Medical researchers have long hoped that stem cells can one day be used to restore sight in people suffering from blindness.
But one of the major hurdles for the treatment is that the cells die before they have a chance to get to work.
In a new study however, scientists at the Buck Institute have found that the immune system could partly be to blame, and they’ve found a way to fix it.
The result? The scientists were able to restore vision in mice.
They hope the results could pave the way for the restoration of sight in humans suffering macular degeneration, a common cause of age-related blindness.
“This turned into a nice story of long-term restoration of vision in completely blind mice,” said Buck faculty and senior author Deepak Lamba, PhD, MBBS.
“We show that these mice can now perceive light as far out as 9-months following injection of these cells.”
So how did they do it?
The researchers tested the stem cells in mice which are lacking a specific immune cell receptor, making them unable to reject the transplant.
“This mouse strain is great model for this research because they are otherwise healthy and normal, including in their vision, so it allows us to conduct studies focused on cell integration,” said the publication’s lead author, Jie Zhu, PhD, a postdoctoral researcher.
The scientists found that in these mice ten times more cells matured and were integrated into the retina, but they hadn’t yet proved they worked.
The next stage of the study was to transplant the cells into mice that were born blind.
Nine months to a year later, the mice were responding to light and transmitting sight messages to the brain.
“That finding gives us a lot of hope for patients, that we can create some sort of advantage for these stem cell therapies so it won’t be just a transient response when these cells are put in, but a sustained vision for a long time,” said Lamba.
“Even though the retina is often considered to be ‘immune privileged,’ [meaning cells of the immune system don’t monitor those locations] we have found that we can’t ignore cell rejection when trying to transplant stem cells into the eye.”
The scientists hope that the stem cells treatment could be combined with drugs that have already been approved, to treat macular degeneration.
“Using an antibody against this specific receptor means that the immune system might not need to be suppressed more generally, which can be very toxic,” said Zhu.
Macular degeneration is the most common cause of blindness and partial-sightedness in the UK, affecting more than 185,000 people in the UK alone.