated cytotrophoblast cells remained stationary when cultured on dishes coated with Col I and Col IV, but they assumed a more motile morphology and aggregated into a network when cultured on LN and VN. These data indicate that human trophoblast cells interact with their microenvironment to control their behavior and function.

[Culture of human trophoblast cells in vitro as a research method--review of techniques (Part I)]

In part I, several histological techniques applied for establishing the human trophoblast cell cultures are characterized. The methods of isolation and purification of trophoblast cells, as well as the management of selective culture are discussed.

[The 2 differentiation pathways of the human trophoblast]

The trophoblast is the major component of the human placenta. It is directly involved in blastocyst implantation and in feto-placental growth and development. Human trophoblast follows two major pathways of differentiation: the villous trophoblast, bathing in maternal blood of intervillous spaces and involved in matemo-fetal exchanges and in placental endocrine functions; the extra-villous trophoblast involved in uterine spiral arteries remodeling and in the placental anchorage into the uterine wall. It is essential to understand the cellular and molecular mechanisms involved in human trophoblast differentiation: cellular proliferation, migration, invasion and differentiation by cell-cell fusion. Abnormal trophoblast differentiation is implicated in the major pathologies of human pregnancy such as pre-eclampsia and intrauterine growth retardation.

Endogenous production of nitric oxide by vascular endothelial growth factor down-regulates proliferation of choriocarcinoma cells

The trophoblast-like choriocarcinoma cell line BeWo expresses a receptor for vascular endothelial growth factor (VEGF) and proliferates in response to VEGF. Nitric oxide (NO) seems to play a key role in the VEGF-induced proliferation of endothelial cells but the NO mechanistic regulation of VEGF-stimulated trophoblast proliferation is presently unclear. We assessed the effect of exogenous VEGF on BeWo cell proliferation by [3H]thymidine incorporation. The VEGF-induced proliferation of BeWo cells was significantly increased by the NO synthase (NOS) inhibitor, N(omega)-nitro-l-arginine methyl ester (L-NAME), but was inhibited by the NO donor, sodium nitroprusside. Treatment of the cells with 10 ng/ml of VEGF increased not only eNOS expression but also NO production. The extracellular signal-regulated kinase (Erk) of the mitogen-activated protein kinase (MAPK) family was activated by VEGF as demonstrated by the phosphorylation of Erk in Western blots. The effects of VEGF on NO production and the expression of endothelial NOS (eNOS) were attenuated by treating BeWo cells with the selective inhibitor of MAPK kinase, PD98059. VEGF-stimulated proliferation of BeWo cells was inhibited by the tyrosine kinase inhibitor genistein but increased by PD98059. Other kinase inhibitors, including LY294002 (phosphoinositide 3-kinase inhibitor) and SB203580 (P38 MAPK inhibitor), had no effect on the proliferation of the cells and NO production. These results indicate that endogenous NO production down-regulates the VEGF-stimulated proliferation of BeWo cells and that the activation of Erk plays an important role in this mechanism.

alpha-, beta-, gamma-catenin, and p120(CTN) expression during the terminal differentiation and fusion of human mononucleate cytotrophoblasts in vitro and in vivo

The cadherins play key roles in the formation and organization of the mammalian placenta by mediating cellular interactions and the terminal differentiation of trophoblastic cells. Although cadherin function is regulated by the cytoplasmic proteins, known as the catenins, the identity and expression pattern(s) of the catenins present in the trophoblastic cells of the human placenta have not been characterized. In these studies, we have determined that alpha-, beta-, gamma-catenin, and p120(ctn) expression levels are high in villous cytotrophoblasts isolated from the human term placenta but decline as these cells undergo aggregation and fusion to form syncytium with time in culture. In contrast, the expression levels of these four catenin subtypes remained constant in non-fusing JEG-3 choriocarcinoma cells at all of the time points examined in these studies. alpha-, beta-, gamma-catenin, and p120(ctn) expression was further immunolocalized to the mononucleate cells present in these two trophoblastic cell cultures. Similarly, intense immunostaining for all four catenins was detected in the mononucleate villous cytotrophoblasts of the human first trimester placenta. Collectively, these observations demonstrate that the expression levels of alpha-, beta-, gamma-catenin, and p120(ctn) are tightly regulated during the formation of multinucleated syncytium in vitro and in vivo.

