Endometrial Vasculature Research Articles

Abnormal expression of the angiopoietins and Tie receptors in menorrhagic endometrium

Objective To identify changes in expression of stimulatory and inhibitory factors when normal endometrium becomes menorrhagic. Design Retrospective blinded immunohistologic study. Setting Private research center. Patient(s) Premenopausal and postmenopausal women with non-menorrhagic and menorrhagic endometrium undergoing curettage or hysterectomy were selected. Intervention(s) Samples of endometrium were obtained from all patients. Main outcome measure(s) Expression of angiopoietins 1 and 2, and vascular receptors Tie-1 and Tie-2 and endothelial nitric oxide synthase (eNOS). Result(s) Angiopoietin 1 (ANG-1) expression was similar in non-menorrhagic and menorrhagic endometrium. However, there was a significant increase in expression of ANG-2 and its receptor Tie-2 in menorrhagic tissues, which may be important in destabilizing the endometrial vasculature. Tie-1, responsible for endothelial integrity, was also increased in menorrhagic tissues, and is a likely compensatory mechanism for the existing vascular pathology. Expression of eNOS was also increased in menorrhagic women. Conclusion(s) Differences in the expression of ANG-2, Tie-2, Tie-1, and eNOS were found in menorrhagic endometrium, which may represent a new target for therapeutic intervention to correct menorrhagic conditions.

Differential effects of thrombin and hypoxia on endometrial stromal and glandular epithelial cell vascular endothelial growth factor expression.

Ovarian steroids and/or premenstrual endometrial hypoxia are thought to restore the endometrial vasculature shed during menstruation by elevating endometrial vascular endothelial growth factor (VEGF) levels. During the luteal phase, VEGF levels peak, progesterone induces estradiol (E(2))-primed human endometrial stromal cells (HESCs) to decidualize and express tissue factor (TF), and endometrial vascular permeability is enhanced. The latter would present circulating clotting factors to decidual cell-expressed TF to form local thrombin. HESCs were incubated in serum-supplemented medium containing vehicle (control) or 10(-8) M E(2) or 10(-7) M medroxyprogesterone acetate (MPA) or E(2) + MPA for 7 d to induce decidualization, while monolayers of human endometrial glandular epithelial cells (HEGECs) formed during 4-d incubation of glands. The medium was exchanged for a defined medium containing corresponding vehicle or steroids +/- thrombin under normoxia or hypoxia (0-1% O(2)). Hypoxia enhanced secreted immunoreactive VEGF levels by severalfold in HESCs and HEGECs, but the steroids did not affect VEGF output in either cell type under normoxia or hypoxia. In E(2) + MPA-decidualized HESCs, VEGF levels were elevated by 0.1 U/ml of thrombin, and 0.5-2.5 U/ml of thrombin elicited maximum effects. The addition of 0.5 U/ml of thrombin evoked a time-dependent enhancement of VEGF levels and about an 8-fold increase at 48 h (P < 0.02; n = 6). Northern blotting indicated that E(2) + MPA-decidualized HESCs expressed VEGF(121), VEGF(165), and VEGF(189) mRNA, which were enhanced severalfold during 5- to 20-h incubation with thrombin. Moreover, TRAP, a synthetic peptide activator of the constitutively expressed protease activated receptor-1 thrombin receptor in decidualized HESCs, also elevated secreted VEGF levels. By contrast, HEGECs were unresponsive to thrombin added alone or with ovarian steroids. These results suggest that thrombin formed by progestin-augmented TF levels acts as an autocrine enhancer of VEGF expression in decidualized HESCs. Because angiogenesis occurs in a matrix of decidualized HESCs, these in vitro results provide a novel mechanism to account for both the peak in VEGF and angiogenesis in luteal phase human endometrium.

Surface vascularization and endometrial appearance in women with menorrhagia or using levonorgestrel contraceptive implants. Implications for the mechanisms of breakthrough bleeding.

