Since its beginning in the mid-1800’s, the science of stem cell research has been debated over. Some say that stem cell research goes against human morals – that scientists are attempting to “play God”. Others see this research as the future of the human race, as it has the greatest potential of any treatment to cure and prevent diseases and defects that were previously untreatable (or at best delayed). For example, neural cells in the brain or spinal cord can be replaced with stem cells. In cancer patients, cells that are destroyed by radiation or chemotherapy can be replaced with healthy stem cells that adapt to whatever area they are applied to, whether it be the lungs, heart, brain, liver, or wherever else they are needed.
First of all, what are stem cells? Stem cells are cells that have the ability to renew themselves through mitosis and can differentiate into many different specialized cells. There are two categories of stem cells, embryonic and somatic (adult). Embryonic cells are the main source of controversy within stem cell research, as they require destroying an embryo to obtain. Those who believe in the sanctity of life from conception liken this to murder – destroying a human life. Advocates of stem cell research argue that the embryo has no human features, and that stem cell lines already exist due to the practice of in vitro fertilization. They also make it very clear that no embryo will be created for the purpose for experimentation.
Embryonic cells are harvested from a single embryo before the cells in it begin to differentiate themselves. When the cells are taken at this time, they can be grown in cultures where they double every 2-3 days. This makes it less likely that more embryos will be destroyed, since the existing ones always continue to grow. Because these cells are the precursor to all specialized tissue in an embryo, they can be administered to prevent birth defects or genetic anomalies that would have otherwise been untreatable. However, those who are against stem cell research point out that about twenty percent of mice treated with embryonic stem cells for Parkinson’s disease died as a result of brain tumors. It seems that embryonic stem cells (when stored for long periods of time) can create the type of chromosomal anomalies that have been known to cause cancer. These same people also point out that funding this branch of stem cell research takes away funding from the other two branches, which are more promising and less controversial.
Somatic stem cells are different from embryonic stem cells in that instead of preventing diseases, they aid in the regrowth of tissue, replenishing specialized cells instead of becoming them. These cells can be taken from bone marrow, as bone marrow is rich in stem cells. However, some painful destruction of the bone marrow results from this. These cells can be taken out without damage to bones, but the process takes more time. Because these cells are from the patient’s own body, they are many times superior to embryonic or cord cells because the immune system never rejects them.
Umbilical stem cells are the next most abundant source of stem cells. As with the adult cells, the umbilical cells can provide a perfect match to the body as long as the family has planned ahead. Umbilical cells can be frozen in cell banks as a type of future insurance for the infant. These cells can also be used for the child’s mother, father, or nearly any relation. However, the more distant the relation, the more likely it is that the cells will be rejected. Thankfully, there are many different cell types – just as there are blood types – and with numerous donors, matching is always possible. Also, scientists now have found ways to increase transferability of these stem cells and reduce risk of rejection, so matching is even easier.
Stem cells all have varied differentiation potential. For example, some cells (known as totipotent cells) that are the result of the fusion between an egg and a sperm can differentiate into virtually any type of cell. This makes these cells especially remarkable. Another type of cell is the pluripotent cell, a close relative of the totipotent cell. All embryonic cells are pluripotent and can give rise to any of the tissues found in adults (when given the right stimulation). These cells can (for the most part) differentiate into cells from the three germ layers of the body (ectoderm, endoderm, and mesoderm). Multipotent stem cells can only differentiate into specific subtypes of cells. And example of this is the hematopoietic cell, which can only become a blood cell type. The final classification of stem cells is the unipotent cell, which can only differentiate into one type of cell but retains its ability to renew itself.
Recently, some scientists are making extraordinary advancements that are rendering some of these stem cells unnecessary. For example, in June 2006 Shinya Yamanaka of Japan described a study in which he mixed skin cells from a mouse in with “genetic cocktails” made from different combinations of 30 genes known to be important to development. The human body contains two-hundred and twenty different cell types, each one with a different combination of dormant genes in it that are associated with pluripotency. When the right four genes were compiled and inserted into the cells aboard retroviruses, the cells’ pluripotency was restored, returning them to an embryo-like state without ever creating an embryo. However, there was no way to tell whether or not the foreign DNA would affect development later in the cells, or even potentially cause cancer. One year later, he managed to transform human skin cells as well. Later on, other scientists experimented with different combinations of genes. This made the cells safer, but much less effective. These cells that were created are known as induced pluripotent stem cells (iPS cells). And because the process is so simple, college students can study stem cells that they create themselves. Now, scientists from both Scotland and Canada have teamed up to create a new method of creating iPS cells, one that is safer and more effective than the original method. A reporter from ScienceNOW Daily News writes:
“The work involves using an engineered chunk of DNA instead of a virus to introduce factors into a cell that will turn on genes needed for pluripotency. Nagy explains that the team used ‘mobile DNA elements’ called transposons that jump from one place to another in the chromosome. Although fragments of DNA called plasmids have been tried for the same purpose, Nagy says this is the first time a nonviral method has worked with human cells. What’s more, he says, the team ‘took advantage of the other property’ of the system, which was that it could be mobilized via an enzyme, transposase, to effect the “seamless removal” of the foreign DNA without disrupting the newly gained pluripotency. So far, the teams have removed the genes in only mouse cells, but they soon expect to show it can also be done with human ones.”
Another example is Douglas Melton, the co-director of the Harvard Stem Cell Institute, who discovered a way to simply transform one type of cell into another in August of 2008. This process allows stem cells to be bypassed altogether. Melton managed to transform a mouse pancreatic cell that does not produce insulin into one that does. If this were applied to humans sometime in the future, it could be the cure (or at least a more effective treatment) for diabetes. Even more recently, President Barack Obama demolished the restraints on stem cell research that were put in place during the Bush administration. This allows more scientists to have government-funded research on a wider range of stem cells than what was previously allowed. Some people disagree with this policy, but President Obama has made it clear that he believes that the government had forced upon us “a false choice between sound science and moral values”. He has also made it clear that no human embryos will be cloned or created for the sole purpose of research.
As you can see, stem cell research is the source for many promising opportunities in the fields of both science and medicine. While some may look down upon it, dismissing it as an act of religious defiance, many more accept that the future of mankind may lie in the smallest parts of our very own bodies. Those who support this field of science are behind it wholeheartedly – refusing to let any lack of funding or pressure from society stand in their way. As Bruce Barrett of the American Diabetes Association puts it, “we will continue to oppose any measure that will stand in the way of progress of potentially lifesaving research.”
