Ontogeny of hepatocyte growth factor (HGF) and its receptor (c-met) in human placenta: reduced HGF expression in intrauterine growth restriction

Homeobox genes in the human placenta: Twists and turns on the path to find novel targets

Fetal growth restriction (FGR) is a clinically important human pregnancy disorder that is thought to originate early in pregnancy and while its aetiology is not well understood, the disorder is associated with placental insufficiency. Currently treatment for FGR is limited by increased surveillance using ultrasound monitoring and premature delivery, or corticosteroid medication in the third trimester to prolong pregnancy. There is a pressing need for novel strategies to detect and treat FGR at its early stage. Homeobox genes are well established as master regulators of early embryonic development and increasing evidence suggests they are also important in regulating early placental development. Most important is that specific homeobox genes are abnormally expressed in human FGR. This review focusses on identifying the molecular pathways controlled by homeobox genes in the normal and FGR-affected placenta. This information will begin to address the knowledge gap in the molecular aetiology of FGR and lay the foundation for identifying potential diagnostic and therapeutic targets.

Influential Serum Kinases (Non-sFlt-1) and Phosphatases in Preeclampsia-Systemic Review and Metanalysis

The early identification of women with an increased risk of preeclampsia (PE) is desirable, but apart from soluble fms-like tyrosine kinase-1 (sFlt-1), few biomarkers have previously been identified as relevant for predicting preeclampsia. Since kinases and phosphatases regulate critical biological processes and previous evidence suggests a potential role of these molecules in preeclampsia, we performed this systematic review and metanalysis. The objective was to determine if there are kinases and phosphatases whose serum levels are different between women with and without PE, being relevant biomarkers of PE. We followed the recommendations of Cochrane and the Preferred Reported Items for Systematic Reviews and Metanalysis (PRISMA) to perform this study. The MESH terms preeclampsia, kinases, phosphatases, angiopoietins, soluble tyrosine protein kinase receptor (sTIE2), and cellular-mesenchymal-epithelial transition factor (c-MET) were combined to find relevant articles in the PubMed, PROSPERO, and Cochrane databases. Then, a qualitative and quantitative analysis was performed in R Studio software. From 580 abstracts identified, 37 were included in the final analysis, which comprised 24,211 pregnant women (2879 with PE and 21,332 women without PE [HP]. The pooled analysis showed that serum creatine kinase (CK) (SMD: 2.43, CI 95% 0.25-4.62) was significantly higher in PE, whereas sTIE2 and anti-angiogenic factor soluble c-Met (sMet)were significantly lower in PE than in HP (SMD: -0.23, CI95% -0.37 to -0.09; and SMD:0.24, CI95% 0.01-0.47, respectively). Adenosine monophosphate-activated protein kinase (AMPK), angiopoietin-1 (ANG-1), angiopoietin-2 (ANG-2), the ratio angiopoietin-1/angiopoietin-2, acid phosphatase, and alkaline phosphatase were not different between women with PE and HP. In summary CK, sTIE2, and c-MET are relevant biomarkers of PE. It is desirable to incorporate them into current models for PE prediction to evaluate their utility as biomarkers.

Mesenchymal Stem/Stromal Cells from the Placentae of Growth Restricted Pregnancies Are Poor Stimulators of Angiogenesis

The extensively branched vascular network within the placenta is vital for materno-fetal exchange, and inadequate development of this network is implicated in the pregnancy disorder fetal growth restriction (FGR), where babies are born pathologically small. Placental mesenchymal stem/stromal cells (pMSCs) and placental macrophages both reside in close proximity to blood vessels within the placenta, where they are thought to promote angiogenesis via paracrine mechanisms. However, the relationship between pMSCs, macrophages and placental vascular development has not yet been examined. We aimed to determine if inadequate paracrine stimulation of placental vascular development by pMSCs and macrophages during pregnancy may contribute to the inadequate vascularisation seen in FGR. Media conditioned by MSCs from FGR placentae significantly inhibited endothelial tube formation, compared to conditioned media derived from normal pMSCs. Similarly, macrophages exposed to media conditioned by FGR pMSCs were less able to stimulate endothelial tube formation in comparison to macrophages exposed to media conditioned by normal pMSCs. While MSCs from normal placentae produce a combination of angiogenic and anti-angiogenic cytokines, there were no significant differences in the secretion of the anti-angiogenic cytokines thrombospondin-1, insulin growth factor binding protein-4, or decorin between normal and FGR pMSCs that could explain how FGR pMSCs inhibited endothelial tube formation. Together, these data suggest a dysregulation in the secretion of paracrine factors by pMSCs in FGR placentae. These findings illustrate how cross talk between pro-angiogenic cell types in the placenta may be crucial for adequate angiogenesis.

Establishment and differentiation of long-term trophoblast organoid cultures from the human placenta

The human placenta is essential for successful reproduction. There is great variation in the anatomy and development of the placenta in different species, meaning that animal models provide limited information about human placental development and function. Until recently, it has been impossible to isolate trophoblast cells from the human placenta that proliferate in vitro. This has limited our ability to understand pregnancy disorders. Generating an in vitro model that recapitulates the unique features of the human placenta has been challenging. The first in vitro model system of human trophoblast that could be cultured long term and differentiated to syncytiotrophoblast (SCT) and extravillous trophoblast (EVT) was a two-dimensional (2D) culture system of human trophoblast stem cells. Here, we describe a protocol to isolate trophoblast from first-trimester human placentas that can be grown long term in a three-dimensional (3D) organoid culture system. Trophoblast organoids can be established within 2-3 weeks, passaged every 7-10 d, and cultured for over a year. The structural organization of these human trophoblast organoids closely resembles the villous placenta with a layer of cytotrophoblast (VCT) that differentiates into superimposed SCT. Altering the composition of the medium leads to differentiation of the trophoblast organoids into HLA-G+ EVT cells which rapidly migrate and invade through the Matrigel droplet in which they are cultured. Our previous research confirmed that there is similarity between the trophoblast organoids and in vivo placentas in their transcriptomes and ability to produce placental hormones. This organoid culture system provides an experimental model to investigate human placental development and function as well as interactions of trophoblast cells with the local and systemic maternal environment.

