Role of retinal pigment epithelium‐derived exosomes and autophagy in new blood vessel formation

Abstract

Autophagy and exosome secretion play important roles in a variety of physiological and disease states, including the development of age‐related macular degeneration. Previous studies have demonstrated that these cellular mechanisms share common pathways of activation. Low oxidative damage in ARPE‐19 cells, alters both autophagy and exosome biogenesis. Moreover, oxidative stress modifies the protein and genetic cargo of exosomes, possibly affecting the fate of surrounding cells. In order to understand the connection between these two mechanisms and their impact on angiogenesis, stressed ARPE‐19 cells were treated with a siRNA‐targeting Atg7, a key protein for the formation of autophagosomes. Subsequently, we observed the formation of multivesicular bodies and the release of exosomes. Released exosomes contained VEGFR2 as part of their cargo. This receptor for VEGF—which is critical for the development of new blood vessels—was higher in exosome populations released from stressed ARPE‐19. While stressed exosomes enhanced tube formation, exosomes became ineffective after silencing VEGFR2 in ARPE‐19 cells and were, consequently, unable to influence angiogenesis. Moreover, vessel sprouting in the presence of stressed exosomes seems to follow a VEGF‐independent pathway. We propose that abnormal vessel growth correlates with VEGFR2‐expressing exosomes release from stressed ARPE‐19 cells, and is directly linked to autophagy.

Analysis of Adult Neural Retina Extracellular Vesicle Release, RNA Transport and Proteomic Cargo

“…35 Recent analysis of EVs from RPE describe autophagy conjugate Atg12-Atg5 and other autophagy pathway cargo with predicted roles in cellular homeostasis. 38 EVs from RPE have also been reported to contain αβ crystalline, mediating anti-inflammatory processes and providing neuroprotection. 39 Cortical neurons have been observed to release AMPA receptors in exosomes during heightened excitability, with a predicted role in synaptic remodeling.…”

Oxidative stress‐induced angiogenesis is mediated by miR‐205‐5p

“…25 For several reasons (light, metabolic rate, cellular membrane interactions, etc), RPE is continually exposed to oxidative stress (OS) [26][27][28] ; hence, OS is considered a relevant risk factor for AMD. 20,30,31 Specifically, OS promotes VEGF production in RPE cells, leading to choroidal neovascularization. 20,30,31 Specifically, OS promotes VEGF production in RPE cells, leading to choroidal neovascularization.…”

“…[27][28][29] Recent reports point out that OS in RPE cells intensifies the production and release of angiogenic factors, thus increasing the formation of new blood vessels. 20,30,31 Specifically, OS promotes VEGF production in RPE cells, leading to choroidal neovascularization. 18,32,33 In agreement with this, miR-205-5p overexpression also reduced reactive oxygen species (ROS) by increasing peroxiredoxin 2 levels, 34 suggesting that miR-205-5p could be sensitive to oxidative stimuli.…”

Distinct role of autophagy on angiogenesis: highlights on the effect of autophagy in endothelial lineage and progenitor cells

“…The paracrine activity of endothelial lineage is mostly dependent on the secretion of factors by releasing exosomes [ 127 ]. The induction of autophagy was shown to increase the biogenesis of exosomes carrying endothelial specific factors such as vWF and VEGFR-2 [ 128 , 129 ].…”