Photobiomodulation‑Engineered Extracellular Vesicles Enhance Neural Differentiation via UFL1‑Mediated UFMylation in Spinal Cord Injury

ABSTRACT Spinal cord injury (SCI) often results in permanent motor dysfunction, and no approved therapy effectively promotes nerve regeneration. We show that engineered extracellular vesicles (EVs) from photobiomodulation (PBM)‐treated microglia, delivering UFL1 (the sole E3 ligase of the UFMylation system), significantly enhance neural repair after SCI. PBM (850 nm, 2.0 J/cm 2 ) promoted microglial M2 polarization and suppressed M1. We isolated PBM‐EVs and identified UFL1 as the key effector via proteomic analysis. Mechanistically, UFL1 competes with MDM2 for p53 binding, inhibiting p53 ubiquitination and degradation, thus stabilizing p53 and activating its signaling. In vitro, PBM‐EV‐delivered UFL1 protected neural stem cells from inflammation‐induced apoptosis and promoted neuronal differentiation; these effects were markedly attenuated by UFL1 knockdown or p53 inhibition. In a rat SCI model, PBM‐EVs delivering UFL1 significantly improved the local immune microenvironment, promoted M2 microglial polarization, reduced glial scar formation, and enhanced axonal regeneration and hindlimb motor recovery. Pharmacological p53 inhibition with PFT‐α or UFL1 knockdown in donor EVs substantially diminished these therapeutic effects in vivo, confirming the central role of the UFL1/p53 axis. Overall, PBM‐EVs deliver UFL1 to activate p53 signaling, synergistically regulating immunity and neural differentiation to promote functional recovery, highlighting the UFL1/p53 axis as a therapeutic target for SCI.