It might be possible to turn on the eye's own resources to regenerate damaged retinas, without the need for transplanting outside retinal tissue or stem cells, according to a new study.
Researchers have discovered a chemical in the eye that triggers the dormant capacity of certain non-neuronal cells to transform into progenitor cells, a stem-like cell that can generate new retinal cells.
If the next step works in animal disease models, then clinical testing would be a possibility soon, offering hopes for millions of victims of degenerative eye diseases.
Scientists have long been aware of Müller cells (existing in the eye), presuming that they were responsible for keeping retinal tissue protected and clear of debris.
In recent years, however, researchers have reported that these cells sometimes exhibit progenitor cell behaviour and re-enter the cell cycle (dividing and differentiating into other type of cells).
Progenitor cells are similar to stem cells but are more mature and are more limited in the number of cells types they can become.
But until this study, scientists have not understood what triggers the transformation.
In their study, Dong Feng Chen of Harvard Medical School and her team observed that when the naturally occurring chemicals known as glutamate and aminoadipate (derivative of glutamate) were injected into the eye, Müller cells began to divide and proliferate.
Not certain if these chemicals directly signalled the transformation, they tested them in the lab and in mice. They added each chemical separately to cultures of pure Müller cells and injected each into the space below the retina in healthy mice.
In both cases, the cells became progenitor cells and then changed into retinal cells. And with aminoadipate, the newly minted retinal cells migrated to where they might be needed in the retina and turned into desirable cell types.
Specifically, they showed that by injecting the chemical below the retina, the cells give rise to new photoreceptors - the type of cells that are lost in retinitis pigmentosa or macular degeneration leading to blindness.
The discovery has been published in the March issue of Investigative Ophthalmology and Visual Science.