About Stem Cells

Stem cells are cells from which all other specialized cells are formed. Stem cell research has proven to be a promising, yet controversial, subject area. But what, exactly, are stem cells? What are they used for? And why so much debate?

Stem Cells: A Definition

Stem cells are a group of undifferentiated cells that have the ability to develop into different types of cells. By a process of continual self-renewal (cell division), stem cells are able to replenish other cells and help repair body tissue. When a stem cell divides, it creates two new cells that can either remain as stem cells or specialize into another type of cell, such as a brain cell. A stem cell maintains its population by undergoing long-term self-renewal. No other cell type has the ability to do this.

Stem Cell Sources

Embryonic stem cells–or “pluripotent” stem cells–come from embryos that are about four to five days old. Amniotic fluid also contains stem cells. Adult stem cells, also called “somatic stem cells,” are found in most adult tissues.

Until recently, researchers believed that stem cells in a particular organ or body tissue could only produce cells for that specific organ. Recent studies suggest that adult stem cells in one organ may be versatile enough to produce cells for an entirely different organ.

Stem Cell Research and Potential Applications

The discovery of stem cells’ ability to differentiate into specialized cell types has sparked a torrent of stem cell research. Stem cells have the potential to become a self-renewing source of cells to replace cells damaged by Alzheimer’s disease, cancer, heart disease and innumerable other conditions.

Already, stem cell transplantation is used to treat bone marrow diseases. During a stem cell transplant, the patient’s own (autologous) stem cells–or a donor’s (allogeneic) stem cells–are transplanted into the patient to restore damaged stem cells in the bone marrow.

Why So Much Controversy About Stem Cells?

The controversy about stem cells surrounds the issue of research on embryonic stem cells. Embryonic stem cells are obtained from eggs that were fertilized at in-vitro fertilization clinics, but were never implanted. Extracting stem cells from these embryos destroys them.

Although the embryos are voluntarily donated, embryonic stem cell research raises ethical issues about destroying the embryos. Many researchers prefer using embryonic stem cells because adult cells are more likely to be corrupted by environmental toxins, making them unusable in stem cell research and therapy.

Induced Pluripotent Stem Cells: An Ethical Solution?

In 2006, researchers genetically altered specialized adult cells to reenter an embryonic stem cell-like state. These induced pluripotent stem cells (iPSCs) help solve some of the ethical issues surrounding stem cell research. Induced pluripotent stem cells have already been used successfully in animal studies and drug development research.


Buck Institute for Age Research (2010). Scientists successfully use human induced pluripotent stem cells to treat Parkinson’s in rodents. Retrieved October 11, 2010, from http://www.sciencedaily.com