Stem cell treatments succeed and fail in treating eye disease

In two different attempts to treat degenerative eye diseases with stem cells, three patients have been blinded, while disease progression has been stopped in a separate patient.

Two articles, published in the New England Journal of Medicine, have described two very different approaches and outcomes to treat macular degeneration, a disease that causes progressive sight deterioration, and is a leading cause of vision loss in the elderly.

The first report was written by scientists and clinicians at the Bascom Palmer Eye Institute at the University of Miami. They discussed three patients who reportedly paid US $5000 for a procedure at an unnamed for-profit clinic in Florida (the authors were not themselves involved with the procedure).

Cells had been taken from the fat cells of the patients, and processed with enzymes to produce adipose-derived stem cells. These cells were mixed with plasma and platelets from the patients' blood and injected into their eyes. There is no current evidence that adult stem cell therapy can treat disease, or that adipose-derived stem cells can mature into photoreceptor cells which enable sight.

Unusually, these injections were made into both eyes of each of the patients. Generally with experimental procedures, only one eye is used so that if complications arise, vision in the other eye might be retained.

The patients exhibited complications including detached retinas and bleeding, and while all three had some vision remaining before the procedure, after the complications they were effectively or completely blind.

Dr Thomas Albini of the Bascom Palmer Institute, and one of the writers of the report, said, 'There's a lot of hope for stem cells, and these types of clinics appeal to patients desperate for care who hope that stem cells are going to be the answer, but in this case these women participated in a clinical enterprise that was off-the-charts dangerous.'

While the FDA has previously issued a warning about stem cell therapy (see BioNews 820), the procedure was not subject to FDA approval because the cells were not transferred between patients and were considered 'minimally processed'.

The second study was carried out by a team of researchers at the RIKEN Laboratory for Retinal Regeneration, Japan.

The scientists took skin cells from a patient and reprogrammed them to generate iPS (induced pluripotent stem) cells, which were developed into retinal pigmented epithelium (RPE) cells, one of the cell types lost in macular degeneration. A sheet of these cells measuring one by three millimetres was inserted into one of the patient's eyes.

After more than one year, no complications had been observed and decline in visual function appeared to have stopped, although no visual improvement was seen either. This study marks the first time that iPS cells have been used to treat any condition in a human (see BioNews 711).

Plans to repeat this procedure on a second patient were called off for safety reasons when the RPE cells prepared were found to have accumulated minor genetic mutations. Professor Shinya Yamanaka of Kyoto University, who won a Nobel Prize for creating iPS cells and was an author of the study, told Science Magazine: 'These changes do not directly induce cancer, but we wanted to make safety the first priority.'

In an editorial discussing the two different reports, Professor George Daley of Harvard Medical School wrote that the caution of the Japanese team 'contrasts markedly' with the approach of the Florida clinic, 'who treated the three patients with an unproven stem cell therapy that ended up have devastating effects on their vision.'