Heterogeneous porous hypoxia-mimicking scaffolds propel urethral reconstruction by promoting angiogenesis and regulating inflammation

The nasty urine microenvironment (UME) impedes neourethral regeneration by inhibiting angiogenesis and inducing an excessive inflammatory response. Cellular adaptation to hypoxia improves regeneration in numerous tissues. In this study, heterogeneous porous hypoxia-mimicking scaffolds were fabricated for urethral reconstruction via promoting angiogenesis and modulating the inflammatory response based on sustained release of dimethyloxalylglycine (DMOG) to promote HIF-1α stabilization. Such scaffolds exhibit a two-layered structure: a dense layer composed of electrospun poly (l-lactic acid) (PLLA) nanofibrous mats and a loose layer composed of a porous gelatin matrix incorporated with DMOG-loaded mesoporous silica nanoparticles (DMSNs) and coated with poly(glycerol sebacate) (PGS). The modification of PGS could significantly increase rupture elongation, making the composite scaffolds more suitable for urethral tissue regeneration. Additionally, sustained release of DMOG from the scaffold facilitates proliferation, migration, tube formation, and angiogenetic gene expression in human umbilical vein endothelial cells (HUVECs), as well as stimulates M2 macrophage polarization and its regulation of HUVECs migration and smooth muscle cell (SMCs) contractile phenotype. These effects were downstream of the stabilization of HIF-1α in HUVECs and macrophages under hypoxia-mimicking conditions. Furthermore, the scaffold achieved better urethral reconstruction in a rabbit urethral stricture model, including an unobstructed urethra with a larger urethral diameter, increased regeneration of urothelial cells, SMCs, and neovascularization. Our results indicate that heterogeneous porous hypoxia-mimicking scaffolds could promote urethral reconstruction via facilitating angiogenesis and modulating inflammatory response.