Stories that caught our eye: $20.5 million in new CIRM discovery awards, sickle cell disease cell bank, iPSC insights

CIRM Board launches a new voyage of Discovery (Kevin McCormack).
Basic or early stage research is the Rodney Dangerfield of science; it rarely gets the respect it deserves. Yesterday, the CIRM governing Board showed that it not only respects this research, but also values its role in laying the foundation for everything that follows.

The CIRM Board approved 11 projects, investing more than $20.5 million in our Discovery Quest, early stage research program. Those include programs using gene editing techniques to develop a cure for a rare but fatal childhood disease, finding a new approach to slowing down the progress of Parkinson’s disease, and developing a treatment for the Zika virus.

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Electron micrograph of Zika virus (red circles). Image: CDC/Cynthia Goldsmith

The goal of the Discovery Quest program is to identify and explore promising new stem cell therapies or technologies to improve patient care.

In a news release Randy Mills, CIRM’s President & CEO, said we hope this program will create a pipeline of projects that will ultimately lead to clinical trials:

“At CIRM we never underestimate the importance of early stage scientific research; it is the birth place of groundbreaking discoveries. We hope these Quest awards will not only help these incredibly creative researchers deepen our understanding of several different diseases, but also lead to new approaches on how best to use stem cells to develop treatments.”

Creating the world’s largest stem cell bank for sickle cell disease (Karen Ring).
People typically visit the bank to deposit or take out cash, but with advancements in scientific research, people could soon be visiting banks to receive life-saving stem cell treatments. One of these banks is already in the works. Scientists at the Center for Regenerative Medicine (CReM) at Boston Medical Center are attempting to generate the world’s largest stem cell bank focused specifically on sickle cell disease (SCD), a rare genetic blood disorder that causes red blood cells to take on an abnormal shape and can cause intense pain and severe organ damage in patients.

To set up their bank, the team is collecting blood samples from SCD patients with diverse ethnic backgrounds and making induced pluripotent stem cells (iPSCs) from these samples. These patient stem cell lines will be used to unravel new clues into why this disease occurs and to develop new potential treatments for SCD. More details about this new SCD iPSC bank can be found in the latest edition of the journal Stem Cell Reports.

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Gustavo Mostoslavsky, M.D., PH.D., Martin Steinberg, M.D., George Murphy PH.D.
Photo: Boston Medical Center

In a news release, CReM co-founder and Professor, Gustavo Mostoslavsky, touched on the future importance of their new stem cell bank:

“In addition to the library, we’ve designed and are using gene editing tools to correct the sickle hemoglobin mutation using the stem cell lines. When coupled with corrected sickle cell disease specific iPSCs, these tools could one day provide a functional cure for the disorder.”

For researchers interested in using these new stem cell lines, CReM is making them available to researchers around the world as part of the NIH’s NextGen Consortium study.

DNA deep dive reveals ways to increase iPSC efficiency (Todd Dubnicoff)
Though the induced pluripotent stem (iPS) cell technique was first described ten years ago, many researchers continue to poke, prod and tinker with the method which reprograms an adult cell, often from skin, into an embryonic stem cell-like state which can specialize into any cell type in the body. Though this breakthrough in stem cell research is helping scientists better understand human disease and develop patient-specific therapies, the technique is hampered by its low efficiency and consistency.

This week, a CIRM-funded study from UCLA reports new insights into the molecular changes that occur during reprogramming that may help pave the way toward better iPS cell methods. The study, published in Cell, examined the changes in DNA during the reprogramming process.

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Senior authors Kathrin Plath and Jason Ernst and first authors Petko Fiziev and Constantinos Chronis.
Photo: UCLA

In a skin cell, the genes necessary for embryonic stem cell-like, or pluripotent, characteristics are all turned off. One way this shut down in gene activity occurs is through tight coiling of the DNA where the pluripotent genes are located. This physically blocks proteins called transcriptions factors from binding the DNA and activating those pluripotent genes within skin cells. On the other hand, regions of DNA carrying skin-related genes are loosely coiled, so that transcription factors can access the DNA and turn on those genes.

The iPS cell technique works by artificially adding four pluripotent transcriptions factors into skin cells which leads to changes in DNA coiling such that skin-specific genes are turned off and pluripotent genes are turned on. The UCLA team carefully mapped the areas where the transcription factors are binding to DNA during the reprogramming process. They found that the shut down of the skin genes and activation of the pluripotent genes occurs at the same time. The team also found that three of the four iPS cell factors must physically interact with each other to locate and activate the areas of DNA that are responsible for reprogramming.

Using the findings from those experiments, the team was able to identify a fifth transcription factor that helps shut down the skin-specific gene more effectively and, in turn, saw a hundred-fold increase in reprogramming efficiency. These results promise to help the researchers fine-tune the iPS cell technique and make its clinical use more practical.

Has the promise of stem cells been overstated?

One of the most famous stem cell scientists in the world said on Monday that the promise of stem cell treatments has in some ways been overstated.

In an interview with the New York Times, Dr. Shinya Yamanaka, one of the recipients of the 2012 Nobel Prize in Medicine for his discovery of induced pluripotent stem cells (iPS cells), said, “we can help just a small portion of patients by stem cell therapy.”

