title: Extravillous trophoblast invasion of venous as well as lymphatic vessels is altered in idiopathic, recurrent, spontaneous abortions.
abstract: Do extravillous trophoblasts (EVTs) invade non-arterial decidual vessels in healthy and pathological pregnancies?
  
  
  
  Our results reveal that trophoblast invasion of venous and lymphatic vessels is a frequent event during the first trimester of pregnancy and is compromised in  recurrent spontaneous abortion (RSA). In addition, the present data suggest that EVTs populate regional lymph nodes during pregnancy.
  
  
  
  Human trophoblasts remodel and invade decidual spiral arteries. In addition, a recent report demonstrates that trophoblasts contact and invade decidual veins.
  
  
  
  Tissue samples of human first trimester deciduae basalis (n = 54, 6th-13th weeks of gestation) obtained from elective pregnancy terminations were used to study trophoblast invasion into veins and lymphatics, in comparison to arteries. Age-matched cases of idiopathic, recurrent spontaneous abortions tissue samples (n = 23) were assessed for cell numbers of EVTs in these decidual vessels. In addition, lymph nodes of four pregnant women were analysed for the presence of EVTs.
  
  
  
  Localization, frequency and EVT-mediated targeting and invasion of arterial, venous as well as lymphatic vessels were determined in first trimester decidua basalis tissue sections using immunofluorescence staining with antibodies against CD31, CD34, ephrin B2 (EFNB2), ephrin receptor B4 (EPHB4), HLA-G, podoplanin, prospero-related homeobox 1 (Prox-1), alpha-smooth muscle actin 2 (ATCTA2), von willebrand factor (vWF) and proteoglycan 2 (PRG2). Arterial, venous and lymphatic-associated EVTs were further characterized according to their position in the vascular structure and classified as intramural (im) or intraluminal (il).
  
  
  
  EVTs, specifically expressing PRG2, target and invade veins and lymphatics in first trimester decidua basalis since HLA-G+ trophoblast were detected in the vascular wall (intramural EVT, imEVTs) and in the lumen of these vessels (intraluminal EVT, ilEVTs). In total, 276 arteries, 793 veins and 113 lymphatics were analysed. While EVTs contact and invade arteries and veins to a similar extent we found that lymphatics are significantly less affected by EVTs (P = 0.001). Moreover, ilEVTs were detected in the lumen of venous and lymphatic vessels, whereas ilEVTs were only found occasionally in the lumen of arteries. Interestingly, RSA tissue sections contained significantly more arterial (P = 0.037), venous (P = 0.002) and lymphatic vessels (P < 0.001), compared to healthy controls. However, while RSA-associated arterial remodeling was unchanged (P = 0.39) the ratios of EVT-affected versus total number of veins (P = 0.039) and lymphatics (P < 0.001) were significantly lower in RSA compared to age-matched healthy decidual sections. Finally, HLA-G+/PRG2+/CD45-EVTs can be detected in regional lymph nodes of pregnant women diagnosed with cervical cancer.
  
  
  
  N/A.
  
  
  
  In this study, first trimester decidual tissues from elective terminations of pregnancies have been examined and used as a reference for healthy pregnancy. However, this collective may also include pregnancies which would have developed placental disorders later in gestation. Due to limitations in tissue availability our staining results for EVT-specific marker expression in regional lymph nodes of pregnant women are based on four cases only.
  
  
  
  In this study, we propose migration of HLA-G+ cells into regional lymph nodes during pregnancy suggesting that the human EVT is capable of infiltrating maternal tissues via the blood stream. Moreover, the description of compromised EVT invasion into the venous and lymphatic vasculature in RSA may help to better understand the pathological characteristics of idiopathic recurrent pregnancy loss.
  
  
  
  This study was supported by the Austrian Science Fund (grant P-25187-B13 to J.P. and grant P-28417-B30 to M.K.). There are no competing interests to declare.
authors.affiliation: Department of Obstetrics and Gynecology, Reproductive Biology Unit, Medical University of Vienna, Währinger Gürtel 18-20, 5Q, 1090 Vienna, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Windsperger
authors.affiliation: Clinical Institute of Pathology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
authors.forename: Sabine
authors.initials: S
authors.lastname: Dekan
authors.affiliation: Department of Gynecological Endocrinology and Reproductive Medicine, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
authors.forename: Sophie
authors.initials: S
authors.lastname: Pils
authors.affiliation: Institute of Pathology, University Hospital Bonn, Sigmund-Freud-Straße 25, Building 62, 53127 Bonn, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Golletz
authors.affiliation: Department of Obstetrics and Gynecology, Reproductive Biology Unit, Medical University of Vienna, Währinger Gürtel 18-20, 5Q, 1090 Vienna, Austria.
authors.forename: Victoria
authors.initials: V
authors.lastname: Kunihs
authors.affiliation: Gynmed Clinic, Mariahilfergürtel 37, 1150 Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Fiala
authors.affiliation: Institute of Pathology, University Hospital Bonn, Sigmund-Freud-Straße 25, Building 62, 53127 Bonn, Germany.
authors.forename: Glen
authors.initials: G
authors.lastname: Kristiansen
authors.affiliation: Department of Obstetrics and Gynecology, Reproductive Biology Unit, Medical University of Vienna, Währinger Gürtel 18-20, 5Q, 1090 Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Knöfler
authors.affiliation: Department of Obstetrics and Gynecology, Reproductive Biology Unit, Medical University of Vienna, Währinger Gürtel 18-20, 5Q, 1090 Vienna, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Pollheimer
mesh_terms: D000026:Abortion, Habitual / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D000028:Abortion, Induced; D000022:Abortion, Spontaneous / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D000328:Adult; D001158:Arteries / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D002465:Cell Movement; D003656:Decidua / Q000098:blood supply / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D047093:Eosinophil Major Basic Protein / Q000378:metabolism; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D042601:Lymphatic Vessels / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D010929:Placentation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011509:Proteoglycans / Q000378:metabolism; D012189:Retrospective Studies; D014327:Trophoblasts / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D066253:Vascular Remodeling; D014680:Veins / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000473:pathology*
chemical_list: D015415:Biomarkers; D011509:Proteoglycans; C074129:PRG2 protein, human; D047093:Eosinophil Major Basic Protein
keywords: decidual vasculature; extravillous trophoblast; recurrent spontaneous abortion; trophoblast; vascular remodeling