How you derive embryonic stem cells matters

A scientist named James Thompson was the first to successfully culture human embryonic stem cells in 1998. He didn’t know it then, but his technique isolated a specific type of embryonic stem cell (ESC) that had a “primed pluripotent state”.

There are actually two phases of pluripotency: naïve and primed. Naïve ESCs occur a step earlier in embryonic development (during the beginning of the blastocyst stage), and the naïve state can be thought of as the ground state of pluripotency. Primed ESCs on the other hand are more mature and while they can still become every cell type in the body, they are somewhat less flexible compared to naïve ESCs. If you want to learn more about naïve and primed ESCs, you can refer to this scientific review.

Scientists have developed methods to derive both naïve and primed human ESCs in culture and are attempting to use these cells for biomedical applications. However, a recent CIRM-funded study published in Cell Stem Cell, calls into question the quality of ESCs produced using these culturing methods and could change how lab-derived stem cells are used for stem cell transplant therapies and regenerative medicine.

Primed human embryonic stem cells (purple) identified by a green stem cell surface marker. (Image courtesy of UCLA)

Primed human embryonic stem cells (purple) identified by a green stem cell surface marker. (Image courtesy of UCLA)

Culturing methods erase stem cell memory

UCLA scientists discovered that some of the culturing methods used to propagate naïve ESCs actually erase important biochemical signatures that are essential for maintaining ESCs in a naïve state and for passing down genetic information from the embryo to the developing fetus.

When they studied naïve ESCs in culture, they focused on a naturally occurring process called DNA methylation. It controls which genes are active and which are silenced by adding chemical tags to certain stretches of DNA called promoters, which are responsible for turning genes on or off. This process is critical for normal development and keeping cells functional and healthy in adults.

UCLA scientists compared the DNA methylation state of the mature human blastocyst – the early-stage embryo and where naïve ESCs come from – to the methylation state of naïve ESCs generated in culture. They found that the methylation patterns in the blastocyst six days after fertilization were the same as the patterns found in the egg that it developed from. This discovery is contrary to previous beliefs that the DNA methylation patterns in eggs are lost a few hours after fertilization.

Amander Clark, the study’s lead author and UCLA professor explained in a UCLA news release:

Amander+Clark+headshot_68295d00-2717-4d5c-99f3-f791e6b6ebcf-prv

Amandar Clark, UCLA

“We know that the six days after fertilization is a very critical time in human development, with many changes happening within that period. It’s not clear yet why the blastocyst retains methylation during this time period or what purpose it serves, but this finding opens up new areas of investigation into how methylation patterns built in the egg affect embryo quality and the birth of healthy children.”

The group also discovered cultured naïve ESCs lack these important DNA methylation patterns seen in early-stage blastocysts. Current methods to derive naïve ESCs wipe their memory leaving them in an unstable state. This is an issue for researchers because some prefer the use of naïve ESCs over primed ESCs for their studies because naïve ESCs have more potential for experimentation.

“In the past three years, naïve stem cells have been touted as potentially superior to primed cells,” Clark said. “But our data show that the naïve method for creating stem cells results in cells that have problems, including the loss of methylation from important places in DNA. Therefore, until we have a way to create more stable naïve embryonic stem cells, the embryonic stem cells created for the purposes of regenerative medicine should be in a primed state in order to create the highest-quality cells for differentiation.”

How you derive embryonic stem cells matters

Now that this culturing problem has been identified, the UCLA group plans to develop new and improved methods for generating naïve ESCs in culture such that they retain their DNA methylation patterns and are more stable.

The hope from this research is that scientists will be able to produce stem cells that more closely resemble their counterparts in the developing human embryo and will be better suited for stem cell therapies and regenerative medicine applications.


Related Links:

A Tale of Two Stem Cell Treatments for Growing New Bones

Got Milk?

