Nanoparticles help Mayo Clinic researcher deliver steroids to retina

December 13, 2011

ROCHESTER, Minn. -- Hitching a ride into the retina on nanoparticles called dendrimers offers a new way to treat age-related macular degeneration and retinitis pigmentosa. A study by investigators at Mayo Clinic, Wayne State University and Johns Hopkins Medicine 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 age-related macular degeneration and retinitis pigmentosa are caused by neuroinflammation, which progressively damages the retina and can lead to blindness. Macular degeneration is the primary cause of vision loss in older Americans, affecting more than 7 million people, according to the National Institutes of Health. Retinitis pigmentosa encompasses many genetic conditions affecting the retina and impacts 1 in 4,000 Americans, the NIH estimates.

"There is no cure for these diseases," says Mayo Clinic ophthalmologist Raymond Iezzi, M.D., a lead author of the study. "An effective treatment could offer hope to hundreds of millions of patients worldwide."

Iezzi and fellow principal author Rangaramanujam Kannan, Ph.D., 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 -- a hallmark of each disease. The microglial cells gobble up the dendrimers, and the drug then shuts down the cells' activity.

"Surprisingly, the activated microglia 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," 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.
-end-
The study was funded by grants from the Ligon Research Center of Vision at Wayne State University, the Ralph C. Wilson Foundation and Research to Prevent Blindness.

The researchers declare no conflict of interest.

Co-authors include Bharath Raja Guru, Ph.D., Case Western Reserve University; Inna Glybina and Alexander Kennedy, both of Wayne State University; and Manoj Mishra, Ph.D., of Johns Hopkins University.

About Mayo Clinic

Mayo Clinic is a nonprofit worldwide leader in medical care, research and education for people from all walks of life. For more information, visit http://www.mayoclinic.org/about and www.mayoclinic.org/news.

Mayo Clinic

Related Macular Degeneration Articles from Brightsurf:

Levodopa may improve vision in patients with macular degeneration
Investigators have determined that treating patients with an advanced form of age-related macular degeneration (AMD) with levodopa, a safe and readily available drug commonly used to treat Parkinson's disease, stabilized and improved their vision.

Combating drug resistance in age-related macular degeneration
An international team of researchers led by Baylor College of Medicine and Houston Methodist has discovered a strategy that can potentially address a major challenge to the current treatment for age-related macular degeneration,

Study finds unexpected suspect in age-related macular degeneration
Scientists have identified an unexpected player in the immune reaction gone awry that causes vision loss in patients with age-related macular degeneration (AMD), according to a new study published today in eLife.

Potential way to halt blinding macular degeneration identified
It would be the first treatment for dry age-related macular degeneration and could significantly improve treatment for wet AMD.

Heating techniques could improve treatment of macular degeneration
Age-related macular degeneration is the primary cause of central vision loss and results in the center of the visual field being blurred or fully blacked out.

Eye's vulnerability to macular degeneration revealed
Scientists have found significant differences in the shape and biology of the same type of cell taken from different parts of the retina, according to a study in eLife.

Hallucinations associated with brain hyperactivity in people with macular degeneration
New research from The University of Queensland has shown for the first time that visual hallucinations in people with macular degeneration are associated with abnormally heightened activity in the visual cortex of the brain.

Eating leafy greens could help prevent macular degeneration
A new study has shown that eating vegetable nitrates, found mainly in green leafy vegetables and beetroot, could help reduce your risk of developing early-stage age-related macular degeneration (AMD).

An orange a day keeps macular degeneration away: 15-year study
A new study has shown that people who regularly eat oranges are less likely to develop macular degeneration than people who do not eat oranges.

Macular degeneration linked to aging immune cells
Studying mice and cells from patients, vision researchers at Washington University School of Medicine in St.

Read More: Macular Degeneration News and Macular Degeneration Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.