Women using progestogen-only contraceptives are commonly troubled by irregular bleeding. Endometrial vessel breakdown and repair is thought to be locally regulated under the indirect influence of sex steroids. Most information about endometrial vessels is derived from blind biopsies taken in an outpatient setting. Hysteroscopy allows in-vivo observation of the whole endometrial surface, including vessel morphology, distribution and areas of bleeding, as well as information about non-vascular structures that may not be accessible from biopsies. Hysteroscopies were performed on 34 women using the levonorgestrel contraceptive implant system (Norplant(TM)) and in a comparison group of 20 women complaining of menorrhagia due to ovulatory dysfunctional bleeding. The images were captured and vascular appearances assessed using image analysis. The percentage of the superficial endometrium covered with blood vessels was found to be significantly greater in Norplant users compared with the comparison group (P = 0.0006). More superficial vessels were seen in those with recent frequent or prolonged bleeding and spotting (P < 0.0001). In Norplant users, but not in the comparison group, superficial vascular distribution was predominantly patchy (P < 0.0001). Unusual vascular appearances classified as 'neovascular' (P < 0.0001) and 'mosaic' (P < 0.0001) patterns were commonly seen in Norplant users but not in the comparison group. The hysteroscopic appearance of the endometrial epithelium, glands and stroma also differed between Norplant users and women with menorrhagia. Apparent shedding of the superficial endometrium was commonly seen by hysteroscopy in Norplant users during a bleeding episode (P < 0.0001). Prominent gland openings with thick mucus were commonly seen in Norplant users and small sessile polyps were seen in six cases. These hysteroscopic observations provide further evidence that exposure to progestogens alters the superficial endometrial vasculature and may interfere with angiogenesis.

Differential expression of neuropilin-1, a novel receptor for vascular endothelial growth factor, in cycling human endometrium

Objective: The endometrial vasculature undergoes dramatic changes in the female reproductive cycle, and angiogenesis is essential for endometrial proliferation and regeneration. Vascular endothelial growth factor (VEGF) is a potent modulator of angionesis and vascular remodelling in the endometrium. VEGF acts via two tyrosine kinase family receptors: VEGR1 (Flt-1) and VEGRF2 (KDR/Flk-1). Recently, neuropilin-1 (NRP-1), a membrane protein that is expressed in developing neurons and functions as a receptor or a component of the receptor complex for the class 3 semaphorins which regulate nerve fiber guidance in embryogenesis, was shown to be expressed also in endothelial cells binding VEGF165 and enhances the binding of VEGF165 to VEGFR2. These results suggest that VEGF, NRP-1 and VEGFR2 may play an important role in VEGF-induced vascular permeability and angiogenesis required for physiological reproductive cycle and further on for embryonic implantation. So far, nothing is known about the different expression of neuropilin-1 in the human endometrium during the menstrual cycle.

Progesterone receptor antagonists (antiprogestins)

Progesterone is an essential regulator of female reproductive functions mediated by the progesterone receptor. Therefore, its blockade by using an antagonist (antiprogestin) allows modulation of various reproductive processes. Since the first description of RU -486 numerous antiprogestins were synthesized with varying pharmacological characteristics. In this review the current knowledge is summarized on the basic in vitro and in vivo profile of antiprogestins with a special focus on a recently identified antiprogestin, ZK 230211. In addition, the use of antiprogestins in a new concept of fertility control in combination with an iNOS inhibitor is discussed. Since antiprogestins have a profound antiproliferative effect on primate endometrium the target for the antiprogestagenic action in the primate endometrium remains to be elucidated. However, the results obtained so far indicate that the endometrial vasculature may be the target for antiprogestins. The implications of these findings for endometrial disorders such as endometriosis are discussed. Numerous studies in animal models and results from first clinical trials demonstrated the efficacy of antiprogestins in treatment of breast cancer. The basic biological principles of the use of antiprogestins in oncological therapy are summarized and recent developments of the use of this important class of anti-hormones in cancer therapy are discussed.

