Platelet-derived soluble factors induce human extravillous trophoblast migration and differentiation: platelets are a possible regulator of trophoblast infiltration into maternal spiral arteries

Maternal Par4 and platelets contribute to defective placenta formation in mouse embryos lacking thrombomodulin

Absence of the blood coagulation inhibitor thrombomodulin (Thbd) from trophoblast cells of the mouse placenta causes a fatal arrest of placental morphogenesis. The pathogenesis of placental failure requires tissue factor, yet is not associated with increased thrombosis and persists in the absence of fibrinogen. Here, we examine the role of alternative targets of coagulation that might contribute to the placental failure and death of Thbd(-/-) embryos. We demonstrate that genetic deficiency of the protease-activated receptors, Par1 or Par2, in the embryo and trophoblast cells does not prevent the death of Thbd(-/-) embryos. Similarly, genetic ablation of the complement pathway or of maternal immune cell function does not decrease fetal loss. In contrast, Par4 deficiency of the mother, or the absence of maternal platelets, restores normal development in one-third of Thbd-null embryos. This finding generates new evidence implicating increased procoagulant activity and thrombin generation in the demise of thrombomodulin-null embryos, and suggests that platelets play a more prominent role in placental malfunction associated with the absence of thrombomodulin than fibrin formation. Our findings demonstrate that fetal prothrombotic mutations can cause localized activation of maternal platelets at the feto-maternal interface in a mother with normal hemostatic function.

MT1-MMP expression in first-trimester placental tissue is upregulated in type 1 diabetes as a result of elevated insulin and tumor necrosis factor-alpha levels

OBJECTIVE

In pregestational diabetes, the placenta at term of gestation is characterized by various structural and functional changes. Whether similar alterations occur in the first trimester has remained elusive. Placental development requires proper trophoblast invasion and tissue remodeling, processes involving matrix metalloproteinases (MMPs) of which the membrane-anchored members (MT-MMPs) such as MT1-MMPs are key players. Here, we hypothesize a dysregulation of placental MT1-MMP in the first trimester of type 1 diabetic pregnancies induced by the diabetic environment.

RESEARCH DESIGN AND METHODS

MT1-MMP protein was measured in first-trimester placentas of healthy (n = 13) and type 1 diabetic (n = 13) women. To identify potential regulators, first-trimester trophoblasts were cultured under hyperglycemia and various insulin, IGF-I, IGF-II, and tumor necrosis factor-alpha (TNF-alpha) concentrations in presence or absence of signaling pathway inhibitors.

RESULTS

MT1-MMP was strongly expressed in first-trimester trophoblasts. In type 1 diabetes, placental pro-MT1-MMP was upregulated, whereas active MT1-MMP expression was only increased in late first trimester. In isolated primary trophoblasts, insulin, IGF-I, IGF-II, and TNF-alpha upregulated MT1-MMP expression, whereas glucose had no effect. The insulin effect was dependent on phosphatidylinositol 3-kinase, the IGF-I effect on mitogen-activated protein kinase, and the IGF-II effect on both.

CONCLUSIONS

This is the first study reporting alterations in the first-trimester placenta in type 1 diabetes. The upregulated MT1-MMP expression in type 1 diabetes may be the result of higher maternal insulin and TNF-alpha levels. We speculate that the elevated MT1-MMP will affect placental development and may thus contribute to long-term structural alterations in the placenta in pregestational diabetes.

Lymphatic vessel dynamics in the uterine wall

During pregnancy, maternal uterine blood vessels undergo dramatic vascular remodeling. However, until now, little was known about whether the lymphatic circulation experiences similar changes and whether these vessels interact with placental cells that invade maternal tissue. Recent studies demonstrate that lymphatic vessels in the uterine wall are highly compartmentalized where their presence is mostly restricted to the deeper layers. In humans, this arrangement changes during pregnancy when extensive lymphangiogenesis occurs at the maternal-fetal interface. Placental cytotrophoblasts stimulate lymphatic growth in vivo and in vitro suggesting that they play a role in triggering pregnancy-induced decidual lymphangiogenesis. These data indicate that lymphatic vessels may have important functions at the implantation site during pregnancy.

