NELL-1-loaded GelMA-fibrinogen crosslinked hydrogel maintains periosteum stability to promote stem cell enrichment and osteogenesis

Jawbone defects pose significant challenges for oral implantation and restoration. Guided bone regeneration is the most common strategy for bone augmentation. However, inadequate efficiency of osteogenesis remains a persistent issue. Periosteum serves as a potential source of osteogenesis, but insufficient mesenchymal stem cells (MSCs) in periosteum often exist due to the lack of initial bone support. Inadequate blood supply near the submembranous osteogenic region also impedes the osteogenesis process. This paper proposes a dual cross-linked natural protein-derived hydrogel, GelMA-fibrinogen/NELL-1(GFN), which optimizes both physical and biological factors to stabilize the elevated maxillary sinus membrane (MSM) (an anatomical structure involved in osteogenesis in maxillary posterior dental region, resembling periosteum) and support the osteogenic space. The results showed stem cells derived from the membrane could migrate to GFN and exhibit robust proliferation capability. Under osteogenic induction, the adequately expanded MSM-derived MSCs enhanced osteogenic differentiation under the synergetic guidance of fibrinogen and Nell-1 through TGF-β/HIF-1α/β-catenin signaling pathway. In vivo experiments showed that GFN could promote bone formation with double-layered cortical bone structures in maxillary sinus region, which provides a new direction for construction of bone grafting materials.