Placental Protein 13 (Galectin-13) Polarizes Neutrophils Toward an Immune Regulatory Phenotype

Termed as galectin-13, placental protein 13 (PP13) is exclusively expressed in the placenta of anthropoid primates. Research on PP13 in normal and pathologic pregnancies show alteration of PP13 concentrations in pregnancy affected by preeclampsia or gestational diabetes. Galectins are also described as potent immunomodulators, and PP13 regulates T cell function in the placenta. Therefore, this study aims to investigate the effects of PP13 on neutrophils; a cell type often ignored in pregnancy, but present in the uterus and placenta from the early stages of pregnancy. Since neutrophil function is dysregulated during pathologic pregnancies, a link between PP13 and neutrophil activity is possible. We determined that PP13 reduces the apoptosis rate in neutrophils. Also, PP13 increases the expression of PD-L1 and production of HGF, TNF-α, reactive oxygen species (ROS), and MMP-9 in these cells. This phenotype resembles one observed in permissive tumor neutrophils; able to sustain tissue and vessel growth, and inhibit T cell activation. At the same time, PP13 does not alter all neutrophil functions, i.e., extrusion of neutrophil extracellular traps, degranulation, phagocytosis, and ROS production following bacterial exposure. PP13 seems to play an essential role in regulating the activity of neutrophils in the placenta by polarizing them toward a placental-growth-permissive phenotype.

Transactivation of Met signalling by semaphorin4D in human placenta: implications for the pathogenesis of preeclampsia

OBJECTIVE

The signalling of the receptor tyrosine kinase Met is critical in promoting trophoblast cell invasion, and the deficiency in HGF/Met signalling is associated with preeclampsia. The semaphorin family member semaphorin4D (sema4D) and its receptor Plexin-B1 have been reported to control tumour cell invasion by coupling with Met. We hypothesized that sema4D/Plexin-B1 may promote trophoblast invasion by activating Met, and downregulation of sema4D/Plexin-B1 may account for the deficiency in Met signalling in preeclamptic placenta.

METHODS

In this study, Met and Erk activation and the expression of sema4D/Plexin-B1 in normal and preeclamptic placentas were comparably measured. The role of sema4D in trophoblast cell invasion and tubulogenesis was examined in vitro using the Transwell invasion assay and tube formation assay in trophoblast-endothelial cell co-culture model.

RESULTS

Met, sema4D and Plexin-B1 co-localized in various subtypes of human trophoblast cells, including villous trophoblasts and extravillous trophoblasts (EVTs). In early-onset preeclampsia (E-PE) placentas, the phosphorylated Met and Erk as well as sema4D and Plexin-B1 were much lower than those in gestational week-matched preterm-labour (PTL) placentas. In human trophoblast HTR8/SVneo cell line, sema4D could promote Met and Erk phosphorylation as well as enhance trophoblast cell invasion and tubulogenesis with endothelial cells. Moreover, the effect of sema4D on HTR8/SVneo could be blocked by knocking down Met with specific siRNA.

CONCLUSION

The crosstalk between sema4D and Met could transactivate Met to promote trophoblast cell invasion and differentiation, and decreased expression of sema4D and Plexin-B1 may be responsible for the deficiency in Met signalling and the development of preeclampsia.

Expression of genes involved in inflammation and growth - does sampling site in human full-term placenta matter?

Objective To investigate the placental gene expression of substances in the inflammatory cascade and growth factors at nine different well-defined sampling sites in full-term placentas from 12 normal weight healthy non-smoking women with an uncomplicated singleton pregnancy. Methods All placentas (six girls and six boys) were delivered vaginally. Quantitative real-time polymerase chain reaction was used to analyze toll receptor-2 and -4, interleukin-6 and -8, tumor necrosis factor-α, leptin, ghrelin, insulin-like growth factor-1 and -2, hepatocyte growth factor, hepatocyte growth factor receptor and insulin receptor (IR). Results The leptin gene and the IR gene showed higher expression in lateral regions near the chorionic plate compared to central regions near the basal plate (P = 0.028 and P = 0.041, respectively). Conclusion Our results suggest that the sampling site may influence the gene expression for leptin and IR in placental tissue obtained from full-term normal pregnancies. We speculate that this may be due to differences in placental structure and perfusion and may be important when future studies are designed.

HGF regulate HTR-8/SVneo trophoblastic cells migration/invasion under hypoxic conditions through increased HIF-1α expression via MAPK and PI3K pathways

Hepatocyte growth factor (HGF) is reported to be down-regulated in pregnancy complications like intrauterine growth retardation and preeclampsia, which are associated with abnormal trophoblast migration/invasion. In this study, role of HGF and associated signaling pathways has been investigated in HTR-8/SVneo trophoblastic cells migration/invasion under normoxia (20% O₂) and hypoxia (2% O₂). HTR-8/SVneo cells exposed to hypoxia showed increase in migration and invasion as compared to cells incubated under normoxic conditions. The migration/invasion under both normoxic and hypoxic conditions was further enhanced after treatment with HGF. Subsequent to treatment with HGF, a significant increase in expression of MMP2 & MMP3 under normoxia and MMP1 & MMP9 under hypoxia was observed. Treatment of HTR-8/SVneo cells with HGF under hypoxia also led to decrease in TIMP1. Treatment of the cells with HGF led to activation of mitogen activated protein kinases (MAPK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways. Inhibition of MAPK by U0126 and PI3K by LY294002 led to concomitant decrease in the HGF-mediated migration/invasion of HTR-8/SVneo cells. HGF treatment under hypoxia also led to a significant increase in hypoxia inducible factor (HIF-1α) expression. Additionally, inhibition of HIF-1α by siRNA led to decrease in HGF-mediated migration of HTR-8/SVneo cells under hypoxic conditions. Inhibition of HGF activated MAPK and PI3K signaling led to reduction in HIF-1α expression under hypoxia. In conclusion, HGF facilitates HTR-8/SVneo cell migration/invasion by activation of MAPK/PI3K signaling pathways and increased expression of MMPs. HIF-1α has a role in HGF-mediated increase in migration under hypoxic conditions.

Analysis of hepatocyte growth factor immunostaining in the placenta of HIV-infected normotensive versus preeclamptic pregnant women

OBJECTIVE

Hepatocyte Growth Factor (HGF) plays a role in the migration and morphogenesis of different cell types and tissues. Preeclampsia (PE) is associated with deficient trophoblast invasion and placental insufficiency; hence HGF production is expected to be compromised. This study therefore aimed to immunolocalize and morphometrically analyse placental HGF in normotensive versus PE pregnancies stratified by HIV status and gestational age.

