No Need to Learn Latin! Understanding In Vivo, In Vitro, and Ex Vivo Techniques

In vitro fertilization, ex vivo gene therapy, and in vivo clinical trials are exciting techniques in the medical field. The words that describe these methods (in vitro, in vivo, and ex vivo) are common adjectives used to describe research, treatments, or procedures. Although these words sound similar, they are distinct from each other and have unique uses and advantages. Let’s explore the meanings and uses of in vitro, in vivo, and ex vivo techniques.

In Vivo
In vivo describes when a study is done inside a living organism, such as a human or animal. In vivo is Latin for “within the living”. Clinical trials for medicines are often done in vivo because the conditions of a living organism cannot be replicated outside the body. Usually, in vivo treatments are tested on animals first, such as mice or rabbits, and if they produce the desired effects, clinical trials then open to humans. One advantage of in vivo clinical trials is that it shows the entire body’s response to a treatment or drug, including how the drug is metabolized by the body and the body’s response to the drug or treatment.

In Vitro
In vitro is Latin for “in glass”: it describes treatments that are done in a controlled environment such as a test tube or petri dish. The growth of cells, tissues, or bacteria that are in vitro is called a culture. Cultures are used extensively in the early stages of research because testing the responses of cells or tissues is much easier when they are isolated in a culture. Cultures can be easily replicated which is much cheaper than paying for living subjects to participate in an in vivo clinical trial! However, in vitro testing is mostly done in early stages of research because conditions in a petri dish or glass tube cannot show the effects of treatment on the entire body.

In vitro fertilization
In vitro fertilization (IVF) is a fertility treatment consists of extracting one or more eggs from a woman’s ovary and putting them into a petri dish with a man’s sperm. The dish is left in a controlled environment for three to five days, and then the fertilized egg is inserted into the woman’s uterus. She can then carry the embryo to full term within her body. IVF has helped women and men who struggle with fertility to have children with the assistance of a controlled environment outside the body, which is a great example of the advantages of in vitro treatments.

Ex Vivo
Ex vivo treatments combine elements of in vivo and in vitro to advance the boundaries of medical treatments and therapies. Ex vivo is Latin for “from life”: it involves cells or tissues taken from a living organism, such as a human or animal, and transports them into an artificial environment with very similar conditions. The new environment is as similar as possible to the body where the cells and tissues were extracted from so that they can later be implanted back into the body! An advantage of ex vivo treatments is that they provide conditions similar to in vivo experiments while benefiting from the isolation that in vitro methods have.

Ex vivo gene therapy
A revolutionary use of ex vivo methods is in the field of gene therapy, which prevents or treats disease by introducing new DNA into cells. Gene therapy is needed when the body has a defective gene and can’t produce necessary proteins. In ex vivo gene therapy, cells are taken from the body and exposed to a virus in an artificial environment. The virus inserts the gene into the cell’s DNA and the cell with the functioning gene is injected or transplanted back into the body. Ex vivo gene therapy has treated genetic conditions such as hemophilia and is being studied in clinical trials to determine whether it can be used to treat acquired diseases such as cancer.

In vivo, in vitro, and ex vivo describe the methods used for research and treatment and they differ in whether they take place inside the body or in a controlled environment such as a petri dish or test tube. The words may be in a different language but you don’t need to be an expert in Latin to understand how these methods are used to test new drugs and improve medical treatments!

References
https://www.healthline.com/health/in-vivo-vs-in-vitro
https://www.verywellhealth.com/what-does-in-vivo-and-in-vitro-mean-2249118

What is Targeted Drug Delivery?

Targeted drug delivery is a method of delivering medication with the goal of maximizing its effects on specific parts of the body. This approach aims to minimize unwanted effects of the medication on non-diseased tissue, while at the same time prolonging the drug’s actions on its target.

Regular drug delivery utilizes blood circulation as a means to transfer the active substance to its target. The main disadvantage of that approach is that a very small percentage of the initial dose manages to reach the intended target, while the rest affects unintended cell populations. Targeted drug delivery aims to mitigate this exact issue by various ways.