Shinya Yamanaka. (Image source: Ko Sasaki, New York Times)

Shinya Yamanaka. (Image source: Ko Sasaki, New York Times)

He explained that there are only 10 target diseases that he believes will benefit directly from stem cell therapies including, “Parkinson’s, retinal and corneal diseases, heart and liver failure, diabetes, spinal cord injury, joint disorders and some blood disorders. But maybe that’s all. The number of human diseases is enormous.”

This is a big statement coming from a key opinion leader in the field of stem cell research, and it’s likely to spur a larger conversation on the future of stem cell treatments.

Yamanaka also touched on another major point in his interview – progress takes time.

In the ten years since his discovery of iPS cells, he and other scientists have learned the hard way that the development of stem cell treatments can be time consuming. While autologous iPS cell treatments (making stem cell lines from a patient and transplanting them back into that patient) have entered clinical trials to treat patients with macular degeneration, a disease that causes blindness, the trials have been put on hold until the safety of the stem cell lines being used are confirmed.

At the World Alliance Forum in November, Yamanaka revealed that generating a single patient iPS cell line can cost up to one million dollars which isn’t feasible for the 1000’s of patients who need them. He admitted that the fate of personalized stem cell medicine, which once seemed so promising, now seems unrealistic because it’s time consuming and costly.

But with any obstacle, there is always a path around it. Under Yamanaka’s guidance, Japan is generating donor iPS cell lines that can be used to treat a large portion of the Japanese population. Yamanaka said that 100 lines would cover 100 million people in Japan and that 200 lines would be enough to cover the US population. iPS cell banks are being generated around the world, meaning that one day the millions of people suffering from the target diseases Yamanaka mentioned could be treated or even cured. Would this not fulfill a promise that was made about the potential of stem cell treatments?

Which brings me to my point, I don’t believe the promise of stem cells has been overstated. I think that it has yet to be realized, and it will take more research and more time to get there. As a community, we need to be understanding, patient, and supportive.

In my opinion (as a scientist aside from my role at CIRM), I believe that Yamanaka’s interview failed to reveal his optimism about the future of stem cell treatments. What I took from Yamanaka’s comments is that stem cell treatments can help a small number of patients with specific diseases right now. That’s not to say that stem cell research won’t produce promising treatments for other diseases in the future.

Retinal diseases and blood disorders are easier to target with stem cell treatments because only one type of cell needs to be replaced. It makes sense to tackle those diseases first and make sure that these stem cell treatments are effective and safe in patients before we focus on more complicated diseases where multiple cell types or organs are involved.

Part of the reason why scientists are unsure whether stem cell treatments can treat complex diseases is because we still don’t know the details of what causes these diseases. After we know more about what’s going wrong, including all the cell types and molecules involved, research might reveal new ways that stem cells could be used to help treat those diseases. Or on the other hand, stem cells could be used to model those diseases to help discover new drug treatments.

I’ve heard Yamanaka talk many times and recently I heard him speak at the World Alliance Forum in November, where he said that the two biggest hurdles we are facing for stem cell treatments to be successful is time and cost. After we overcome these hurdles, his outlook was optimistic that stem cell treatments could improve people’s lives. But he stressed that these advances will take time.

He shared a similar sentiment at the very end of the NY Times interview by referencing his father’s story and the decades it took to cure hepatitis C,

“You know, my father had a small factory. He injured his leg in the factory when I was in junior high. He had a transfusion, and he got hepatitis C. He passed away in 1989. Twenty-five years later, just two years ago, scientists developed a very effective cure. We now have a tablet. Three months and the virus is gone — it’s amazing. But it took 25 years. iPS cells are only 10 years old. The research takes time. That’s what everybody needs to understand.”

Yamanaka says more time is needed for stem cell treatments to become effective cures, but CIRM has already witnessed success. In our December Board meeting, we heard from two patients who were cured of genetic blood diseases by stem cell treatments that CIRM funded. One of them was diagnosed with severe combined immunodeficiency (SCID) and the other had chronic granulomatous disease (CGD). Both had their blood stem cells genetically engineered to removed disease-causing mutations and then transplanted back into their body to create a healthy immune system and cure them of their disease.

Hearing how grateful these patients and their families were to receive life-saving stem cell treatments and how this research brings new hope to other patients suffering from the same diseases, in my mind, fulfills the promise of stem cell research and makes funding stem cell treatments worth it.

I believe we will hear more and more of these success stories in the next decade and CIRM will most certainly play an important role in this future. There are others in the field who share a similar optimism for the future of stem cell treatments. Hank Greely, the Director for Law and the Biosciences at Stanford University, said in an interview with the Sacramento Bee about the future of CIRM,

Hank Greely, Stanford University

Hank Greely, Stanford University

“The next few years should determine just how good California’s investment has been. It is encouraging to see CIRM supporting so many clinical trials; it will be much more exciting when – and I do expect ‘when’ and not ‘if’ – one of those trials leads to an approved treatment.”

