What is the difference between in vitro and in vivo medical studies, and what is the definition of each of these types of clinical trials?. Learn more about the term in vitro as used in health and biology and how in vitro studies play a role in STD research. In vitro (meaning: in the glass) studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially.
in vitro Studies
These assays are of growing importance for risk assessment because they measure events that could lead to delayed or latent adverse health effects. Annex provides an expanded description of genetic toxicology information, and Annex describes several specific types of validated genetic toxicity tests. The current challenge is to demonstrate a connection between changes in specific genes or combinations of genes and the underlying mechanism responsible for a given disease.
New technology that may eventually aid in assessing risk of toxicity of compounds, including dietary supplement ingredients, is described in Annex The previous paragraphs organized in vitro assays by the effects assessed: These and other in vitro tests may be conducted in a variety of experimental systems, such as isolated tissues or in isolated cells, each of which has its own considerations. In some experiments, animal tissues are isolated and then treated with test substances e.
Tissues in many ways resemble an intact in vivo system because they contain a variety of cell types organized in their native structure and, because they are usually recently isolated from an animal, the protein expression is relatively similar to that in vivo.
Detrimental effects observed in tissue or isolated organ assays may be predictive of effects in vivo. Nevertheless, the toxicological value of these effects can be limited by the inability of an isolated tissue to react with other reciprocating organ-body systems. For example, there are limitations inherent in excluding the gastrointestinal system in an experiment using isolated tissue.
Botanical extracts provide an example of how important it is to consider how absorption of the ingested substance may affect which compounds reach the target tissue. Botanical extracts often contain polyphenolic compounds e. When administered orally to humans, however, these compounds may bind to food components or gastrointestinal cells, or they can be metabolized by gastrointestinal mucosal or bacteria enzymes and therefore not exert the same effects in vivo as seen in isolated tissue Bravo, ; Yang et al.
In summary, if the impact of excluding effects of other organ systems is considered or compensated for, isolated tissue can be a valuable tool for studying physiological effects of dietary supplement ingredients. Suspensions of isolated cells or cultures of cells derived from animal tissue or from continuously replicating cell lines offer numerous advantages for studying chemical toxicity.
The test substance can be examined in direct contact with the cell type of interest, the concentration of the test substance can be rigorously controlled, and the secondary effects of such extracellular influences as metabolic factors, matrix, and cell-to-cell contact can be excluded or controlled for.
However, substances that are insoluble in culture media may not adequately reach the target cell in vitro , leading to misleading negative results. In addition, adaptation of cells to culture generally results in spontaneous alterations of gene expression so that caution must be exercised in extrapolating to whole organisms the results of chemical effects in culture.
It is also important that the appropriate cell model is used. All cell types do not respond similarly to a single substance, even when the cells originate from the same organ. One cell type may exclude or excrete a compound, whereas another cell will not, and another may behave differently due to its unique biochemical pathways.
Cell lines may have different activities than the parent tissue. For example, a problematic interpretation can be made using certain hepatocyte cultures that, unlike the liver, do not always support expression of metabolizing enzymes, causing some data generated in these assays to be misleading.
A better choice for some tests might be cell cultures established specifically to evaluate metabolism of substances. In vitro studies vary in their value as predictors of harm. An in vitro assay will have the most direct predictive value when the measured effects. It may often be appropriate to use in vitro data as hypothesis generators, as potential indicators of harmful health effects, or as information about biological plausibility or mechanism, rather than as standalone demonstrated indicators that in themselves indicate risk.
However, some types of in vitro assays should be considered validated as predictors of possible harm, and thus when carefully conducted and interpreted, will provide valuable information beyond simply reinforcing observations from other categories of data or generating hypotheses.
In vitro assays warrant attention and are appropriate to use as standalone indicators of risk to human health when the relationship between the results of an in vitro assay and actual clinical or animal outcomes has been demonstrated, thus validating the predictive value of the assay. A number of validated in vitro tests are in standard use for regulated materials and are often required for premarket approval by a regulatory authority. These form an important established battery of tests that are useful in predicting possible adverse effects.
