Retinal transplants using induced pluripotent stem (iPS) cells can help partially restore lost visual function in mice, a Riken research institute study has found.

Scientists said photoreceptors, a permanent and irreplaceable element of the retina, replicated from mouse iPS cells were found to function after being transplanted.

Once the effectiveness and safety of photoreceptors derived from human iPS cells can be confirmed, scientists plan to kick off a clinical study within the next two years on people with retinal degeneration.

“If the transplant is successful, there are possibilities the technology can delay the progress of the disease or partially recover vision,” said Deputy Project Leader Michiko Mandai of the institute’s Laboratory for Retinal Regeneration.

Some 30,000 people nationwide are believed to suffer from retinal degeneration, a mostly inherited condition that destroys photoreceptors.

The latest study was published in the U.S. academic journal Stem Cell Reports on Jan. 10.

Photoreceptors are vital to human vision, as they are responsible for converting light into signals and sending them to neurons connected to the brain. They are sandwiched between these neurons and the pigment epithelium, a layer of tissue that assists retinal activity. The body is unable to reproduce photoreceptors when they are destroyed, leading to vision impairment and blindness.

The research team tackled this problem by working on what they found in an earlier study.

The scientists knew that immature photoreceptors produced from mouse iPS cells can become mature after being transplanted into mice with degenerated photoreceptors.

In the latest study, the researchers inspected retinas removed from mice after more than a month since the transplant and found that the photoreceptors were properly connected to the neurons. Signals were also found to successfully transmit to the neurons when light was shone on the retinas.

Behavioral analysis of these mice showed that about 40 percent of them reacted to light.