Extracellular Vesicles (EVs)

Extracellular vesicles (EVs) are tiny membrane-bound particles released by cells into their surrounding environment. They contain proteins, metabolites, and nucleic acids, and are enclosed within a lipid membrane, a thin fatty layer structurally similar to the cell membrane itself. This membrane protects the vesicle’s contents and allows it to travel safely and stably between cells.

For many years, scientists believed that extracellular vesicles mainly served as “cellular garbage bags” used to remove unnecessary materials from the cell. Today, however, it is understood that they play a central role in communication between cells and influence various biological processes throughout the body.

Extracellular vesicles are found in many bodily fluids, including blood, urine, saliva, and cerebrospinal fluid. They are commonly classified according to their size and the way they are formed:

• Small vesicles that are generated inside the cell and later released from it.
• Vesicles formed by budding, a process in which a small protrusion separates from the cell membrane.
• Vesicles released during programmed cell death, a natural process in which old or damaged cells break down.

In current research, it is not always possible to determine with certainty the exact origin of every extracellular vesicle. As a result, scientists often use broader classifications based on the vesicles’ size or physical characteristics.

Extracellular vesicles play important roles in normal physiological conditions and are involved in regulating the immune system, blood clotting, tissue development, and processes of healing and repair. Alongside their functions in healthy conditions, they also participate in disease processes. In cancer, for example, tumor cells release large quantities of extracellular vesicles. These vesicles can alter the tumor environment and, in some cases, prepare distant tissues to receive cancer cells, a process that may contribute to the formation of metastases.

Because extracellular vesicles are capable of carrying biological materials and information from the cells that release them, they have attracted major interest in modern medicine. In the field of diagnostics, they may provide valuable information about processes occurring within the body through noninvasive analysis of bodily fluids. At the same time, scientists are exploring the possibility of using extracellular vesicles as biological “messengers” capable of delivering drugs and therapeutic substances directly to diseased cells in a targeted manner.

Frequently Asked Questions

1. What are extracellular vesicles (EVs)?

Extracellular vesicles are tiny particles surrounded by a thin lipid membrane, a membrane similar to the cell membrane, that are released by cells into their external environment. They carry a variety of biological materials, including proteins, lipids, and nucleic acids (mainly RNA and sometimes DNA). When these vesicles are taken up by other cells, they can influence cellular activity, making them an important mechanism of communication between cells.

2. What types of extracellular vesicles exist?

Extracellular vesicles are generally classified according to the way they are formed within the cell. The main types include exosomes (generated inside the cell and later released), microvesicles (which bud directly from the cell membrane), and vesicles associated with programmed cell death. Because it is not always possible to determine their exact origin with certainty, researchers often use simpler classifications such as “small vesicles” or “large vesicles.”

3. How do extracellular vesicles transfer information between cells?

After being released from a cell, extracellular vesicles can attach to a target cell, be absorbed into it, or fuse directly with its membrane. In this way, they deliver their biological contents directly into the recipient cell and alter its activity. The extent of the effect depends on the type of vesicle, the type of recipient cell, and the surrounding biological conditions.

4. What is the connection between extracellular vesicles and cancer?

In cancer, tumor cells use extracellular vesicles to communicate with and manipulate their environment. These vesicles can promote the formation of new blood vessels that supply the tumor with nutrients, weaken the immune system’s response against the cancer, and even “prepare the ground” in distant tissues to facilitate the spread of cancer cells (the formation of metastases).

5. Why are extracellular vesicles important in medical diagnostics?

Extracellular vesicles are considered highly promising tools in the field of “liquid biopsy” (diagnosing diseases through simple blood or urine tests instead of surgery or needle-based tissue sampling from internal organs). Because the vesicles contain materials originating from the cells that released them, analyzing them can provide an accurate “report” about the condition of tissues throughout the body. However, before this approach can become routine in clinical medicine, more standardized and precise methods for isolating vesicles from bodily fluids are still needed.

6. Can extracellular vesicles be used as medical treatments?

Scientists are exploring the use of extracellular vesicles as vehicles for targeted delivery of drugs or therapeutic RNA molecules. One of their major advantages is that they are natural biological structures, meaning the body does not reject them easily, and they can reach target cells with a high degree of precision. This field is currently in advanced stages of research.

7. Do extracellular vesicles contain DNA and RNA?

Yes. These vesicles carry various types of nucleic acids, including messenger RNA (mRNA), microRNA, and sometimes even fragments of DNA. These materials can alter gene expression in the cells that absorb them. In addition, the presence of DNA within vesicles circulating in the bloodstream may help physicians identify genetic changes (mutations), associated with different diseases without directly sampling the affected organ itself.

8. What is the difference between extracellular vesicles and liposomes?

Liposomes are completely artificial vesicles manufactured in laboratories for the purpose of drug delivery. Extracellular vesicles (EVs), by contrast, are natural vesicles produced by living cells within the body. EVs are more complex and biologically sophisticated because their membranes contain unique proteins and sugars derived from the original cell. These components help them navigate through the body and reach specific target cells more precisely than synthetic delivery systems.