STUDY DESIGN

Normotensive (N; n = 40) and preeclamptic (PE; n = 80) women were stratified by HIV status (HIV- and HIV+), and gestational age i.e. early onset of PE (EOPE; <34 weeks) and late onset of PE (LOPE; ≥34 weeks). Placental tissues were stained using conventional immunohistochemistry, performed using mouse anti-human HGF antibody. Morphometric image analysis was performed using Zeiss Axio-Vision software.

RESULTS

HGF was immuno-localized within the syncytiotrophoblast, cytotrophoblast, endothelial and fibroblast-like cell populations of both conducting and exchange villi. Based on pregnancy type, HGF immunoexpression within the conducting villi was significantly different between Nvs EOPE (p = 0.0372) and EOPE vs LOPE (p = 0.0006). Within the exchange villi, no significant difference of HGF immunostaining was noted between N vs EOPE and N vs LOPE. A down-regulation of HGF immuno-expression was observed in LOPE compared to other groups within both villi types, albeit non-significant. Based on HIV status, no significant difference in HGF immuno-expression was demonstrated between HIV- vs HIV + within the exchange and conducting villi. However, the expression of HGF in HIV- group was elevated in both villi types. Across the groups, a significant difference was found between N+ vs EOPE- (p  = 0.0207), EOPE+ vs LOPE- (p = 0.0036) and EOPE- vs LOPE- (p = 0.0016) of the conducting villi while no significant difference was found within the exchange villi.

CONCLUSION

This novel study demonstrates that HGF was two-fold higher in conducting compared to exchange villi irrespective of the pregnancy type. HIV infection does not influence HGF expression within the conducting and exchange villi. The HGF/c-MET receptor complex may modulate the ligand expression within the placenta.

Efficient Induction of Syncytiotrophoblast Layer II Cells from Trophoblast Stem Cells by Canonical Wnt Signaling Activation

The syncytiotrophoblast layer is the most critical and prominent tissue in placenta. SynT cells are differentiated from trophoblast stem cells (TSCs) during early embryogenesis. Mouse TSCs can spontaneously differentiate into cells of mixed lineages in vitro upon withdrawal of stemness-maintaining factors. However, differentiation into defined placental cell lineages remains challenging. We report here that canonical Wnt signaling activation robustly induces expression of SynT-II lineage-specific genes Gcm1 and SynB and suppresses markers of other placental lineages. In contrast to mouse TSCs, the induced SynT-II cells are migratory. More importantly, the migration depends on hepatocyte growth factor (HGF) and the c-MET signaling axis. Furthermore, HGF-expressing cells lie adjacent to SynT-II cells in developing murine placenta, suggesting that HGF/c-MET signaling plays a critical role in SynT-II cell morphogenesis during the labyrinth branching process. The availability of SynT-II cells in vitro will facilitate molecular understanding of labyrinth layer development.

•

Wnt is sufficient to induce SynT-II cells from trophoblast stem cells

•

Induced SynT-II cells are migratory and are independent on EMT

•

Hepatocyte growth factor/c-MET is essential for SynT-II cell migration

Conditioned medium from umbilical cord mesenchymal stem cells induces migration and angiogenesis

Umbilical cord mesenchymal stem cells (UC-MSCs) have been suggested as a candidate for various clinical applications, however, major limitations include the lack of organ-specific accumulation and low survival rates of transplanted cells. In the present study, it was hypothesized that the paracrine effects of UC‑MSCs may enhance stem cell-based tissue repair and regeneration by promoting the specific homing of stem/progenitor cells and the overall ability to drive them to the damaged area. UC-MSCs-derived conditioned medium (UC-CM) was analyzed using liquid chip and ELISA techniques. In vitro tube formation assays of human umbilical vein endothelial cells (HUVECs) and UC-MSCs were then performed to assess the angiogenic properties of UC-CM. Subsequently, UC-MSCs, HUVECs and fibroblasts were labeled with PKH26 for an in vivo cell migration assay. The expression levels of C-X-C chemokine receptor 4 (CXCR4), C-C chemokine receptor 2 (CCR2) and c-met were determined in the UC-MSCs, HUVECs and fibroblasts using reverse transcription-quantitative polymerase chain reaction and flow cytometry. UC-CM was incubated with or without antibodies, and the contribution of stromal cell-derived factor 1 (SDF-1), monocyte chemotactic protein 1 (MCP-1) and hepatocyte growth factor (HGF) on the migration of cells was investigated in vitro. The results demonstrated that UC-MSCs secreted different cytokines and chemokines, including increased quantities of SDF-1, MCP-1 and HGF, in addition to the angiogenic factors, vascular cell adhesion protein-1, interleukin-8, insulin-like growth factor-1 and vascular endothelial growth factor. The total lengths of the tubes were significantly increased in the UC-MSCs and HUVECs incubated in UC-CM compared with those incubated in Dulbecco's modified Eagle's medium. In vivo cell migration assays demonstrated that UC-CM was a chemotactic stimulus for the UC-MSCs and HUVECs. In vitro Matrigel migration and scratch healing assays demonstrated that UC-CM increased the migration of CXCR4-positive or/and CCR2-positive cells in a dose-dependent manner. In addition, different molecules were screened under antibody-based blocking migration conditions. The data revealed that the SDF-1/CXCR4 and MCP-1/CCR2 axes were involved in the chemoattractive activity of UC-CM and suggested that the effective paracrine factor of UC-CM is a large complex rather than a single factor. The results of the present study supported the hypothesis that UC-MSCs release soluble factors, which may extend the therapeutic applicability of stem cells.

c-Met-dependent multipotent labyrinth trophoblast progenitors establish placental exchange interface

The placenta provides the interface for gas and nutrient exchange between the mother and the fetus. Despite its critical function in sustaining pregnancy, the stem/progenitor cell hierarchy and molecular mechanisms responsible for the development of the placental exchange interface are poorly understood. We identified an Epcam(hi) labyrinth trophoblast progenitor (LaTP) in mouse placenta that at a clonal level generates all labyrinth trophoblast subtypes, syncytiotrophoblasts I and II, and sinusoidal trophoblast giant cells. Moreover, we discovered that hepatocyte growth factor/c-Met signaling is required for sustaining proliferation of LaTP during midgestation. Loss of trophoblast c-Met also disrupted terminal differentiation and polarization of syncytiotrophoblasts, leading to intrauterine fetal growth restriction, fetal liver hypocellularity, and demise. Identification of this c-Met-dependent multipotent LaTP provides a landmark in the poorly defined placental stem/progenitor cell hierarchy and may help us understand pregnancy complications caused by a defective placental exchange.

