Mesenchymal stem cell extracellular vesicles for ischemic retinal damage

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Central retinal artery occlusion (CRAO) is an ophthalmological emergency with few proven therapies. Stem cell-based retinal cell replacement is a highly encouraging approach to achieve retinal neuroprotection and to save vision in retinal diseases. However, with limitations including few cells integrated, adverse immune re- sponses, and aberrant growth, an alternative cell-free approach is required. EVs are nano-vesicular bodies that, when endocytosed by target cells, trigger specific responses. Here, the microRNA (miRNA) cargo of the EVs plays a key role. This proposal targets restoration of retinal function using engineered MSC-EVs containing function-specific miRNA. Compared to MSCs, their EVs are non-immunogenic, non-tumorigenic, and modifiable for specific delivery modes. These characteristics render them ideal biomimetic agents fitting precision-based medicine. Our studies indicate that EVs can rescue retinal cells that have been acutely subjected to hypoxia or ischemia, the key mechanism that starts cells dying in CRAO. We also found that hypoxic preconditioning of MSCs resulted in EVs (H-EVs) with enhanced cytoprotective properties including anti-apoptosis and anti-inflam- mation. A number of miRNAs overexpressed in the H-EVs have cytoprotective properties in retinal cells. Our central hypothesis is that targeted EV-specific expression of miR-424/other key miRNAs in MSC-EVs will re-capitulate the anti-apoptosis and anti-inflammatory actions of H-EVs. We designate such EVs as Func- tionally Engineered EVs (FEEs). To facilitate clinical translation of MSC-EV therapy, we have identified key fun- damental knowledge gaps: (1) The relationship between EV miRNA and its anti-apoptotic properties; (2) EV miRNA and its role in anti-inflammatory actions of MSC-EVs in retina; and (3) Can MSC-EVs be enhanced for targeted functionality by engineering their miRNA cargo? In Aim 1 we will produce FEEs overexpressing miR- 424 (FEE-424) and 146b (FEE-146b). We will evaluate the mechanisms of action of the FEEs, and their candi- dacy for generation of FEEs in retinal ganglion cells, microglia, Muller cells, and retinal vascular endothelial cells using loss and gain of function studies in models of simulated ischemia in vitro. These results will serve as a proof-of-principle model for development of FEEs for amelioration of cell damage in the retina. In Aim 2, FEEs containing miR-424 and -146b will be used to test specific targeting of anti-apoptotic and inflammatory mecha- nisms in a rodent model of CRAO. Overall, the proposed studies are expected to provide transformative results whereby MSC-EVs are modified and delivered for retinal protective action after the ischemic event to treat CRAO. Innovations are cell-free therapy of retinal diseases, EV miR-mediated application-specificity, and direct determination of the impact of EVs on specific cells involved in retinal ischemic injury. Translational significance is the high likelihood of impacting novel molecular therapy. Underlying basic research significance is that the studies will enable vertical advancement of the field by determining mechanisms of actions of EVs in the retina.