Embryonic Stem Cell Formation
In the cleavage phase after fertilization, the zygote reproduces by dividing by a series of mitoses . Each daughter cell formed as a result of division is called a blastomere. These embryonic cells, called blastomeres, get smaller with each cleavage division, and no blastomere has a distinctive feature and superiority until the 8 blastomere stage. Each blastomere is totipotent. These puppies have the ability to develop into anything from bone tissue to the placental wall. Just as "thing" is used in a sentence, "totipotent" is the same for organism.
Then, on the 3rd day, the 12-16 blastomere morula period comes. The embryo, which reaches approximately 107 cells on the 5th day after the morula period, begins to differentiate into two different cell types. Shortly after the morula enters the uterus, a fluid-filled cavity called the blastosis cavity (blastocele) is observed. This fluid from the uterus passes through the zona pellucida and fills the cavity. As fluid increases within the blastocyst, it divides the blastomeres into two parts, the embryoblast (embryonic inner cell mass) and the trophoblast (extraembryonic outer cell mass). Here, every cell taken from the embryoblast is pluripotent and is directed to differentiate into three germ layers (ectoderm, endoderm, mesoderm) in the future.
Induced Stem Cell Production
Adult stem cells have limited differentiation potential compared to embryonic stem cells. For this reason, studies are carried out with induced stem cells (iPSCs). Induced stem cells arise as a result of reprogramming of somatic cells induced by specific factors to the pluripotent stage. Body somatic cells can be transformed into pluripotent cells using 3 main methods:
- somatic nuclear transfer method,
- somatic cell fusion method,
- reprogramming method.
Induced pluripotent stem cells are seen as an alternative to embryonic stem cells (ESCs); because iPSCs produced from somatic cells have the same characteristics as embryonic stem cells.
Adult stem cells are non-specialized stem cells found among cells in the tissue or organ of the living organism. There are many sources of stem cells:
- Mesenchymal stem cells, hematopoietic stem cells and stem cells found in organs are adult stem cells .
- Bone marrow stem cells, peripheral blood stem cells and cord blood stem cells are hematopoietic stem cells.
- Fetal stem cells and cadaver stem cells are non-embryonic stem cells.
Some of the tissues from which stem cells are obtained; It has been reported as heart, brain, kidney, skin, eye, gastrointestinal tract, liver, lung, pancreas, breast, ovary, prostate and testicles . [7]
Advantages of Modern Stem Cell Techniques Like iPSC
Compared to alternative methods, induced pluripotent stem cells; There are strengths such as being productive in reprogramming, low risk of genomic integration, low genomic disruption, and minimal risk of disruption. iPSCs are a good resource for therapeutic use.
One of the most important advantages of adult stem cells is that personalized treatment can be applied and stem cells can be collected from the patient himself. For this reason, stem cell therapy does not cause unwanted immune responses. Providing an unlimited source of autologous differentiated cells, iPSCs provide clinical advantage in the case of tissue rejection . For example, in vitro differentiation of iPSCs produced from spinal muscular atrophy (SMA) patients revealed progressive motor neuron loss, which may indicate the developmental loss of motor neurons seen during this disease. These studies provide clues that disease modeling using iPSC technology may actually be applicable.
However, iPSCs represent an optimal autologous cellular model for the study and treatment of individual diseases. The personalized approach is based on the idea that individuals react differently in disease states. This approach analyzes personal clinical, genetic and environmental information, optimizing medical care and outcomes for disease detection, prevention and treatment.
Use of Human Stem Cells
Human stem cells can be used for multiple purposes in molecular biology and clinical fields. Its importance for molecular biology is its potential to shed light on developmental biology. With the help of human stem cells, critical points in the embryonic development stage can be revealed and complex pathways can be resolved.
Now scientists can turn genes on and off and observe which ones play a critical role in the development of the human embryo. Likewise, it can be revealed which genes are important in cell transport during development. Investigation of all these points and potential problems also leads to clinical research. For example, by examining the cell cycles of stem cells, it can be understood how some types of cancer develop. The biggest benefit of understanding this is the idea of being able to fight cancer cells by controlling their cell cycles.
Stem cells are the longest living and permanent cells in the tissues where they are found, but with the aging of the organism, these cells gradually decrease and they age and die after a certain mitosis division. Stem cells can form clones , and with this ability, much more new stem cells can be created from a single stem cell.
