Food for thought... on cell culture.

Cell culture technologies form the basis of most alternative methods. They have matured over the last decades, but severe limitations remain, which – to say it positively – leave room for improvement. This second article of the Food for Thought series wants to raise awareness of current limitations that impact on the predictive value of test systems based on cell cultures. The critical question is, how well the cell in culture reflects the cell in the organism, especially with regard to its state of differentiation and its response patterns in isolation in an artificial environment. Differentiation can be seen as the cellular equivalent of the phenotype at the level of an organism: Which genes are expressed at a given time point and which functionality do they allow? This critical appraisal of the problems of current cell culture techniques does not mean that in vitro systems are not useful, but stresses the need to critically evaluate the predictive value of these models in each and every case. This emphasises the need for validation, either in a formal sense for standardised tests or as a quality assurance process for the in vitro models in research and cellbased screening approaches.