What is the difference between Ex vivo and In vitro?

I know this train of thought is 4 years old, with 18673 reads as of immediately ( indicating that this question is of wide interest ). I besides suspect that Naveen ( who posted the original question ) may well have graduated by now, and moved on to possibly much bigger questions. While I read through the responses above, I realized two things ( blue, no offense to anyone ) : ( 1 ) the responses did not realize the depth of this question, and quite obviously reflect the definitions widely available by ‘googling ‘, and ( 2 ) even guidelines from eminent regulative organizations like FDA fail to realize the astuteness of this question. I shall provide examples for why I am making these two statements. And I ask for a fiddling unplayful thought here ( I have no clear suffice to this wonder ; see below ). As a retread : studying the effects of a drug on an animal when the whole animal is administered, is an case of “ in vivo ” study. Study of that drug on an isolate weave of the animal, when the weave is taken out and treated outside the animal ‘s body, is “ ex-husband vivo ”. Study of the lapp drug on cells derived from that animal, but cultured and treated in artificial medium, is “ in vitro ”. so far, fine. The complication comes when you come across hundreds of research articles, even in top CNS ( Cell-Nature-Science ) -type journals, where cell culture experiments are referred to as both “ in vitro ”, and sometimes, “ in vivo ”. In practical writing of a research article, I think it is the context that dictates what terms should be used, and when. Let me give an model below.

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Cell culture-based experiments have defined critical events that lead to recognition of origin sequences for eukaryotic DNA replication, fabrication of multiple multi-protein complexes and recruitment of many accessory factors and enzymatic activities in distinct orders, which ultimately culminates in DNA echo initiation. We call these studies “ in vitro ”, as these events were dissected “ inside the civilized cells ”. article Regulated Eukaryotic DNA Replication Origin Firing with Puri… immediately, take the fabulously brilliant work from John Diffley ‘s lab reported in Nature ( ) where they could orchestrate forum and firing of rejoinder complexes “ ALL IN TEST TUBES ” from INDIVIDUAL PURIFIED COMPONENTS. What would you call that ? “ In vitro ”, decidedly ; correct ? historically, cell-free experiments are normally referred to as “ in vitro ” ( based on semantics, Diffley ‘s work would be called “ in vitro ” ; and he calls his experiments “ in vitro ” ). nowadays, that approach path did not involve in-cell studies, but was an absolutely cell-free study. If we do so, we would not be able to distinguish his work from all the cell-based works on DNA echo that have been carried out. right ? therefore, we need to distinguish “ cell-based in vitro ” from “ cell-free in vitro ”. Right ? now, how to do sol ? Imagine a situation where Diffley finds an exciting leave in his in vitro ( cell-free ) experiments, and validates those results in in-cell ( distillery “ in vitro ” ) experiments, and writes an article. Should he call both sets of experiments “ in vitro ” ? Or, should he adopt distinct terms, like “ cell-free ” for non-cell experiments based on cell-derived extracts and purify components, and “ in vitro ” for the “ in-cell ” experiments ? If so, then he will use both terms “ cell-free ” and “ in vitro ” in the same article with ‘mutually exclusive ‘ meanings. This will come in contrast with the historical exercise of exchangeable usage of these terms to mean the same thing. Things get a bite more complicated when we follow the works such as those by Nobel laureate Jack Szostak. His group would not even use purify DNA/proteins prepared from extracts derived from cells, as Diffley did. They would synthesize membrane-like polymers and other chemicals to retrace how a primitive environment may have created “ basic functional entities ” of life, closely 4 billion years ago. His approach, nowadays we see, are even a big outdistance away from Diffley ‘s cell-free “ in vitro ” apparatus. What do we call that ?

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I do not have answers. But I do not think we can dismissively and promptly demarcate what is in vivo, what is in vitro, and what is not. For scientists like Roger Kornberg, who studied cell-free “ in vitro ” mechanisms of arrangement, a cell-based experiment would be sincerely “ in vivo ”. In turn, animal-based experimentalists would laugh at cell-based scientists, saying cells do not qualify to be called in vivo, and animals do ! thus, do we bring “ context ” into it, and call anything “ in vitro ”, “ in vivo ” etc as the position fits ? Or, should we adopt clear up, unequivocal, distinct terms for discrete experimental approaches ? Sorry Naveen, I do n’t think we have clear answer to your doubt however. I shall appreciate “ thoughts ” on this motion ( but, may I request no more copy-paste responses, please ? ).

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