Vascular endothelial growth factor expression and signaling in the lens
Vascular endothelial growth factor expression and signaling in the lens
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DOI：
10.1167/iovs.02-1226
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发表时间：
2003-09-01
影响因子：
4.4
通讯作者：
Beebe, DC
中科院分区：
文献类型：
--
作者：
Shui, YB;Wang, XH;Beebe, DC
目的。先前的研究已经确定了晶状体纤维细胞中编码血管内皮生长因子(VEGF)-A和VEGF受体之一（VEGFR2, Ftk-1， KDR）的序列。本研究旨在确定晶状体中VEGF- a蛋白的分布，晶状体细胞中是否存在通过VEGF受体传递的信号，晶状体发育过程中VEGF- a的表达模式，以及缺氧对VEGF- a表达的影响。利用免疫细胞化学方法定位VEGF-A和VEGFR2。Western blot检测VEGF-A和VEGFR2蛋白。用抗磷酸酪氨酸抗体免疫沉淀检测激活（酪氨酸磷酸化）的VEGFR2，然后用VEGFR2抗体进行Western blot分析。定量PCR检测VEGF-A mRNA水平。采用缝合成年小鼠或家兔眼睑3 d诱导晶状体缺氧。在成人晶状体上皮细胞中存在VEGFR2序列，在鸡胚、成人和小鼠晶状体上皮细胞中检测到VEGF-A转录本。胚胎脉管系统形成时小鼠胚胎晶状体纤维细胞末端的VEGF-A蛋白。在后期，VEGF-A均匀分布在皮质纤维细胞的细胞质中。VEGFR2存在于小鼠晶状体上皮细胞和纤维细胞中，并且在检查的所有阶段都被酪氨酸磷酸化。在出生后的第一周，晶状体上皮细胞中几乎检测不到VEGF-A蛋白，但随着瞳孔前膜毛细血管的退化而增加。成人晶状体中VEGF-A水平最高。眼睑缝合导致晶状体上皮细胞和纤维细胞中VEGF-A mRNA和蛋白表达升高。晶状体细胞分泌的VEGF-A可能刺激胎儿血管的形成，但这些血管的退化不太可能是由晶状体分泌的VEGF-A减少引起的。一个功能未知的活跃VEGF-A信号系统似乎在晶状体中活跃。VEGF-A的表达可能在晶状体发育的各个阶段受到组织缺氧的调节。
PURPOSE. Previous studies have identified sequences encoding vascular endothelial growth factor (VEGF)-A and one of the VEGF receptors (VEGFR2, Ftk-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.