Types and tasks of stem cells
All-rounders with special properties
There are various types of stem cells. They are classified according to three different methods:
- Classification by cell type
- Classification by ontogenetic age
- Classification by differentiation potential
Classification by cell type
The stem cells can be classified according to which cell types or tissue they are precursors for. A blood stem cell e.g. cannot become new bone or a nerve cell.
Hematopoietic stem cells
Another word for hematopoietic stem cells is blood stem cells. These stem cells are responsible for the whole hematopoiesis but have a very limited life span. Every day, about 200 billion of erythrocytes (red blood cells), 120 billion of leucocytes (white blood cells), and 150 billion of thrombocytes (platelets) must be formed in an adult person.
Mesenchymal stem cells
Mesenchymal stem cells are the precursor cells of connective tissue. They develop into bone and cartilage as well as muscles, tendons, and ligaments. They are found particularly in the gel-like part of the umbilical cord tissue – Wharton’s Jelly.
Neuronal stem cells
Neuronal stem cells are destined to become nerve cells, in particular brain cells. They are especially interesting in the research of neurodegenerative diseases like dementia or Parkinson’s, but also traumatic injuries, e.g. after strokes or serious head injuries caused by accidents. The expectation for the future is that neuronal stem cells may trigger repair processes and thus minimize damages.
Classification by ontogenetic age
In biology Ontogenesis is the development of the individual – from the egg cell to the sexually mature organism. The classification by ontogenetic age therefore differentiates between embryonic, fetal, and adult stem cells.
Embryonic stem cells
Embryonic stem cells act in the beginning of human life – long before birth. They are the “mothers of all cells” and can develop into any type of specific cell. However, they exist only for a very short time – namely during the development into the blastocyst, the state of the embryo about three to four days after fertilization. For medical purposes, this means that you would have to grow embryos and destroy them afterwards. Embryonic stem cells are therefore highly controversial from an ethical point of view, and their production is prohibited in the EU.
Adult stem cells
Adult stem cells from the bone marrow and other organs are the reservists of our organism. They create substitutions for dead cells. They are no longer able to differentiate into all types of cells in an organism, like embryonic stem cells, and they are not as viable as stem cells from umbilical cord blood. Furthermore, the extraction of adult stem cells is laborious, risky and expensive.
Neonatal stem cells
Stem cells from umbilical cord blood technically belong to the adult cells, even though they are particularly young and potent. They are therefore their own class –neonatal stem cells.
Collecting umbilical cord blood at birth is the most simple and ethically inoffensive way to extract young and potent stem cells; thus securing them for medical precaution for the child.