GotmilkIf you grew up during the 90’s, you most certainly will remember the famous “Got Milk?” advertising campaign to boost milk consumption. The plug was that milk was an invaluable source of calcium, a mineral that’s essential for growing strong bones. Drinking three glasses of the white stuff a day, supposedly would help deter osteoporosis, or the weakening and loss of bone with old age.

Research has proven that calcium is essential for growing and maintaining healthy bones. But milk isn’t the only source of calcium in the human diet, and a diet rich in calcium alone won’t prevent everyone from experiencing some amount of bone loss as they grow older. It also won’t help patients who suffer from bone skeletal defects grow new bone.

So whatever are we to do about bone loss and bone abnormalities? Here, we tell the “Tale of two stem cell treatments” where scientists tackle these problems using stem cell-derived therapies.

Protein Combo Boosts Bone Growth

Osteoporosis. (Image source)

Osteoporosis. (Image source)

Our first story comes from a CIRM-funded team of UCLA scientists. This team is interested in developing a better therapy to treat bone defects and osteoporosis. The current treatment for bone loss is an FDA-approved bone regenerating therapy involving the protein BMP-2 (bone morphogenetic protein-2). The problem with BMP-2 is that it can cause serious side effects when given in high doses. Two of the major ones are abnormal bone growth and also making stem cells turn into fat cells as well as bone cells.

The UCLA group attempted to improve the BMP-2 treatment by adding a second protein called NELL-1 (which they knew was good at stimulating bone growth from previous studies).  The combination of BMP-2 and NELL-1 resulted in bone growth and also prevented stem cells from making fat cells.

Upon further exploration, they found that NELL-1 acts as a signaling switch that controls whether a stem cell becomes a bone cell or a fat cell. Thus, with NELL-1 present, BMP-2 can only turn stem cells into bone cells.

Kang Ting, a lead author on the study, explained the significance of their new strategy to improve bone regeneration in a UCLA press release:

Kang Ting, UCLA

Kang Ting, UCLA

“Before this study, large bone defects in patients were difficult to treat with BMP2 or other existing products available to surgeons. The combination of NELL-1 and BMP2 resulted in improved safety and efficacy of bone regeneration in animal models — and may, one day, offer patients significantly better bone healing.”

Chia Soo, another lead author on the study, emphasized the importance of using NELL-1 in combination with BMP-2:

“In contrast to BMP2, the novel ability of NELL-1 to stimulate bone growth and repress the formation of fat may highlight new treatment approaches for osteoporosis and other therapies for bone loss.”

Stem cells that could fix deformed skulls

Our second story comes from a group at the University of Rochester. Their goal is to repair bones in the face and skull of patients suffering from congenital deformities, or damage due to injury or cancer surgery.

In a report published in Nature Communications, the scientists identified a population of skeletal stem cells that orchestrate the formation of the skull and can promote craniofacial bone repair in mice.

They identified this special population of skeletal stem cells by their expression of a protein called Axin2. Genetic mutations in the Axin2 gene can cause a birth defect called craniosynostosis. This condition causes the bone plates of a baby’s skull to fuse too early, causing skull deformities and impaired brain development.

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Axin2 stem cells shown in red and blue generated new bones cells after transplantation.

According to a news release from the University of Rochester, the group’s “latest evidence shows that stem cells central to skull formation are contained within Axin2 cell populations, comprising about 1 percent—and that the lab tests used to uncover the skeletal stem cells might also be useful to find bone diseases caused by stem cell abnormalities.”

Additionally, senior author on the study, Wei Hsu, “believes his findings contributee to an emerging field involving tissue engineering that uses stem cells and other materials to invent superior ways to replace damaged craniofacial bones in humans due to congenital disease, trauma, or cancer surgery.”

Two different studies, one common goal

Both studies have a common goal: to repair or regenerate bone to treat bone loss, damage, or deformities. I can’t help but wonder whether these different strategies could be combined in a way to that would bring more benefit to the patient than using either strategy alone.

