This year is off to an exhilarating start with not just one, but two high-profile scientific papers showing that stem cell transplantation can restore vision in blind mice.
Those of you who keep up-to-date with FFB research stories might be wondering: what’s new here? Haven’t scientists already made blind mice see? The short answer is – yes. Scientists first reported that they could restore vision in blind mice in 2006. This landmark discovery set the stage for a flurry of research focused on using stem cell transplantation to restore sight.
Although I love the history of science, I can’t list everything that’s happened over the past decade in this post (I’ll save the complete overview for another time). What matters here is that despite scientists many success stories with small animals, they still face significant hurdles that are preventing stem cell transplantation approaches involving photoreceptors from being tested in humans.
What’s the hold up?
Basically, photoreceptor cells (the light-sensing cells in the eye that degenerate in many different blinding eye diseases) are very complicated neural cells that do not tend to survive after they have been transplanted. Most recently, a number of papers have suggested that none of the cells survive post-transplantation. And, in fact, the very few cells that were thought to be the survivors are actually just cells that were already in the eye, but have taken on a new identity because the transplanted photoreceptors transferred some of their material to the old host cells before dying. (For more details about this “material transfer” phenomenon, which was our top discovery of 2016, check out this story.)
What’s new and important about these two discoveries?
The first paper, published in Stem Cell Reports, matters for a few reasons, first – it’s led by Dr. Masayo Takahashi from the esteemed RIKEN institute in Japan. Dr. Takahashi came into the limelight in 2014 when she pioneered the first clinical trial testing if induced pluripotent stem cells (iPSCs) could be used to treat age-related macular degeneration (AMD). Her team has demonstrated success with taking research from the laboratory into the clinic. So, at the FFB, we are thrilled that her team is now having success working on end-stage retinal degeneration (aka, blind mice) because, if successful, this work could be relevant to a variety of different blinding eye diseases, such as retinitis pigmentosa (RP). Second, the neat new thing about her team’s recent paper is that they transplanted intact retinal tissue, not just single photoreceptor cells. This transplanted tissue was able to make connections with remaining cells in the eyes of the blind animals. More importantly, after transplantation, the animals gained the ability to respond to light.
The second paper, published in Cell Stem Cell, by Dr. Deepak Lamba’s team from the Buck Institute in California, made a clinically significant finding. Their paper is very important because it sheds light on the question about why so many photoreceptors die after transplantation. Recently, some scientists have suggested that this death might be due to an immune response. However, others have argued that the eye is “immune privileged” and that it does not reject foreign tissue like other parts of the body. Lamba’s study settles the debate by showing that the survival rate of transplanted photoreceptors increases significantly if they are given to animals that lack an important immune cell receptor (essentially to animals that don’t have a functioning immune system). Not only did they show a 10-fold increase in the survival rate of transplanted cells, they also demonstrated that these cells restored vision for a long-term period!
Both of these new discoveries fuel our enthusiasm about the growing potential to restore vision using a stem cell transplantation approach. We will be following the race to restore sight throughout the year and, thanks to generous FFB donors, we will be doing EVERYTHING that we can to make sure that these new discoveries impact patients who are waiting for treatments. Stay tuned for more exciting developments… we’re just getting started!