Homeobox genes and down-stream transcription factor PPARγ in normal and pathological human placental development

The placenta provides critical transport functions between the maternal and fetal circulations during intrauterine development. Formation of this interface is controlled by nuclear transcription factors including homeobox genes. Here we summarize current knowledge regarding the expression and function of homeobox genes in the placenta. We also describe the identification of target transcription factors including PPARγ, biological pathways regulated by homeobox genes and their role in placental development. The role of the nuclear receptor PPARγ, ligands and target genes in human placental development is also discussed. A better understanding of these pathways will improve our knowledge of placental cell biology and has the potential to reveal new molecular targets for the early detection and diagnosis of pregnancy complications including human fetal growth restriction.

Preeclampsia is associated with an elevation of plasma sMet concentrations in the second trimester

OBJECTIVE

The aim of this study was to investigate the association between anti-angiogenic factor soluble c-Met (sMet) concentrations in maternal plasma and the risk of preeclampsia.

METHODS

The pregnant women included in this study (1) had subsequent preeclampsia (n = 52) and were compared to normal controls (n = 104) at the time of amniocentesis (15-20 weeks); and (2) had preeclampsia (n = 63) and were compared to normal controls (n = 112) at the time of diagnosis of preeclampsia (29-40 weeks). sMet concentrations were measured by ELISA. Non-parametric statistics were used for analysis.

RESULTS

Maternal plasma sMet concentrations were significantly higher in both women with subsequent preeclampsia (median: 1372.7 ng/ml versus 1100.5 ng/ml; p = 0.036) and women with preeclampsia (median: 1651.9 ng/ml versus 1364.7 ng/ml; p < 0.001) than in the controls. After adjusting for potential confounding factors, the risks of developing preeclampsia were as follows: adjusted odds ratio 2.5 (95% confidence interval, 1.2-5.2; p = 0.016) for second trimester sMet concentration with a cut-off value of 1223.5 ng/ml and 4.4 (95% confidence interval, 2.2-9.1; p < 0.001) for third trimester sMet concentration with a cut-off value of 1460.3 ng/ml.

CONCLUSION

Elevated maternal plasma sMet concentrations were independently associated with the increased risk of preeclampsia.

Hepatocyte growth factor regulates HLX1 gene expression to modulate HTR-8/SVneo trophoblast cells

BACKGROUND

Paracrine signaling of the hepatocyte growth factor (HGF) cytokine plays an important role in survival and invasion ability of placental trophoblasts. However, the intracellular factors and biological pathways underlying these responses remain unclear.

METHODS

This study investigated whether HGF affected the expression of homeobox gene HLX1, which is principally expressed in reproductive tissues and in some immune cells, and evaluated the implications of such in the HGF-induced human trophoblast cell line HTR-8/SVneo.

RESULTS

HGF was found to up-regulate both HLX1 mRNA and protein levels. Transient transfection of small interfering RNA (siRNA) targeting HLX1 abrogated its induction by HGF. Functionally, HLX1 siRNA not only reduced the growth and invasion capacities of HTR-8/SVneo cells at the basal level, but also inhibited these responses induced by HGF treatment.

CONCLUSIONS

HLX1 is an essential downstream signaling component of HGF that leads to growth and invasiveness of trophoblast cells.

The role of homeobox genes in the development of placental insufficiency

Intrauterine growth restriction (IUGR) is an adverse pregnancy outcome associated with significant perinatal and pediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. While a number of maternal, fetal and environmental factors are known causes of IUGR, the majority of IUGR cases are of unknown cause. These IUGR cases are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in IUGR associated with placental insufficiency is therefore of increasing importance. Here, we review our understanding of transcriptional control of normal placental development as well as human IUGR associated with placental insufficiency. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis and clinical management of IUGR associated with placental insufficiency.

The impact of compositional topography of amniotic membrane scaffold on tissue morphogenesis of salivary gland

Amniotic membrane (AM) has been widely used in the reconstruction of oral epithelial defects. However, whether it is also effective in facilitating tissue formation of salivary gland, an appendix of oral epithelia, has never been explored. To investigate the effects and the underlying mechanism of AM on salivary gland morphogenesis, murine fetal submandibular gland (SMG) explants were cultured on different preparations of AM scaffolds. It was found that, on AM stromal scaffold, SMG demonstrated well-developed branching morphogenesis. Nonetheless, on AM epithelial scaffold, SMG epithelial cell converted to a spindle-shape, lost intercellular connection, changed cytoskeletal organization, and exhibited scattering behaviors. Meanwhile, the integrity of SMG basement membrane was dismantled as well. However, when acellular AM epithelial scaffold was used, cultured SMG demonstrated organized morphology, indicating that AM epithelial component provided specific surface features for SMG morphogenesis. To further investigate AM scaffold morphogenetic effect, it was found hepatocyte growth factor (HGF), an epithelial scattering factor, was expressed abundantly in cultivated AM epithelia. After blocking HGF function of AM, cultured SMG regained branching activity, reorganized cell adhesion and subcellular organization, and reproduced basement membranes. Therefore, AM-derived bioactive factor profoundly influences cell behaviors and structure formation of SMG. Together, this study showed that compositional topography of AM scaffold is important in affecting SMG morphogenesis. By understanding the effects of AM scaffold on SMG morphogenesis, it provides important information for rationally designing and fabricating AM scaffold for salivary gland regeneration.

