Stem cell researchers continue to make breakthroughs that hold out the promise of one day being able to treat all manner of diseases and physiological dysfunctions. An article in Science Daily brings us up to speed on the latest development, but first a little background gleaned from the article:
Until recently, it's been thought that the destiny of a cell was fixed early on in development. Pluripotent embryonic stem cells give rise to all the cell types in the body, but as the daughter cells become more specialized, they also become more biologically isolated. A skin cell could not become a nerve cell, etc.
That view began to change when Dolly the sheep was cloned from an adult cell in 1997, showing that, under certain conditions, a specialized cell could shed these restrictions and act like an embryonic stem cell.
And in 2007, researchers announced the creation of induced pluripotent stem cells, or iPS cells, from human skin cells by infecting them with four stem-cell-associated proteins called transcription factors. This was like returning them to their embryonic state. The process was often described in concept as moving the skin cells backward along the differentiation pathway and then guiding them forward again along a different branch into a new lineage. Thus skin cells could, through a painstaking process, be developed into nerve cells.
Finally, in 2008, Doug Melton, a co-director of Harvard's Stem Cell Institute, showed it was possible in adult mice to reprogram one type of cell in the pancreas to become another pancreatic cell type by infecting them with a pool of viruses expressing just three transcription factors.
As a result, scientists began to wonder whether it was even necessary to walk the cells back to the pluripotent stage and began to look for ways to convert one kind of cell directly to another kind.
Here's the fascinating part. Scientists at the Stanford University School of Medicine have now succeeded in transforming mouse skin cells in a laboratory dish directly into functional nerve cells with the application of just three genes. The cells make the change without first becoming a pluripotent type of stem cell.
According to Science Daily:
The finding could revolutionize the future of human stem cell therapy and recast our understanding of how cells choose and maintain their specialties in the body.
"We actively and directly induced one cell type to become a completely different cell type," said Marius Wernig, MD, assistant professor of pathology and a member of Stanford's Institute for Stem Cell Biology and Regenerative Medicine. "These are fully functional neurons. They can do all the principal things that neurons in the brain do." That includes making connections with and signaling to other nerve cells -- critical functions if the cells are eventually to be used as therapy for Parkinson's disease or other disorders.
The implications of this, not only for Parkinson's and Alzheimer's sufferers, but also for paralytics and perhaps diabetics would seem to be immense. This is truly exciting stuff. It should be mentioned also that, unlike earlier stem cell research, none of this current work involves sacrificing human embryos. This removes a great moral impediment to proceeding with the development of medical applications for stem cells.
RLC