Injectable Hydrogel Based on Enzymatic Initiation of Keratin Methacrylate for Controlled Exosome Release in Intervertebral Disc Degeneration Therapy

The treatment of intervertebral disc degeneration (IVDD) using bone marrow mesenchymal stem cell-derived exosomes has shown success in alleviating inflammation and restoring the extracellular matrix (ECM), however, challenges persist due to the deficiency in mechanical support and controlled release. Herein, a carbon-carbon double bond modified keratin (KeMA) is synthesized by 2-isocyanatoethyl modification for exosomes wrapping. This injectable KeMA hydrogel, initiated by a biocompatible glucose/ glucose oxidase/ horse radish peroxidase enzymatic cascade reaction with acetylacetone and N-vinylpyrrolidone, displayed rapid gelation, resembling nucleus pulposus (NP) elasticity, and excellent cytocompatibility. In vitro studies showcased that the exosomes-loaded KeMA hydrogel (Exo@KeMA) enhanced exosome release kinetics, suppressed inflammation, fostered extracellular matrix (ECM) regeneration, and reinstated NP biomechanics. RNA-seq analysis indicated Exo@KeMA's effects involved PI3K-Akt signaling for matrix regeneration and NF-kappa B signaling inhibition for anti-inflammation. In vivo IVDD rat models demonstrated Exo@KeMA attenuated inflammation, maintained NP water content, preserved disc height, and promoted structural regeneration. This research introduces an injectable KeMA hydrogel as a promising therapy for IVDD, by facilitating biomechanics restoration, anti-inflammatory response, and ECM regeneration. In this study, an injectable hydrogel is prepared based on enzymatic initiation of keratin methacrylate, which first improved the mechanical environment of the degenerated intervertebral disc, and then released BMSC-exo to promote the activation of the PI3K-AKT pathway for matrix regeneration and simultaneously inhibited the NF-kappa B pathway to reduce the inflammatory necrosis of nucleus pulposus cells, which served to improve the degeneration of the intervertebral disc. image