Could we use BMP-2 and NELL-1 treatment along with Axin2 skeletal stem cells to treat craniosynostosis or repair damaged skulls? Or could we identify new stem cell populations in bone that would help patients suffering from osteoporosis?

I’m sure scientists will answer these questions sooner rather than later, and when they do, you’ll be sure to read about it on the Stem Cellar!


Related Links:

CREATE-ing tools that deliver genes past the blood-brain barrier

Your brain has a natural defense that protects it from infection and harm, it’s called the blood-brain barrier (BBB). The BBB is a selectively permeable layer of tightly packed cells that separates the blood in your circulatory system from your brain. Only certain nutrients, hormones, and molecules can pass through the BBB into the brain, while harmful chemicals and infection-causing bacteria are stopped at the border.

This ultimate defense barrier has its downsides though. It’s estimated that 98% of potential drugs that could treat brain diseases cannot pass through the BBB. Only some drug compounds that are very small in size or are fat-soluble can get through. Clearly, getting drugs and therapies past the BBB is a huge conundrum that remains to be solved.

Penetrating the Impenetrable

However, a CIRM-funded study published today in Nature Biotechnology has developed a delivery tool that can bypass the BBB and deliver genes into the brain. Scientists from Caltech and Stanford University used an innocuous virus called an adeno-associated virus (AAV) to transport genetic material through the BBB into brain cells.

Viral delivery is a common method to target and deliver genes or drugs to specific tissues or cells in the body. But with the brain and its impenetrable barrier, scientists are forced to surgically inject the virus into specific areas of the brain, which limits the areas of the brain that get treatment, not to mention the very invasive and potentially damaging nature of the surgery itself. For diseases that affect multiple areas in the brain, like Huntington’s and Alzheimer’s disease, direct injection methods are not likely to be effective. Thus, a virus that can slip past the BBB and reach all parts of the brain would be an idea tool for delivering drugs and therapies.

And that’s just what this new study accomplished. Scientists developed a method for generating modified AAVs that can be injected into the circulatory system of mice, pass through the BBB, and deliver genetic material into the brain.

They devised a viral selection assay called CREATE (which stands for Cre Recombinase-based AAV Targeted Evolution). Using CREATE, they tested millions of AAVs that all had slight differences in the genetic composition of their capsid, or the protein shell of the virus that protects the viruses’ genetic material. They tested these modified viruses in mice to see which ones were able to cross the BBB and deliver genes to support cells in the brain called astrocytes. For more details on how the science of CREATE works, you can read an eloquent summary in the Caltech press release.

A Virus that Makes Your Brain Glow Green

After optimizing their viral selection assay, the scientists were able to identify one AAV in particular, AAV-PHP.B, that was exceptionally good at getting past the BBB and targeting astrocytes in the mouse brain.

Lead author on the study, Ben Deverman, explained: “By figuring out a way to get genes across the blood-brain barrier, we are able to deliver them throughout the adult brain with high efficiency.”

They used AAV-PHP.B and AAV9 (which they knew could pass the BBB and infect brain cells) to transport a gene that codes for green fluorescent protein (GFP) into the mouse brain. After injecting mice with both viruses containing GFP, they saw that both viruses were able to make most of the cells in the brain glow green, confirming that they successfully delivered the GFP gene. When they compared the potency of AAV-PHP.B to the AAV9 virus, they saw that AAV-PHP.B was 40 times more efficient in delivering genes to the brain and spinal cord.

sing a new selection method, Caltech researchers have evolved the protein shell of a harmless virus, AAV9, so that it can more efficiently cross the blood brain barrier and deliver genes, such as the green fluorescent protein (GFP), to cells throughout the central nervous system. Here, GFP expression in naturally occurring AAV9 (left) can be seen distributed sparsely throughout the brain. The modified vector, AAV-PHP.B (right), provides more efficient GFP expression. Credit: Ben Deverman and the Gradinaru laboratory/Caltech - See more at: http://www.caltech.edu/news/delivering-genes-across-blood-brain-barrier-49679#sthash.BDu7OfC8.dpuf

Newly “CREATEd” AAV-PHP.B (right) is better at delivering the GFP gene to the brain than AAV9 (left). Credit: Ben Deverman.

