Scientists have for the first time successfully grown sight-giving cells in the lab and integrated them into the eyes of living mice.
The experiment, the results of which are published in the journal Nature Biotechnology, point to the possibility of eventually reproducing the very complex cells and structures involved in creating eyes. It also marks the first time scientists have ever been able to fully integrate artificially grown retinal cells into the retina’s larger structure.
“The breakthrough here is that we’ve demonstrated we can transplant photoreceptors derived from embryonic stem cells into adult mice. It paves the way to a human clinical trial because now we have a clear route map of how to do it,” Professor Robin Ali of Moorfields Eye Hospital and University College London is quoted as saying.
There are two types of photoreceptors in the eyes. They are known as rods and cones.
The test mice in this case had been robbed of functioning rods, meaning that they have very little night vision. Rod loss is a leading cause of sight loss in humans, relating to a number of degenerative eye diseases such as age-related macular degeneration, among others.
Using a recent breakthrough in 3D culture techniques, Professor Ali and team, using stem cells extracted from mouse embryos, grew light-sensitive rod cells using an artificial retina in a laboratory dish. This allowed the rod cells to conform to the complex structure that is found in the retina and that is important for proper eye function.
The scientists then transplanted 200,000 of those photoreceptor cells into the retina of the night blind mice.
Three weeks after transplantation and a proportion of those 200,000 photoreceptor cells had integrated into the mouse retina. In fact, they now exhibited characteristics of normal mature rod cells. Moreover, the scientists also observed new nerve connections, suggesting that the cells were able to establish connections with the retina’s nerve system.
However, the scientists have not yet observed any improvement in the mice subjects’ night vision. They remain hopeful, however, that this test points the way toward human trials — and soon.
“This is a real proof of concept that photoreceptors can be transplanted from an embryonic stem cell’s source and it gives us a route map to now do this in humans. That’s why we’re so excited, five years is a now a realistic aim for starting a clinical trial,” Ali told the BBC.
The efficiency of the procedure and the uptake of artificially grown rods would have to be dramatically improved before any human treatment would be viable, but there is reason to think that this might be achievable.
The second issue, however, is one that is less easy to brush off: that of animal testing.
This research has been done on specially impaired mice. The ethics of that remain a concern for many animal rights advocates, but even discounting this, there is the fact that, while the procedure should remain similar when adapting it to humans, this is all just hearsay until human research is carried out and the treatment’s effectiveness for human patients ascertained.
This once again outlines why a growing number of people even within the medical research field oppose animal tests as, a large proportion of cases, arbitrary and cruel.
A third issue, of course, would be the need to use human embryonic stem cells, something that currently raises fierce opposition among those who, despite no evidence, contend that human life begins at conception.
That said, this research offers a tantalizing glimpse at an achievable way to treat blindness. This is something that before seemed decades away, but now may just be a matter of years.
For the 21.2 million American adults who are forced to live their lives either with partial sight or no sight at all, this news will still be significant and welcome.
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