Platelets are novel regulators of neovascularization and luteinization during human corpus luteum formation

The human corpus luteum is a unique endocrine organ that is periodically constructed from the ovulated follicle. During human corpus luteum formation, which is well known as a pathophysiological model for tissue remodeling, the precise mechanisms by which centripetal vascular development is regulated remain unknown. Recently platelets were reported to contain chemoattractive substances with the potential to induce endothelial migration. In this study, we examined the involvement of platelets in the early tissue remodeling process of the human corpus luteum. An immunohistochemical study demonstrated that considerable amounts of red blood cells and CD41-positive platelets were localized at extravascular sites among luteinizing granulosa cells after ovulation. Platelet deposition gradually decreased and became limited near the central cavity toward which microvessels were extending. Platelets were hardly observed in the midluteal phase when the vascular network had already been established. These platelets expressed CD62P/P-selectin and were colocalized with extracellular matrix, suggesting that platelets had been activated by the extracellular matrix. Progesterone production by luteinizing granulosa cells that were isolated from patients undergoing in vitro fertilization therapy was significantly promoted by direct contact with platelets during 4-d culture. Platelet-derived soluble factors induced spreading in granulosa cell morphology. These factors also increased the migration of human umbilical vein endothelial cells, whereas luteinizing granulosa cells attenuated platelet-induced endothelial cell migration. These findings lead us to propose the novel concept that platelets are regulators of endothelial cell migration and granulosa cell luteinization in the remodeling process of the human corpus luteum.

Fetal gene defects precipitate platelet-mediated pregnancy failure in factor V Leiden mothers

We describe a mouse model of fetal loss in factor V Leiden (FvL) mothers in which fetal loss is triggered when the maternal prothrombotic state coincides with fetal gene defects that reduce activation of the protein C anticoagulant pathway within the placenta. Fetal loss is caused by disruption of placental morphogenesis at the stage of labyrinth layer formation and occurs in the absence of overt placental thrombosis, infarction, or perfusion defects. Platelet depletion or elimination of protease-activated receptor 4 (Par4) from the mother allows normal placentation and prevents fetal loss. These findings establish a cause–effect relationship for the observed epidemiologic association between maternal FvL status and fetal loss and identify fetal gene defects as risk modifiers of pregnancy failure in prothrombotic mothers. Pregnancy failure is mediated by Par4-dependent activation of maternal platelets at the fetomaternal interface and likely involves a pathogenic pathway independent of occlusive thrombosis. Our results further demonstrate that the interaction of two given thrombosis risk factors produces markedly disparate consequences on disease manifestation (i.e., thrombosis or pregnancy loss), depending on the vascular bed in which this interaction occurs.

Expression of adhesion molecules during normal pregnancy

We review the available information regarding the role of adhesive molecules as potential participants in the complex events of fertilization, embryogenesis, implantation and placentation. Studies that specifically relate to the expression and modulation of adhesive molecules in fertilization, embryogenesis, and implantation have been identified in the literature and by Medline searches. Cell-cell and cell-extracellular matrix interactions play a critical role in various developmental processes and in the cascade of events that lead to implantation and to the normal development of the fetus during pregnancy. Adhesion molecules influence, directly or indirectly, numerous aspects of cell behaviour, cell migration, cell growth, cell survival, cell proliferation, angiogenesis, invasion and metastasis.

