Novel discovery of LYVE-1 expression in the hyaloid vascular system

• Published in: Investigative ophthalmology & visual science 2010-12, Vol.51 (12), p.6157-6161
• Main Authors: Zhang, Hui, Tse, Julie, Hu, Xuemei, Witte, Marlys, Bernas, Michael, Kang, Jinjoo, Tilahun, Firehiwott, Hong, Young-Kwon, Qiu, Mengsheng, Chen, Lu
• Format: Article
• Language: English
• Subjects: Angiopoietin-2 - metabolism; Animals; Antigens, Differentiation - metabolism; Female; Fluorescent Antibody Technique, Indirect; Glycoproteins - metabolism; Lens, Crystalline - blood supply; Lens, Crystalline - embryology; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Fluorescence; Ophthalmic Artery - embryology; Ophthalmic Artery - metabolism; Platelet Endothelial Cell Adhesion Molecule-1 - metabolism; Vitreous Body - blood supply; Vitreous Body - embryology
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.10-5205

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. 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. 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. 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.