Using stem cells to fix bad behavior in the brain

 

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Gladstone Institutes Steven Finkbeiner and Gaia Skibinski: Photo courtesy Chris Goodfellow, Gladstone Institutes

Diseases of the brain have many different names, from Alzheimer’s and Parkinson’s to ALS and Huntington’s, but they often have similar causes. Researchers at the Gladstone Institutes in San Francisco are using that knowledge to try and find an approach that might be effective against all of these diseases. In a new CIRM-funded study, they have identified one protein that could help do just that.

Many neurodegenerative diseases are caused by faulty proteins, which start to pile up and cause damage to neurons, the brain cells that are responsible for processing and transmitting information. Ultimately, the misbehaving proteins cause those cells to die.

The researchers at the Gladstone found a way to counter this destructive process by using a protein called Nrf2. They used neurons from humans (made from induced pluripotent stem cells – iPSCs – hence the stem cell connection here) and rats. They then tested these cells in neurons that were engineered to have two different kinds of mutations found in  Parkinson’s disease (PD) plus the Nrf2 protein.

Using a unique microscope they designed especially for this study, they were able to track those transplanted neurons and monitor what happened to them over the course of a week.

The neurons that expressed Nrf2 were able to render one of those PD-causing proteins harmless, and remove the other two mutant proteins from the brain cells.

In a news release to accompany the study in The Proceedings of the National Academy of Sciences, first author Gaia Skibinski, said Nrf2 acts like a house-cleaner brought in to tidy up a mess:

“Nrf2 coordinates a whole program of gene expression, but we didn’t know how important it was for regulating protein levels until now. Over-expressing Nrf2 in cellular models of Parkinson’s disease resulted in a huge effect. In fact, it protects cells against the disease better than anything else we’ve found.”

Steven Finkbeiner, the senior author on the study and a Gladstone professor, said this model doesn’t just hold out hope for treating Parkinson’s disease but for treating a number of other neurodegenerative problems:

“I am very enthusiastic about this strategy for treating neurodegenerative diseases. We’ve tested Nrf2 in models of Huntington’s disease, Parkinson’s disease, and ALS, and it is the most protective thing we’ve ever found. Based on the magnitude and the breadth of the effect, we really want to understand Nrf2 and its role in protein regulation better.”

The next step is to use this deeper understanding to identify other proteins that interact with Nrf2, and potentially find ways to harness that knowledge for new therapies for neurodegenerative disorders.

Translating great stem cell ideas into effective therapies

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CIRM funds research trying to solve the Alzheimer’s puzzle

In science, there are a lot of terms that could easily mystify people without a research background; “translational” is not one of them. Translational research simply means to take findings from basic research and advance them into something that is ready to be tested in people in a clinical trial.

Yesterday our Governing Board approved $15 million in funding for four projects as part of our Translational Awards program, giving them the funding and support that we hope will ultimately result in them being tested in people.

Those projects use a variety of different approaches in tackling some very different diseases. For example, researchers at the Gladstone Institutes in San Francisco received $5.9 million to develop a new way to help the more than five million Americans battling Alzheimer’s disease. They want to generate brain cells to replace those damaged by Alzheimer’s, using induced pluripotent stem cells (iPSCs) – an adult cell that has been changed or reprogrammed so that it can then be changed into virtually any other cell in the body.

CIRM’s mission is to accelerate stem cell treatments to patients with unmet medical needs and Alzheimer’s – which has no cure and no effective long-term treatments – clearly represents an unmet medical need.

Another project approved by the Board is run by a team at Children’s Hospital Oakland Research Institute (CHORI). They got almost $4.5 million for their research helping people with sickle cell anemia, an inherited blood disorder that causes intense pain, and can result in strokes and organ damage. Sickle cell affects around 100,000 people in the US, mostly African Americans.

The CHORI team wants to use a new gene-editing tool called CRISPR-Cas9 to develop a method of editing the defective gene that causes Sickle Cell, creating a healthy, sickle-free blood supply for patients.

