A novel phage display-identified nucleus pulposus-targeting peptide enhances exosome therapy for intervertebral disc...

Intervertebral disc degeneration (IVDD) is driven by progressive loss of nucleus pulposus cell (NPC) homeostasis, yet therapeutic delivery to NPCs remains limited by the avascular, dense disc microenvironment and the lack of cell-selective ligands. Here, cell-based phage display identified a novel NPC-affinitive peptide, EYFNSPKYDLYR (NTP), which exhibited preferential affinity for NPCs over annulus fibrosus cells and endplate chondrocytes. NTP was incorporated onto mesenchymal stem cell-derived exosomes (MSC-exo) through DSPE-PEG-mediated post-insertion to generate NTP-modified, NPC-targeted MSC-derived exosomes (NT-EXO). NT-EXO retained typical exosomal characteristics while exhibiting enhanced NPC uptake and improved early intradiscal retention. In TBHP-injured NPCs, NT-EXO restored ACAN and COL II expression and reduced MMP13 expression. Molecular analyses further showed partial restoration of miR-142-3p, miR-199a, and miR-217, accompanied by regulation of their reported downstream molecules and attenuation of endoplasmic reticulum stress- and apoptosis-associated transcriptional responses. In a rat puncture-induced IVDD model, NT-EXO improved MRI degeneration grade, disc architecture, proteoglycan preservation, and matrix-marker expression more effectively than unmodified MSC-exo. These findings establish NTP as a functional NPC-targeting ligand and provide preclinical proof-of-concept that cell-selective surface engineering can improve exosome delivery and therapeutic performance in IVDD.