Although the regulatory situation is such that completion of these or other in vitro tests is not required for dietary supplement ingredients, the scientific value of these assays in predicting adverse effects in humans is as valuable in assessing the safety of dietary supplements as it is in assessing the safety of other substances.
For example, specific types of in vitro tests are used by the Environmental Protection Agency EPA and the Food and Drug Administration FDA to identify potential pesticides and food additives that may lead to adverse effects see Annex Assays used by regulatory bodies are by no means the only assays or in vitro observations that should be considered as validated and thus independent predictors of risk.
Other specific assays, such as certain receptors or ion channel assays, should also be considered validated. The important concept is that for an assay to stand alone as a predictor of risk, a connection between the observed biological effect and an adverse effect needs to have been made. In Chapter 10 , this concept is illustrated by the need for linkages between observed biological effects and adverse health effects.
In addition to the types of in vitro effects considered validated, other in vitro information is also valuable for assessing biological plausibility of concerns raised by other observations, such as observations of adverse. The assessment of biological plausibility becomes an issue when interpreting data and trying to predict the likelihood of causal relationships see Chapter While it is not necessary to establish a rational mechanism of harm to conclude that an ingredient poses an unreasonable risk, it is nonetheless valuable to identify possible mechanisms that explain the totality of the data.
Many in vitro studies can be useful for this purpose. In addition to considering the correlation of the particular in vitro assay with a particular adverse health outcome, it is of utmost importance to consider the seriousness of the outcome when evaluating the level of concern warranted by results of in vitro studies. This concept is analogous to Table , which categorizes the relative seriousness of various types of effects observed in animals.
There is no quantitative method of assigning a weight to the outcome of each in vitro experiment and imputing an appropriate level of concern for public health risk from such data. Instead, it is important for experts to reach a judgment about the in vitro results based on the seriousness of the effect predicted, the validity of the assay in identifying substances that cause a particular adverse effect, the quality of the individual studies, and the consistency among the collection of studies.
Considerations on study quality discussed in the human and the animal chapters Chapters 4 and 5 apply to in vitro systems as well. Considerations include the strength of the association, its reproducibility in the same and corresponding systems, the specificity of the findings for both cause and effect, and the coherence of the evidence—all of which give more confidence that the findings are meaningful.
When considering the information, it will be helpful to answer the following questions to decide how much concern for public health is warranted by the in vitro evidence:. Is the in vitro test validated or commonly used to predict a serious adverse effect? For example, assays used in regulatory situations to predict possible carcinogenic effects are considered as such.
How serious is the adverse effect that might be predicted? Mutagenicity in many assays, DNA damage in human cells, cell transformation, and production of DNA adducts in vitro are evidence of higher levels of concern, especially for potential carcinogenesis. Evidence of enzyme induction without DNA damage or mutagenesis is of lesser concern. Does the evidence provide mechanistic or mode of action information which lends biological plausibility to effects observed in humans or animals?
Is the mechanism or mode of action consistent with the type of effect, caused by similar substances, such as plants in the same family?
Is there information suggesting that the concentrations used in vitro are relevant or irrelevant? The answers to these questions determine the appropriate level of concern, as described in Table Information such as that in the right column warrants higher levels of concern about public safety and risk of consumption.
In vitro information such as that described in the left column warrants lower levels of concern, while information described in the middle column warrants concern, but additional information may be required to warrant conclusion that a risk exists. In addition to providing the raw materials for evolution, genetic alterations are associated with a large proportion of human diseases, including cancer.
Chromosomal aberrations, such as deletions, inversions, and translocations, have been associated with leukemia, lymphoma, and some solid tumors. The term genotoxic is applied to substances or physical agents like ultraviolet light or X-rays that have an intrinsic ability to damage DNA not simply due to gross toxicity that may secondarily result in damage to DNA.