Right now, the only effective long-term treatment for sickle cell disease is a bone marrow transplant, but that requires a patient to have a matched donor – something that is hard to find. Even with a perfect donor the procedure can be risky, carrying with it potentially life-threatening complications. Using the patient’s own blood stem cells to create a therapy would remove those complications and even make it possible to talk about curing the disease.

While damaged cartilage isn’t life-threatening it does have huge quality of life implications for millions of people. Untreated cartilage damage can, over time lead to the degeneration of the joint, arthritis and chronic pain. Researchers at the University of Southern California (USC) were awarded $2.5 million to develop an off-the-shelf stem cell product that could be used to repair the damage.

The fourth and final award ($2.09 million) went to Ankasa Regenerative Therapeutics, which hopes to create a stem cell therapy for osteonecrosis. This is a painful, progressive disease caused by insufficient blood flow to the bones. Eventually the bones start to rot and die.

As Jonathan Thomas, Chair of the CIRM Board, said in a news release, we are hoping this is just the next step for these programs on their way to helping patients:

“These Translational Awards highlight our goal of creating a pipeline of projects, moving through different stages of research with an ultimate goal of a successful treatment. We are hopeful these projects will be able to use our newly created Stem Cell Center to speed up their progress and pave the way for approval by the FDA for a clinical trial in the next few years.”

What’s Fat Got to do With Alzheimer’s?

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(Image credit: FineCooking.com)

Diets these days are a dime a dozen, and dietary trends come and go. First eggs were “out” because they contain cholesterol, but now they are back “in” because we now know that some types of cholesterol can be actually good for the body. Then there was the era of “fat-free” or “reduced-fat” foods. This was all the rage in the 90s until scientists realized that eliminating healthy fats from your diet can have negative consequences on your health.

The theories behind different diets evolve constantly much like the theories behind complicated neurodegenerative diseases like Alzheimer’s disease (AD). Alzheimer’s is a debilitating disease that slowly robs patients of their minds, leaving them as shadows of their former selves. AD affects 47.5 million people globally with 7.7 million new patients diagnosed every year, thus making the disease one of the most important unmet medical needs to be addressed.

The causes of AD have eluded scientists for over a century. However, the main theory behind what causes AD involves the buildup of toxic proteins in the brain. These proteins accumulate to form structures called plaques and tangles that impair brain function and kill off brain cells.

Unfortunately, there is no cure for AD or treatments to stop its progression. This sobering fact is not due to a lack of effort by scientists and pharmaceutical companies. Dozens of drug therapies have or are being tested in clinical trials, many of them focusing on the removal of toxic protein levels in people with the disease. While there have been some pretty dramatic failures in these trials, a few are starting to show encouraging results.

Link Between Abnormal Fat Metabolism and Alzheimer’s Disease

Now, a new theory on AD involving the build up of toxic fat molecules in the brains of AD patients has been thrown into the mix. In a study published Thursday in Cell Stem Cell, scientists from Montreal reported the presence of fat droplets in AD patient brains in areas surrounding brain stem cells. Brain stem cells are responsible for growing new brain cells (such as nerves) and maintaining overall brain function and health. The scientists discovered that the fat droplets actually prevented the regenerative abilities of the brain stem cells, leading them to believe that the accumulation of fat droplets in the brain could be a cause of AD.

Fat is used as an energy source by cells and organs in the body in a process called “fatty acid metabolism”. Fat metabolism is very important for proper brain development but also in maintaining brain health and function in adults. Problems with fat metabolism in humans can cause diseases such as obesity, diabetes, and heart disease. So one can imagine that problems with fat metabolism in the brain could also have serious consequences.

