Repair of goat tibial defects with bone marrow stromal cells and beta-tricalcium phosphate

Tissue engineering techniques have been proven effective in bone regeneration and repairing load-bearing bone defects. Previous studies, however, have heretofore been limited to the use of slowdegradable or natural biomaterials as scaffolds. There are, however, no reports on using biodegradable, synthetic beta-tricalcium phosphate (beta-TCP) as scaffolds to repair weight-bearing bone defects in large animals. In the present study, highly porous beta-TCP scaffolds prepared by the polymeric sponge method were used to repair goat tibial defects. Fifteen goats were randomly assigned to one of three groups, and a 26 mm-long defect at the middle part of the right tibia in each goat was created. In Group A (six goats), a porous beta-TCP ceramic cylinder that had been loaded with osteogenically induced autologous bone marrow stromal cells (BMSCs) was implanted in the defect of each animal. In Group B (six goats), the same beta-TCP ceramic cylinder without any cells loaded was placed in the defect. In Group C (three goats), the defect was left untreated. In Group A, bony union can be observed by gross view, X-ray and micro-computed tomography (Micro-CT) detection, and histological observation at 32 weeks post-implantation. The implanted beta-TCP scaffolds were almost completely replaced by tissue-engineered bone. Bone mineral density in the repaired area of Group A was significantly higher (p < 0.05) than that of Group B, in which scant new bone was formed in each defect and the beta-TCP hadn't been completely resorbed at 32 weeks. Moreover, the tissue-engineered bone of Group A had similar biomechanical properties as that of the normal left tibia in terms of bending strength and Young's modulus (p > 0.05). In Group C, little or no new bone was formed, and non-union occurred, showing that the 26 mm segmental defect of the goat tibia was critical sized at 32 weeks. Thus, it can be concluded that the mechanical properties of the BMSCs/beta-TCP composites could be much improved via tissue engineering approach and beta-TCP might be used to repair the weight-bearing segmental defects of goat tibias.