title: Endometrial angiogenesis throughout the human menstrual cycle.
abstract: BACKGROUND
  The timing and mechanisms of new blood vessel formation in the endometrium during the menstrual cycle are still largely unknown. In the present study we used the chick embryo chorioallantoic membrane (CAM) as an in-vivo assay for angiogenesis to assess the angiogenic potential of endometrium obtained at different stages of the menstrual cycle.
  
  
  METHODS
  Endometrial fragments were explanted onto the CAM and, after 4 days of incubation, slides of the treated area were taken in ovo through a microscope for computerized image analysis. The vascular density index (VDI), a stereological estimate of vessel number and length, was obtained by counting the intersections of vessels with five concentric circles of a circular grid superimposed on the computerized image.
  
  
  RESULTS
  We demonstrated that human endometrium has angiogenic potential throughout the menstrual cycle. Furthermore, there was a significant difference in angiogenic response between the stages of the menstrual cycle (P = 0.01). The VDIs of the early proliferative, early and late secretory stage were significantly higher than the VDI of the late proliferative phase.
  
  
  CONCLUSIONS
  Elongation of existing vessels during the early proliferative phase as well as growth and coiling of the spiral vessels during the secretory phase may demand far higher angiogenic activity than outgrowth and maintenance of vessels during the late proliferative phase.
authors.affiliation: Department of Obstetrics and Gynaecology, Maastricht University, Maastricht, The Netherlands. jwmmaas@hotmail.com
authors.forename: J W
authors.initials: JW
authors.lastname: Maas
authors.forename: P G
authors.initials: PG
authors.lastname: Groothuis
authors.forename: G A
authors.initials: GA
authors.lastname: Dunselman
authors.forename: A F
authors.initials: AF
authors.lastname: de Goeij
authors.forename: H A
authors.initials: HA
authors.lastname: Struyker Boudier
authors.forename: J L
authors.initials: JL
authors.lastname: Evers
mesh_terms: D000482:Allantois / Q000098:blood supply; D000818:Animals; D001808:Blood Vessels / Q000033:anatomy & histology; D002642:Chick Embryo; D002823:Chorion / Q000098:blood supply; D046508:Culture Techniques; D004717:Endometrium / Q000098:blood supply*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008597:Menstrual Cycle; D018919:Neovascularization, Physiologic