In this study, scientists used a genetic mouse model of AD that had a “triple-threat” of genetic mutations that cause AD in humans. They studied the brain stem cells in these mice and found that the support cells surrounding the stem cells were full of fat droplets. They also noticed that when the fat droplets were present, the brain stem cells were not dividing to generate new brain cells (which is a common defect associated with AD). When they looked at brain tissue from nine AD patients, they also observed a similar pattern of an increased concentration of fat droplets surrounding areas of brain stem cells compared to healthy human brain tissue.

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AD patient brains (lower panel) have more fat droplets shown in red than normal healthy brains (upper panel). (Hamilton et al., 2015)

Using a fancy science technique called mass spectrometry, the scientists found that the fat droplets were made up of a fat triglyceride called oleic acid, which is a common component of vegetable and animal fats. To prove that oleic acid was bad for brain stem cells, they took normal healthy mice and injected oleic acid into their brains. They observed that adding this fat negatively affected the stem cells’ regenerative ability to divide. Going one step further, the scientists used drugs to block the formation of oleic acid in their AD mouse model, and saw that removing this fat allowed the brain stem cells to divide and function properly.

The major conclusions generated from this study were summarized nicely by senior author Karl Fernandes in a news release:

We discovered that these fatty acids are produced by the brain, that they build up slowly with normal aging, but that the process is accelerated significantly in the presence of genes that predispose to Alzheimer’s disease. In mice predisposed to the disease, we showed that these fatty acids accumulate very early on, at two months of age, which corresponds to the early twenties in humans. Therefore, we think that the build-up of fatty acids is not a consequence but rather a cause or accelerator of the disease.

 

Don’t Count Your Chickens Just Yet

While this study suggests that fat accumulation in the brain is a cause of AD, more research will need to be done to confirm that abnormal fat metabolism is the culprit. Some experiments can be done quickly such as treating their AD mouse model with the drugs that block the formation of the “bad fat” and monitoring them for an extended time period to see if blocking oleic acid accumulation prevents the onset of AD symptoms like memory loss. Other experiments, such as therapeutically targeting abnormal brain fat deposits in human, will be more long term projects with unknown results.

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Dr. Alois Alzheimer

Nontheless, this study nicely ties back to an observation by Dr. Alois Alzheimer who first reported about AD in 1906 . When he dissected the brains of AD patients who had passed away, he found five major pathologies that distinguished their brains from healthy brains. One of these traits was an increased concentration of fat droplets. Thus findings from Fernandes and his group revive a century old notion that fat metabolism could be a cause of AD and open doors for the development of new therapeutic strategies to fight AD.


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2015 Golden Globes shines light on Alzheimer’s and ALS with acting awards

In between the one-liners, surprise presenters and bottomless champagne, something remarkable happened at last night’s 72nd Golden Globe Awards.

26 awards were given last night to the best in film and television. But two in particular were especially meaningful.

Julianne Moore plays a professor grappling with Alzheimer's in Still Alice [Credit: Sony Pictures Classics]

Julianne Moore plays a professor grappling with Alzheimer’s in Still Alice [Credit: Sony Pictures Classics]

I am referring, of course, to Julianne Moore and Eddie Redmayne, who each took home awards in the lead acting categories for their portrayals of two individuals suffering from neurodegenerative diseases. Their wins not only solidified them as front-runners for the Academy Awards ceremony next month, but also gave millions of viewers a deeply intimate look at two unforgiving illnesses.

Eddie Redmayne as Stephen Hawking in The Theory of Everything [Credit: Focus Features]

Eddie Redmayne as Stephen Hawking in The Theory of Everything [Credit: Focus Features]

Renowned actress Julianne Moore was the first of the two to receive her award, winning for her role as Alice Howland, a Columbia linguistics professor diagnosed with Early-Onset Alzheimer’s disease, in the film Still Alice.

And later in the program the Globes honored Eddie Redmayne for his brilliant portrayal of Professor Stephen Hawking—a long-time sufferer of the motor neuron disease ALS—in the biopic The Theory of Everything.

