The Bee Gees, pioneers in trying to find ways to mend a broken heart. Photograph: Michael Ochs Archives
This may be the first time that the Australian pop group the Bee Gees have ever been featured in a blog about stem cell research, but in this case I think it’s appropriate. One of the Bee Gees biggest hits was “How can you mend a broken heart” and while it was a fine song, Barry and Robin Gibb (who wrote the song) never really came up with a viable answer.
Happily some researchers at the University of Southern California may succeed where Barry and Robin failed. In a study, published in the journal Nature Genetics, the USC team identify a gene that may help regenerate damaged heart tissue after a heart attack.
When babies are born they have a lot of a heart muscle cell called a mononuclear diploid cardiomyocyte or MNDCM for short. This cell type has powerful regenerative properties and so is able to rebuild heart muscle. However, as we get older we have less and less MNDCMs. By the time most of us are at an age where we are most likely to have a heart attack we are also most likely to have very few of these cells, and so have a limited ability to repair the damage.
Michaela Patterson, and her colleagues at USC, set out to find ways to change that. They found that in some adult mice less than 2 percent of their heart cells were MNDCMs, while other mice had a much higher percentage, around 10 percent. Not surprisingly the mice with the higher percentage of MNDCMs were better able to regenerate heart muscle after a heart attack or other injury.
So the USC team – with a little help from CIRM funding – dug a little deeper and did a genome-wide association study of these mice, that’s where they look at all the genetic variants in different individuals to see if they can spot common traits. They found one gene, Tnni3k, that seems to play a key role in generating MNDCMs.
Turning Tnni3K off in mice resulted in higher numbers of MNDCMs, increasing their ability to regenerate heart muscle. But when they activated Tnni3k in zebrafish it reduced the number of MNDCMs and impaired the fish’s ability to repair heart damage.
While it’s a long way from identifying something interesting in mice and zebrafish to seeing if it can be used to help people, Henry Sucov, the senior author on the study, says these findings represent an important first step in that direction:
“The activity of this gene, Tnni3k, can be modulated by small molecules, which could be developed into prescription drugs in the future. These small molecules could change the composition of the heart over time to contain more of these regenerative cells. This could improve the potential for regeneration in adult hearts, as a preventative strategy for those who may be at risk for heart failure.”
Caleb Sizemore speaks to the CIRM Board at the June 2017 ICOC meeting.
Having been to many conferences and meetings over the years I have found there is a really simple way to gauge if someone is a good speaker, if they have the attention of people in the room. You just look around and see how many people are on their phones or laptops, checking their email or the latest sports scores.
By that standard Caleb Sizemore is a spellbinding speaker.
To say his talk was both deeply moving and inspiring is an understatement. I could go into more detail but it’s so much more powerful to hear it from Caleb himself. His words are a reminder to everyone at CIRM why we do this work, and why we have to continue to do all that we can to live up to our mission statement and accelerate stem cell treatments to patients with unmet medical needs.
The human cardiovascular system is an intricate, complex network of blood vessels that include arteries, capillaries and veins. These structures distribute blood from the heart to all parts of the body, from our head to our toes, and back again.
This week, two groups of scientists published studies showing that they can create key components of the human cardiovascular system from human pluripotent stem cells. These technologies will not only be valuable for modeling the cardiovascular system, but also for developing transplantable tissues to treat patients with cardiovascular or vascular diseases.
Growing capillaries using 3D printers
Scientists from Rice University and the Baylor College of Medicine are using 3D printers to make functioning capillaries. These are tiny, thin vessels that transport blood from the arteries to the veins and facilitate the exchange of oxygen, nutrients and waste products between the blood and tissues. Capillaries are made of a single layer of endothelial cells stitched together by cell structures called tight junctions, which create an impenetrable barrier between the blood and the body.
In work published in the journal Biomaterials Science, the scientists discovered two materials that coax human stem cell-derived endothelial cells to develop into capillary-like structures. They found that adding mesenchymal stem cells to the process, improved the ability of the endothelial cells to form into the tube-like structures resembling capillaries. Lead author on the study, Gisele Calderon, explained their initial findings in an interview with Phys.org,
“We’ve confirmed that these cells have the capacity to form capillary-like structures, both in a natural material called fibrin and in a semisynthetic material called gelatin methacrylate, or GelMA. The GelMA finding is particularly interesting because it is something we can readily 3-D print for future tissue-engineering applications.”
