Induced PluriPotent Stem Cells

Some of the first trials to test whether reprogrammed stem cells can repair diseased organs have begun to report positive results. Research teams involved in the studies, all based in Japan, say they provide early hints that the hotly anticipated technology works. But many researchers outside the country are cautious about overstating the significance of the trials, saying they were small and the results have yet to be peer reviewed.

Induced pluripotent stem (iPS) cells are those that have been reprogrammed from mature cells — often taken from the skin — into an embryonic-like state. From there, they can then turn into any cell type and be used to repair damaged organs.

In January, researchers reported in a preprint1 that the first person in Japan given a transplant of heart-muscle cells made from reprogrammed stem cells had experienced improved heart function following the procedure. Then, in April, another group announced that several people’s vision had improved after their diseased corneas were transplanted with corneal cells made from reprogrammed stem cells — a world first.

Ongoing trials are “delivering encouraging first insights into the evolution of iPS-cell-based therapies, from lab to patient”, says Wolfram-Hubertus Zimmermann, a pharmacologist at the University Medical Centre Göttingen in Germany.

The biggest impact of the iPS-cell trials in Japan so far is that they “give people confidence all over the world that it is doable”, says Kapil Bharti, a translational stem-cell researcher at the US National Eye Institute in Bethesda, Maryland.

The iPS-cell field is hugely popular in Japan, in large part because it was a local scientist, Shinya Yamanaka at Kyoto University, who discovered how to make the cells. Expectations for the potential uses of iPS cells soared in 2012, when Yamanaka won the medicine Nobel prize for his 2006 discovery. In 2013, the Japanese government announced that it would pour ¥110 billion (US$814 million today) over the next ten years into regenerative medicine.

In that time, Japanese scientists have launched at least ten trials in people. These have largely shown that the technology is safe, but have yet to establish that it has a beneficial effect. Now, public enthusiasm has waned, which threatens future government funding, says Masayo Takahashi, an ophthalmologist and president of the cell-therapy company Vision Care in Kobe, Japan.

iPS-cell technology has only been around for 16 years. And bringing it into clinical testing has happened unbelievably fast,” says Zimmermann. “The challenge is that this is all happening under high public attention.”


How To Reverse Congenital Blindness

Researchers funded by the  American National Eye Institute (NEI) have reversed congenital blindness in mice by changing supportive cells in the retina called Müller glia into rod photoreceptors. The findings advance efforts toward regenerative therapies for blinding diseases such as age-related macular degeneration and retinitis pigmentosa. A report of the findings appears online today in Nature. NEI is part of the National Institutes of Health.

This is the first report of scientists reprogramming Müller glia to become functional in the mammalian ,” said Thomas N. Greenwell, Ph.D., NEI program director for retinal neuroscience. “Rods allow us to see in low light, but they may also help preserve cone photoreceptors, which are important for color vision and high visual acuity. Cones tend to die in later-stage eye diseases. If rods can be regenerated from inside the eye, this might be a strategy for treating diseases of the eye that affect photoreceptors.”

Photoreceptors are light-sensitive cells in the retina in the back of the eye that signal the brain when activated. In mammals, including and humans, photoreceptors fail to regenerate on their own. Like most neurons, once mature they don’t divide.

Scientists have long studied the regenerative potential of Müller glia because in other species, such as zebrafish, they divide in response to injury and can turn into photoreceptors and other retinal neurons. The zebrafish can thus regain vision after severe retinal injury. In the lab, however, scientists can coax mammalian Müller glia to behave more like they do in the fish. But it requires injuring the tissue.

From a practical standpoint, if you’re trying to regenerate the retina to restore a person’s vision, it is counterproductive to injure it first to activate the Müller glia,” said Bo Chen, Ph.D., associate professor of ophthalmology and director of the Ocular Stem Cell Program at the Icahn School of Medicine at Mount Sinai, New York.

We wanted to see if we could program Müller glia to become rod photoreceptors in a living mouse without having to injure its retina,” added Chen, the study’s lead investigator.