Stem Cell Injections for AMD

By Leesha Lentz

Although treatment with stem cells is not yet a viable treatment for age-related macular degeneration, its prospects hold promise for researchers.

According to a recent study by researchers at the Cedars-Sinai Board of Governors Regenerative Medicine Institute, adult-derived human stem cell injections into the eye may slow or even reverse vision loss caused by early-stage age-related macular degeneration (AMD). Currently, there are no known treatments for slowing the progression of the disease, which makes this research so promising for the more than 15 million Americans affected by AMD.

The study "Human iPSC-Derived Neural Progenitors Preserve Vision in an AMD-like Model," posted online ahead of print in the journal STEM CELLS used a preclinical AMD-like rat model. When the rats were injected with stem cells, their vision was preserved for 130 days, "which roughly equates to 16 years in humans," as stated in the Cedars-Sinai press release.

What Is AMD?
AMD is the No. 1 cause of vision loss in adults aged 60 and over, and it progresses with age, according to AMD.org, a website offering information and tools to those living with AMD. In fact, AMD.org estimates that "more than one person in three can develop signs of age-related macular degeneration, with over 200,000 new cases diagnosed every year."

The disease damages the macula, a small spot in the retina, which affects central vision. While AMD does not result in total blindness, the National Eye Institute of the National Institutes of Health states on its website that the loss of central vision can negatively impact daily functioning, "such as the ability to see faces, drive, read, write, or do close work, such as cooking or fixing things around the house." While there are some rehabilitation services and special devices such as magnifiers to aid patients with AMD, there is no cure, which is especially sobering for patients since the disease worsens over time.

"Macular degeneration, when you first present with it, begins with a certain amount of loss and it gets worse and worse over time. It's age-related and it's obviously older adults who get it," says Clive Svendsen, PhD, director of the Board of Governors Regenerative Medicine Institute and contributing author to the study. Therefore, it's important to help slow or prevent the disease in its earliest stages while patients still have reasonable vision, he says.

How Stem Cells Work
For the study, researchers used and developed induced neural progenitor stem cells. "We can take adult tissue so, for example, a skin fibroblast or a skin cell from any aged patient, up to 100 years old we've done, and put it in the petri dish, and expose the cell to a single protein that sends it back in time to more or less an embryonic state," Svendsen explains. "So once they're in that embryonic state, we call them induced pluripotent stem cells. They're essentially immortal and can grow forever. We can bank and store millions of those cells, and they can be pushed forward to be neural stem cells, or neural progenitor cells as we call them. These are cells that can be injected into the eye to slow macular degeneration."

Cedar-Sinai researchers in the David and Jane Pollak Induced Pluripotent Stem Cell Laboratory are among the leading groups in the country converting adult human skin cells into induced pluripotent stem cells, which "can be expanded indefinitely and then made into any cell of the human body," according to its press release. For the current study, these stem cells were transitioned into induced neural progenitor cells, which have been shown to prevent vision loss.

Once injected, these healthy cells form a protective layer around the retina. "When you put them in under the retina, they migrate into areas of damage, such as the macula," Svendsen says. "They will actually form a little layer that protects the ongoing degeneration. It kind of rejuvenates the back of the eye in that way."

In the study's abstract, researchers reported that retinas protected by induced pluripotent stem cells were 140-fold more sensitive to light stimulation than equivalent areas. Svendsen says that rats that didn't have the injection essentially became blind. With such results, the researchers suggested that stem cells can be applied to therapeutic utility in early-stage AMD.

Possible Treatment Option in AMD Patients?
While these results suggest a possible treatment for patients with early-stage AMD, the researchers caution that the stem cells need to be tested for toxicity and safety before moving on to clinical trials. "The caution here is that we used a model in the rats and it's the closest thing that we could get to retinal degeneration. There is no human model of macular degeneration where we can guarantee that this will be the same in human beings," Svendsen says. "Mice and rats don't get true macular degeneration. The caution is we don't know how these cells will react in humans or how they'll work in the actual disease themselves, so that's why we're going to apply to the FDA to do a small clinical trial to test the safety of the cells and to see if they have an initial effect."

Shaomei Wang, MD, PhD, lead author of the study and a research scientist in the Eye Program at the Cedars-Sinai Board of Governors Regenerative Medicine Institute, says it's also important to test the stem cell injection in the long term. "We need to make sure these cells after injection do not have any binding effects, such as being toxic or forming a tumor. So we need to perform safety studies."

When asked about a projected timeline when this treatment may be offered, neither Wang nor Svendsen was able to offer an estimate. Wang says the regulatory process is very complicated, and as mentioned above, there is still a lot of pending research. However, Svendsen notes that there currently are a lot of patient trials with stem cells, and while they use stem cells different from ones used in this study, he says the "eye is turning out to be a leader in stem cell translational therapy because it's easy to access and it's easy to assess vision, whether you protect it or not."

Future Plans
If everything progresses well during the clinical trials, Svendsen believes the procedure to treat early-stage AMD in patients could be a relatively simple one. "It's kind of an outpatient procedure: local anesthetic to the eye, inject the cells, and the patient can go back home. The one-time injection of the cell will get to work," he says.

The impact of the one-time stem cell injection could be enormous, as it may protect the eye for long periods of time without requiring any other medication, according to Svendsen. This may lower costs both to the patients as well as the hospital.

In the meantime, with this promising research on the horizon, it's important for physicians working with older adult populations to recommend their patients get their eyes checked regularly by an eye care professional. Although there may not be visible symptoms for early-stage AMD, Svendsen says the disease is prevalent. The National Eye Institute provides a list of eye exams that may detect AMD, as well as further information about possible vision devices to aid patients in their day-to-day activities. In addition, AMD.org offers practical tips and advice to patients living with the disease, including a free AMD toolkit and a list of support groups.

— Leesha Lentz is a freelance writer based in Pottstown, Pennsylvania.