Skin Cells Turned into Retinal Cells

Proceedings of the National Academy of Sciences, August 24, 2009

Researchers at the University of Wisconsin at Madison are once again in the news headlines. This time, they have reprogrammed skin cells into retinal cells. The implications of such an accomplishment offer new hope to millions of people who suffer from vision problems.

Led by Drs. David Gamm and Jason Meyer, the team of researchers took ordinary fibroblasts and de-differentiated them into a more primitive state known as iPS (induced pluripotent stem) cells, a procedure which is becoming increasingly common in research laboratories throughout the world. The iPS cells, which resemble embryonic stem cells in their pluripotency, were then re-differentiated into retinal cells. Additionally, the scientists also compared the differentiation of iPS cells into retinal cells with the differentiation of embryonic stem cells into retinal cells, and both processes appeared to progress through the same stages over the same amount of time. Both types of cells developed first into neural cells, which then differentiated further into cells of the primitive eye field, which in turn differentiated further into the more specialized cells of the retina, which is the light-sensitive, image-forming membrane on the inside of the eye, without which vision is not possible. The final cells included retinal pigment epithelium cells as well as photoreceptor cells, both of which are commonly lost in diseases of the eye such as retinitis pigmentosa and age-related macular degeneration, the latter of which is estimated to afflict approximately 30 million people around the world, and which in the U.S. is the leading cause of blindness in people 55 years of age and older.

As Dr. Gamm explains, "If you understand and follow every stage of building a photoreceptor, you're more confident because you've observed the assembly line. We can understand the disease better and see if there are ways to protect the cells or slow down the disorder." It is still not yet known, however, if these new retinal cells can actually function in vivo in the same manner as naturally occurring retinal cells. As Dr. Meyer adds, "That is among the next projects we're working on."

First pioneered in 2007, simultaneously by Dr. James Thomson of the UW-Madison as well as by Dr. Shinya Yamanaka at Kyoto University in Japan, iPS cell technology is now considered to be one of the most promising fields in regenerative medicine. With the same pluripotency as embryonic stem cells, but without any of the ethical dilemmas and controversies, iPS cells seem to be able to do anything and everything that embryonic stem cells can do.

According to Dr. Robert Lanza, chief scientific officer at Advanced Cell Technology, who did not participate in the current study but has conducted similar research, "This is an important paper. It underscores the enormous potential of iPS cells, not only for treating diseases such as blindness, but as an important tool for understanding eye development. I think it will only be a matter of time before these iPS-derived cells are used in the clinic to help restore vision in patients."

Indeed, according to Dr. Gamm, who believes that clinical trials for retinal cell replacement could be conducted within the next 5 years, "That's not pie in the sky anymore. I couldn't have said that, even two years ago."