Researchers from Tufts University and the University of Oxford have found that two common viruses —the varicella zoster and herpes simplex viruses— could trigger Alzheimer’s disease.
Varicella zoster (VZV) is an extremely common virus causes which causes chickenpox. Once cured of the first infection, the virus tends to linger in peripheral nerves where they remain dormant. When these dormant viruses are reactivated, they cause shingles.
HSV-1, the subtype of the herpes simplex virus, causes both oral and genital herpes. It is a very common infection, affecting nearly 4 million people worldwide under the age of 50 years. The American Sexual Health Organization estimates that around one in two adults has oral herpes in the United States.
Cytokines are produced in response to VZV. Cytokines are part of a healthy immune system. These small proteins help control the growth and activity of your blood cells and immune cells. Cytokines tell your immune system to do its job. But when too many cytokines are released, it can cause your immune system to go into overdrive, resulting in cytokine storm.
In their findings, published in the Journal of Alzheimer’s Disease, researchers found that when VZV infect neurons, they trigger an inflammatory response due to this overproduction of cytokines. This inflammatory response in turn awakens the herpes simplex viruses which typically lie dormant and harmless in the brain. With both viruses now active, inflammation throughout the brain is aggravated, potentially leading to the formation of plaque and the slow deterioration of neurons—both hallmarks of Alzheimer’s.
The study’s leading author, Dana Cairns, along with her team of collaborators gathered data by using lab grown cultures of brain nerve, or neural, stem cells. They found that infecting neurons with varicella zoster alone was not enough to trigger Alzheimer-like properties. However, when the herpes simplex was already lying-in wait, varicella zoster initiated a series of events that resulted in plaques, tangled fibers and brain damage.
“It’s a one-two punch of two viruses that are very common and usually harmless, but the lab studies suggest that if a new exposure to VZV wakes up dormant HSV-1, they could cause trouble,” explains Cairns. One of her collaborators, Oxford’s Ruth Itzhaki, was one of the first scientists to suggest a link between herpes infections and Alzheimer’s.
The California Institute for Regenerative Medicine (CIRM) has already invested almost $35 million in 21 different Alzheimer’s projects. In addition, we are committed to investing at least $1.5 billion in treatments that target conditions affecting the brain and central nervous system (CNS), including Alzheimer’s.
Thelma, participant in the CAMELLIA clinical trial
You have almost certainly never heard of Thelma, or met her, or know anything about her. She’s a lady living in England who, if it wasn’t for a CIRM-funded therapy, might not be living at all. She’s proof that what we do, is helping people.
Thelma is featured in a video about a treatment for acute myeloid leukemia, one of the most severe forms of blood cancer. Thelma took part in a clinical trial, called CAMELLIA, at Oxford Cancer Centre in Oxford, UK. The clinical trial uses a therapy that blocks a protein called CD47 that is found on the surface of cancer cells, including cancer stem cells which can evade traditional therapies. The video was shot to thank the charity Bloodwise for raising the funds to pay for the trial.
Prof. Paresh Vyas of Oxford University, who was part of the clinical trial team that treated Thelma, says patients with this condition face long odds.
“Patients with acute myeloid leukemia have the most aggressive blood cancer. We really haven’t had good treatments for this condition for the last 40 years.”
While this video was shot in England, featuring English nurses and doctors and patients, the therapy itself was developed here in California, first at Stanford University under the guidance of Irv Weissman and, more recently, at Forty Seven Inc. That company is now about to test their approach in a CIRM-funded clinical trial here in the US.
This is an example of how CIRM doesn’t just fund research, we invest in it. We help support it at every stage, from the earliest research through to clinical trials. Without our early support this work may not have made it this far.
The Forty Seven Inc. therapy uses the patient’s own immune system to help fight back against cancer stem cells. It’s looking very promising. But you don’t have to take our word for it. Take Thelma’s.
Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.
Two hearts beat as one, or not Sorry for the pre-Valentine’s Day buzzkill but stem cell research published this past week points to a very unromantic discovery: two hearts do not beat as one. The study, out of Rockefeller University, and published in the Journal of Cell Biology, sought to understand the limited success of clinical trials in which stem cell-derived heart muscle cells, or cardiomyocytes, are transplanted into the heart to help repair tissue scarred by disease or a heart attack.
