Evenly Distributed Microporous Structure and E7 Peptide Functionalization Synergistically Accelerate Osteogenesis and Angiogenesis in Engineered Periosteum

Repairing large bone defects remains a significant clinical challenge. Stem cell is of great importance in bone regeneration, and periosteum is rich in periosteal stem cell, which has a great influence on repairing bone defects. Bioengineered periosteum with excellent biocompatibility and stem cell homing capabilities to promote bone regeneration is of great clinical significance. The E7 peptide (EPLQLKM), which exhibits a specific affinity for mesenchymal stem cells (MSCs), is beneficial for modulating cellular functions. In this study, a unique microporous structured carboxymethyl chitosan/sodium alginate membrane with a proper mass ratio is developed by the addition of Poloxam 407 （P407）, which is then functionalized with the E7 affinitive peptide. This membrane, characterized by its microporous structure and E7 peptide functionalization (CSSA/P/E), not only demonstrated favorable mechanical properties, enhanced hydrophilicity, satisfactory biodegradation profile, and excellent biocompatibility, but also synergistically enhanced MSCs recruitment. It is found to promote the proliferation, spreading, and osteogenic differentiation of MSCs in vitro and to accelerate early periosteal regeneration, bone matrix deposition, and vascularization in vivo, leading to effective regeneration of critical-sized bone defects. Overall, this study presents a robust, cell and growth factor-free strategy for bioengineering periosteum, offering a potential solution for the challenging large size bone defects.