Scaffold-free cell sheet injection results in bone formation.

Area of Science:

• Regenerative Medicine
• Biomaterials Science
• Orthopedic Surgery

Background:

• Mesenchymal stem cells (MSCs) are crucial for bone regeneration.
• Previous work established MSCs cultured as cell sheets with high osteogenic potential.
• Injectable delivery methods are needed for minimally invasive applications.

Purpose of the Study:

• To evaluate the bone-forming capacity of injectable MSC sheets after subcutaneous transplantation.
• To assess the potential of MSC sheets to rescue osteogenic potential in dead bone.

Main Methods:

• Subcutaneous injection of MSC sheets into animal models.
• Radiographic, histological, and gene expression analyses (ALP, OC) for bone formation assessment.
• Three-dimensional computed tomography (3D-CT) for structural evaluation.
• Injection of MSC sheets into dead bone defects.

Main Results:

• Formation of hard masses at injection sites, confirmed as newly formed bone.
• Histology revealed bone matrix, osteocytes, and osteoblasts.
• Gene expression analysis showed high levels of ALP and OC mRNA.
• MSC sheets successfully supplied osteogenic potential to dead bone.

Conclusions:

• Osteogenic MSC sheets can be effectively transplanted via needle injection to form bone in vivo.
• This injectable MSC sheet method represents a minimally invasive approach for hard tissue reconstruction.
• The technique shows potential for applications in bone regeneration and repair.