Towards modulated feeding for the efficient and phenotypically controlled expansion of articular chondrocytes

Cell culture of chondrocytes, either in an experimental or industrial setting, typically rely on an invariant feeding strategy. The contribution of each component of the total expansion regime to the behaviour of the cells been expanded are not fully understood. It can be argued that to fully realise the potential of cell-based therapies, the exact contribution of the various expansion parameters to growth rate, metabolic behaviour and cell phenotype need to be intimately understood.

The studies in this thesis aim to better inform the nutritional aspects of future cell manufacturing strategy by; uncovering the contribution of critical culture parameters to growth rate and phenotype, understanding the relationship of any interactions that may exist between components and how these components may influence the culture as a function of time.

Results from the various studies demonstrated that an isolated subpopulation of chondrocytes can be sustained under serum-free conditions that promote SOX-9 transcript expression while returning growth rates similar to that found using serum-based medium. The contribution of the medium components, seed density and adhesion protein concentration to growth rate, metabolic behaviour and SOX-9,6 & 5 transcript expression were quantified using a statistically designed experiment. Two factors from the experiment, EGF and FGF-2, were taken forward and their effects on growth rate and gene expression as a function of time were investigated. The findings revealed that the exact timing of the introduction of the proteins into the culture medium had a marked impact on cell growth and gene expression.