Tubes, Branches, and Pillars

The angiogenic cascade is getting increasingly complex. A few years ago, vasculogenesis and angiogenesis were considered as the primary mechanisms leading to the formation of new blood vessels. The original definition of vasculogenesis denotes the formation of a primary embryonic vascular network from in situ differentiating angioblastic cells.1 In contrast, angiogenesis primarily referred to the sprouting of blood vessels from preexisting vessels.1 Recent advances in the identification of molecules that regulate angiogenesis and vascular remodeling have shown that the simplistic model of an invading capillary sprout is not sufficient to appreciate the whole spectrum of morphogenic events that are required to form a neovascular network (Figure 1).1–3 Undoubtedly, vascular endothelial growth factor (VEGF) acts at an early point in the hierarchical order of morphogenic events and probably fulfills all criteria to be considered as a master switch of the angiogenic cascade. In contrast, the angiopoietins and their receptor Tie-2 as well as the ephrins and their corresponding Eph receptors appear to act at a somewhat later stage of neovessel formation. These molecules orchestrate a number of related, yet functionally and molecularly not well understood, processes such as vessel assembly (network formation and formation of anastomoses), vessel maturation (recruitment of mural cells [pericytes and smooth muscle cells], and extracellular matrix assembly, pruning of the primary vascular bed), and acquisition of vessel identity (formation of arteries, capillaries, and veins)3,4 (Figure 2). Lastly, the mechanisms of organotypic differentiation of the vascular tree (continuous endothelium, discontinuous endothelium, fenestrated endothelium) are not at all understood and the first molecules that govern subpopulation-specific vascular growth and differentiation are just being uncovered.5,6 Figure 1. Change of paradigm. From sprouting angiogenesis to vascular morphogenesis. Basement membrane degradation, directed endothelial cell migration, and proliferation (left) were considered as the primary mechanisms of angiogenesis. …

Importance of angiogenesis in reproductive physiology

The cyclic angiogenesis that occurs uniquely within the female reproductive tract is critical for normal reproduction. Two families of endothelial cell-specific growth factors and their receptors have been identified in the ovary, uterus, and placenta: vascular endothelial growth factor/vascular permeability factor and the angiopoietins. These appear to have complementary actions on the vasculature and to be involved during intrauterine development as well as in the adult. Within the ovary, a complex cascade of events required for angiogenesis may play a role in follicular maturation and selection as well as in normal corpus luteum function. Aberrant expression of angiogenic factors plays a role in a wide variety of abnormalities in the ovary. In the uterus, angiogenesis is required for endometrial growth and remodeling. Peptide growth factors such as vascular endothelial growth factor may serve as local mediators of the effects of reproductive hormones on the endometrial vasculature. Disease states such as dysfunctional uterine bleeding, endometriosis, and endometrial hyperplasia or cancer may be associated with aberrant uterine angiogenesis.

Changes in vascular basement membrane in the endometrium of Norplant users

Progestogen-only contraception is almost invariably associated with changes in menstrual bleeding patterns. Changes in the endometrial vasculature, and in particular an increase in vascular fragility, may contribute to this bleeding. In this study, endometrial vascular density and endothelial cell basement membrane components were examined using immunohistochemistry before and after insertion of Norplant. Endometrial vascular density was increased from a mean (+/- SEM) of 189.6 +/- 7.0 vessels/mm2 during the control cycle to 253.9 +/- 80.7 vessels/mm2 at 2-13 weeks of Norplant exposure, and to 212.7 +/- 12.9 vessels/mm2 at 14-42 weeks. During the control cycle, a mean of 161.4 +/- 4.5 vessels/mm2 stained for collagen IV (85% of all vessels), while at 2-13 weeks, 144.5 +/- 13.0 vessels/mm2 stained for collagen IV (57% of all vessels) (t ratio = 2.08, P = 0.0057). By 14-42 weeks, 71% of vessels (151.0 +/- 9.8) vessels/mm2 were surrounded by collagen IV. This was not significantly different from control values (t ratio = 2.03). Endometrial vascular laminin was also reduced following Norplant insertion, from a mean of 176.0 +/- 4.2 vessels/mm2 in the control cycle (93% of vessels), to 156.3 +/- 6.7 vessels/mm2 at 2-13 weeks of exposure (57% of vessels) (t ratio = 2.08, P = 0.01). By 14-42 weeks of exposure to Norplant, 162.5 +/- 9 vessels/mm2 (76%) stained for laminin. This was not significantly different from control values (t ratio = 2.04). Endometrial vascular heparan sulphate proteoglycan (HSPG) was reduced from 58.6 +/- 3.0 vessels/mm2 during the control cycle (31% of vessels) to 43.6 +/- 5.6 vessels/mm2 (only 17% of vessels) at 2-13 weeks (t ratio = 2.08, P = 0.025). At 14-42 weeks, only 19% of vessels stained for HSPG (41.3 +/- 5.8 vessels/mm2; t ratio = 2.04, P = 0.009).

