The Science Behind Stem Cells and Stem Cell Research
What is a stem cell?
A stem cell is essentially a type of cell that all other cells in our body arise or “stem” from. There are essentially two major characteristics that make stem cells different from all other cells in the body. The first is that stem cells can divide and thus renew themselves for very long periods of time, both in the body and in vitro (meaning outside to body in culturing plates). The second unique characteristic of stem cells is their ability to develop into specialized cells such has muscle cells, nerve cells, skin cells, or pancreatic cells. Other cells in our body, like the muscle or skin cells, can’t change into say, pancreatic or nerve cells. So, if those cells were ever to get damaged, stem cells would have to specialize and then replace them. (National Institutes of Health 2006, 28-35)
What are the different types of stem cells?
Perhaps you’ve heard some scientific jargon in the past, usually along the lines of “totipotent”, “pluripotent” or “multipotent” stem cells, often in close connection with other terms like “human embryonic stem cells” and “adult stem cells”. Although simple definitions could suffice, it’s better to describe these words in the context of human development, because that’s essentially where stem cells come from. And to understand what all the ethical debates are about, it’s best to understand the origins of stem cells first.
Where do stem cells come from? And what is a “pluripotent embryonic stem cell”?
It all starts with the coupling of a sperm and egg. Usually, for the purpose of research, this is done in vitro. This procedure is often used in fertility treatments (called In Vitro Fertilization or IVF). The fertilized egg, called a zygote, then starts to divide, forming an embryo which at this stage is just a clump of 4-8 early embryonic stem cells (this structure is still often referred to as a zygote). These stem cells are said to be totipotent, meaning they can divide and differentiate into any type of cell in the body and essentially form the entire organism; however, these are not the cells scientists are most interested in. (National Institutes of Health 2009)
After about 5-7 days of development, the embryo becomes a blastocyst, which is a hallow ball of cells. The outside layer of cells forms the placenta. On the inside lies a mass of about 30 stem cells called the inner mass cells, also known as embryonic stem cells. (Bryant and Schwartz 2008) These inner mass cells are said to be pluripotent, meaning they can divide and differentiate into ALMOST any type of cell but not ALL. For example, inner mass cells can develop into other types of stem cells and specific tissue cells of a fetus, but not into a placenta; meaning that these stem cells alone cannot develop into a baby. It’s these inner mass stem cells, that we often hear in the news as “pluripotent human embryonic stem cells” that many scientists are interested in. (National Institutes of Health 2006, 28-35)
In order to isolate these stem cells for research purposes, the scientist will use a microscopic needle to suck the embryonic stem cells out of the blastocyst. These stem cells are then cultivated on special cell culturing plates and can grow indefinitely. This means that one embryo with 30 inner mass cells can produce thousands upon thousands of embryonic stem cells. However, it also means that this embryo will never develop into a human. (National Institutes of Health 2006, 28-35)
Below is a comic that summarizes some of the key points mentioned above.
What are adult stem cells and what does “multipotent” mean?
Now we know that embryonic stem cells are essentially the cells that make up the early embryo and then go on to differentiate into other cells to form the entire human being. So, what are those multipotent adult stem cells all about?
After the blastocyst, or the hallow ball of cells is formed, it can be implanted into the uterus of a woman and continue to grow into a baby, and eventually an adult. Many of the embryonic stem cells would have formed tissues of the body, but some also develop into adult stem cells which reside in specific tissues (such as bone marrow) and give rise to specialized cells that replace old and dying cells. Adult stem cells are said to be multipotent, meaning they can give rise to only a few different types of cells. Sometimes adult stem cells are extracted for use in medical therapies such as bone marrow transplants, as well as research.
So now we know that stem cells are essentially what gives rise to an entire organism, and what replaces cells as they get damaged and grow old. But what good is that in research and medicine?
Below is another diagram that illustrates the relationships between all the different types of stem cells.
What are stem cells used for? Why are they important in science and medicine?
As mentioned before, stem cells are hot topics in scientific research today. The importance of stem cells lies in their amazing potential to become virtually any type of cell in our body. So, if someone has certain cells that don’t function properly or that have been damaged, then stem cells could be used to replace those damaged cells. This is not a new concept. In fact, stem cells have already been used for years in medicine.
