The effects of cross-linking of collagen-glycosaminoglycan scaffolds on compressive stiffness, chondrocyte-mediated contraction, proliferation and biosynthesis

The healing of articular cartilage defects may be improved by the use of im plantable three-dimensional matrices. The present study investigated the ef fects of four cross-linking methods on the compressive stiffness of collage n-glycosaminoglycan (CG) matrices and the interaction between adult canine articular chondrocytes and the matrix: dehydrothermal treatment (DHT), ultr aviolet irradiation (UV), glutaraldehyde treatment (GTA), and 1-ethyl-3-(3- dimethylaminopropyl) carbodiimide (EDAC). The degree and kinetics of chondr ocyte-mediated contraction, chondrocyte proliferation, and protein and glyc osaminoglycan synthesis were evaluated over a four-week period in vitro. Ce ll-mediated contraction of the matrices varied with cross-linking: the most compliant DHT and UV matrices contracted the most (60% reduction in matrix diameter) and stiffest EDAC. matrices contracted the least (30% reduction in matrix diameter). All cross-linking protocols permitted cell proliferati on and matrix synthesis as measured by DNA content and radiolabeled sulfate and proline incorporation, respectively. During the first week in culture, a lower level of proliferation was seen in the GTA matrices but over the f our-week culture period, the GTA and EDAC matrices provided for the greates t cell proliferation. On day 2, there was a significantly lower rate of H-3 -proline incorporation in the GTA matrices (p < 0.003) although at later ti me points, the EDAC and GTA matrices exhibited the highest levels of matrix synthesis. With regard to cartilage-specific matrix molecule synthesis, im munohistochemistry revealed a greater amount of type H collagen in DHT and UV matrices at the early time points. These findings serve as a foundation for future studies of tissue engineering of articular cartilage and the ass ociation of chondrocyte contraction and the processes of mitosis and biosyn thesis. (C) 2001 Elsevier Science Ltd. All rights reserved.