A longitudinal study of changes in endometrial microvascular density in norplant® implant users

This study aimed to investigate the effects of the subdermal levonorgestrel contraceptive implant Norplant® on endometrial vascular density at different durations of exposure, and the relationship between endometrial histology, vascular density, and bleeding patterns. A prospective controlled trial of Norplant implant users compared endometrial vascular density in biopsies taken before and after Norplant implant insertion. A total of 34 women with regular menstrual cycles requesting long-term contraception were recruited at the Sydney Centre for Reproductive Health Research, Australia. A significant increase in mean endometrial microvascular density was observed from as early as 3 weeks after insertion of Norplant implants. Vascular density was increased from a control secretory phase value of 189.6 ( 7.0 vessels/mm 2 (±SEM) to 253.80 ± 7 vessels/mm 2 at 2–13 weeks of Norplant implant exposure (t ratio = 2.08, p = 0.01) and 212.7 ± 12.9 vessels/mm 2 at 14–42 weeks of exposure (t ratio = 2.03, p = 0.02). In those with atrophic endometrium, or in whom myometrium and basalis only were found in biopsies (20 of 66, 30%), mean endometrial vascular density was increased at 273.1 ± 16.1 vessels/mm 2 compared with 210.9 ± 11.7 vessels/mm 2 in other histological groups (F ratio = 9.74, p = 0.0028). Bleeding and spotting in the previous 30 days were less common in those with this histological appearance at a mean of 4.95 days compared with 8.22 days. This is the first study to assess endometrial vascular density in the early months of Norplant implant use. The findings suggest that the endometrial vasculature is profoundly altered in the early months of Norplant implant exposure when bleeding problems are most common.

Human endothelial cell migration is stimulated by urokinase plasminogen activator:plasminogen activator inhibitor 1 complex released from endometrial stromal cells stimulated with transforming growth factor beta1; possible mechanism for paracrine stimulation of endometrial angiogenesis.

Human endometrial stromal cell cultures, stimulated for two days with recombinant transforming growth factor beta1 (TGFbeta1; 10 ng/ml), contained conditioned medium concentrations of urokinase plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI1), and uPA:PAI1 complex. Since a number of cellular effects have been reported to follow a binding of enzymatically inactive uPA to the receptor in different cell types, we studied the influence of uPA:PAI1 complex on human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1). Increasing concentrations of uPA:PAI1 complex as well as free uPA resulted in a dose-dependent stimulation of endothelial cell migration. Stimulation by the complex was of the same magnitude as that of free uPA on a molar basis and reached its maximum at 1 nM in both cell types. PAI1 by itself, however, had no effect on cell migration. The migratory response to both uPA and the uPA:PAI1 complex was inhibited by antibody adhesion to the cell surface receptor for uPA. In addition, we found that TGFss1 had a direct stimulatory effect on migration in both HUVEC and HMEC-1. This response did not, however, involve the binding of uPA to the uPA receptor. Since TGFbetas are expressed in endometrial tissue and reportedly stimulate angiogenesis in other tissues in vivo, though not endothelial cell proliferation in vitro, they may engage in the regeneration of endometrial vasculature indirectly via perivascular cells. We found that the uPA:PAI1 complex, when released from endometrial stromal cells in response to TGFbeta1, stimulated endothelial cell migration. This suggests a possible mechanism for paracrine stimulation of endometrial angiogenesis.

Angiogenesis in the endometrium.

Human endometrial vasculature has the unique property of undergoing benign angiogenesis during each menstrual cycle under the influence of the ovarian steroids estradiol and progesterone. However, neither has intrinsic angiogenic activity and endometrial angiogenesis involves stimulation by ovarian steroids of angiogenic factor release by the epithelium and stroma which then act on the endothelium. In vitro models using cultures of isolated endometrial epithelium, stroma and endothelium now allow mechanistic questions to be addressed. Vascular endothelial growth factor and platelet-derived endothelial cell growth factor/thymidine phosphorylase at present appear to be key players in endometrial angiogenesis.

Decidual cell regulation of hemostasis during implantation and menstruation.

