Genetics and stem cells

Stem cell trial for eye condition to go ahead

“UK medics lead Europe's first embryonic stem cell trial,” reported BBC News. It said that doctors at Moorfields Eye Hospital in London have been “given the go-ahead” to carry out Europe's first clinical trial using human embryonic stem cells (cells from early stage embryos that have the potential to develop into any type of body cell).

In the trial in London, retinal cells derived from embryonic stem cells will be injected into the retina of people with Stargardt's macular dystrophy, which is an inherited condition that causes progressive, and eventually total, loss of central vision.

This early trial, which is likely to start within the next few months, is aimed at testing the safety of the treatment in humans. It may be some time before we know whether it works. If the results indicate that there are no serious side effects, further trials in larger numbers of people will give a better idea of how well it works for people at different stages of the disease. The researchers hope that the treatment may also work for other eye conditions, such as age-related macular degeneration, but this is only a theory at present and further research will be needed to investigate this.

What is Stargardt’s disease?

Stargardt’s disease or Stargardt’s macular dystrophy is the most common form of inherited juvenile macular degeneration, affecting around one in 10,000 children. To develop the condition, people need to inherit a copy of the ‘mutant’ Stargardt's gene from both parents. The parents themselves will not have been affected if they carry only one copy of the gene.

The condition affects the area of the retina called the macular, which enables us to see directly in front of us. This part of the retina is needed for everyday activities such as reading and writing. The two main changes that occur on the retina are an oval lesion around the macular area, which is referred to as having a ‘beaten bronze’ appearance and which causes gradual deterioration in the function of the macular cells over time. The second change that is distinctive of the condition is the appearance of yellowish flecks around the lesion. These are lipid (fat) deposits.

The changes to the macular occur gradually, so that most affected individuals will first start to notice visual problems as an adolescent. Patients may be advised to avoid exposure to bright light and to wear UV-protective sunglasses to try to slow progression of the disease. There are currently no treatments to prevent the visual loss. Most sufferers will become legally blind (less than 6/60 vision) in adulthood due to the loss of their central vision.

What are embryonic stem cells?

Embryonic stem cells are unique in that they have the potential to develop (differentiate) into any type of adult body cell. Most embryonic stem cells are taken from embryos that have been fertilised in vitro in the laboratory (IVF), and the cells are then cultured in the laboratory, remaining in their undifferentiated form unless researchers put them under conditions that will allow them to change into different cell types. Under laboratory conditions it has been possible to develop retinal cells from these cells, which is a significant advance and could potentially be translated into new treatments for patients who have otherwise untreatable visual loss due to damage to their own retinal cells. As a first step, the researchers would need to test the safety of transplanting retinal cells in a small number of affected individuals.

The newspapers report that the team at Moorfields Eye Hospital has been given approval to go ahead with the trial by the Medicines and Healthcare Products Regulatory Agency (MHRA). This is the UK governing body responsible for ensuring public safety by monitoring the safety of all medical treatments and procedures.

The technique was originally developed by the US company Advanced Cell Technology (ACT), which started similar trials in the United States from November 2010.

How will the trial be performed?

The trials are due to start in the next few months, and will be led by Professor James Bainbridge, one of Moorfields’ retinal surgeons, at the National Institute for Health Research (NIHR) biomedical research centre for ophthalmology, based at Moorfields and the University College London (UCL) Institute of Ophthalmology. During an operation lasting up to an hour, the stem-cell-derived retinal cells will be transplanted into adults with severe sight impairment as a result of Stargardt’s disease, but who are otherwise healthy.

What is the purpose of the trial?

At this current early stage in development of the technology, the trial has one principal aim - to see whether transplanting retinal cells into people with Stargardt’s disease is safe. The trial is important because there are currently no treatments available for Stargardt’s disease. Therefore, if this treatment is successful it could have huge potential and have a life-changing effect for affected individuals.

When will we know if it has been successful?

The potential for this technique to improve vision will not be known for a long time. The few people who are treated by the procedure in this initial trial will need to be followed up for some time to assess their visual change and any adverse effects. However, to test the efficacy of the technique thoroughly will require further trials with much larger numbers of people. Such trials  may go ahead if this first trial demonstrates the technique’s safety.

The current trial is specifically related to people with Stargardt’s disease. It is hoped that in the future the technique could be developed and possibly used to treat other blinding disorders of the retina, such as age-related macular degeneration (AMD), which is the most common cause of age-related visual loss. However, it is too early to speculate on other potential uses for the technique at its current stage.

NHS Attribution