Stem cell research
|It doesn't stop at the water's edge:|
|Random strands and actors|
Stem cell research proposes to use stem cells to repair or replace damaged tissues in order to treat an extremely wide range of conditions, including severed spinal cords, non-functioning endocrine glands, diabetes, cancer, heart disease, various types of brain damage, and many other conditions.
This article predominantly looks at the social side of the issue, rather than detailing current scientific research or scientific discussions.
 What are stem cells?
Most cells in the human body are considered to be "differentiated", or specialized at one task. For instance, red corpuscles are specialized in oxygen delivery, astrocytes in delivering nutrients to neurons, osteoclasts in dissolving bone, et cetera. The value of stem cells comes from the two properties which define them. First, they exhibit self-renewal (they can divide repeatedly into more stem cells). Second, they exhibit potency, which is the ability to differentiate into any of a wide range of different tissues. Potency is measured on a scale:
- Totipotency - Ability to become any type of human tissue, including extraembryonic tissues like the placenta
- Pluripotency - Ability to become any type of tissue found in an adult human
- Multipotency - Ability to become any one of many, but not all, types of tissues found in an adult human
- Unipotency - Ability to become only one type of cell found in an adult human (your own)
- (There could be a possible fifth level, "nullopotency", where the cell cannot reproduce, e.g. osteoblasts and red corpuscles)
There are two kinds of stem cell: adult stem cells and embryonic stem cells. Adult stem cells are usually only multipotent or even unipotent, whereas some embryonic stem cells are pluripotent.
 Examples of research
It is hoped that stem cells can provide cures for many illnesses as well as loss of body tissue from things like traumatic burns.
Much of the primary research is focused on attempting to revert normal adult stem cells into embryonic stem cells, since this would also allow a much greater range of treatments using one's own cells and potentially negate the need to take immunosuppressants for life. It also has the side benefit of avoiding the Religious right's whining and moaning.
The use of adult stem cells has made its way into (experimental) clinical practice, for a number of therapies. With the exception of bone marrow transplantation in cancer patients, only stem cells harvested from the patient's own body are used -- not for political or ethical reasons, but because grafts of ones own cells have almost no chance of organ rejection.
In 2012, Yamanaka and Gurdon won the Nobel Prize in Medicine for discovering a way to turn ordinary skin cells into stem cells. Depending on how functional these "manufactured" stem cells are, when compared with normal adult stem cells or embryonic stem cells, many new avenues of research may have been opened up.
The use of human embryonic stem cells has evoked ethical concerns from pro-lifers, because blastocyst-stage embryos are destroyed in the process of obtaining the stem cells. The embryos from which stem cells have been obtained are produced through in-vitro fertilization. Those who consider pre-implantation human embryos to be human beings generally consider such work to be morally wrong, because they assert that human life begins at the moment that an egg cell has become fertilized. Therefore, those who oppose embryonic stem cell research believe that the extraction of embryonic stem cells violates the sanctity of life and is tantamount to murder.
Others may accept the use of human embryonic stem cells because:
- They may not regard the blastocysts to be human persons with right to life.
- More than a third of zygotes do not implant after conception. Thus, far more embryos are lost due to chance than are proposed to be used for embryonic stem cell research or treatments.
- It is known that none of the cells of the inner cell mass are exclusively destined to become part of the embryo itself — all of the cells contribute some or all of their cell offspring to the placenta, which has not been accorded any special legal status.
- In vitro fertilization generates large numbers of unused embryos. Many of these thousands of embryos are slated for destruction. Using them for scientific research utilizes a resource that would otherwise be wasted.
The divergence of views on this issue is illustrated by the fact that the use of human embryonic stem cells is allowed in some countries and prohibited in others. In USA, during the Bush years, funding for new lines of embryonic stem cell research was banned, but research continued on the less promising adult stem cells.
 See also
- Embryonic stem cells reverse Parkinson's in monkeys
- Steven Pinker, The Stupidity of Dignity, a rebuttal to advocates of "theocon" bioethics such as Leon Kass