Have you ever heard of a bone marrow transplant? Did you know that this therapy for treatment of leukemia is completely dependent on the ability of multipotent adult stem cells to renew themselves and differentiate into white blood cells? When a person has leukemia (a blood related cancer), their white blood cells, called leukocytes, grow abnormally and cannot carry out their usual functions. The patient can’t fight off infection, and the abnormal cells also interfere with the proper functioning of other organs. The idea behind bone marrow transplants is to replace the stem cells that are giving rise to cancerous leukocytes, with ones that will generate healthy leukocytes. In order to do this, chemotherapy is first used to kill off the cancerous leukocytes and then the donor’s bone marrow containing stem cells are introduced to the patient’s blood stream. If all goes well, the stem cells from the donor will migrate to the patient’s bone marrow and begin producing healthy leukocytes. Since this method of treatment has been very successful, scientists have good reason to try to uncover all the untapped information and potential treatments that stem cells could offer. (University of Utah Center 2008)
Currently, scientists are working on developing therapies that may one day be able to treat diseases such as Parkinson’s, cerebral palsy and diabetes. The idea here is to grow compatible tissues in vitro for transplant to replace damaged neurological cells, or pancreatic cells. Another method may be to use drugs to stimulate the body’s stem cells to produce more healthy cells and avoid transplantation altogether. There has been some success already just by injecting patients with stem cells which eventually find their way to the damaged cells. (National Bioethics Advisory Commission 2006)
Scientists are also studying stem cells and focusing in on their mechanisms for differentiation and division. This may be important in future cancer treatments and our overall understanding of cancer in general because cancer cells essentially don’t differentiate or divide normally. Also, many cancers originate from faulty stem cells that give rise to faulty tissue cells. Current treatments focus on the tissue cells, but if scientists can figure out what caused the stem cell to go awry then new therapies and treatments may be developed. (National Bioethics Advisory Commission 2006)
So it seems that stem cells can lead to many medical breakthroughs that can greatly benefit human health. Also, it seems that stem cells are already used in a few effective therapies. So what’s the problem? Isn’t stem cell research a good thing?
The real controversy lies in how embryonic stem cells are obtained for research, and the role of cloning in obtaining those them. We’ve already talked about how scientists obtain embryonic stem cells by removing them from the blastocyst, so before we embark on the journey of ethics, religion and politics, let’s consider one last bit of science to help us better understand the controversy behind stem cells.
Where does cloning come into play and what is its purpose?
Remember how we currently use stem cell therapies like bone marrow transplants, and hope to one day perfect tissue transplant therapies and create better treatments for some cancers? All these therapies depend on the patient’s own DNA/genetic information. For example, in bone marrow transplants today, it is essential that the donor has as close a match as possible to the patient’s own genetic make-up; otherwise, it is likely that the patient will reject the transplant because his immune system will see it as foreign, and this is likely to be fatal. What if instead of searching for a match, doctors and scientists could make specially tailored bone marrow stem cells, and tissues that are genetically identical to the patients? Then there would be no fear of rejection, and a much higher rate of recovery will result.
In order to create these special lines of cells, we need to create clones of the patient’s cells that are being transplanted or studied. This is called therapeutic cloning. Note that the goal here is to clone CELLS not a full living, breathing human being. This isn’t Star Wars! (Nova Science Now 2005)
How do you clone a stem cell? Cloning 101 a.k.a Somatic Cell Nuclear Transfer
Cloning is a tricky business, but the concept is actually easier than most people think. Essentially cloning involves creating an egg that only has the DNA of one individual, and then making that egg divide to create more cells. DNA is held within the nucleus of a cell. So, if we remove the nucleus from an egg of person A, and swap it with a nucleus from a cell in person B, that egg will only have the DNA of person B. And voila! We have a clone (or at least a cloned cell)! This cloning process is also called somatic cell nuclear transfer (SCNT). The cloned egg is then induced to divide, and the inner mass cells are removed from the blastocyst, and cultured in plates. Then if given the right mixture of chemicals, these stem cells can be induced to become, say new pancreatic cells that can be transplanted into a patient with diabetes. Since these cells are exact clones of the patient’s, they are highly unlikely to be rejected. (Sumanas Incorporated 2007)
Even though the purpose of SCNT is to create more cells, it still is still possible to create an entire human being if the egg is implanted. It’s already been done in animals like the famous cloned sheep, Dolly. Now, it is starting to become clearer as to why there’s so much controversy surrounding stem cells, especially embryonic stem cells. While scientists believe that embryonic stem cells hold the most promise for new biomedical technologies and therapies, opponents bring up the many ethical issues surrounding cloning, and the value of an unborn human life. So, with that, on to the debate!
The Ethics of Stem Cell Research
What exactly is the controversy behind stem cell research?
