Stem Cell and Its Types

Adult stem cells are different from cells taken from the embryo and fetus and are found in tissues that develop in humans or animals after birth. However, the best place to obtain these cells is the bone marrow located at the center of certain bones. Bone marrow is usually collected from a bone section called “krista iliaca” behind the upper hip bone. There are different types of stem cells in bone marrow, including hematopoietic stem cells, endothelial stem cells and mesenchymal stem cells.  Endothelial stem cells are known to treat the vascular system (arteries and veins), i.e. they are used in treatments related to veins; endothelial stem cells are known to treat the vascular system (arteries and veins), i.e. they are used in treatments related to veins. Mesenchymal stem cells are known to turn into a hundred different cells on average, including bone, cartilage, muscle, nerve, liver, pancreatic cells.

1) SVF – Stromal Vascular Fraction

When it is understood that stem cells can be obtained from adipose tissue, first, the fat cells are separated by various enzymatic and mechanical processes in order to reach the cells inside the fat, and the complex stem cell suspension that has remaining and many different cells is called SVF. It contains many types of cells found in adults. They accommodate 80-100 different therapeutic stem cell groups, including mesenchymal cells, which are capable of turning into various cells, hematopoietic cells, which form blood cells, endothelial cells, which treat veins, fibroblasts, which form connective tissues. When it’s administered to a patient intravenously (by vascular access), the cells it contains are used as therapeutic cells by the relevant regions. If desired, cells can be separated from the SVF by special methods, reproduced separately and used in different treatments.

Likewise, in burns, diseases of autoimmune system, which require treatment by multiple cells in a collective manner, the cells are used as a whole, without separating them.

2) Mesenchymal Stem Cell

It is the name given to a cell that has the ability to turn into another cell. It is found in adult mesenchymal stem cells and connective tissues. These stem cells can migrate from the tissue it is present in to a damaged tissue. They repair damaged tissues. If damage is detected in any tissue, it can be detected if there is damage in other tissues. The mesenchymal stem cells found in adult individuals are obtained from bone marrow and fat tissue, where such cells are found 4 times more than bone marrow. A mesenchymal stem cell taken from an adult has the ability to transform into about 100 different cells, which are known for now. These are many different cells, including bone, cartilage, muscle, nerve, liver, pancreatic cells.

Characteristics of mesenchymal stem cell:

• Mesenchymal stem cells can be transformed into other cells.
• They differ in appearance in lung, stomach and bone tissue. This is due to different conditions in the environment.
• Mesenchymal Stem Cells have the ability to fuse with damaged cells. Not only do they repair the damage in the tissue where they are present, they also pass to the other tissue in case of any damage in that tissue and repair that tissue.
• They are originating from connective tissues so they can contribute to the development and function of related tissue cells.
• They can differentiate into cells such as muscle, fat, bone, cartilage, tendon, ligament, which are connective tissue cells.

In order to increase their number, they should be reproduced in cultures that last for weeks under special laboratory conditions. This requires a serious technology, infrastructure, experience and it is costly. Therefore, mesenchymal stem cells suitable for clinical use are produced in a limited number of centers worldwide. All procedures required for this procedure must be carried out in accordance with international standards (GMP Good manufacturing practice).

3) Hematopoietic Stem Cell (Blood Cell)

All blood cells  in our body are made up of young (immature) cells called hematopoietic stem cells. (The word hematopoietic means “blood forming.)

Stem cells are usually present in the bone marrow (spongy core in the bones) to divide to form new cells. They are unique cells that were discovered the first, were best described and have been applied successfully in the clinic for years.

Functions of hematopoietic stem cells:

• Carry oxygen to tissues, ensure the functioning of the immune system and control the basic mechanisms such as controlling bleeding.
• They are self-renewing cells that can differentiate and form the entire blood tissue.
• They are used in hematopoietic cancers (leukemia-lymphoma-myeloma), non-hematopoetic cancers,
• Genetic and/or acquired bone marrow diseases such as:
• Aplastic anemia, thalassemia, sickle cell disease, and autoimmune diseases in a progressively frequent manner.

4) Endothelial Stem Cell

Endothelial Stem Cells mature in the bone marrow, circulate, become concentrated in areas of vascular damage (vascular system) and play a vital role in repair of the damage. After leaving the bone marrow, Endothelial Stem Cells can turn into mature endothelial cells, undergoing certain changes in cell surface markers.

Endothelial stem cells multiply and circulate to the extent of their ability to divide and treat the existing vessels.

5) Autologous Stem Cell Production

Autologous stem cell production means reproduction under laboratory conditions of cells in our body which cannot turn into any other cells than themselves and administration of those cells to the incomplete region.

The following are examples of cell types for autologous cell production:

Fibroblast cell:

These are primary cells forming the connective tissue in the lower layer of the skin and collagen producing tissues. Over time, due to the death of these cells, connective tissue begins to collapse and collagen production decreases. In this way, skin aging is seen. In rejuvenation treatments, these cells can be produced in the laboratory and conveyed back to the skin in order to repair incomplete regions in these tissues under the skin.

Beta cell:

These cells play a role in the production of insulin in the pancreas, and they can be used to treat diabetes by reproducing them in the laboratory and placing them back in the pancreas. 

Keratinocytes:

These are the cells that make up the most outer layer of the skin. In epidermal conditions of the outer skin, such as burns, acne scar, injury, etc. which require forming an epidermis, these can be produced in the laboratory.

An embryo that is about 7-8 weeks of age after a development phase is called a “fetus“. When a baby is forming, the cells obtained from the fetus between 8 and 12 weeks have the ability to turn into cells in almost all tissues and organs, even if they do not completely form a human being. These are types of stem cells obtained from infants of women who had a miscarriage between 8 and 12 weeks, which can divide in an unlimited fashion and have the ability renew themselves. Fetal stem cells do not have any antigens. Antigen means a substance which is perceived as a foreign substance by the body’s immune system when it enters the body and which induces production of antibodies for its destruction. A fetal stem cell is not an antigen so when given to another person’s body, that person’s body does not perceive it as a foreign substance and thus the fetal stem cells are completely accepted even if given to another human being. Fetal stem cells thus mimic the cells in the tissues and organs they touch and hence the problematic tissues and organs are treated.

Stem cells are diverse in their ability to differentiate. The cell with the highest ability to differentiate is the zygote, which is the first state where the egg has been fertilized with sperm. The zygote can differentiate into any type of cell the body and any extraembryonic tissue cell. In this way, a human being is born from a single cell. After fertilization, a hollow sphere with approximately 150 cells, called a “blastocyte“, is formed in approximately 5 days. You can recreate a human being using these cells and clone a thousand people. Therefore, studies on embryonic stem cells are prohibited by all countries.

Cord blood stem cells are relatively young compared to other stem cell sources and when they are stored, their aging and wear processes are stopped. Their reproduction rates are higher than those of other sources. The success rate is high even in the absence of a complete tissue match (HLA) between the recipient and the donor during cord blood transplantation.

Cord blood is taken from the part of the umbilical cord remaining on the placenta side, which is cut after birth. Immediately after a baby is born, the umbilical cord is clamped and cut, the infant is taken and the blood inside the cord connected to the placenta is collected into a sterile blood bag containing anticoagulant agent by means of a special system. The collected blood is sent to the cord blood bank laboratory within 48 hours.

The stem cells obtained from cord blood have the ability to be transformed into a current estimate of 200 different cells in the body. However, the mesenchymal stem cells obtained after a baby is born, i.e. from adults can turn into an estimated 100 different cells. Therefore, cord blood obtained from the baby is more successful when used in the treatment of a disease in the long term.