 


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Stories that caught our eye: frail bones in diabetics, ethics of future IVF, Alzheimer’s

The connection between diabetes and frail bones uncovered
Fundamentally, diabetes is defined by abnormally high blood sugar levels. But that one defect over time carries an increased risk for a wide range of severe health problems. For instance, compared to healthy individuals, type 2 diabetics are more prone to poorly healing bone fractures – a condition that can dramatically lower one’s quality of life.

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Bones of the healthy animals (top) form larger calluses during healing which lead to stronger repaired bones. Bones of the diabetic mice (bottom) have smaller calluses and the healed bones are more brittle. Image: Stanford University

To help these people, researchers are trying to tease out how diabetes impacts bone health. But it’s been a complicated challenge since there are many factors at play. Is it from potential side effects of diabetes drugs? Or is the increased body weight associated with type 2 diabetes leading to decreased bone density? This week a CIRM-funded team at Stanford pinpointed skeletal stem cells, a type of adult stem cell that goes on to make all the building blocks of the bone, as important pieces to this scientific puzzle.

Reporting in Science Translational Medicine, the team, led by Michael Longaker – co-director of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine – found that, compared to healthy animals, type 2 diabetic mice have a reduced number of skeletal stem cells after bone fracture. A study of the local cellular “neighborhood” of these stem cells showed that the diabetic mice also had a reduction in the levels of a protein called hedgehog. Blocking hedgehog activity in healthy mice led to the slow bone healing seen in the diabetic mice. More importantly, boosting hedgehog levels near the site of the fracture in diabetic mice lead to bone healing that was just as good as in the healthy mice.

To see if this result might hold up in humans, the team analyzed hedgehog levels in bone samples retrieved from diabetics and non-diabetics undergoing joint replacement surgeries. Sure enough, hedgehog was depleted in the diabetic bone exactly reflecting the mouse results.

Though more studies will be needed to develop a hedgehog-based treatment in humans, Longaker talked about the exciting big picture implications of this result in a press release:

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Michael Longaker

“We’ve uncovered the reason why some patients with diabetes don’t heal well from fractures, and we’ve come up with a solution that can be locally applied during surgery to repair the break. Diabetes is rampant worldwide, and any improvement in the ability of affected people to heal from fractures could have an enormously positive effect on their quality of life.”

 

Getting the ethics ahead of the next generation of fertility treatments
The Business Insider ran an article this week with a provocative title, “Now is the time to talk about creating humans from stem cells.” I initially read too much into that title because I thought the article was advocating the need to start the push for the cloning of people. Instead, author Rafi Letzter was driving at the importance for concrete, ethical discussion right now about stem cell technologies for fertility treatments that may not be too far off.

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These mice were born from artificial eggs that were made from stem cells in a dish.
It’s great news for infertility specialist but carries many ethical dilemmas. 
(Image: K. Hayashi, Kyushu University)

In particular, he alludes to a paper from October (read our blog about it) that reported the creation of female mouse eggs from stem cells. These eggs were fertilized, implanted into the mother and successfully developed into living mice. What’s more, one set of stem cells were derived from mouse skin samples via the induced pluripotent stem cell method. This breakthrough could one day make it possible for an infertile woman to simply go through a small skin biopsy or mouth swab to generate an unlimited number of eggs for in vitro fertilization (IVF). Just imagine how much more efficient, less invasive and less costly this procedure could be compared to current IVF methods that require multiple hormone injections and retrieval of eggs from a woman’s ovaries.

But along with that hope for couples who have trouble conceiving a child comes a whole host of ethical issues. Here, Letzter refers to a perspective letter published on Wednesday in Science Translation Medicine by scientists and ethicists about this looming challenge for researchers and policymakers.

It’s an important read that lays out the current science, the clinical possibilities and regulatory and ethical questions that must be addressed sooner than later. In an interview with Letzter, co-author Eli Adashi, from the Alpert Medical School at Brown University, warned against waiting too long to heed this call to action:

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Eli Adashi

“Let’s start the [ethical] conversation now. Like all conversations it will be time consuming. And depending how well we do it, and we’ve got to do it well, it will be demanding. It will not be wise to have that conversation when you’re seeing a paper in Science or Nature reporting the complete process in a human. That would not be wise on our collective part. We should be as much as possible ready for that.”

 

 

Tackling Frontotemporal dementia and Alzheimer’s by hitting the same target.
To develop new disease therapies, you usually need to understand what is going wrong at a cellular level. In some cases, that approach leads to the identification of a specific protein that is either missing or in short supply. But this initial step is just half the battle because it may not be practical to make a drug out of the protein itself. So researchers instead search for other proteins or small molecules that lead to an increase in the level of the protein.

A CIRM-funded project at the Gladstone Institutes has done just that for the protein called progranulin. People lacking one copy of the progranulin gene carry an increased risk for  frontotemporal dementia (FTD), a degenerative disease of the brain that is the most common cause of dementia in people under 60 years of age. FTD symptoms are often mistaken for Alzheimer’s. In fact, mutations in progranulin are also associated with Alzheimer’s.

Previous studies have shown that increasing levels of progranulin in animals with diseases that mimic FTP and Alzheimer’s symptoms can reverse symptoms. But little was known how progranulin protein levels were regulated in the cells. Amanda Mason, the lead author on the Journal of Biological Chemistry report, explained in a press release how they tackled this challenge:

“We wanted to know what might regulate the levels of progranulin. Many processes in biology are controlled by adding or removing a small chemical group called phosphate, so we started there.”

