3-DIMENSIONAL COMPOSITE OF DEMINERALIZED BONE POWDER AND COLLAGEN FORIN-VITRO ANALYSIS OF CHONDROINDUCTION OF HUMAN DERMAL FIBROBLASTS

Implantation of demineralized bone powder (DBP) in muscle or connectiv e tissue stimulates chondrogenesis followed by ectopic bone formation, in this way inducing the differentiation of endochondral bone. A new 3-dimensional in vitro composite sponge was designed to duplicate the packing density of in vivo DBP implants. The composite device, which c onsists of DBP packed between two layers of a porous collagen lattice, was used to assess the chondroblastic differentiation of human dermal fibroblasts. Important design considerations for this device were bio compatibility, rigidity and ability of cells to penetrate. In this stu dy, collagen concentration and source, irradiation, and lyophilization conditions were varied in fabrication. Human dermal fibroblasts were seeded onto the composite sponge, migrated through the collagen lattic e into the packet of DBP, and deposited a metachromatic extracellular matrix amongst the particles of DBP. In contrast, cells cultured in co llagen sponges or in composite sponges with inactivated guanidine-extr acted DBP did not secrete metachromatic matrix. This new in vitro syst em will be valuable in defining the mechanism of differentiation by os teoinductive materials and in evaluating the influence of other extrac ellular components and soluble factors on skeletal differentiation. (C ) 1996 Elsevier Science Limited.