Evaluation of Autologous Bone Marrow Mesenchymal Stem Cell–Calcium Phosphate Ceramic Composite for Lumbar Fusion in Rhesus Monkey Interbody Fusion Model

Autologous bone marrow mesenchymal stem cell (BMSC)–calcium phosphate ceramic composites were constructed in vitro and implanted as a bone graft substitute for lumbar anterior interbody fusion in rhesus monkeys to determine the osteogenic capacity of the composites. Nine adult rhesus monkeys underwent lumbar L3–L4 and L5–L6 diskectomy and interbody fusion via an anterior retroperitoneal approach. Two fusion sites in each animal were randomly assigned to two of three treatments: autogenous tricortical iliac crest bone graft (autograft group), cell-free ceramic graft (ceramic group), or BMSC–ceramic composite graft (BMSC group). Autologous BMSCs were expanded in culture and stimulated with osteogenic supplement. The spinal fusion segments were evaluated by radiography, biomechanical testing, histologic analysis, and histomorphometric analysis 3 months postsurgery. The BMSC group achieved lumbar interbody fusion superior to that of the ceramic group, both biomechanically and histologically. The BMSC group and the autograft group showed equivalent biomechanical stiffness. Ceramic residues were significantly greater in the ceramic group versus the BMSC group. The results indicate that BMSC–ceramic composites can enhance bone regeneration and achieve osseous spinal fusion 3 months after implantation in the rhesus monkey interbody fusion model.