Management of thrombocytopenia in bone marrow failure: a review

The clinical course of many neoplastic and primary bone marrow diseases will result in cytopenias secondary to bone marrow failure or infiltration. Acute and chronic leukemias, the myelodysplastic syndromes (MDS), aplastic anemia, breast and prostate cancer, as well as other hematologic and solid tumors, all may lead to chronic, severe cytopenias. Management of anemia and neutropenia are well described in the medical literature. Less well detailed are management approaches for patients with chronic thrombocytopenia, with or without active bleeding. Severe thrombocytopenia presents many difficult management choices for caregivers, patients and their families, especially near the end of life. The use of platelet transfusions in this patient population presents complex issues; platelets are logistically more difficult to transfuse than red cells and carry risks including acute febrile episodes, alloimmunization, and infection. In this review, we discuss the association of chronic thrombocytopenia to serious bleeding and the role of various prophylactic and therapeutic interventions available to palliative care and hospice providers. Specifically, this review examines the following issues: What is the morbidity and mortality from chronic thrombocytopenia in the setting of cancer or other bone marrow failure states? Is there a role for prophylactic platelet transfusions in the palliative care setting, and if so, with what frequency of monitoring, and at what transfusion threshold? What is the impact of alloimmunization and how can it be minimized? What treatments are available besides, or in addition to, platelet transfusions for acute bleeding episodes?

Eph-ephrin A system regulates murine blastocyst attachment and spreading

Although numerous adhesion molecules are expressed on mammalian endometrial epithelial cells, there have not been any studies of a mechanism to prevent premature attachment of the embryo. In this study, we examined the possible involvement of Eph-ephrin interaction, which can induce repulsive forces. In mice, Eph A1, A2, and A4 were expressed on endometrial epithelial cells and ephrin A1-4 on blastocysts. Reverse transcriptase-polymerase chain reaction showed that mRNA expression of ephrin A1-4 on embryos transiently decreased around the implantation period. Immunohistochemistry demonstrated that the expression of Eph A1 on endometrial epithelial cells and ephrin A1 and A3 expression on embryos decreased at implantation sites. Recombinant Eph A1 reacted with cell the surface of ephrin A-bearing trophectoderm cells. Attachment assays using Eph A1-coated dishes showed that blastocyst attachment was reversibly inhibited by Eph A1. These findings suggest an important role of the Eph-ephrin A system in regulating the initial embryo-maternal contact during the cross-talk period that precedes embryo implantation.

Membrane-bound peptidases regulate human extravillous trophoblast invasion

During human placentation, the extravillous trophoblast (EVT) invades maternal decidua and spiral arteries. However, the precise regulatory mechanisms by which EVT invasion is induced toward maternal arteries or limited within the uterus have not been well characterized. Recently, we found that dipeptidyl peptidase IV, a membrane-bound cell surface peptidase that can degrade chemokines, including RANTES, was expressed on EVT that had already ceased invasion. Another cell surface peptidase, carboxypeptidase-M, was also detected on EVT including the endovascular trophoblast in the maternal arteries. The inhibition of these peptidases increased cell invasion of choriocarcinoma-derived JEG-3 cells. On the other hand, CCR-1, a chemokine receptor for RANTES, was specifically expressed on EVT that migrated toward maternal arteries, while RANTES enhanced invasion of EVT that were isolated from primary villous explant culture. Platelets, which secrete RANTES and other chemokines, were detected among the endovascular trophoblast, and platelets were shown to enhance invasion of cultured EVT. Furthermore, a novel membrane-bound cell surface peptidase, laeverin, was found to be specifically expressed on EVT at deep sites in the maternal decidua. These findings suggest that membrane-bound peptidases regulate EVT invasion in cooperation with a chemokine system during early human placentation.

A combinatorial role for NFAT5 in both myoblast migration and differentiation during skeletal muscle myogenesis

Skeletal muscle regeneration depends on myoblast migration, differentiation and myofiber formation. Isoforms of the nuclear factor of activated T cells (NFAT) family of transcription factors display nonredundant roles in skeletal muscle. NFAT5, a new isoform of NFAT, displays many differences from NFATc1-c4. Here, we examine the role of NFAT5 in myogenesis. NFAT5+/- mice displayed a defect in muscle regeneration with fewer myofibers formed at early times after injury. NFAT5 has a muscle-intrinsic function because inhibition of NFAT5 transcriptional activity caused both a migratory and differentiation defect in cultured myoblasts. We identified Cyr61 as a target of NFAT5 signaling in skeletal muscle cells. Addition of Cyr61 to cells expressing inhibitory forms of NFAT5 rescued the migratory phenotype. These results demonstrate a role for NFAT5 in skeletal muscle cell migration and differentiation. Furthermore, as cell-cell interactions are crucial for myoblast differentiation, these data suggest that myoblast migration and differentiation are coupled and that NFAT5 is a key regulator.