Inability to enter S phase and defective RNA polymerase II CTD phosphorylation in mice lacking Mat1

The trimeric Cdk7-cyclin H-Mat1 complex comprises the kinase subunit of basal transcription factor TFIIH and has been shown to function as a cyclin-dependent kinase (Cdk)-activating kinase. Herein we report that disruption of the murine Mat1 gene leads to peri-implantation lethality coincident with depletion of maternal Mat1 protein. In culture, Mat1(-/-) blastocysts gave rise to viable post-mitotic trophoblast giant cells while mitotic lineages failed to proliferate and survive. In contrast to wild-type trophoblast giant cells, Mat1(-/-) cells exhibited a rapid arrest in endoreduplication, which was characterized by an inability to enter S phase. Additionally, Mat1(-/-) cells exhibited defects in phosphorylation of the C-terminal domain (CTD) of RNA polymerase II on both Ser5 and Ser2 of the heptapeptide repeat. Despite this, Mat1(-/-) cells demonstrated apparent transcriptional and translational integrity. These data indicate an essential role for Mat1 in progression through the endocycle and suggest that while Mat1 modulates CTD phosphorylation, it does not appear to be essential for RNA polymerase II-mediated transcription.

Keratinocyte growth factor is up-regulated by estrogen in the porcine uterine endometrium and functions in trophectoderm cell proliferation and differentiation

Keratinocyte growth factor (KGF) is expressed by uterine endometrial epithelial cells during the estrous cycle and during pregnancy in pigs, whereas KGF receptor is expressed in conceptus trophectoderm and endometrial epithelia. In particular, KGF expression in the endometrium is highest on day 12 of pregnancy. This corresponds to the period of maternal recognition of pregnancy in pigs, which is signaled by large amounts of estrogen secreted by conceptus trophectoderm acting on the endometrium. Our hypothesis is that estrogens of conceptus origin stimulate endometrial epithelial KGF expression, and, in turn, secreted KGF stimulates proliferation and differentiation of conceptus trophectoderm. To determine the factors affecting KGF expression in the uterus, endometrial explants from gilts on day 9 of the estrous cycle were cultured in the presence of 17beta-estradiol, catechol estrogens, or progesterone. 17beta-Estradiol stimulated the expression of KGF (P < 0.05), whereas catechol estrogens had no effect (P > 0.05). Between days 9 and 15 of pregnancy, proliferating cell nuclear antigen was abundant in conceptuses, but was barely detectable in uterine endometrial epithelia. To determine the effects of KGF on conceptus trophectoderm, porcine trophectoderm (pTr) cells were treated with recombinant rat KGF (rKGF). rKGF increased the proliferation of pTr cells (P < 0.01) as measured by [(3)H]thymidine incorporation. rKGF elicited phosphorylation of KGF receptor and activated the mitogen-activated protein kinase (ERK1/2) cascade in pTr cells. pTr cell differentiation was affected by rKGF, because it increased expression of urokinase-type plasminogen activator, a marker for differentiation in pTr cells. Collectively, these results indicate that estrogen, the pregnancy recognition signal from the conceptus in pigs, increases uterine epithelial KGF expression, and, in turn, KGF stimulates the proliferation and differentiation of conceptus trophectoderm.

Isolation of fetal cells from the maternal circulation: prospects for the non-invasive prenatal diagnosis

