Ras pathway inhibition prevents neovascularization by repressing endothelial cell sprouting

Abstract

Vascular networks develop from a growing vascular front that responds to VEGF and other guidance cues. Angiogenesis is required for normal tissue function, but, under conditions of stress, inappropriate vascularization can lead to disease. Therefore, inhibition of angiogenic sprouting may prevent neovascularization in patients with blinding neovascular eye diseases, including macular degeneration. VEGF antagonists have therapeutic benefits but also can elicit off-target effects. Here, we found that the Ras pathway, which functions downstream of a wide range of cytokines including VEGF, is active in the growing vascular front of developing and pathological vascular networks. The endogenous Ras inhibitor p120RasGAP was expressed predominately in quiescent VEGF-insensitive endothelial cells and was ectopically downregulated in multiple neovascular models. MicroRNA-132 negatively regulated p120RasGAP expression. Experimental delivery of α-miR-132 to developing mouse eyes disrupted tip cell Ras activity and prevented angiogenic sprouting. This strategy prevented ocular neovascularization in multiple rodent models even more potently than the VEGF antagonist, VEGF-trap. Targeting microRNA-132 as a therapeutic strategy may prove useful for treating multiple neovascular diseases of the eye and for preventing vision loss regardless of the neovascular stimulus.

Roles of Hypoxia Response in Retinal Development and Pathophysiology

“…However, another target is now required because it has become clear that VEGF antagonism may induce retinal atrophy, in some cases. We confirmed a microR-NA as a candidate for the alternative target for neovascular retinal diseases 40 (Fig. 6).…”

Neurovascular crosstalk between interneurons and capillaries is required for vision

“…Whole-mount preparations were performed after removing the cornea, lens, retina pigment epithelium, choroid, and sclera as previously described (36,37). Immunostaining of cryosections or vibratome sections (100 μm) was carried out as previously described (36) We report here a function for amacrine cells, generating VEGF for vascular maintenance, photoreceptor homeostasis, and visual function. Amacrine and horizontal cells were previously thought to be required only for preprocessing and integrating visual stimuli.…”

“…ERG was performed according to procedures previously described (23,36). Mice were dark-adapted overnight before the experiments and anesthetized under a dim red light by intraperitoneal injection of 15 mg/kg ketamine and 7 mg/kg xylazine.…”

Endothelial microRNA-150 is an intrinsic suppressor of pathologic ocular neovascularization

“…Moreover, dysregulation of miRNA is associated with many diseases, such as cancer and heart diseases, and are being developed as important biomarkers (12,13). In neovascular diseases, both pro-and antiangiogenic miRNAs were identified in vascular ECs and perivascular cells (8,13,14). However, it is not well understood whether miRNAs are intrinsically regulated in proliferative blood vessels to influence ocular vascular diseases.…”