The Remarkable Potential of Stem Cells
All living things are made up of cells. There are more than a trillion cells—perhaps more than 30 trillion—in the human body, including many kinds of specialized...
Over the past few decades, talk of stem cells has often been in the news. What exactly are stem cells, and why all the excitement? Let’s wonder a bit about the science of cells—and the remarkable potential of stem cells.
All living things are made up of cells. There are more than a trillion cells—perhaps more than 30 trillion—in the human body, including many kinds of specialized cells. Bone cells, nerve cells, skin cells, blood cells … and, yes, stem cells.
All cells are self-contained, with their insides separated from their environment by a cell membrane. This enclosure keeps cytoplasm—a thick, gel-like substance that comprises the bulk of a cell—from leaking out. The cell membrane also allows nutrients to flow in, while keeping out material that might damage the cell.
Within each cell is a nucleus that holds the cell’s genetic material. Most cells also contain mitochondria—tiny organic batteries that serve as the cell’s power supply. And within each cell is a structure called the endoplasmic reticulum, a network of membranes within the cytoplasm that carries material, such as nutrients, throughout the cell.
There are critical differences among various kinds of cells, each having specific jobs and roles to play, for instance, in enabling you to breath, to walk, to fend off diseases. Yet with all this diversity among cell types, at the moment of conception, every living organism starts as a single cell. That cell divides into two, then four, then eight, and so on. And at this stage, when you were just a blob of cells, those were all embryonic stem cells.
The special, critical feature of stem cells is that, as they divide, they begin to differentiate. Some end up as nerve cells, some as blood cells, and some as muscle cells. While those specialized cells can only create more of their own kind of cell when they divide, stem cells give rise to any of the hundreds of kinds of specialized cells in your body.
Adults do have stem cells in their bodies. These adult stem cells are the body’s repair mechanisms. They can fix damaged tissues and organs by regenerating worn out or damaged or diseased cells, no matter what kind of specialized cells they are. Adult stem cells in your bone marrow, for example, can become red blood cells, white blood cells, or platelets, which are the cells that make up your blood.
The real power of stem cells, however, is not simply in their versatility. It is, rather, that stem cells can be grown in a laboratory.
The real power of stem cells, however, is not simply in their versatility. It is, rather, that stem cells can be grown in a laboratory. And even more powerful, in the past few years, scientists have learned how to reprogram specialized cells to become like stem cells. Indeed, the 2012 Nobel Prize in Physiology or Medicine was awarded to Shinya Yamanaka of Kyoto University for his work on converting mature skin cells into cells that closely resemble stem cells.
Scientists have already been exploring the use of stem cells to treat diseases such as multiple sclerosis and cerebral palsy, as well as to repair spinal cord and bone injuries. It will certainly be many years before stem therapies are widely available, but we can look forward to a future in which scientists can grow, say, a new liver for a patient whose own liver is failing. A new liver that is a perfect match for that patient, because it is grown from his or her own cells. Stem cell research promises an exciting future for regenerative medicine.
Question to ponder:
Ethical questions arise when considering the use of stem cells taken from embryos for scientific research. What ethical issues, if any, might be associated with reprogramming someone’s skin cells to become stem cells for research or therapy?