The research into non-invasive and invasive prenatal diagnostic techniques developed almost in parallel. On the one hand the need was arising to ensure the birth of normal progeny in all cases, while on the other, it was not possible to eliminate the abortion risks connected with the invasiveness of amniocentesis (risk of abortion 1/200), chorion villi sampling, (risk of abortion 2%) and funicolocentesis (risk of abortion 3-4%). One of the first researchers in the non-invasive field was Adinolfi who published the earliest data in 1974 on the possibility of detecting three types of fetal cells in the maternal circulation using flow cytometry. Adinolfi suggested the possibility of using fetal cells present in the maternal circulation for prenatal diagnosis of chromosome or biochemical anomalies. Our review takes into consideration the latest methodological and technical progress in relation to the study of fetal cells in maternal circulation, without considering cells present in the endocervical canal where from the 8th week of pregnancy it is only possible to obtain trophoblast cells. This technique has since been abandoned due to the scarcity of cellular material available, the greater risk of contamination by cells of maternal origin, and also because the recovery of the cells is unpredictable, despite their potential use for the early non-invasive diagnosis of sex. The following issues are addressed in this review: the characterization of the fetal cell types present in the maternal circulation, the methods of their separation and enrichment, and the methods of genetic diagnostics applied.

Insulin-like growth factor-binding protein 1 stimulates human trophoblast migration by signaling through alpha 5 beta 1 integrin via mitogen-activated protein Kinase pathway

A highly migratory subpopulation of the human placental trophoblast, known as the extravillous trophoblast (EVT), invades the uterus and its vasculature, to establish adequate exchange of key molecules between the maternal and fetal circulations. During their formation, EVT cells selectively acquire alpha 5 beta 1 integrin. We had shown that alpha 5 beta 1 is required for their migratory function, and that EVT cell migration is stimulated by insulin-like growth factor-binding protein (IGFBP)-1 produced by the uterine decidua. The present study examined whether this stimulation is dependent on binding of the Arg-Gly-Asp (RGD) domain of IGFBP-1 to an RGD binding site on the alpha 5 beta 1 integrin, followed by activation of focal adhesion kinase (FAK) and stimulation of the mitogen-activated protein kinase (MAPK) pathway. IGFBP-1 treatment increased migration of EVT cells, whereas an anti-alpha 5 beta 1 integrin antibody blocked migration regardless of IGFBP-1 treatment. Migration stimulation by IGFBP-1 was abrogated by pretreatment with a Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), but not a Gly-Arg-Gly-Glu-Ser-Pro (GRGESP) hexapeptide, and by mutation of the RGD domain of IGFBP-1 to Trp-Gly-Asp (WGD). IGFBP-1 treatment caused a rapid localization of immunoreactive FAK to cellular lamellipodia, a rapid increase in phosphorylation of FAK and extracellular-signal regulated kinases 1 and 2. Preincubation of EVT cells with Herbimycin A, a tyrosine kinase inhibitor, abrogated IGFBP-1 effects; whereas an MAPK kinase inhibitor, PD 98059, reduced migration regardless of IGFBP-1 treatment. These results indicate that IGFBP-1 stimulation of EVT cell migration occurs by binding of its RGD domain to the alpha 5 beta 1 integrin, leading to activation of FAK and stimulation of MAPK pathway.

Fetal cells in transcervical samples at an early stage of gestation

Several investigations are in progress with the aim of performing prenatal diagnosis of inherited disorders by noninvasive or minimally invasive techniques. The most important approaches are based on the detection of fetal nucleated cells in maternal blood, the analysis of fetal DNA present in maternal plasma, and the identification and isolation of fetal trophoblastic cellular elements shed into the uterine cavity and the endocervical canal. In this review, we discuss the methods that have been employed for the collection of the transcervical samples at an early stage of gestation and the techniques used for the identification of fetal cells. We also report the results of using endocervical cells for the detection of fetal chromosomal disorders by fluorescent in-situ hybridization and for performing prenatal diagnosis of fetal Rh(D) phenotypes. Recent investigations have also shown that--after the isolation of trophoblastic cells from maternal contaminants by micromanipulation--transcervical samples can be employed for the prenatal diagnosis of single gene defects, such as those causing thalassemia and sickle cell anemia. Although the present results are promising, further investigations are required to demonstrate the feasibility of performing accurate diagnosis of fetal diseases by this minimally invasive approach in all transcervical samples retrieved at an early stage of gestation.

