The classification of stem cells by their ability to differentiate:1.Totipotent cells are able to form all embryonic and extra-embryonic cell types. These include only the fertilized oocyte and blastomeres of the 2 — 8 cell stage.
2.Pluripotent cells are capable of forming all types of embryonic cells. These include embryonic stem cells, primary germ cells and embryonic carcinomas.
3.Other types of stem cells are localized in the formed tissues of the adult body (adult stem cells). They vary in their ability to differentiate from multi- to unipotent.
Classification of stem cells according to the source of their allocation:
1.Embryonic stem cells (ESC) — intracellular mass of the early embryo (at the stage of blastocysts 4-7 days of development).
2.Fetal stem cells — embryonic cells on the 9-12th week of development, isolated from abstrative material.
3.Adult stem cells:
— Hematopoietic stem cells (HSCs) are multipotent stem cells that give rise to all blood cells: blood — erythrocytes, B-lymphocytes, T-lymphocytes, neutrophils, basophils, eosinophils, monocytes, macrophages and platelets. Apart from the bone marrow, GCSs are found in the systemic circulation and Skeletal muscles.
— Mesenchymal stem cells are multipotent regional stem cells contained in all mesenchymal tissues (mainly in the bone marrow), capable of differentiation into various types of mesenchymal tissues, as well as into cells of other germ layers.
— Stromal stem cells are the multipotent stem cells of an adult organism that form a bone marrow stroma (supporting hematopoiesis) that have a mesenchymal origin.
— Tissue-specific stem cells — are located in various types of tissues and, first of all, are responsible for updating their cell population, the first to activate if damaged. Have a lower potential than the bone marrow stromal cells.
To date, the following types of tissue-specific stem cells have been detected:
1.Neuronal stem cells in the brain give rise to three basic types of cells: neural cells (neurons) and two groups of non-neuronal cells-astrocytes and oligodendrocytes.
2.Stem cells of the skin — located in the basal layers of the epidermis and near the base of the hair follicles, can give rise to keratocytes, which migrate to the surface of the skin and form a protective layer of the skin.
3.Stem cells of skeletal musculature — are isolated from the transversely striated musculature. They are capable of differentiation into cells of the nervous, cartilaginous, fatty and bone tissues, striated muscle. However, recent studies show that skeletal muscle cells are nothing more than mesenchymal stem cells localized in muscle tissue.
4.Myocardial stem cells — can differentiate into cardiomyocytes and vascular endothelium.
5.Adipose tissue stem cells — found in 2001, conducted since then, additional studies have shown that these cells can transform into other types of tissues, they can grow cells of nerves, muscles, bones, blood vessels, or at least, Cells having the properties of the foregoing.
6.Stromal cells of the spinal cord (mesenchymal stem cells) give rise to different types of cells: bone cells (osteocytes), cartilage cells (chondrocytes), fat cells (adipocytes), and other types of cells of connective tissue.
7.Epithelial stem cells of the digestive tract are located in deep folds of the intestinal membranes and can give rise to different types of cells in the digestive tract.
In addition, at the beginning of last year, American scientists from the University of North Carolina reported that after seven years of research they developed a technology for obtaining stem cells from the amniotic fluid, without harming the actual embryo. Scientists hope in the near future to create from them the tissues and entire organs needed by the patient for transplantation. Their advantage over donor organs is that they can be grown from the cells of the patient himself, and they will not cause rejection. The needs of medicine in the transplant material are almost unlimited. To date, only 10-20 percent of people restore their health due to a successful organ transplant. And 70-80 percent of patients die without treatment while waiting for surgery.
Stem cells in a sense can really become sources of «spare parts» for our body. About the very first experiments with the cultivation of organs can be read here. Already today, studies are under way on the use of stem cells in the treatment of various diseases. Cell therapy is used in cardiology. Work is underway to create methods for the treatment of diabetes, Parkinson’s disease, oncological diseases … The first successes of cell therapy lead to the understanding that everyone should have a stock of their own stem cells for the treatment of various diseases. In the United States, it has long been practiced to take blood from the umbilical cord of a newborn baby and then freeze it. Now services for banking cord blood are offered to Russia. In the future, if this child has any health problems, his frozen stem cells can be thawed, multiplied and sent to the body to restore a certain type of cells.