The performance of a bone-derived scaffold material in the repair of critical bone defects in a rhesus monkey model

The efficacy and safety of a material derived from human bones in the repair of critical segmental bone defects are evaluated in a rhesus monkey model. Frozen human bones were chemically and physically processed into a partially demineralized and deproteinized material in blocks. The complete tissue-engineered (TE) bone was constructed of the material preseeded with allogeneic bone marrow mesenchymal stem cells (MSCs). The material alone and the TE bone were, respectively, implanted to bridge 2.5 cm-long critical defects in right and left radii of 15 monkeys. At weeks 1, 2, 3, 6 and 12 post-implantation, the grafts were collected from three animals and assessed for the local expression of osteogenic markers, histological and roentgenographic features, and immune reactions. It was shown that defects were well repaired with both treatments whereas the bone defects in 2 additional untreated animals remained the same size after 12 weeks. In radii implanted with the TE bones, the repair processes were approximately 3 weeks faster and new bones were formed in a multipoint way. There was neither observable toxic effect nor overt immune rejection in any animals. Taken together, these observations suggest that the TE bone blocks composited of the allogeneic or xenogeneic bone-derived scaffold and allogeneic MSCs may provide an ideal method for repairing large segmental bone defects.