The effect of devitalized trabecular bone on the formation of osteochondral tissue-engineered constructs

In the current study, evidence is presented demonstrating that devitalized trabecular bone has an inhibitory effect on in vitro chondral tissue development when used as a base material for the tissue-engineering of osteochondral constructs for cartilage repair. Chondrocyte-seeded agarose hydrogel constructs were cultured alone or attached to an underlying bony base in a chemically defined medium formulation that has been shown to yield engineered cartilaginous tissue with native Young's modulus (E(Y)) and glycosaminoglycan (GAG) content. By day 42 in culture the incorporation of a bony base significantly reduced these properties (E(Y)=87+/-12 kPa, GAG=1.9+/-0.8%ww) compared to the gel-alone group (E(Y)=642+/-97 kPa, GAG=4.6+/-1.4%ww). Similarly, the mechanical and biochemical properties of chondrocyte-seeded agarose constructs were inhibited when co-cultured adjacent to bone (unattached), suggesting that soluble factors rather than direct cell-bone interactions mediate the chondro-inhibitory bone effects. Altering the method of bone preparation, including demineralization, or the timing of bone introduction in co-culture did not ameliorate the effects. In contrast, osteochondral constructs with native cartilage properties (E(Y)=730+/-65 kPa, GAG=5.2+/-0.9%ww) were achieved when a porous tantalum metal base material was adopted instead of bone. This work suggests that devitalized bone may not be a suitable substrate for long-term cultivation of osteochondral grafts.