Lymphatic incorporated biomimetic scaffold enhances Osteoangio-lymphogenic coupling via HIF-1α mediated mitochondrial reprogramming for osteoporotic bone repair

Recent studies have challenged the notion that bone tissue lacks lymphatic vessels, highlighting their essential role in bone regeneration. Effective bone repair relies on the interplay of osteogenesis, angiogenesis, and lymphangiogenesis. Here, we present a three dimensional-printed biomimetic Gelatin methacryloyl/icariin@Mesoporous silica nanoparticle/Hydroxyapatite (GelMA/ICA@MSN/HAp) scaffold designed to recruit bone marrow mesenchymal stem cells (BMSCs), human umbilical vein endothelial cells (HUVECs), and lymphatic endothelial cells (LECs), enabling these cells to self-assemble into "cell islands" that coordinate tissue regeneration. The scaffold exhibits excellent biocompatibility, biodegradability, and sustained cytokine release. In vitro, it promotes the migration, proliferation, and lineage-specific differentiation of BMSCs, HUVECs, and LECs. In an osteoporotic bone defect model, the scaffold significantly enhances new bone formation, supports vascular remodeling by recruiting HUVECs, and induces lymphatic maturation via LECs, accompanied by upregulation of bone morphogenetic protein 2, vascular endothelial growth factor, and prospero homeobox protein 1. Transcriptomic analysis identifies activation of the hypoxia-inducible factor 1 alpha (HIF-1α) signaling pathway as crucial to these effects. Mechanistically, LECs-derived conditioned medium stimulates HUVECs angiogenesis and BMSCs osteogenesis by inducing HIF-1α mediated mitochondrial metabolic reprogramming. This is the first study to integrate lymphatic modulation into scaffold design for bone repair, achieving osteo-angio-lymphogenic coupling and establishing a novel organoid model for bone regeneration.