Three people with severe vision impairment who received stem cell transplants experienced substantial improvements in vision that persisted for more than a year. A fourth person with severe vision impairment also had gains in their vision, but these did not last. The four are the first to receive transplants made from reprogrammed stem cells to treat the damaged cornea, the transparent outer surface of the eye¹.

The results, described in The Lancet today, they’re impressive, says Kapil Bharti, a translational stem cell researcher at the US National Eye Institute, National Institutes of Health, in Bethesda, Maryland. “This is an exciting development.”

“The results are worth treating more patients,” says stem cell researcher Jeanne Loring of Scripps Research in La Jolla, California.

Reprogrammed cells

The outermost layer of the cornea is maintained by a reservoir of stem cells housed in the limbal annulus – the dark ring around the iris. When this essential source of rejuvenation is depleted – a condition known as limbal stem cell deficiency (LSCD) – scar tissue covers the cornea, eventually leading to blindness. It can result from trauma to the eye or from autoimmune and genetic diseases.

Treatments for LSCD are limited. They usually involve transplanting corneal cells derived from stem cells obtained from a person’s healthy eye, which is an invasive procedure with uncertain results. When both eyes are affected, corneal transplants from deceased donors are an option, but these are sometimes rejected by the recipient’s immune system.

Kohji Nishida, an ophthalmologist at Osaka University in Japan, and his colleagues used an alternative source of cells – induced pluripotent stem (iPS) cells – to make the corneal transplants. They took blood cells from a healthy donor and reprogrammed them to an embryo-like state, then turned them into a thin, transparent sheet of cobblestone-shaped corneal epithelial cells.

Between June 2019 and November 2020, the team registered two women and two men aged 39 to 72 years with LSCD in both eyes. As part of the surgery, the team scraped away the layer of scar tissue covering the damaged cornea in one eye, then sewed on epithelial sheets derived from a donor and placed a protective soft contact lens on top.

Eye test

Two years after receiving the transplants, none of the recipients had severe adverse reactions. The grafts did not form tumors — a known risk of iPS cell growth — and showed no clear signs of being attacked by the recipients’ immune systems, even in two patients who did not receive immunosuppressive drugs. “It is important and a relief to see that the grafts have not been rejected,” says Bharti. But more transplants are needed to be sure of the intervention’s safety, he says.

After the transplants, all four recipients showed immediate improvements in their vision and a reduction in the area of ​​the cornea affected by LSCD. Improvements persisted in all but one recipient, who showed slight reversals during a one-year follow-up period.

Bharti says it’s not clear what exactly caused the vision improvements. It is possible that the transplanted cells themselves have proliferated in the recipient’s cornea. But the vision gains could also be due to the removal of scar tissue before the transplant, or the transplant causing the recipient’s own cells to migrate from other regions of the eye and rejuvenate the cornea.

Nishida says he plans to launch clinical trials in March that would evaluate the treatment’s effectiveness. Several others based on iPS cells test are underway globally to treat eye diseases, says Bharti. “These success stories suggest we are moving in the right direction.”