Different genotoxicants interact with DNA in different ways, cause different types of DNA alterations, and can be detected using different assay systems Preston and Hoffmann, For example, substances that cause heritable changes in DNA sequence are called mutagens. A mutation may result from an alteration in a single DNA base or addition or deletion of one or more DNA bases point muta-.
Standardized a subcellular and cellular assays validated for the purpose of establishing in vivo toxic effect. Standardized subcellular and cellular assays validated for the purpose of establishing in vivo toxic effect. Multiple different assays suggesting the same pathological condition or endpoint. Knowledge of presence of toxicant in blood or tissue enhanced by knowledge of concentrations comparable with those causing toxicity in vitro. This is the type of mutation that occurs in the heritable human disease sickle-cell anemia.
Some genotoxicants cause visibly identifiable types of changes—alterations in chromosome structure or chromosome number chromosome mutations, or clastogenicity.
These types of changes can be detected by observation of cells generally fixed and stained with a microscope. The ability of some substances to cause DNA damage can also be assessed by determining whether the substance increases the normal level of activity of certain DNA repair processes or whether it is more lethal to cells.
Results from microarray experiments show a gene expression pattern predictive of dangerous compounds b. Knowledge of presence of toxicant in blood or tissue at concentrations comparable with those causing toxicity in vitro.
However, these types of data may become more important as the field progresses. If the value of genomics, proteomics, and other new technologies in identifying dangerous compounds is demonstrated in the future, then such results may warrant more concern than is indicated in this figure.
Because of the importance of genetic alterations in cancer development, and the observation that many carcinogens were also mutagenic, the original focus of genetic toxicology on evaluating potential hazards to the human gene pool shifted in the early s to the use of genotoxicity assays as rapid screens for potential carcinogens Ames et al. The subsequent finding that many animal carcinogens are not genotoxic and that some chemicals show genotoxic activity in at least some assay systems, but do not show detectable carcinogenic activity in standard animal carcinogenicity studies, has somewhat lessened the attractiveness of genotoxicity assays Tennant et al.
Some programs require a mammalian gene mutation assay in addition to the typical Ames bacterial gene mutation assay, and the test battery may include an assay for induction of DNA repair. Also, testing in additional assays may be triggered by positive results in the initial battery. While genotoxicity assays are no longer viewed as a quick and inexpensive way to detect chemical carcinogens, they do still have substantial utility.
Evidence of lack of genotoxicity, together with positive evidence of another mode of carcinogenic action, may lead to use of a risk assessment model that is not linear at low doses and predicts lesser risk at low doses than the default low-dose linear model. In summary, genotoxicity data are not currently used alone in regulation of chemicals, and this is not likely to change.
More commonly they are used to trigger a requirement for carcinogenicity testing. Internally, companies may use genotoxicity assays at an early point in product development as part of a screening system to identify promising leads—they may not wish to risk investing large amounts of time and money on a chemical that may turn out to be a carcinogen. While it is estimated that only about 60 to 70 percent of mutagens are carcinogens depending on the system Tennant et al.
Another example of a shortcoming of in vitro studies relates to concentrations of molecules, especially as they compete for nuclear receptors Intracellular receptor proteins that bind to hydrophobic signal molecules such as steroid and thyroid hormones or intracellular metabolites and are thus activated to bind to specific DNA sequences which affect transcription. For example, the vitamin D metabolite, 1,D Primary biologically active vitamin D hormone.
Activates the vitamin D nuclear receptor. Produced by hydroxylation of D. Also known as 1,dihydroxycholecalciferol, 1,hydroxyvitamin D and calcitirol. Animal studies and clinical trials are two forms of in vivo research.
In vivo testing is often employed over in vitro because it is better suited for observing the overall effects of an experiment on a living subject. While there are many reasons to believe in vivo studies have the potential to offer conclusive insights about the nature of medicine and disease, there is a number of ways that these conclusions can be misleading.
