Purpose
To investigate the distribution of VEGFR-1, -2 and -3 in the mouse retina and choroid in laser-induced CNV and to elucidate the effect of Notch activation on these receptors. Notch activation in endothelium leads to an inhibition of angiogenesis in postnatal blood vessel development. Effects on VEGF receptors in the adult retinal and choroidal vascular network have not yet been analyzed.
Methods
Notch intracellular domain (NICD) is the nuclear transcription factor in Notch signaling. NICD gain of function (GOF) mice were laser-treated. Gene expression of VEGFR-1, -2 and 3, of VEGF-A and -C and of Notch-related genes (Jag-1, Dll4, Hey-1, Hes-1) and PECAM-1 were analyzed and in-vivo angiography performed. The distribution of VEGFR-1, -2 and -3 were analyzed immunhistochemically in C57Bl/6 mice.
Results
Immunhistochemically, membrane-associated VEGFR1 was expressed in the ganglion cell (GC) layer and was only partially associated to blood vessels. VEGFR2 was expressed in the GC layer and weaker in the inner and outer nuclear layer. In CNV, VEGFR2 was not associated specifically to vessel walls but to isolectin B4 (IB4) negative cells in the vessels. The IB4 levels of the neovascular vessel were increased. VEGFR3 could be visualized in the GCs and their axons and in the ILM, in the outer plexiform layer and weakly in the inner plexiform layer. Gene expression analysis showed a strong increase of VEGF-A and -C and VEGFR1 early after laser treatment in NICDGOF mice and a lesser increase of VEGFR2>3. Notch-related genes were upregulated and PECAM1 levels were reduced. These changes diminished over time. 14 days after laser, VEGF-A,-C and VEGFR2 and -3 were decreased. PECAM1 was still reduced. Angiographic analysis on day 7 showed a markedly reduced hyperfluorescence in laser spots of NICDGOF mice compared to littermate controls.
Conclusions
For the first time, the distribution of VEGFR3 in the retina and choroid was described and investigated as a possible target for angiogenic changes in the adult eye. We could show decreased PECAM1 levels in NICDGOF mice which, together with the observations in angiography, might be due to a lesser amount of endothelial cells. Notch could be a therapeutical target in eye diseases with uncontrolled vessel growth due to its effect on VEGF receptors and their ligands and to reduced vascular permeability.
Keywords: 453 choroid: neovascularization •
674 receptors •
412 age-related macular degeneration