Stem cells are undifferentiated cells that are not only capable of turning into specialized, specific cell types, but of also dividing for the purpose of producing more stem cells. There is a significant amount of interest in stem cells because they are the only cells in the body that have the natural ability to generate new cell types. We take a look at everything you should know about these "wonder" cells.
Where do stem cells come from?
There are two main types of stem cells: embryonic and adult.
Embryonic stem cells are taken from a human embryo in the blastocyst phase. The embryo is about four or five days old in this phase and has around 150 cells. Embryos that are used for stem cells are commonly created in IVF (in vitro fertilization) clinics. While many cells are created during the IVF process, only one is necessary for impregnating a woman. Therefore, the ones remaining are donated for research purposes with consent of the donors.
Embryonic stem cells are known as pluripotent cells, which means that they can divide into more stem cells or become a specific type of cell found in the body. With such adaptability, embryonic stem cells can potentially regenerate or repair damaged tissue and organs.
Also called somatic stem cells, adult stem cells are present throughout the body and are found in various types of tissue following embryonic development. The specific tissues tissue include the brain, bone marrow, blood, skin, fat, and liver. They are dormant and remain so until triggered by disease or injury done to the tissue. Once active, adult cells can divide and self-repair indefinitely.
Adult cells were once thought to be more limited than embryonic cells. Researchers believed that adult cells were only be able to differentiate depending on the tissue they were originally found in. However, current research suggests this may be false. Studies have shown that adult stem cells are indeed able to become a cell type unrelated to their organ of origin. For example, adult stem cells taken from bone marrow may have the potential to generate heart muscle cells.
What issues are associated with stem cells?
Ethical concerns have been raised over the use of stem cells, specifically embryonic stem cells. Issue is taken with the fact that the process hinders embryonic development beyond the blastocyst phase. A minority of religious individuals argue that this hindrance is akin to the taking of a human life. Despite this belief being far from mainstream, extremely vocal fringe Christian organizations have managed to create controversy where there was none.
Due to the controversy, the National Institutes of Health made research guidelines in 2009 about the collection of stem cells. The guidelines specifically discuss the use of embryonic stem cells in research and donation. They state that only embryos that are both produced by in vitro fertilization and no longer necessary for that purpose are eligible for donation. Additionally, donors cannot be compensated monetarily.
Though research for adult stem cells is promising and doesn't pose as many ethical issues, embryonic cells are preferred because they are more adaptable and durable. Additionally, due to environmental toxins, adult cells are at a greater risk for abnormalities.