| This study demonstrates that the phenotype of zonal articular chondrocytes can be dramatically affected by monolayer passaging, three-dimensional culture, substrate modification, and growth factor stimulation. Retention of the chondrocytic phenotype is important for tissue engineering applications and cell transplantation procedures in which large numbers of cells are required. Defining a culture environment that is conducive to chondrocytic growth and development could help promote the formation of a functional tissue in a short amount of time. This work focuses on the phenotypic changes that occur in zonal chondrocytes cultured in vitro. Initial differences in gene expression are found to exist between superficial and growth zone articular chondrocytes. Results indicate that monolayer expansion of these cells causes a rapid loss in chondrocytic phenotype, especially for zone-related genes. By using novel growth environments, this work shows that there is a possibility for retaining the phenotype of cultured cells. In particular, dedifferentiated zonal chondrocytes seeded onto aggrecan-coated polystyrene show a limited ability to re-express the chondrocytic phenotype in monolayer. The presence of growth factors can also stimulate matrix synthesis and improve gene expression. This work shows that significant changes occur under a variety of treatments, but in general, biosynthesis is localized to growth zone chondrocytes. As shown throughout the combined studies, the zonal populations respond differently to stimuli, a finding that requires consideration when replicating the native organization of articular cartilage. |
