Patching up a Broken Heart with FSTL1

Get-Over-Heartbreak-Step-08How do you mend a broken heart? It’s a subject that songwriters have pondered for generations, without success. But if you pose the same question to a heart doctor, they would give you a number of practical options that focus on the prevention or management of the physical symptoms you are dealing with.

That’s because heart disease is complicated. There are many different types of diseases that affect the health and function of the heart. And once damage happens to your heart, say from a heart attack, it’s really hard to fix.

New regenerative factor for heart disease

Scientists from Stanford University, the University of California, San Diego, and the Sanford-Burnham-Prebys Medical Discovery Institute have teamed up to figure out how to fix a broken heart. In a CIRM-funded study published today in the journal Nature, the group reported that the gene follistatin-like 1 (FSTl1) has the ability to regenerate heart tissue when it’s delivered within a patch to the injured heart.

2004_Heart_Wall

The different layers of the heart.

The wall of the heart is made up of three different layers: the endocardium (inner), myocardium (middle), and epicardium (outer). The epicardium not only protects the inner two layers of the heart, but also supports the growth of the fetal heart.

The group decided to study epicardial cells to determine whether these cells produced specific factors that protect or even regenerate adult heart tissue. They took epicardial cells from rodents and cultured them with heart cells (called cardiomyocytes), and found that the heart cells divided and reproduced much more quickly when cultured with the epicardial cells. This suggested that the epicardial cells might secrete factors that promote the expansion of the heart cells.

Patching up a broken heart

They next asked whether factors secreted from epicardial cells could improve heart function in mice after heart injury. They designed and engineered tiny patches that contained a cocktail of special epicardial factors and sewed them onto the heart tissue of mice that had just experienced the equivalent of a human heart attack. When they monitored these mice two weeks later, they saw an improvement in heart function in mice with the patch compared to mice without.

When they analyzed the cocktail of epicardial factors in the patch, they identified one factor that had potential for regenerating heart tissue. It was FSTL1. To test its regenerative abilities, they cultured rodent heart cells in a dish and treated them with FSTL1 protein. This treatment caused the heart cells to divide like crazy, thus proving that FSTL1 had regenerative qualities.

Moving from the dish into animal models, the scientists explored which layers of the heart FSTL1 was expressed in after heart injury. In healthy hearts, FSTL1 is expressed in the epicardium. However, in injured hearts, they found that FSTL1 expression was missing in the epicardium and was instead present in the middle layer of the heart, the myocardium.

FSTL1 to the rescue

patch

Cross sections of a healthy (control) or injured mouse heart. Injured hearts treated with patches containing FSTL1 show the most recovery of healthy heart tissue (red). Image adapted from Wei et al. 2015)

In a eureka moment, the scientists decided to add a FSTL1 protein back to the epicardial layer of the heart, post heart injury, using the same patch system they used earlier in mice, to see whether this would promote heart tissue regeneration. Their guess was correct. FSTL1 delivery through the engineered epicardium patch system resulted in a number of beneficial effects to the heart including better function and survival, reduced scar tissue build up (a consequence of heart injury), and increased blood flow to the area of the patch.

Upon further inspection, they found that the FSTL1 epicardial patch caused heart cells to divide and proliferate. The same effect did not happen when FSTL1 is expressed in the myocardium layer of the injured heart.

To make sure their findings translated to other animal models, they studied the regenerative effects of FSTL1 in a pig model of heart injury. They applied patches infused with FSTL1 to the injured heart and as expected, observed that FSTL1 delivery improved symptoms and caused heart cells to divide.

No more heartbreak?

The authors concluded that heart injury turns off the activity of an important factor, FSTL1, in specific heart cells needed for heart regeneration. By turning on FSTL1 back on in the epicardium after injury, heart cells will receive the signal to divide and regenerate heart tissue.

Co-first author and CIRM postdoctoral scholar Ke Wei spoke to CIRM about the next steps for this study and its relevance:

Ke Wei

Co-first author, Ke Wei

In the future, we hope that our engineered epicardium patch technology can be used as a clinical platform to deliver drugs or cells to the injured heart. This strategy differs from conventional tools to treat heart attack, and may provide a novel approach in our repertoire battling heart diseases.