Human trophoblast invasion and spiral artery transformation: the role of PECAM-1 in normal pregnancy, preeclampsia, and fetal growth restriction

During early human pregnancy extravillous cytotrophoblasts invade the uterus and spiral arteries transforming them into large vessels of low resistance. Failure of trophoblast invasion and spiral artery transformation occurs in preeclampsia and fetal growth restriction (FGR); these processes are not well understood. Recent studies have suggested that cytotrophoblasts that invade spiral arteries mimic the endothelial cells they replace and express PECAM-1. It was also reported that in preeclampsia, cytotrophoblasts fail to express PECAM-1 and that failure to express endothelial cell adhesion molecules may account for failed trophoblast invasion. Despite the possible importance of adhesion molecules in trophoblast invasion, no study has systematically investigated the expression of PECAM-1 in the placental bed throughout the period of invasion, particularly in the myometrial segments where the key failure occurs. There are no studies on PECAM-1 expression in the placental bed in FGR. We have examined the expression of PECAM-1 in placental bed biopsies and placentas from 8 to 19 weeks of gestation and in the placenta and placental bed in the third trimester in cases of preeclampsia, FGR, and control pregnancies. PECAM-1 was expressed on endothelium of vessels in the placenta and placental bed but not by villous or extravillous trophoblasts in normal or pathological samples. These findings do not support a role for PECAM-1 in normal invasion or in the pathophysiology of preeclampsia or FGR.

Murine ectoplacental cone-derived trophoblast cells express chemokine receptors

Chemokine receptors (CCRs) have been shown to regulate T cell migration and differentiation as well as the establishment of Th1/Th2 bias. Furthermore, T cells and T cell products are essential to trophoblast development. Thus, postulating that chemokines as well as their receptors may be expressed by trophoblast to move T cells into an interaction with the feto-placental unit, we examined whether CCRs are expressed during the early stages of ectoplacental cone (EPC) formation. For this, murine EPC-derived trophoblast were examined for their ability to express CCRs constitutively or inducible by interferon-gamma (IFN-gamma). Immunofluorescence experiments on EPC-derived trophoblast cells showed that CCR3, CXCR4 and CCR5 are significantly expressed. IFN-gamma accelerated the mobilization of intracellular pools of CCR molecules during early cell culture periods (2-6 h) and, in most cases, increased their expression on EPC-derived trophoblast cells. CCR activity could be detected in the culture supernatants of these cells, inversely proportional to cell surface expression, suggesting the existence of rapid endocytosis and recycling mechanisms. This finding indicates that the level of intracellular CCRs may partly be determined in the extracellular matrix, an event that could play an important role towards neutralization of specific T cell/trophoblast interactions during early stages of pregnancy and protect the fetus against harmful maternal immune responses.

[Detection of fetal cells in maternal blood: myth or reality?]

Fetal cells exist in maternal blood and can be utilized for prenatal diagnosis. These cells are present from the sixth week of gestation, with frequency increasing as gestation advances, to many years after the birth. Enrichment of trophoblast cells, erythroblasts and lymphocytes was performed with various density gradient techniques and either magnetic activated or fluorescent activated sorting techniques. The abnormalities were detected by fluorescent in-situ hybridation (FISH) with chromosome-specific DNA probes for the detection of trisomy 21, trisomy 18, Klinefelter syndrome 47 XXY, or by polymerase chain reaction (PCR) for the detection of fetal sex, certain Mendelian disorders (as beta-globin mutations), HLA polymorphisms and fetal Rhesus D blood type. However others studies were necessary to determine the sensitivity and specificity of this technique as a noninvasive alternative to conventional methods of prenatal cytogenetic diagnosis.

Capacity for hormone production of cultured trophoblast cells obtained from placentae at term and in early pregnancy

PROBLEM

There is an increased doubt about the identity of isolated cytotrophoblast cells at term. Therefore, we compared pregnancy serum levels of three hormones [human placental lactogen (hPL), human chorionic gonadotropin (hCG), and leptin] with the capacity for hormone production of early placentae [EP; 8-13 weeks of gestation (WG)] and term placentae (TP; 38-42 WG).

METHODS

Serum levels of these hormones were determined in 15 paired maternal (7-41 WG) and fetal (37-41 WG) samples. Cytotrophoblast cells were isolated from term (TP; 38-42 weeks) and early (EP; 8-13 weeks) placentae by enzymatic digestion and subsequent purification on a Percoll gradient. These cells were cultured for 6 days. The production of the hormones hPL, hCG, and leptin was determined as release during culture + cell content after culture - cell content before culture.