Progesterone stimulation of the estradiol (E2)-primed human endometrium initiates DZ of the stromal cells around the spiral arterioles. Under continued steroid stimulation, DZ spreads wave-like to establish the decidual cell as a major cell type of the luteal phase and pregnant endometrium. Because of their widespread distribution throughout the endometrium and concentration at perivascular sites, decidual cells are spatially and temporally positioned to mediate the opposing requirements of maintaining hemostasis during endovascular trophoblast invasion, yet promoting menstrual hemorrhage in the absence of implantation. The experimental results summarized in this review indicate that the paradoxical properties manifested by endometrial stromal/decidual cells are controlled by several proteins with either hemostatic or ECM-degrading or vasoactive activity, and that their expression is altered in response to changes in levels of circulating ovarian steroids during the menstrual cycle. These conclusions are drawn primarily from studies with a well-characterized in vitro model of DZ using monolayers of stromal cells derived from specimens of predecidualized endometrium. Thus, progestins modify the expression of several DZ-related markers in the cultured stromal cells, and E2 enhances these effects despite the lack of response to E2 alone. These responses are consistent with the differential actions displayed by E2 and progesterone in vivo, by which E2 primes the endometrium for the decidualizing effects of progesterone by elevating progesterone receptor levels. Accordingly, during steroid-induced in vitro DZ, a marked increase in the expression of stromal cell TF and PAI-1 and reciprocal inhibition of tPA activity suggest mechanisms to account for the absence of hemorrhage during invasion of the endometrial vasculature by implanting trophoblasts. In contrast to steroid-induced DZ, the events of menstruation are initiated in response to a decline in circulating levels of ovarian steroids. Accordingly, subjecting in vitro decidualized stromal cells to steroid withdrawal results in pronounced reversal in the expression of all of the end points listed above. Consequently, the local hemostatic environment is transformed into a hemorrhage-promoting milieu. Taken together with vascular injury resulting from ischemia induced by spiral artery vasoconstriction, the net effect is attainment of two prerequisites for menstrual hemorrhage, vascular injury and inadequate hemostasis.

Expression of vascular endothelial growth factor (VEGF) and VEGF-receptor messenger ribonucleic acids in the peri-implantation rabbit uterus.

The endometrial vasculature undergoes expansion during preimplantation stages and, even more prominently, after implantation. In addition to angiogenesis, vascular hyperpermeability accompanies the attachment and invasion of blastocysts into the uterine lining. Vascular endothelial growth factor (VEGF) is an angiogenic factor expressed in mammalian uteri that also has potent activity in inducing vascular permeability. Rabbit uteri were examined using Northern and in situ hybridization to assess the temporal and spatial expression of VEGF and its receptor (Flk-1, Flt-1) mRNAs during the pre- and peri-implantation periods (Days 0-8). Steady-state levels of VEGF mRNA were highest in endometrium at estrous and peri-implantation stages (Days 6-8). In situ hybridization revealed a shift from uniform expression of VEGF transcripts throughout the uterus at estrus and Day 4, to an endometrial epithelial localization just before and during implantation. At implantation sites, a pronounced signal was present in the trophoblastic knobs, the syncytial aggregates that attach to and invade the endometrium. VEGF protein was detected by immunoblot analysis in peri-implantation-stage uteri but was below the limit of detection in estrous endometrium. VEGF receptor mRNAs were expressed in the uterus at all stages examined, with high levels of Flk-1 and Flt-1 at estrus and again just before implantation, 6-3/4 days pregnant. The high level just before implantation correlates with in situ hybridization results showing a prominent, but transient, signal for Flk-1 mRNA in the endometrial epithelium. During implantation, Flk-1 mRNA was associated with blood vessels of the endometrial stroma. We conclude that VEGF is a candidate factor for the induction of vascular hyperpermeability at implantation in the rabbit and in the angiogenic process that follows.

Endometrial vasculature in Norplant users.

