In vitro studies are those performed in tubes or dishes with cultures of cells or their components. As in vitro techniques have improved, the volume of cell culture experiments in the literature has expanded rapidly. In vitro studies are useful because they are relatively inexpensive and allow simplification of complex systems that can be studied in relative isolation. However, this simplicity and disconnectedness detracts somewhat from the usefulness of the work regarding extrapolative understanding. For while in vitro studies provide useful data, they fall short of providing the bigger picture because they cannot possibly replicate the intricate complexity of the cellular system in the organism as a whole. Therefore the data from in vitro work should never be extrapolated verbatim to complex in vivo physiology. Despite this flaw, in vitro data is often used out of context either deliberately or by accident in the public and academic arena, because conclusions drawn from such work often belie the actual data collected from the experiments.
A great example of the misinterpretation of in vitro work was that made by Dan Duchaine of Body Opus fame (here). Duchaine incorrectly believed that chrysin, which he called flavone X, would be a useful in vivo anti-oestrogen. His theory was based on cell culture work that at the time showed an anti-oestrogenic effect of chrysin in its aglycone form. However, this data was limited in its scope because it did not accurately reflect the complexity of the whole organism. Chrysin is extensively metabolised in the enterocytes of the gut, resulting in the absorption of mainly phase II conjugates. It is these conjugates that interact with cells and tissues and have physiological effects. Therefore the anti-oestrogenic effects of high concentrations of chrysin in cell culture experiments in not relevant to the form of chrysin present in plasma, incidentally, also at much lower concentrations. Although Duchaine can be forgiven for this mistake as he himself acknowledged the failure, we should be less forgiving of professional scientists who make the same mistakes.
RdB
