Inducible Expression of Vascular Endothelial Growth Factor in Adult Mice Causes Severe Proliferative Retinopathy and Retinal Detachment

Abstract

Transgenic mice with vascular endothelial growth factor (VEGF) driven by the rhodopsin promoter (rho/VEGF mice) develop neovascularization that originates from the deep capillary bed of the retina and grows into the subretinal space. In rho/VEGF mice, VEGF expression in photoreceptors begins between postnatal days 5 and 7, the period when the deep capillary bed is developing. An important question is whether or not the developmental stage of the deep capillary bed is critical for occurrence of neovascularization. Also, although rho/VEGF mice are extremely useful for the study of ocular neovascularization, there are some applications for which the early onset of VEGF expression is a disadvantage. In this study, we used the reverse tetracycline transactivator (rtTA) inducible promoter system coupled to either the rhodopsin or interphotoreceptor retinoidbinding protein ( Damage to retinal capillaries resulting in retinal ischemia is a constant feature in diseases complicated by retinal neovascularization. Therefore, the demonstration that vascular endothelial cell growth factor (VEGF) is up-regulated by hypoxia 1,2 focused attention on VEGF as a candidate mediator of retinal neovascularization. Circumstantial evidence suggesting that VEGF plays a role was provided by temporal and spatial correlation of VEGF expression with retinal neovascularization in patients and animal models. 3-8 Inhibition of retinal neovascularization by several different types of VEGF antagonists has demonstrated that VEGF is a necessary stimulatory factor. 9 -13

Cell Type–Specific Regulation of Angiogenic Growth Factor Gene Expression and Induction of Angiogenesis in Nonischemic Tissue by a Constitutively Active Form of Hypoxia-Inducible Factor 1

“…Sustained doxycyclineinducible, retina-specific expression of VEGF 165 in adult transgenic mice caused neovascularization from the deep capillary bed but not from superficial capillaries. 34 These results indicate that increased levels of a single VEGF isoform are not sufficient to cause new vessels to sprout from the superficial vessels. Our data suggest a prominent role for PLGF in the neovascularization induced by AdCA5.…”

Vascular endothelial growth factor in eye disease

“…A transgenic mouse model with excessive expression of VEGF in the photoreceptors driven by an inducible promoter system coupled to either the rhodopsin or interphotoreceptor retinoid-binding protein promoter was developed (Ohno-Matsui et al, 2002). These mice showed evidence that CNV could develop in the neurosensory retina without the need for injury to Bruch's membrane or the outer retinal region when excessive VEGF provided a chemotactic gradient in the neurosensory retina.…”

Angiopoietin 1 inhibits ocular neovascularization and breakdown of the blood–retinal barrier

“…The doxycycline inducible promoter system in transgenic mice is a very useful tool, which in past studies has allowed detailed exploration of the effects of VEGF 19,20 and brain-derived neurotrophic factor in the retina. 21 It requires generation of two transgenic mice, one in which reverse tetracycline transactivator is coupled to a promoter that drives its expression ubiquitously or in a certain tissue.…”

“…These mice were genotyped using the primers above to identify the TRE/ang1 transgene, and to identify the rho/rtTA transgene, the following primers were used, as previously described: forward, GTT TAC CGA TGC CCT TGG AAT TGA CGA GT; reverse, GAT GTG GCG AGA TGC CCT TGG AAT TGA CGA GT. 19,28 To generate mice with doxycyline-inducible expression of Ang1 throughout the body, TRE/ang1 transgenic mice were crossed with transgenic mice in which the reverse tetracycline transactivator is under control of the CMV promoter (CMV/rtTA mice, Jackson Labs, Bar Harbor, ME, USA) to generate TetCMVAng1 double transgenic mice. These mice were genotyped using the primers above to identify the TRE/ang1 transgene, and to identify the CMV/rtTA transgene, the following primers were used: forward, CGC TGT GGG GCA TTT TAC TTT AG; reverse, CAT GTC CAG ATC GAA ATC GTC.…”