“What provides most of AAV-PHP.B’s benefit is its increased ability to get through the vasculature into the brain,” said Ben Deverman. “Once there, many AAVs, including AAV9 are quite good at delivering genes to neurons and glia.”

Senior author on the study, Viviana Gradinaru at Caltech, elaborated: “We could see that AAV-PHP.B was expressed throughout the adult central nervous system with high efficiency in most cell types.”

Not only that, but using a neat technique called PARS CLARITY that Gradinaru developed in her lab, which makes tissues and organs transparent, the scientists were able to see the full reach of the AAV-PHP.B virus. They saw green cells in other organs and in the peripheral nerves, thus showing that AAV-PHP.B works in other parts of the body, not just the brain.

But just because AAV-PHP.B is effective in mice doesn’t mean it works well in humans. To address this question, the authors tested AAV-PHP.B in human neurons and astrocytes derived from human induced pluripotent stem cells (iPS cells). Sergiu Pasca, a collaborator from Stanford and author on the study, told the Stem Cellar:

Sergiu Pasca

Sergiu Pasca

“We have also tested the new AAV variant (AAV-PHP.B) in a human 3D cerebral cortex model developed from human iPS cells and have shown that it transduces human neurons and astrocytes more efficiently than does AAV9 demonstrating the potential for biomedical applications.”

An easier way to deliver genes across the BBB

This study provides a new way to cross the BBB and deliver genes and potential therapies that could treat a laundry list of degenerative brain diseases.

This is only the beginning for this new technology. According to the Caltech press release, the study’s authors have future plans for the AAV-PHP.B virus:

“The researchers hope to begin testing AAV-PHP.B’s ability to deliver potentially therapeutic genes in disease models. They are also working to further evolve the virus to make even better performing variants and to produce variants that target certain cell types with more specificity.”


Related Links:

Super stem cell exhibit opens in San Diego

Stem cell exhibit

The best science museums are like playgrounds. They allow you to wander around, reading, watching and learning and being amazed as you go. It’s not just a feast for the mind; it’s also fun for the hands.  You get to interact with and experience science, pushing buttons, pulling levers, watching balls drop and electricity spark.

The best science museums bring out the kid in all of us.

This Saturday a really great science museum is going to be host to a really great exhibition. The Reuben H. Fleet Science Center in San Diego is the first stop on a California tour for “Super Cells: The Power of Stem Cells”. The exhibit is coming here fresh from a successful tour of Canada and the UK.

The exhibit is a “hands-on” educational display that demonstrates the importance and the power of stem cells, calling them “our body’s master cells.” It uses animations, touch-screen displays, videos and stunning images to engage the eyes and delight the brain.

stem cell exhibit 2Each of the four sections focuses on a different aspect of stem cell research, from basic explanations about what a stem cell is, to how they change and become all the different cells in our body. It has a mini laboratory so visitors can see how research is done; it even has a “treatment” game where you get to implant and grow cells in the eye, to see if you can restore sight to someone who is blind.

 

In a news release the Fleet Science Center celebrated the role that stem cells play in our lives:

“Stem cells are important because each of us is the result of only a handful of tiny stem cells that multiply to produce the 200 different types of specialized cells that exist in our body. Our stem cells continue to be active our whole lives to keep us healthy. Without them we couldn’t survive for more than three hours!”

It is, in short, really fun and really cool.

