CRISPR-Cas9 can be delivered directly into the eye of living animals to treat age-related macular degeneration efficiently and safely
IBS study proves that CRISPR-Cas9 can be delivered directly into the eye of living animals to treat age-related macular degeneration efficiently and safely.
It is estimated that almost one in every ten people over 65 has some signs of age-related macular degeneration (AMD), and its prevalence is likely to increase as a consequence of the aging population. AMD is a form of blindness, common in Caucasians, which causes distorted vision and blind spots. Scientists at the Center for Genome Engineering, within the Institute for Basic Science
(IBS) report the use of CRISPR-Cas9 in performing “gene surgery” in the layer of tissue that supports the retina of living mice. Published in Genome Research, this study combines basic research and mouse model applications.
The most common retinopathies causing blindness are ‘retinopathy of prematurity’ in children, ‘diabetic retinopathy’ and ‘AMD’ in older adults. In these diseases, abnormally high levels of the Vascular Endothelial Growth Factor (VEGF) are secreted. In AMD, VEGF causes the formation of new blood vessels in the eyes but also leads to leakages of blood and fluid into the eye, damaging an area at the center of the retina called macula.
Injections of anti-VEGF drugs are the most common treatment against AMD, but at least seven injections per year are required, because VEGF is continuously overexpressed by the cells of the diseased retinal pigment epithelium. Instead of such invasive treatments, IBS scientists believe that gene therapy with the third generation gene editing tool CRISPR-Cas9 could improve the situation. “The injections tackle the effects, but not the main cause of the problem. By editing the VEGF gene, we can achieve a longer-term cure,” explains KIM Jin-Soo, Director of the Center for Genome Engineering.
CRISPR-Cas9 can precisely cut and correct DNA at the desired site in the genome. The CRISPR-Cas9 system works by cutting DNA at a target site, in this case, inside the VEGF gene. Two year ago, IBS scientists proved that a pre-assembled version of CRISPR-Cas9, a.k.a, Cas9 ribonucleoprotein (RNP), can be delivered to cells and stem cells to modify target genes. The pre-assembled complex works rapidly and degrades before the body has time to build up an immune response against it. Despite these advantages and previous successes, the difficulty in delivering pre-assembled CRISPR-Cas9 has limited its use in therapeutic applications.
In this study, the research team successfully injected CRISPR-Cas9 into the eyes of a mice model with wet AMD and locally modified the VEGF gene. Initially they found that the delivery of the pre-assembled CRISPR-Cas9 complex is more efficient that the delivery of the same components in a plasmid form. Secondly, the complex disappeared after just 72 hours. Scientists assessed the whole genome of the animals and found the CRISPR-Cas9 complex modified only the VEGF gene and did not affect other genes. The progression of the eye disease was monitored by looking at choroidal neovascularization (CNV), the creation of new blood vessels between the retina and the sclera – a common problem of ‘wet’ macular degeneration – and researchers found the CNV area reduced by 58%. Moreover, a likely side effect, namely cone dysfunction, that takes only 3 days to show in these mice, did not occur a week after the treatment.
“We have developed a treatment to suppress CNV by inactivating the VEGF gene, one of the causes of AMD. We envision that, in the future, surgeons will be able to cut and paste disease-causing genetic elements in patients,” explains Kim Jin-Soo.
While CRISPR-Cas9 is conventionally used to correct mutations causing hereditary diseases or cancer, this study suggests a new therapy for non-hereditary degenerative disease.”We believe that this is a new therapeutic modality for the treatment of non-hereditary degenerative diseases,” points out Professor KIM Jeong Hun (Seoul National University), “We confirmed the effect on the animal models of the disease and now we wish to continue with preclinical trials.”
Eye diseases such as diabetic retinopathy and age-related macular degeneration are among the leading causes of irreversible vision loss and blindness worldwide. Currently, gene therapy can be administered to treat these conditions — but this requires an injection. Now researchers report in the journal ACS Applied Materials & Interfaces a new way to deliver the treatment topically, without a needle.
The rear part of the eye is where conditions such as proliferative diabetic retinopathy and age-related macular degeneration develop. And they involve a substance called vascular endothelial growth factor, which stimulates the growth of blood vessels. Scientists have been trying to inhibit the growth factor using gene therapy, but delivering drugs to the back of the eye currently requires an injection. Not surprisingly, few patients opt for this type of treatment. Gang Wei and colleagues wanted to find a noninvasive approach.
Boosting the potency of a broccoli-related compound yields a possible treatment for age-related macular degeneration
Buck researchers boosted the potency of a broccoli-related compound by ten times and identified it as a possible treatment for age-related macular degeneration (AMD), the leading cause of vision loss affecting more than 10 million older Americans.
The research, published in Scientific Reports, also highlights the role of lipid metabolism in maintaining the health of the retina, reporting that palmitoleic acid also had protective effects on retinal cells in culture and in mice.
The “good-for-you” compound in broccoli which prompted the inquiry is indole-3-carbinol (I3C), which is currently being studied for cancer prevention. I3C helps clear cells of environmental toxins by activating the aryl hydrocarbon receptor (AhR) protein which upregulates pathways involved in chemical detoxification. AhR, which declines with age, is important for detoxifying the retina. Previous studies show that AhR-deficient mice develop a condition which looks extremely similar to AMD. When contemplating the possibility of boosting AhR via broccoli’s I3C, Buck faculty and lead author Arvind Ramanathan, PhD, knew there was a challenge – I3C is weak activator of AhR. So he used the chemical scaffold of I3C to do a ‘virtual’ screen of a publicly-available database of millions of compounds to find those that were related to I3C but would bind to AhR with more strength. His team came up with 2,2?-aminophenyl indole (2AI) which is ten times more potent than I3C.
“2AI protected human retinal cells in culture from stress,” said Ramanathan. “And it also protected retinal cells in mice from light-mediated damage. We are very excited about the potential for 2AI and look forward to developing it further.” Ramanathan is also excited about the possibility of finding more potent versions of other naturally occurring molecules that show health benefits for age-related diseases. “You would have to eat an unreasonable amount of broccoli and other cruciferous vegetables to get enough of a protective effect to impact AMD,” he said. “This method allows us to capitalize on nature’s wisdom to find related molecules that can deliver therapeutic benefit.”
An injection of stem cells into the eye may soon slow or reverse the effects of early-stage age-related macular degeneration, according to new research from scientists at Cedars-Sinai
Currently, there is no treatment that slows the progression of the disease, which is the leading cause of vision loss in people over 65.
“This is the first study to show preservation of vision after a single injection of adult-derived human cells into a rat model with age-related macular degeneration,” said Shaomei Wang, MD, PhD, lead author of the study published in the journal STEM CELLS and a research scientist in the Eye Program at the Cedars-Sinai Board of Governors Regenerative Medicine Institute.
The stem cell injection resulted in 130 days of preserved vision in laboratory rats, which roughly equates to 16 years in humans.
Age-related macular degeneration affects upward of 15 million Americans. It occurs when the small central portion of the retina, known as the macula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye. Macular degeneration may also be caused by environmental factors, aging and a genetic predisposition.
When animal models with macular degeneration were injected with induced neural progenitor stem cells, which derive from the more commonly known induced pluripotent stem cells, healthy cells began to migrate around the retina and formed a protective layer. This protective layer prevented ongoing degeneration of the vital retinal cells responsible for vision.