Targeted drug delivery can be achieved by increasing the molecular specificity of the medication. An example of this approach is the use of monoclonal antibodies, which are commonly used in cancer treatment. Monoclonal antibodies are normally created by the immune system in response to a specific antigen, and they can only bind on cells that have that antigen on their surface. Thus, when creating monoclonal antibodies for different forms of cancer, scientists find protein targets that only exist on the surface of the cancer cells. This means that the treatment will only affect these cell populations, while having essentially no effect on any other cells they encounter through blood circulation.

When molecular specificity cannot be achieved, there is another effective way to increase drug concentration at the intended target site. Researchers have developed various delivery vehicles that can protect drugs from degradation and increase their amount in blood circulation, leading to higher concentrations and longer action time. Nanotechnology has played a significant role in the development of new delivery vehicles that can bypass the body’s immune response while being non-toxic.

Resources:

Drug Delivery: https://www.technologynetworks.com/drug-discovery/articles/drug-delivery-322035

Targeted Drug Delivery: https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/targeted-drug-delivery

What are the Main Functions of Blood?

From childhood cuts to Vampire films, everyone knows what blood looks like outside of the body: bright, red, and runny. But what exactly does blood do?

Blood is actually very hard at work within the body. The primary responsibility of blood is transportation: the blood delivers oxygen from the lungs to the cells of the body, transports carbon dioxide produced in the body back to the lungs for exhalation, transports critical nutrients and hormones to cells, and removes waste products. However, blood also works to maintain the overall function of the body via protection mechanisms and regulation functions. Learn more about the functions of blood below!

Protection: Blood plays a critical role in defending the body against external and internal threats to overall health and wellness. Some white blood cells within the blood work to protect the body from disease-causing bacteria entered into the bloodstream through an open wound, while others seek out and eradicate harmful body cells infected with viruses or cells with mutated DNA that could potentially cause cancer. Platelets in the blood also initiate clotting at the site of an injury to prevent harmful amounts of blood loss.

Regulation: Blood helps regulate and maintain the proper temperature within the body. When we are too hot, blood vessels become wider and allow more blood to flow through the skin, which causes more heat to be lost. Blood vessels leading to the skin capillaries become wider allowing more blood to flow through the skin and more heat to be lost to the environment. This is called vasodilation. When we are too cold, blood vessels constrict – which allows less blood to flow through the skin and conserves the core body temperature. This is called vasoconstriction. Blood also helps regulate proper pH and water levels within the body.

As you can see, blood plays a critical role in keeping your body safe, healthy, and functioning properly. Good thing you have around 1.5 gallons of blood inside of you!

Resources

Khan Academy: https://www.khanacademy.org/science/biology/human-biology/circulatory-pulmonary/a/components-of-the-blood

Medical News Today: https://www.medicalnewstoday.com/articles/196001

Texas Heart Institute: https://www.texasheart.org/heart-health/heart-information-center/topics/blood/

What’s the Difference Between Chemotherapy, Radiation Therapy, Immunotherapy?

The goal of cancer treatment is to cure, shrink, or stop the progression of a cancer. Depending on the particular situation, patients may receive one treatment or a combination of treatments. There are many different types of cancer treatments, which will be described in this post.

Doctors often recommend chemotherapy as a treatment for cancer. Chemotherapy uses drugs that kill dividing cancer cells and prevent them from growing. It is considered a systemic treatment, because it affects cancer cells throughout the body, which includes potential metastasized growths. Many chemotherapy drugs have adverse effects, some of which may be severe. Doctors recommend chemotherapy after assessing the risk for side effects, when they believe that the specific patient will have significant benefits from it.   A person will often have chemotherapy as part of an overall treatment plan, which may also include surgery and radiation therapy. These treatments are effective in many cases of cancer. However, their effectiveness will often depend on the stage of the cancer as well as its type. Overall, it is calculated that about 50% of cancer patients will receive chemotherapy as part of their treatment at some point.

