Therapeutic potential of red blood cell-derived extracellular vesicles in reducing neuroinflammation and protecting against retinal degeneration.

Neuroinflammation is a pathological process mediated through immune cell activation and pro-inflammatory cytokine release, resulting in neuronal cell death. In the central nervous system (CNS), neuroinflammation is a characteristic feature underlying the onset and progression of retinal and neurodegenerative diseases. Targeting neuroinflammation to reduce neuronal cell death and protect against visual and cognitive declines is therefore a key therapeutic strategy. However, due to the complex and multi-faceted nature of these diseases, to date there has been little therapeutic success with single target approaches insufficient to tackle widespread and multi-pathway inflammatory cascades. Furthermore, as the retina and brain reside within immune-privileged environments, a major challenge in treating these diseases is producing and delivering a therapeutic that, in itself, does not exacerbate inflammation. Extracellular vesicles (EV), derived from red blood cells (RBC EV), present a promising solution to overcome these hurdles, due to their innate ability to cross blood-tissue barriers, biocompatible nature, and their broad anti-inflammatory properties to modulate complex neuroinflammatory pathways. This study therefore investigated the therapeutic potential of RBC EV in mediating neuroinflammation using an in-vivo photo-oxidative damage model of retinal degeneration as a model for CNS neuroinflammation. In this work, we developed a novel incubation pipeline using N1 medium supplement and superoxide dismutase (SOD) supplementation to promote the production of safe, neuroprotective, and anti-inflammatory RBC EV. Delivery of RBC EV in vivo, was shown to be safe with strong penetration across all retinal layers. Further, therapeutic administration of RBC EV via local intravitreal injection significantly reduced inflammation and cell death and preserved retinal function. Notably, strong safety and therapeutic efficacy was also demonstrated in the retina following systemic (intraperitoneal) administration, highlighting a potential game-changing approach for less-invasive therapeutic delivery to the CNS. Finally, multi-omic analyses and in vitro findings supported an anti-inflammatory mechanism-of-action, with RBC EV modulating pro-inflammatory cytokine release, including those known to be involved in the pathogenesis of retinal and neurodegenerative diseases. Taken together, these findings highlight the broad applicability of RBC EV in treating neuroinflammation in the CNS, presenting a scalable and effective treatment approach for these currently untreatable diseases.