Stem cells are defined as cells that carry self-renewal and proliferative properties that do not carry a specific tissue character, protect undifferentiated phenotypes until appropriate signal is received.
One of the biggest goals of human beings since its existence has been finding solutions to diseases and prolonging the life span. There is information that the mixture obtained from many different plants was used for treatment thousands of years ago. It is known that various illnesses and treatments are told in a papyrus thought to belong to B.C. 1534. The desire of human beings to reach conscious sublimation has been the driving force of medical science to this day.
Especially in the last 20 to 30 years, tissue engineering has progressed all over the world and it has come to the point of being able to produce tissues of human stem cells and even 3-D organs in the laboratory environment. By removing of one’s own cell, the production of cells (autologues), tissues or and the application of the cell to himself again self can cure many diseases for which the pharmaceutical industry is insufficient, and it can connect the patient to life.
The stem cells, which have the ability to renew themselves and transform into different cells, are divided into 3 types according to their division and differentiation characteristics.
As we know, for mammals, life starts from a single cell called zygote (sperm egg fertilization). This cell is a totipotent cell and carries all the functions that are required for an adult organism to come into existence. A totipotent cell can alone create a living creature. This will last for 4 days without fertilization. Totipotent cells are not used in human treatment due to ethical reasons.
By embryonic stem cell is meant the pluripotent cells from the inner cell mass of the blastocyst. These cells have the ability to differentiate into three embryonic germ layers. Three germ layers constitute more than 220 cell types in an adult. Some differentiated pluripotent cells may be present as multipotent cells in adults (eg, bone marrow), but their ability to differentiate is limited. One of the most important issues in regenerative medicine is embryonic stem cell research because of their ability to renew themselves unlimitedly and having plasticity (ability to transform into different cell types).
Adult stem cells are more likely to turn into organ or tissue from where they are obtained and they are called multipotent stem cells. Multipotent stem cells are undifferentiated cells found in differentiated tissues in adults which have the ability to regenerate dead or damaged cells. They are also called somatic stem cells. They are found in tissues such as bone marrow, muscle, eye, nerve, liver and skin. They have the ability to divide and regenerate themselves. In adults, there is not the same number and potential stem cells in each organ and tissue. For example, in the brain these cells are found in quite a few numbers. As a result, there is no organ regeneration like a bone or tissue in the brain damage, the damage is usually permanent and has serious consequences. Multipotent stem cells constitute the stem cell group used in the treatment field.
- Hematopoietic stem cells (HSC): Hematopoietic stem cells are the precursors of all blood cells. Myeloid cells (monocytes, macrophages, basophils, eosinophils, erythrocytes, megakaryocytes / platelets and some dendritic cells) and lymphocytes (T-cells, B cells, NK-cells) are terminal cells formed by differentiation of hematopoietic cells. Hematopoietic stem cells are found in the bone marrow, thighs, buttocks, chest, ribs and other bones in adults. The cells can be taken from the hip bone by direct syringe, with the aid of some drugs (cytokine) can be obtained from the blood. Today, hematopoietic stem cells are the stem cells that are often referred to as bone marrow transplants in leukemia patients.
- Mesenchymal Stem Cells (MSC): Mesenchymal stem cells are stem cells that are found in the adipose tissue, in the bone marrow, in the cord blood. And they have very high renewal, differentiation and tissue repair capacities.
- Adipose Tissue Root Cells (SVF): Adipose tissue stem cells (ASC) are generally isolated from human fat tissue by the lipoaspirate method. Thanks to many features, it resembles mesenchymal stem cells (MSC) found in bone marrow. Their isolation is less painful than stem cell derived from bone marrow. It has been shown that human adipocyte stem cells can differentiate into bone, cartilage, fat and muscle cells in the laboratory environment and it is possible that they can differentiate into neurons in the future by the development of applications.