Abstract / Summary
Urethral injury remains a significant clinical challenge, often leading to complications such as stricture formation due to persistent inflammation, oxidative stress, and fibrosis. Current treatments, including catheterization and surgical reconstruction, focus on anatomical repair but fail to address the underlying pathological microenvironment. To overcome these limitations, this study developed an injectable, multifunctional hydrogel system combining a chitosan-phosphate matrix with hollow cerium oxide nanozymes (CeO 2 ) for comprehensive urethral repair. The hydrogel provides antibacterial protection and controlled drug release, while the CeO 2 nanozymes scavenge reactive oxygen species (ROS) and promote anti-inflammatory macrophage polarization. Additionally, sustained rapamycin delivery inhibits fibrosis, addressing key challenges in urethral healing. In vitro studies demonstrated that the rapamycin-loaded and CeO 2 -modified hyaluronic acid (Gel/Na/Ra) system effectively suppressed pro-inflammatory cytokine secretion, reduced intracellular and mitochondrial ROS accumulation, and protected urothelial cells from H₂O₂-induced apoptosis. In a rabbit urethral defect model, the system significantly reduced stricture formation, promoted epithelial regeneration with organized muscle bundles, and suppressed local and systemic inflammation. Mechanistically, single-cell transcriptomic analysis revealed that Gel/Na/Ra treatment downregulated pro-inflammatory macrophage secretory factors, enhanced extracellular matrix remodeling, and attenuated intercellular communication intensity via the CD44 signaling axis. Functional validation confirmed that CD44 mediates M2 macrophage polarization and ECM-related genes expression. Together, these findings establish the Gel/Na/Ra hydrogel as a multifunctional, cell-free platform that simultaneously modulates oxidative stress, inflammation, and fibrosis, offering a promising strategy for regenerative urethral repair with potential applications in other tubular organ injuries.