These phosphate groups hold a lot of energy in their chemical bonds and can be harnessed to activate or turn off the function of proteins and DNA. The team systematically observed the effects of enzymes that add and remove phosphate groups and zeroed in on one called Ripk1 that leads to increases in progranulin levels. Now the team has set their sights on Ripk1 as another potential target for developing a therapeutic that could be effective against both FTP and Alzheimer’s. Steve Finkbeiner, the team lead, gave a big picture perspective on these promising results:

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Steve Finkbeiner

“This is an exciting finding. Alzheimer’s disease was discovered over 100 years ago, and we have essentially no drugs to treat it. To find a possible new way to treat one disease is wonderful. To find a way that might treat two diseases is amazing.”

 

Eye on the prize: two stem cell studies restore vision in blind mice

For the 39 million people in the world who are blind, a vision-restoring therapy would be the ultimate prize. So far, this prize has remained out of reach, but two studies published this week have entered the ring as promising contenders in the fight against blindness.

In the red corner, we have a study published in Stem Cell Reports from the RIKEN Institute in Japan led by scientist Masayo Takahashi. Her team restored vision in blind mice with an advanced stage of retinal disease by transplanting sheets of light-sensing photoreceptor cells that were made from induced pluripotent stem cells (iPSCs).

In the blue corner, we have a study published in Cell Stem Cell from the Buck Institute in California led by scientist Deepak Lamba. His team restored long-term vision in blind mice by transplanting embryonic stem cell-derived photoreceptor cells and preventing the immune system from rejecting the transplant.

Transplanting Retinal sheets

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Synaptic integration of graft retina into model mouse
Credit: RIKEN

Let’s first talk about the Riken study led by Masayo Takahashi. She is well known for her pioneering work on iPSC-derived treatments for macular degeneration – a disease that damages the retina and causes blindness.

In previous work, Takahashi and her team transplanted sheets of mouse stem cell-derived retinal progenitor cells, which mature into light-sensing cells called photoreceptors, into the eyes of mice. The cells within the sheet formed connections with the resident cells in the mouse eye, proving the feasibility of transplanting retinal sheets to restore vision.

In their current study, published in Stem Cell Reports, Takahashi’s team found that the retinal sheets could restore vision in mice that had a very severe form of retinal disease that left them unable to see light. After the mice received the retinal transplants, they responded to light, which they were unable to do previously. Like their other findings, they found that the cells in the transplant made connections with the host cells in the eye including nerve cells that send light-sensing signals to the brain.

First author on the study, Michiko Mandai explained the importance of their findings and their future plans in a news release,

“These results are a proof of concept for using iPSC-derived retinal tissue to treat retinal degeneration. We are planning to proceed to clinical trials in humans after a few more necessary studies using human iPSC-derived retinal tissue in animals. Clinical trials are the only way to determine how many new connections are needed for a person to be able to ‘see’ again.”

While excited by their results, Mandai and the rest of the RIKEN team aren’t claiming the prize for a successful treatment that will cure blindness in people just yet. Mandai commented,

“We cannot expect to restore practical vision at the moment. We will start from seeing a simple light, then possibly move on to larger figures in the next stage.”

Blocking the immune system

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Image showing transplanted GFP-expressing human stem cell derived photoreceptors (green) integrated in a host rodent retina stained for Otx2 (red).
Credit Jie Zhu, Buck Institute for Research on Aging

In the Buck Institute study, Lamba and his team took on the challenge of answering a controversial question about why retinal cell transplants typically don’t survive long-term in the eye. Some scientists think that the transplanted cells die off over time because they don’t integrate into the eye while others think that they are rejected and killed off by the immune system.

To answer this question, Lamba transplanted human embryonic stem cell-derived retinal cells into immunodeficient mice that lacked a protein receptor that’s vital for a functioning immune system. The retinal cells transplanted into immunodeficient mice survived much better than retinal cells transplanted into normal mice and developed into ten times as many photoreceptors that integrated themselves into the host eye.

Their next step was to transplant the retinal cells into mice that were blind and also lacked the same immune receptor as the other mice. After the transplant, the blind mice became responsive to light and showed brain activity associated with sensing light. Their newfound ability to see lasted for nine months to a year following the transplant.

Lamba believes that backing down the immune response is responsible for the long-term vision restoration in the blind mice. He explained the importance of their findings in a Buck Institute news release,

“That finding gives us a lot of hope for patients, that we can create some sort of advantage for these stem cell therapies so it won’t be just a transient response when these cells are put in, but a sustained vision for a long time. Even though the retina is often considered to be ‘immune privileged,’ we have found that we can’t ignore cell rejection when trying to transplant stem cells into the eye.”

In the future, Lamba will explore the potential for using drugs that target the specific protein receptor they blocked earlier to improve the outcome of embryonic stem cell-derived retinal transplants,

“We can also potentially identify other small molecules or recombinant proteins to reduce this interleukin 2 receptor gamma activity in the body – even eye-specific immune responses – that might reduce cell rejection. Of course it is not validated yet, but now that we have a target, that is the future of how we can apply this work to humans.”