Calcium signaling in placenta

The placenta sustains the developing fetus throughout gestation and its major functions include nutrition, gas and waste exchange via a variety of passive or active mechanisms. Up to 30 g of calcium (Ca(2+)) actively crosses the trophoblast layer during human pregnancy. The Ca(2+) ion not only plays an important role for skeletal development but is also an essential second messenger. This review is intended to highlight the implications of Ca(2+) signaling during reproduction and specifically placentation. Initially, a Ca(2+) wave induces fertilization of the oocyte. The intracellular Ca(2+) concentration is key for the blastocyst implantation, proper placental development and function. Current knowledge of many proteins involved in placental Ca(2+) regulation and their function in pathologic conditions is largely limited. Recent studies, however, point to alterations in Ca(2+) homeostasis in placental pathologies such as pre-eclampsia (PE) and intrauterine growth restriction (IUGR). A broader understanding of the role of Ca(2+) signaling during human reproduction may offer insight into impaired pregnancy outcomes.

Plasma level of soluble c-Met is tightly associated with the clinical risk of preeclampsia

OBJECTIVE

The objective of the study was to examine the relevance of the soluble form c-Met (sMet) with the clinical risk for severe preeclampsia.

STUDY DESIGN

This prospective case-control study was performed by using plasma derived from 44 preeclamptic and 51 uncomplicated pregnant women. Plasma concentration of sMet was measured with specific enzyme-linked immunosorbent assay, and the predictive values were determined based on the receiver-operating characteristic (ROC) curves analysis.

RESULTS

Plasma s-Met level in normal pregnant women changed in a gestation-dependent manner, peaking at weeks 19-24. In women with severe preeclampsia, the circulating sMet level was significantly lower than that in the gestational stage-matched controls during gestational weeks 15-30. The ROC curve analysis revealed a significant correlation between plasma sMet level and the risk of developing severe preeclampsia.

CONCLUSION

Plasma sMet could serve as a potential biomarker for predicting severe preeclampia at early second trimester of pregnancy.

The cytotrophoblast layer of human chorionic villi becomes thinner but maintains its structural integrity during gestation

Chorionic villi in the human placenta serve as essential structures in fetomaternal exchanges. According to the embryology and placentology literature, during the first trimester, the cytotrophoblast (CTB) layer that is subjacent to the syncytiotrophoblast (STB) and supported by a basal lamina is nearly complete, but later, it becomes discontinuous. In the present study, we investigated the structural integrity of the CTB layer in the normal villous tree by advanced microscopy techniques using an antibody to hepatocyte growth factor (HGF) activator inhibitor type 1 (SPINT1), a potent inhibitor of HGF activators expressed exclusively on villous CTB. In full-term placenta, the cell surface of the CTB layer was spread over the basal lamina but was not interrupted. Morphometric analysis showed that throughout the villous tree, 80% of the continuity of the CTB layer of full-term placenta and 90% of that of first-trimester placenta were preserved. Gestation was accompanied by unique structural change in the basal domain of the trophoblast layer. The initially cuboidal-shaped CTB cells were transformed to flat cells with many cellular processes that, together with those of the adjacent STB, eventually covered the trophoblast basal lamina in a complex network of interdigitations. In addition, the expression levels of SPINT1, ST14, HGF, and MET mRNAs in the villous tree increased over the course of gestation. These results suggest that the structural integrity of the SPINT1-positive CTB layer may play an important role in villous differentiation and in maintenance of the villous tree via the HGF signaling system during gestation.

R-spondin3 is required for mouse placental development

Mouse R-spondin3 (Rspo3) is a member of the R-spondin protein family, which is characterized by furin-like cysteine-rich domains and a thrombospondin type 1 repeat. Rspo3 has been proposed to function as a secretory molecule that promotes the Wnt/beta-catenin signaling pathway. We generated mice bearing a mutant Rspo3 allele in which a lacZ-coding region replaced the coding region of the first exon. The homozygous mutant mice died at about embryonic day 10, due to impaired formation of the labyrinthine layer of the placenta. Rspo3 was expressed in the allantoic component of the labyrinth. In the homozygous mutant placentas, fetal blood vessels did not penetrate into the chorion, and expression of Gcm1, encoding the transcription factor glial cells missing-1 (Gcm1), was dramatically reduced in the chorionic trophoblast cells. These findings suggest a critical role for Rspo3 in the interaction between chorion and allantois in labyrinthine development.

Microarray analysis of BeWo and JEG3 trophoblast cell lines: identification of differentially expressed transcripts

Trophoblast cell lines are important research tools used as a surrogate for primary trophoblast cells in the study of placental function. Because the cellular origins of transformed trophoblasts are likely to be diverse, it would be of value to understand the unique and shared phenotypes of the cells on a global scale. We have compared two widely used cell lines, BeWo and JEG3, by microarray analysis in order to identify differentially expressed genes. Results indicated that approximately 2700 genes were differentially expressed between the cell lines, with principal differences observed in the biological processes of response to stress, cell adhesion, signal transduction, and protein and nucleobase metabolisms. These data suggest that BeWo and JEG3 cell lines, and perhaps other trophoblast cell lines, are sufficiently dissimilar from each other such that they will be differentially suited for specific experimental paradigms.

Homeobox gene HLX1 expression is decreased in idiopathic human fetal growth restriction

Fetal growth restriction (FGR) is a clinically significant pregnancy disorder in which the fetus fails to achieve its full growth potential in utero. Identifiable causes of FGR account for approximately 30% of cases, but the remainder are idiopathic and are frequently associated with placental malfunction. Previously, we isolated the homeobox gene HLX1 and provided evidence for a regulatory role in normal placental development. Here, we investigated whether placental HLX1 expression levels are changed in placentas from idiopathic FGR pregnancies. Real-time polymerase chain reaction quantitation showed reduced HLX1 mRNA levels with advancing gestation age (preterm control placentas, 27 to 35 weeks, 1.1 +/- 0.3, n = 13, versus term placentas 36 to 41 weeks, 0.74 +/- 0.02, n = 12, P < 0.005). FGR-affected placentas had significantly lower levels of HLX1 expression compared with gestation age-matched controls (0.36 +/- 0.07 versus 1.05 +/- 0.2, n = 25, P < 0.001). Immunoblotting with a rabbit polyclonal HLX1 antibody revealed reduced levels of HLX1 in FGR-affected placentas compared with controls (481.07 +/- 12.3 versus 2766.7 +/- 30.3, n = 10, P < 0.001). Immunohistochemistry showed a qualitative decrease in HLX1 immunoreactivity in FGR-affected term placentas compared with controls. This is the first demonstration that a homeobox transcriptional regulator shows altered expression in an important human placental disorder, suggesting that decreased HLX1 levels contribute to the abnormalities in placental developmental seen in idiopathic FGR.

