Treating disease is about fixing broken parts — about replacing cells that no longer work as they should, repairing tissues that falter and boosting systems that fail. But curing disease is a different matter. To cure disease, you have to do all of that and more. You have to remove the pathological cause of the problem and to ensure that it doesn’t return. This requires teasing out where rogue cells went wrong and finding a way to nurture healthier ones to replace them.
That’s where the promise of stem cells lies. As the mother cells of every tissue in the body, they are the biological ore from which the body emerges. All cells can trace their provenance to a stem cell, to the embryo and the first days after fertilization when such cells form. It’s now possible to grow stem cells in a lab, not just from embryonic tissue but also by turning back the clock on an already developed cell like one from the skin, bypassing the embryo altogether with four important fountain-of-youth genes that rework the skin cell’s DNA machinery and make it stemlike again.