Who will be the winner?

The Buck Institute study is interesting because it suggests that embryonic stem cell-based transplants combined with immunosuppression could be a promising strategy to improve vision in patients. But it also begs the question of whether the field should focus instead on iPSC-based therapies where a patient’s own stem cells are used to make the transplanted cells. This strategy would side step the immune response and prevent patients from a taking a lifetime of immunosuppressive drugs.

However, I’m not saying that RIKEN’s iPSC-based strategy is necessarily the way to go for treating blindness (at least not yet). It takes a lot of time and money to make iPSC lines and it’s not feasible given our current output to generate iPSC lines for every blind patient.

So, it sounds like a winner in this fight to cure blindness won’t be announced any time soon. In the meantime, both teams need to conduct further preclinical studies before they can move on to testing these treatments in human clinical trials.

Here at CIRM, we’re funding a promising Phase 1 clinical trial sponsored by jCyte for a form of blindness called Retinis Pigmentosa. Based on preliminary results with a small cohort of patient, the treatment seems safe and may even be showing hints of effectiveness in some patients.

Ultimately, more is better. As the number of stem cell clinical trials for blindness grows, the sooner we can find out which therapies work best for which patients.

Using stem cells to fix bad behavior in the brain

 

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

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

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

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

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

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

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

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

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

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

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

Stem cell-derived pacemaker cells could help weak hearts keep the beat

In an average lifetime, the human heart dutifully beats more than 2.5 billion times. You can thank an area of the heart called the sinoatrial node, or SAN, which acts as the heart’s natural pacemaker. The SAN is made up of specialized heart muscle cells that, like a conductor leading an orchestra, dictates the rate which all other heart muscle cells will follow. But instead of a conductor’s baton, the cells of the SAN send out an electrical signal which stimulates the heart muscle cells to beat in unison.

Stem cell-derived pacemaker cells (blob in center) stimulate the layer of heart muscle cells  underneath to beat in unison (video: McEwen Centre for Regenerative Medicine).

Artificial pacemakers: an imperfect remedy for irregular heart beats
Certain inherited mutations as well as the aging process can foul up this natural pacemaker signal which usually results in slower, erratic heart rates and leads to poor blood circulation. The current remedy for irregular heart rhythm in these cases is the implantation of an artificial electronic pacemaker into the body. But these devices have their drawbacks: they can’t respond to hormone signals received by the heart, the implantation itself carries a risk of infection and the pacemaker’s battery life is limited to about 7 years so replacement surgeries are needed. Also, for children needing artificial pacemakers, there’s no effective way to adjust the device to adapt to a child’s growing heart.

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X-Ray of implanted electronic pacemaker (Image: Wikipedia)

Now, a Canadian research team at the McEwen Centre for Regenerative Medicine in Toronto aims to create a pacemaker from stem cells to one day provide a biological alternative to current electronic options. In their Nature Biotechnology report published last week, the team describes how they used their expertise in the developmental biology of the heart to successfully devise a method for transforming human embryonic stem cells into functioning pacemaker cells.

If you’ve been following the stem cell field for a while, you’ve probably watched lots of cool videos and read countless stories about beating heart cells grown from stem cells. Then what’s so special about this report? It’s true, you can readily make beating heart muscle cells, or cardiomyocytes, from embryonic stem cells. But usually these methods generate a mixture of various types of cardiomyocytes. The current report instead focused on specifically transforming the stem cells into the SAN pacemaker cells.

Look Ma, no genes inserted!
In 2015, another research team published work showing they had nudged stem cells to become cells with SAN-like pacemaker activity. But that study relied on the permanent insertion of a gene into the cells’ DNA which carries a risk of promoting tumor formation and would not be suitable for clinical use in the future. To generate cells that more closely correspond to the natural pacemaker found in healthy individuals, the researchers in this study created their cells by relying on a gene insertion-free recipe that included the addition of various hormones and growth factors. Stephanie Protze, the first author in the report, explained in a University Health Network press release, the challenge of finding the right ingredients:

“It’s tricky, you have to determine the right signaling molecules, at the right concentration, at the right time to stimulate the stem cells.”

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First author Dr. Stephanize Protze and senior author Gordon Keller, Director of the McEwen Centre
(Photo: McEwen Centre for Regenerative Medicine)

A replacement biological pacemaker: one step closer to reality
Analysis of their method showed that 90% of the human stem cell-derived SAN cells had the correct pacemaker activity. They went on to show that these cells could act as a natural pacemaker both in the petri dish and in rats. These results are an exciting step towards providing a natural pacemaker for people with irregular heartbeat disorders. Still, it’s important to realize that human clinical trials are at least 5 to 10 years down the road because a lot of preclinical animal studies will need to examine safety and effectiveness of such a therapy.

In the meantime, the team is eager to use their new method to grow patient specific pacemaker cells from human induced pluripotent stem cells. This approach will give the researchers a chance to study heart arrhythmia in a petri dish to better understand this health problem and to test drugs that could potentially improve symptoms.

