Cell-based bonding of articular cartilage : an extended study

This study evaluated the biomechanical characteristics of newly formed cartilaginous tissue synthesized from isolated chondrocytes and seeded onto devitalized cartilage in an extended study in vivo. Cartilage from porcine articular joints was cut into regular discs and devitalized by multiple freeze-thaw cycles. Articular chondrocytes were enzymatically isolated and incubated in suspension culture in the presence of devitalized cartilage discs for 21 days. This procedure allowed the isolated chondrocytes to adhere to the devitalized matrix surfaces. Chondrocyte-matrix constructs were assembled with fibrin glue and implanted in dorsal subcutaneous pockets in nude mice for up to 8 months. Histological evaluation and biomechanical testing were performed to quantify the integration of cartilage pieces and the mechanical properties of the constructs over time. Histological analysis indicated that chondrocytes grown on devitalized cartilage discs produced new matrix that bonded and integrated individual cartilage elements with mechanically functional tissue. Biomechanical testing demonstrated a time dependent increase in tensile strength, failure strain, failure energy, and tensile modulus to values 5-30% of normal articular cartilage by 8 months in vivo. The values recorded at 4 months were not statistically different from those collected at the latest time point, indicating that the limits of the biomechanical property values were reached after four months from implantation.