Stem Cells: Structure, Function & Diseases

Stem cells are considered the precursors of somatic cells and can divide almost endlessly. A wide variety of cell types develop from them.

What are stem cells?

A stem cell is a body cell that does not yet have a function in the organism. For this reason, they have the ability to develop into a wide variety of cell types (e.g., nerve cells, heart cells, blood cells). Stem cells are thus pluripotent and therefore play a special role in regenerative medicine. One can also say that they are a form of the cell of origin, since a stem cell can multiply indefinitely. This form of cell is subdivided into embryonic and adult stem cells.

Anatomy and structure

As the name suggests, embryonic stem cells occur only at the developmental stage of an embryo. They are not yet specialized, which is why they are called totipotent. This means that a complete organism can develop from one cell. Adult stem cells, on the other hand, are cells that are found in the human body after birth. Compared to embryonic stem cells, they are only multipotent and form only certain types of cells. Adult stem cells include cells found in the human bone marrow, where they replicate the vital blood cells. Stem cells have also been identified in the liver. Here, they ensure that the dead cells are replaced in the event of damage. Probably the best-known repair function in which cells are involved is the healing of the skin after superficial abrasions. In principle, no complete organism can develop from adult stem cells. Specific cell types can be grown from stem cells in the laboratory using nutrient solutions.

Function and tasks

Stem cells have the ability to form so-called daughter cells. These also possess the characteristics of a stem cell. This is made possible by asymmetric cell division, which, however, has not yet been fully elucidated by science. Which cells stem cells ultimately develop into depends on the biological area in which they are found. Stem cells play a particularly important role in hematopoiesis. They give rise to red and white blood cells and platelets in several steps. They thus contribute to the renewal, repair and growth of the structures of the human body. Stem cells are used primarily in the treatment of diseases. They ensure that damaged or lost tissue can be replaced or restored. They have been used in the treatment of certain diseases for 40 years. Treatment with the help of stem cells helps not only to fight the symptoms of certain diseases, but also to regenerate the damage in the body in the long run. By law, embryonic stem cells may neither be obtained nor used in Germany, as embryos must be destroyed for this purpose. Stem cell research is also only possible if very strict conditions are met. By means of certain procedures (e.g. bone marrow puncture in the case of bone marrow donation) the adult stem cells can be obtained. However, this procedure is painful for the patient and also involves risks. For some years now, it has also been possible to obtain stem cells from the blood of the umbilical cord directly after delivery. Since they are exactly between embryonic and adult stem cells in their development, they bring with them some positive characteristics. For the newborn child, the collection is painless and without risks. The use of stem cells from umbilical cord blood is now steadily increasing worldwide. Many parents want to freeze stem cells from umbilical cord blood for their child or anonymously.

Diseases

Probably the best known disease of the so-called hematopoietic stem cells is leukemia. The lifespan of blood cells is limited, which is why the body has to keep producing them. If a genetic change now occurs in the corresponding stem cells, then more and more non-functioning white blood cells enter the bloodstream, displacing the normal components of the blood. This leads to a shortage of red blood cells, which are responsible for transporting oxygen.Anemia develops, which then leads to oxygen deficiency in the organism. In leukemia, there are too few hemostatic platelets. The tendency to bleed increases, and since functional white blood cells are missing, the susceptibility to infections increases. Medicine distinguishes between acute and chronic leukemia. Neither type of this disease can be prevented. Adult hematopoietic stem cells are used in the treatment of leukemia, and they also help the damaged bone marrow to regenerate after chemotherapy or radiation. In connection with the topic of stem cells, the Stem Cell Act should also be mentioned. Its purpose is to protect unborn life. It contains regulations that make it possible to conduct research on embryonic stem cells in Germany. In order to obtain embryonic stem cells, it is necessary to kill cloned embryos or embryos created by artificial insemination. This procedure is prohibited in Germany by the Embryo Protection Act. Under certain conditions, however, it is possible for embryonic stem cells from aborted fetuses to be imported for research purposes. The fulfillment of the conditions of the strict requirements of the Stem Cell Act are examined and evaluated by the “Central Ethics Committee”. The Robert Koch Institute (RKI for short) is the responsible approval authority. Only with its approval can embryonic stem cells be imported from abroad.

Typical and common diseases of the blood and erythrocytes.