*Purpose: Ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) and chronic kidney disease (CKD). Damage to microvascular peritubular capillaries (PTC) is a critical determinant of AKI-to-CKD transition after IRI. We previously identified anti-LG3/perlecan autoantibodies in patients with CKD, as a negative prognostic factor for long-term renal function after AKI. We also showed that a new class of extracellular vesicles produced by apoptotic endothelial cells (ApoExo), characterized by the LG3 autoantigen, active 20S proteasome and a specific pattern of immunogenic RNAs, can prompt the production of anti-LG3. Here, we test the hypothesis that ApoExo drive renal inflammation after renal IRI leading to anti-LG3 production, defective microvascular repair and loss of renal function.

*Methods: Renal IRI in mice was performed with renal artery clamping for 30 minutes and contralateral nephrectomy. ApoExo were purified by sequential ultracentrifugation from serum-free medium conditioned by apoptotic murine endothelial cells. ApoExo were injected twice every other day before IRI and thereafter up to eight injections, and end-points were assessed 21 days post-IRI. Interstitial inflammation and tubular damage were scored on hematoxylin-eosin sections. Inflammatory infiltrate, complement activation, PTC rarefaction and fibrosis were assessed with immunohistochemistry for T cells (CD3), B cells (CD20), macrophages (F4/80) and IL-17A⁺ cells, C4d deposition on PTC, MECA-32 staining of PTC and myofibroblasts (α-SMA⁺) differentiation. Anti-LG3 titers were measured by ELISA.

*Results: ApoExo injection enhanced tubular damage (p=0.03) and interstitial inflammation (p=0.03). C4d deposition, PTC rarefaction, and interstitial accumulation of α-SMA⁺ cells were increased in ApoExo treated mice (p=0.009, p=0.01, p=0.04). ApoExo increased anti-LG3 production, which correlated with C4d deposition on PTC and myofibroblasts differentiation (r=0.8, p=0.007 and r=0.7, p=0.03). Mice treated with ApoExo were more infiltrated with CD3 lymphocytes, IL-17A⁺ cells, and macrophages (p=0.004, p=0.002, p=0.007), with lymphocyte aggregates formation and a CD3⁺/CD20⁺/F4/80⁺/IL-17A⁺ cluster reminiscent of early-stage lymphoid-like structures.

*Conclusions: These results identify ApoExo as novel regulators of inflammation after renal IRI, driving anti-LG3 formation, complement activation and lymphocyte infiltration. They also suggest that autoimmune pathways triggered by ApoExo can contribute to microvascular rarefaction and renal fibrosis. Understanding immune mechanisms driven by ApoExo will help determine better strategies to predict and prevent kidney function loss and graft rejection after IRI-induced AKI.

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