This leads to the next cancer treatment of radiation therapy. Radiation therapy uses waves of energy, such as light or heat, to treat cancers and other tumors and conditions. Radiation inhibits tumor growth by destroying the genetic material responsible for cancer cell division, while at the same time having little effect on regular cells. Radiation therapy is a localized treatment, because the beams are targeted towards the affected region only. Doctors may recommend radiation for cancer at different stages. In the early stages, radiation therapy can help reduce the size of a tumor before surgery or kill remaining cancer cells afterward. In the later stages, it may help relieve pain as part of palliative care.

One of the more recent types of cancer treatment is immunotherapy, which utilizes our immune system to help us fight cancer cells. The immune system helps our bodies fight infections and other diseases. Drugs used in immunotherapy are boosting the ability of our immune system to detect cancer cells and have a stronger response against them. Examples include monoclonal antibodies, which bind onto cancer cells and mark them for destruction, as well as immune system modulators, that boost immune responses. Immunotherapy is also a systemic form of cancer treatment, and can provide a significant benefit in combination with other treatments.

How Does Blood Clot?

The blood clot process begins whenever our skin or blood vessel wall breaks and blood starts coming into contact with the outside. That triggers a series of chemical reactions that result in the formation of a clot, which aims to stop the bleeding and help the vessel heal.

Initially, blood vessels in the area will constrict, to ensure that blood flow is decreased. During this process, small blood particles called platelets will start binding together in the damaged area, creating what is called a platelet plug. This leads to the next step of the process, in which several blood clotting factors are activated and create a chain of reactions that leads to the creation of fibrin, a fiber-like protein that helps increase the size of the clot and stabilize it.

If the clotting process does not stop when appropriate, dangerous clots can be formed in other parts of the body. This is why there is a rigorous control system ensuring that the clotting reaction stops when the vessel is sufficiently blocked to prevent bleeding. However, there are certain blood disorders that lead to increased clotting, such as thrombophilia.

High cholesterol concentrations can form plaques in arteries, making it difficult for blood to flow in the area. If these plaque breaks open, they will form a clot that travels in the blood stream. Most heart attacks and strokes happen when a plaque suddenly bursts.

Blood clots can also form when something obstructs the regular flow of blood in the body. If blood pools in the blood vessels or heart, the platelets are more likely to stick together. Atrial fibrillation and deep vein thrombosis (DVT) are two conditions where slowly moving blood can cause clotting problems. If undetected, these conditions can lead to serious heart problems or even death, which is why clotting factors are often included in blood analyses when the patient has a known risk for these diseases.

Parts of a Human Cell

The cell is the main building unit for all living organisms, from bacteria to humans. All complex organs and systems are made up from billions of individual cells working together, but also individually. In the human body, cells come in different shapes depending on the tissue they belong to. However, all cells have four parts in common: the plasma membrane, cytoplasm, ribosomes, and DNA.

The plasma membrane (also called the cell membrane) is a thin coat of lipids that surrounds the cell. It forms the physical boundary between the cell and its environment and therefore is very important for all interactions between the cell and the outside. Many proteins assist with these interactions by docking on the plasma membrane and binding to outside molecules. Furthermore, cells can send signaling molecules through their plasma membrane to communicate messages to other parts of the tissue or body.

Next, the cytoplasm refers to all of the cellular material inside the plasma membrane, other than the nucleus. Cytoplasm is gel-like in its texture and contains mostly water, salt and other molecules, as well as all organelles that assist with cellular function, such as ribosomes.

Ribosomes are structures in the cytoplasm where proteins are made. They consist of RNA molecules and proteins, and their main role is to translate genetic sequences to proteins. Each cell may have a large number of ribosomes which either exist as free particles in the cytoplasm, or are organized in larger structures.

Finally, the DNA is a nucleic acid that contains all the necessary genetic information for the cell to function. The DNA is usually tightly packed in the nucleus of the cell, where it is protected from the outside environment. If we were to measure the length of a DNA molecule, each cell alone contains about 6 feet of DNA. The human DNA contains about 25,000 gene sequences, as well as many sequences that do not encode proteins and are either evolutionary remnants or regulatory components.

What is RNA and What are its Types?

