Stem cells are primary cells that can self-repair by division, and differentiate into many specialized cell types. Depending on the source of origin, there are two types: embryonic and adult stem cells.
Embryonic stem cells originate from epiblast tissue (blastocyst cell mass). A blastocyst is an early embryo (approximately 5-day-old human embryo) that contains 50 to 150 cells. Embryonic stem cells can be transformed into any adult organism cell (there are more than 200).
Embryonic stem cells have two distinctive properties:
Pluripotency is the main feature that distinguishes embryonic stem cells from adult stem cells.
Adult stem cells are undifferentiated cells spread throughout the body. They multiply and replace dead cells, repairing damaged body tissue. Adult stem cells are produced in small amounts. They are often in the process of differentiation, which greatly narrows the possibilities of their use. Unlike pluripotent embryonic stem cells, adult cells are multipotent. This means that adult stem cells can only generate a limited number of cell types.
The potential of propagating indefinitely makes embryonic stem cells useful for continuous research and clinical use. Embryonic stem cells are effective for tissue replacement treatment for a number of injuries and diseases.
Adult stem cells are also used in regenerative medicine, although they are considered slightly less effective. Patients who decide to use their own adult stem cells, however, have a considerable advantage. These cells will not be rejected after transplantation since it is the biological material of the organism.
Also, adult stem cell research does not raise ethical issues the way embryonic stem cell research does; obtaining adult stem cells is not associated with the destruction of an embryo. In the majority of countries, significant amounts are allocated to adult stem cell research, as embryonic stem cell research is banned in most cases.
Cord blood stem cells are a lesser-known type of stem cell. They are the least differentiated adult organism cell and can be used to treat a wide range of diseases, as they feature the greatest repair potential.