title: Absence of blood and lymphatic vessels in the developing human cornea.
abstract: OBJECTIVE
  The normal human cornea is devoid of both blood and lymphatic vessels and actively maintains this avascularity (corneal angiogenic privilege). Whether and when corneal angiogenic privilege is achieved during development is unknown.
  
  
  METHODS
  This study analyzed whether the cornea is primarily devoid of both blood and lymphatic vessels during intrauterine development or whether secondary regression of pre-existing vessels occurs before delivery. Indirect double immunohistochemistry was performed on 4-microm serial pupil-optic disc sections of paraffin-embedded human eyes stillborn at gestational ages of 17 to 41 weeks with antibodies against von Willebrand factor (vWF; factor VIII-associated antigen) as a panendothelial marker and with antibodies against lymphatic vessel endothelial hyaluronate receptor 1 (LYVE1) as a marker specific for lymphatic vascular endothelium.
  
  
  RESULTS
  Human corneas were devoid of both vWF+++/LYVE-1(-) blood vessels and vWF+/LYVE-1+++ lymphatic vessels at all time-points analyzed. In contrast, there were numerous blood and lymphatic vessels detectable in the adjacent conjunctiva.
  
  
  CONCLUSIONS
  The normal human cornea is primarily avascular and devoid of both blood and lymphatic vessels. Corneal angiogenic privilege is already achieved very early during fetal intrauterine development. This suggests early and strong expression of both antiangiogenic and antilymphangiogenic factors in the human cornea during development.
authors.affiliation: Department of Ophthalmology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany. ccursiefen@yahoo.com
authors.forename: Claus
authors.initials: C
authors.lastname: Cursiefen
authors.forename: Carmen
authors.initials: C
authors.lastname: Rummelt
authors.forename: Anselm
authors.initials: A
authors.lastname: Jünemann
authors.forename: Christian
authors.initials: C
authors.lastname: Vorwerk
authors.forename: Winfried
authors.initials: W
authors.lastname: Neuhuber
authors.forename: Friedrich E
authors.initials: FE
authors.lastname: Kruse
authors.forename: Falk
authors.initials: F
authors.lastname: Schroedl
mesh_terms: D001808:Blood Vessels / Q000196:embryology* / Q000378:metabolism; D003315:Cornea / Q000196:embryology*; D005865:Gestational Age; D006801:Humans; D007124:Immunoenzyme Techniques; D042583:Lymphangiogenesis / Q000502:physiology*; D042601:Lymphatic Vessels / Q000196:embryology* / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000502:physiology*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: C119248:LYVE1 protein, human; D033921:Vesicular Transport Proteins; D014841:von Willebrand Factor