M2 macrophage−derived exosomes improves secondary lymphedema through cellular mitochondrial homeostasis regulation via the Keap1-Nrf2/mPTP axis

Background: Secondary lymphedema leads to progressive tissue remodeling and immune dysregulation. Dysregulation of macrophage polarization critically influences pathological progression. Oxidative stress and mitochondrial homeostasis are the critical components of secondary lymphedema. Methods: cell injury model were established. Mitochondrial dynamics were evaluated using the ROS assay, mitochondrial membrane potential analysis and mPTP opening assays. Mechanistic investigations included Nrf2 nuclear translocation analysis via immunofluorescence, western blotting, and pharmacological inhibition of exosome biogenesis using GW4869. Results: Secondary lymphedema tissues exhibited a significant imbalance in M1/M2 macrophage infiltration (with an increase in M1 and decrease in M2), along with elevated IL-1β levels. M2-Exo significantly prevents the proliferation, migration, and tube formation of human lymphatic endothelial cells and alleviated the mitochondrial damage induced by LPS. This mechanism may involve activation of Keap1-Nrf2 signaling. Conclusion: M2 macrophage exosomes activated the Nrf2 anti-oxidative stress pathway. This activation improves mitochondrial homeostasis and enhances the function of human lymphatic endothelial cells by delivering active ingredients, offering a new strategy for the treatment of secondary lymphedema.