One major branch of future progress in stem cell therapy will discard transplantation of cells in favor of manipulating the signals that tell local cells what to do - which is generally what the transplanted cells are actually doing anyway. This will become more effective as researchers gain a better understanding of the intricacies of cell signalling relevant to growth and repair, but here is an early example of what can be done with this sort of approach:
In the first human study of its kind, researchers activated heart failure patients' stem cells with gene therapy to improve their symptoms, heart function and quality of life. [Researchers] delivered a gene that encodes a factor called SDF-1 to activate stem cells like a "homing" signal.
SDF-1 is a naturally occurring protein, secreted by cells, that guides the movement of other cells. Previous research [has] shown SDF-1 activates and recruits the body's stem cells, allowing them to heal damaged tissue. However, the effect may be short-lived. For example, SDF-1 that's naturally expressed after a heart attack lasts only a week. In the study, researchers attempted to re-establish and extend the time that SDF-1 could stimulate patients' stem cells. Study participants' average age was 66 years.
Researchers injected one of three doses of the SDF-1 gene [into] the hearts of 17 patients with symptomatic heart failure and monitored them for up to a year. Four months after treatment, they found: 1) Patients improved their average distance by 40 meters during a six-minute walking test. 2) Patients reported improved quality of life. 3) The heart's pumping ability improved. 4) No apparent side effects occurred with treatment.
"We found 50 percent of patients receiving the two highest doses still had positive effects one year after treatment with their heart failure classification improving by at least one level. They still had evidence of damage, but they functioned better and were feeling better." Researchers are now comparing results from heart failure patients receiving SDF-1 with patients who aren't. If the trial goes well, the therapy could be widely available to heart failure patients within four to five years.