If you’re a regular at The Stem Cellar, you’ll recall that just last Friday we summarized published experiments that suggest the cardiomyocytes used in successful trials do not grow new tissue themselves but instead heal the heart indirectly by releasing proteins that stimulate repair.
The research team behind this week’s study instead reasoned that the transplanted cardiomyocytes do indeed integrate into the heart tissue, but they fail to contract properly with the undamaged heart cells. So, the thinking goes, the transplanted cells do nothing to restore the heart’s ability to beat at full strength.
A two-cell “microtissue” contains a mouse embryonic stem cell-derived cardiomyocyte and a mouse neonatal cardiomyocyte. The lower panel shows the traction forces generated as the two cells contract; the stronger, neonatal cardiomyocyte produces more force than the weaker, stem cell-derived cardiomyocyte. Credit: Aratyn-Schause, Y. et al. J Cell Biol. 2016 Watch video here: http://medicalxpress.com/news/2016-02-muscles-on-a-chip-insight-cardiac-stem.html
To test this hypothesis, the researchers devised a two-cell micro-tissue made up of a single mouse cardiomyocyte and a single cardiomyocyte derived from either mouse embryonic stem cells or induced pluripotent stem cells (iPS). This “muscle-on-a-chip” showed that the two cells are able to physically connect up and even beat in sync with each other. But, the embryonic and iPS-derived cardiomyocytes beat less strongly than the native cell. Based on computer simulations, this imbalance made the micro-tissue beat less efficiently. A university press release picked up by Newswise includes a short yet fascinating video of the differing strengths of the beating heart cells (click on image above).
With this micro-tissue in hand, the team aims to find a way to fix this imbalance, which hopefully would make cell therapies for heart disease more potent.
Your Own Private Micro-liver Enough about micro-hearts, let’s talk micro-livers.
In a report published on Monday in PNAS, a multidisciplinary UCSD team of engineers and biomedical researchers described the creation of a bioprinted 3D liver model made from human iPS-derived liver cells, or hepatocytes. The hepatocytes are imprinted on a surface in hexagonal shapes, the kind seen in the complex microarchitecture of the human liver. These structures were also seeded with two other cell types: endothelial cells, which form blood vessels, and fat cells, which support the health of hepatocytes. Including these relevant cell types in the “micro-liver” design resulted in a 3D cell culture that not only mimics structures but also replicates functions found in a natural liver.
The 3-D-printed parts of the biomimetic liver tissue include: liver cells derived from human induced pluripotent stem cells (left), endothelial and mesenchymal supporing cells (center), and the resulting organized combination of multiple cell types (right). — Chen Laboratory, UC San Diego
This is a really exciting development for improving drug safety. A big concern of any new drug coming on the market is its potential liver toxicity, formally known as DILI (drug induced liver injury), the most common cause of liver failure in the U.S. Although animal studies and clinical trials carefully test for the potential of DILI, that doesn’t guarantee the drug will be safe in all individuals. And because this liver model was designed using human iPS cells – which can be derived from anyone with a simple skin biopsy – it has the potential to serve as a personalized drug screening device as well as a disease-in-a-dish model for studying inherited forms of liver disease.
As Bradley Fikes, San Diego Union Tribune’s biotechnology writer, mentions in an excellent summary of the publication, beyond drug screening and disease-in-dish modeling, this bioprinting process could also one day make it possible for researchers to reach the “holy grail” of tissue engineering: building an entire organ.
Finally! The Bloody Holy Grail While that holy grail remains on the horizon, Stanford researchers are nearly holding the goblet in their hands. Based on a Nature report published yesterday, a team led by CIRM grantee Irv Weissman have found a long sought after cellular tag that can fish out a very specific type of hematopoietic stem cell (HSC), or blood-forming stem cell, from bone marrow.
Almost thirty years ago, Weissman identified HSCs, which have the ability to form all the cell types of the blood. Since that time, scientists have struggled with fully understanding how HSCs are maintained in the body and, in turn, how to grow them in the laboratory.
The source of this problem is due to the fact that most HSCs are so-called short term HSCs because they eventually lose their “stemness”; that is, their ability to divide indefinitely. Only a small fraction of HSCs are of the long-term variety. To really understand how the body sustains a life-long supply of HSCs, it’s necessary to have a method to pick out just the long term HSCs.
So scientists in Weissman’s lab set out to do just that. Starting with a list of 100 genes that are known to be active in the bone marrow, they looked for genes that are turned on only in long term HSCs. After a painstaking, systematic method that took two years, the team narrowed down the list to just one gene that was unique to long term HSCs.
