Stem cells are undifferentiated cells that have the ability to differentiate into specific cells and are characterized by their ability to divide indefinitely. They are categorized into embryonic stem cells, adult stem cells, and reverse differentiated stem cells, and are utilized in various fields such as regenerative medicine and drug development, but embryonic stem cells in particular have caused ethical controversy.
In the modern world, we are exposed to a variety of advertisements, learn about new technologies in the news, and study the term stem cells in school. This is due to the in-depth coverage of stem cells in the current curriculum, but you can also encounter them in various situations in your daily life. You may have heard of them in cosmetic advertisements and medical news. We are constantly bombarded with advertisements that claim to reduce wrinkles by inducing the division of stem cells called “fibroblasts” in the dermis layer of the skin, or that cosmetic ingredients can affect stem cells for long-term cosmetic benefits. In medical news, the ultimate cure for a disease is often discussed. We read about stem cell transplants that have cured diseases such as leukemia and stroke. As you can see, stem cells are very special to us, but at the same time, they can be a bit of a mystery. So, what are stem cells?
A stem cell is defined as an undifferentiated cell that can divide and become a specific cell. In other words, it’s a cell that doesn’t perform a specific function, but can divide and become a cell that performs a specific function. Our body is what it is today because of the division of a single cell called a fertilized egg, which is to say that a single cell called a fertilized egg divides and divides to become a single entity. In this way, division is the most important characteristic of a cell. Unlike normal cells, stem cells can increase their own division limit (Hayflick Limit), meaning they can divide indefinitely.
Stem cells are not the only cells that can divide indefinitely. Cancer cells, for example, can divide indefinitely. Cervical cancer cells from a woman named Henrietta Lacks were collected in 1951 and are still dividing in the lab. So what’s the difference between cancer cells and stem cells? While both are the same in that they divide endlessly, cancer cells do not differentiate, but instead continue to multiply as a mass of their own. This ever-growing mass eventually robs the surrounding cells of oxygen and nutrients, causing the destruction of the surrounding tissue. Stem cells, on the other hand, divide only when they receive a signal from the cell to divide, and once they divide, they tend to differentiate into a predetermined cell type: skin, stomach lining, sperm, or any other part of the body.
There are three main types of stem cells that are important in the body. They are embryonic stem cells, adult stem cells, and pluripotent stem cells. Of these, adult stem cells were the first to be studied. In 1956, E. Donal Thomas, an American internist, discovered that bone marrow injected into a living body produces new blood cells, which earned him the Nobel Prize in Physiology or Medicine in 1990. Then, in November 1998, James Thompson of the University of Wisconsin and John Gearhart of Johns Hopkins University became the first scientists in the world to isolate stem cells from embryos and differentiate them into other tissues. Reverse differentiation of stem cells is a relatively recent development. In 2006, Professor Shinya Yamanaka of Kyoto University in Japan introduced several genes into the skin fibroblasts of mice to create pluripotent stem cells like embryonic stem cells, and the following year, he introduced genes into adult skin cells to create reverse-differentiated stem cells.
Embryonic stem cells are cells that can be obtained from the embryonic stage of a fertilized egg. The fertilized egg divides and divides to enter a stage called the blastocyst. Inside the blastocyst, undifferentiated cells clump together, and these cells are embryonic stem cells. Embryonic stem cells are at the highest level of totipotent stem cells, which are capable of differentiating into any cell except the placenta. However, the fertilized egg after embryonic stem cell harvesting is discarded because it cannot develop into a normal individual. For this reason, the ethical debate around embryonic stem cells is still ongoing. Opponents argue that embryonic stem cells are obtained by destroying a fertilized egg, thus taking one life to save another. Another type of embryonic stem cell is cloned embryonic stem cells, which are created by implanting the nucleus of one’s own somatic cell into an enucleated egg. This has the advantage over fertilized egg embryonic stem cells that there is no immune rejection when organs made from stem cells are transplanted. However, cloned embryonic stem cells have another objection in that the fertilized egg must be further cultured and implanted in the uterus, which can lead to human cloning. Also, the current technology has a low success rate of successfully differentiating the stem cells into the desired cells, so more lives must be destroyed.
The second is adult stem cells. During the blastocyst stage, embryonic stem cells differentiate into different parts of the body and most of them disappear. However, some of them remain in each part of the body and continue to produce cells. They can be found under the skin, in the intestinal membrane, in the hippocampus, in the bone marrow, and more. However, unlike embryonic stem cells, adult stem cells are multipotent, meaning they have a limited number of cells that can differentiate into different types of cells. The problem with culturing them in the lab is that most of them differentiate quickly, so you can’t get enough stem cells. They are also difficult to obtain due to the small sample size and the location of the stem cells deep within the body. However, adult stem cells have the advantage of not being immunologically rejected because they use their own cells, and there are no ethical issues.
Lastly, Induced Pluripotent Stem Cells (IPSCs) are stem cells created by human power. All of the body’s cells have the same genetic information because they all came from a single fertilized egg. Stem cells made by reverse differentiation of these cells back to their pre-differentiation state are called reverse differentiated stem cells. In addition to the Sox2 gene, which maintains pluripotency, and the c-Myc gene, which promotes cell proliferation and transformation, genes such as Oct-4 and Klf4 are introduced into the somatic cells to return them to their pre-differentiation state. They are called “dream cells” because they have the pluripotency of embryonic stem cells in that they are made from their own somatic cells, but they are not ethically problematic. However, they are still in the experimental stage, and the success rate of reverse differentiation is not perfect. Even if the reverse differentiation is stabilized, it still needs to be studied whether it will differentiate into the desired cells in the body or whether it will continue to divide and become a cancerous mass.
By studying and utilizing stem cells, many things are possible. One of the main purposes of stem cell research is organ transplantation. When organs are irreparably damaged due to age or trauma, they need to be transplanted from another person to continue living. However, the supply is too low compared to the demand and there’s also the issue of compatibility. This is where stem cells come in, as they can be used to create healthy organs. Transplanting tissue units rather than organs can be used to treat muscle atrophy, Parkinson’s disease, nerve damage, and even autologous bone marrow transplants. In addition, stem cells can be used to quickly test the effects and risks of new drugs by differentiating stem cells into various tissues, and cancer stem cells can be used to test the effects of anticancer drugs. The infinite number of divisions of stem cells can also be used to effectively treat heart disease, which requires constant management.
We’ve learned what stem cells are, how they differ from other cells, their history, types of stem cells, and how they can be used. Stem cells are likely to be at the center of the future of medicine. For example, combining stem cells with gene editing technology could be used to treat rare diseases or enable personalized organ regeneration. These technological advances could lead to lower healthcare costs and more personalized treatments for patients. Despite the promise of stem cells, they are still very much under-researched and under-utilized, which is why it’s important to be selective and analyze information about stem cells in everyday products rather than accepting it blindly.
The use of stem cells will become increasingly important in a variety of fields. Researchers are expecting amazing results in regenerative medicine, drug development, gene therapy, and more using stem cells. Furthermore, advances in stem cell technology will improve our quality of life and open up the possibility of curing incurable diseases. For these reasons, stem cell research will continue to attract attention in the future, and we need to continue to support its potential.