Disrupted, prolonged and irregular endometrial bleeding are major unwanted side-effects of progestin-only contraceptives. The aim of this paper is to review current information on steroid control of the microvasculature, microvascular heterogeneity and microvascular fragility, with emphasis on the relevance of these issues to the endometrial microvasculature in women receiving Norplant implant contraception. Subjects were either Indonesian women with between 3 and 12 months exposure to Norplant (n = 191) or Caucasian controls recruited in Melbourne, Australia. Norplant endometrium was always thinner than control endometrium, with a varied histology that usually included a basalis-type appearance, signs of haemorrhage and some dilated and congested subepithelial vessels. Thin-walled vessels were seen which could have been either blood vascular or lymphatics. Steroid control of the vasculature can operate through numerous direct and indirect mechanisms, with up to 30 genes relevant to vascular function having consensus oestrogen response elements in their promoter regions. The vasoactive effects of progesterone are less well documented. However, experimental data for direct effects on the endometrial vasculature are mounting. Progestin-induced endometrial breakthrough bleeding is often focal, suggesting that microvascular heterogeneity may be an important factor in understanding this phenomenon. Increased susceptibility to bleeding may result from increased microvascular fragility, possibly as a consequence of progestins altering the balance of angiogenic promoters and inhibitors in the endometrium, thus leaving the vessels in a permanently weakened state.

Effect of single-dose, early luteal phase administration of mifepristone (RU486) on implantation stage endometrium in the rhesus monkey.

The characteristics of implantation stage endometrium following a single-dose, early luteal phase application of mifepristone (RU486) in proven conception cycles has been examined in the rhesus monkey in an attempt to understand the physiological basis of the anti-implantation activity of the drug. Endometrial samples were collected from monkeys subjected to vehicle (group 1, n = 14) and RU486 (2 mg/kg body weight; group 2, n = 12) on day 2 after the presumed day of ovulation of successfully mated cycles. The average diameter of glands (P < 0.05), number of vacuolated cells (P < 0.01), number of supranuclear vacuolated cells (P < 0.05) in glandular epithelium and amount of glandular secretion (P < 0.05) were significantly lower in RU486-treated endometrium compared with control tissue samples. Additionally, 18% of glandular epithelial cells showed apoptotic and degenerative features in RU486-treated tissue samples. These data, together with the observed significant decreases in precipitate area (P < 0.02) and in the optical absorbance of alkaline phosphatase reaction end-product (P < 0.05), confirm that retardation in glandular differentiation in the upper functionalis is a likely target of antiprogestin action in implantation stage endometrium. An increased frequency of mitosis in stromal cells (P < 0.05) and a greater degree of extravasation (P < 0.05) were also observed after RU486 exposure. Despite an apparent indication of constriction and regression in few RU486-exposed endometria compared with controls, morphometric analyses did not show any changes in capillary structure. Whether endometrial vasculature in progesterone-exposed uterus is a target of antiprogestin action during the peri-implantation stage remains to be determined. Further studies are required to explain the observed increase (P < 0.02) in the area of precipitate of von Willebrand (vW) factor with no change in vW factor-positive vessels, and the apparent increase in collagen IV immunostain in subepithelial and perivascular basement membrane in implantation stage endometrium after early luteal phase RU486 treatment in monkeys.

A Biological Model for the Regulation of Peri-Implantational Hemostasis and Menstruation

To delineate the physiologic mechanisms whereby the human endometrium maintains hemostasis during endovascular trophoblast invasion but permits menstrual hemorrhage. Experimental results are presented that are relevant to developing a comprehensive biological model for studying peri-implantational hemostasis and menstruation. A marked increase in the expression of tissue factor (TF) and type-1 plasminogen activator inhibitor (PAI-1) and an inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA, respectively), matrix metalloproteinases (MMP), and endothelin-1 (ET-1) expression accompany progestin-induced decidualization of estrogen-primed endometrial stromal cells both in vivo and in vitro. The presence of these important regulators of hemostasis, fibrinolysis, extracellular matrix (ECM) turnover, and vascular tone in decidualized human stromal cells and decidual cells isolated from gestational endometrium suggests a mechanism to explain the absence of hemorrhage during invasion of the endometrial vasculature by trophoblasts. Conversely, progesterone withdrawal reduces TF and PAI-1 expression and increases tPA, uPA, MMP, and ET-1 expression accounting for the hemorrhage, enhanced fibrinolysis, ECM degradation, and ischemic spiral arterial vascular injury characterizing menstruation. Perivascular decidualized endometrial stromal cells are spatially and temporally positioned to promote endometrial hemostasis during implantation but, paradoxically, promote the hemorrhage of menstruation via their hormone-regulated expression of hemostatic, proteolytic, and vasoactive proteins.

