A recently published study by Professor Gilbert Bernier of the University of Montreal and its affiliated Maisonneuve-Rosemont Hospital highlights how age-related macular degeneration (AMRD), characterized by the loss of cones, could be treated with the help of stem cells. The study explains an important in-vitro technique that uses human embryonic stem cells to produce light sensitive retina cells.
“Our technique has the ability to differentiate 80 percent of embryonic stem cells into pure cones,” explained Professor Gilbert. “Within 45 days, the cones that were allowed to grow towards convergence spontaneously developed into organized retinal tissue with a thickness of 150 microns, a success that has never been achieved before.”
Problems In Treating ARMD
ARMD results in degeneration of the macula – the central part of the retina that majorly facilitates eyesight. The cause of this degeneration is the destruction of cells and cones in the retinal pigment epithelium (RPE). The latter is the tissue responsible for reparation of visual cells in the retina, along with the removal of worn out cells.
However, the degree of reparation is somewhat limited, since we are born with a specific number of cones. Therefore, natural replacement does not take place. Moreover, with age, the maintenance of the RPE becomes less effective, resulting in accumulation of waste which forms deposits.
“Differentiating RPE cells is fairly easy. However, a complete therapy involves producing RPE cells capable of linking all neuronal tissue to the cones, which is much more intricate to develop.” Nevertheless, the challenge was taken up by the researchers.
Verifying The Novel Technique
Clusters of retinal cells were injected into the eyes of healthy mice. It was observed that the transplanted photoreceptors naturally migrated into the retina of the host. Bernie explained this achievement as a significant therapeutic solution for treating retinal pathologies as a result of photoreceptor degeneration.
Until now, obtaining large quantities of human cones had been difficult to achieve. Scientists have been trying to develop such a technique for years. This study offers the potential for developing novel treatments to treat presently non-curable degenerative diseases, such as ARMD and Stargardt disease.
“Thanks to our straightforward and efficient approach, any laboratory around the world can now create large numbers of photoreceptors. Despite having a long way to go before clinical trials can be launched, in theory, we will eventually be able to treat numerous patients,” stated Bernie.
Significance Of The Findings
The findings of this study have the potential of enhancing life expectancies, and also decreasing the incidence of ARMD, which is the biggest cause of blindness in millions of people above the age of 50. Moreover, people above 80 face this accelerated aging of the retina more prominently – perception of color is lost and at its worst, the ability to write, read, watch television and even recognize faces is lost.
Bernie’s latest research demonstrates that in order to produce cones, COCO – a ‘recombinational’ human molecule generally expressed inside photoreceptors as they develop – can methodically inhibit all signaling pathways involved in the differentiation of other retinal cells. By revealing this molecular mechanism, Bernie was able to generate numerous photoreceptors.
Apart from clinical applications, the findings could also facilitate the modeling of human retinal degenerative diseases by using induced pluripotent stem cells. This offers the possibility of creating avenues for testing and studying therapies on the patient’s own tissues.