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Research

Immune cells in the retina can spontaneously regenerate

07/05/2018
It’s been discovered microglia immune cells can completely repopulate themselves in the retina after being nearly eliminated, and are even able to re-establish normal organisation and function.

Previous studies have shown that in degenerative retinal disorders, such as age related macular degeneration (AMD) and retinis pigmentosa (RP), inhibiting or removing microglia can help retain photoreceptors, and thus slow vision loss.

However, the return of microglia is still important to support the retina’s neurons, which is why the researchers investigated whether or not microglia can return to fulfil their normal functions after they had been eliminated.


"The organisation of these immune cells is quite elaborate, and all the organisation comes right back. We can actually image the eye and watch these cells divide and split and migrate as part of the repopulation response,"
Dr Wai Wong, lead investigator

The study, supported by the National Eye Institute, used a drug to deplete microglia in the retinas of mice until they had nearly disappeared, before stopping to see if the microglia would return. Within 30 days, the study’s lead investigator, Dr Wai Wong, observed that the microglia had repopulated the retina, and that they returned to normal density within 150 days.

“The organisation of these immune cells is quite elaborate, and all the organisation comes right back. We can actually image the eye and watch these cells divide and split and migrate as part of the repopulation response,” Wong said.

The researchers used an injury model where photoreceptor cells are damaged by bright light to test whether the new microglia were fully functional, and found that the new microglia were able to activate and migrate to the injury site normally.

Aside from potentially aiding treatments for RP and AMD, Wong said temporarily removing the presence of microglia could potentially be useful as a therapeutic intervention for degenerative or inflammatory disorders of the retina.

“If we were to get rid of the microglia while a large, inappropriate immune response was happening we might be able to miss the worst of the inflammation, but still come back into balance at a later point in time. We could hit pause on the immune system in the retina in a directed way,” Wong explained.

However, more research is needed to find ways to administer the therapy directly to the retina, in order to avoid off-target tissues that result from the systemic administration of current drugs.

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