These two films were particularly poignant for those in the Alzheimer’s and ALS communities—as they reveal in stark, sometimes disturbing detail, how these diseases wreak havoc on the brain and nervous system. In preparation for their roles, each spent several months speaking with patients and clinicians who see and live with the diseases every day.

For example, Moore spoke with women who—like her character Alice—were living with Early-Onset Alzheimer’s, giving her first-hand knowledge of not only how the disease affects them, but also how their families are affected.

Meanwhile, Redmayne spent significant time with Hawking himself, learning about his unique experience as a long-time ALS patient. In interviews Redmayne has said that Hawking was often present during filming. The time the two individuals spent with each other clearly paid off, and had a remarkable impact on the actor.

“It is a great privilege for me to be in this room,” Redmayne said during his Golden Globe acceptance speech. “Getting to spend time with Stephen Hawking … was one of the great, great honors of my life.”

The fact that the two lead acting awards put spotlight on these diseases was not lost on the patient advocacy communities. For example, Maria Shriver tweeted shortly after the awards ceremony:

Shriver Tweet

Shriver’s statement underscores the stark reality of awareness, or lack thereof, for neurodegenerative diseases. Here at CIRM, we are laser focused on supporting ground-breaking work in regenerative medicine that can slow, halt or even reverse these conditions. We are hopeful that these two actors’ stellar performances can help put a human face on conditions that are all too-often reduced to numbers.

This hope has thus far translated to these films’ audiences. For example, said one review of Still Alice from the New York Post:

Still Alice … presents a disease that can devastate any family, anywhere, with unsparing truth and great compassion.”

Read more about how regenerative medicine can change the face of Alzheimer’s and ALS on our Stories of Hope.

Bringing out the Big Guns: Scientists Weigh in on How Best to Combat Deadly Diseases of the Brain

Despite our best efforts, diseases of the brain are on the rise. Neurodegenerative conditions such as Alzheimer’s and Parkinson’s diseases threaten not only to devastate our aging population, but also cripple our economy. Meanwhile, the causes of conditions such as autism remain largely unknown. And brain and spinal cord injuries continue to increase—leaving their victims with precious few options for improving their condition.

This special review issue of addresses some of the key challenges for translational neuroscience and the path from bench to beside. [Credit: Cell Press]

This special review issue of Neuron addresses some of the key challenges for translational neuroscience and the path from bench to beside. [Credit: Cell Press]

We need to do better.

The scientific community agrees. And in a special issue of the journal Neuron, the field’s leading researchers lay out how to accelerate much-needed therapies to the many millions who will be affected by brain disease or injury in the coming years.

The journal’s leadership argues that now is the time to renew efforts in this field. Especially worrying, say experts, is the difficulty in translating research breakthroughs into therapies.

But Neuron Editor Katja Brose is optimistic that the answers are out there—we just need to bring them to light:

“There is resounding agreement that we need new approaches and strategies, and there are active efforts, discussion and experimentation aimed at making the process of therapeutic development more efficient and effective.”

Below are three papers highlighted in the special journal, each giving an honest assessment of how far we’ve come, and what we need to do to take the next step.

Fast-tracking Drug Development. In this perspective, authors from the Institute of Medicine (IOM) and the Salk Institute—including CIRM grantee Fred Gage—discuss the main takeaways from an IOM-sponsored workshop aimed at finding new avenues for accelerating treatments for brain diseases to the clinic.

The main conclusion, according to the review’s lead author Steve Hyman, is a crucial cultural shift—various stakeholders in academia, government and industry must stop thinking of themselves as competitors, but instead as allies. Only then will the field be able to successfully shepherd a breakthrough from the lab bench and to the patient’s bedside.

Downsized Divisions’ Dangerous Effects. Next, an international team of neuroscientists focuses their perspective on the recent trend of pharmaceutical companies to cut back on funding for neuroscience research. The reasoning: neurological diseases are far more difficult than other conditions, and proving to be too costly and too time-consuming to be worth continued effort.

