Construction of artificial skin tissue with placode-like structures in well-defined patterns using dielectrophoresis
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During embryonic development of animal skin tissue, the skin cells form regular patterns of high cell density (placodes) where hair or feathers will be formed. These placodes are thought to be formed by the aggregation of dermal cells into condensates. The aggregation process is thought to be controlled by a reaction-diffusion mechanism of activator and inhibitor molecules, and involve mechanical forces between cells and cells with the matrix. In this project, placode formation in chicken embryonic skin cells was used as a model system for the study of the mechanism by which the placodes are formed. Artificial aggregates of chicken embryonic skin cells were created by suspending them in a 300 mM low conductivity sorbitol solution and attracting them by positive dielectrophoresis to high field regions within microelectrode arrays by applying a 10 - 20 Vpk-pk 1 MHz signal across the microelectrodes. It was demonstrated that using this method aggregates can be produced in a large variety of patterns and that the distance between the aggregates and aggregate size and shape within the pattern can be controlled effectively. Custom-built image analysis tools were developed in LabVIEW to analyze the patterns formed. The formation of aggregates by dielectrophoresis was followed by an immobilization phase of the resulting patterns inside a gel matrix, forming an artificial skin. Nutrients and oxygen were supplied externally. Long-term incubation of the artificial skin shows that embryonic skin cells in the aggregates were viable and showed behavior similar to that of developing embryonic skin, including further aggregation of the cells and the formation of cell condensates. The domain size was shown to have an influence on the condensation process, with cells in small aggregates forming only one condensate near the centre of the aggregate, and several condensates in larger aggregates. Whilst the distribution of cell condensates within the aggregates in round large aggregates is predominantly random, some line formation could be observed in linear aggregations, indicating some self-organization may be occurring.