Scientists grow capillaries from stem cells using 3D gels. (Image Credit: Jeff Fitlow/Rice University)
The team will use their 3D printing technology to develop more accurate models of human tissues and their vast network of capillaries. Their hope is that these 3D printed tissues could be used for more accurate drug testing and eventually as implantable tissues in the clinic. Co-senior author on the study, Jordan Miller, summarized potential future applications nicely.
“Ultimately, we’d like to 3D print with living cells … to create fully vascularized tissues for therapeutic applications. You could foresee using these 3D printed tissues to provide a more accurate representation of how our bodies will respond to a drug. The potential to build tissue constructs made from a particular patient represents the ultimate test bed for personalized medicine. We could screen dozens of potential drug cocktails on this type of generated tissue sample to identify candidates that will work best for that patient.”
Growing functioning arteries
In a separate study published in the journal PNAS, scientists from the University of Wisconsin-Madison and the Morgridge Institute reported that they can generate functional arterial endothelial cells, which are cells that line the insides of human arteries.
The team used a lab technique called single-cell RNA sequencing to identify important signaling factors that coax human pluripotent stem cells to develop into arterial endothelial cells. The scientists then used the CRISPR/Cas9 gene editing technology to develop arterial “reporter cell lines”, which light up like Christmas trees when candidate factors are successful at coaxing stem cells to develop into arterial endothelial cells.
Arterial endothelial cells derived from human pluripotent stem cells. (The Morgridge Institute for Research)
Using this two-pronged strategy, they generated cells that displayed many of the characteristic functions of arterial endothelial cells found in the body. Furthermore, when they transplanted these cells into mice that suffered a heart attack, the cells helped form new arteries and improved the survival rate of these mice significantly. Mice who received the transplanted cells had an 83% survival rate compared to untreated mice who only had a 33% survival rate.
“Our ultimate goal is to apply this improved cell derivation process to the formation of functional arteries that can be used in cardiovascular surgery. This work provides valuable proof that we can eventually get a reliable source for functional arterial endothelial cells and make arteries that perform and behave like the real thing.”
In the future, the scientists have set their sights on developing a universal donor cell line that can treat large populations of patients without fear of immune rejection. With cardiovascular disease being the leading cause of death around the world, the demand for such a stem cell-based therapy is urgent.
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.
Image from Scope Blog.
Understanding Heart Defects. Healthy heart tissue is made up of smooth, solid muscle, which is essential for normal heart function. Patients with a heart defect called left ventricular non-compaction (LVNC), lack normal heart tissue in their left ventricle – the largest, strongest blood-pumping chamber – and instead have spongy-looking tissue.
LVNC occurs during early heart development where pieces of heart muscle fail to condense (compact) and instead form an airy, sponge-like network that can leave patients at risk for heart failure and other complications.
A team at Stanford is interested in learning how LVNC occurs in humans, and they’re using human stem cells for the answer. Led by CIRM grantee Joe Wu, the scientists generated induced pluripotent stem cells (iPSCs) from four patients with LVNC. iPSCs are cells that can be turned into any other cell in the body, so Wu turned these cells into iPSC-derived heart muscle in a dish.
Wu’s team was particularly interested in determining why some LVNC patients have symptoms of disease while others seem perfectly normal. After studying the heart muscle cells derived from the four LVNC patients, they identified a genetic mutation in a gene called TBX20. This gene produces a type of protein called a cardiac transcription factor, which controls the expression of other heart related genes.
Upon further exploration, the scientists found that the genetic mutation in TBX20 prevented LVNC heart muscle cells from dividing at their normal rate. If they blocked the signal of mutant TBX20, the heart cells went back to their normal activity and created healthy looking heart tissue.
This study was published in Nature Cell Biology and covered by the Stanford Medicine Scope blog. In an interview with Scope, Joe Wu highlighted the big picture of their work:
Joseph Wu Stanford
“This study shows the feasibility of modeling such developmental defects using human tissue-specific cells, rather than relying on animal cells or animal models. It opens up an exciting new avenue for research into congenital heart disease that could help literally the youngest — in utero — patients.”
Stem Cell Heart Patch. Scientists from the University of Wisconsin, Madison are creating stem cell-based heart patches that they hope one day could be used to treat heart disease.
In a collaboration with Duke and the University of Alabama at Birmingham, they’re developing 3D stem cell-derived patches that contain the three main cell types found in the heart: cardiomyocytes (heart muscle cells), fibroblasts (support cells), and endothelial cells (cells that line the insides of blood vessels). These patches would be transplanted into heart disease patients to replace damaged heart tissue and improve heart function.
As with all research that has the potential for reaching human patients, the scientists must first determine whether the heart patches are safe in animal models. They plan to transplant the heart patches into a pig model – chosen because pigs have similar sized hearts compared to humans.
In a UW-Madison News release, the director of the UW-Madison Stem Cell and Regenerative Medicine Center Timothy Kamp, hinted at the potential for this technology to reach the clinic.
“The excitement here is we’re moving closer to patient applications. We’re at a stage when we need to see how these cells do in a large animal heart attack model. We’ll be making patches of heart muscle that can be applied to these injured areas.”
Kamp and his team still have a lot of work to do to perfect their heart patch technology, but they are thinking ahead. Two issues that they are trying to address are how to prevent a patient’s immune system from rejecting the heart patch transplant, and how to make sure the heart patches beat in sync with the heart they are transplanted into.
Check out the heart patches in action in this video:
(Video courtesy of Xiaojun Lian)
Cool Stem Cell Art! When I was a scientist, I worked with stem cells all the time. I grew them in cell culture dishes, coaxed them to differentiate into brain cells, and used a technique called immunostaining to take really beautiful, colorful pictures of my final cell products. I took probably thousands of pictures over my PhD and postdoc, but sadly, only a handful of these photos ever made it into journal publications. The rest collected dust either on my hard drive or in my lab notebook.
It’s really too bad that at the time I didn’t know about this awesome stem cell art contest called Cells I See run by the Centre for Commercialization of Regenerative Medicine (CCRM) in Ontario Canada and sponsored by the Stem Cell Network.
The contest “is about the beauty of stem cells and biomaterials, seen directly through the microscope or through the interpretive lens of the artist.” Scientists can submit their most prized stem cell images or art, and the winner receives a cash prize and major science-art street cred.
The submission deadline for this year’s contest was earlier this month, and you can check out the contenders on CCRM’s Facebook page. Even better, you can vote for your favorite image or art by liking the photo. The last date to vote is October 15th and the scientist whose image has the most likes will be the People’s Choice winner. CCRM will also crown a Grand Prize winner at the Till & McCulloch Stem Cell Meeting in October.
I’ll leave you with a few of my favorite photos, but please don’t let this bias your vote =)!
Lessons learned from babies with heart failure could now help adults
Inspiration can sometimes come from the most unexpected of places. For English researcher Stephen Westaby it came from seeing babies who had heart attacks bounce back and recover. It led Westaby to a new line of research that could offer hope to people who have had a heart attack.
Westaby, a researcher at the John Radcliffe hospital in Oxford, England, found that implanting a novel kind of stem cell in the hearts of people undergoing surgery following a heart attack had a surprisingly significant impact on their recovery.
Westaby got his inspiration from studies showing babies who had a heart attack and experienced scarring on their heart, were able to bounce back and, by the time they reached adolescence, had no scarring. He wondered if it was because the babies’ own heart stem cells were able to repair the damage.
Scarring is a common side effect of a heart attack and affects the ability of the heart to be able to pump blood efficiently around the body. As a result of that diminished pumping ability people have less energy, and are at increased risk of further heart problems. For years it was believed this scarring was irreversible. This study, published in the Journal of Cardiovascular Translational Research, suggests it may not be.
Westaby and his team implanted what they describe as a “novel mesenchymal precursor (iMP)” type of stem cell in the hearts of patients who were undergoing heart bypass surgery following a heart attack. The cells were placed in parts of the heart that showed sizeable scarring and poor blood flow.
Two years later the patients showed a 30 percent improvement in heart function, a 40 percent reduction in scar size, and a 70 percent improvement in quality of life.
In an interview with the UK Guardian newspaper, Westaby admitted he was not expecting such a clear cut benefit:
“Quite frankly it was a big surprise to find the area of scar in the damaged heart got smaller,”
Of course it has to be noted that the trial was small, only involving 11 patients. Nonetheless the findings are important and impressive. Westaby and his team now hope to do a much larger study.
CIRM is funding a clinical trial with Capricor that is taking a similar approach, using stem cells to rejuvenate the hearts of patients who have had heart attacks.
Fred Lesikar, one of the patient’s in the first phase of that trial, experienced a similar benefit to those in the English trial and told us about it in our Stories of Hope.
It’s always exciting to read a science article featuring a talented scientist who is breaking boundaries in the field of regenerative medicine. It’s especially exciting to us at CIRM when the scientist is a CIRM grantee.
Last week, OZY published a fun and inspiring piece on Stanford scientist Joe Wu. Dr. Wu is the Director of the Stanford Cardiovascular Institute and his lab studies how stem cells (both adult and pluripotent) function and how they can be used to model heart diseases and screen for new drug therapies. He also is a CIRM grantee and has a Disease Team Therapy Development grant that aims to clinically test human embryonic stem cell-derived cardiomyocytes (heart cells) in end stage heart failure patients.
Dr. Joe Wu. (Image Source: Sean Culligan/OZY)
The OZY piece does a great job of highlighting Dr. Wu’s recent efforts to use human induced pluripotent stem cells (iPS cells) to make heart tissue in a dish and model cardiovascular disease. And without getting too technical, the article explains Dr. Wu’s larger mission to combine precision medicine and stem cell research to identify drugs that would be best suited for specific patient populations.
The article commented,
“He envisions treatments based on an individual’s own iPS cells. For example, a popular breast cancer drug has an 8 percent chance of giving patients heart failure. In Wu’s world, we’d test the drug on stem cells first, and if a patient lands in that 8 percent, begin treatment for the side effects preemptively or avoiding the drug totally and avoiding heart failure, too.”
Basically, Dr. Wu sees the future of clinical trials in a dish using human stem cells. “His goal is to take these stem cells from thousands of patients to create a genetically diverse enough bank that will allow for “clinical trials in a dish” — Wu’s go-to phrase.”
Instead of following the traditional drug development paradigm that takes more than 10 years, billions of dollars, and unfortunately usually ends in failure, Dr. Wu wants to follow an accelerated path where stem cells are used for drug toxicity and efficacy testing.
This alternative path could improve overall drug development and approval by the FDA. The article explained,
“Testing drugs on stem cells will give big pharma and the FDA vastly improved heads up for toxic complications. Stem cells are “absolutely” the best avenue going forward, says Norman Stockbridge, director of the division of cardiovascular and renal products at the FDA’s Center for Drug Evaluation and Research.”
Not everyone is on the same page with Dr. Wu’s bold vision of the future of precision medicine, stem cells, and treatments for heart disease. Some believe he is overly ambitious, however top scientists in the stem cell field have praised Dr. Wu’s “systematic approach” to research and how he doesn’t stop at data discovery, he focuses on the big picture and how his work can ultimately help patients.
You can read more about Dr. Wu’s research on his lab website and I highly encourage you to check out the OZY article which is a great example of science communication for the general public.
It seems like an oxymoron but one in ten Americans has a rare disease. With more than 7,000 known rare diseases it’s easy to see how each one could affect thousands of individuals and still be considered a rare or orphan condition.
Only 5% of rare diseases have FDA approved therapies
People with rare diseases, and their families, consider themselves the underdogs of the medical world because they often have difficulty getting a proper diagnosis (most physicians have never come across many of these diseases and so don’t know how to identify them), and even when they do get a diagnosis they have limited treatment options, and those options they do have are often very expensive. It’s no wonder these patients and their families feel isolated and alone.
Rare diseases affect more people than HIV and Cancer combined
Hopefully some will feel less isolated after yesterday’s CIRM Board meeting when several rare diseases were among the big winners, getting funding to tackle conditions such as ALS or Lou Gehrig’s disease, Severe Combined Immunodeficiency or SCID, Canavan disease, Tay-Sachs and Sandhoff disease. These all won awards under our Translation Research Program except for the SCID program which is a pre-clinical stage project.
As CIRM Board Chair Jonathan Thomas said in our news release, these awards have one purpose:
“The goal of our Translation program is to support the most promising stem cell-based projects and to help them accelerate that research out of the lab and into the real world, such as a clinical trial where they can be tested in people. The projects that our Board approved today are a great example of work that takes innovative approaches to developing new therapies for a wide variety of diseases.”
These awards are all for early-stage research projects, ones we hope will be successful and eventually move into clinical trials. One project approved yesterday is already in a clinical trial. Capricor Therapeutics was awarded $3.4 million to complete a combined Phase 1/2 clinical trial treating heart failure associated with Duchenne muscular dystrophy with its cardiosphere stem cell technology. This same Capricor technology is being used in an ongoing CIRM-funded trial which aims to heal the scarring that occurs after a heart attack.
Duchenne muscular dystrophy (DMD) is a genetic disorder that is marked by progressive muscle degeneration and weakness. The symptoms usually start in early childhood, between ages 3 and 5, and the vast majority of cases are in boys. As the disease progresses it leads to heart failure, which typically leads to death before age 40.
The Capricor clinical trial hopes to treat that aspect of DMD, one that currently has no effective treatment.
As our President and CEO Randy Mills said in our news release:
Randy Mills, Stem Cell Agency President & CEO
“There can be nothing worse than for a parent to watch their child slowly lose a fight against a deadly disease. Many of the programs we are funding today are focused on helping find treatments for diseases that affect children, often in infancy. Because many of these diseases are rare there are limited treatment options for them, which makes it all the more important for CIRM to focus on targeting these unmet medical needs.”
Speaking on Rare Disease Day (you can read our blog about that here) Massachusetts Senator Karen Spilka said that “Rare diseases impact over 30 Million patients and caregivers in the United States alone.”
Hopefully the steps that the CIRM Board took yesterday will ultimately help ease the struggles of some of those families.
Here’s a heartfelt science story for all those Valentine’s day fans out there. Scientists from the Gladstone Institutes have identified how a group of transcription factors interact during embryonic development to make a healthy heart. Their work will increase our biological understanding of how the heart is formed and could produce new methods for treating cardiovascular disease.
The study, published today in the journal Cell, describes a tumultuous love story between cardiac transcription factors. Transcription factors are proteins that orchestrate gene expression. They have the power to turn genes on or off by binding to specific DNA sequences and recruiting other proteins that will eventually turn the information encoded in that gene into a functional protein.
Every organ has its own special group of transcription factors that coordinate the gene expression required for that organ’s development. Often times, transcription factors within a group directly interact with each other and work together to conduct a specific sequence of events. These interactions are essential for making healthy tissues and organs, but scientists don’t always understand how these interactions work.
For the heart, scientists have already identified a group of transcription factors essential for cardiac development, and genetic mutations in any of these factors can impair heart formation and cause heart defects in newborns. What’s not known, however, are the details on how some of these cardiac transcription factors interact to get their job done.
A cardiac love triangle
In the Gladstone study, the scientists focused on how three key cardiac transcription factors – NKX2.5, TBX5, and GATA4 – interact during heart development. They first proved that these transcription factors are essential for the formation of the heart in mouse embryos. When they eliminated the presence of one of the three factors from the developing mouse embryo, they observed abnormal heart development and heart defects. When they removed two factors (NKX2.5 and TBX5), the results were even worse – the heart wasn’t able to form and none of the embryos survived.
Normal cardiomyocytes or heart cells, courtesy Kyoto University
Next, they studied how these transcription factors interact to coordinate gene expression in heart cells called cardiomyocytes made from mouse embryonic stem cells that lacked either NKX2.5, TBX5, or both of these factors. Compared to normal heart cells, cardiomyocytes that lacked one or both of these two transcription factors started beating at inappropriate times – either earlier or later than the normal heart cells.
Taking a closer look, the scientists discovered that TBX5, NKX2.5 and GATA4 all hangout in the same areas of the genome in embryonic stem cells that are transitioning into cardiomyocytes. In fact, each individual transcription factor required the presence of the others to bind their DNA targets. If one of these factors was missing and the love triangle was broken, the remaining transcription factors became confused and bound random DNA sequences in the genome, causing a mess by turning on genes that shouldn’t be on.
First author on the study, Luis Luna-Zurita, explained the importance of maintaining this cardiac love triangle in a Gladstone Press Release:
Luis Luna-Zurita, Gladstone Institute
“Transcription factors have to stick together, or else the other one goes and gets into trouble. Not only are these transcription factors vital for turning on certain genes, but their interaction is important to keep each other from going to the wrong place and turning on a set of genes that doesn’t belong in a heart cell.”
The last part of the study proved that two of these factors, NKX2.5 and TBX5, directly interact and physically touch each other when they bind their DNA targets. In collaboration with a group from the European Molecular Biology Laboratory (EMBL) in Germany, they developed protein crystal structures to model the molecular structure of these transcription factors when they bind DNA.
Co-author and EMBL scientist Christoph Muller explained his findings:
“The crystal structure critically shows the interaction between two of the transcription factors and how they influence one another’s binding to a specific stretch of DNA. Our detailed structural analysis revealed a direct physical connection between TBX5 and NKX2-5 and demonstrated that DNA plays an active role in mediating the interaction between the two proteins.”
Big picture
While this study falls in the discovery research category, its findings increase our understanding of the steps required to make a healthy heart and sheds light on what goes wrong in patients or newborns with heart disease.
Senior author on the paper and Gladstone Professor Benoit Bruneau explained the biomedical applications of their study for treating human disease:
Benoit Bruneau, Gladstone Institute
“Gene mutations that cause congenital heart disease lower the levels of these transcription factors by half, and we’ve shown that the dosage of these factors determines which genes are turned on or off in a cell. Other genetic variants that cause heart defects like arrhythmias also affect the function of these factors. Therefore, the better we understand these transcription factors, the closer we’ll come to a treatment for heart disease. Our colleagues at Gladstone are using this knowledge to search for small molecules that can affect gene regulation and reverse some of the problems caused by the loss of these transcription factors.”
I think it’s worth mentioning that these studies were done using mouse embryos and mouse embryonic stem cells. Future work should be done to determine whether this cardiac love triangle and the same transcription factor interactions exist in human heart cells.
As part of our CIRM scholar series, we feature the research accomplishments of students and postdocs that have received CIRM funding.
Jessica Gluck, CIRM Scholar
I’d like to introduce you to one of our CIRM Scholars, Jessica Gluck. She’s currently a Postdoctoral Fellow at UC Davis working on human stem cell models of heart development. Jessica began her education in textiles and materials science at North Carolina State University, but that developed into a passion for biomedical engineering and stem cell research, which she pursued during her PhD at UC Los Angeles. During her graduate research, Jessica developed 3D bio-scaffolds that help human stem cells differentiate into functioning heart cells.
We asked Jessica to discuss her latest foray in the fields of stem cells and heart development.
Q: What are you currently working on in the lab?
JG: I work as a postdoc at UC Davis in the lab of Deborah Lieu. She’s working on developing pacemaking cardiomyocytes (heart cells) from human induced pluripotent stem cells (iPS cells). Pacemaking cells are the cells of the heart that are in charge of rhythm and synchronicity. Currently, we’re able to take iPS cells and get them to a cardiomyocyte state, but we want to further develop them into a pacemaking cell.
So ultimately, we’re trying to make a biological pacemaker. We can figure out how we can make a cell become the cell that tells your heart to beat, and there’s two things we can get out of that. First, if we understand how we get these beating cells, the ones that are telling the other heart cells to beat, we might be able to understand how different heart diseases progress, and we might be able to come up with a new way to prevent or treat that disease. Second, if we understand how we’re getting these pacemaking cells, we could hopefully bioengineer a biological pacemaker so you wouldn’t necessarily need an electronic pacemaker. With a biological one, a patient wouldn’t have to go back to the doctor to have their battery replaced. And they wouldn’t have to have multiple follow up surgeries throughout their life.
Q: What models are you using to study these pacemaking cells?
JG: I’m looking at my project from two different directions. On one side, we’re using a pig model, and we’re isolating cells from the sinoatrial (SA) node, which is where the pacemaking cells actually reside in your heart. And there’s really not that many of these cells. You probably have about a billion cells in your heart, but there’s maybe 100,000 of these pacemaking cells that are actually controlling the uniform beating of the heart. So we’re looking at the native SA node in the pig heart to see if it’s structurally any different than ventrical or atrial heart tissue.
Diagram of the heart depicting the Sinoatrial Node. (Image from Texas Heart Institute)
We’ve found that the SA node is definitely different. So we’re de-cellularizing that tissue (removing the cells but not the matrix, or support structure, that keeps them in place) thinking that we could use the native matrix as a scaffold to help guide these heart cells to become the pacemaking phenotype. On the other side, we’re taking dishes with a known elasticity and we’re coating them with different proteins to see if we can tease out if there’s something that an individual protein does or a certain stiffness that actually is part of the driving force of making a pacemaking cell. We’ve gotten some pretty good preliminary results. So hopefully the next phase will be seeing how functional the cells are after they’ve been on these de-cellularized matrices.
Q: Why does your lab work with pig models?
JG: Pig hearts are pretty close to the human heart – their anatomy is pretty similar. To give you context, a pig heart is slightly larger than the size of your two hands clasped together. But the SA node, when you isolate it out, is only a couple of millimeters squared. It’s a lot smaller than we originally thought, and if we had gone with a smaller animal model, we wouldn’t be able to tangibly study or manipulate the SA node area. Because we are at UC Davis, we have a Meat Lab on campus, and we are able to get the pig hearts from them.
Q: Have you run into any road blocks with your research?
JG: For anybody that’s working with cardiomyocytes, the biggest problem is getting stem cells to become mature cardiomyocytes. Some labs have shown that you can get cells to a more mature cardiomyocyte after it’s been in culture for almost 100 days, but that’s not exactly feasible or that helpful.
We’ve been able to isolate out a small population of cells that we’re pretty sure are pacemaking cells. Over the last year, we’ve realized that a lot of the information that we thought we knew about pacemaking cells isn’t necessarily specific to pacemaking cells. Many of the biological markers that people have published in the literature are present in pacemaking cells, but we realized that they are also present in other heart cells like atrial cells, just in a lower amount. So we haven’t really been able to pick one specific biomarker that we’ve been able to say, yes this is actually a pacemaking cell. Instead, we have a small percentage of cells that we’re able to study. But we’re trying to figure out if there’s a way that we could increase our yield, or if there’s something fundamentally different about the environment that would also increase the yield of these pacemaking cells. So we’ve had a lot of trouble shooting along the way.
Q: What was your experience like as a CIRM scholar?
JG: I became a CIRM scholar in the spring of 2014. It was through the UC Davis Stem Cell Training Program. The opportunity was very helpful for me because it was in my first year as a postdoc at Davis. I earned my PhD at UCLA, so I was dealing with being on a new campus, trying to figure out whose lab I could go to to borrow random things and where to find equipment that I needed to use. So it was helpful to be around a group of other people that were also doing stem cell projects. Even though a lot of us were focused on different areas, it was still helpful to talk to other people, especially if you get somebody’s perspective that isn’t necessarily in your field. They might come up with a random idea that you haven’t thought of before.
Over the course of the year, we had a journal club, which was always interesting to see what’s going on in the field. I also went to the annual International Society for Stem Cell Research meeting in Vancouver using CIRM funding. And as part of the program, we also worked with the CIRM Bridges program between UC Davis and Cal State Sacramento. There were Bridges master’s students that were there with us. It was interesting to hear their take on everything, and they were very enthusiastic. We have had two master’s students work in our lab. I think it was very beneficial to them because they got a lot of hands on training and both have gone on to jobs in the regenerative medicine field.
Q: What is the future of stem cell research?
JG: If you’re looking at heart disease and stem cell treatments, there’s been some interesting clinical trials that have come out that have some promising results. I think that for a couple of those studies, people might have jumped the gun a little getting the treatments into the clinic. There’s still a lot that people should study in the lab before we move on to clinical trials. But I do think that we will see something in the next 20 years where stem cell research is going to have a huge therapeutic benefit. The field is just moving so quickly, and I think it will be really interesting to see what advances are made.
For our research, I’ve always been fairly realistic, and unfortunately, I don’t think we will see this biological pacemaker any time soon. But I think that the research that we produce along the way will be very beneficial to the field and our work will hopefully improve the foundation of what is known about pacemaking cells. What I think is really interesting about our lab’s work, is that we are moving into a 3D culture environment. Cells behave very differently in the body as opposed to on a plastic petri dish. So I think it’s very encouraging that we are seeing a lot more labs moving towards a more physiologically relevant model.
Q: What are your future goals?
I’ve been lucky that I’ve been able to work with very well established professors and also brand new faculty. But I’ve seen how difficult the funding climate is – it’s very daunting. So I’m really not sure what will happen next, and I’m keeping my options open.
I’ve really enjoyed working with our undergraduate and graduate students. I’ve gotten involved with outreach programs in Sacramento that promote science to young kids. It’s something that I’ve really enjoyed, and it’s very interesting telling people that I work in stem cells. Middle school kids seem to think that stem cells are magic. It’s fun to explain the very basics of stem cells and to see the light bulb moment where they understand it. I’m hoping to end up in a career that is still within the stem cell field but more towards teaching or outreach programs.
Q: What is your favorite thing about being a scientist?
JG: The thing I really like is having a puzzle that you’re trying to figure out the answer to. It’s great because every time you answer one question, that answer is going to lead you to at least three or four more new questions. I think that that’s really interesting especially trying to figure out how all the puzzle pieces fit together, and I’ve really enjoyed getting to work with people in very different fields. My parents think its funny because they said even as a little kid, I hated not knowing the answers to questions – and still do! They were completely understanding as to why I stayed in school as long as I did.
You can learn more about Jessica’s research by following her on Twitter: @JessicaGluckPhD
Images of clusters of heart muscle cells (in red and green) derived from human embryonic stem cells 40 days after transplantation. Courtesy UCLA
Every year more than 735,000 Americans have a heart attack. Many of those who survive often have lasting damage to their heart muscle and are at increased risk for future attacks and heart failure. Now CIRM-funded researchers at UCLA have identified a way that could help regenerate heart muscle after a heart attack, potentially not only saving lives but also increasing the quality of life.
The researchers used human embryonic stem cells to create a kind of cell, called a cardiac mesoderm cell, which has the ability to turn into cardiomyocytes, fibroblasts, smooth muscle, and endothelial cells. All these types of cells play an important role in helping repair a damaged heart.
As those embryonic cells were in the process of changing into cardiac mesoderms, the team was able to identify two key markers on the cell surface. The markers, called CD13 and ROR2 – which makes them sound like extras in the latest Star Wars movie – pinpointed the cells that were likely to be the most efficient at changing into the kind of cells needed to repair damaged heart tissue.
The researchers then transplanted those cells into an animal model and found that not only did many of the cells survive but they also produced the cells needed to regenerate heart muscle and vessels.
Big step forward
The research was published in the journal Stem Cell Reports. Dr. Reza Ardehali, the senior author of the CIRM-funded study, says this is a big step forward in the use of embryonic stem cells to help treat heart attacks:
“In a major heart attack, a person loses an estimated 1 billion heart cells, which results in permanent scar tissue in the heart muscle. Our findings seek to unlock some of the mysteries of heart regeneration in order to move the possibility of cardiovascular cell therapies forward. We have now found a way to identify the right type of stem cells that create heart cells that successfully engraft when transplanted and generate muscle tissue in the heart, which means we’re one step closer to developing cell-based therapies for people living with heart disease.”
More good news
But wait, as they say in cheesy TV infomercials, there’s more. Ardehali and his team not only found the markers to help them identify the right kinds of cell to use in regenerating damaged heart muscle, they also found a way to track the transplanted cells so they could make sure they were going where they wanted them to, and doing what they needed them to.
In a study published in Stem Cells Translational Medicine, Ardehali and his team used special particles that can be tracked using MRI. They used those particles to label the cardiac mesoderm cells. Once transplanted into the animal model the team was able to follow the cells for up to 40 days.
Ardehali says knowing how to identify the best cells to repair a damaged heart, and then being able to track them over a long period, gives us valuable tools to use as we work to develop better, more effective treatments for people who have had a heart attack.
CIRM is already funding a Phase 2 clinical trial, run by a company called Capricor, using stem cells to treat heart attack patients.
The Stem Cellar 