Our organs and tissues originate from stem cells, and the study of embryonic and adult stem cells plays an important role in the treatment of various diseases and regenerative medicine.
All of our organs and tissues are made from clumps of stem cells that divide in a fertilized egg. Stem cells are distinct from the hundreds of millions of cells in our body because they can divide to make more of the same stem cells, and they can differentiate into different types of cells, such as skin, muscle, and blood. Studying the differentiation potential of stem cells can lead to breakthroughs in disease treatment. As a result, stem cell research is being conducted around the world.
There are two main types of stem cells that can be obtained from mammals They are embryonic stem cells, which are obtained from embryos, and adult stem cells, which are obtained from adult tissues.
Embryonic stem cells come from embryos that are just a few days old after fertilization, or blastocysts, one of the earliest stages of development. The fertilized egg, which results from the union of a sperm and an egg, undergoes a series of divisions, from one to two, four, eight, or 16, and after four to five days, it reaches the stage of a mass of cells called a blastocyst. This mass of cells divides into an inner and outer layer, with the outer layer becoming the placenta and the inner layer becoming the embryo. Embryonic stem cells are the cells located on the inside of the blastocyst. Just as a newborn baby has infinite possibilities, these cells have the potential to differentiate into any cell or even an individual, which is called totipotent and pluripotent.
In adults, there are progenitor cells that work to repair the body when something goes wrong. They are at rest and when damage occurs, they migrate to the site and differentiate into the damaged tissue. Adult stem cells are obtained from these. So far, the body tissues from which adult stem cells have been found to be obtained include the brain, bone marrow, blood, blood vessels, skeletal muscle, skin, and liver. However, liver cells are only present in a very small percentage of the body’s tissues, so the number of stem cells available is small. Also, because adult stem cells have already differentiated to some extent, the extent to which they can differentiate into different cell types is limited compared to embryonic stem cells.
Embryonic stem cells can multiply in large numbers and can be transplanted into other people and other species without immune rejection when used in patients. However, their differentiation is difficult to control, and they can become cancerous, which requires careful study.
Adult stem cells are limited compared to embryonic stem cells in that fewer stem cells can be obtained and there is less scope for differentiation into different cell types. There is also the added problem of immune rejection when receiving stem cells from another person.
The greatest value of stem cells is the ability to obtain large quantities of cells or tissues to replace damaged tissue, which can be used to treat incurable diseases. Parkinson’s disease, a degenerative brain disorder, is caused by the death of dopamine-producing nerve cells, and the most effective treatment is transplantation of fetal brain tissue. However, fetal brain tissue is very limited and raises many ethical and social issues. If a method is developed to induce the differentiation of dopaminergic neurons from stem cells, it will be possible to obtain large quantities of dopaminergic neurons and transplant them into Parkinson’s disease patients, and if large quantities of insulin-secreting β cells are obtained, it will be possible to treat type 1 diabetes patients who rely on insulin injections. In addition, the value of regenerative medicine, a dream that could reshape the entire global medical market, which is currently around 120, is increasing vertically. Currently, stem cells are being used to treat strokes, regenerate knee arthritis, and more.
The ethical issue with embryonic stem cell research is that it requires the use of blastocysts, which means destroying embryos. While embryos are not yet fetuses, there is an ongoing debate about whether using embryos that can develop into fetuses for research is taking human life. This is why some countries have banned or allowed embryonic stem cell research. European countries such as Sweden, Finland, Greece, the United Kingdom, the Netherlands, South Korea, Japan, India, and Iran allow embryonic stem cell research, while Germany, Austria, Ireland, Italy, New Zealand, and most countries in South America and Africa prohibit it by law. Adult stem cells, on the other hand, are obtained from adults and do not face the same ethical debate.
One of the most amazing discoveries of the last decade is iPS cells. Adult stem cells are called iPS cells because they have undergone special modifications that make them pluripotent, like embryonic stem cells. This opens up the possibility of generating pluripotent cells from patients to treat incurable diseases such as Huntington’s chorea and chronic conditions such as autoimmune diseases without immune rejection.
As Nancy Reagan once said, “Stem cell research is the hope that we will finally have the answers we’ve been looking for, the answers we’ve been waiting to hear.” Stem cells are a revolutionary topic in the treatment of human disease. However, we are still in the early stages of research where stem cells can be used. While many cancer patients have been cured thanks to bone marrow stem cell transplants, it’s safe to say that we haven’t even begun to scratch the surface in other disease areas. Vigorous research will lead to a much deeper understanding of stem cells, and clinical trials will focus on alleviating or curing the symptoms of disease. There is much more to be accomplished in stem cell research than what has been discovered so far.