RESULTS

Serum levels (mean +/- SD; n = 15) at 7-12 and 37-41 WG were 89,652 +/- 21,431 and 13,620 +/- 5854 mIU/ml for hCG, 400 +/- 182 and 7088 +/- 2030 ng/ml for hPL, and 12,675 +/- 4266 and 32,236 +/- 10,961 pg/ml for leptin, respectively. For cultured cells from EP and TP, hCG and hPL showed different patterns of release during the first 2-3 days. While the release of these two hormones by EP cytotrophoblast cells continued during 6 days in culture, their concentrations reached a plateau for TP cytotrophoblasts between 4 and 6 days. Leptin was undetectable (< 15 pg/ml) in TP cell cultured media, while for EP all three hormones showed the same release profiles. Production calculated for 30,000 TP trophoblast cells cultured for 6 days (n = 8) was 2-31 mIU for hCG and 0.5-2 ng for hPL. For EP (n = 11), it was 50-1070 mIU for hCG, 15-323 ng for hPL, and 137-580 pg for leptin. Net synthesis of hCG and hPL for TP was > 10-fold and < 1-fold, respectively. In contrast, the production of all three hormones for EP was at least 100 times the initial cell content.

CONCLUSIONS

These results demonstrate that trophoblasts from early pregnancy show much higher production rates of hCG, hPL, and leptin than at term. However, the in vitro findings are difficult to be reconciled with the different serum concentrations of the two hormones hPL and leptin observed during the course of pregnancy.

Smads in human trophoblast cells: expression, regulation and role in TGF-beta-induced transcriptional activity

Smad proteins have recently been shown to be downstream signaling molecules that transduce TGF-beta signals from cell surface to the nucleus. To determine the mechanisms of TGF-beta action in human trophoblast cells, we investigated the expression and regulation of Smad2,3,4, and 7 mRNAs in a normal trophoblast cell line, NPC, and a cell line derived from choriocarcinoma, JEG-3. Messenger RNAs for Smad2,3,4 and 7 were detected in both NPC and JEG-3 cells. TGF-beta1 induced modest increases in Smad2 and Smad4 mRNA levels without affecting Smad3 mRNA expression in both cell lines. Significant increases in Smad7 mRNA levels in both NPC and JEG-3 cells following TGF-beta1 treatment were observed. TGF-beta1 also induced promoter activity of the Smad7 gene, indicating a direct effect at the level of gene transcription. The transcriptional activity of TGF-beta was examined in JEG-3 cells using two TGF-beta responsive reporter constructs, p3TP-Lux and pAR3-Lux. We found that Smad3 and to a lesser extent, Smad2 and Smad4, enhanced, while Smad7 inhibited, TGF-beta1-induced transcriptional activities. The basal and TGF-beta1-induced transcription can be blocked by overexpression of a dominant negative TGF-beta type II receptor. Taken together, these findings demonstrate that in human trophoblast cell lines, the Smad pathway involved in TGF-beta signal transduction is functional and that TGF-beta plays an autocrine role in regulating gene expression.

Mechanisms for the transport of unconjugated bilirubin in human trophoblastic BeWo cells

To evaluate mechanisms that mediate passage of unconjugated bilirubin (UCB) across placenta, the transport of [3H]UCB was studied in the human trophoblastic, BeWo cell line. When plotted against the unbound UCB concentration [Bf], uptake exhibited saturative kinetics with a similar apparent Km ( approximately 30 nM) for BeWo cells grown either in polarized (Transwell) or non-polarized fashion (dish). UCB release from cells, but not uptake, was inhibited by sulfobromophthalein but not by taurocholate, and almost abolished by MK571, a specific inhibitor of the activity of multidrug resistance-associated proteins (MRPs). MRP1 and MRP5 were both present in BeWo cells and the expression of MRP1, but not MRP5, was markedly higher in polarized cells. These data indicate that UCB is taken up from the fetal circulation by a still undefined, saturative process not shared by other organic anions and is then excreted to maternal circulation by proteins of the MRP family.