RNA is the second most well-known ribonucleic acid after DNA. When it comes to structure, it is highly similar to DNA, but has some important differences. For example, RNA has one distinct nucleotide called uracil (or U) instead of thymin (or T). Furthermore, RNA commonly exists in single-strand format, while DNA is almost always double-stranded.

Human DNA GraphicAs we discussed in the previous post, all human cells contain genetic information for protein expression in the form of DNA. Our DNA is tightly packed in the cell nucleus to ensure protection from outside factors. However, almost all processes that are required for protein generation are taking place outside the nucleus. For this reason, there are mechanisms in place for creating copies of genetic information that can traverse from the nucleus to other locations. This is where RNA comes into play, since it can be synthesized in a complementary manner to DNA and contain the same type of genetic information. Furthermore, RNA can interact with proteins and create necessary complexes for various cell processes.

The main types of RNA are the following:

  • mRNA: Also known as messenger RNA, mRNA is a single-stranded RNA molecule that contains information for generating a protein sequence. It is created in the nucleus through the process of transcription, during which the two DNA strands are temporarily separated to copy the information of one gene onto the new mRNA molecule. Then, mRNA can exit the nucleus and go to the ribosomes, where proteins are generated using its information.

  • tRNA: tRNA, or transfer RNA, is a small RNA molecule that is essential for protein synthesis. Proteins consist of amino acids, and each amino acid has a 3-letter code (or codon) in the DNA or mRNA that corresponds to it. This way a DNA or RNA sequence can be translated to a protein sequence. Codons are examined in series, and tRNA is responsible for bringing the correct amino acid depending on each codon. This is done by utilizing the complementary structure of one tRNA part to the codon triplet.

  • rRNA: Ribosome RNA (or rRNA) is an RNA molecule that is a fundamental component of ribosomes. As mentioned before, ribosomes are the machinery for protein synthesis in the cell. There are two rRNA subunits in each ribosome, a large one and a small one. Along with proteins and enzymes, they facilitate the process of translating an mRNA sequence into protein.

Honorable Mentions

There are some other RNA types in human cells that are not commonly known but are often used in molecular biology research. For example, micro RNA or miRNA is a small single-strand RNA molecule that can silence other types of RNA (such as mRNA) by binding to them using the rules of complementarity. Small interfering RNA or siRNA is a double-stranded RNA molecule that has a similar goal, but acts by triggering an mRNA degradation response called RNA interference. Overall, these molecules can affect protein expression levels by effectively silencing certain genes without affecting the DNA itself.

More sources on RNA:

— Vicky Kanta

How is DNA Organized in the Human Cell?

Our DNA contains the genetic code for creating every single protein in our bodies. All cells contain an almost identical copy of our DNA in their nuclei. However, since DNA molecules can be over 6 feet long if stretched out, they are packed and organized in a very specific manner in order to fit in the very small space of the nucleus. Here are the different levels of DNA organization:

  • Human DNA GraphicDouble helix DNA: This is the unpacked form of our DNA, in which two complementary strands are chemically linked together and are spiraling around counterclockwise, forming a “ladder-like” double-stranded molecule. Each “step” of the ladder consists of a pair of nucleotides, which are the basis of DNA sequences and are commonly known by their initials (A and T, G and C). In every cell, genetic information exists in two copies, with one coming from each of the two parents.

  • Nucleosome: This is the first step of “packaging” inside the nucleus. In a nucleosome, a segment of double helix DNA is wrapped around a set of proteins called histones. Usually, the length of DNA in each nucleosome is fixed to about 150 nucleotide pairs. When many nucleosomes are seen together in series, they have the appearance of “beads on a string”, which is a common term used for this level of organization.

  • Chromatin: In this next level, nucleosomes are tightly grouped together forming a fiber that is about 30 nm in diameter. There are two types of chromatin, namely euchromatin and heterochromatin, that differ in how compact they are and whether they allow unpacking for gene expression. These two types can be located on a microscope in different parts of the nucleus.

  • Chromosome: This is the final form of DNA organization inside the nucleus. In the chromosome form, chromatin is even more tightly packed. In the end, the entirety of the double helix DNA is packaged in 23 pairs of chromosomes, that fit in the 6μm wide cell nucleus.