Understanding two heart problems by studying the domino effect of one gene network

Although heart muscle cells, or cardiomyocytes, are specialized to help pump blood to the organs, they nonetheless carry all the genetic instructions for becoming a nerve cell, an intestinal cell, a liver or any cell type in the body. But at the moment in time that the fetal heart begins to develop, master switch proteins, called transcription factors, act like the first tile in an extremely complex pattern of dominos and set off a chain of events which lead to the activation of heart muscle specific genes in cardiomyocytes as well as the silencing of genes important for the development other cells types.

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cardiomyocytes

It’s truly amazing that this process comes together to create functioning hearts in the about 355,000 babies that are born in the world each day. But it isn’t always flawless as heart defects occur in about 1% of all live births. By studying a family with a history of heart defects, scientists at the Gladstone Institutes have gained a deeper understanding of how gene networks go awry,  causing heart defects as well as heart disease later in life. This CIRM-funded work was published today in Cell.

Half the children in the family studied by the Gladstone team were born with a hole in the wall between the two chambers of the heart. Back in 2003, the family approached Deepak Srivastava, head of the cardiovascular institute at Gladstone, for help. A genetic analysis by Srivastava’s team found that all of the affected children carried a mutation in the GATA4 gene, which encodes a heart specific transcription factor protein. Seven years later the children developed heart disease that led to weaker heart pumping. Although the two heart problems were not related, they suspected both were caused by the GATA4 mutation and sought to understand how that could be the case.

Srivastava’s team sought to understand how the GATA4 mutation could be causing both health problems. They collected skin samples from the affected children and generated cardiomyocytes using the induced pluripotent stem cell technique. Cells were also collected from the children’s healthy siblings. In the laboratory, the cells were analyzed for how well they functioned, such as their ability to contract. All of these tests showed that the cells carrying the GATA4 mutation had impaired function compared to the healthy cells. These findings provide a basis for the heart disease found in the children during their teens.

In terms of the heart wall defect, the team examined the GATA4 protein’s interaction with the protein TBX5, another transcription factor that is also mutated in cases of this defect. Both proteins regulate genes by directly binding to DNA as well as interacting with each other. In cells with the defective GATA4, the research discovered TBX5 did not bind well to the DNA. The lack of TBX5 led to a disruption in the activation of genes that play a role in the development of the heart wall.

TBX5 and GATA4 also work together in cardiomyocytes to silence genes that play a role in other cell types. But the scientists found that the because the GATA4 mutation hindered its interaction with TBX5, those non-heart specific genes we’re no longer repressed causing further disruption to proper cardiomyocyte development. Srivastava summed up these results in an institute press release:

srivastava-profile

Deepak Srivastava

“By studying the patients’ heart cells in a dish, we were able to figure out why their hearts were not pumping properly. Investigating their genetic mutation revealed a whole network of genes that went awry, first causing septal [heart wall] defects and then the heart muscle dysfunction.”

Now, because GATA4 and TBX5 are those first domino tiles in very intricate networks of genes, targeting those proteins for future therapy development wouldn’t be wise. Their effects are so widespread that blocking their actions would do more harm than good. But finding drugs that might affect only a branch of GATA4/TBX5 actions could result in new therapy approaches to heart defects and disease.

deepak-yen-sin-22 Deepak Srivastava and Yen-Sin Ang [Photo: Chris Goodfellow, Gladstone Institutes]

Yen-Sin Ang, the first author on the report, thinks these finding could prove fruitful for other diseases as well:

“It’s amazing that by studying genes in a two-dimensional cluster of heart cells, we were able to discover insights into a disease that affects a complicated three-dimensional organ. We think this conceptual framework could be used to study other diseases caused by mutations in proteins that serve as master regulators of whole gene networks.”

Stem cell stories that caught our eye: insights into stem cell biology through telomeres, reprogramming and lung disease

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.

Telomeres and stem cell stability: too much of a good thing

Just like those plastic tips at the end of shoelaces (fun fact: they’re called aglets), telomeres form a protective cap on the end of chromosomes. Because of the way DNA replication works, the telomeres shorten each time a cell divides. Trim away enough of the telomere over time and, like a frayed shoelace, the chromosomes become unstable and an easy target for damage which eventually leads to cell death.

telomere_caps

Telomeres (white dots) form a protective cap on chromsomes (gray). (Wikimedia) 

Stem cells are unique in that they contain an enzyme called telomerase that lengthens telomeres. Telomerase activity and telomere lengthening are critical for a stem cell’s ability to maintain virtually limitless cell divisions. So you’d assume the longer the telomere, the more stable the cell. But Salk Institute scientists reported this week that too much telomere can be just as bad, if not worse, than too little.

The CIRM-funded work, which was published in Nature Structural & Molecular Biology, used genetic engineering to artificially vary telomerase activity in human embryonic stem cells. Cells with low telomerase activity had shorter telomeres and died. This result wasn’t a surprise since the short telomeres-cell death observation has been well documented. Based on those results, the team was expecting cells with boosted telomerase activity and, in turn, extended telomeres would be especially stable. But that’s not what happened as senior author Jan Karlseder mentioned in a Salk press release:

“We were surprised to find that forcing cells to generate really long telomeres caused telomeric fragility, which can lead to initiation of cancer. These experiments question the generally accepted notion that artificially increasing telomeres could lengthen life or improve the health of an organism.”