The solution, says author Dennis Choi of State University of New York Stonybrook, is a fundamental policy change in the way that market returns of neurological disease drug development are regulated. But Choi argues that such a shift cannot be achieved without a concerted effort by patient advocates and nonprofits to lead the charge. As he explains:

“The broader neuroscience community and patient stakeholders should advocate for the crafting and implementation of these policy changes. Scientific and patient group activism has been successful in keeping the development of therapies in other areas—such as HIV and cancer—appropriately on track, but this type of sector-wide activism would be a novel step for the neuroscience community.”

Indeed, here at CIRM we have long helped support the patient community—a wonderful collection of individuals and organizations advocating for advances in stem cell research. We are humbled and honored that so many patients and patient advocates have stepped forward as stem cell champions as we move towards the clinic.

The Road to Preclinical Diagnosis. Finally, we hear from Harvard University neuroscientists highlighting how far the research has come—even in the face of such extraordinary difficulty.

Specifically focused on Alzheimer’s disease, the authors touch on the discoveries of protein markers, such as amyloid-beta and tau, that serve as an indicator of neurodegeneration. They make the important point that because Alzheimer’s is almost certainly is present before the onset of physical symptoms, the ultimate goal of researchers should be to find a way to diagnose the disease before it has progressed too far.

“[Here we] highlight the remarkable advances in our ability to detect evidence of Alzheimer’s disease in the brain, prior to clinical symptoms of the disease, and to predict those at greatest risk for cognitive decline,” explained lead author Reisa Sperling.

The common thread between these perspectives, say Neuron editors in an accompanying editorial, is that “by leveraging shared resources, tools and knowledge and approaching these difficult problems collaboratively, we can achieve more together.”

A sentiment that we at CIRM fully support—and one that we will continue to foster as we push forward with our mission to accelerate stem cell-based therapies to patients in need.

Stories of Hope: Alzheimer’s Disease

This week on The Stem Cellar we feature some of our most inspiring patients and patient advocates as they share, in their own words, their Stories of Hope.

Adele Miller knew what came next. She had lived it twice already: her father’s unraveling, due to Alzheimer’s disease, and, a few years later, her mother’s journey through the same erasure of mind and memory. So when doctors told her, at age 55, that she, too, had the disease, she remembered her parents’ difficult last years.

Lauren Miller has seen first hand how Alzheimer's can erase a lifetime's worth of memories.

Lauren Miller has seen first hand how Alzheimer’s can erase a lifetime’s worth of memories.

‘Tell no one,’ she told her family. Keep it secret.

“She was ashamed,” her daughter, actress and writer Lauren Miller, recalls. “She was so embarrassed because there’s such a stigma.” And she worried about her family. How would they handle all this? “I asked her once if she was scared,” Lauren says. “She said she wasn’t afraid for herself. But she was afraid for me, and my dad, and my brother. She knew what she’d gone through with her parents.”

Alzheimer’s disease has been a constant in the actress’s family. Perhaps that made her more attuned to the subtle changes that can herald the onset of the disease. At Lauren’s college graduation, she saw the first clues that something was amiss with her mother. She was repeating herself. Not just, “Oh, have I told you this before?” This was different. A few years later, as she and her mother prepared for a party, Lauren was stunned by the changes in her mother’s behavior. Her mother’s memory no longer seemed to function. She kept forgetting that the taco salad was vegetarian. She kept asking over and over where to throw the garbage. Lauren knew that’s not like her mother, a teacher for 35 years. So she sat down with her brother Dan and their dad. It was time to do something for Mom.

“It’s not that my dad wasn’t noticing things. But I don’t think he wanted to admit there was a problem. And he was simply too close to it,” Lauren says.

It took less than five years for Alzheimer’s disease to rob Adele Miller of nearly everything. Before she turned 60, she couldn’t write. She couldn’t speak. She didn’t even recognize her family.

