title: Novel discovery of LYVE-1 expression in the hyaloid vascular system.
abstract: OBJECTIVE
  The hyaloid vascular system (HVS) is a transient network nourishing developing eyes and has been widely used as a natural model to study blood vessel regression. Failure of its regression in humans leads to several blinding diseases. Lymphatic vessel endothelial hyaluronic acid receptor (LYVE-1) is a recently defined lymphatic marker that is also expressed by a subpopulation of macrophages. To date, there is no report on its expression in the HVS. This study was conducted to investigate whether LYVE-1 is expressed in the HVS and how it is associated with the vascular structure and macrophage phenotype.
  
  
  METHODS
  Normal C57BL/6 mouse eyeballs were sampled from embryonic day (E) 10.5 to postnatal (P) and adult stages for immunofluorescent microscopic studies with antibodies against LYVE-1, CD31 (panendothelial cell marker), and F4/80 (macrophage marker). Additionally, Angiopoietin-2 (Ang-2) knockout mice with abnormally persistent HVS were examined.
  
  
  RESULTS
  The LYVE-1 expression was detected on normal HVS between E12.5 and P14. The LYVE-1(+) cells were F4/80(+) but CD31(-), indicating a macrophage lineage. Additionally, LYVE-1(+) cells bud on CD31(+) vessels and constitute an integral part of the network in both normal developing and Ang-2 knockout mice.
  
  
  CONCLUSIONS
  This study provides the first evidence that the HVS contains a LYVE-1(+) cellular component in both physiological and pathologic conditions. This novel finding not only provides a new concept in defining the embryogenesis and pathogenesis of the HVS, it also leads to a completely natural model in which to study the functions of the LYVE-1 pathway, an important topic for lymphatic research as well.
authors.affiliation: Center for Eye Disease and Development, School of Optometry, University of California, Berkeley, CA 94720, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Julie
authors.initials: J
authors.lastname: Tse
authors.forename: Xuemei
authors.initials: X
authors.lastname: Hu
authors.forename: Marlys
authors.initials: M
authors.lastname: Witte
authors.forename: Michael
authors.initials: M
authors.lastname: Bernas
authors.forename: Jinjoo
authors.initials: J
authors.lastname: Kang
authors.forename: Firehiwott
authors.initials: F
authors.lastname: Tilahun
authors.forename: Young-Kwon
authors.initials: YK
authors.lastname: Hong
authors.forename: Mengsheng
authors.initials: M
authors.lastname: Qiu
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
mesh_terms: D042702:Angiopoietin-2 / Q000378:metabolism; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006023:Glycoproteins / Q000378:metabolism*; D007908:Lens, Crystalline / Q000098:blood supply / Q000196:embryology*; D008297:Male; D026901:Membrane Transport Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009880:Ophthalmic Artery / Q000196:embryology* / Q000378:metabolism*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D014822:Vitreous Body / Q000098:blood supply / Q000196:embryology*
chemical_list: D042702:Angiopoietin-2; D000943:Antigens, Differentiation; D006023:Glycoproteins; D026901:Membrane Transport Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C492273:LYVE1 protein, mouse; C036763:monocyte-macrophage differentiation antigen