Patient, Heal Thyself
Harnessing the regenerative power of stem cells. When you think of stem cells, do you think of embryos? Stem cell-related breakthroughs that make the news often focus on embryonic stem cells and prompt a maelstrom of ethical concerns about the morality of using human embryos as a stem cell source. Stem cells don’t just come from embryos, though. In fact, each of us, even as an adult, has stem cells — in our stomach and fingernails and even our hair follicles.
What is it about stem cells that has scientists so excited? For starters, they are potentially life-saving and are already used to treat debilitating illness. Also, many experts believe that stem cells hold great promise for new cell-based therapies that put the cells to work repairing organs, and believe that research might provide important medical clues related to birth defects and diseases such as cancer and diabetes.
Embrace your inner stem cells
Stem cells provide the foundation for everything in our body; every organ and tissue originates from a stem cell. Although we hear a lot about embryonic stem cells, there are lots of other types of stem cells, says Patricia A. Ernst, Ph.D., assistant professor, Department of Genetics and Microbiology and Immunology at Dartmouth Medical School, and Norris Cotton Cancer Center member at Dartmouth-Hitchcock Medical Center in Hanover.
Some stem cells are a blank slate and could develop into any organ, tissue or body part, while others have more limited potential, Ernst says. For instance, whereas embryonic stem cells can contribute to anything in the body, tissue stem cells are dedicated only to regenerating tissues such as “skin, gut lining, hair and fingernails, which turn over a lot, along with the entire blood-forming system, which is constantly being made and destroyed,” she says. All stem cells have regenerative abilities, with one stem cell capable of becoming multiple stem cells ad infinitum.
In terms of treatment, stem cells could hold the key to promising new therapies. We’ve all heard stories of patients agonizingly waiting for a donor organ to replace their failing lung or heart or kidney. Stem cell-based therapy would enable doctors to use cells, possibly a patient’s own, to mend damaged tissue. Much work remains to be done, but it appears that scientists can direct certain types of stem cells, with their unlimited replenishing ability, to become specific cell types, to nudge them into becoming heart tissue, for example, or brain tissue or spinal cord cells. The healthy cells could be transplanted into patients and get to work, replacing cells that are damaged or lost due to injury or disease.
Where do they come from?
Unfortunately, along with exciting stem cell applications that include treatments for Parkinson’s disease, diabetes, traumatic spinal cord injury, heart disease and vision and hearing loss, the thorny question of stem cell harvesting arises. Those troubled by the idea of using embryonic stem cells might take heart in knowing that doctors are already taking advantage of other stem cell sources, including adult patients.
For example, bone marrow transplants — the most common, current stem cell treatment, Ernst says — can use a patient’s own bone marrow for treatment. Bone marrow and umbilical cord blood are often used to treat blood disorders including leukemia and lymphoma, Ernst says, when doctors need to treat a patient’s existing lymphonic system. Using a patient’s own blood or cells can be beneficial because it helps avoid immune system rejection problems between donor and host, but patients might lack the kind of cells necessary to treat a particular problem.
On the horizon
This is what makes embryonic stem cells especially appealing: their versatility, their ability to become anything. But getting them from embryos leads to difficult ethical issues as people weigh the benefits of therapeutically using embryonic cells against the morality of destroying embryos to obtain the stem cells. The good news is, there’s another kind of cell in the works that circumvents all the controversy, Ernst says.
Induced pluripotent cells or “iPS” cells involve converting just about any kind of dispensable cell that exists within a patient to an embryonic-like stem cell, one that is capable of becoming any kind of tissue, Ernst says. Theoretically this means that iPS cells could aid heart repair for heart disease patients or brain repair for someone with brain damage. iPS technology is currently in a research phase, “but it’s going to be really important,” Ernst says. Not only would iPS cells offer some of the benefits of embryonic stem cells minus the ethical problems, they would avoid the complications of mismatched donor cells and potential donor-host rejection problems, because each of us could supply our own stem cells if needed, Ernst says. NH
Out of the Mouths of BabesCalling all tooth fairies! There’s gold in them thar hills, or at least stem cells in those baby teeth. Ethical concerns sparked by the harvesting of stem cells from human embryos, along with a 2003 discovery by a scientist who was curious about what was inside his daughter’s baby teeth, have led to one of the newer frontiers in stem cell therapy: harvesting stem cells from baby teeth pulp.
Stem cells from baby teeth pulp do not have all of the same regenerative properties as embryonic stem cells, and no one is currently using baby teeth stem cells therapeutically, but potential medical uses are being actively researched, says Scott F. Bobbitt, D.M.D., M.A.G.D. of Nashua.
Stem cells are found in adult teeth but are less plentiful than they are in children, Bobbitt says. The number of stem cells a person has decreases dramatically with age, so that, as far as stem cell population is concerned, even a 35- or 40-year-old patient is “kind of over the hill, dentally,” he says.
Dentists such as Bobbitt who offer stem cell extraction services send baby teeth to a lab, where the stem cells are harvested and stored for an annual fee. Parents of kids who need to have teeth extracted for orthodontic treatments especially might want to consider collecting their child’s stem cells, Bobbitt says, since the teeth have to come out anyway.
Some parents view banking a child’s baby teeth stem cells for a possible future medical emergency as a type of insurance. But some medical experts scoff at the idea, saying that the technology that would enable doctors to use baby teeth stem cells therapeutically does not yet exist, and that the cells have limited value. Baby teeth stem cells greatly reduce the risk of graft versus host rejection that can occur during transplants, however, and can be more easily used than other types of cells to target specific conditions, Bobbitt says.
Ultimately, the decision to bank stem cells “becomes an issue of risk tolerance,” Bobbitt says. “If you think that your family is healthy and everybody lives to be 95 or more and they die of old age in a car accident, then the chance that you’re going to need something health-wise is pretty slim. But then there’s the rest of us ... These are things that patients have to weigh on their own.”