Thus it seems that scientists have found a potential way to patch-up a broken heart and to extend a lifeline for those suffering from heart disease. It’s comforting to know that the regenerative abilities of FSTl1 will be explored in human models and will hopefully reach clinical trials.

Ke Wei (UCSD, Sanford-Burnham-Prebys) and Vahid Serpooshan (Stanford) were co-first authors on this study. The senior authors were Daniel Bernstein (Stanford), Mark Mercola (UCSD, Sanford-Burnham-Prebys), and Pilar Ruiz-Lozano (Stanford). Both Ke Wei and Mark Mercola received CIRM funding for this study.


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New Regenerative Liver Cells Identified

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.

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.

Hybrid hepatocytes (shown in green) divide and regenerate the liver in response to injury. (Image source: Font-Burgada et al., 2015)

Hybrid hepatocytes (green) divide and regenerate the liver in response to injury. (Image source: Font-Burgada et al., 2015)

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 Fellow Jean Font-Burgada

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.


Related links:

UCSD Press Release

CIRM Spotlight on Liver Disease Research

CIRM Spotlight on Living with Liver Disease

Building a Bridge to Therapies: Stem Cell-Derived Neurons Restore Feeling to Injured Limbs

It’s been a great week for spinal cord injury-related stem cell research – and it’s only Tuesday. In case you missed it, Asterias Biotherapeutics announced yesterday that they had treated their first clinical trial participant with an embryonic stem cell-based therapy for complete spinal cord injury. “Complete” refers to injuries that cause a total loss of feeling and movement below the site of injury.

Transplant human neurons (red) provide a bridge for the mice nerve fibers (green) to enter the spinal cord (spc). Image credit Hoeber et al. Scientific Reports

Transplanted human neurons (red) provide a bridge for the mice nerve fibers (green) to enter the spinal cord surface (spc). Image credit: Hoeber et al. Scientific Reports 5:10666

In another study also reported yesterday in Nature’s Scientific Reports, researchers at Uppsala University in Sweden made significant progress toward understanding and treating a related but different sort of injury that disrupts nerve signals coming into and out of the spinal cord. These so-called avulsion injuries are frequently seen after traffic, particularly motorcycle, accidents and lead to paralysis, loss of sensation, and chronic pain in the affected limbs. Although the ruptured nerve fibers from the limbs have the ability to extend back toward the spinal cord, inflammation from the site of injury makes the spinal cord impenetrable and blocks any restoration of normal sensory function.

To explore the potential of overcoming this spinal cord barrier, the research team transplanted human embryonic stem cell-derived neurons into mice mimicking human avulsion injury. Five months after the transplant, growth of nerve fibers into the spinal cord was seen. But these nerve fibers that had reconnected with the spinal cord were host animal cells and not the transplanted human stem cell-derived neurons. It turns out the human neuron fibers provide a physical bridge permitting the mouse nerve fibers to extend into the spinal cord. The human neurons also encourage this regrowth by releasing proteins that reduce the scar left by the injury and promote nerve fiber growth. The reconnected nerve fibers is an exciting result but did it have any impact on the animals? The answer is yes. Using standard behavior tests the team found that injured mice with the transplanted neurons had more sensitivity to touch stimulation and greater grip strength compared to untreated injured mice.

Because stem cells have the ability for unlimited growth, any future therapy based on these findings must shown that the transplant doesn’t lead to excessive cell growth. In an encouraging sign, no tumor formation or extreme growth of human neurons in the animals were observed.

Stem cells and professional sports: a call for more science and less speculation

In the world of professional sports, teams invest tens of millions of dollars in players. Those players are under intense pressure to show a return on that investment for the team, and that means playing as hard as possible for as long as possible. So it’s no surprise that players facing serious injuries will often turn to any treatment that might get them back in the game.

image courtesy Scientific American

image courtesy Scientific American

A new study published last week in 2014 World Stem Cell Report (we blogged about it here) highlighted how far some players will go to keep playing, saying at least 12 NFL players have undergone unproven stem cell treatments in the last five years. A session at the recent World Stem Cell Summit in San Antonio, Texas showed that football is not unique, that this is a trend in all professional sports.

