As I mentioned yesterday, I am going to take a moment to make the case against reducing scientific research to the in vitro is invalid– in vivo is valid binary. I feel like the biggest issue with this is that it significantly limits our understanding of how research is being done and how to evaluate it. I also think that hanging on to old-fashioned ideas about in vitro studies perpetuates the unnecessary use of animals in studies. So I want to take some time to break that up a bit.
There is a lot more to be determined than whether we are looking at a human clinical trial or a petri dish experiment using a cell line purchased from a biotech lab. Furthermore, there is no reason to discount that in vitro research out-of-hand. If we want to evaluate the efficacy of a study we need to look at the design of the experiment which I will tackle later in the week. Before I dive into the methodology. I should probably explain a few basic terms in the context of biological research.
Medium– a substance that various cultures are grown in. The most commonly used mediums are probably nutrient broths and agar.
Bacterial culture – this type of culture involves growing a microbial colony in lab equipment for experimentation. Biofilm models (single or mixed-species) can be cultured in the lab, also. They are useful in determining the effect that the biofilms have on host tissue or the effects that an agent might have on a biofilm, but it has been a tedious process. The following journal article breaks down that history, a little:
Lebeaux, David, Ashwini Chauhan, Olaya Rendueles, and Christophe Beloin. “From in Vitro to in Vivo Models of Bacterial Biofilm-Related Infections.” Pathogens 2, no. 2 (May 13, 2013): 288–356.
Cell cultures– a cell culture is made by removing a cell from its original environment and incubating it in favorable medium (often agar) in lab equipment. Additives are needed for the growth of the culture. For example, viruses need living host cells to live. Animal cells need some type of blood serum which contains growth factors and hormones they would be receiving through perfusion in the body.
Sometimes these cells are modified in some way and stored cell repositories in the form of cell lines or “immortalized” cells to be distributed for future research. That’s why sometimes you will see the authors mention the biobank where they got their material. Here you can read about the biobank founded by one of the pioneers in this field- The Coriell Institute.
Researchers are also able to culture tissue and organs. This is an interesting article that explains some of the history of that process. Use of human tissue explants to study human infectious agents. Not too long ago researchers were able to culture a new windpipe for a man using his own cells.
Now let’s investigate the different types of research methodology you will run across in research studies. I have them listed in the order they are often considered to be most reliable, but keep in mind there are reasons researchers choose a particular methodology and they are all necessary, and useful, components of scientific research.
In Vivo Experiments
In Vivo experiments are those experiments done on a living organism. They generally take the form of animal studies in labs or human clinical trials. Microbiologists (who are doing many of the studies herbal researchers use) may call an experiment done on isolated cells in vivo as long as they are living and haven’t been modified- for example they might use cultured cells from a biopsy. This is more accurately described as an ex vivo experiment, but not all researchers use the same terminology. So you have to read the fine print-not just the abstract.
In Situ Experiments
Sometimes you might see the term in situ used instead of in vivo. In Situ experiments are performed in exactly the place which the issue being investigated occurs without any sort of interference from the researchers. An in situ experiment might take the form of examining cells or tissues of a functioning organ with blood is being delivered (perfusion) or examining a plant while growing in its natural environment, as opposed to bringing it into the lab. I think they are quite relevant to studying plants as it has been proven conclusively that plants grown in the wild produce more secondary metabolites than lab plants.
Ex Vivo Experiments
These are experiments that work with cells or tissue from an organism in an external environment but do not alter the cells or tissue, as opposed to in vitro tests which might manipulate the cells to immortalize them, or for some other reason. You can read more about the differences here, if you are interested.
An ex vivo project allows researchers to do things they couldn’t ethically do, otherwise. Working with cultured tissues and organs is one of the answers to reducing the use of animals in scientific research.
In Vitro Experiments
In vitro studies are experiments are carried out using microorganisms, cells or biological molecules which have in some way been disrupted. The individual parts are tested or analyzed outside their normal biological environment-generally in some sort of glass lab equipment.
One of the most amazing in vitro advances in recent years is the discovery of induced pluripotent cells. Researchers managed to re-program skin cells into a cell with stem cell like capabilities that could then be used to generate any cell in the body-even diseased ones. So what you end up with in the dish is a specific model of a disease. This technology is eliminating the need for in vivo research which involved infecting animals with diseases.
Also experiments done on whole, living organisms which have been cloned and never left a lab are sometimes still referred to as in vitro because the subject has been scientifically tampered with. Again this is specific to herbalists because it happens a lot with plants.
In vitro experiments are often dismissed with the caveat that how something works in a petri dish, is not how it works in the human body. This can absolutely be true at times, but is not always necessarily the case. In vitro technology is being refined and improved all the time. This method can absolutely be relevant when looking at an agent’s efficacy. They have also used cultures to replace some of the more obnoxious animal tests like the Draize eye irritancy test.
In Silico Experiments
These experiments are conducted by using computer models for research. You will sometimes see them referred to as lab-on-a-chip technologies. They are already using these computer models to replace primates used for brain research.
I have very strong concerns about using animals for research and think that every measure should be used to “restrict, refine and replace.” This is one of the reasons, I feel so strongly about helping people to understanding the validity of ex vivo and in vitro research, is that as long as we are spreading the misconception that this research is always less valid than in vivo research we will never end animal experimentation.
This idea that in vitro research is not valid has been amplified by people defending the use of animals in scientific research. In 2011, Norvo Nordisk proved that using cell cultures in their quality control process was as effective as animal tests, in order to eliminate animal testing in their facility. The ridiculous part is that it took them over a decade to do so convincingly- not because the testing wasn’t accurate but because of the deeply entrenched thinking on in vitro methodology.
On the other hand, it is absolutely not true that animal research is never applicable to humans, and can be eliminated entirely-not yet. Due to the chronic disease epidemic and the advances in epigenetics, we need to be able to track these illnesses through multiple generations. Mice share 98% of their DNA with humans. For example, the two human tachykinin genes TAC1 and TAC3 correspond to Tac1 and Tac2 genes in mice. They also have relatively short life spans. It was new technology enabling researchers to use mice in genetic research that stopped the decline in animal research in the 80’s.
References:  Yong, Ed. “Will We Ever... Grow Synthetic Organs in the Lab?” Future. Accessed April 12, 2016. http://www.bbc.com/future/story/20120223-will-we-ever-create-organs.  “Human Tissue for in Vitro Research as an Alternative to Animal Experiments: A Charitable ‘Honest Broker’ Model to Fulfil Ethical and Legal Regulations and to Protect Research Participants.” Alternatives to Laboratory Animals. Accessed June 21, 2016. http://www.atla.org.uk/human-tissue-for-in-vitro-research-as-an-alternative-to-animal-experiments-a-charitable-honest-broker-model-to-fulfil-ethical-and-legal-regulations-and-to-protect-research-participa/  Doke, Sonali K., and Shashikant C. Dhawale. “Alternatives to Animal Testing: A Review.” Saudi Pharmaceutical Journal 23, no. 3 (July 2015): 223–29.  National Academy of Sciences. Guide for the Care and Use of Laboratory Animals. Washington, D.C.: National Academies Press, 1996. http://www.nap.edu/catalog/5140.  Preedy, Victor R., ed. Neuropathology of Drug Addictions and Substance Misuse Volume 1: Foundations of Understanding, Tobacco, Alcohol, Cannabinoids and Opioids. London, UK: Academic Press, 2016. p. 190