The researchers also examined induced pluripotent stem (iPS) cells in the study and found that the cells contain “footprints” of telomere trimming. So the team is in a position to study how a cell’s telomere history relates to how well it can be reprogrammed into iPS cells. First author Teresa Rivera pointed out the big picture significance of this finding:

“Stem cell reprogramming is a major scientific breakthrough, but the methods are still being perfected. Understanding how telomere length is regulated is an important step toward realizing the promise of stem cell therapies and regenerative medicine.”

jan-karlseder_teresa-rivera-garcia0x8c7144w

Jan Karlseder and Teresa Rivera

Lego set of gene activators takes trial and error out of cellular reprogramming

To convert one cell type into another, stem cell researchers rely on educated guesses and a lot of trial and error. In fact, that’s how Shinya Yamanaka identified the four Yamanaka Factors which, when inserted into a skin cell, reprogram it into the embryonic stem cell-like state of an iPS cell. That ground-breaking discovery ten years ago has opened the way for researchers worldwide to specialize iPS cells into all sorts of cell types from nerve cells to liver cells. While some cell types are easy to generate this way, others are much more difficult.

Reporting this week in PNAS, a University of Wisconsin–Madison research team has developed a nifty systematic, high-throughput method for identifying the factors necessary to convert a cell from one type to another. Their strategy promises to free researchers from the costly and time consuming trial and error approach still in use today.

The centerpiece of their method is artificial transcription factors (ATFs). Now, natural transcription factors – Yamanaka’s Factors are examples – are proteins that bind DNA and activate or silence genes. Their impact on gene activity, in turn, can have a cascading effects on other genes and proteins ultimately causing, say a stem cell, to start making muscle proteins and turn into a muscle cell.

Transcription factors are very modular proteins – one part is responsible for binding DNA, another part for affecting gene activity and other parts that bind to other proteins. The ATFs generated in this study are like lego versions of natural transcription factors – each are constructed from combinations of different transcription factor parts. The team made nearly 3 million different ATFs.

As a proof of principle, the researchers tried reproducing Yamanaka’s original, groundbreaking iPS cell experiment. They inserted the ATFs into skin cells that already had 3 of the 4 Yamanaka factors, they left out Oct4. They successfully generated iPS with this approach and then went back and studied the makeup of the ATFs that had caused cells to reprogram into iPS cells. Senior author Aseem Ansari gave a great analogy in a university press release:

“Imagine you have millions of keys and only a unique key or combination of keys can turn a motor on. We test all those keys in parallel and when we see the motor fire up, we go back to see exactly which key switched it on.”

atf_ips_cells

Micrograph of induced pluripotent stem cells generated from artificial transcription factors. The cells express green fluorescent protein after a key gene known as Oct4 is activated. (ASUKA EGUCHI/UW-MADISON)

The analysis showed that these ATFs had stimulated gene activity cascades which didn’t directly involve Oct4 but yet ultimately activated it. This finding is important because it suggests that future cell conversion experiments could uncover some not so obvious cell fate pathways. Ansari explains this point further:

“It’s a way to induce cell fate conversions without having to know what genes might be important because we are able to test so many by using an unbiased library of molecules that can search nearly every corner of the genome.”

This sort of brute force method to accelerate research discoveries is music to our ears at CIRM because it ultimately could lead to therapies faster.

Search for clues to treat deadly lung disease

When researchers don’t understand what causes a particular disease, a typical strategy is to compare gene activity in diseased vs healthy cells and identify important differences. Those differences may lead to potential paths to developing a therapy. That’s the approach a collaborative team from Cincinnati Children’s Hospital and Cedars-Sinai Medical took to tackle idiopathic pulmonary fibrosis (IPF).

IPF is a chronic lung disease which causes scarring, or fibrosis, in the air sacs of the lung. This is the spot where oxygen is taken up by tiny blood vessels that surround the air sacs. With fibrosis, the air sacs stiffen and thicken and as a result less oxygen gets diffused into the blood and starves the body of oxygen.  IPF can lead to death within 2 to 5 years after diagnosis. Unfortunately, no cures exist and the cause is unknown, or idiopathic.

(Wikimedia)

(Wikimedia)

The transfer of oxygen from air sacs to blood vessels is an intricate one with many cell types involved. So pinpointing what goes wrong in IPF at a cellular and molecular level has proved difficult. In the current study, the scientists, for the first time, collected gene sequencing data from single cells from healthy and diseased lungs. This way, a precise cell by cell analysis of gene activity was possible.

One set of gene activity patterns found in healthy sample were connected to proper formation of a particular type of air sac cell called the aveolar type 2 lung cell. Other gene patterns were linked to abnormal IPF cell types. With this data in hand, the researchers can further investigate the role of these genes in IPF which may open up new therapy approaches to this deadly disease.

The study funded in part by CIRM was published this week in Journal of Clinical Investigation Insight and a press release about the study was picked up by PR Newswire.

Translating great stem cell ideas into effective therapies

alzheimers

CIRM funds research trying to solve the Alzheimer’s puzzle

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

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

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

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

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

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

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

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

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

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

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

Stem cell stories that caught our eye: glowing stem cells and new insights into Zika and SCID

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.