New Cells and Old Vessels: The Remodeling of the Endometrial Vasculature during Establishment of Endometrial Cups1

New Cells and Old Vessels: The Remodeling of the Endometrial Vasculature during Establishment of Endometrial Cups1

Expression of adhesion molecules in human endometrial vasculature throughout the menstrual cycle.

In the present study, we examined the pattern of expression of human leukocyte antigen (HLA)-DR as well as several adhesion molecules implicated in leukocyte trafficking, including ICAM-1, E-selectin, and VCAM-1 in human endometrium. All of the vessels in endometrium exhibited HLA-DR and ICAM-1 throughout the menstrual cycle. In the proliferative phase, endothelial cells in the functionalis were weak to nonreactive for VCAM-1 and were E-selectin negative (E-selectin-). Endothelial cells of the vessels in the basalis and within myometrium were VCAM positive (VCAM-1+)/E-selectin-. In sharp contrast, in the secretory phase, endothelial cells in the basalis were VCAM-1+/E-selectin+. Surprisingly, endometrial glands, primarily those in the basalis, expressed E-selectin and VCAM-1 during the entire menstrual cycle. Stromal cells were ICAM-1+ and were focally HLA-DR+ around HLA-DR+ lymphoid cells during the entire menstrual cycle and were E-selectin-/VCAM-1- during the proliferative phase. Immunoreactivity for VCAM-1 and E-selectin, however, appeared in the stromal cells in the upper functionalis in the secretory phase. Immunoreactivity for VCAM-1 was the distinguishing feature that separated the lymphoid cells in the aggregates from other nonaggregated lymphoid cells. Recruitment of leukocytes to tissues is in part due to cytokine-regulated expression of specific molecules on endothelial cells. Therefore, we tested the effects of cytokines on the expression of these molecules in endothelial cells derived from microvasculature. ICAM-1 and VCAM-1 were inducible in a dose-dependent fashion in the endothelial cells by interleukin-1 alpha (IL-1 alpha), interferon-gamma (IFN gamma), and tumor necrosis factor-alpha (TNF alpha). Expression of HLA-DR in endothelial cells was inducible by IL-1 alpha and IFN gamma and not by TNF alpha. Expression of E-selectin on endothelial cells was induced only by IL-1 alpha, not by IFN gamma or TNF alpha. Cytokine treatment of endothelial cells significantly enhanced the binding of leukocytes to endothelial cells. The data show a heterogeneity in the vasculature of endometrium with respect to the expression of various adhesion molecules. This heterogeneity is potentially related to the type or amount of cytokine with which endothelial cells are activated. In addition, unique cell- and site-specific expression of adhesion molecules in human endometrium throughout the menstrual cycle may account for the distinct distribution pattern of leukocytes in this tissue.

Expression of adhesion molecules in human endometrial vasculature throughout the menstrual cycle

Expression of adhesion molecules in human endometrial vasculature throughout the menstrual cycle

Involvement of the proto-oncogene c-ets 1 and the urokinase plasminogen activator during mouse implantation and placentation.

Many of the Ets proteins have been shown to be transcription activators. In vitro, Ets 1 proteins are involved in the transcriptional induction of genes such as stromelysin 1, collagenase 1 or urokinase type plasminogen activator, which are proteases responsible for extracellular matrix degradation. In vivo, c-ets 1 is expressed in a wide variety of embryonic tissues in migrating cells, especially in endothelial cells during blood vessel formation. C-ets 1 is also expressed in stromal cells of invasive carcinomas. In the present work, we have investigated the expression of both c-ets 1 and u-PA, a putative target gene of the Ets 1 proteins, within a biological model which includes both embryonic and tumoral aspects. Implantation and placentation of the mouse embryo display migration of the trophoblastic cells, which invade the stroma of the uterine endometrium and trigger the establishment of a new vascular frame. Using in situ hybridization, we show that the overlapping of expression of c-ets 1 and u-PA is restricted to some maternal cell populations from the invasive front and to the endothelial cells of the endometrial vasculature. C-ets 1 is never expressed in trophoblasts. In contrast, u-PA expression in trophoblasts is strong and coincides with the embryo invasive phase. In the embryo proper, c-ets 1 displays a spatio-temporal expression pattern similar to that described in the chick embryo. Until E 10.5, u-PA is expressed neither in embryonic nor in extra-embryonic structures. The respective roles of c-ets 1 and u-PA and their relationship during mammalian placentation are discussed.