Hydrogen-releasing magnesium hydrogel mitigates post laminectomy epidural fibrosis through inhibition of neutrophil extracellular traps.

Epidural fibrosis is a primary contributor to the failure of laminectomy surgeries, leading to the development of failed back surgery syndrome (FBSS). Post-laminectomy, neutrophils infiltrate the surgical site, generating neutrophil extracellular traps (NETs) that contribute to epidural fibrosis. Reactive oxygen species (ROS) play a pivotal role in mediating NETs formation. Molecular hydrogen, recognized for its selective antioxidant properties and biosafety, emerges as a potential therapeutic gas in suppressing epidural fibrosis. In this study, we developed an in-situ hydrogen release hydrogel that inhibits the formation of NETs and mitigates epidural scarring. Biodegradable magnesium (Mg) microspheres served as a hydrogen source, coated with PLGA to regulate hydrogen release. These microspheres (Mg@PLGA) were then incorporated into a PLGA-PEG-PLGA thermosensitive hydrogel (Mg@PLGA@Gel), providing a surgical implant for sustained, long-term hydrogen release. In vitro experiments confirmed the biocompatibility of the system, demonstrating that hydrogen produced by Mg@PLGA effectively neutralizes neutrophil intracellular ROS and inhibits NETs formation. Histological analyses, including H&E staining, MRI, Masson staining, and immunohistochemistry, collectively indicate that Mg@PLGA@Gel is biocompatible and effectively inhibits epidural fibrosis post-laminectomy. Furthermore, Mg@PLGA@Gel inhibits ROS accumulation and NETs formation at the surgical site. These findings suggest that Mg@PLGA@Gel ensures continuous, therapeutic hydrogen concentration, providing relief from epidural fibrosis in a laminectomy mouse model. STATEMENT OF SIGNIFICANCE: •The hydrogen-releasing hydrogel combines the therapeutic effects of a physical barrier with immunomodulation. •In situ-generated molecular hydrogen scavenges ROS caused by surgical stress and suppresses NETs formation. •The hydrogen-releasing hydrogel is demonstrated to exhibit high biocompatibility and inhibit epidural scar formation in vivo.