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Looking for an Alternative to Embryonic Stem Cells
In 2009, the FDA approved the use of human embryonic stem cell-based therapy for the treatment of patients with spinal cord injuries. Cell-based therapy — the use of human cells transplanted into the human body to promote healing — is not a futuristic concept. Bone marrow transplant, for example, is a cell-based therapy that was proven to be safe and effective more than 50 years ago. Stem cells are particularly useful in these cell-based therapies because they are both immortal and flexible, meaning they can divide without end and they can become almost any type of cell.
“There are several ways of thinking about this,” says Dr. Michael Shamblott, an expert in human stem cell biology at the International Center for Spinal Cord Injury at Kennedy Krieger Institute. “One is to turn embryonic stem cells into neurons and then use them to replace the neurons that were damaged or destroyed by the injury.
“Another, and perhaps more feasible approach, is to instead turn the embryonic stem cells into oligodendrocytes, cells that would insulate the neurons that weren’t damaged by the injury, helping them to function.” Shamblott continues, “Neurons, like the wires in your home or car, conduct electrical current. If they don’t have insulation, the result is essentially a short circuit.”
The Promise of Pluripotency
Meanwhile, another phenomenon called induced pluripotency (iPS) is gaining new attention as a promising alternative to the use of embryonic stem cell-based therapy. The process converts tissue from any kind of rapidly growing cells, such as skin cells, into cells that are very similar, if not identical, to embryonic stem cells. The tissue is easily obtained by taking a small skin biopsy, much like doing a simple blood draw. The skin cells are brought to the lab and turned into a culture.
“The basis behind this process is that we force these cells to produce some of the proteins that are produced by embryonic stem cells,” Dr. Shamblott says. “They become pluripotent and, like embryonic stem cells, can become almost any cell in the adult human body.”
In the case of the spinal cord injury patient, these new cells are transplanted into the spinal cord around the area of the injury. Once there, explains Dr. Shamblott, “if it takes up residence in the tissue, it could take over some of the functions that were lost due to the injury or death of the original cell.”
The benefits of iPS cells are numerous. “We think iPS cells are superior to embryonic stem cells primarily because they are taken from and then transplanted back into the patient’s own body,” Dr. Shamblott says. “As a result, you have a supply of cells that immunologically matches the person, and when implanted, may be less likely to require the patient to be on immunosuppressant drugs. Embryonic stem cells, on the other hand, can carry with them the danger of rejection, much like any other organ transplant. Furthermore, the use of iPS cells would achieve the same positive results without the controversy that surrounds embryonic stem cells.”
Although an important goal of the Kennedy Krieger Institute is to use iPS cells to treat spinal cord injury patients, the possibilities go much farther.
“The impact of this discovery cannot be overstated,” says Dr. Shamblott. “Kennedy Krieger sees many patients with all sorts of genetic neurologic diseases. iPS cells can be made from these patients and then used to study and gain understanding of these diseases. I would say this is by far the most important finding since the discovery of embryonic stem cells and will ultimately be even more important.”