Cigarette Smoking Induces Overexpression of Hepatocyte Growth Factor in Type II Pneumocytes and Lung Cancer Cells

We examined gene expression of hepatocyte growth factor (HGF) and HGF receptor (HGFR), or product of proto-oncogene c-met (c-met), in smokers and nonsmokers with adenocarcinoma (ADC) by suppression subtractive hybridization and microarray techniques. Expression of HGF and c-met was confirmed by RT-PCR. HGF content in the respective tumor mass and nontumor lung tissue was measured by ELISA. HGF in pathologic samples was localized by immunohistochemistry and in situ hybridization. Our results indicate that overexpression of HGFR was frequently detected in ADC cells, whereas overexpression of HGF was detected in alveolar type II (ATII) cells. Overexpression of HGF was correlated with cigarette smoking and tumor stages. In vitro, HGF expression was evaluated in isolated murine ATII cells and in 12 ADC cell lines, and we found that nicotine activated HGF expression in ATII cells and lung cancer cells.

Expression of hepatocyte growth factor/scatter factor receptor in IUGR fetuses' placentas: an immunohistochemical analysis

OBJECTIVE

We aimed to evaluate the expression sta tus of c-met, receptor for the hepatocyte growth factor (HGF), in the placentas of intrauterine growth retardation (IUGR) fetuses.

MATERIALS AND METHODS

Placentas were obtained during delivery from both third trimester normal and IUGR complicated pregnancies. Ultrasonographic estimation of fetal birth weight has been done and placentas of those under the fifth percentile for their gestational ages were enrolled in the study group. Eighteen fetuses with IUGR and 6 uncomplicated pregnancies were subjected to the study. Histological sections from placentas were immunohistochemically evaluated for the expression status of c-met.

RESULTS

Seventeen of the eighteen patients (94.4%) in the study group were found to have overexpression of the c-met while this figure was only 16.7% (1/6) in the control group (p < 0.0001). There was a strong statistically significant difference between the two groups regarding degree of c-met expression.

CONCLUSION

Our present findings suggest that c-met is an important cell membrane receptor in human placenta. Deregulation of the interaction between HGF and its receptor c-met during placentation may be the cause responsible for the growth retardation of the fetus due to the impaired placental functions.

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.

Human decidual production of hepatocyte-growth factor is not influenced by trophoblastic invasion in vivo

OBJECTIVE

To evaluate and compare production of hepatocyte growth factor (HGF) from human first-trimester implantation-site decidua (decidua basalis) and nonimplantation site decidua (decidua parietalis), and hence to determine whether human trophoblast invasion in vivo is associated with increased decidual HGF production.

DESIGN

Controlled prospective study.

SETTING

University hospital-based study.

PATIENT(S)

Ten women undergoing first-trimester termination of singleton pregnancy for psychosocial reasons without preexisting medical or gynecologic diseases.

INTERVENTION(S)

Decidual samples surgically excised and processed for paraffin-embedded immunohistochemistry and for reverse transcription-polymerase chain reaction (RT-PCR) studies.

MAIN OUTCOME MEASURE(S)

Protein and mRNA production in decidua basalis and decidua parietalis by immunohistochemistry and RT-PCR, respectively.

RESULT(S)

No statistically significant difference was found between decidua basalis and decidua parietalis in HGF protein or mRNA production. Immunohistochemical analysis (n = 9) showed a mean score of 3.28 +/- 2.37 for decidua basalis and 3.61 +/- 2.66 for decidua parietalis. Semiquantitative analysis of HGF mRNA expression between the two sites showed no statistically significant difference (n = 10)

CONCLUSION(S)

Human decidual production of HGF is not influenced by trophoblastic invasion in vivo.

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.

Hepatic function and physiology in the newborn

The liver develops from progenitor cells into a well-differentiated organ in which bile secretion can be observed by 12 weeks' gestation. Full maturity takes up to two years after birth to be achieved, and involves the normal expression of signalling pathways such as that responsible for the JAG1 genes (aberrations occur in Alagille's syndrome), amino acid transport and insulin growth factors. At birth, hepatocytes are already specialized and have two surfaces: the sinusoidal side receives and absorbs a mixture of oxygenated blood and nutrients from the portal vein; the other surface delivers bile and other products of conjugation and metabolism (including drugs) to the canalicular network which joins up to the bile ductules. There is a rapid induction of functions such as transamination, glutamyl transferase, synthesis of coagulation factors, bile production and transport as soon as the umbilical supply is interrupted. Anatomical specialization can be observed across the hepatic acinus which has three distinct zones. Zone 1 borders the portal tracts (also known as periportal hepatocytes) and is noted for hepatocyte regeneration, bile duct proliferation and gluconeogenesis. Zone 3 borders the central vein and is associated with detoxification (e.g. paracetamol), aerobic metabolism, glycolysis and hydrolysis and zone 2 is an area of mixed function between the two zones. Preterm infants are at special risk of hepatic decompensation because their immaturity results in a delay in achieving normal detoxifying and synthetic function. Hypoxia and sepsis are also frequent and serious causes of liver dysfunction in neonates. Stem cell research has produced many answers to the questions about liver development and regeneration, and genetic studies including studies of susceptibility genes may yield further insights. The possibility that fatty liver (increasingly recognized as non-alcoholic steatohepatitis or NASH) may have roots in the neonatal period is a concept which may have important long-term implications.

Plasma hepatocyte growth factor as a marker for small-for-gestational age fetuses

OBJECTIVE

To study the association between hepatocyte growth factor (HGF) levels and pregnancy outcome.

STUDY DESIGN

Hepatocyte growth factor levels were measured in 42 plasma samples between weeks 14 and 21 of gestation using an enzyme-linked immunosorbent assay (ELISA). Results were correlated to pregnancy outcome and Mann-Whitney U-test applied to study the differences.

RESULTS

Hepatocyte growth factor values in pregnancies that develop preeclampsia (n=12) were not significantly different from unaffected pregnancies (n=21, multiples of the median (MoM)=1.38, P=0.47). However, hepatocyte growth factor values were significantly elevated in pregnancies of small-for-gestational age (SGA) fetuses (n=9) compared to uncomplicated pregnancies (MoM=2.66, P<0.001).