After serious diseases in organs such as the brain, liver and heart, which have important functions in the body, it is not possible to regenerate these organs naturally. There are studies on the treatment of diseases in these organs by taking advantage of the regeneration and reproduction abilities of stem cells. He conducts stem cell studies for the treatment of many diseases such as nervous system diseases, spinal cord injuries, heart muscle regeneration, orthopedic defects, rheumatism, diabetes, and can replace organ transplantation.
With genetic reprogramming in humans; dermal fibroblast, liver, peripheral blood cells, pancreatic cells, keratinocyte , urinary epithelial cell, B and T cells, gastric epithelial cells, mesenchymal cells, neural stem cells, cord blood cells, progenitor blood cells were obtained.
Another advantage of using stem cells is that the drugs produced can be tested on the tissue formed by the stem cells. Again, to give an example on cancer, a drug produced specifically for a certain cancer type can be tested on cancerous tissues created with the help of stem cells, and thus, whether the drug is safe and effective on targeted cancer cells can be tested without using animals.
However, perhaps the most important use of human stem cells is to provide the development of "cell-based therapy" method. As you know, organ transplants do not always give successful results. In these cases, cell-based therapies can be used. Taking advantage of the specialization features of embryonic stem cells for each cell type, scientists are able to produce the necessary tissues and organs. Although successful many times over, this exciting therapy is still in the process of development.
By conducting laboratory studies on stem cells; It is aimed to develop new drugs, to determine the causes of birth defects and to develop disease model systems. However, thanks to stem cell studies, the regeneration mechanisms and repair processes of cells in the human body have been clarified. It has been seen that human disease models can be developed under laboratory conditions for basic toxicology and cancer studies.
Misconceptions About Stem Cells
Unfortunately, erroneous information about stem cells also causes various misconceptions about stem cells to spread among the public. Let's take a look at some of them.
In one case, the parents of a congenitally blind 2-year-old girl spent nearly $50,000 to have her admitted to a clinic in China, where stem cells from a donated umbilical cord were transplanted to their daughter.
After the treatment, the family was initially convinced that their daughter's vision had improved, but an objective determination by an ophthalmologist revealed that their daughter still could not see. This story; It is one of many sad stories that emerge as a result of deceptive information about new technologies that are not yet fully mature. Stem cell therapies are an application that has been on the agenda for years, just like in blood cancer treatments, for only very limited applications. Although it continues to be emphasized that embryonic stem cells are very effective in stem cell therapies, it also brings ethical discussions.
Stem cells; Although they are undifferentiated cells, they also have the capacity to transform into specific cell types. Embryonic stem cells are the cells with the highest differentiation capacity and can transform into any body cell. Studies with stem cells; It gives hope for how to control the differentiation processes of stem cells, which may be useful for treatment.
Possible applications that are expected to result in the regeneration of heart muscle cells, beating and strengthening of the heart with the injection of stem cells into the heart in heart failures are already ongoing. As experiments are still ongoing, it may be premature to use stem cells for such treatments at this stage. Similar experimental studies are underway, such as stem cell treatments to the damaged brain or spinal cord. Stem cells can also be applied as support cells, not as replacement cells.
Genetically engineered stem cells can primarily be made into drug delivery systems or support cells so that damaged cells can live and function longer. But there are major obstacles in this regard. Because there is a possibility that stem cells can turn into cancer cells. One of the reasons; our body does not consist of stem cells with unlimited self-renewal capacity. Stem cells share some characteristics with cancer cells and injected stem cells are most likely to become cancerous.
Stem cells have enormous potential and will likely play an increasingly important role in medical therapies over the next 20 years. But the truth is; There is a lot of exaggerated and only theoretical information about stem cells, and it is not possible to reach that level already. This situation is suitable for the case of abuse.
Stem cell clinics continue to be established mostly in poor countries such as China and India and in different parts of South America. They are mainly there to lure western wealthy people for therapeutic purposes. The price can go from 10 thousand to 100 thousand dollars. Once you start investing in stem cell therapy, you put in a lot of effort both financially and morally. These families believe in and invest heavily in treatment despite the evidence that the treatment doesn't work very well.