AGING EFFECT ON INDUCTIVE CAPACITY OF HUMAN DEMINERALIZED BONE-MATRIX

Demineralized bone powder (DSP) prepared from human cortical bone was implanted into subcutaneous pouches of athymic Nu/Nu mice for 28 days. The osteoinductive capacity was evaluated by histomorphometry of the induced cartilage and bone, and by alkaline phosphatase activity in th e implant. Very small amounts of new bone and cartilage were found at histological analysis, confirming that human DBP is much less osteoind uctive than that from other species. Whereas the morphometric data of the implants from the young and aged donors were not significantly dif ferent, the alkaline phosphatase activity was significantly lower in t he implants from the old donors than from the younger ones. This diffe rence between the morphometric and biochemical results could reflect t he fact that the enzymatic activity is already present in the osteopro genitor cells. At 28 days, the osteoblastic activity in contact with D BP from the aged group is characterized by a decrease in the enzymatic amount which is not yet visible at the tissue level. This tendency to a decrease in the osteoinductive capacity of bone matrix is an additi onal aspect of the age-related alterations which occur in bone tissue and could be attributed to modifications of different proteins of the bone matrix, including bone morphogenetic protein.