CONCLUSION

Measurement of hepatocyte growth factor in peripheral blood between 14 and 21 weeks gestation may offer new possibilities in the early diagnosis and prediction of fetal birth weight but not of preeclampsia.

Hepatocyte Growth Factor Induced Human Trophoblast Motility Involves Phosphatidylinositol-3-Kinase, Mitogen-Activated Protein Kinase, and Inducible Nitric Oxide Synthase

Hepatocyte growth factor (HGF) increases human trophoblast motility and invasion, an effect which is abrogated when inducible nitric oxide synthase (iNOS) is inhibited. In this study we have investigated the pathways involved in the regulation of trophoblast motility. Both basal and HGF-stimulated motility of the extravillous trophoblast cell line, SGHPL-4, were inhibited in a dose-dependent manner by the phosphatidylinositol-3-kinase (PI3-kinase) inhibitor, LY294002. HGF-stimulated iNOS expression was also inhibited by LY294002 and direct activation of PI3-kinase, using the peptide 740Y-P, led to an increase in iNOS expression and cell motility. Pretreatment with rapamycin, which acts at a point distal to PI3-kinase activation, also inhibited basal and HGF-stimulated motility. Inhibition of the p42/p44 mitogen activated protein kinase (MAPK) pathway but not the p38 MAPK pathway had significant inhibitory effects on HGF-stimulated but not basal trophoblast motility. Inhibition of p42/p44 MAPK also inhibited HGF-induced iNOS expression. This data demonstrate that the PI3-kinase signaling pathway is involved in basal trophoblast motility and that both MAPK and PI3-kinase signaling pathways are important in HGF-stimulated motility and iNOS expression.

The ontogeny of 25-hydroxyvitamin D(3) 1alpha-hydroxylase expression in human placenta and decidua

In addition to its classical calciotropic effects, the active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a potent anti-proliferative/immunomodulatory secosteroid. The enzyme that catalyzes the synthesis of 1,25(OH)(2)D(3), 1alpha-hydroxylase (1alpha-OHase), is expressed in many human tissues, highlighting its possible role as an autocrine/paracrine activator of vitamin D. Immunohistochemical and RNA analyses were used to characterize the ontogeny of 1alpha-OHase expression in human placenta and decidua. Protein for 1alpha-OHase was detectable in trophoblast and decidua; the latter being stronger in decidualized stromal cells than macrophages, with no staining of lymphocytes. Quantitative reverse transcriptase-polymerase chain reaction was used to assess changes in mRNA expression for 1alpha-OHase at different gestations: first (mean, 9.1 +/- 1.5 weeks); second (mean, 14 +/- 1.8 weeks), and third trimester (mean, 39.3 +/- 2.5 weeks). 1alpha-OHase expression in decidua was approximately 1000-fold higher in first (95% confidence limits, 611 to 1376) and second (95% confidence limits, 633 to 1623) trimester biopsies when compared with the third trimester (95% confidence limits, 0.36 to 2.81) (both P < 0.001). In placenta, 1alpha-OHase expression was 80-fold higher in the first (range, 42 to 137) and second (range, 30 to 199) trimester when compared with third trimester biopsies (0.6 to 1.6) (both P < 0.001). Similar results were obtained by semiquantitative IHC. Parallel analysis of the receptor for 1,25(OH)(2)D(3) (vitamin D receptor) indicated that, as with 1alpha-OHase, highest levels of expression occurred in first trimester decidua. However, changes in vitamin D receptor mRNA expression across gestation were less pronounced than 1alpha-OHase. These spatiotemporal data emphasize the potential importance of 1alpha-OHase during early fetoplacental life and, in particular, suggest an autocrine/paracrine immunomodulatory function for the enzyme.

Comparative developmental anatomy of the murine and human definitive placentae

The placenta of eutherian mammals is a remarkable biological structure. It is composed of both zygote-derived and maternal cells, and mediates the complex interactions between the mother and the fetus that are necessary for fetal growth and survival. While the genetic basis of human placental development and function is largely unknown, its understanding is of immense clinical importance because placentopathies of unknown genetic aetiology are thought to be the cause of many types of pregnancy complications including unexplained miscarriage and intrauterine growth retardation. The mouse is the best-studied mammalian experimental genetic model system and research is not restricted by the inherent ethical and practical limitations associated with the human. As a result, knowledge about the genetic control of mouse placental development has expanded greatly in recent years. In order for this to be of benefit to medical practice, extrapolations from murine to human placentation have to be made. However, comprehensive comparisons of the placentae of these two species are rare. This review therefore compares the developmental anatomy of the placenta between humans and mice with emphasis on structures and cell types that might be analogous between the two species. This could be of particular benefit to mouse developmental geneticists who study placental development and have an interest in the possible clinical implications of their work.

Apoptosis and syncytial fusion in human placental trophoblast and skeletal muscle

Skeletal muscle fibers and placental villous trophoblast are the main representatives of syncytia in the human. Both syncytia are derived from fusion of mononucleated stem cells, show a high degree of differentiation, and have lost their generative potency. Consequently, for their growth both depend on fusion of additional stem cells. There is evidence that syncytial fusion is directly or indirectly related to apoptotic events: As early as in the differentiated stages of the mononucleated stem cells, initiation stages of the apoptosis cascade have been observed. After syncytial fusion progression of the cascade is retarded or blocked by a variety of mechanisms. In this review we emphasize the links between apoptosis cascade, differentiation pathways and syncytial fusion. It needs to be elucidated whether these processes simply take place in parallel, both temporally and spatially, or whether there are causal connections between apoptosis cascade and syncytial fusion. Based on recent data obtained for placental villous trophoblast, it is tempting to speculate that early molecular mechanisms of the apoptosis cascade are involved in differentiation and syncytial fusion. Data obtained in skeletal muscles support this assumption and reveal a considerable degree of homology in genesis, maintenance and turnover of both tissues.

