There is hot debate about stem cell use, their ethics and potential for curing diseases. Although promising, the application to disease states should not be overblown. We may all feel bad for Christopher Reeve, but injecting him with stem cells is simply not going to make him miraculously walk. Some cold water needs to be thrown on the loudest proponents, since common sense dictates that all advancements in science don’t always happen out of sheer will and hope. Like all medical experiments, we ask the question: will it work and is it safe, and this applies equally to stem cells.
Stem cells are regarded as the ideal resource for tissue regeneration, outside of formal organ transplantation. Stem cells have the following properties: they self-renew, they can form any cell type in the body and they can multiply into clonal populations.
There are many sources of stem cells:
Adult stem cells exist in adult tissues throughout the body, such as bone marrow, brain, muscle and GI tract. Research with these cells has progressed slowly because they are difficult to maintain in culture. Their advantage is that they will not provoke an immune response such as rejection.
Embryonic stem cells are obtained from the inner cells of the blastocyst, an early stage in human embryonic development formed five days after fertilization of the egg by the sperm. The ethical and political controversy dates back to 1998, when human embryonic stem cells were first isolated from donated human embryos. Although they can differentiate into any cell type (except placenta), their growth is not well-controlled, and can provoke an immune reaction.
Amniotic fluid and placental stem cells can be obtained from amniotic fluid, can self-renew and can differentiate into all types of cells. They are less-studied but have properties between adult and embryonic stem cells, and importantly, unlike embryonic stem cells, they do not form teratomas, a type of tumor.
Stem cells for urinary incontinence is a potentially exciting application. The external sphincter can become weak and allow urine to leak past it with coughing, sneezing, laughing and exercise. Age, menopause and childbirth are common risk factors for stress incontinence.
Several groups in the U.S. and Germany have performed animal studies showing improvement in sphincter function. There are small series of human trials showing some improvement as well. Upper arm muscle biopsies from female patients are taken, and the muscle cells and connective tissue cells are grown in culture and then injected into the urethra of the same women. One early study showed a 60 percent cure rate and a 28 percent improvement rate. Another small series of eight patients showed some modest improvement at 12 months after injection, and several needed repeat injections.
Onset of improvement was between three and eight months after the injections were performed. Despite these early modest findings, stem cells are a promising avenue for medical treatment if/when some of the ethical considerations are settled.