Glowing stem cells help scientists understand how cells work. (Karen Ring)
It’s easy to notice when something is going wrong. It’s a lot harder to notice when something is going right. The same thing can be said for biology. Scientists dedicate their careers to studying unhealthy cells, trying to understand why people get certain diseases and what’s going wrong at the cellular level to cause these problems. But there is a lot to be said for doing scientific research on healthy cells so that we can better understand what’s happening when cells start to malfunction.

A group from the Allen Institute for Cell Science is doing just this. They used a popular gene-editing technology called CRISPR/Cas9 to genetically modify human stem cell lines so that certain parts inside the cell will glow different colors when observed under a fluorescent microscope. Specifically, the scientists inserted the genetic code to produce fluorescent proteins in both the nucleus and the mitochondria of the stem cells. The final result is a tool that allows scientists to study how stem cells specialize into mature cells in various tissues and organs.

Glowing human stem cells. The edges of the cells are shown in purple while the DNA in the cell’s nucleus is in blue. (Allen Institute for Cell Science).

Glowing human stem cells. The edges of the cells are shown in purple while the DNA in the cell’s nucleus is in blue. (Allen Institute for Cell Science).

The director of stem cells and gene editing at the Allen Institute, Ruwanthi Gunawardane, explained how their technology improves upon previous methods for getting cells to glow in an interview with Forbes:

 “We’re trying to understand how the cell behaves, how it functions, but flooding it with some external protein can really mess it up. The CRISPR system allows us to go into the DNA—the blueprint—and insert a gene that allows the cell to express the protein in its normal environment. Then, through live imaging, we can watch the cell and understand how it works.”

The team has made five of these glowing stem cell lines available for use by the scientific community through the Coriell Institute for Medical Research (which also works closely with the CIRM iPSC Initiative). Each cell line is unique and has a different cellular structure that glows. You can learn more about these cell lines on the Coriell Allen Institute webpage and by watching this video:

 

Zika can take multiple routes to infect a child’s brain. (Kevin McCormack)
One of the biggest health stories of 2016 has been the rapid, indeed alarming, spread of the Zika virus. It went from an obscure virus to a global epidemic found in more than 70 countries.

The major concern about the virus is its ability to cause brain defects in the developing brain. Now researchers at Harvard have found that it can do this in more ways than previously believed.

Up till now, it was believed that Zika does its damage by grabbing onto a protein called AXL on the surface of brain cells called neural progenitor cells (NPCs). However, the study, published in the journal Cell Stem Cell, showed that even when AXL was blocked, Zika still managed to infiltrate the brain.

Using induced pluripotent stem cell technology, the researchers were able to create NPCs and then modify them so they had no AXL expression. That should, in theory, have been able to block the Zika virus. But when they exposed those cells to the virus they found they were infected just as much as ordinary brain cells exposed to the virus were.

Caption: Zika virus (light blue) spreads through a three-dimensional model of a developing brain. Image by Max Salick and Nathaniel Kirkpatrick/Novartis

Caption: Zika virus (light blue) spreads through a three-dimensional model of a developing brain. Image by Max Salick and Nathaniel Kirkpatrick/Novartis

In a story in the Harvard Gazette, Kevin Eggan, one of the lead researchers, said this shows scientists need to re-think their approach to countering the virus:

“Our finding really recalibrates this field of research because it tells us we still have to go and find out how Zika is getting into these cells.”

 

Treatment for a severe form of bubble baby disease appears on the horizon. (Todd Dubnicoff)
Without treatment, kids born with bubble baby disease typically die before reaching 12 months of age. Formally called severe combined immunodeficiency (SCID), this genetic blood disorder leaves infants without an effective immune system and unable to fight off even minor infections. A bone marrow stem cell transplant from a matched sibling can treat the disease but this is only available in less than 20 percent of cases and other types of donors carry severe risks.

In what is shaping up to be a life-changing medical breakthrough, a UCLA team has developed a stem cell/gene therapy treatment that corrects the SCID mutation. Over 40 patients have participated to date with a 100% survival rate and CIRM has just awarded the team $20 million to continue clinical trials.

There’s a catch though: other forms of SCID exist. The therapy described above treats SCID patients with a mutation in a gene responsible for producing a protein called ADA. But an inherited mutation in another gene called Artemis, leads to a more severe form of SCID. These Artemis-SCID infants have even less success with a standard bone marrow transplant compared to those with ADA-SCID. Artemis plays a role in DNA damage repair something that occurs during the chemo and radiation therapy sessions that are often necessary for blood marrow transplants. So Artemis-SCID patients are hyper-sensitive to the side of effects of standard treatments.

A recent study by UCSF scientists in Human Gene Therapy, funded in part by CIRM, brings a lot of hope to these Artemis-SCID patient. Using a similar stem cell/gene therapy method, this team collected blood stem cells from the bone marrow of mice with a form of Artemis-SCID. Then they added a good copy of the human Artemis gene to these cells. Transplanting the blood stem cells back to mice, restored their immune systems which paves the way for delivering this approach to clinic to also help the Artemis-SCID patients in desperate need of a treatment.