Human embryonic stem cells are a relatively new field of research. The first human stem cell was isolated for experiments by Dr. James Thomson from the University of Wisconsin in 1998. A ban on federal funding for research involving fetal stem cells further stymied research possibilities for many years until former President Bush allowed some of the frozen stem cell lines to be used for research, rather than discarded. Then President Obama lifted the federal ban entirely. As a result, human stem cell research is still in its early stages, but human clinical trials are expected to begin this summer.
There are three classes of human embryonic stem cells. A fertilized egg is “totipotent,” which means that it can give rise to any type of cell in the body. A “pluripotent” stem cell can become any type of cell in the body (except for those required to develop a fetus). “Multipotent” cells can give rise to a small number of other cell types. These fetal stem cells are usually taken from embryos and used to create “stem cell lines,” which can be grown forever in a laboratory setting. While most stem cells come from young embryos that are just 3 to 5 days old, some pluripotent stem cell lines may be derived from fetal tissue that is beyond 8 weeks old.
There are several traits that make human embryonic stem cells preferable for stem cell therapies. For one, these early developmental cells are a blank canvas. These cells have no particular tendency to become anything specific but may be encouraged to become one of 200+ cell types. Additionally, fetal stem cells can remain in this protean, undifferentiated state for long periods of time and may divide or self-renew indefinitely. Therefore, it’s easier to create mass quantities of embryonic stem cells for use in adult stem cell research.
Even though research using human embryonic stem cells was limited to select states that passed ballot initiatives, underground, privately-funded scientists have been working diligently since 1998 to find ways to use not just fetal stem cells but also adult human stem cells. It was previously believed that embryonic stem cells were versatile, able to become any of 200+ cell types and that adult stem cells were confined to only replicating more specialized cells of a similar nature. In late 2007, scientists found a way to reprogram adult stem cells to behave like embryonic stem cells that will form a number of other tissues, rather than just the tissue it was derived from. More studies are needed to determine whether these manipulated cells are safe for use in humans, but the findings are significant.
Tags: adult stem cell research, fetal stem cells, human embryonic stem cells, human stem cells, stem cell therapies