The loss, the sadness, and the anger that Alzheimer’s families feel is compounded by a sense of utter helplessness against a disease that yields to no drug. But Lauren decided she would not be helpless, and in 2011, she and her husband, actor Seth Rogen, launched Hilarity for Charity, which aims to raise Alzheimer’s awareness in young people while also raising funds for the Alzheimer’s Association. This year Hilarity for Charity sponsored its first college fundraisers. It also hosts support groups for under-40 caregivers.

“Seth has the ability to reach an audience that may not know much about Alzheimer’s. His fans are 16 year old boys who aren’t generally the target for Alzheimer’s awareness,” Lauren said. “But he was able to strike a cord with a lot of these young people. We get emails from people who are 16. ‘Thank you for doing this. I felt alone. Now there’s a voice.’ This is considered an old person’s disease, but it’s really not. It affects everyone.”

In December 2013, Lauren, co-writer, producer and star of For a Good Time, Call, joined the CIRM governing Board, the Independent Citizens Oversight Committee, as a patient advocate for Alzheimer’s disease.

“Alzheimer’s research is woefully underfunded by the government, so it’s important to have bold, innovative approaches like CIRM’s to take research to the next level,” Lauren said. “Stem cell research is at the cusp of something life changing. To me, it’s one of the things closest to making a step toward treatment. I jumped at the opportunity to be part of it.”

For information about CIRM-funded Alzheimer’s disease research, visit our Alzheimer’s Fact Sheet. You can read more about Lauren’s Story of Hope on our website.

Blood Test Reveals Alzheimer’s Disease Risk, CIRM-Funded Study Finds

Could a simple blood test predict your risk for one day developing Alzheimer's disease?

Could a simple blood test predict your risk for developing one day developing Alzheimer’s disease?

By the time someone begins to experience the clinical symptoms of Alzheimer’s disease, the damage has already been done. An accumulation of toxic proteins is causing brain cells to whither and die, taking with them a lifetime of precious memories.

But what if we had a definitive test that could predict one’s risk of developing Alzheimer’s, even before the onset of symptoms? Could we use it to develop an early-detection method and—even more importantly—a way to slow or halt the disease before it is too late?

While this may seem closer to fiction than reality, scientists from the Western University of Health Sciences are reporting that they’ve done just that: a simple blood test that can accurately predict one’s Alzheimer’s risk—up to ten years before symptoms begin to develop.

Reporting in the latest issue of Translational Psychiatry, senior author Dr. Doug Ethell and his research team describe their ingenious method of tracking the earliest stages of Alzheimer’s via a simple blood test.

Their test, called the CD4see assay, tracks the body’s early immune response to toxic proteins—called amyloid beta proteins—that accumulate and form harmful plaques in the brains of Alzheimer’s patients.

Ethell has long been studying how a class of immune cells, called T cells, responds to the buildup of amyloid beta. Previously, he showed that these so-called amyloid beta-specific T cells could actually counter the cognitive decline seen in Alzheimer’s. So, lower amyloid T cell levels should correlate with symptoms. As he explained in an interview:

“If our mouse studies were correct, then there should be fewer of those cells in Alzheimer’s patients. Translating those studies from mouse to man was going to take a big effort—characterizing the small proportion of T cells that respond to amyloid-beta from the millions of other kinds of T cell would require technology that didn’t exist yet.”

So Ethell turned to stem cells. With support from CIRM, Ethell and his team took human embryonic stem cells (hESCs) and developed a type of immune system cell called dendritic cells. These cells stimulated the growth of amyloid-beta T cells—effectively bringing them out of hiding and allowing the researchers to locate and count them.

“Everyone showed a decrease in these T cells as they aged, but the decline occurred earliest in women with the apoE4 gene (the single greatest genetic risk factor for Alzheimer’s), often right around the same time as menopause,” explained Ethell. “When our raw data was pasted on foam boards all over my office it seemed to us that older women had lower responses than men, and when the data was finally plotted the dramatic decline around menopause was clear.”

