Rock Stars of Vision Research: BrightFocus Grantees Featured in ARVO 'Hot Topics’
This research was supported by BrightFocus
In the research community, it’s an honor to give a presentation at ARVO. In order to present their latest research in an ARVO poster or talk, researchers’ abstracts have to undergo peer review and be accepted by the program committee. BrightFocus congratulates the more than 100 current and past grantees, and members of our Scientific Review Committees, who were selected to be ARVO 2015 presenters!
To have your research chosen as a “Hot Topic” by the ARVO Scientific Program Committee is an attention-getting distinction. It signals the newest and most promising research in a given field that may be indicative of an emerging direction or trend. This year, seven BrightFocus grantees had their research chosen as Hot Topic presentations. Generally, only a fraction of accepted abstracts – just 3 to 5 percent--are selected as Hot Topics.
Here are our grantees who gave this year’s Hot Topic presentations, with a short description of their research.
Macular Degeneration Research Hot Topics
A surprising way to treat wet AMD
It’s a novel approach that 2013-15 BrightFocus grantee Sarah Doyle, PhD, and co-principal investigators Matthew Campbell, PhD, and Luke O’Neill, PhD, all of Trinity College Dublin (TCD), have tested at increasingly higher levels.
They’ve shown that interleukin 18 (IL-18), a naturally occurring cytokine, or inflammatory enzyme in the body, helps, rather than hinders, the eye’s recovery from choroidal neovascularization (ie, CNV, or the growth of wet, leaky blood vessels seen in “wet AMD”). The team’s hope is their early experiments may propel IL-18 into clinical trials involving humans, and that this novel approach might someday become a candidate for FDA approval as a treatment for macular degeneration.
Their hypothesis has been challenged because inflammatory factors are considered harmful to the retinal pigmented epithelial (RPE) cells which nourish the retina. In fact, other researchers had shown that a form of IL-18, when administered, led to cell death. However, following that report, “we started trying to repeat some of their experiments in vitro, and we couldn’t,” Doyle said in an interview about their past several years’ work.
Instead, in 2012, on an earlier 2011-13 BrightFocus grant held at TCD by Peter Humphries, PhD and Campbell, their team made the discovery that IL-18 induced a significant decrease in laser-induced CNV volume and size. “And when combined with murine anti-VEGF, we actually got increased attenuation of laser-induced CNV,” Campbell told a crowd in one of ARVO’s largest lecture halls. This line of research continues be supported by the more recent BrightFocus grant to this group.
Over the past year, the group has repeated the experiments in monkeys, using intravitreal injections to the back of the eye at varying dose levels. Results show that IL-18 is effective at preventing laser-induced CNV development. Importantly, even at the highest dose level (10 times that envisioned in humans), it did not cause RPE or retinal cell death. These results have paved the way for clinical trials in humans to test IL-18’s safety and efficacy as a novel treatment for neovascular AMD, most likely as a combination therapy or as an adjunct to anti-VEGF therapy. (ARVO Abstract #2596)
Last year, Campbell won the prestigious President of Ireland Young Researcher Award from Science Foundation Ireland, for the research program he has established at TCD. He now has his own lab at Smurfitt Institute of Genetics, where the team is based, and was awarded a 2015-17 BrightFocus grant to explore ways to manipulate the blood-brain barrier to remove toxic waste from the brain in Alzheimer’s disease.
Genetic risk of AMD develops slowly, over decades.
Sarah Melissa Jacobo, PhD, is a postdoctoral fellow working in the lab of 2014-16 BrightFocus grantee Darlene Dartt, PhD, of Schepens Eye Research Institute, Harvard. A molecular biologist and biochemist by training, Jacobo is working to “decode” the disease pathway to AMD.
Whereas a decade ago, people were asking what genetic mutations contribute to AMD, “now, the challenge is to investigate their function,” she said. “We’re looking at the most prevalent polymorphisms, and asking how do they put brakes on the function of otherwise protective mechanisms in the cells?”
Specifically, they are looking at polymorphisms (SNPs) in a gene known as high temperature requirement A1 (HtrA1), and the impact of these small gene variants, known as single nucleotide polymorphisms, on RPE cells, which is believed to be where AMD begins.
HtrA1 mutations are one of the strongest known risk factors for AMD. Anywhere from 30-60 percent of people with AMD have one of two [HtrA1] variants at birth, but the consequences in the eye don’t manifest until the fifth or sixth decade. It is then when the SNP makes them up to eight-fold more susceptible to AMD, particularly if their lifestyle includes other risk factors such as smoking and bright light exposure.