Automated quantitation of cell-mediated HIV type 1 infection of human syncytiotrophoblast cells by fluorescence in situ hybridization and laser scanning cytometry

Infection of human placental syncytiotrophoblast cells with HIV requires direct contact with infected leukocytes. In vitro investigations into mechanisms regulating placental HIV transmission and into the development of therapeutic interventions have been hampered by difficulties inherent in quantitating HIV levels in cocultures of infected lymphocytes and adherent multinucleated syncytiotrophoblast cells. Here, we have used fluorescence in situ hybridization (FISH) for the direct detection of HIV-1 RNA within syncytiotrophoblast cells combined with laser scanning cytometry (LSC) to quantitate HIV levels exclusively in the syncytiotrophoblast cells. HIV-1-infected lymphocytic MOLT-4 cells were cocultured with primary human syncytiotrophoblast cells. Lymphocytic cells were identified with an anti-vimentin antibody and Cy5. HIV RNA was localized by in situ hybridization, using a digoxigenin-labeled riboprobe detected by Oregon Green, and nuclei were stained with 7-aminoactinomycin D. The three-color cocultures were analyzed by LSC to remove unwanted cell populations and quantitate HIV expression levels. The total HIV RNA level (green fluorescence integral) in each colony was normalized for cell size by dividing by the total DNA content (red fluorescence integral). The nuclear-normalized fluorescence integral was 2.3 times higher in infected cocultures than in uninfected cultures. When cocultures were incubated with 10 microM AZT, the green/red fluorescence integral value was significantly lower than that of cocultures incubated in the absence of AZT, corresponding to a 78% reduction in fluorescence. Laser scanning cytometry can be used to quantitate cell-mediated HIV infection in syncytiotrophoblast cells and should allow drug assessment studies and studies aimed at understanding the mechanism of virus entry into trophoblast cells to be carried out.

Developmental regulation of morphological differentiation of placental villous trophoblast in the baboon

The present study determined whether morphological differentiation of placental villous cytotrophoblasts into syncytiotrophoblast during primate pregnancy was developmentally regulated and whether oestrogen has a role in this process. Placental volumetric composition of the cytotrophoblast and syncytiotrophoblast was determined by the test-point counting method on days 45-54, 60, 100, and 170 of gestation (term=184 days) in untreated baboons, on day 60 after placental oestrogen production was prematurely elevated by administration of aromatizable androstenedione or oestradiol, and on day 170 after oestrogen production was suppressed by administration of aromatase inhibitor CGS 20267. Cytotrophoblast and syncytiotrophoblast volumes and oestrogen levels increased (P< 0.01) with advancing gestation. Due to the rise in syncytiotrophoblast volume (12-fold) exceeded that of the cytotrophoblast (threefold), the mean (sem) ratio of syncytiotrophoblast and cytotrophoblast volumes increased (P< 0.001) from 3.4 (0.5) ml on day 60 to 12.1 (2.8) ml on day 170. Androstenedione administration elevated serum oestradiol levels threefold (P< 0.01) and increased the ratio of syncytiotrophoblast: cytotrophoblast volumes on day 60 by 50 per cent (P< 0.03) to that normally observed on day 100. However, the ratio of trophoblast volumes was unaltered in oestradiol-treated and CGS 20267-treated baboons. It is concluded that there is a developmental increase in morphological differentiation of the placental villous trophoblast during primate pregnancy and that androstenedione potentially via its conversion to oestrogen has a role in this process.