Of course we might be a tad biased here as we helped produce and develop the exhibit in collaboration with the Sherbrooke Museum of Science and Nature in Canada, the Canadian Stem Cell Network, the Centre for Commercialization of Regenerative Medicine in Canada; the Cell Therapy Catapult in the UK, and EuroStemCell.

stem cell exhibit 3

The exhibit is tri-lingual (English, Spanish and French) because our goal was to create a multi-lingual global public education program. San Diego was an obvious choice for the first stop on the California tour (with LA and the Bay Area to follow) because it is one of the leading stem cell research hubs in the U.S., and a region where CIRM has invested almost $380 million over the last ten years.

As our CIRM Board Chair, Jonathan Thomas, said:

“One of our goals at CIRM is to help spread awareness for the importance of stem cell research. San Diego is an epicenter of stem cell science and having this exhibition displayed at the Reuben H. Fleet Science Center is a wonderful opportunity to engage curious science learners of all ages.”

The Super Cells exhibit runs from January 23 to May 1, 2016, in the Main Gallery of the Reuben H. Fleet Science Center. The exhibition is included with the cost of Fleet admission.

For more information, visit the Reuben H. Fleet Science Center website.

Training the Next Generation of Stem Cell Scientists

Nobel prize winners don’t come out of thin air, they were all young, impressionable kids at one point in time.  If you ask any award-winning scientists how they got into science research, many of them would likely tell you about an inspiring teacher, an encouraging parent, or a hands-on research opportunity that inspired or helped them to pursue a scientific career.

Not every student is lucky enough to have one of these experiences, and many students, especially those from low income families, might never be exposed to good science or have the opportunity to pursue a career as a scientist.

CIRM is changing this for students in California by committing a significant portion of its funds to educating and training future stem cells scientists.

Yesterday, the Board approved over $42 million to fund two of CIRM’s educational programs, the Bridges to Stem Cell Research and Therapy Awards (Bridges) and the Summer Program to Accelerate Regenerative Medicine Knowledge (SPARK).

Bridging the Stem Cell Gap

The Bridges program supports undergraduate and master’s level students by providing paid research internships at California universities or colleges that don’t have a major stem cell research program. This program has evolved over the past seven years since it began, and now includes training and education courses in stem cell research, and direct patient engagement and outreach activities within California’s diverse communities.

CIRM’s president, Randy Mills explained in a press release:

Randy Mills, Stem Cell Agency President & CEO

Randy Mills, CIRM President & CEO

“The goal of the Bridges program is to prepare undergraduate and Master’s level students in California for a successful career in stem cell research. That’s not just a matter of giving them money, but also of giving them good mentors who can help train and guide them, of giving them meaningful engagement with patients and patient advocates, so they have a clear vision of the impact the work they are doing can have on people’s lives.”

Chairman of the CIRM Board, Jonathan Thomas, added:

Jonathan Thomas

Jonathan Thomas, Chairman of the CIRM Board

“The Bridges program has been incredibly effective in giving young people, often from disadvantaged backgrounds, a shot at a career in science. Of the 700 students who have completed the program, 95 percent are either working in a lab, enrolled in school or applying to graduate school. Without the Bridges program this kind of career might have been out of reach for many of these students.”

The CIRM Board voted to approve $40.13 million for the Bridges program, which will fund 14 programs at California state universities and city colleges. Each program will be able to support ten students for five years.

SPARKing Interest in Stem Cells

The SPARK program supports summer research internships for high school students that represent the diversity of the state’s population. It evolved from an earlier educational program called Creativity, and now emphasizes community outreach, direct patient engagement activities, and social media training along with training in stem cell research techniques.

“SPARK is all about helping cultivate high school students who are interested in science, and showing them it’s possible to have a career doing something they love,” said Randy Mills.

The Board approved $2.31 million for the SPARK program, which will provide California institutions funding support for five to ten students each year. Seven programs received funding including the Children’s Hospital Oakland Research Institute, UC San Francisco, UC Davis, Cedars-Sinai, City of Hope, USC and Stanford.

