Prof. Zhou Miao's Team at Guangdong Provincial People's Hospital: Biomimetic Periosteum Promotes Cell Recruitment, Immunomodulation and Angiogenesis to Accelerate Bone Regeneration

Bone healing is a dynamic process involving inflammatory response, stem cell recruitment and differentiation, vascularization and ossification, where the periosteum plays crucial roles throughout. However, clinical bone defects are often accompanied by periosteal loss. Traditional autologous periosteal transplantation faces limitations such as immune rejection and donor shortage. Intramembranous ossification is the primary mechanism for craniofacial bone development. Current artificial periosteum for oral surgery lacks essential functions of immunomodulation, vascularization and osteogenesis. Therefore, developing tissue-engineered periosteum with multifunctional properties mimicking natural periosteum is of great significance for craniofacial bone regeneration.

Recently, Prof. Zhou Miao's team published their latest research "An engineered M2 macrophage-derived exosomes-loaded electrospun biomimetic periosteum promotes cell recruitment, immunoregulation, and angiogenesis in bone regeneration" in Bioactive Materials (IF: 18). Inspired by the temporal sequence of bone healing and periosteal multipotency, the team extracted reparative M2 macrophage exosomes (Exo) and conjugated them with amino- and cholesterol-modified BMSC-specific aptamers (Apt) via 3WJ RNA structure to form engineered exosomes (Ap-NP-Exo). These were then covalently immobilized onto coaxial electrospun membranes with periosteal extracellular matrix (ECM) "shell" and polycaprolactone (PCL) "core" to create biomimetic periosteum (PEC-Apt-NP-Exo).

Experimental results demonstrated this biomimetic periosteum could sustainably release engineered exosomes to promote BMSC migration, enhance BMSC osteogenic differentiation via Rap1/PI3K/AKT signaling pathway, and increase VEGF secretion to facilitate endothelial angiogenesis. After in vivo implantation, it could modulate early-stage M2 macrophage polarization in bone defects, recruit endogenous BMSCs and induce osteogenic differentiation, ultimately accelerating bone regeneration and vascularization (Fig. 1).

Fig. 1: Design of biomimetic periosteum: (1) Coaxial electrospinning to prepare PCL-core/ECM-shell membranes; (2) BMSC-specific aptamer-modified exosomes; (3) Covalent immobilization of engineered exosomes on electrospun membranes. In vivo/vitro results demonstrate PEC-Apt-NP-Exo accelerates bone defect repair by promoting BMSC recruitment, immunomodulation, osteogenesis and angiogenesis via Rap1/PI3K/AKT pathway.

The team prepared decellularized porcine femoral periosteum into coaxial electrospun membranes. Under EDC/NHS catalysis, amino-modified engineered exosomes reacted with carboxyl groups in ECM to form PEC-Apt-NP-Exo. This construct could sustainably release Ap-NP-Exo over 8 days while promoting BMSC growth and osteogenic differentiation (Fig. 2).

Fig. 2: Fabrication and characterization of biomimetic periosteum

Transwell assays showed PEC-Apt-NP-Exo significantly enhanced BMSC migration, with immunofluorescence confirming endogenous BMSC (SSEA4+, CD45-) recruitment to bone defects at 1 week post-implantation (Fig. 3).

Fig. 3: Biomimetic periosteum recruits BMSCs in early-stage bone defects

When culturing bEND.3 cells with supernatant from Exo-treated BMSCs, the team found Exo could promote VEGF secretion from BMSCs, thereby enhancing bEND.3 tube formation. CD31 immunohistochemistry also revealed the most angiogenesis in PEC-Apt-NP-Exo groups (Fig. 4).

Fig. 4: Biomimetic periosteum promotes angiogenesis by increasing VEGF secretion from BMSCs

After 8 weeks, micro-CT and HE staining showed new bone formation positively correlated with Exo loading and Apt modification, with PEC-Apt-NP-Exo demonstrating the most osteogenesis (Fig. 5).

Fig. 5: Biomimetic periosteum promotes critical-size calvarial defect repair in mice

Full paper: https://authors.elsevier.com/sd/article/S2452199X25001379