Extracellular vesicles from retinal pigment epithelium: Key players in the outer blood‐retinal barrier disruption and choroidal neovascularization in age‐related macular degeneration

Aims/Purpose: Age‐related macular degeneration (AMD), a degenerative disease causing irreversible central vision loss in the elderly, is characterized by dysregulation of the retinal pigment epithelium (RPE). During AMD, stressed RPE releases extracellular vesicles (EVs) carrying bioactive cargo, potentially disrupting the outer blood‐retinal barrier (oBRB) and accelerating AMD progression. Mechanisms behind EV‐induced oBRB disruption and their role in choroidal neovascularization (CNV) are unclear. Our study aims to assess how RPE‐derived EVs under inflammatory conditions impact oBRB integrity and CNV in AMD. Methods: We used highly polarized primary cultures of porcine RPE (pRPE), porcine eyecups with the RPE exposed, and human umbilical vein endothelial cells (HUVEC). RPE and HUVEC cells were treated with TNF, LPS, or EVs derived from inflamed RPE cells. Additionally, Balb/c mice were intravitreally injected with RPE‐derived EVs. Results: Treatment with TNF or LPS reduced the transepithelial resistance (TER) of pRPE cells monolayer and disrupted the tight junction complexes. Although inflammatory stimuli reduced EVs release from the apical membrane of RPE cells, increased CD63 levels and MMPs levels and activity were found in EVs. Moreover, these EVs led to the disruption of the RPE monolayer. In the Matrigel assay of HUVEC, angiogenesis was induced by both TNF and LPS, and by RPE‐derived EVs isolated after the LPS stimulus. At seven days following intravitreal injection, EVs induced outer retinal structural changes in the Balb/c mice. Conclusions: Our study indicates that EVs released from RPE cells following an inflammatory insult contribute to the oBRB disruption and induce neovascularization, indicating that EVs may play a key role in the onset and progression of AMD. Support: GOAP, Bayer; FCT, Portugal: 2020.04811.BD (to BM), PEst UIDB/04539/Base/2020 and UIDP/04539/Programatico/2020 through POCI‐01‐0145‐FEDER‐007440, CENTRO‐01‐0145‐FEDER‐000008: BRAINHEALTH2020