Interestingly, this observation seems to correlate with the fact that Alzheimer’s is more prevalent in women than in men.

Ethell and his team propose that the CD4see assay could soon be used to measure amyloid-beta-specific T cells against one’s age, sex and whether they carry apoE4. This could then be used to calculate the individual’s risk for developing Alzheimer’s symptoms in the future.

This assay could also prove helpful when looking to test new therapeutic strategies that treat early-stage Alzheimer’s—something that has proven difficult without a reliable early detection method.

“Alzheimer’s disease is a puzzle and every bit of knowledge adds a new piece,” added Ethell. “We now view Alzheimer’s disease very differently than we did even just a few years ago.”

What was Old is New Again: Scientists Transplant Brain Cells into Aged Mice and Reverse Memory Loss

Alzheimer’s disease starts with small, almost imperceptible steps. And then it builds. Sometimes slowly over a period of decades, other times more quickly—in just a matter of years. But no matter the speed of progression, the end outcome is always the same.

Transplanted cells (shown in green) in the hippocampus, 3 months after transplantation.  Cell nuclei are labeled in blue.  [Credit: Leslie Tong and Yadong Huang/Gladstone Institutes]

Transplanted cells (shown in green) in the hippocampus, 3 months after transplantation. Cell nuclei are labeled in blue. [Credit: Leslie Tong and Yadong Huang/Gladstone Institutes]

The sixth leading cause of death in the United State, Alzheimer’s develops as brain cells, or neurons, are destroyed over time. The hippocampus, the brain’s memory center, is the hardest hit, which is why memory loss is the single most common—and most devastating—symptom of the disease.

As a result, scientists have looked to the field of regenerative medicine to replace the vital cells lost to Alzheimer’s. And now, researchers at the Gladstone Institutes in San Francisco have made an important step towards that goal.

Reporting in the latest issue of the Journal of Neuroscience, researchers in the laboratory of Dr. Yadong Huang have successful transplanted early-stage brain cells, called “neuron progenitor cells,” into aged mice that have been modified to mimic Alzheimer’s symptoms. And after doing so, what they saw was extraordinary.

Not only did the cells survive the transplantation—a feat in and of itself—they began to grow and integrate into the molecular circuitry of the brain. And that’s when they noticed changes to the animals’ behavior.

These mice, whose age corresponded to humans in late-stage adulthood, were living with physical signs of memory loss. But after the cell transplants, the team saw signs that memory and learning were restored.

Leslie Tong, a graduate student at Gladstone and the University of California, San Francisco and the paper’s first author, elaborated on the importance of these findings in a news release:

“Working with older animals can be challenging from a technical standpoint, and it was amazing that the cells not only survived but affected activity and behavior.”

For a brain to function normally, there should be a balance between two types of neurons: ‘excitatory’ neurons, that act as the brain’s gas pedal, and ‘inhibitory’ neurons that serve as the brake. If this balance between these two cell types gets thrown out of whack, normal function is disrupted—and cells, especially the inhibitory neurons, degrade and die. Combined with other factors, such as genetic risk and the buildup of toxic proteins—this imbalance plays a key role in the dysfunction that eventually leads to Alzheimer’s.

The success of this treatment not only reveals the importance of maintaining this balance in memory and learning, but is also proof of concept that if neurons are lost—they can in principle be replaced.

Huang is particularly excited about the therapeutic potential of these findings. As he stated in the same news release:

“The fact that we see a functional integration of these cells into the hippocampal circuitry and a…rescue of learning and memory deficits in an aged model of Alzheimer’s disease is very exciting.”

This study, which was supported in part by CIRM, points towards several possible therapeutic strategies that could one day help human brains ravaged by Alzheimer’s regrow the cells they’ve lost—and repair the damage to learning and memory that today remains irreparable. According to Huang:

“This study tells us that if there is any way we can enhance inhibitory neuron function in the hippocampus, like through the development of small molecule compounds, it may be beneficial for Alzheimer’s disease patients.”