In a groundbreaking, new achievement, researchers at the University of Washington in Seattle (UWS) have managed to create photoreceptor cells directly from adult, differentiated skin cells. This feat has been successfully tested in a series of mouse experiments, in which the rodents had their retinas “outfitted” with this type of cells. The investigation showed that the photoreceptors integrated normally with the surrounding tissue, which brings great hope that one day this type of treatment could be applied to humans as well.

The new light-sensing retinal cells could be used to address conditions such as retinitis pigmentosa and macular degeneration, which affect millions of people around the world. In order to achieve this, the UWS group employed induced pluripotent stem cell (iPSC) technology, which enabled them to revert fully differentiated skin cells to their embryonic state. This was done by manipulating only a few genes in the original batch of cells. In their pluripotent state, these cells can differentiate into any type of cell in the human body, including bone, cartilage, soft tissue and nerve cells.

Thomas Reh, the leader of the UWS team, is not on his first attempt of obtaining photoreceptors from stem cells, but his early experiments were conducted using the embryonic variety. The new approach works best for two reasons. First off, it circumvents the ethical debate associated with embryonic stem cells (ESC), and secondly it allows for the cells to be harvested from the patient directly. This means that all possible incompatibility issues are avoided, since all cells in a body have the same genetic material. Basically, there will be a zero risk of a patient's immune system attacking the newly implanted cells.

In addition to their practical applications in humans, the new cells will also provide researchers with a method of studying new drug therapies, and also of conducting more in-depth research on diseases that lead to retinal degeneration. They will be especially useful if the patient they are harvested from suffers from a genetic mutation that led to the development of his or her condition, since the skin cells would contain all the genetic material involved. Researchers could then isolate the gene, or combination of genes, that promotes the condition, and develop new methods of inhibiting them in other people.

“There are no good drugs to slow photoreceptor degeneration. One reason we don't have more molecules we can test is that we don't have good animal models for many human retinal diseases,” Reh, who is a neurobiologist at UWS, says, quoted by Technology Review.