2015 Creativity Program students (now called SPARK).

2015 Creativity Program students (now called SPARK).

Training the Next Generation

For years, national leaders, including President Obama, have warned that without skilled, experienced researchers, the U.S. is in danger of losing its global competitiveness in science. But cuts in federal funding for research mean this is a particularly challenging time to begin a scientific career.

Our goal with the Bridges and SPARK programs is to address both these issues and support young scientists as they get the experience they need to launch their careers.


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Smoking out Leukemia Cells to Prevent Cancer Relapse

Ninety-five percent of all patients with chronic myeloid leukemia (CML), carry a Frankenstein-like gene, called BCR-ABL, created from an abnormal fusion of two genes normally found on two separate chromosomes. Like a water faucet without a shutoff valve, the resulting mutant protein is stuck in an “on” position and leads to uncontrolled cell division and eventually to CML as well as other blood cancers.

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An oversized bone marrow cell, typical of chronic myeloid leukemia. Credit:  Difu Wu

Gleevec, a revolutionary, targeted cancer drug that specifically blocks the BCR-ABL protein was approved by the FDA in 2001 and doubled 5-year survival rates for CML patients (31 to 59%) over that decade. Still, some patients who are responsive to the Gleevec class of drugs, become resistant to the treatment and suffer a relapse. Up until now, research studies pointed to an accumulation of additional DNA mutations as the driving force behind a rebound of the cancer cells.

But on Monday, a CIRM-funded UC San Diego team reported in PNAS that a reduction in just one protein, called MBNL3, in CML cancer cells activates a cascade of genes normally responsible for the unlimited self-renewing capacity of embryonic stem cells. Much like a researcher can reprogram a skin cell back into an embryonic like state via the induced pluripotent stem cell (iPSC) technique, this finding suggests that CML enhances its ability to spread by exploiting the same cellular reprogramming machinery.

CML is a slowly progressing cancer that initially begins with a chronic phase. At this stage, the cancerous cells, called blast cells, make up less than five percent of cells in the bone marrow. The phase usually lasts several years and is well controlled by drug treatment. A blast crisis phase follows when the blast cells make up 20 to 30% of the blood or bone marrow. At this stage, the patient’s condition deteriorates as symptoms like anemia and frequent infections worsen.

The UCSD team, led by Catriona Jamieson, director of Stem Cell Research at Moores Cancer Center, did a comparative analysis of CML patient samples and found that a reduction of MBNL3, a RNA binding protein, corresponded with CML progression from the chronic to blast phase. If you took intro biology in high school or college, you may recall that RNA acts as a messenger molecule critical to the translation of DNA’s genetic code into proteins. Some splicing and trimming of the RNA molecule occurs to prep it for this translation process. It turns out the decrease in MBNL3 in blast phase cells frees up stretches of RNA that leads to alternate splicing and, in turn, alternate forms of a given protein.

The study showed that in response to the decrease of MBNL3, an alternate form of the protein CD44, aptly named CD44 variant 3 (CD44v3), is increased in CML blast phase cells compared with chronic phase cells. Artificially over producing CD44v3 increased the activity of SOX2 and OCT4, two genes that are critical for maintaining the properties of embryonic stem cells. Genes involved with homing blood cells to the bone marrow were also upregulated.

Put together, these data suggest that this alternate RNA splicing not only helps CML blast phase cells preserve stem cell-like qualities, but it also helps sequester them in the bone marrow. Other studies have shown that the BCR-ABL protein inhibitor drugs are not effective in eradicating blast phase cells in the bone marrow, perhaps the reason behind relapse in some CML patients.

To try to smoke out these hiding blast phase cells in mouse CML studies, the team tested a combination treatment of a CD44 inhibitor along with the BCR-ABL inhibitor. While either treatment alone effectively removed the CML blast phase cells from the spleen and blood, only the combination significantly reduced survival of the cells in the bone marrow.

