Adult Stem Cells
What are Stem Cells?
Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth. In addition, in many tissues they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.
Stem cells are distinguished from other cell types by two important characteristics. First, they are unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity. Second, under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions. In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.
What are Adult Stem Cells?
There are two primary types of stem cells, embryonic and adult stem cells. As the name suggests, the controversial embryonic stem cell are derived from embryos and are often developed from in vitro fertilized eggs, then donated to labs for research and therapy development. A previously overlooked alternative source for therapeutic stem cells resides within our own bodies, known as adult stem cells.
The adult stem cell is an undifferentiated cell that is found in a differentiated tissue. It has the ability to renew itself and become specialized to yield all the cell types of the tissue from which it originated and, in the appropriate environment, can also become a specialized cell of a different tissue. Adult stem cells are capable of self-renewal for the lifetime of the organism.
Sources of adult stem cells have been found in bone marrow, the blood stream, cornea and retina of the eye, the dental pulp of the tooth, liver, skin, gastrointestinal tract, adipose tissue and pancreas. Stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a myriad of diseases, conditions and disabilities. Adult stem cells are relatively quiescent cells, particularly in organisms where cell turnover is low, yet they can mount a rapid and strong response to tissue stress and injury.
As cells designed to withstand crisis and orchestrate repair, stem cells must be especially resilient. Until recently, it had been thought that a stem cell collected from the bone marrow or peripheral blood (a hematopoietic stem cell) could not give rise to cells of a different tissue type, such as nerve cells. A number of clinical studies over recent years have affirmed the phenomenon known as plasticity. Plasticity is the ability of adult stem cells to differentiate to other cell types from a specific cell line. In other words, stem cells, from the bone marrow or from the circulating blood do have the ability to differentiate into other cell types such as heart cells or nerve cells.
Because of this plasticity, your own adult stem cells are the perfect ethical and moral alternative to stem cells derived from other donors or from embryonic stem cells. Adult stem cell transplants (bone marrow transplants) have been used for over 40 years in successfully treating cancers such as leukemia, multiple myeloma and lymphomas and it has now opened the doors of regenerative and reparative therapeutics.
For more information visit the United States National Institutes of Health online resource for stem cell research – http://stemcells.nih.gov/info/basics/