Injectable tissue-engineered bone repair of a rat calvarial defect

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Orthopedic Surgery

Background:

• Minimally-invasive delivery of tissue-engineered bone (TEB) is advancing bone repair.
• Injectable biopolymers offer a promising approach for TEB delivery.
• Chitosan-based gels combined with growth factors and cells are being explored for bone regeneration.

Purpose of the Study:

• To evaluate the efficacy of an injectable TEB formulation in a rat calvarial critical size defect (CSD) model.
• To assess the role of mesenchymal stem cells (MSCs) and bone morphogenetic protein-2 (BMP-2) in enhancing bone formation.
• To investigate cell viability and proliferation using green fluorescent protein (GFP)-labeled MSCs.

Main Methods:

• A prospective, controlled trial was conducted in 30 male rats with 8-mm calvarial CSDs.
• Defects were treated with chitosan gel, gel with MSCs, gel with BMP-2, or gel with both MSCs and BMP-2; a control group received no treatment.
• Bone regeneration was assessed at 4 and 8 weeks using microcomputed tomography (micro-CT), histology, and immunohistochemistry.

Main Results:

• All treated groups showed new bone growth in the defects.
• The combination of chitosan gel, MSCs, and BMP-2 resulted in a significant time-dependent increase in bone volume and area (P < .001) compared to other groups.
• Histology confirmed enhanced bone formation, and GFP-labeled TEB indicated MSC viability and contribution to new bone.

Conclusions:

• An injectable TEB formulation comprising chitosan gel, MSCs, and BMP-2 effectively enhances bone formation in a rat calvarial CSD model.
• This injectable TEB approach holds potential for minimally-invasive bone repair strategies.
• The study confirms the viability and osteogenic contribution of MSCs within the engineered construct.