Human umbilical cord mesenchymal stromal cell-derived exosomes from MSCs pretreated with inflammatory factors attenuate renal injury of diabetic mice by regulating macrophage polarization

Diabetic nephropathy (DN), a major complication of diabetes mellitus (DM), is characterized by severe clinical manifestations, impaired quality of life, and a high risk of progression to end-stage renal disease, underscoring the urgent need for effective therapeutic interventions. Mesenchymal stromal cell-derived exosomes (MSC-Exo) have emerged as promising candidates for mitigating inflammatory injury in DN due to their immunomodulatory properties, and exosomes derived from MSCs pretreated with inflammatory factors such as TNF-α and IFN-γ may possess enhanced therapeutic potential. In this study, exosomes isolated from human umbilical cord MSCs were characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blotting. Their therapeutic effects were evaluated in diabetic mice, focusing on renal inflammation and macrophage polarization. Both normal MSC-Exo (Norm-Exo) and TNF-α&IFN-γ-pretreated MSC-Exo (TNF-α&IFN-γ-Exo) effectively ameliorated kidney injury and promoted M2 macrophage polarization, with TNF-α&IFN-γ-Exo showing superior efficacy. High-glucose-stimulated RAW264.7 cells were used to explore the underlying mechanisms, and high-throughput RNA Sequencing identified inhibitor of DNA binding 3 (ID3) as a molecule involved in MSC-Exo-regulated macrophage polarization. Loss-of-function experiments confirmed that ID3 knockdown alone recapitulated the effects of exosomes, promoting M2 polarization and suppressing M1 markers. Conversely, ID3 overexpression attenuated exosome efficacy. Mechanistically, ID3 partially mediated exosome-induced inhibition of the NF-κB pathway. The translational relevance of these findings was further validated in PMA-differentiated THP-1 human macrophages. Collectively, these findings demonstrate that MSC-Exo-particularly TNF-α&IFN-γ-Exo-attenuate diabetic renal injury by modulating macrophage polarization through ID3 regulation, highlighting a novel cell-free immunomodulatory approach for DN therapy.