“The RPE are specialized cells that are critical for the survival and function of light-sensing photoreceptors. I am interested in the machinery and processes within RPE that are essential for protein quality control, and how these components may go awry during normal aging and in AMD,” Jacobo says. “In this study, I focus on RPE-related functions of HTRA1, a gene that is frequently variant in AMD patients. Using cultured RPE, I mimic physiological conditions that stress on the RPE, and examine whether non-variant HtrA1 versus AMD-linked HtrA1 variants are protective or detrimental during these stressful conditions. My current data point to a role for HtrA1 as a pro-survival factor. It’s something that happens early, but proceeds quite slowly.”
Jacobo, Dartt, and Andrius Kazlauskas, PhD, a collaborator at Harvard, believe that HTRA1 may serve a “chaperone” function. Chaperones are proteins that assist other proteins in achieving their final, functional shape, and play an important role in regulating protein synthesis and degradation.
As someone who’s just getting started in the field, Jacobo was happy to learn her paper (coauthored with Kazlauskas) had been selected as a Hot Topic. The research could lead to new therapies aimed at correcting the defect. “Our ability to detoxify those misfolded proteins will make a difference,” Jacobo promises. And possibly not only for AMD, but for several well-known age-related disorders where protein misfolding plays a role, including Alzheimer’s, Parkinson’s, and Huntington’s diseases. (ARVO Abstract #2596)
Just as with Alzheimer’s disease (AD) and other diseases of aging, “current knowledge suggests that the development of AMD likely involves the abnormal build-up of amyloid-beta (Aβ) proteins in the eye,” said Parthasarathy, who earned her PhD under Dr. Pepperberg’s mentorship and was giving her first ARVO talk.
Whereas in AD, abnormal Aβ levels lead to plaque formation, in AMD it is believed to collect within drusen and to trigger a pro-inflammatory response that harms the retinal pigmented epithelial (RPE) cells which nourish and protect the retina.
“Neprilysin, an enzyme produced in many healthy tissues, acts to break down Aβ,” Parasarthy reported. In an animal model, they have tested whether an engineered form of neprilysin was successful in reducing Aβ levels in eye tissue after being delivered through intravitreal injections to the eye.
“Our findings indicate substantial Aβ reduction,” Dr. Parasarathy summarized. “If further research studies support the efficacy and safety of neprilysin delivered in this fashion, it could lead to clinical testing of intra-ocular neprilysin treatment as a means of slowing or blocking the progress of AMD.” (ARVO Abstract #3991)
For their BrightFocus grant, Pepperberg et al have designed experiments that are specifically aimed at comparing two different methods of introducing neprilysin into the mouse eye. The first of these is to access the target eye tissues by directly injecting small volumes of neprilysin-containing solution into the vitreous compartment of the eye, in much the same way that certain drugs used in clinical ophthalmology are delivered to the eye. The second method is a gene therapy approach, the objective of which is to produce expression of neprilysin in the eye by delivering viral particles to the eye that carry the peptidase gene. Results will set the stage for further development of these novel technologies as potential clinical therapies.
Amyloid accumulation represents an interesting link between diseases o f mind and sight. In addition to serving as a point of attack to treat both AD and AMD, some think that detecting abnormal Aβ in the eye may provide a window to diagnosing early AD.
National Glaucoma Research Hot Topics
Is glaucoma a brain disease?
It’s been the focus of 2013-15 BrightFocus grantee Kevin Chan, PhD (University of Pittsburgh) to explore whether the visual brain, in addition to the eye, are affected by the early degenerative mechanisms of glaucoma. He’s using new structural, metabolic, and functional magnetic resonance imaging (MRI) techniques (developed with co-PIs Joel Schuman, MD, and Ian Conner, MD, PhD) to make whole-brain, non-invasive and repeated measurements over a period of time to evaluate the damage to the visual pathway and disease progression under different levels of chronic high eye pressure and drug treatment.
Cindy Teng, a medical student and Chan’s lab assistant on the project, had her abstract selected as a Hot Topic. “Our studies suggest that degeneration of the optic nerve may occur before patients show vision impairment,” she said. “In this study, we measured brain activity with functional MRI, cells layers in the eye with optical coherence tomography (OCT), and degree of vision loss with Humphrey’s visual field assessment.” Results in patients with advanced and early glaucoma were compared with those without visual impairment.
