Three dimensional tissue and organ models in vitro: their application in basic and practical research

Good and reliable three dimensional biomodel in vitro should mimic the in vivo structure and function of investigated tissue or organ. This can be achieved through the interaction of various cell types and the environment (extracellular matrix, as well as spatial cell contacts). While designing such a model it is necessary to find best nutritive and adhesive factors, to allow access to components of optimal matrix and to enable cell contacts in three dimensions. The response and function of such models reminds physiological function of tissue of origin. Over several years there has been an increasing number of experiments and publications reporting research involving spatial cell models. This model and its structural and molecular analysis clearly showed, that in comparison with conventional cultures, mainly monocultures grown as monolayers, spatial cultures resemble the in vivo situation with regard to cell shape and biological behaviour. Spatial arrangement of cells and the environment can direct tissue differentiation. Interesting example of the importance of the environment for the latter, is the finding that the ectopic implantation of embryonic cells transforms them into malignant tissue while the same cells located in the uterus undergo normal embryogenesis. The present review describes several three-dimensional models in vitro and their application in basic and practical studies. It is especially interesting and important in the light of developments of tissue modeling to obtain in vitro substitutes of damaged or impaired tissues and organs. Other demands come from animal protectionists who suggest replacement of experimental animals with cultures and tissue models in bio-, pharmacological, and toxicological assays. In response, European Union legislation introduces increasing restrictions on animal experiments. At last, researchers seek in vitro models which would enable avoiding discrepancies between in vitro and in vivo results.