A stem cell is able to divide and replicate itself almost indefinitely and can be grown to produce a more specialized or differentiated cell. Some stem cells are already differentiated or specialized and can be grown to produce only specific specialized cells. Other stem cells are more specialized or differentiated and can be grown into a wide range of specific cell types. These are called multi-potent or pluripotent cells. The third type of stem cells is called totipotent. These are completely undifferentiated and can be grown into any cell type.

SOURCES OF STEM CELLS

Multipotent cells can be found in adult blood, adult bone marrow, and umbilical blood. They can also be derived from cancer tissues and from fetal cells and embryonic cells (either pre-implantation or post-implantation).

Embryonic stem cells are totipotent. They are able to develop into any type of body cell or tissue. The nucleus of the stem cell can be removed and can be replaced by the nucleus of a patient who has a damaged tissue. The cell can grow into the desired tissue. Embryonic stem cells are more efficient than adult stem cells.

DISEASES LIKELY TO BE TREATED USING EMBRYONIC STEM CELLS

The following serious medical conditions are candidates for cure using stem cells: diabetes, stroke, spinal cord injury, and neurodegenerative disorders such as Parkinson's disease. Stem cells could be grafted at a site of spinal cord injury. Stem cells grafted in the pancreas could produce insulin that is deficient or lacking in diabetics.

ADVANTAGES OF STEM CELLS

Stem cells have two main advantages. They can be a source of tissue or organs thus helping overcome the shortage of organs for transplantation. Stem cells generated under the patient’s own genetic control will be fully immunologically compatible unlike donated organs that can be rejected by the patient.

ETHICAL CONTROVERSY ABOUT EMBRYONIC STEM CELLS

The use of adult stem cells or cells from the umbilical cord raises few ethical controversies. Embryonic stem cells, unlike adult stem cells, are a source of ethical controversy because they are obtained from embryonic tissue, either pre-implantation or post-implantation. Use of such tissue involves violation of the purpose of preserving life. Since the cell is a potential human life its use in research or transplantation involves denial of that life.