In vitro means cells or tissue studied outside a living organism. It allows precise control and direct observation of what a substance does to a cell, and removes everything a body would otherwise do to the substance first.
In vitro means cells or tissue studied outside a living organism. It allows precise control and direct observation of what a substance does to a cell, and removes everything a body would otherwise do to the substance first.
A compound applied directly to cells has bypassed digestion, the liver and distribution through the bloodstream. A substance that acts powerfully in a dish may never reach the relevant tissue in a person at any realistic dose, which is one of the most common reasons results do not translate.
Dish experiments frequently use concentrations far above anything achievable in a living body. The effect is real at that concentration and says little about effects at concentrations a body could produce.
Isolated cells have no immune response, no excretion and no feedback from other organs. Effects that a body would counteract, amplify or clear appear in a dish as straightforward consequences.
That a mechanism is possible. If a substance cannot affect a cell directly, a whole-organism effect by that route is unlikely, so negative in vitro results constrain the hypothesis usefully.
Many experiments use immortalised cell lines that have been dividing in culture for decades and differ from the tissue they came from. Primary cells are closer and harder to work with, and papers state which they used.
In vitro work is faster and cheaper than anything else, so there is more of it, so there is nearly always a dish study supporting any claim. Abundance is not weight, and a claim resting only on in vitro findings is resting on the lightest available layer.
What concentration, which cells, and whether anything beyond a dish has tested the same hypothesis. If the answer to the third is nothing in twenty years, that is the finding.
Dish experiments frequently use concentrations far above anything a body could produce. The effect is real at that concentration and says little about effects at achievable ones.
If a substance cannot affect a cell directly, an effect by that route in a whole organism is unlikely. In vitro work is therefore stronger evidence against a mechanism than for one.
The claims on this page about cells in isolation answer a narrower question than their results are used for can be checked against sources outside this site: