Millions of Americans use marijuana for medical reasons, such as reducing anxiety or helping ease the side effects of cancer therapy. Millions more turn to it for recreational reasons, saying it helps them relax. Now a new study says those who smoke marijuana regularly might be putting themselves at increased risk of heart disease and heart attack.
There has long been debate about the benefits versus the risks for using cannabis, with evidence on both sides to support each position. For example some studies have shown taking oral cannabinoids can help people cope with the nausea brought on by chemotherapy. Other studies have shown that regular use of marijuana can cause problems such as marijuana use disorder, a condition where the user is showing physical or psychological problems but has difficulty controlling or reducing their use of cannabis.
Now this latest study, from researchers at Stanford Medicine, shows that THC, the psychoactive part of the drug, can cause inflammation in endothelial cells. These are the cells that line the interior of blood vessels. When these cells become inflamed it can cause a constriction of the vessels and reduce blood flow. Over time this can create conditions that increase the risk of heart disease and heart attack.
The researchers, led by Dr. Joe Wu, began by analyzing data from the UK Biobank. This included information about some 35,000 people who reported smoking marijuana. Of these around 11,000 smoked more than once a month. The researchers found that regular marijuana smokers:
Were significantly more likely than others to have a heart attack.
Were also more likely to have their first heart attack before the age of 50, increasing their risk of subsequent attacks.
The team then used the iPSC method to create human endothelial cells and, in the lab, found that THC appeared to promote inflammation in the cells. They also found signs it created early indications of atherosclerosis, where there is a buildup of fat and plaque in the arteries.
They then tested mice which had been bred to have high levels of cholesterol and who were given a high fat diet. Some of the mice were then injected with THC, at a level comparable to smoking one marijuana cigarette a day. Those mice had far larger amounts of atherosclerosis plaque in their arteries compared to the mice who didn’t get the THC.
In a news release, Dr.Wu, the lead author of the study, said: “There’s a growing public perception that marijuana is harmless or even beneficial. Marijuana clearly has important medicinal uses, but recreational users should think carefully about excessive use.”
On the bright side, the team also reported that the damage caused by THC can be stopped by genistein, a naturally occurring compound found in soy and fava beans. The study, in the journal Cell, also found that genistein blocked the bad impact of THC without impeding the good impacts.
“As more states legalize the recreational use of marijuana, users need to be aware that it could have cardiovascular side effects,” said Dr. Wu. “But genistein works quite well to mitigate marijuana-induced damage of the endothelial vessels without blocking the effects marijuana has on the central nervous system, and it could be a way for medical marijuana users to protect themselves from a cardiovascular standpoint.”
Today the governing Board of the California Institute for Regenerative Medicine (CIRM) awarded $750,000 to Dr. Xiaokui Zhang at Celularity to conduct a clinical trial for the treatment of COVID-19. This brings the total number of CIRM clinical trials to 64, including three targeting the coronavirus.
This trial will use blood stem cells obtained from the placenta to generate natural killer (NK) cells, a type of white blood cell that is a vital part of the immune system, and administer them to patients with COVID-19. NK cells play an important role in defense against cancer and in fighting off viral infections. The goal is to administer these cells to locate the active sites of COVID-19 infection and destroy the virus-infected cells. These NK cells have been used in two other clinical trials for acute myeloid leukemia and multiple myeloma.
The Board also approved two additional awards for Discovery Stage Research (DISC2), which promote promising new technologies that could be translated to enable broad use and improve patient care.
One award for $100,000 was given to Dr. Albert Wong at Stanford. Dr. Wong has recently received an award from CIRM to develop a vaccine that produces a CD8+ T cell response to boost the body’s immune response to remove COVID-19 infected cells. The current award will enable him to expand on the initial approach to increase its potential to impact the Latinx and African American populations, two ethnicities that are disproportionately impacted by the virus in California.
The other award was for $249,996 and was given to Dr. Preet Chaudhary at the University of Southern California. Dr. Chaudary will use induced pluripotent stem cells (iPSCs) to generate natural killer cells (NK). These NK cells will express a chimeric antigen receptor (CAR), a synthetic receptor that will directly target the immune cells to kill cells infected with the virus. The ultimate goal is for these iPSC-NK-CAR cells to be used as a treatment for COVID-19.
“These programs address the role of the body’s immune T and NK cells in combatting viral infection and CIRM is fortunate enough to be able to assist these investigators in applying experience and knowledge gained elsewhere to find targeted treatments for COVID-19” says Dr. Maria T. Millan, the President & CEO of CIRM. “This type of critical thinking reflects the resourcefulness of researchers when evaluating their scientific tool kits. Projects like these align with CIRM’s track record of supporting research at different stages and for different diseases than the original target.”
The CIRM Board voted to endorse a new initiative to refund the agency and provide it with $5.5 billion to continue its work. The ‘California Stem Cell Research, Treatments and Cures Initiative of 2020 will appear on the November ballot.
The Board also approved a resolution honoring Ken Burtis, PhD., for his long service on the Board. Dr. Burtis was honored for his almost four decades of service at UC Davis as a student, professor and administrator and for his 11 years on the CIRM Board as both a member and alternate member. In the resolution marking his retirement the Board praised him, saying “his experience, commitment, knowledge, and leadership, contributed greatly to the momentum of discovery and the future therapies which will be the ultimate outcome of the dedicated work of the researchers receiving CIRM funding.”
Jonathan Thomas, the Chair of the Board, said “Ken has been invaluable and I’ve always found him to have tremendous insight. He has served as a great source of advice and inspiration to me and to the ICOC in dealing with all the topics we have had to face.”
Lauren Miller Rogen thanked Dr. Burtis, saying “I sat next to you at my first meeting and was feeling so extraordinarily overwhelmed and you went out of your way to explain all these big science words to me. You were always a source of help and support, and you explained things to me in a way that I always appreciated with my normal brain.”
Dr. Burtis said it has been a real honor and privilege to be on the Board. “I’ve been amazed and astounded at the passion and dedication that the Board and CIRM staff have brought to this work. Every meeting over the years there has been a moment of drama and then resolution and this Board always manages to reach agreement and serve the people of California.”
A few weeks ago we held a Facebook Live “Ask the Stem Cell Team About Parkinson’s Disease” event. As you can imagine we got lots of questions but, because of time constraints, only had time to answer a few. Thanks to my fabulous CIRM colleagues, Dr. Lila Collins and Dr. Kent Fitzgerald, for putting together answers to some of the other questions. Here they are.
Q:It seems like we have been hearing for years that stem cells can help people with Parkinson’s, why is it taking so long?
A: Early experiments in Sweden using fetal tissue did provide a proof of concept for the strategy of replacing dopamine producing cells damaged or lost in Parkinson’s disease (PD) . At first, this seemed like we were on the cusp of a cell therapy cure for PD, however, we soon learned based on some side effects seen with this approach (in particular dyskinesias or uncontrollable muscle movements) that the solution was not as simple as once thought.
While this didn’t produce the answer it did provide some valuable lessons.
The importance of dopaminergic (DA) producing cell type and the location in the brain of the transplant. Simply placing the replacement cells in the brain is not enough. It was initially thought that the best site to place these DA cells is a region in the brain called the SN, because this area helps to regulate movement. However, this area also plays a role in learning, emotion and the brains reward system. This is effectively a complex wiring system that exists in a balance, “rewiring” it wrong can have unintended and significant side effects.
Another factor impacting progress has been understanding the importance of disease stage. If the disease is too advanced when cells are given then the transplant may no longer be able to provide benefit. This is because DA transplants replace the lost neurons we use to control movement, but other connected brain systems have atrophied in response to losing input from the lost neurons. There is a massive amount of work (involving large groups and including foundations like the Michael J Fox Foundation) seeking to identify PD early in the disease course where therapies have the best chance of showing an effect. Clinical trials will ultimately help to determine the best timing for treatment intervention.
Ideally, in addition to the cell therapies that would replace lost or damaged cells we also want to find a therapy that slows or stops the underlying biology causing progression of the disease.
So, I think we’re going to see more gene therapy trials including those targeting the small minority of PD that is driven by known mutations. In fact, Prevail Therapeutics will soon start a trial in patients with GBA1 mutations. Hopefully, replacing the enzyme in this type of genetic PD will prevent degeneration.
And, we are also seeing gene therapy approaches to address forms of PD that we don’t know the cause, including a trial to rescue sick neurons with GDNF which is a neurotrophic factor (which helps support the growth and survival of these brain cells) led by Dr Bankiewicz and trials by Axovant and Voyager, partnered with Neurocrine aimed at restoring dopamine generation in the brain.
A small news report came out earlier this year about a recently completed clinical trial by Roche Pharma and Prothena. This addressed the build up in the brain of what are called lewy bodies, a problem common to many forms of PD. While the official trial results aren’t published yet, a recent press release suggests reason for optimism. Apparently, the treatment failed to statistically improve the main clinical measurement, but other measured endpoints saw improvement and it’s possible an updated form of this treatment will be tested again in the hopes of seeing an improved effect.
Finally, I’d like to call attention to the G force trials. Gforce is a global collaborative effort to drive the field forward combining lessons learned from previous studies with best practices for cell replacement in PD. These first-in-human safety trials to replace the dopaminergic neurons (DANs) damaged by PD have shared design features including identifying what the best goals are and how to measure those.
And the Summit PD trial, Dr Jeanne Loring of Aspen Neuroscience.
Taken together these should tell us quite a lot about the best way to replace these critical neurons in PD.
As with any completely novel approach in medicine, much validation and safety work must be completed before becoming available to patients
The current approach (for cell replacement) has evolved significantly from those early studies to use cells engineered in the lab to be much more specialized and representing the types believed to have the best therapeutic effects with low probability of the side effects (dyskinesias) seen in earlier trials.
If we don’t really know the cause of Parkinson’s disease, how can we cure it or develop treatments to slow it down?
PD can now be divided into major categories including 1. Sporadic, 2. Familial.
For the sporadic cases, there are some hallmarks in the biology of the neurons affected in the disease that are common among patients. These can be things like oxidative stress (which damages cells), or clumps of proteins (like a-synuclein) that serve to block normal cell function and become toxic, killing the DA neurons.
The second class of “familial” cases all share one or more genetic changes that are believed to cause the disease. Mutations in genes (like GBA, LRRK2, PRKN, SNCA) make up around fifteen percent of the population affected, but the similarity in these gene mutations make them attractive targets for drug development.
CIRM has funded projects to generate “disease in a dish” models using neurons made from adults with Parkinson’s disease. Stem cell-derived models like this have enabled not only a deep probing of the underlying biology in Parkinson’s, which has helped to identify new targets for investigation, but have also allowed for the testing of possible therapies in these cell-based systems.
iPSC-derived neurons are believed to be an excellent model for this type of work as they can possess known familial mutations but also show the rest of the patients genetic background which may also be a contributing factor to the development of PD. They therefore contain both known and unknown factors that can be tested for effective therapy development.
I have heard of scientists creating things called brain organoids, clumps of brain cells that can act a little bit like a brain. Can we use these to figure out what’s happening in the brain of people with Parkinson’s and to develop treatments?
There is considerable excitement about the use of brain organoids as a way of creating a model for the complex cell-to-cell interactions in the brain. Using these 3D organoid models may allow us to gain a better understanding of what happens inside the brain, and develop ways to treat issues like PD.
The organoids can contain multiple cell types including microglia which have been a hot topic of research in PD as they are responsible for cleaning up and maintaining the health of cells in the brain. CIRM has funded the Salk Institute’s Dr. Fred Gage’s to do work in this area.
If you go online you can find lots of stem cells clinics, all over the US, that claim they can use stem cells to help people with Parkinson’s. Should I go to them?
In a word, no! These clinics offer a wide variety of therapies using different kinds of cells or tissues (including the patient’s own blood or fat cells) but they have one thing in common; none of these therapies have been tested in a clinical trial to show they are even safe, let alone effective. These clinics also charge thousands, sometimes tens of thousands of dollars these therapies, and because it’s not covered by insurance this all comes out of the patient’s pocket.
These predatory clinics are peddling hope, but are unable to back it up with any proof it will work. They frequently have slick, well-designed websites, and “testimonials” from satisfied customers. But if they really had a treatment for Parkinson’s they wouldn’t be running clinics out of shopping malls they’d be operating huge medical centers because the worldwide need for an effective therapy is so great.
Here’s a link to the page on our website that can help you decide if a clinical trial or “therapy” is right for you.
Is it better to use your own cells turned into brain cells, or cells from a healthy donor?
This is the BIG question that nobody has evidence to provide an answer to. At least not yet.
Let’s start with the basics. Why would you want to use your own cells? The main answer is the immune system. Transplanted cells can really be viewed as similar to an organ (kidney, liver etc) transplant. As you likely know, when a patient receives an organ transplant the patient’s immune system will often recognize the tissue/organ as foreign and attack it. This can result in the body rejecting what is supposed to be a life-saving organ. This is why people receiving organ transplants are typically placed on immunosuppressive “anti-rejection “drugs to help stop this reaction.
In the case of transplanted dopamine producing neurons from a donor other than the patient, it’s likely that the immune system would eliminate these cells after a short while and this would stop any therapeutic benefit from the cells. A caveat to this is that the brain is a “somewhat” immune privileged organ which means that normal immune surveillance and rejection doesn’t always work the same way with the brain. In fact analysis of the brains collected from the first Swedish patients to receive fetal transplants showed (among other things) that several patients still had viable transplanted cells (persistence) in their brains.
Transplanting DA neurons made from the patient themselves (the iPSC method) would effectively remove this risk of the immune system attack as the cells would not be recognized as foreign.
CIRM previously funded a discovery project with Jeanne Loring from Scripps Research Institute that sought to generate DA neurons from Parkinson’s patients for use as a potential transplant therapy in these same patients. This project has since been taken on by a company formed, by Dr Loring, called Aspen Neuroscience. They hope to bring this potential therapy into clinical trials in the near future.
A commonly cited potential downside to this approach is that patients with genetic (familial) Parkinson’s would be receiving neurons generated with cells that may have the same mutations that caused the problem in the first place. However, as it can typically take decades to develop PD, these cells could likely function for a long time. and prove to be better than any current therapies.
Creating cells from each individual patient (called autologous) is likely to be very expensive and possibly even cost-prohibitive. That is why many researchers are working on developing an “off the shelf” therapy, one that uses cells from a donor (called allogeneic)would be available as and when it’s needed.
When the coronavirus happened, it seemed as if overnight the FDA was approving clinical trials for treatments for the virus. Why can’t it work that fast for Parkinson’s disease?
While we don’t know what will ultimately work for COVID-19, we know what the enemy looks like. We also have lots of experience treating viral infections and creating vaccines. The coronavirus has already been sequenced, so we are building upon our understanding of other viruses to select a course to interrupt it. In contrast, the field is still trying to understand the drivers of PD that would respond to therapeutic targeting and therefore, it’s not precisely clear how best to modify the course of neurodegenerative disease. So, in one sense, while it’s not as fast as we’d like it to be, the work on COVID-19 has a bit of a head start.
Much of the early work on COVID-19 therapies is also centered on re-purposing therapies that were previously in development. As a result, these potential treatments have a much easier time entering clinical trials as there is a lot known about them (such as how safe they are etc.). That said, there are many additional therapeutic strategies (some of which CIRM is funding) which are still far off from being tested in the clinic.
The concern of the Food and Drug Administration (FDA) is often centered on the safety of a proposed therapy. The less known, the more cautious they tend to be.
As you can imagine, transplanting cells into the brain of a PD patient creates a significant potential for problems and so the FDA needs to be cautious when approving clinical trials to ensure patient safety.
When I first saw the headline for this story I thought of the nursery rhyme about the three blind mice. Finally, they’ll be able to see the farmer’s wife coming at them with a carving knife. But the real-world implications are of this are actually pretty exciting.
Researchers at the National Institute of Health’s National Eye Institute took skin cells from mice and directly reprogrammed them into becoming light sensitizing cells in the eye, the kind that are often damaged and destroyed by diseases like macular degeneration or retinitis pigmentosa.
What’s particularly interesting about this is that it bypassed the induced pluripotent stem cell (iPSC) stage where researchers turn the skin cells into embryonic-like cells, then turn those into the cells found in the eye.
In a news release, Anand Swaroop of the NEI says this more direct approach has a number of advantages: “This is the first study to show that direct, chemical reprogramming can produce retinal-like cells, which gives us a new and faster strategy for developing therapies for age-related macular degeneration and other retinal disorders caused by the loss of photoreceptors.”
After converting the skin cells into cells called rod photoreceptors – the light sensing cells found in the back of the eye – the team transplanted them into blind mice. One month later they tested the mice to see if there had been any change in vision. There had; 43 percent of the mice reacted to light exposure, something they hadn’t done before.
Biraj Mahato, the study’s first author, said that three months later, the transplanted cells were still alive and functioning. “Even mice with severely advanced retinal degeneration, with little chance of having living photoreceptors remaining, responded to transplantation. Such findings suggest that the observed improvements were due to the lab-made photoreceptors rather than to an ancillary effect that supported the health of the host’s existing photoreceptors.”
Obviously there is a lot of work still to do before we can even begin to think about trying something like this in people. But this is certainly an encouraging start.
When someone thinks of machine learning, the first thing that comes to mind might be the technology used by Netflix or Hulu to suggest new shows based on their viewing history. But what if this technology could be applied towards advancing the field of regenerative medicine?
Thanks to a CIRM funded study, a team of scientists lead by Dr. Todd McDevitt at the Gladstone Institutes have found a way to to use machine learning to control the spacial organization of stem cells, a key process that plays a vital role in organ development. This new understanding of how stem cells organize themselves in 3D is an important step towards being able to create functional and/or personalized organs for research or organ transplants.
“We’ve shown how we can leverage the intrinsic ability of stem cells to organize,” said Dr. McDevitt in a news release from Gladstone Institutes. “This gives us a new way of engineering tissues, rather than a printing approach where you try to physically force cells into a specific configuration.”
In their normal environment, stem cells are able to form patterns as they mature and over time morph into the tissues seen in an adult organism. One type of stem cell, called an induced pluripotent stem cell (iPSC), can become nearly every cell type of the body. In fact, researchers have already found ways to direct iPSCs to become various cell types such as those in the heart or brain.
Unfortunately, attempting to replicate the pattern formation of stem cells as they mature has been challenging. Some have used 3D printing to lay out stem cells in a desired shape, but the cells often migrated away from their initial locations.
In the same news release mentioned above, Ashley Libby, a graduate student at Gladstone and co-first author of this study, said that,
“Despite the importance of organization for functioning tissues, we as scientists have had difficulty creating tissues in a dish with stem cells. Instead of an organized tissue, we often get a disorganized mix of different cell types.”
To solve this problem, the scientists used a computational model to learn how to influence stem cells into forming new arrangements, such as those that might be useful in generating personalized organs.
Previous studies conducted by Dr. McDevitt showed that blocking the expression of two genes, called ROCK1 and CDH1, affected the layout of iPS cells grown in a petri dish.
In this current study, the scientists used CRISPR/Cas9 gene editing (you can read about this technology in more detail here) to block expression of ROCK1 and CDH1 at any time by adding a drug to the iPSCs. This was done to see if they could predict stem cell arrangement based on the alterations made to ROCK1 and CDH1 at different drug doses and time periods.
The team carried out various experiments with different doses and timing. Then, the data was input into a machine-learning program designed to identify patterns, something that could take a human months to identify.
The machine-learning program used the data to predict ways that ROCK1 and CDH1 affect iPSC organization. The scientists then began to see whether the program could compute how to make entirely new patterns, like a bull’s-eye or an island of cells. The team says the results were little short of astounding. Machine learning was able to accurately predict conditions that will cause stem cell colonies to form desired patterns.
The full study was published in the journal Cell Systems.
Clive Svendsen, PhD, left, director of the Cedars-Sinai Board of Governors Regenerative Medicine Institute, and Samuel Sances, PhD, a postdoctoral fellow at the institute, with the January 2019 special edition of National Geographic. The magazine cover features a striking image of spinal cord tissue that was shot by Sances in his lab. Photo by Cedars-Sinai.
National Geographic is one of those iconic magazines that everyone knows about but few people read. Which is a shame, because it’s been around since 1888 and has helped make generations of readers aware about the world around them. And now, it’s shifting gears and helping people know more about the world inside them. That’s because a special January edition of National Geographic highlights stem cells.
The issue, called ‘The Future of Medicine’, covers a wide range of issues including stem cell research being done at Cedars-Sinai by Clive Svendsen and his team (CIRM is funding Dr. Svendsen’s work in a clinical trial targeting ALS, you can read about that here). The team is using stem cells and so-called Organ-Chips to develop personalized treatments for individual patients.
Here’s how it works. Scientists take blood or skin cells from individual patients, then using the iPSC method, turn those into the kind of cell in the body that is diseased or damaged. Those cells are then placed inside a device the size of an AA battery where they can be tested against lots of different drugs or compounds to see which ones might help treat that particular problem.
This approach is still in the development phase but if it works it would enable doctors to tailor a treatment to a patient’s specific DNA profile, reducing the risk of complications and, hopefully, increasing the risk it will be successful. Dr. Svendsen says it may sound like science fiction, but this is not far away from being science fact.
“I think we’re entering a new era of medicine—precision medicine. In the future, you’ll have your iPSC line made, generate the cell type in your body that is sick and put it on a chip to understand more about how to treat your disease.”
Dr. Svendsen isn’t the only connection CIRM has to the article. The cover photo for the issue was taken by Sam Sances, PhD, who received a CIRM stem cell research scholarship in 2010-2011. Sam says he’s grateful to CIRM for being a longtime supporter of his work. But then why wouldn’t we be. Sam – who is still just 31 years old – is clearly someone to watch. He got his first research job, as an experimental coordinator, with Pacific Ag Research in San Luis Obispo when he was still in high school.
Neurons derived from stem cells.Credit: Silvia Riccardi/SPL
Currently, more than 10 million people worldwide live with Parkinson’s disease (PD). By 2020, in the US alone, people living with Parkinson’s are expected to outnumber the cases of multiple sclerosis, muscular dystrophy and Lou Gehrig’s disease combined.
There is no cure for Parkinson’s and treatment options consist of medications that patients ultimately develop tolerance to, or surgical therapies that are expensive. Therefore, therapeutic options that offer long-lasting treatment, or even a cure, are essential for treating PD.
To understand their treatment strategy, however, we first have to understand what causes this disease. Parkinson’s results from decreased numbers of neurons that produce dopamine, a molecule that helps control muscle movements. Without proper dopamine production, patients experience a wide range of movement abnormalities, including the classic tremors that are associated with PD.
The current treatment options only target the symptoms, as opposed to the root cause of the disease. Takashi’s group decided to go directly to the source and improve dopamine production in these patients by correcting the dopaminergic neuron shortage.
The scientists harvested skin cells from a healthy donor and reprogrammed them to become induced pluripotent stem cells (iPSCs), or stem cells that become any type of cell. These iPSCs were then turned into the precursors of dopamine-producing neurons and implanted into 12 brain regions known to be hotspots for dopamine production.
The procedure was carried out in October and the patient, a male in his 50s, is still healthy. If his symptoms continue to improve and he doesn’t experience any bad side effects, he will receive a second dose of dopamine-producing stem cells. Six other patients are scheduled to receive this same treatment and Takashi hopes that, if all goes well, this type of treatment can be ready for the general public by 2023.
This treatment was first tested in monkeys, where the researchers saw that not only did the implanted stem cells improve Parkinson’s symptoms and survive in the brain for at least two years, but they also did not cause any negative side effects.
CRISPR iPSC colony of human skin cells showing expression of SOX2 and TRA-1-60, markers of human embryonic pluripotent stem cells
Back in 2012, Shinya Yamanaka was awarded the Nobel Prize in Physiology or Medicine for his group’s identification of “Yamanaka Factors,” a group of genes that are capable of turning ordinary skin cells into induced pluripotentent stem cells (iPSCs) which have the ability to become any type of cell within the body. Discovery of iPSCs was, and has been, groundbreaking because it not only allows for unprecedented avenues to study human disease, but also has implications for using a patient’s own cells to treat a wide variety of diseases.
Recently, Timo Otonkoski’s group at the University of Helsinki along with Juha Kere’s group at the Karolinska Institutet and King’s College, London have found a way to program iPSCs from skin cells using CRISPR, a gene editing technology. Their approach allows for the induction, or turning on of iPSCs using the cells own DNA, instead of introducing the previously identified Yamanka Factors into cells of interest.
As detailed in their study, published in the journal Nature Communications, this is the first instance of mature human cells being completely reprogrammed into pluripotent cells using only CRISPR. Instead of using the canonical CRISPR system that allows the CAS9 protein (an enzyme that is able to cut DNA, thus rendering a gene of interest dysfunctional) to mutate any gene of interest, this group used a modified version of the CAS9 protein, which allows them to turn on or off the gene that CAS9 is targeted to.
The robustness of their approach lies in the researcher’s identification of a DNA sequence that is commonly found near genes involved in embryonic development. As CAS9 needs to be guided to genes of interest to do its job, identification of this common motif allows multiple genes associated with pluripotency to be activated in mature human skin cells, and greatly increased the efficiency and effectiveness of this approach.
In a press release, Dr. Otonkoski further highlights the novelty and viability of this approach:
“…Reprogramming based on activation of endogenous genes rather than overexpression of transgenes is…theoretically a more physiological way of controlling cell fate and may result in more normal cells…”
It’s common knowledge that your liver is a champion when it comes to regeneration. It’s actually one of the few internal organs in the human body that can robustly regenerate itself after injury. Other organs such as the heart and lungs do not have the same regenerative response and instead generate scar tissue to protect the injured area. Liver regeneration is very important to human health as the liver conducts many fundamental processes such as making proteins, breaking down toxic substances, and making new chemicals required to digest your food.
The human liver
Over the years, scientists have suggested multiple theories for why the liver has this amazing regenerative capacity. What’s known for sure is that mature hepatocytes (the main cell type in the liver) will respond to injury by dividing and proliferating to make more hepatocytes. In this way, the liver can regrow up to 70% of itself within a matter of a few weeks. Pretty amazing right?
So what is the source of these regenerative hepatocytes? It was originally thought that adult liver stem cells (called oval cells) were the source, but this theory has been disproved in the past few years. The answer to this million-dollar question, however, likely comes from a study published last week in the journal Cell.
A group at UCSD led by Dr. Michael Karin reported a new population of liver cells called “hybrid hepatocytes”. These cells were discovered in an area of the healthy liver called the portal triad. Using mouse models, the CIRM-funded group found that hybrid hepatocytes respond to chemical-induced injury by massively dividing to replace damaged or lost liver tissue. When they took a closer look at these newly-identified cells, they found that hybrid hepatocytes were very similar to normal hepatocytes but differed slightly with respect to the types of liver genes that they expressed.
A common concern associated with regenerative tissue and cells is the development of cancer. Actively dividing cells in the liver can acquire genetic mutations that can cause hepatocellular carcinoma, a common form of liver cancer.
What makes this group’s discovery so exciting is that they found evidence that hybrid hepatocytes do not cause cancer in mice. They showed this by transplanting a population of hybrid hepatocytes into multiple mouse models of liver cancer. When they dissected the liver tumors from these mice, none of the transplanted hybrid cells were present. They concluded that hybrid hepatocytes are robust and efficient at regenerating the liver in response to injury, and that they are a safe and non-cancer causing source of regenerating liver cells.
