01/19/2012 0 Comments

Hitching a ride into the retina on nano-particles called dendrimers offers a new way to treat age-related macular degeneration and retinitis pigmentosa, say investigators at the Mayo Clinic, Wayne State University and Johns Hopkins. Their study shows that steroids attached to the dendrimers target the damage-causing cells associated with neuroinflammation, leaving the rest of the eye unaffected and preserving vision. The findings appear in the journal Biomaterials.

Dry AMD and RP are caused by neuroinflammation, which progressively damages the retina and can lead to blindness. “There is no cure for these diseases,” says Mayo Clinic ophthalmologist Raymond Iezzi, MD, a lead author of the study. “An effective treatment could offer hope to hundreds of millions of patients worldwide.”

Dr. Iezzi and fellow principal author Rangaramanujam Kannan, PhD, an ophthalmology professor at the Wilmer Eye Institute of Johns Hopkins, developed an intracellular, sustained-release drug delivery system. The research, conducted in part at Wayne State University’s Kresge Eye Institute with collaboration from Wayne State’s College of Engineering and Ligon Research Center of Vision, tested the dendrimer delivery system in rats that develop neuroinflammation.

The target was microglial cells, inflammatory cells in charge of cleaning up dead and dying material in the eye, Dr. Iezzi says. When activated as “trash collectors,” the cells cause damage via neuroinflammation. The microglial cells gobble up the dendrimers, and the drug then shuts down the cells’ activity.

“Surprisingly, the activated micro-glia in the degenerating retina appeared to eat the dendrimer selectively, and retain them for at least a month. The drug is released from the dendrimer in a sustained fashion inside these cells, offering targeted neuroprotection to the retina,” Dr. Kannan says.

The treatment reduced neuroinflammation in the rat model and protected vision by preventing injury to photoreceptors in the retina. Though the steroid offers only temporary protection, the treatment as a whole provides sustained relief from neuroinflammation.

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