In this blog post, we will look at the definition and types of stem cells and how their ability to differentiate into various cells can lead to medical innovation.
Stem cells are also called hepatocytes and blast cells. All of these names imply that they are cells that can develop into any tissue. Thanks to this potential, stem cells are presenting innovative possibilities in the medical field, and active research is being conducted, especially in the field of incurable disease treatment and regenerative medicine. In other words, stem cells are “undifferentiated” cells that have not yet differentiated. As such, they are cells that have not yet acquired the characteristics of a tissue, so they can differentiate into various tissue cells if given the right conditions. Stem cells are mainly collected from early-dividing embryos, and can be cultured into a specific cell system by inputting them in advance.
The term “stem cell” was first proposed by Russian scientist Maksimov at the Berlin Hematology Society in 1908, and it was not until 1963 that the existence of stem cells was proven by a research team at the University of Toronto in Canada. Since then, stem cell research has expanded into various fields of life science and medicine, and scientists have begun to explore the infinite possibilities of stem cells. Subsequently, test-tube babies and mouse cloning were successfully carried out in the UK and the US, and stem cells began to attract attention in earnest with the birth of Dolly the cloned sheep through somatic cell cloning. In 2004, Dr. Hwang Woo-suk announced that he had succeeded in cloning embryonic stem cells using human eggs in South Korea, but in 2005, a survey revealed that the research data had been fabricated, causing a huge stir. This incident sparked a global debate on bioethics and scientific responsibility, and since then, discussions on the transparency and ethical standards of scientific research have become more active. In 2013, a research team at Oregon Health and Science University announced that they had succeeded in cloning human embryonic stem cells, which was recorded as the first scientifically verified case of cloning human embryonic stem cells. This success marked a new turning point in stem cell research, and stem cell research has since continued to develop while overcoming various ethical and technical challenges.
There are also several types of stem cells: embryonic stem cells, adult stem cells, and pluripotent induced stem cells. First, embryonic stem cells are derived from fertilized eggs created by the fertilization of a sperm, a male reproductive cell, and an egg, a female reproductive cell. Embryonic stem cells have the strongest differentiation ability and can develop into various body tissues, from nerve cells to heart cells. Usually, stem cells are collected and cultured from embryos on the fourth day after fertilization of the egg and sperm, but they can also be isolated by somatic cell transplantation. The somatic cell transplantation method involves removing somatic cells from the body, separating the nucleus containing the genetic information of the cells, removing the nucleus of the egg, inserting the separated nucleus into it, and culturing it to obtain embryonic stem cells with the same genetic information. Embryonic stem cells are also called pluripotent stem cells because they have the ability to differentiate into various types of cells. This ability opens up the possibility of transplantation therapy, but at the same time, it also carries the risk of tumor formation due to incorrect differentiation. Since they do not have an immune rejection response, can proliferate in large quantities, and can differentiate into almost all body cells, they are easy to transplant. However, they have the disadvantage of being difficult to control their differentiation, which can lead to the possibility of becoming cancerous, and they inevitably require the destruction of egg donors and fertilized eggs, which has raised significant ethical concerns.
Adult stem cells are present in very small amounts in each tissue of the body. Unlike embryonic stem cells, which can differentiate into various types of cells, adult stem cells are predetermined to differentiate into cells that make up a specific tissue. For this reason, adult stem cells are more suitable for treatments aimed at regenerating specific tissues or organs than embryonic stem cells. For example, bone marrow cells are determined to differentiate only into blood cells, and skin stem cells only into skin. Adult stem cells do not have ethical issues because there is no destruction of fertilized eggs, and they are stable in differentiation, so there is no possibility of cancer cells. However, they have a major disadvantage in that they can only differentiate into specific cells, and they are difficult to culture and donate due to immune rejection issues.
Induced pluripotent stem cells are often referred to as IPS cells. These are stem cells that have been reprogrammed into embryonic stem cells-like stem cells using somatic cells, and they have the advantage of being able to use any part of the human body. This technology has great potential not only for the treatment of specific diseases, but also for genetic research and drug development. The work of Japanese scientist Shinya Yamanaka, who was the first to successfully reverse-differentiate and was awarded the Nobel Prize in Physiology or Medicine, is so great that it is not only ethical, but also the most medically viable stem cell.
Stem cells have the highest medical value because they can differentiate into any cell in the body. In particular, there is growing interest in regenerative medicine and personalized treatment, and stem cell technology is emerging as the core of future medicine. And recently, stem cell research and stem cell therapy have become closer to us as they are being used clinically in blood diseases and are being tried in the field of neurology. In addition, experimental research on spinal cord injuries and various types of neurodegenerative diseases is being actively conducted in Korea and abroad.
Although stem cell therapy is currently underway, there is still a long way to go. As the “cure of dreams,” there are still many ethical and technical issues to be resolved before it can be used to treat intractable diseases. In addition, discussions on the commercialization of stem cells are becoming increasingly important along with the establishment of social and legal systems. However, if research on stem cells continues, it is expected that there will be a revolutionary leap forward both scientifically and medically.
