Treating Age-Related Macular Degeneration
Meera - Recently I went to the Globe theatre in London for a special event organised by the London Project to Cure Blindness. The event aimed to increase awareness about therapies currently in development to age-related macular degeneration or AMD, the most common cause of blindness in people over 60. Given how common this disease is there are currently few treatments available with one form of the disease having no treatment at all. The director of the London Project is Pete Coffey from University College London. I spoke to him at the event to find out more about the therapies he's working on and also to find out just what age-related macular degeneration is.
Pete - It's a disease of the eye which affects the elderly, typically over the age of 60. It affects the cells at the back of the eye. That's the seeing part of the eye. These cells in a very small area, known as the macular which is where your highest visual acuity is deteriorate, die and then no longer support the retina. The retina starts to die as well and that's when the person goes blind. There's a form called 'wet.' The reason it's called wet is that during the disease process vessels at the back of the eye start to grow into it and become very leaky. There's a dry form in which you get the cells dying but you don't see that bleed into the eye typically. The largest population is the dry form and the dry form today doesn't have any clinical therapy available. What this project is trying to do is to replace those cells.
Meera - How many people are affected with AMD?
Pete - In Europe about 14 million people suffer from some form of age-related macular degeneration; in the UK typically 25% of the population over the age of 60. This is a huge problem: much bigger than neurological diseases such as Alzheimer's and Parkinson's.
Meera - What are some of the major problems experienced by someone with AMD?
Pete - They're unable to read in the first instance. They find it very difficult to read text even when it's magnified. They then lose the ability in all the central vision so they can't even recognise faces, they're own family to the point where very blurred peripheral vision is the only thing they experience.
Meera - What are you hoping to look into with the London Project?
Pete - The London Project wants to use stem cells, turn the stem cells into eye cells and replace those dead cells at the back of the eye. The way in which we aim to do that is to deliver a patch of cells which can be placed into a patient's eye surgically within a 30 minute surgical procedure.
Meera - Why are stem cells good for this?
Pete - Stem cells are very good for this because they are very young. They are very plastic. Because the eye in the elderly patient is aged, it's diseased we can replace them with healthy, young, new support cells.
Meera - Do you have any idea of the success rate hoped for?
Pete - At the moment in late stage disease when we've used the patient's own cells we're getting about 25% success rate. We hope to improve that and perform the operation much earlier in the disease which will give a greater success.
Meera - You say you've used the patient's own cells, form their own eyes?
Pete - From their own eyes. The cells have been harvested from non-diseased areas. You take those cells from an area which they won't miss vision from so very peripheral and you place them under the very high acuity area which is the macular.
Meera - What happens to the region which you've just removed the cells from?
Pete - The region from which we've removed them from does actually go blind because you've taken those support cells away. It's very peripheral and the patient doesn't mind that as long as they can see where they're going, what they're eating. They are more concerned their high visual acuity rather than their peripheral vision.
Meera - One of the current treatments involves taking some healthy support cells from the undamaged region of an AMD patient's eye, usually cells from the periphery and transplanting those healthy cells into the same patient's damaged macular region to restore central vision. This method isn't possible in patients with severe damage and isn't always guaranteed. With the London Project the team are researching possible treatment using human embryonic stem cells. These stem cells can be guided into becoming support cells and create a small patch of these cells that can then be put straight into a patient's eye where they then support the retina and potentially give the patient their sight back. It sounds promising but have they got any evidence with stem cells to prove that it's really possible?
Pete - We've shown that they have the profile we would want them to have as eye cells. We've managed to put them on patches. We've managed to place them in animal models of the disease. We've also gone through a surgical procedure exactly the same way as we would do it in the clinic and it's been very successful.
Meera - That night I also met the surgeon who was hoping to make this all happen. Dr Lynden da Cruz from Moorfields Eye Hospital. He told me how in practice these stem cell patches are going to make treatment for AMD easier.
Lynden - These stem cell patches we hope to be delivered much more simply by a larger number of surgeons and might be available across a greater number of people such that we could create thousands of the patches and then have them available.
Meera - Part of the problem you were saying when it comes to treating the dry form is that there's quite a narrow window because you don't want to do it to early before because the procedures are complex. If you do it too late it's too late, basically. How is this stem cell procedure going to help with that timing?
Lynden - That's a good point. In wet degeneration which we've been treating people would lose their vision over a very short period of time, maybe a week or even two weeks. That flagged up the period from when they went from a normal retina to a retina they couldn't see with. That meant that the retina was pretty healthy. We could do our transplants or translocations and we have good results. With dry degeneration it progresses over months or even years. That means the vision is slowly being lost. We often end up doing the operations very late. This means the chance of getting good recovery's low. By creating a stem cells patch, a much simpler operation with lower risks we'll be able to do the operation much earlier in the disease and hopefully rescue a lot more vision.
Meera - Research into the potential use of stem cell patches to be transplanted into the eye could lead to treatment for a disease that not only affects so many in our population but also currently has no treatment available at all. The therapy has only been verified in animals so far but if the research continues to develop it could potentially help and entire generation to live a lot more comfortably.