We are pleased to announce that Prof. Elita Montanari (Università degli studi Roma Tre, Italy) will join Targeting Extracellular Vesicles 2026 as a speaker.

Delivering nucleic acids to the retina remains a major challenge. Today, most approved approaches rely on adeno-associated viruses, or AAVs, to deliver DNA. Although powerful, AAVs have important limitations, including limited cargo capacity, possible immune reactions, and challenges linked to patient acceptance. Synthetic lipid nanoparticles are another option, but they may also trigger inflammatory responses.

To explore a safer and more flexible alternative, we developed a non-viral delivery platform based on human blood-derived extracellular vesicles. The objective was to use these natural vesicles to deliver messenger RNA to retinal cells.

We tested three different types of human blood-derived EVs. Each of them was able to spontaneously fuse with lipid nanovectors carrying mRNA, forming hybrid extracellular vesicles. These hybrid EVs showed very high mRNA loading efficiency, above 90%, and strong hybridization between EVs and lipid nanovectors, above 85%.

Importantly, all three hybrid EV formulations were well tolerated by human retinal pigment epithelial cells. However, they did not behave in exactly the same way. Their uptake and transfection efficiency differed, suggesting that each EV type may have its own natural tropism. Among them, one formulation, called hb-hEV-1, showed the best uptake and the most reproducible transfection capacity.

This selected formulation was then tested in healthy mice using two routes of administration: subretinal and intravitreal injection. hb-hEV-1 carrying mCherry mRNA showed a safe profile. After subretinal injection, it mainly transfected retinal pigment epithelium cells. After intravitreal injection, it reached some Müller glia and retinal pigment epithelium cells.

These findings suggest that combining selected extracellular vesicles with lipid nanovectors can create a modular and efficient platform for retinal mRNA delivery. One of the most interesting aspects is the possibility of reaching deeper retinal layers, even through intravitreal injection, which remains difficult with many current delivery systems.

This approach could open new therapeutic opportunities for genetic eye diseases that are still difficult or impossible to treat. It may also contribute to the development of safer, targeted, semi-autologous and personalized RNA-based therapies.

More broadly, this work presents a highly efficient strategy for loading mRNA into natural EVs while preserving their biological functionality. This could help expand the use of EVs as gene-therapy carriers in ophthalmology and beyond.

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