The stem cell controversy essentially surrounds the issues of creating and obtaining embryonic stem cells and their use in therapeutic cloning. The central themes of the stem cell controversy revolve around the beginning and value of life, and the effectiveness and efficiency of embryonic stem cell research and therapies. Similar to the debate over abortion, much of this debate is fought between scientists and pro-life and religious groups. It’s also these debates that shape subsequent political and ethical policies for scientific research all over the world.
Some questions that are asked include whether it is right to create embryos for the purpose of extracting stem cells, or whether it is right or even better to use existing embryos from fertilization treatments to obtain them. Others ask whether cloning is even necessary, and whether the benefits outweigh moral and religious values. Others also ask questions over the cost of stem cell therapies, and who can afford them.
All these debates are multi-dimensional and can become quite complex, and are also very susceptible to one’s own religious, and moral views. As such, the aim in the next few sections is to present the aspects of the debate both in support and in opposition to stem cell research in as non-biased and fact-based form as possible.
What do the supporters of embryonic stem cell research have to say?
When life begins is a huge source of debate on its own. For the supporters of embryonic stem cell research, most believe that at the stage of embryonic development when the stem cells are removed, the embryo is simply not “human”. They are cells, or building blocks, and are no different than a skin or muscle cell. The embryo has not developed a heart, a brain, or any other human characteristics. It is not conscious, or self aware. Also, since the purpose of cloning these stem cells was not to create a new human being, these eggs in the laboratory setting never had the “potential” to become a real human; although some may challenge this argument. As such, many scientists and supporters don’t see it as unethical or as immoral to use existing embryos from IVF treatments or to create embryos for the purpose of obtaining embryonic stem cells since no human life is being destroyed in the process. (Peters 2008)
Some also argue that the “potential” for life is too vague a concept. With cloning techniques essentially all cells in your body have the potential for generating a new life. You can take the nucleus of any cell and insert it into a donor egg. So, when you cut your hair, or clip off a finger nail, you are killing the potential for a new human to be made. Even without cloning, the female ovaries hold thousands of eggs, and in males thousands of sperm die everyday. So when those sperm die, and when not all those eggs are fertilized, has the potential for a new life been destroyed? If we look at potential in this manner, then more potential is destroyed on a daily basis than in any lab. (Peters 2008, and Devoterre 2000)
When it comes to the value of human life and that of a fertilized egg, religious groups say that they value them equally. But, if you were in a burning room with a fridge full of frozen embryos, and your son, who would you save? It’s safe to say that, whether you are Catholic or anything else, you would save your child. So, despite stating that all life is equally valuable, how much do people truly believe in that? A simple test seems to demonstrate that a real human life has far more value than one that has not yet truly begun. (Nova Science Now 2005)
What do the opponents have to say?
This debate is mostly led by religious and pro-life groups; the biggest among them being the Catholic Church. Their primary argument, stemming from the Catholic belief, is that life begins at the moment an egg is fertilized by a sperm, as such that embryo has a right to live. Thus, to create an embryo only to destroy it is both morally and ethically wrong. For many Catholics and pro-life groups, even using extra embryos from fertility treatments is wrong because so long as they are saved, then they can still be used to produce a human being. Also, even if the embryo is not implanted it is still a living human life by Catholic standards, and thus will eventually die; however, this is no reason to kill them prematurely, because it is the same as saying that each and one of us will eventually die and can be rightly killed before then. When it comes to cloning, the simple statement issued by the Vatican is that cloning is just wrong not only because it is like playing God, but also that it again involves creating an embryo only to destroy it. (Correa 2000, and Lewis 2009)
Although some supporters believe that self awareness and consciousness is a defining characteristic of life, and thus an embryo is not yet a human life and expendable, disability activist groups disagree. They believe that saying that is the same as saying that someone in a coma or suffering from some sort of mental handicap is not a human life form and can thus be destroyed. (Healy 2003)
What do the supporters of embryonic stem cell research have to say?
Many scientists believe that creating new embryonic stem cells and using cloning techniques will provide the most knowledge and new therapies. As discussed before, cloning could provide transplant therapies that eliminate the chance of rejection, hence saving many more lives. Also, embryonic stem cells are more promising than adult stem cells not only because they are pluripotent, but also because adult stem cells are more likely to have undergone damage through all the toxins and pollutants that people are exposed to throughout their lives. These damages could cause adult stem cells to behave differently and lead to less effective medical treatments. (Healy 2003)
Scientists also believe that if it’s not right to create and clone embryonic stem cells, then there shouldn’t be as much debate over the use of existing embryos produced from IVF (In Vitro Fertilization) treatments. For each treatment, thousands of embryos could be produced, and only a few are selected for implantation. These embryos that aren’t used are frozen and sit in limbo, and can be considered “dead” since they will never be used in fertility treatments. It would be far more efficient to put these embryos to good use instead of extracting new stem cells from adults. (Peters 2008, and Healy 2003)
What do the opponents have to say?