For example, a therapy can offer a short-term benefit, but a long-term harm. Although in silico studies represent a relatively new avenue of inquiry, it has begun to be used widely in studies which predict how drugs interact with the body and with pathogens. For example, a study used software emulations to predict how certain drugs already on the market could treat multiple-drug-resistant and extensively drug-resistant strains of tuberculosis.
There is a variety of in silico techniques, but the two that are discussed the most in connection with the Marshall Protocol A curative medical treatment for chronic inflammatory disease. Based on the Marshall Pathogenesis. Table of Contents In vitro studies. To cite one example among many, the lysates or extracts from culture-grown spirochetes do not reflect antigens expressed in the mammalian Borrelia: Tunev 1 Because of this, in vitro studies may lead to results that do not correspond to the circumstances occuring around a living organism.
Bacterial sequencing techniques — As an alternative to in vitro methods for identifying bacteria, various in silico methods which sequence bacterial DNA and RNA have been developed. The most commonly used use is polymerase chain reaction PCR. PCR takes a single or few copies of a piece of DNA and increases it across several orders of magnitude, generating millions or more copies of a particular DNA sequence. Urinalysis is a physical, chemical, and microscopic examination of urine, and serology is the study of blood serum.
To unlock this lesson you must be a Study. Login here for access. Did you know… We have over college courses that prepare you to earn credit by exam that is accepted by over 1, colleges and universities.
You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level. To learn more, visit our Earning Credit Page.
Not sure what college you want to attend yet? The videos on Study. Explore over 4, video courses. Find a degree that fits your goals. In Vivo Studies Quiz Course. Try it risk-free for 30 days. Adrianne Baron Adrianne has taught high school and college biology and has a master's degree in cancer biology. Add to Add to Add to. Want to watch this again later?
This lesson is going to look at the two main categories for how we study the body. We will cover in-vitro as well as in-vivo studies and look at some of the most common processes used. Studying the Body Very early in life, you found happiness in learning more about your body.
In Vitro Studies People aren't very willing to subject their bodies to things like surgery and medication when we're not sure what will happen to them once they take the pills or have the procedure. Cytology studies help to determine the differences between normal and cancerous cells Bacterial cell culture studies are something that you perform regularly when need to learn more about what medications are effective against certain bacterial infections of the body. In Vivo Studies Once you and other researchers understand the possible ways that the body may react to something, then you'll conduct studies within the body.
Try it risk-free No obligation, cancel anytime. Want to learn more? Select a subject to preview related courses: Mice are great animal models Now that you've proven what happens in the laboratory using animal models, the government will finally allows you to do in vivo studies on humans. Lesson Summary Let's go through a recap of the main points from this lesson. Cytology - studies on cells obtained from the body Bacterial cell culture - laboratory studies on bacteria Histology - studies on body tissues removal of body tissue is a tissue biopsy Bodily fluid studies are used to study sputum, blood, lymph, and urine.
Animal models - use of animals to study what may happen in the human body Human research - studying how things affect the human body after you've completed animal model studies; usually use volunteers.
Register to view this lesson Are you a student or a teacher? I am a student I am a teacher. Unlock Your Education See for yourself why 30 million people use Study.
Become a Member Already a member? What teachers are saying about Study. Earning College Credit Did you know… We have over college courses that prepare you to earn credit by exam that is accepted by over 1, colleges and universities. To learn more, visit our Earning Credit Page Transferring credit to the school of your choice Not sure what college you want to attend yet?
Browse Articles By Category Browse an area of study or degree level. You are viewing lesson Lesson 1 in chapter 13 of the course:.
Looking for other ways to read this?
Differences between in vitro, in vivo, and in silico studies There are three broad categories of experiments: studies, studies, and studies. Each study type has. In vivo and in vitro are common scientific terms to describe where research In an in vivo experiment, scientists are conducting their studies in. J Reprod Fertil. Jan;(1) Studies in vivo and in vitro on the initiation of follicle growth in the bovine ovary. Braw-Tal R(1), Yossefi S.