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

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

“The results merit treating more patients,” says Jeanne Loring, a stem cell researcher at Scripps Research in La Jolla, California.

Reprogrammed cells

The outermost layer of the cornea is held together by a reservoir of stem cells housed in the limbal ring – 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, ultimately leading to blindness. It can result from eye trauma or autoimmune and genetic diseases.

Treatments for LSCD are limited. They typically involve the transplantation of 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 colleagues used an alternative source of cells – induced pluripotent stem (iPS) cells – to perform the corneal transplants. They took blood cells from a healthy donor and reprogrammed them into an embryonic state, then transformed 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 operation, the team scraped off the layer of scar tissue covering the damaged cornea in a single eye, then sewed it onto epithelial sheets from a donor and placed a soft protective contact lens over it.

Eye test

Two years after receiving the transplants, none of the recipients had experienced serious side effects. The grafts did not form tumors – a known risk of iPS cell growth – and did not show clear signs of attack by the recipients’ immune systems, even in two patients who did not receive immunosuppressive drugs. . “It’s important and it’s a relief to see that the grafts were not rejected,” says Bharti. But more transplants are needed to ensure the procedure is safe, 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 1-year observation period.

Bharti says the exact cause of these vision improvements is unclear. 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 to the transplant triggering the migration of the recipient’s own cells from other areas of the eye and rejuvenating the cornea.

Nishida announced plans to launch clinical trials in March, which would evaluate the treatment’s effectiveness. Several other systems based on iPS cells tests are underway globally to treat eye diseases, says Bharti. “These successes suggest we are moving in the right direction. »