Researchers have been tantalized by the possibilities of so-called regenerative medicine — treatments that replace lost or damaged tissue with healthy new tissue.  At the heart of this concept are stem cells, those undifferentiated cells from which all of our tissues arise.  Where do you find them?  How do you use them?  Can they be made to work in new therapeutic ways?  These are some of the questions that have obsessed researchers in this area for over a decade.

Initially, it was thought that the only place to obtain useful stem cells was to take them from a human embryo.  However, the moral, ethical, and even political controversies surrounding this practice led researchers to look elsewhere.  What they discovered was that a wide variety of cells in the adult body can be reprogrammed to act as stem cells.  For example, the journal Blood¹ recently reported that ordinary circulating human blood cells can be modified to perform like stem cells.  The research was done last year at the Howard Hughes Medical Institute at Children’s Hospital in Boston, Massachusetts.

Modern genetic engineering techniques have made this type of work possible.  In this case, the scientists harvested a cell known as CD34+ from an adult male and then infected it with a virus that carried genes from stem cells.  Those genes reprogrammed the cells’ internal functions so that they acted exactly like embryonic stem cells with the ability to change into any tissue of the body.  Furthermore, in experiments with mice, the researchers injected the newly made stem cells and watched as they created new respiratory tissue, bone, and even nerve cells. 

Another recent report, this one from the journal Nature,² described how researchers at Mount Sinai Hospital found a way to deliver those reprogramming genes without using a virus, which can sometimes damage DNA in the process. 

Moreover, other researchers have found success simply by using a person’s own bone marrow, a rich source of stem cells.  Scientists at Tel Aviv University recently were able to insert bone marrow stem cells into damaged brain tissue and then track their progress using MRI scans.  What they saw, as reported in the journal Stem...