Expression of 11 beta-hydroxysteroid dehydrogenase isozymes and corticosteroid hormone receptors in primary cultures of human trophoblast and placental bed biopsies

Interconversion of active and inactive glucocorticoids, e.g. cortisol (F) and cortisone (E) is catalysed by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) which exists as two isoforms. We have used human placental bed biopsies and an in-vitro cytotrophoblast cell culture system to examine the expression and activity of the 11 beta-HSD isoforms along with that of the glucocorticoid and mineralocorticoid receptors (GR and MR). Immunohistochemistry localized 11 beta-HSD1 to decidualized stromal cells and 11 beta-HSD2 to villous cytotrophoblast, syncytiotrophoblasts and trophoblast cells invading the placental bed and maternal vasculature. In primary cultures of human cytotrophoblast, 11 beta-HSD2, GR and MR mRNA were expressed. Low levels of 11 beta-HSD1 mRNA were noted in these cultured cells, but could be explained on the basis of contaminating, vimentin-positive decidual stromal cells (< or =5%). Enzyme activity studies confirmed the presence of a high-affinity, NAD-dependent dehydrogenase activity (K(m) 137 nmol/l and V(max) 128 pmol E/h/mg protein), indicative of the 11 beta-HSD2 isoform. No reductase activity was observed. The presence of functional MR and GR was determined using Scatchard analyses of dexamethasone and aldosterone binding (MR K(d) 1.4 nmol/l B(max) 3.0; GR K(d) 6.6 nmol/l B(max) 16.2 fmol/ng protein). The expression of 11 beta-HSD1 in maternal decidua and 11 beta-HSD2 in adjacent trophoblast suggests an important role for glucocorticoids in determining trophoblast invasion. The presence of the MR within trophoblast indicates that some of the effects of cortisol could be MR- rather than GR-mediated.

Transforming growth factor beta may act as an autocrine-survival-promoting factor for transformed trophoblasts

Using five trophoblast cell lines of different differentiation status, we have shown that trophoblasts could constitutively release the transforming growth factor beta-1 (TGFbeta1), but not TGFbeta2. Treatment of the human tumorigenic, TL, and BeWo cells with a differentiating agent and a potent protein kinase C activator--the tumor-promoting agent--or the JEG-3 cells with cholera toxin--a potent cyclic adenosine 3':5'monophosphate (cAMP) inducer--or its analogue 8-bromo-cAMP, potentiates TGFbeta production, but the two signaling pathways appear to be mutually exclusive. Surprisingly, the JAR tell line failed to respond to either type of TGFbeta activator. Based on reverse transcriptase (RT)-polymerase chain reaction (PCR), it was found that only the JAR cell line expressed messenger ribonucleic acid for decorin, a natural inhibitor of TGFbeta, and none of the cell lines had detectable protein expression as determined by immunocytochemical studies. The tell number in cultures with decorin was invariably lesser than in those without decorin under serum-free conditions for all the cell lines tested. These results suggest that TGFbeta may act as an autocrine-survival factor for transformed trophoblasts by allowing the cells to survive longer under a microenvironment which is not favorable for growth. Lastly, our results indicate that decorin, acting in a paracrine manner, may also play an important negative regulatory role in the development of transformed trophoblasts by sequestering TGFbeta, thereby preventing its action.

Does nitric oxide play a role in the aetiology of pre-eclampsia?

Although progress has been made toward our understanding of the pathophysiology of pre-eclampsia, the precise aetiology of this disease still remains an enigma. One of the hallmarks of pre-eclampsia is a failure of the extravillous cytotrophoblast cells to invade and remodel the uterine spiral arterioles during the first trimester of pregnancy. Moreover, studies suggest that the cause of this disorder may be immunological in nature. Evidence is provided here suggesting that impaired trophoblastic invasion of the spiral arterioles may be linked to the altered immunological response associated with pre-eclampsia. Previous studies by Reister et al., 1999 demonstrated a direct relationship between macrophage infiltration of the myometrial segments of spiral arterioles and reduced trophoblastic invasion in pre-eclampsia. Also, it is well established that activated macrophages produce large amounts of nitric oxide (NO). Our present findings reveal that low concentrations of NO-mimetic drugs (glyceryl trinitrate and sodium nitroprusside) inhibit the ability of trophoblast cells to penetrate through reconstituted extracellular matrix (Matrigel). This inhibition is accompanied by a reduced expression of the cell surface urokinase receptor, a molecule important for invasion. These results suggest a possible mechanistic link between the aberrant macrophage infiltration associated with pre-eclampsia, and the maladapted uteroplacental arterioles that characterize the disease.

Altered placental structure induced by maternal food restriction in guinea pigs: a role for circulating IGF-II and IGFBP-2 in the mother?

