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Testing a novel target for anti-angiogenesis therapy in the eye

Final Report Summary - ANGIOBLOCK (Testing a novel target for anti-angiogenesis therapy in the eye)

Angiogenesis is a process involved in several pathologies such as age-related macular degeneration (AMD) among others. AMD is a retinal disease characterized by central vision loss produced mainly by new vessels formed from choroidal capillaries (choroidal neovascularization, CNV). Current therapies are directed to inhibition of vascular endothelial growth factor (VEGF); however patients need to be retreated given that the CNV tends to recur. Moreover, sustained blocking of VEGF could report unexpected side effects. It is therefore important to explore alternative molecular targets for the development of AMD effective therapies that can overcome resistance to VEGF targeted approaches. Neuropilin 1 (Nrp1) acts as a co-receptor for several angiogenic ligands and it has also been found to be expressed in the retinal pigment epithelial cells of surgically excised choroidal neovascular membranes. Thus, ANGIOBLOCK was aimed to investigate if blocking Nrp1 is therefore an attractive target to reduce or prevent CNV development. Mutant mice lacking Nrp1 (Nrp1c/c) were created by cre-lox technology (endothelial cell specific, tamoxifen induced Cre-recombination) and were compared with littermate controls. The mouse model used in ANGIOBLOCK is exceptionally efficient and allows gene deletion within 24 hours in close to 100% of active endothelial cells. In the present project, damage was applied to mice’s retinas with a diode laser (532 nm) to reproduce CNV human lesions that were weekly followed to measure their growing and leakage by fluorescein angiographies. In addition, we used cutting edge technology during the follow-up by spectral-domain optical coherence tomography (SD-OCT) that allows us to follow the lesion in vivo with an extremely high resolution and precision. This permits you to identify the lesion area and therefore, the volume and areas observed in the lesions of those animals were measured by software analysis based on the OCT images. We could demonstrate that lesions observed in transgenic animals were smaller in area and volume compared with their littermate controls. However, to properly confirm that the measurements made on the OCT were accurate and corresponded to vessels, a vessel staining (with lectin) was performed on wholemounted posterior eyecups. In addition to the main ANGIOBLOCK objectives, we were able to identify in vivo some hyper-reflecting inflammatory cells around the lesion site using the OCT. This result suggests that Nrp1 would be a valid molecule to further investigate in the CNV blocking. Blocking Nrp1 is therefore an attractive target to block CNV because it mediates the function of multiple angiogenic factors and might overcome VEGF resistance. Soluble forms of Nrp1 have been shown efficacy in some tumour models, hence the results obtained in the present project showing the importance of Nrp1 in the CNV development, could be interesting for the ophthalmology industry, since soluble Nrp1 and Nrp2 isoforms may serve to sequester VEGF in the lesion area. ANGIOBLOCK provides a basis for an alternative therapy for CNV lesions. Therefore, patients that currently do not respond to the gold standard treatment will be benefit from this discovery. However, more studies will be needed to confirm the validity and efficacy of these soluble forms or anti-Nrp1 in CNV lesions.