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Amir Hajrasouliha, Guomin Jiang, Wei Wang, Henry Kaplan, Hui Shao; Exosomes Released From Retinal Astroglial Cells (RACs) Contain Anti-Angiogenic Components That Can Suppress Active Vessels In a Laser-induced CNV Model. Invest. Ophthalmol. Vis. Sci. 2013;54(15):340.
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We previously reported that exosomes from RAC could suppress retinal vascular leakage and inhibit choriodal neovascularization (CNV) in a laser-induced CNV model. Here, we aimed to identify anti-angiogenic components in RAC exosomes that might exert their function.
Exosomes released from cultured murine RAC or retinal pigmented epithelium (RPE) were isolated. Exosome proteins were extracted and blotted with Mouse Angiogenesis Array Kit. In some experiments exosomes were treated with FN-439 (1ug/ml), a matrix metalloproteinase (MMP) inhibitor, prior to harvesting. CNV in C57BL/B6 mice was induced by 4 laser spots (50um diameter at 250mV, 0.5s energy) around the optic disc. Mice with CNV were injected periocularly (in sub-Tenon’s space) with PBS or derived exosomes daily starting on day 0. On day 7 the incidence of leaking vessels was observed in vivo by fluorescein-labeled dextran perfusion and fluorescence microscopy. The area of new vessel formation in the choroid was determined in choroid flat mounts using fluorescent microscopy.
Using angiogenesis array kit, we detected endostatin (an endogenous inhibitor of angiogenesis), MMP-3 and MMP-9 in RAC exosomes and not in RPE exosomes. RAC exosomes also expressed higher levels of pigment epithelium-derived factor (PEDF) and tissue inhibitors of metalloproteinases (TIMP-1) than those in RPE exosomes, both PEDF and TIMP-1 being anti-angiogenic factors. In contrast, RPE exosomes contained high levels of angiogenesis related factors such as placenta growth factor-2. We further used FN-439 to block MMPs in the cleavage of collagen XVIII to form endostatin. Retinal vascular leakage was suppressed after treatment with RAC exosomes, and FN-439 completely reversed the effect (33%, 0%, 30%, P<0.05), whereas the inhibition of RAC exosomes on choroidal neovascularization area could not be fully reversed by FN-439 treated exosomes
We showed that RAC exosomes contain multiple anti-angiogenic components, among which endostatin might be important for maintaining vascular barrier. By identifying additional components and their functions of RAC exosomes, we might improve the anti-angiogenic therapy for CNV in AMD and diabetic retinopathy.
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