Their research into the eye-brain connection in glaucoma could potentially lead to more timely intervention and targeted treatments to protect the optic nerve and brain. (ARVO Abstract #1697)
Do cells consume themselves to survive glaucoma?
Paloma B Liton, PhD, and co-PI Molly Walsh, MD, both of Duke University, held a 2012-14 BrightFocus grant to investigate whether autophagy, a form of degradation cells use to rid themselves of unwanted substances, is a cellular response used to protect the optic nerve against chronic high eye pressure in glaucoma. In autophagy (which literally from the Greek translates as “self-eating” ), unwanted contents are isolated from the rest of the cell within a double-membraned vesicle known as an autophagosome, which then fuses with a lysosome (a cell filled with enzymes that can dissolve almost any material as part of waste disposal), which breaks down and recycles the contents. Sometimes autophagy can be an adaptive response to disease and/or stress in an organisms, thus promoting survival, while at other times it can lead to cell morbidity and death.
Her research showed that both autophagy and chaperone-assisted autophagy (a specific type of autophagy induced by tension), are part of an integrated response triggered in TM cells in response to strain and exerts a dual role in repair and mechanotransduction. “We hypothesize that dysregulation of this response contributes to the increased stiffness reported in the glaucomatous outflow pathway,” Liton said.
If these protective cellular pathways (autophagy and chaperone-assisted autophagy) could be activated by pharmacological agents, that might constitute a novel therapeutic strategy for glaucoma.
Does anti-VEGF therapy increase risk of glaucoma?
At ARVO, it was his paper on vascular endothelial growth factors (VEGF) and the impact of VEGF and anti-VEGF treatment on aqueous humor outflow, that gained attention as a Hot Topic. It offers a tentative explanation as to why some people with macular degeneration become at higher risk of developing glaucoma.
Currently for glaucoma, "the only treatment is to reduce pressure within the eye,” Overby said; however, “many glaucoma therapies eventually fail to achieve sufficient pressure reduction, giving the disease a second chance to further erode away precious vision.
“To design better glaucoma drugs, we need to target the mechanisms that control eye pressure, but this requires improved understanding of the fluid drainage from the eye. The fluid that fills the front part of the eye is not stagnant, but undergoes constant turnover, draining through a porous tissue known as the trabecular meshwork (TM). Like all d rains, it can get clogged, and an unidentified blockage in the TM often is the cause of elevated eye pressure in glaucoma.
“Our research has shown that VEGF, a molecule that controls fluid turnover elsewhere in the body, regulates fluid drainage through the TM of mice. Human TM cells also secrete VEGF, possibly as part of a feedback loop to regulate drainage and eye pressure. In mice and in humans, blocking VEGF activity appears to inhibit fluid drainage, which may explain why some patients receiving anti-VEGF therapy for retinal disease experience elevated eye pressure that puts them at risk for glaucoma.”
BrightFocus Scientific Review Committee member Rand Allingham, MD, of Duke University, is a coauthor. This work was not funded by BrightFocus. (ARVO Abstract #3542)
Novel measurements track glaucoma changes
Arthur Sit, MD, of Mayo Clinic College of Medicine in Rochester, MN, is a member of the NGR Scientific Review Committee and an expert in measuring pressure and tissue changes in the eye related to glaucoma. His most recent BrightFocus grant (2010-13,with co-PI Jay McLaren, PhD) was to develop a technique for measuring venous pressure in human eyes as a factor that can affect (IOP).
At ARVO, his Hot Topic presentation involved a paper he coauthored with McLaren and others on another novel measurement technique, in this case to determine Young’s modulus (a formula for elasticity) as a biomechanical property of the eye and something that could be important for understanding the risk of glaucoma. Their study calculated Young’s modulus in normal human eyes from the speed of mechanical wave propagation through the cornea.
“The risk for glaucoma and other ocular diseases is likely related to the biomechanical properties (stiffness) of the tissues in the eye. However, there is no method available to measure these properties in patients. In this study, we developed and tested a novel, non-invasive technique that enables the calculation of tissue stiffness based on measurement of the speed of gentle vibrations traveling through the eye. Our values for tissue stiffness were similar to tissue stiffness measured directly in previous studies of cadaver eyes. As well, we found that stiffness was related to eye pressure. This technique could potentially provide a clinical method of measuring tissue properties in patients,” Dr. Sit said about the study.
The results may help explain mechanical deformation of the optic disc during IOP changes. Further work is required to determine if elasticity is altered in glaucoma patients, as well as in other ocular diseases.
This work was not directly supported by BrightFocus. (ARVO Abstract #2596)