Methods for cultivation of keratinocytes with an air-liquid interface

In ordinary cultures, cells are grown on artificial substrates and immersed in culture medium. In vivo, interfollicular epidermal cells grow on the basement membrane and are exposed to air. In a first effort to render the culture of these cells more physiological it seems legitimate to raise the cultured cells to the air-medium interface. Epidermal cells can be raised by the use of collagen gels maintained on a rigid support. They can also be grown on nitrocellulose filters coated with collagen or coated with a basement-membrane equivalent (BME) previously deposited by bovine corneal endothelial cells. By raising the cultures to the air-medium interface there is some evidence of a more complete differentiation, as evaluated by morphologic criteria. However, biochemically, the raising of the cultures does not seem to induce the synthesis of those keratin polypeptides which are not expressed in immersed cultures. Epidermal cells can also be raised by culturing them on dermal substrates or dermal equivalents. When they were cultured on inverted dead pig skin, epidermal cells synthesized membrane-coating granules (MCG). MCG were not found in immersed controls. By culturing epidermal-cell suspensions on dead deepidermized dermis (DED), all morphologic markers of differentiation were seen except the keratin pattern. In addition, partial reexpression of high-molecular-weight keratin polypeptides occurred. However, the complete expression of keratins by cultured cells depends on the filtering action of the dermal substrate (the cultures are fed from underneath) more than on exposure to the air-liquid interface. In summary, several methods are available to culture epidermal cells at the air-liquid interface that are of interest in an investigation of the response of these cells to epigenetic influences.