Bone Regeneration with Autologous Plasma, Bone Marrow Stromal Cells, and Porous β-Tricalcium Phosphate in Nonhuman Primates

To potentiate the bone formation capability of bone marrow stromal cell (BMSC)/beta-tricalcium phosphate (beta-TCP) constructs, we devised an autologous plasma-based construct. We tested its effectiveness and investigated the effects of its components on a monkey ectopic bone formation model. The autologous plasma (platelet-rich plasma, PRP, or platelet-poor plasma, PPP)/BMSC/beta-TCP construct (R group or P group) showed significantly more bone formation at 3 and 6 weeks after implantation than a conventional BMSC/beta-TCP construct using a culture medium (M group). There was no significant difference between the P and R groups. Moreover, the P group constructs with a 10-fold lower cell concentration yielded equivalent bone formation to the M group at 5 weeks after implantation. To elucidate the effect of fibrin and serum contained in the plasma, five constructs were prepared using the following cell vehicles: autologous serum + fibrinogen (0, 1, 4, or 16 mg/mL) or phosphate-buffered saline + fibrinogen (4 mg/mL). The serum + fibrinogen (4 mg/mL, physiological concentration of monkeys) construct showed the most abundant bone formation at 3 weeks after implantation, though at 5 weeks no statistical difference existed among the groups. Autologous plasma efficiently promoted osteogenesis of BMSCs/porous beta-TCP constructs, and both fibrin and serum proved to play significant roles in the mechanism.