Regulation of human cytotrophoblast morphogenesis by hepatocyte growth factor/scatter factor

In vitro morphogenesis of epithelial cells to form tube-like structures is regulated by hepatocyte growth factor-scatter factor (HGF/SF). The placenta is a rich source of HGF/SF, and its absence in mice has been shown to lead to impaired placental growth and embryonic death. There is no information in the literature regarding in vitro morphogenesis of human cytotrophoblasts or the effect of HGF/SF on this process. In this study, cytotrophoblasts were isolated from human placentae obtained from all three trimesters of gestation and cultured on the recombinant basement membrane matrix (Matrigel). Under these conditions, cytotrophoblasts participated in morphogenetic events including formation of spheroid-like structures, radial linear processes with branching, and invaded Matrigel and formed large, tube-like structures. The presence of a developing lumen was documented in the linear projections arising from spheroids and in the tube-like structures by both confocal and transmission electron microscopy. Immunohistochemistry was used to characterize the phenotype of the cells, and staining with anti-cytokeratin and anti-E-cadherin antibodies confirmed the presence of cytotrophoblasts in both the spheroids and tube-like structures. Recombinant HGF (rHGF) significantly increased the invasive activity of cytotrophoblasts isolated from the first and second (P < 0.001) and third trimesters (P < 0.01). In addition, rHGF significantly increased the percentage of spheroids with branching processes in the first and second trimesters (P < 0.05). Anti-HGF antibody inhibited both these effects in a dose-dependent manner, indicating the specificity of the above findings. This study provides new evidence indicating that HGF/SF regulates invasion and branching morphogenesis of cytotrophoblasts throughout gestation, with maximum effects in the first and second trimester. These findings may help to elucidate the importance of the reduced expression of HGF/SF identified in placentae from women with preeclampsia or intrauterine growth restriction and suggest that HGF/SF may serve as an important candidate in therapeutic intervention strategies.

Use of transgenic mice model for understanding the placentation: towards clinical applications in human obstetrical pathologies?

The mammalian embryo and fetus are unable to develop without a well-established, functional placenta. This transitory yet indispensable structure attaches the conceptus to the uterus and establishes the vascular connections necessary for nutrient and gaseous exchange between maternal and fetal compartments. Genetic targeting strategy allows the generation of mice lacking a specific gene. Such approaches reveal: (i) the high incidence of mutant embryonic or fetal death in utero, and (ii) the extraembryonic (placental) causes of these deaths. Due to the similarities presented between mouse and human placenta, we propose to use the potential of mouse targeting experiments as a model in order to understand human obstetrical pathologies. In this paper, we first review genes that have been demonstrated to be required in mice for implantation, choriovitelline and chorioallantoic placentation. Using examples (integrins, homeoboxs, hepatocyte growth factor or epidermal growth factor receptor...) we demonstrate the reality and efficiency of such an approach. Other candidate genes (receptor of leukemia inhibitory factor, Wnt2 or retinoic acid receptor alpha...) in order to understand, prevent and treat human obstetrical pathologies.

Placental development: lessons from mouse mutants

The placenta is the first organ to form during mammalian embryogenesis. Problems in its formation and function underlie many aspects of early pregnancy loss and pregnancy complications in humans. Because the placenta is critical for survival, it is very sensitive to genetic disruption, as reflected by the ever-increasing list of targeted mouse mutations that cause placental defects. Recent studies of mouse mutants with disrupted placental development indicate that signalling interactions between the placental trophoblast and embryonic cells have a key role in placental morphogenesis. Furthering our understanding of mouse trophoblast development should provide novel insights into human placental function.

Hepatocyte growth factor activator (HGF-A) and its zymogen in human placenta

HGF-activator (HGF-A) is a circulating serine protease known to be responsible for activation of hepatocyte growth factor (HGF). Active HGF is thought to be an important regulator of trophoblast growth. In vitro, HGF-A is produced via proteolytic cleavage of its zymogen by thrombin. Immunocytochemistry and Western immunoblotting were performed using human placental tissue from all three trimesters with an antibody that recognizes both HGF-A and its zymogen. Western immunoblotting revealed a 97 kDa band equivalent to the zymogen in placenta from all three trimesters. A smaller 34 kDa band equivalent to HGF-A was only seen in first and second trimester placenta. The anti-HGF-A/zymogen antibody demonstrated immunostaining in placental villi and membranes throughout gestation. Within first trimester villi immunostaining was strongest within the syncytio- and cytotrophoblast layers, but was also seen within stromal and endothelial cells. Likewise, in third trimester placenta the syncytio-cytotrophoblast layer showed the strongest immunoreactivity. In vitro, HGF can induce trophoblast DNA synthesis and the localization of HGF-A to the peri-villous trophoblast layer (which expresses c-met, the HGF receptor) suggests that it may be responsible for activation of pro-HGF at this site. This adds further weight to the hypothesis that HGF in vivo is an important regulator of trophoblast growth.

The hepatocyte growth factor/Met pathway in development, tumorigenesis, and B-cell differentiation

This article summarizes the structure, signal transduction and physiologic functions of the HGF/Met pathway, as well as its role in tumor growth, invasion, and metastasis. Moreover, it highlights recent studies indicating a role for the HGF/Met pathway in antigen-specific B-cell development and B-cell neoplasia.

A role for hepatocyte growth factor during early postimplantation growth of the placental lineage in mice

Hepatocyte growth factor (HGF) is implicated in placental development; hgfr and hgf null mutant embryos develop placental insufficiency and lethality at 11.5 days (E11.5) after fertilization. The function of HGF in placentation at implantation (E4.5) has not been studied. Using reverse transcription-polymerase chain reaction, we detected HGF receptor (HGFR) mRNA in preimplantation embryos and in cultured blastocyst outgrowths. HGFR protein was detected in trophoblast cells in blastocyst outgrowths. HGF mRNA was not detected at these stages but was detected in the uterus at E5.5. Using in situ hybridization, we detected HGF mRNA in the mesometrial uterus, near the embryo, from E6.5 through E8.5. At E8.5, HGFR mRNA was detected in the chorionic placenta, and HGF mRNA was detected in the allantois. The expression for HGF and HGFR suggested a maternal-to-embryonic communication before the development of the allantois. To test this, blastocyst outgrowths were cultured with HGF. HGF stimulated the outgrowth of trophoblasts in a time-dependent manner and stimulated the expression of proliferating cell nuclear antigen, but it did not scatter trophoblasts. HGF stimulated an increase in the trophoblast cell number, but caused a decrease in the total number of terminally differentiated trophoblasts expressing placental lactogen-1 protein. These data suggest that HGF stimulates the cell division, but not the differentiation, of trophoblast cells during implantation.