PEGylated (3-Cell-Targeting Exosomes from Mesenchymal Stem Cells Improve (3 Cell Function and Quantity by Suppressing NRF2-Mediated Ferroptosis

Background: The depletion of beta cell mass is widely recognized as a significant contributor to the progression of type 2 diabetes mellitus (T2DM). Exosomes derived from mesenchymal stem cells (MSC-EXOs) hold promise as cell-free therapies for treating T2DM. However, the precise effects and mechanisms through which MSC-EXO affects beta cell function remain incompletely understood, and the limited ability of MSC-EXO to target beta cells and the short blood circulation time hampers its therapeutic effectiveness. Methods: The effects of MSC-EXO were investigated in T2DM mice induced by a high-fat diet combined with STZ. Additionally, the high glucose-stimulated INS-1 cell line was used to investigate the potential mechanism of MSC-EXO. Michael addition reactionmediated chemical coupling was used to modify the surface of the exosome membrane with a beta-cell-targeting aptamer and polyethylene glycol (PEG). The beta-cell targeting and blood circulation time were evaluated, and whether this modification enhanced the islet-protective effect of MSC-EXO was further analyzed. Results: We observed that the therapeutic effects of MSC-EXO on T2DM manifested through the reduction of random blood glucose levels, enhancement of glucose and insulin tolerance, and increased insulin secretion. These effects were achieved by augmenting beta cell mass via inhibiting nuclear factor erythroid 2-related factor 2 (NRF2)-mediated ferroptosis. Mechanistically, MSC-EXOs play a role in the NRF2-mediated anti-ferroptosis mechanism by transporting active proteins that are abundant in the AKT and ERK pathways. Moreover, compared to MSC-EXOs, aptamer- and PEG-modified exosomes (Apt-EXOs) were more effective in islet protection through PEG-mediated cycle prolongation and aptamer-mediated beta-cell targeting. Conclusion: MSC-EXO suppresses NRF2-mediated ferroptosis by delivering bioactive proteins to regulate the AKT/ERK signaling pathway, thereby improving the function and quantity of beta cells. Additionally, Apt-EXO may serve as a novel drug carrier for islettargeted therapy.