AMSC-EVs attenuate acute kidney injury through TXNIP-IKKα/NFκB signaling-mediated renal CX3CR1(+) macrophage polarization.

BACKGROUND: Extracellular vesicles generated from mesenchymal stem cells (MSC-EVs) have garnered significant attention as a cell-free treatment option for acute kidney injury (AKI). The fundamental processes and capabilities of MSC-EVs in attenuating kidney injury are still largely unclear. METHODS: The AKI mouse model was established by intraperitoneal injection of cisplatin. AKI mice were further randomized to receive Phosphate- Buffered Saline, adipose-derived mesenchymal stem cell-extracellular vesicles (AMSC-EVs (50 µg), or AMSC-EVs (100 µg) into the tail vein. Following a 96-hour post-injury period, the mice were euthanized, and kidney tissues together with blood samples were procured for paraffin embedding and immunoblotting. To investigate the relationship between AMSC-EVs and renal CX3CR1(+) macrophages, CX3CR1(+) macrophage-specific conditional knockout mice (CX3CR1-Cre+/-; Rosa26-LSL-DTR+/-) were generated. Additionally, overexpression of experiments of thioredoxin-interacting protein (TXNIP) were conducted to analyze macrophage polarization and TXNIP-IKKα/NFκB signaling pathway expression. RESULTS: In mice, AMSC-EVs reduced the renal tubule damage and ameliorated cisplatin-induced AKI in a dose-dependent manner. However, in the CX3CR1(+) macrophage ablated group, AKI mice exhibited more severe renal tubular pathology compared to littermate controls, suggesting diminished therapeutic efficacy of AMSC-EVs post CX3CR1(+) macrophage ablation. Meanwhile, AMSC-EVs promoted polarization of renal CX3CR1(+) macrophages towards reparative M2 macrophages, leading to increased production of anti-inflammatory factors and subsequent alteration of the inflammatory microenvironment in renal tubular cells, thereby facilitating the self-repair process in AKI mice. Mechanistically, AMSC-EVs suppressed the protein expression of TXNIP-IKKα/NFκB in renal CX3CR1(+) macrophages. Finally, overexpression of TXNIP appeared to attenuate the protective effects of AMSC-EVs in renal CX3CR1(+) macrophages. CONCLUSIONS: Our study findings suggest that AMSC-EVs modulate the polarization of renal CX3CR1(+) macrophages and promote renal self-recovery following cisplatin-induced AKI through the TXNIP-IKKα/NFκB signaling pathway.