Stem-cell research
When it comes to the news about stem cells, it can be hard to distinguish fact from fiction. The media regularly carry stories touting stem cells as cures for everything from baldness to cancer. Is it just hype or real hope?
The enormous scientific and clinical interest in stem cells is well founded. These special cells can develop into many different cell types in the body. When a stem cell divides, each daughter cell can either remain a stem cell or become another type of cell—a blood cell perhaps, or a brain cell or a muscle cell. Because of this versatility, stem cells may be a source of replacement cells for treating diseases and disabilities such as Parkinson's, Alzheimer's, spinal cord injury, stroke, and many more.
The key word is potential, notes Heritage Scholar Dr. David Hansen. "There's a great deal that we don't understand about stem cells—and this understanding is crucial for realizing the therapeutic potential of stem cells."
In his laboratory at the University of Calgary, Dr. Hansen studies the delicate balance that must be maintained between proliferation (the simple self-renewal of cells) and differentiation (where dividing cells turn into different types of cells) in order for stem cells to function properly, and for an organism to develop properly and remain healthy. Too much proliferation can lead to the formation of tumours; too little proliferation will reduce the stem-cell population to the point where it is unable to form an adequate number of specialized cells.
Dr. Hansen is one of many researchers around the world who are attempting to identify the genes involved in regulating this balance. The organism he studies is C. elegans, a tiny roundworm—about one millimetre in length—that lives in the soil. He focuses on germline stem cells—a very small proportion of germ cells that are capable of either self renewing or differentiating into sperm and eggs.
Although many genes have been identified, how they actually work together to control the balance between stem-cell proliferation and differentiation is still very much a mystery. "One gene produces proteins that turn on another gene in a kind of cascade that we call a signalling pathway," explains Dr. Hansen. "For the C. elegans germ line, one of these pathways—the Notch signalling pathway—is a major regulator of the decision to proliferate or differentiate. But only in one particular location or niche."
Dr. Hansen's team investigates some of the genes involved in maintaining this niche. When stem cells are in this niche, they remain stem cells. If they leave the niche, they differentiate. The determining factor is the presence of signalling molecules, which are produced by neighbouring niche cells. "So it's a case of other cells telling the stem cells what to do," says Dr. Hansen. "There is still a lot of work to do to figure out how all the components work together.
"The idea behind the research is to try to determine how this works in relatively simple organisms like worms or fruit flies, and then apply that information to more complex organisms like humans. My work, and that of other scientists, adds incrementally to the knowledge about stem cells. It may seem slow to an outsider, but there's real excitement in our lab. We've been able to gain fundamental insights into how an organism develops and how life is controlled. It's these insights that increase our understanding of stem-cell behaviour in general and will eventually be applicable to human health."