Experimental Study on Reconstruction of Segmental Mandible Defects Using Tissue Engineered Bone Combined Bone Marrow Stromal Cells With Three-Dimensional Tricalcium Phosphate

Abstract

Reconstructive procedures of segmental mandible defects often require bone graft harvesting, which results in donor site morbidity; the use of tissue-engineered bone might mitigate this problem. The aim of the present experimental pilot study was to produce three-dimensional (3D) autologous tissue-engineered constructs that combine autogenous cultivated bone marrow stromal cells with beta-tricalcium phosphate to reconstruct segmental mandible defects without donor site morbidity. Bone marrow stromal cells were isolated from a dog's caput femoris. After differentiation and proliferation in vitro, the cells were seeded into a 3D beta-tricalcium phosphate scaffold. The constructs were incubated under osteogenic culture conditions for 5 days. Segmental defects of 30 mm length were created unilaterally in the mandibles of the animals. Reconstruction was performed using the construct in three dogs and the scaffold only in three dogs as a control group. The specimens were retrieved 3 months later, and the reconstructed areas were processed for gross observation, radiographic examination, 3D computed tomographic (CT) imaging, biomechanical evaluations, and histologic observation. The construct implanted group (n = 3) showed an average height of the reconstructed area of 18.54 mm and the control group 9.16 mm (P < 0.05). Higher radiodensity was present in the construct group than in the control group, as shown by radiograph. 3D CT imaging showed nearly two-thirds absorption of the reconstructed area in the control group. The biomechanical examination of the construct and control groups showed a compression strength of 102.77 N and 42.90 N and stress of 3.504 N/mm and 1.930 N/mm, which demonstrates significant difference. Histologic micrographs showed new bone formation in the scaffolds in central sections of the defects in the construct group 3 months later, with osteoblast seams, osteoclastic resorption, and cartilage formation. The construct of morphologic, 3D beta-tricalcium phosphate scaffold seeded, autologous bone marrow stromal cells ensure bone formation and vascularization throughout the procedure of mandible segmental defect reconstruction, closely resembling how tissue engineering would be used to reconstruct a segmental mandible defect in the clinical setting.