In vitro reconstituted tissue as an alternative to human respiratory tract.

The data obtained from in vitro systems utilizing human cells and tissues should form a basic part of the information necessary for risk assessment. The most important thing for such systems is, therefore, to simulate the structures and functions of cells and tissues in the native organ as closely as possible. In designing in vitro systems, there may be two approaches-one aiming at the growth of cells in a primarily two-dimensional fashion, the other allowing cells to form in vivo-mimicking three-dimensional architectures. In cultures in which the airway epithelial cells are growing in a two-dimensional fashion, some functional and structural characteristics can be developed to a considerable extent. However, there are some that cannot be developed or expressed under that condition but require a three-dimensional growth pattern. In this paper we explore the capacity of early to long-term passage airway epithelial cells (human and hamster) to resume architectures and functions existing in the native tissue in the specific environments given in vitro.