Injectable Dynamic Hydrogel with Responsive Mechanical Reinforcing Ability Reverses Intervertebral Disc Degeneration by Suppressing Ferroptosis and Restoring Matrix Homeostasis

Abstract Intervertebral disc degeneration (IDD) remains an essential challenge in the clinics due to the ferroptosis of nucleus pulposus cells (NPCs) and the imbalance of extracellular matrix (ECM) metabolism. Here, a dynamic hydrogel (HPGO) based on oxidized hyaluronic acid (OHA) and polyvinyl alcohol (PVA) for the integration of oridonin (Ori)‐loaded NPC membrane‐based nanovesicles is proposed, which is further grafted with growth and differentiation factor 5 (GDF5) on the OHA chain via Schiff base ligation. The precursors can rapidly form mechanically resilience hydrogels after injection into nucleus pulposus (NP) through the formation of various dynamic bonds. Meanwhile, the acidic pH in the degenerated NP can trigger the responsive release of GDF5, which may cooperate with Ori to alleviate inflammation in the microenvironment for restoring the metabolic homeostasis of ECM. In addition, the Schiff base moieties in HPGO hydrogel can scavenge free ferrous ions in the microenvironment to strengthen the dynamic bonds for self‐regulated reinforcement, thus providing mechanical support for the degenerated intervertebral discs (IVDs). Furthermore, HPGO hydrogel can enhance ferroptosis resistance of NPCs by activating the nuclear factor erythoid 2‐related factor 2 signaling pathway. Overall, HPGO hydrogel can mechanically support the damaged IVDs as well as reversing their degenerative status through cooperative ferroptosis inhibition, which provides an approach for the clinical treatment of IDD.