Integrin alpha5 is involved in fibronectin-induced human extravillous trophoblast invasion

To identify the molecules involved in human extravillous trophoblast (EVT) invasion, we raised murine mAbs that react with EVTs and obtained one mAb (CHL3) that inhibited invasion of a human choriocarcinoma-derived cell line, BeWo cells. The N-terminal 22 aminoacid sequence of the CHL3 antigen (150kDa) purified from placental tissue completely matched that of integrin alpha5, which is known to interact with fibronectin. Double immunohistochemical staining and flow cytometry confirmed the reactivity of CHL3 with integrin alpha5 and its expression on the surface of BeWo cells and human EVTs isolated from villous explant cultures. CHL3 mAb inhibited the attachment of human EVTs and BeWo cells to fibronectin-coated dishes, but not to Matrigel dishes. In the Matrigel invasion assay supplemented with or without fibronectin, the invasion of isolated EVTs and BeWo cells was attenuated by treatment with CHL3 without affecting cell proliferation. During invasion assays, the production of matrix metalloproteases 2 and 9 was not changed by CHL3. These findings suggest that interaction with fibronectin through integrin alpha5 plays an important role in human extravillous trophoblast invasion.

Intrauterine administration of autologous peripheral blood mononuclear cells promotes implantation rates in patients with repeated failure of IVF–embryo transfer

BACKGROUND

There are few effective approaches to infertile patients with repeated failure in IVF-embryo transfer therapy. Since recent evidence suggests that some populations of maternal immune cells positively support embryo implantation, we have developed a new approach using peripheral blood mononuclear cells (PBMCs).

METHODS

Patients who had not experienced successful pregnancy despite four or more IVF-embryo transfer sessions were enrolled in this study (n = 35, 35 cycles). PBMCs were obtained from patients on the day of oocyte retrieval and were cultured with HCG for 48 h. Two days later, PBMCs were freshly isolated from patients again, combined with cultured PBMC and then administered to the intrauterine cavity of the patients. Blastocyst transfer was performed on day 5, and the success of implantation in the PBMC-treated group was compared with that in the non-treated group.

RESULTS

Clinical pregnancy rate, implantation rate and live birth rate in the PBMC-treated group (41.2, 23.4 and 35.3%; n = 17, 47 and 16, respectively) were significantly higher than those in the non-treated group (11.1, 4.1 and 5.5%; n = 18, 49 and 18, respectively).

CONCLUSION

Intrauterine administration of autologous PBMC may be an effective approach to improve embryo implantation in patients with repeated IVF failures.

Cytotrophoblast induction of arterial apoptosis and lymphangiogenesis in an in vivo model of human placentation

We studied the vascular effects of invasive human cytotrophoblasts in vivo by transplanting placental villi to the fifth mammary fat pads or beneath the kidney capsules of Scid mice. Over 3 weeks, robust cytotrophoblast invasion was observed in both locations. The architecture of the mammary fat pad allowed for detailed analysis of the cells' interactions with resident murine blood vessels, which revealed specific induction of apoptosis in the endothelial cells and smooth muscle walls of the arterioles. This finding, and confirmation of the results in an in vitro coculture model, suggests that a parallel process is important for enabling cytotrophoblast endovascular invasion during human pregnancy. Cytotrophoblast invasion of the kidney parenchyma was accompanied by a robust lymphangiogenic response, while in vitro, the cells stimulated lymphatic endothelial cell migration via the actions of VEGF family members, FGF, and TNF-alpha. Immunolocalization analyses revealed that human pregnancy is associated with lymphangiogenesis in the decidua since lymphatic vessels were not a prominent feature of the nonpregnant endometrium. Thus, the placenta triggers the development of a decidual lymphatic circulation, which we theorize plays an important role in maintaining fluid balance during pregnancy, with possible implications for maternal-fetal immune cell trafficking.