Dr. Shane Shapiro, an orthopedic surgeon at the Mayo Clinic, says it was an article in the New York Times in 2009 about two of the NFL players named in the World Stem Cell Report that led him to becoming interested in stem cells. The article focused on two members of the Pittsburgh Steelers team who were able to overcome injuries and play in the Super Bowl after undergoing stem cell treatment, although there was no direct evidence the stem cells caused the improvement.

“The next day, the day after the article appeared, I had multiple patients in my office with copies of the New York Times asking if I could perform the same procedure on them.”

Dr. Shapiro had experienced what has since become one of the driving factors behind many people seeking stem cell therapies, even ones that are unproven; the media reports high profile athletes getting a treatment that seems to work leading many non-athletes to want the same.

“This is not just about high profile athletes it’s also about older patients, weekend warriors and all those with degenerative joint disease, which affects around 50 million Americans. Currently for a lot of these degenerative conditions we don’t have many good non- surgical options, basically physical therapy, gentle pain relievers or steroid injections. That’s it. We have to get somewhere where we have options to slow down this trend, to slow down the progression of these injuries and problems.”

Shapiro says one of the most popular stem cell-based approaches in sports medicine today is the use of plasma rich platelets or PRP. The idea behind it makes sense, at least in theory. Blood contains platelets that contain growth factors that have been shown to help tissue heal. So injecting a patient’s platelets into the injury site might speed recovery and, because it’s the patient’s own platelets, the treatment probably won’t cause any immune response or prove to be harmful.

That’s the theory. The problem is few well-designed clinical trials have been done to see if that’s actually the case. Shapiro talked about one relatively small, non-randomized study that used PRP and in a 14-month follow-up found that 83% of patients reported feeling satisfied with their pain relief. However, 84% of this group did not have any visible improved appearance on ultrasound.

He is now in the process of carrying out a clinical trial, approved by the Food and Drug Administration (FDA), using bone marrow aspirate concentrate (BMAC) cells harvested from the patient’s own bone marrow. Because those cells secrete growth factors such as cytokines and chemokines they hope they may have anti-inflammatory and regenerative properties. The cells will be injected into 25 patients, all of whom have arthritic knees. They hope to have results next year.

Dr. Paul Saenz is a sports medicine specialist and the team physician for the San Antonio Spurs, the current National Basketball Association champions. He says that sports teams are frequently criticized for allowing players to undergo unproven stem cell treatments but he says it’s unrealistic to expect teams to do clinical studies to see if these therapies work, that’s not their area of expertise. But he also says team physicians are very careful in what they are willing to try.

“As fervent as we are to help bring an athlete back to form, we are equally fervent in our desire not to harm a $10 million athlete. Sports physicians are very conservative and for them stem cells are never the first thing they try, they are options when other approaches have failed.”

Saenz said while there are not enough double blind, randomized controlled clinical trials he has seen many individual cases, anecdotal evidence, where the use of stem cells has made a big difference. He talked about one basketball player, a 13-year NBA veteran, who was experiencing pain and mobility problems with his knee. He put the player on a biologic regimen and performed a PRP procedure on the knee.

“What we saw over the next few years was decreased pain, and a dramatic decrease in his reliance on non-steroidal anti inflammatory drugs. We saw improved MRI findings, improved athletic performance with more time on court, more baskets and more rebounds.”

But Saenz acknowledges that for the field to advance anecdotal stories like this are not enough, well-designed clinical trials are needed. He says right now there is too much guesswork in treatments, that there is not even any agreement on best practices or standardized treatment protocols.

Dr. Shapiro says for too long the use of stem cells in sports medicine has been the realm of individual physicians or medical groups. That has to change:

“If we are ever to move forward on this it has to be opened up to the scientific community, we have to do the work, do the studies, complete the analysis, open it up to our peers, report it in a reputable journal. If we want to treat the 50 million Americans who need this kind of therapy we need to go through the FDA approval process. We can’t just continue to treat the one patient a month who can afford to pay for all this themselves. “