Stem cells and induced pluripotent stem cells (iPS cells) are playing an important role in regenerative medicine and the development of personalized therapies due to their ability to differentiate into a variety of cells. With ethical and supply issues addressed, iPS cell technology is revolutionizing tissue engineering, drug discovery, regenerative medicine, and more, opening up new possibilities for personalized medicine.
Our bodies are made up of more than 60 trillion cells. Some cells, like heart cells, live for more than 80 years before they die. But most cells, like blood cells, don’t live that long and die quickly. Red blood cells, which give blood its red color, only live for four months once they’re made. If the red blood cells responsible for oxygenation are dead and gone, how can the cells in your body be oxygenated?
The answer lies in stem cells. Stem cells are undifferentiated cells that have not undergone a process called differentiation, which is when they divide into cells specialized for each tissue. They can divide into different types of cells when the body needs new cells. This ability to divide in response to the body’s needs distinguishes stem cells from cancer cells, which are constantly dividing. Stem cells maintain homeostasis and regenerative capacity, and play an important role in the repair of damaged tissue and the generation of new cells. For example, hematopoietic stem cells, a type of stem cell, can make all the cells needed in the blood, including red blood cells specialized to carry oxygen, and white blood cells and lymphocytes responsible for immunity. This allows the number of red blood cells in the blood to be maintained so that they can carry oxygen.
Scientists have applied the ability of stem cells to divide into different cell types to tissue engineering. The idea of using stem cells from normal people to create new skin tissue, hearts, and transplant them to patients in need has fascinated the medical community. When tissue made from other people’s cells is transplanted, immune rejection occurs when the body does not accept the transplanted tissue because it is different from its own cells. The body becomes inflamed, like a thorn in the side, and the transplant fails. Even if it succeeds, you may have to take immunosuppressive drugs for the rest of your life. Fortunately, immune rejection can be overcome by using the patient’s own stem cells. This has made stem cells an important keyword in tissue engineering.
However, stem cells in the adult body are limited in number and cannot differentiate into a single organ. Therefore, embryonic stem cells, which can make any organ, must be used, but they have the same problems as adult stem cells. The most important obstacles are the ethical issue of whether an embryo is considered a fetus, and the supply issue of where to get embryos when the number of eggs is limited. This problem, which cannot be solved forever, has prevented tissue engineers from conducting active research.
In 2006, Shinya Yamanaka, a professor at Kyoto University in Japan, found the perfect way to solve this problem: his research showed that embryos turn off four specific genes when they divide, limiting the abilities they don’t need in an individual. During development, the fertilized egg is set up so that no single cell can differentiate into all of them, spreading its abilities across multiple cell types and creating a generalized somatic cell that is completely unable to divide. Of course, only DNA in the fertilized egg can do this. Dr. Yamanaka turned the four genes of the normal somatic cell back on in reverse, returning it to its original state as an embryonic stem cell. The resulting cells are called Induced Pluripotent Stem Cells (iPS Cells). Since iPS cells use abundant somatic cells, they can solve the ethical and supply problems of embryonic stem cells once and for all.
Prof. Shinya Yamanaka was awarded the Nobel Prize in Physiology or Medicine in 2012 for his work. He was originally an orthopedic surgeon. However, he became a researcher when he realized that current medical technology was unable to treat incurable diseases such as congenital heart disease. The technology he developed opened up the possibility of tissue engineering. The ethical issues that have been a social issue have been resolved, but most importantly, the supply of experimental materials has been solved. If we can differentiate stem cells into the desired cells, we can create personalized cellular therapies to treat diseases caused by cellular abnormalities or develop new drugs that respond only to those cells. Tailored treatments using stem cells are expected to usher in a new era of personalized medicine. Unfortunately, we don’t know how to differentiate them into the cells we want, so we have to do a lot of experiments to figure it out, and that requires a lot of stem cells.
Personalized cellular therapies can be tested for safety and can radically treat a patient’s disease. For example, Parkinson’s disease is caused by the death of dopamine neurons in the midbrain. Current drug treatments are only temporary and not a cure. On the other hand, if stem cells are differentiated into dopaminergic neurons and transplanted, Parkinson’s disease can be cured. It took a lot of stem cells to get to this cell therapy, which is currently in monkey trials.
Stem cells can be used for disease research and drug development. Until now, researchers have had to use animal cells to develop new drugs, but after solving the supply problem with iPS cells, they can now test directly on human cells. The probability of success in the clinical stage is low if experiments are conducted on animal cells, so drug development has been time-consuming and expensive. However, if you reverse differentiate human cells with a disease, you can create stem cells with the same disease. If you test these cells, you can screen for drugs that have therapeutic effects and increase the chances of success in the clinical stage.
Stem cell technology is also opening up new possibilities in regenerative medicine beyond simple therapies. For example, research is underway to regenerate damaged spinal cord nerves or repair cartilage damaged by degenerative arthritis. This approach to regenerative medicine could offer new hope for many patients with incurable diseases.
The introduction of iPS cells to tissue engineering has revitalized many fields of research and opened the door to tissue engineering, which has been slowed by social issues and stem cell shortages. Research results using iPS cells have been published in the hallowed pages of Nature. Soon, there will be cellular therapies made from iPS cells that will be personalized to the patient, and eventually, patients who need heart or kidney transplants will be able to receive organs that will not cause immune rejection. These advances are important steps toward realizing the future of healthcare we dream of.
