title: Expression Patterns of VEGF and Flk-1 in Human Endometrium during the Menstrual Cycle.
abstract: BACKGROUND
  The VEGF is essential in the process of tissue remodeling and angiogenesis. Limited data is available on the expression and regulation of VEGF and its receptors in the human endometrium. The aim of this study was evaluation of expression patterns of VEGF and Flk-1 in human endometrium during the menstrual cycle.
  
  
  METHODS
  Sixty paraffin-embedded blocks of endometrial tissues from the patients with normal menstrual cycles were obtained. Tissue samples were assembled into tissue microarray slides and classified by histological dating into five phases: the proliferative (n = 14), peri-ovulatory (n = 9), early-secretory (n = 12), mid-secretory (n = 11) and late-secretory (n = 14) phases. Immunohistochemical staining was performed using VEGF or Flk-1 monoclonal antibodies. The intensity of immunostaining was evaluated by the semi-quantitative scoring method (HSCORE). Kruskal-Wallis one-way analysis of variance and Scheff's post-hoc test were used for statistical analysis. A p-value of <0.05 was considered statistically significant.
  
  
  RESULTS
  VEGF and Flk-1 were expressed in the three components of the endometrium at various phases of the menstrual cycle. In the stroma, the expression of VEGF varied among the phases (p < 0.05). The expression of Flk-1 in the luminal and glandular epithelium revealed stronger intensity of immunostaining as compared with the stroma at the different phases (p < 0.05). The level of Flk-1 expression also showed significant differences among the phases in the glandular epithelium with greatest expression at late-secretory phase (p < 0.05).
  
  
  CONCLUSIONS
  Temporal and spatial distribution of VEGF and Flk-1 expression in the three components of human endometrium during menstrual cycle suggests the functional role of angiogenesis in the remodeling process of endometrial tissue.
authors.affiliation: Department of Obstetrics and Gynecology, Cathay General Hospital, Taipei City, Taiwan ; Institute of Systems Biology and Bioinformatics, National Central University, Hongli City, Taoyuan County, Taiwan ; Fu Jen Catholic University School of Medicine, New Taipei City, Taiwan.
authors.forename: Tsung-Hsuan
authors.initials: TH
authors.lastname: Lai
authors.affiliation: Second Department of Obstetrics and Gynecology, University of Athens Medical School, Aretaieion Hospital, Athens, Greece.
authors.forename: Nikos
authors.initials: N
authors.lastname: Vlahos
authors.affiliation: Department of Gynecology and Obstetrics, School of Medicine, Johns Hopkins University, Baltimore, United States.
authors.forename: Ie-Ming
authors.initials: IeM
authors.lastname: Shih
authors.affiliation: Department of Gynecology and Obstetrics, School of Medicine, Johns Hopkins University, Baltimore, United States.
authors.forename: Yulian
authors.initials: Y
authors.lastname: Zhao
keywords: Endometrium; Flk-1; Menstrual cycle; Tissue microarray; VEGF