Immune cells contribute to systemic cross-talk between the embryo and mother during early pregnancy in cooperation with the endocrine system

In early pregnancy, human chorionic gonadotropin (HCG) stimulates the corpus luteum to produce progesterone that in turn maintains human embryo implantation in the uterus. This inevitable communication through blood circulation can be called 'systemic cross-talk between the embryo and mother'. Despite considerable evidence suggesting that the human corpus luteum cannot be maintained by HCG alone, no other responsible soluble factors have been proposed. We found that peripheral blood mononuclear cells (PBMC) derived from pregnant women promoted progesterone production by human luteal cells and propose that both hormones and immune cells participate in this systemic cross-talk. This systemic cross-talk by immune cells is believed to operate in embryo implantation. Splenocytes derived from pregnant mice promoted endometrial differentiation and embryo implantation in vivo. Human PBMC derived from women early in pregnancy promoted invasion of murine embryos in vitro. In addition, recombinant HCG increased the effects of human PBMC on murine embryo invasion. Human chorionic gonadotropin also increased chemokine production by human PBMC through a lectin-glycan interaction, which is a primitive pathway in the immune system. Furthermore, chemokines were shown to induce human trophoblast invasion. These findings suggest that the immune system positively contributes to systemic cross-talk between the embryo and mother in cooperation with the endocrine system. (Reprod Med Biol 2006; 5: 19-29).

EPHB4 regulates chemokine-evoked trophoblast responses: a mechanism for incorporating the human placenta into the maternal circulation

In humans, fetal cytotrophoblasts leave the placenta and enter the uterine wall, where they preferentially remodel arterioles. The fundamental mechanisms that govern these processes are largely unknown. Previously, we have shown that invasive cytotrophoblasts express several chemokines, as well as the receptors with which they interact. Here, we report that these ligand-receptor interactions stimulate cytotrophoblast migration to approximately the same level as a growth factor cocktail that includes serum. Additionally, cytotrophoblast commitment to uterine invasion was accompanied by rapid downregulation of EPHB4, a transmembrane receptor associated with venous identity, and upregulation of ephrin B1. Within the uterine wall, the cells also upregulated expression of ephrin B2, an EPH transmembrane ligand that is associated with arterial identity. In vitro cytotrophoblasts avoided EPHB4-coated substrates; upon co-culture with 3T3 cells expressing this molecule, their migration was significantly inhibited. As to the mechanisms involved, cytotrophoblast interactions with EPHB4 downregulated chemokine-induced but not growth factor-stimulated migration. We propose that EPHB4/ephrin B1 interactions generate repulsive signals that direct cytotrophoblast invasion toward the uterus, where chemokines stimulate cytotrophoblast migration through the decidua. When cytotrophoblasts encounter EPHB4 expressed by venous endothelium, ephrin B-generated repulsive signals and a reduction in chemokine-mediated responses limit their interaction with veins. When they encounter ephrin B2 ligands expressed in uterine arterioles, migration is permitted. The net effect is preferential cytotrophoblast remodeling of arterioles, a hallmark of human placentation.

New regulatory mechanisms for human extravillous trophoblast invasion

Human extravillous trophoblasts (EVT) invade maternal deciduas and reconstructed maternal spiral arteries during early placentation. However, the precise regulatory mechanisms to induce EVT invasion toward arteries and/or to protect EVT from further invasion have not been well understood. Recently, it was found that EVT that had already ceased their invasion, specifically expressed cluster of differentiation (CD9) and dipeptidyl peptidase IV (DPPIV) on their cell surface. In addition, EVT migrating to maternal spiral arteries expressed CC chemokine receptor type-1 (CCR-1), which is a chemokine receptor for regulated on activation normal T cell expressed and secreted (RANTES) and so on. CD9 is associated with integrin molecules on the cell surface and is considered to modulate integrin function. In contrast, DPPIV is a cell surface peptidase that can metabolize RANTES at extracellular sites before its accessing to the chemokine receptors. In vitro functional assay showed that CD9, DPPIV and RANTES are involved in the regulation for EVT invasion. From these findings, it can be proposed that CD9 and DPPIV, including chemokines, are new regulatory factors for human extravillous trophoblasts. (Reprod Med Biol 2005; 4: 189-195).