Survival of Osteocompetent Marrow Cells in Vitro and the Effect of PHA-Stimulation on Osteoinduction in Composite Bone Grafts

Abstract

The osteoinductive capacities of bone-marrow autografts, washed marrow-free bone allografts, and composite grafts of washed allogeneic bone impregnated with viable or killed autologous marrow cells have been compared in a heterotopic site in rabbits. Composite grafts (similar to 40 mg allogeneic bone) with viable marrow performed equally well as autografts, providing that these implants contained at least 50,000 marrow cells. Composite grafts with dead marrow were noninductive, and grafts with 10,000 viable marrow cells produced much less new bone than grafts with 50,000 cells. Postoperative treatment of host rabbits with PHA-P increased the osteoinductive capacity of composite grafts with initially subcritical numbers of marrow cells to control levels. These results indicate that the osteoinductive cells in composite grafts are mobilized from the marrow elements rather than from the undifferentiated cells in the host bed.