In blinding eye disease, trash-collecting cells go awry, accelerate damage

NIH | JULY 5, 2015

Spider-like cells inside the brain, spinal cord and eye hunt for invaders, capturing and then devouring them. These cells, called microglia, often play a beneficial role by helping to clear trash and protect the central nervous system against infection. But a new study shows that they also accelerate damage wrought by blinding eye disorders, such as retinitis pigmentosa.

The researchers observed in the mice that very early in the disease process, the microglia infiltrate a layer of the retina near the photoreceptors, called the outer nuclear layer, where they don’t usually venture.

The microglia then create a cup-like structure over a single photoreceptor, surrounding it to ingest it in a process called phagocytosis. Wong and his team caught this dynamic process on video. The whole feast, including digestion, takes about an hour.

Phagocytosis is a normal process in healthy tissues and is a key way of clearing away dead cells and cellular debris. However, in retinitis pigmentosa the researchers found that the microglia target damaged but living photoreceptors, in addition to dead ones.

These findings suggest that therapeutic strategies that inhibit microglial activation may help decelerate the rate of rod photoreceptor degeneration and preserve vision.

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