The genesis of stem cell research is attributed to Canadian scientists Ernest A. McCulloch, a cellular biologist, and James E. Till, a biophysicist. McCulloch and Till started a series of experiments in the 1960s that involved injecting bone marrow cells into irradiated mice.
What are stem cells?
A stem cell is a primitive type of cell that can be coaxed into developing into most of the 220 types of cells found in the human body (e.g. blood cells, heart cells, brain cells, etc).
Types:
Stem cells are classified by the extent to which they can differentiate into different cell types.
Totipotent stem cells: Produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilised egg cell are also totipotent. These cells can grow into any type of cell without exception.
Pluripotent stem cells: Descendants of totipotent cells and can grow into any cell type except for totipotent stem cells.
Multipotent stem cells: Produce only cells of a closely related family of cells (e.g. blood cells such as red blood cells, white blood cells and platelets).
Unipotent cells: Produce only one cell type, but have the property of self-renewal, which stinguishes them from non-stem cells.
Embryonic and adult stem cells
Stem cells are also categorised as either adult or embryonic, i.e. according to their source.
Embryonic stem cells are derived from four- to five-day-old embryos. At this stage, the embryos are spherical and are known as blastocysts.
Adult stem cells are undifferentiated cells found in small numbers in most adult tissues. They are also found in children and can be extracted from umbilical cord blood.
Thought of as multipotent cells, the primary roles of adult stem cells are to maintain and repair the tissues in which they are found.
Cell therapy
Cell therapy can be defined as a group of new techniques, or technologies, that rely on replacing diseased or dysfunctional cells with healthy, functioning ones. The goal is for the healthy cells to become integrated into the body and begin to function like the patient's own cells.
Bone marrow transplants are an example of cell therapy in which the stem cells in a donor's marrow are used to replace the blood cells of the victims of leukaemia and other cancers.
Cell therapy is also being used in experiments to graft new skin cells to treat serious burn victims, and to grow new corneas for the sight-impaired.
With the use of cell therapies, there may soon be cures for cancer, Parkinson's, diabetes, kidney disease, multiple sclerosis, macular degeneration and a host of other diseases.
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