It is worth mentioning here that DNA does not only exist in the cell nucleus. There is some amount of DNA in other organelles inside our cells called the mitochondria. Mitochondrial DNA is also organized in small chromosomes and contains genetic information for mitochondrial function. Unlike nuclear DNA, which is inherited from both parents, mitochondrial DNA is only inherited from the mother via the egg.

More DNA organization sources:

— Vicky Kanta

What is Herd Immunity?

Infectious diseases caused by microorganisms such as bacteria and viruses can spread widely within a community. In particular, densely populated areas like big cities allow rapid disease transmission, because people are frequently in close proximity. When a certain proportion of the community acquires immunity for a disease, then further spread is limited, because immune individuals usually cannot get re-infected or infect others. This is when we reach herd immunity for this particular disease.

There are two main ways to achieve herd immunity. The first way is for the pathogen to infect a large number of people, who then recover and become immune. The second way is through vaccination, which provides future immunity against the disease by stimulating the natural pathways that lead to it. Nowadays, many infectious diseases are either eliminated or controlled through vaccination, such as measles, chickenpox, and the seasonal flu. In fact, a vaccine is the safest way towards herd immunity, leading to less sick people and therefore a lower overall number of disease-related deaths and complications.

Depending on the size of the community, as well as the infectiousness of the disease, the percentage of people that must become immune before herd immunity is achieved can vary. For example, measles requires 93-95% vaccination rates, whereas polio requires around 80-86%. This is why timely vaccination of children at the recommended schedule is really important; skipping or delaying a dose does not only increase chances of disease susceptibility for the child, but also contributes to a decrease in herd immunity and therefore allows previously controlled diseases to reappear like the recent resurgence of the measles.

Herd immunity is highly important for our society, because it is an important tool to curtail or even eliminate infectious diseases. Furthermore, it protects some of the most vulnerable members in our communities from getting sick, such as the elderly, those who can’t have a vaccine for medical reasons, or the immunocompromised, as well as pregnant women and infants. For this reason, there is extensive research and funding dedicated towards the development of safe and effective vaccines.

More resources on herd immunity and vaccination:

What is Diabetic Nephropathy?

Diabetic nephropathy, or diabetic kidney disease, is a common condition associated with Type I or Type II diabetes. It is estimated that about 20-40% of diabetic patients develop some form of kidney disease. If undetected, diabetic nephropathy can be a debilitating and dangerous disease, which is why people with diagnosed diabetes have to be frequently monitored for kidney function.

The main role of the kidneys is to filter the blood and remove waste and harmful products, while maintaining proteins, water and other useful substances. More specifically, kidneys contain small blood vessels called glomeruli that are responsible for filtering a large volume of blood every day. There are two kidneys in the human body, working together in a complementary manner. However, if one kidney stops working, the glomeruli in the other kidney start filtering more blood to compensate for the loss of function. This is why people can live without issues if they have at least one functioning kidney.

In unregulated diabetes, blood sugar levels are elevated, which slowly damages the glomeruli. Furthermore, many diabetics also have high blood pressure, which also stresses kidney function over time. When glomeruli stop functioning properly, protein starts leaking in the urine and eventually harmful waste may stay in the bloodstream, causing severe problems.

Thankfully, diabetic nephropathy can be prevented in most cases by maintaining regulated blood sugar levels. However, even if a patient reaches the early stages of nephropathy, blood sugar regulation can slow down the progression of kidney disease. If left untreated, both kidneys may fail, in which case interventional treatments such as dialysis or even a kidney transplant may be necessary. Transplants can come from compatible organ donors that have fully functional kidneys and a compatible blood type to the recipient. Frequently, transplants come from living donors, which often are family members wanting to help their loved ones.

More resources on diabetic nephropathy

  1. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/diabetic-kidney-disease

  2. National Kidney Foundation. https://www.kidney.org/atoz/content/Diabetes-and-Kidney-Disease-Stages1-4

  3. American Heart Association. https://www.heart.org/en/health-topics/diabetes/why-diabetes-matters/kidney-disease–diabetes

— Vicky Kanta