US scientists have taken an important step towards using stem cells to treat age-related macular degeneration (AMD), the leading cause of blindness in the UK. The study demonstrates, for the first time, the ability to direct human iPS cells (induced pluripotent stem cells) to become the type of eye cells that die and cause loss of sight in sufferers of the disease.
'We have shown that we are able to generate retinal cells from cells originally taken from a small amount of biopsied skin, that are then induced to become stem cells', explained study leader Dr Nady Golestaneh from Georgetown University Medical Centre in Washington, DC. 'The retinal cells we have generated are really functional… they mimic the function of native retinal cells that play a key role in the eye for light absorption, nutrition and receptor function'.
AMD affects a small part of the retina at the back of the eye, leading to death of retinal pigment epithelial (RPE) cells, a coloured layer which nourishes the light-receiving cells of the retina. Around one in 50 people more than 50 years of age, and up to one in five people over the age of 85, are affected by the disease, which results in the gradual loss of central vision needed for daily tasks such as reading and driving.
While existing treatments slow the progression of AMD, there is currently no cure. Human iPS cells offer the potential to use patient-specific stem cells to generate retinal cells for transplant. However, for transplantation to be possible, the iPS cells must first be programmed to possess the characteristics of native RPE cells and, until now, there has not been evidence that iPS-derived RPE cells have the required ability.
The study authors were careful to stress that their work is preliminary and much future research is needed before these cells can be used clinically. They pointed out that the cells they produced also displayed some structural abnormalities and chromosome damage, highlighting the need to focus on generating 'safe', as well as viable, iPS-derived cells.
'We also identified some issues that need to be worked out before these cells are ready for transplantation but overall, this is a tremendous step forward in regenerative medicine', concluded Dr Golestaneh. The study was published in the journal Stem Cells.