Stem cells are a special class of undifferentiated cells that, due to their ability to specialize, give rise to all types of cells. Depending on the origin, stem cells are divided into two types – embryonic and adult. Both types of cells are characterized by the ability and potential to differentiate (specialize) into different types of cells, for example, cells of the skin, muscles, bones, etc.
Adult or somatic stem cells have passed the period of embryonic development and are found in different types of tissues throughout the human body. They have been identified in bone marrow, blood, skeletal muscle, skin, brain, blood vessels, and liver. Adult stem cells may not divide and remain dormant for many years until they are activated by disease or tissue damage. It is also worth noting that the process of self-renewal and division can continue indefinitely. This allows them to form a number of cells from the original organ, or even restore it entirely. It used to be thought that adult stem cells can only specialize on the basis of which tissue or organ they come from. But in the light of recent research, this statement is already controversial.
Embryonic stem cells are usually obtained from a 4- or 5-day-old embryo at the blastocyst stage. The blastocyst is the stage of embryonic development during which the internal cell mass (embryoblast) is formed. It is this cell mass that will subsequently be the source for the emergence of embryonic stem cells.
Stem cells can also be classified according to their differentiation potential:
totipotent – can specialize in all types of cells, these include the zygote, which is formed during fertilization, and the first few cells that have arisen as a result of its division;
For scientists, the study of stem cells is of great interest largely due to the fact that if stem cells are removed at the stage of embryonic development, then later they can be induced to develop any required type of cells. This, in turn, means that stem cells have enough power to fully reproduce damaged body tissues under the right conditions.
Thus, already in 2013, according to American scientists from the Massachusetts General Hospital, USA, they were able to create blood vessels in a mouse using human pluripotent stem cells. According to doctors, the regeneration of blood vessels can help treat people who have problems with the cardiovascular system. In addition, replacement of tissues and cells with stem cells can be used to treat brain pathologies such as Parkinson’s and Alzheimer’s disease. It is also worth noting that adult hematopoietic stem cells (from bone marrow and blood) can be used to treat various types of cancer.