Stem cell therapy has become the subject of huge interest and vigorous debates. Promoters believe stem cells offer great promise for new medical treatments to combat cancer, diabetes, Alzheimer’s and other regenerative diseases, while the opposition argues that research on embryos—the prime source of the most versatile stem cells, pluripotent—destroys human life. In the past year, scientists have found genes that can transform ordinary skin cells into cells that look and act like embryonic stem cells, eliminating the use of an embryo, and the ethical concerns. The downside is that delivery of these genes requires the use of a virus, raising concerns the cells could cause tumors or other effects if placed in a patient. Now, researchers say they have discovered a new method of transporting the genes without the use of such potentially harmful viruses, thereby overcoming a major hurdle for safe, personalized stem cell therapies in the future.

Other scientists, however, while crediting the work as an important advance, say it remains crucial to continue work on both types of cells. “The point is, we don’t know yet what the end potential of either of these approaches will be,” said Mark A. Kay of Stanford University. “No one has cured any disease in people with any of these approaches yet. We don’t know enough yet to know which approach will be better.”