Chondroinduction of human dermal fibroblasts by demineralized bone in three-dimensional culture

We designed and tested a three-dimensional device composed of demineralized bone powder (DBP) packed within a bilaminate sponge as an in vitro model for chondroinduction induced by DBP. Control bovine articular chondrocytes deposited cartilage matrix when cultured in these sponges. Human dermal fibroblasts that were seeded onto the composite sponge migrated through the collagen lattice and attached to the particles of DBP. Fibroblasts surrounding the DBP deposited a fine, granular extracellular matrix characterized by metachromatic staining similar to that deposited around the bona fide chondrocytes. Immunohistological analysis showed that the matrix contained chondroitin delta Di-4 sulfate, chondroitin delta Di-6 sulfate, and keratan sulfate epitopes. These components accumulated during the culture period, as quantified by immunochemical analysis of extracted matrix. In contrast, fibroblasts cultured in collagen sponges without DBP did not produce such a cartilage matrix. Control bovine chondrocytes produced these matrix molecules when cultured in the presence or absence of DBP. Thus this composite three-dimensional device facilitated evaluation of chondroinduction in human dermal fibroblasts in vitro.