PURPOSE: Previous studies have identified sequences encoding vascular endothelial growth factor (VEGF)-A and one of the VEGF receptors (VEGFR2, Flk-1, KDR) in lens fiber cells. The current study was undertaken to determine the distribution of VEGF-A protein in the lens, whether signaling through VEGF receptors occurs in lens cells, the pattern of VEGF-A expression during lens development, and the effect of hypoxia on VEGF-A expression. METHODS: VEGF-A and VEGFR2 were localized using immunocytochemistry. VEGF-A and VEGFR2 protein were identified and quantified by Western blot analysis. Activated (tyrosine phosphorylated) VEGFR2 was detected by immunoprecipitation with an anti-phosphotyrosine antibody followed by Western blot analysis with antibody to VEGFR2. Levels of VEGF-A mRNA were measured by quantitative PCR. Suturing the lids of adult mouse or rabbit eyes for 3 days was used to induce lens hypoxia. RESULTS: VEGFR2 sequences were present in adult human lens epithelial cells, and VEGF-A transcripts were detected in chicken embryo, adult human, and mouse lens epithelial cells. VEGF-A protein localized to the ends of mouse embryo lens fiber cells at developmental stages when the fetal vasculature was forming. At later stages, VEGF-A was distributed uniformly throughout the cytoplasm of cortical fiber cells. VEGFR2 was present in mouse lens epithelial and fiber cells and was tyrosine phosphorylated at all stages examined. VEGF-A protein was barely detectable in lens epithelial cells during the first postnatal week, but increased as the capillaries of the anterior pupillary membrane regressed. VEGF-A levels were highest in adult lenses. Suturing the eyelid caused an increase in VEGF-A mRNA and protein in lens epithelial and fiber cells. CONCLUSIONS: VEGF-A secreted by lens cells may stimulate the formation of the fetal vasculature, but regression of these vessels is not likely to be caused by a reduction in VEGF-A production by the lens. An active VEGF-A signaling system of unknown function appears to be active in the lens. It is likely that VEGF-A expression is regulated by tissue hypoxia at all stages of lens development.
PURPOSE: Previous studies have identified sequences encoding vascular endothelial growth factor (VEGF)-A and one of the VEGF receptors (VEGFR2, Flk-1, KDR) in lens fiber cells. The current study was undertaken to determine the distribution of VEGF-A protein in the lens, whether signaling through VEGF receptors occurs in lens cells, the pattern of VEGF-A expression during lens development, and the effect of hypoxia on VEGF-A expression. METHODS:VEGF-A and VEGFR2 were localized using immunocytochemistry. VEGF-A and VEGFR2 protein were identified and quantified by Western blot analysis. Activated (tyrosine phosphorylated) VEGFR2 was detected by immunoprecipitation with an anti-phosphotyrosine antibody followed by Western blot analysis with antibody to VEGFR2. Levels of VEGF-A mRNA were measured by quantitative PCR. Suturing the lids of adult mouse or rabbit eyes for 3 days was used to induce lens hypoxia. RESULTS:VEGFR2 sequences were present in adult human lens epithelial cells, and VEGF-A transcripts were detected in chicken embryo, adult human, and mouse lens epithelial cells. VEGF-A protein localized to the ends of mouse embryo lens fiber cells at developmental stages when the fetal vasculature was forming. At later stages, VEGF-A was distributed uniformly throughout the cytoplasm of cortical fiber cells. VEGFR2 was present in mouse lens epithelial and fiber cells and was tyrosine phosphorylated at all stages examined. VEGF-A protein was barely detectable in lens epithelial cells during the first postnatal week, but increased as the capillaries of the anterior pupillary membrane regressed. VEGF-A levels were highest in adult lenses. Suturing the eyelid caused an increase in VEGF-A mRNA and protein in lens epithelial and fiber cells. CONCLUSIONS:VEGF-A secreted by lens cells may stimulate the formation of the fetal vasculature, but regression of these vessels is not likely to be caused by a reduction in VEGF-A production by the lens. An active VEGF-A signaling system of unknown function appears to be active in the lens. It is likely that VEGF-A expression is regulated by tissue hypoxia at all stages of lens development.
Authors: Alexander I Son; Michal Sheleg; Margaret A Cooper; Yuhai Sun; Norman J Kleiman; Renping Zhou Journal: Invest Ophthalmol Vis Sci Date: 2014-03-19 Impact factor: 4.799
Authors: Claudia M Garcia; Ying-Bo Shui; Meera Kamath; Justin DeVillar; Randall S Johnson; Hans-Peter Gerber; Napoleone Ferrara; Michael L Robinson; David C Beebe Journal: Exp Eye Res Date: 2008-08-20 Impact factor: 3.467
Authors: Małgorzata Goralska; Steven Nagar; Lloyd N Fleisher; Philip Mzyk; M Christine McGahan Journal: Invest Ophthalmol Vis Sci Date: 2013-11-19 Impact factor: 4.799
Authors: Peter Baluk; Chun Geun Lee; Holger Link; Erin Ator; Amy Haskell; Jack A Elias; Donald M McDonald Journal: Am J Pathol Date: 2004-10 Impact factor: 4.307
Authors: Yu Chen; Yong-qiu Doughman; Shi Gu; Andrew Jarrell; Shin-ichi Aota; Ales Cvekl; Michiko Watanabe; Sally L Dunwoodie; Randall S Johnson; Veronica van Heyningen; Dirk A Kleinjan; David C Beebe; Yu-Chung Yang Journal: Development Date: 2008-07-24 Impact factor: 6.868