Although embryonic stem cells and cloning hold a lot of promise for future therapies, there still haven’t been any real effective treatments developed for diseases using them. Scientists also admit that it will be many years into the future before treatments can be developed. However, adult stem cells have already been proven effective, such as in bone marrow transplants. Embryonic stem cell research and cloning is also very expensive, and raise the cost-benefit issue for policy makers. Also, if therapies are developed, they are also likely to cost a lot. Some argue that only the rich will be able to afford the therapies. (Lachmann 2000) In Canada, with our universal health care, will that mean new stem cell therapies will be covered, or will the cost force our system to become more privatized, or will these therapies just not be made available to us at all? Will that in the end be ethical?
One of the biggest arguments to not invest in embryonic stem cell research is that adult stem cell research has already generated so many breakthroughs within the last few years. Most noteworthy was in February of 2009 with the discovery led by Canadian scientists who developed a method of turning normal adult skin cells into pluripotent stem cells (the same type as embryonic stem cells). This has been done before by other scientists using viruses, but the Canadian team developed a method that excluded viruses, which means that the stem cells are more stable and less likely to become cancerous. If this method can be perfected, then there will be no need to create embryos for the purpose of extracting embryonic stem cells at all. (Mount Sinai Hospital News 2009)
Eventually, all the debates, beliefs, facts add up and influence the political as well as scientific policies that guide research today. We’ve all heard a lot about the take on stem cell research in the United States and that at times got quite confusing, but what about in Canada? Our scientists really are paving the way for new discoveries, but how much do we know about the guidelines they must follow, and how they affect us everyday citizens?
Politics and Policy in the US and Canada
In 2001 former President George W. Bush, essentially allowed stem cell research to occur in the US using only “existing cell lines”, or stem cells that were previously extracted from embryos and growing in cultures. He banned research on “new cell lines” which would involve extracting stem cells from new or existing embryos. This proved to be extremely limiting for scientists, because there were very few existing cells lines for them to work with. However, in March of 2009, President Barack Obama revoked the previous executive order, and now American scientists will be allowed to create new cell lines for research, so long as no new embryos are being created solely for the purpose of harvesting stem cells. This means, that embryos from IVF fertility treatments can now be used. (American Association for the Advancement of Science 2009)
What is the overall policy governing Canadian stem cell research?
Up until March 2002, Canada didn’t have any policy governing stem cell research. However, the debate and events in the States eventually led for guidelines to be drafted. According to Updated Guidelines for Human Pluripotent Stem Cell Research, June 29, 2007 written by the Government of Canada’s Canadian Institute of Health Research the guiding principles are as follows quoted directly from the guideline:
Research undertaken should have potential health benefits for Canadians;
Free and informed consent, provided voluntarily and with full disclosure of all information relevant to the consent; (in regards to donating IVF embryos)
Respect for privacy and confidentiality;
No direct or indirect payment for tissues collected for stem cell research and no financial incentives;
No creation of embryos for research purposes;
Respect individual and community notions of human dignity and physical, spiritual and cultural integrity
Canada has always allowed the use of research on new cell lines from donated IVF embryos, so our scientists have been at the cutting edge of stem cell research. But like the US, and almost all other countries except for a select few, embryos cannot be created for research purposes. Meaning, for the time being, scientists and doctors won’t be making specially tailored stem cells to create the “perfect transplant” organ.
What does the change in US policy mean for Canada?
It seems like the US has “caught up” with Canadian policy on stem cells and it’s been cause for much celebration amongst the scientific community. However, a serious issue of “brain drain” is also worrying many within the community. With the current Conservative government in power, it is unclear what type of support the government is promising scientists, making it harder for research labs to hire and retain scientists. However, in the US, there is a definitive promise of more funding and more freedom in research, making it all the more likely Canadian stem cell researchers will move to the US where they can do the same research while getting paid more Why is this reason for any of us ordinary citizens to worry? Put simply, with the economy already the way it is, and with so much promise resting in stem cell research, we want to keep as much talent in Canada as we can. (The Canadian Press 2009)
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