Co-lead author James Y. Chen, a MD/PHD candidate at Stanford, described the significance of this effort in a university press release:
James Y. Chen
“For nearly 30 years, people have been trying to grow HSCs outside the body and have not been able to do it — it’s arguably the ‘holy grail’ in this field. Now that we have an anchor, a way to look at long-term HSCs, we can look at the cells around them to understand and, ideally, recreate the niche.”
Older Dads and The Selfish Sperm
We wrap up the week with a PNAS publication that got a wide range of coverage by the likes of BBC News, Gizmodo and Cosmos in addition to the usual suspects like Health Canal. Not too surprising given the topic including selfish sperm and chopped up testicles.
Research over the past decade or so has made it increasingly clear that biological clocks not only tick for would-be moms but also dads. At first glance, it makes sense: older fathers have had more time to accumulate random DNA mutations in their spermatogonia, the stem cells that produce sperm. But studies of Apert syndrome, a rare disease causing defects in the skull, fingers and toes, has put this hypothesis in question.
Back in 2003, a research team at Oxford University found the mutation in spermatogonia that causes Apert syndrome occurs 100 to 1000 times more frequently than would be expected if it were merely due to a random mutation (the Apert syndrome is not inherited because males with the disease rarely go on to have children).
So what’s going on? To answer that question the Oxford scientists collaborated with a USC research team who (men: you may not want to read the rest of this sentence, this is your only warning) chopped up human testicles – ones that had been removed for unrelated medical reasons and donated – in order to reconstruct a three-dimensional map of where these Apert syndrome mutations were occurring. If the mutations were merely random, the affected spermatogonia would have been evenly distributed throughout the testicle. Instead, the team found clusters of cells carrying the mutation.
This results confirms a “selfish sperm” hypothesis in which the mutation provides a selective advantage to the affected sperm cells allowing them to out compete other nearby sperm cells, much like a cancer cell that multiples and gradually forms a tumor. The study serves as more sobering news to otherwise healthy older dads that they may have a higher risk of passing on harmful mutations to their offspring.
Like I said, sorry for the buzzkill. Happy Valentine’s Day weekend!
The backers of the cancer stem cell hypothesis just got a boost from scientists at the University of Oxford, UK, and the Karolinska Institute in Sweden, who last week used an advanced genetic tracking technique that identified, in patients, the presence of cancer stem cells—a small subset of cancer cells that many experts view as the underlying cause of cancer.
Scientists have long searched for a reliable way to measure and track cancer stem cells.
The concept of cancer stem cells has gained traction in recent years, but remains a controversial topic—in large part because it has proven difficult to definitively isolate them. Scientists have theorized that a small cadre of stem cells is responsible for propagating the growth of a patient’s cancer. So, even if the most advanced cancer treatments can destroy the tumor itself, there is always the risk of resurgence—unless the cancer stem cells are destroyed too.
As Dr. Peter Woll, the study’s first author, explained in last week’s news release:
“It’s like having dandelions in your yard. You can pull out as many as you want but if you don’t get the roots they’ll come back.”
As a result, considerable effort has been made worldwide to try track down these cells in their natural environment—because if they can be found, they could also be destroyed, thus destroying the cancer.
In this study, published last week in the journal Cancer Cell, the researchers studied patients who suffered from myelodysplastic syndrome (MDS), a blood condition that often progresses to acute myeloid leukemia. Using genetic tools, the researchers pinpointed specific cancer-driving mutations in the DNA of the tumor cells. Working backward, the team was then able to identify a small subset of cancer cells that had the hallmark properties of the elusive cancer stem cells. As explained in the news release:
“The MDS (cancer stem) cells were rare, sat at the top of the hierarchy of MDS cells, could sustain themselves, replenish the other MDS cells and were the origin of all stable DNA changes and mutations that drove the progression of the disease.”
Woll argues that these findings offer “conclusive evidence for the existence of cancer stem cells” in patients with MDS. The implications of this discovery, Dr. Woll argues, offer new insight into permanently eliminating a patient’s cancer:
“It is a vitally important step because it suggests that if you want to cure patients, you would need to target and remove these cells at the root of the cancer—but that would be sufficient, that would do it…. [These findings] give us a target for development of more efficient and cancer stem cell-specific therapies to eliminate the cancer.”