The cells and their function
Stem cells are remarkable for the fact that they can both renew themselves and give rise to a huge range of cell types. Through mitosis (when a single cell divides itself equally in two), a stem cell is able to replicate itself and, when the time is right, differentiate into whatever specialized cell type is needed. This absolute flexibility is necessary to produce complex, multi-cellular organisms such as humans. After all, we start as a single fused sperm and egg cell and end up as a collection of trillions of different cells.
Keeping our origins in mind, it makes sense that stem cells are found inside embryos. These cells, true jacks-of all- trades, are the basis of embryonic development. A little more surprising is the presence of stem cells in various tissues of adults. There, they act as inhouse mechanics, repairing damaged tissues and replacing dying cells.
What exactly, then, is a stem cell? Provided that the cell in question is self renewing and has unlimited potency (the ability to differentiate into any cell type), it can be termed a stem cell.
The history
In light of the ever-growing media coverage over stem cell research, it is interesting to note that they were almost completely ignored when first discovered. This inauspicious start occurred in the 1960s, when Joseph Altman and Gopal Das found evidence that a new type of cell creates neurons during adulthood. At this point in time, it was firmly believed that no new neurons were created after birth.
Fortunately, in 1963, Canadian researchers Dr. Ernest Armstrong Mc- Culloch and Dr. James Edgar Till conclusively proved that stem cells existed. They demonstrated that these cells were capable of self-renewal in the bone marrow of the mice they were studying. Their work directly led to the use of bone marrow transplants to treat diseases such as severe combined immunodeficiency disorder, which the famous “bubble boy” David Vetter suffered from.
With each passing year, researchers uncovered more about the initially mysterious stem cells. Hematopoietic stem cells-the progenitors of all blood cells, including platelets and white blood cells-were uncovered in 1978. Embryonic stem cells were isolated in mice in 1981. A technique to isolate and grow these same cells from a human blastocyst (the ball of cells that develops into the fetus) was developed in 1998 by Dr. James Thomson’s group at the University of Wisconsin-Madison. Embryonic stem cells have been the focus of continued research- and much controversy-ever since. The rate of progress has only increased since these initial findings and shows no signs of stopping, despite some politicians’ efforts to curb certain types of stem cell research.
The controversy
Evoking numerous fundamental bioethical issues, stem cell research may be the most controversial topic in science. Most concerns are focused on human embryonic stem cell research, which requires the destruction of a human embryo or the cloning of cells to create stem cells. Not surprisingly, many pro-life groups denounce the practice, arguing that destroying an embryo is technically abortion, and devalues life because these embryos have the potential to eventually produce a human life.
In 1995, the Clinton administration agreed to federally fund research using leftover embryos from fertility treatments, but declined to fund research that involved the creation of embryos for this research based on moral grounds. In response, Congress created and passed the Dickey Amendment in the same year, prohibiting any federal funding for stem cell research that involved the destruction of embryos, regardless of their source.
After human embryonic stem cells were isolated in 1998, the issue of federal funding had to be re-examined. In August 2001, President Bush announced that this research would receive federal funding for the first time, but only if existing stem cell lines were used. This sidestepped the moral dilemma of destroying more embryos for the sake of research, as funding was given only to projects where “the life-and-death decision has already been made.”
Not content with this limited decision, Senate continued to pressure the president to expand funding for research by allowing the use of excess embryos from fertility treatments. On July 18, 2006, Senate passed the first bill that would allow federal money to be spent on this type of research. Bush vetoed this bill the next day.
Cord-blood-derived, embryonic-like stem cells and a new type of stem cell found in amniotic fluid are the latest developments in this rapidly evolving field of study. Researchers are hoping that these potentially powerful cells can eliminate the use of embryonic stem cells and the accompanying ethical complications.
A Canadian contribution
Recent findings from McMaster University researchers describe how the cells surrounding an embryonic stem cell can affect its function. Termed “niche” cells, they are created by the parent stem cell and, through the use of protein “growth factors,” are able to direct the parent cell’s growth. This new approach to manipulating stem cells that are obtained by working with the cells directly surrounding them, could lead to novel ways of controlling their behaviour and literally “programming” them to become whatever cell type is desired. Clearly, figuring out the mechanism underlying the specialization of stem cells is key to harnessing their restorative power.
The implications
When Korean researcher Hwang Woo- Suk announced that he used unfertilized human oocytes to create embryonic stem cells in 2004, he sparked media frenzies and rampant speculation as to the future of stem cells and medicine. Woo-suk’s results, revealed to be fictitious, were an unpleasant reminder of the lengths that unscrupulous scientists can go to in order to claim a key scientific breakthrough as their own.
The excitement surrounding stem cell research is understandable. If scientists harness the self-renewing abilities of stem cells, diabetics could conceivably be cured with regenerated pancreas cells. Paraplegics could have their spinal cords repaired and perhaps walk again, and cancer could become a simple matter to deal with. A theoretical real-life fountain of youth, stem cells may completely change the way medicine is practiced. So little is known, however, that it is still too early to suggest any possible timelines or exact future scenarios for the application of stem cell research.
Already, stem cells are being used in novel ways. A new procedure using fat taken from a woman’s stomach and adult stem cells enables women to grow new breasts. After the combination is injected into the chest, the stem cells nurture the surrounding fat tissue, allowing it to grow over a period of many months. Seen as a promising treatment for breast cancer patients who have undergone mastectomies, this simple procedure takes only an hour and could become commonplace in a few years.
