It is now known that organs communicate with each other using "message substances," and in recent years, "message substances" called "exosomes" have been attracting attention. Exosomes have "certain characteristics" that differ from those of conventional substances, and research is underway to apply these characteristics to medical treatment and other applications.
Clarification of Exosomes
Exosomes are capsule-like substances produced by cells. When magnified under an electron microscope, it is shaped like a round ball with protrusions. It is only 1/10,000th of a millimeter in size. Exosomes are produced by every cell in the body. Based on the number of exosomes in our blood, it is thought that there are over 100 trillion exosomes flowing through our bodies.
Exosomes are also unique in that they contain a variety of "message substances. One of them is a genetic material called microRNA. MicroRNA is a member of DNA and is known to regulate gene function. It was originally thought to exist only in cells, but 11 years ago, Swedish scientist Jan Lotvall discovered that it is contained in exosomes. Since then, research to elucidate the function of exosomes has been conducted all over the world.
Exosomes' relevance to disease
What is now being elucidated is the link between exosomes and disease. Cells in the body constantly secrete exosomes, and their secretion is said to increase in disease.
One such disease is cancer. Cancer cells have been studied to produce various "message substances" such as cytokines, and it has been confirmed that cancer cells also secrete exosomes. For example, cancer spreads to other organs through metastasis. It has become clear that exosomes produced by cancer cells are greatly involved in this metastasis. One such example is the metastasis of ovarian cancer to the peritoneum.
The ovaries, which are located behind a woman's uterus, are only about the size of a thumb, and even if cancer is present, it is painless and difficult to notice. As a result, it is known to metastasize to the peritoneum, which covers and protects the surface of internal organs. Once cancer has metastasized to the peritoneum, it can spread to many places in the peritoneum, a condition known as "seeding. Once cancer spreads to the peritoneum, the area to be treated expands and treatment becomes difficult.
However, the surface of the peritoneum is normally lined with protrusions that act as a barrier to prevent foreign substances such as cancer cells from entering the peritoneum. Therefore, how they metastasize to the peritoneum has been shrouded in mystery. However, exosomes released by ovarian cancer adhered to the peritoneum and entered the cells that make up the peritoneum. The "message substance" contained in the exosomes is then delivered to the recipient. The message, so to speak, is a message of death: "Your role is over. The cells on the surface of the peritoneum then begin to die. As this process is repeated over and over again, a large crater-like hole is created on the surface of the peritoneum, and ovarian cancer cells attach to the hole. The cancer cells enter the peritoneum through the hole and multiply without difficulty.
In addition to cancer, exosomes have also been found to be associated with diseases such as dementia and neurological intractable diseases.
Exosomes Support Health
On the other hand, exosomes are known not only to cause diseases, but also to play an important role in supporting our health. An example is fertilization. The egg actually secretes exosomes on the surface of its membrane. Essentially, these exosomes prevent the membrane from aging, but they also act as a key for the sperm to enter the egg. In the experiment, when the egg did not have exosomes on its surface, the sperm could not enter the egg and fertilization was not possible. It is hoped that this technology will be applied to infertility treatment in the future.
Furthermore, it has been linked to skin aging. A major French cosmetics company has revealed that skin cells exchange exosomes with each other. Cells called keratinocytes, which make up the skin, secrete exosomes when exposed to UV light. Another cell, the melanocyte, receives the exosomes and secretes a substance called melanin. This melanin, which is known to protect the skin from UV rays, causes blotches and freckles.
Cosmetics companies have analyzed various ingredients related to this mechanism, and have also developed cosmetics based on this analysis.