Retina: Photoreceptor Cells

(millions of photoreceptor cells residing in the human retina gather light and transmit signals to the brain)

When photoreceptor cells die, they take a person's sight with them

People lose their sight when the light-collecting cells die. Medical researchers hoping to reverse blindness have turned their gaze toward stem cells, and recent experiments have shown that these cells could replace photoreceptors lost in macular degeneration.

As the most common form of blindness, macular degeneration affects ten percent of Americans older than 65 years.

• It first targets a protective lining called the retinal pigment epithelium (RPE), which shuttles nutrients to the photorecptor cells and is vital for their survival.
• Some researchers believe that a transplant of fresh pigment epithelium tissue could possibly rescue dying photoreceptors.
• The approach is not currently feasible considering the large amounts of tissue needed to treat the millions of Americans who show signs of early macular degeneration.
• Treating patients who have advanced degrees of macular degeneration or other photoreceptor diseases will ultimately require repairing the photoreceptor cells themselves.
• So far, research and development of the necessary cells has not been achieved for any practical human applications.

The retinas of the eyes are targets for stem cell therapies

If (when) scientists can generate and precisely identify photoreceptor cells derived from retinal stem cells, they will still have to address a host of other possible problems associated with stem cell transplanation; chief among them:

• Rejection of the transplanted cells.
• Tumor development associated with stem cells.
• Survival of the injected cells in a dying retina.

The related retino- unit of words.