Maternal feed restriction may restrict fetal growth in part indirectly by impairing placental functional development. Such actions could be mediated by the insulin-like growth factors (IGF), which are important modulators of placental growth and differentiation and more generally, are influenced by nutrient availability. While a role for the fetal IGF axis has been demonstrated, less is known of the influence, if any, of that in the mother. This study aimed to determine whether alterations in the maternal IGF axis and placental functional and structural development due to maternal food restriction are related. We therefore examined the associations between placental structural parameters, the ratios of maternal to fetal plasma glucose and fetal to maternal plasma urea concentration, and maternal circulating IGF-I, IGF-II and IGFBP-2 in ad libitum fed and food restricted (70-90 per cent of the ad libitum intake) pregnant guinea pigs. In mid-gestation, fetal weight (r = 0.65, P = 0.008, n = 17), volume of the maternal blood space (r = 0.58, P = 0.048, n = 17), and surface density of syncytiotrophoblast (r = 0.65, P = 0.023, n = 17), were positively correlated, and syncytiotrophoblast thickness was negatively correlated, with maternal plasma IGF-II concentration (r = -0.69, P = 0.014, n = 17). Late in gestation, fetal weight, placental weight and total exchange surface area in the placenta were each negatively correlated with maternal plasma IGFBP-2 concentration (all P < 0.01), while the arithmetic mean thickness of syncytiotrophoblast was positively correlated with maternal plasma IGFBP-2 concentration. Late in gestation, the ratio of maternal to fetal plasma glucose was positively correlated with fetal weight (r = 0.54, P = 0.038, n = 15) and the ratio of fetal to maternal plasma urea concentration was positively correlated with placental weight (r = 0.52, P=0.046, n=15). Maternal feed restriction reduced the ratio of maternal plasma IGF-II to IGFBP-2 in late gestation by 75 per cent (P = 0.001) and this ratio was positively correlated with fetal weight (r = 0.56, P = 0.01, n = 20), placental weight (r = 0.59, P = 0.006), placental diameter (r = 0.621, P = 0.003), placental volume (r = 0.57, P=0.009), weight of trophoblast (r = 0.51, P=0.037), weight of fetal capillaries (r = 0.49, P = 0.046), syncytiotrophoblast surface density (r = 0.611, P = 0.009) and negatively correlated with syncytiotrophoblast thickness (r = -0.55, P = 0.021). Our results suggest that in mid-pregnancy, maternal circulating IGF-II promotes placental structural development, while later in pregnancy, IGFBP-2 inhibits it, and their relative abundance and interaction strongly influences placental structure and function near term.

Inwardly rectifying K(+) current and differentiation of human placental cytotrophoblast cells in culture

Ion transport is important for driving nutrient transport across the syncytiotrophoblast and yet is poorly understood. We have examined K(+)currents under basal conditions in cultured cytotrophoblast cells, at various stages of differentiation, using the whole cell patch clamp technique. Cytotrophoblast cells were isolated from human term placenta and maintained in culture for up to 3 days. Cells were studied at four stages of progressive morphological differentiation: (i) mononuclear cells, (ii) mononuclear cells in aggregates, (iii) small multinucleate cells and (iv) large multinucleate syncytiotrophoblast-like cells. In the conditions of whole cell recording the only K(+) selective current identified in all cell types was a strong inwardly rectifying current which was sensitive to Ba(2+) and Cs(+). This current was unaffected by intracellular ATP whereas intracellular GTPgammas caused either run down of the current or activated a linear current. The characteristics of the current described are consistent with those of the inwardly rectifying K(+) channel Kir2.1. The inwardly rectifying K(+) current was observed in three out of 19 (16 per cent ) mononuclear cells, seven out of 21 (33 per cent ) mononuclear aggregates, eight out of 21 (38 per cent ) small multinucleate cells and 16 out of 19 (84 per cent ) large multinucleate cells. This inwardly rectifying K(+) current is likely to have an important role in determining net K(+) diffusion across the syncytiotrophoblast cell membrane, perhaps increasing in importance as the cells terminally differentiate.