By: Dean A. Lee, M.D., Ph.D., assistant professor, Department of Pediatrics, Cell Therapy Section
Why all the fuss?
You can hardly be alive and breathing and not be aware of the ethical and political struggles the world has endured over stem cells for the past several years. In a world that's already jaded to the exposure the media gives to new advances in medical science, stem cell research has become the poster child for what the hyperbole of Washington and Hollywood can do to (for?) science.
Last week, the Washington Post reported the release of new federal rules governing which embryonic stem cells could be used for research, and the week prior U.S. News & World Report ran an article discussing the promise of stem cells. Three weeks ago, My Sister's Keeper was released in theaters, a cinematic adaptation of Jodi Picoult's best-selling novel about the potential legal and ethical conflicts of stem cell donors.
In spite of all the recent discussion on this subject, there's still much confusion about the different kinds of stem cells, the procedures available, and the issues surrounding stem cell therapies.
What is a stem cell?
The great majority of cells in our body have one very specialized function: they make hair, or sweat, or they twitch, or they make insulin, or they absorb nutrients, etc. They dutifully perform these tasks until they die. Somewhere in nearly every organ, though, is a cell that makes replacements for these cells that die, and occasionally, also makes a replacement for itself. Something like a beehive, where almost all of the bees on the colony are specialized as drones or workers, but somewhere deep in the hive is a queen making more of them. And, every so often, the queen is able to make another queen. That ability to reproduce itself is the hallmark of a stem cell.
Cells in our body generally become more and more specialized until they become fully functional mature cells. This is a process called differentiation, and this process typically moves in only one direction. That is, once a cell has gained a specific function, it usually can't go back to being a less-specialized cell. This is why embryonic stem cells are usually described as having so much potential -- because they can, under the right circumstances, become anything. They are, coming from an embryo, the least specialized human cell that there is.
Image from NIH Stem Cell Information
Hematopoietic stem cells
If all you need is blood-forming stem cells, however, the medical research community has a wide variety of well-established sources and procedures -- many that have been in use for more than 30 years. We can obtain these cells from their native source (bone marrow), from the blood of a donor or from a discarded umbilical cord. All of these sources are rich in HSCs and none of them come from an embryo.
Researchers at M. D. Anderson are investigating ways to grow more cells from cord blood, purify the stem cells from blood, increase the number of stem cells in the blood, change the genes of stem cells, grow special immune cells from stem cells and make the stem cells better at finding their way back to the bone marrow. In addition, we have exciting new research using a new kind of stem cell from the structural part (instead of the blood-forming part) of the bone marrow, called mesenchymal stem cells. Some of these new approaches are already available to patients in clinical trials.