Currently, liver transplantation is the only therapy for end-stage liver diseases (often caused by cirrhosis or hepatitis) and aggressive forms of liver cancer. Patients receiving liver transplants from donors have a good chance of survival, however donated livers are in short supply, and patients who actually get liver transplants have to take immunosuppressant drugs for the rest of their lives. Stem cell-derived liver tissue, either from embryonic or induced pluripotent stem cells (iPSC), has been proposed as an alternative source of transplantable liver tissue. However, safety of iPSC-derived tissue for clinical applications is still being addressed due to the potential risk of tumor formation caused by iPSCs that haven’t fully matured.
This study gives hope to the future of cell-based therapies for liver disease and avoids the current hurdles associated with iPSC-based therapy. In a press release from UCSD, Dr. Karin succinctly summarized the implications of their findings.
“Hybrid hepatocytes represent not only the most effective way to repair a diseased liver, but also the safest way to prevent fatal liver failure by cell transplantation.”
This exciting and potentially game-changing research was supported by CIRM funding. The first author, Dr. Joan Font-Burgada, was a CIRM postdoctoral scholar from 2012-2014. He reached out to CIRM regarding his publication and provided the following feedback:
CIRM postdoctoral scholar Joan Font-Burgada
“I’m excited to let you know that work CIRM funded through the training program will be published in Cell. I would like to express my most sincere gratitude for the opportunity I was given. I am convinced that without CIRM support, I could not have finished my project. Not only the training was excellent but the resources I was offered allowed me to work with enough independence to explore new avenues in my project that finally ended up in this publication.”
We at CIRM are always thrilled and proud to hear about these success stories. More importantly, we value feedback from our grantees on how our funding and training has supported their science and helped them achieve their goals. Our mission is to develop stem cell therapies for patients with unmet medical needs, and studies such as this one are an encouraging sign that we are making progress towards to achieving this goal.
There is no singular cause of Parkinson’s disease, but many—making this disease so difficult to understand and, as a result, treat. But now, researchers at the Buck Institute for Research on Aging have tracked down precisely how a genetic change, or mutation, can lead to a common form of the disease. The results, published last week in the journal Stem Cell Reports, point to new and improved strategies at tackling the underlying processes that lead to Parkinson’s.
Mitochondria from iPSC-derived neurons. On the left is a neuron derived from a healthy individual, while the image on the right shows a neuron derived from someone with the Park2 mutation, the most common mutation in Parkinson’s disease (Credit: Akos Gerencser)
The debilitating symptoms of Parkinson’s—most notably stiffness and tremors that progress over time, making it difficult for patients to walk, write or perform other simple tasks—can in large part be linked to the death of neurons that secrete the hormone dopamine. Studies involving fruit flies in the lab had identified mitochondria, cellular ‘workhorses’ that churn out energy, as a key factor in neuronal death. But this hypothesis had not been tested using human cells.
Now, scientists at the Buck Institute have replicated the process in human cells, with the help of stem cells derived from patients suffering from Parkinson’s, a technique called induced pluripotent stem cell technology, or iPSC technology. These newly developed neurons exactly mimic the disease at the cellular level. This so-called ‘disease in a dish’ is one of the most promising applications of stem cell technology.
“If we can find existing drugs or develop new ones that prevent damage to the mitochondria we would have a potential treatment for PD,” said Dr. Xianmin Zeng, the study’s senior author, in a press release.
And by using this technology, the Buck Institute team confirmed that the same process that occurred in fruit fly cells also occurred in human cells. Specifically, the team found that a particular mutation in these cells, called Park2, altered both the structure and function of mitochondria inside each cell, setting off a chain reaction that leads to the neurons’ inability to produce dopamine and, ultimately, the death of the neuron itself.
This study, which was funded in part by a grant from CIRM, could be critical in the search for a cure for a disease that, as of yet, has none. Current treatment regimens aimed at slowing or reducing symptoms have had some success, but most begin to fail overtime—or come with significant negative side effects. The hope, says Zeng, is that iPSC technology can be the key to fast-tracking promising drugs that can actually target the disease’s underlying causes, and not just their overt symptoms. Hear more from Dr. Xianmin Zeng as she answers your questions about Parkinson’s disease and stem cell research: