Injectable ECM-mimetic dynamic hydrogels abolish ferroptosis-induced post-discectomy herniation through delivering nucleus pulposus progenitor cell-derived exosomes

Discectomy-induced ferroptosis of nucleus pulposus cells (NPCs) contributes to postoperative lumbar disc herniation (LDH) recurrence and intervertebral disc degeneration (IDD). We discover that nucleus pulposus progenitor cells (NPPCs) could imprint ferroptosis resistance into NPCs through exosome-dependent intercellular transmission of miR-221-3p. Based on these findings, we first develop synthetically-tailored NPPC-derived exosomes with enhanced miR-221-3p expression and NPC uptake capacity, which are integrated into an injectable hydrogel based on extracellular matrix (ECM) analogues. The ECM-mimetic hydrogel (HACS) serves as a biomimetic filler for the post-operative care of herniated discs, which could be facilely injected into the discectomy-established nucleus pulposus (NP) cavity for localized treatment. HACS-mediated in-situ exosome release in the NP cavity enables marked ferroptosis inhibition in NPCs that not only prevents LDH recurrence but also reverses the IDD symptoms, leading to robust restoration of NP structure and functions. In summary, this study offers a promising approach for treating disc herniation.