This tantalizing result has motivated the Jamieson team to pursue the clinical development of a CD44 blocking antibody with combination with the existing BCR-ABL inhibitors. As reported by Bradley Fikes in a San Diego Union Tribune story, the CD44 blocking antibody was not stable so more work is still needed to generate a new antibody.

But the goal remains the same as Jamieson mentions in a UCSD press release:

“If we target embryonic versions of proteins that are re-expressed by cancer, like CD44 variant 3, with specific antibodies together with tyrosine kinase [for example, BCR-ABL] inhibitors, we may be able to circumvent cancer relapse – a leading cause of cancer-related mortality.”

 

 

 

 

 

Eyeing Stem Cell Therapies for Vision Loss

Back by popular demand (well, at least a handful of you demanded it!) we’re pleased to present the third installment of our Stem Cells in Your Face video series. Episodes one and two set out to explain – in a light-hearted, engaging and clear way – the latest progress in CIRM-funded stem cell research related to Lou Gehrig’s disease (Amyotrophic Lateral Sclerosis, or ALS) and sickle cell disease.

With episode three, Eyeing Stem Cell Therapies for Vision Loss, we turn our focus (pun intended) to two CIRM-funded clinical trials that are testing stem cell-based therapies for two diseases that cause severe visual impairment, retinitis pigmentosa (RP) and age-related macular degeneration (AMD).

Two Clinical Trials in Five Minutes
Explaining both the RP and AMD trials in a five-minute video was challenging. But we had an ace up our sleeve in the form of descriptive eye anatomy animations graciously produced and donated by Ben Paylor and his award-winning team at InfoShots. Inserting these motion graphics in with our scientist and patient interviews, along with the fabulous on-camera narration by my colleague Kevin McCormack, helped us cover a lot of ground in a short time. For more details about CIRM’s vision loss clinical trial portfolio, visit this blog tomorrow for an essay by my colleague Don Gibbons.

Vision Loss: A Well-Suited Target for Stem Cell Therapies
Of the wide range of unmet medical needs that CIRM is tackling, the development of stem cell-based treatments for vision loss is one of the furthest along. There are a few good reasons for that.

The eye is considered to be immune privileged, meaning the immune system is less accessible to this organ. As a result, there is less concern about immune rejection when transplanting stem cell-based therapies that did not originally come from the patient’s own cells.

The many established, non-invasive tools that can peer directly into the eye also make it an attractive target for stem cell–based treatment. Being able to continuously monitor the structure and function of the eye post-treatment will be critical for confirming the safety and effectiveness of these pioneering therapies.

Rest assured that we’ll be following these trials carefully. We eagerly await the opportunity to write future blogs and videos about encouraging results that could help the estimated seven million people in the U.S. suffering from disabling vision loss.

Related Links:

Stem Cellar archive: retinitis pigmentosa
Stem Cellar archive: macular degeneration
Video: Spotlight on Retinitis Pigmentosa
Video: Progress and Promise in Macular Degeneration
CIRM Fact Sheet on Vision Loss

Have your cake and eat it too: Stem cells without the risk of tumors

journal.pmed.1000029.g001

An unregulated stem cell treatment in 2001 led to tumor growth in the (A) brain stem and (B) spinal cord of the patient four years later. (Fig 1. PLoS Med. 2009 Feb 17;6(2):e1000029)

A real stem cell tourism story
Back in 2001, an Israeli boy suffering from Ataxia Telangiectasia, a genetic brain disease that affects movement, traveled to Russia for an unregulated stem cell treatment. His brain and spinal cord were injected with fetal stem cells though the exact composition of those cells was not known. Four years later, the boy complained of headaches and his doctors back home found tumors in his brain and spinal cord.

 Stem cells: a double-edged sword
As the BBC  and many other news outlets reported in 2009, a Plos Medicine report eventually confirmed the tumor cells originated from the donor stem cells. And here lies a double-edged sword of stem cell-based therapies. On one side, stem cells hold great promise to repair diseased or damaged tissue because they can morph, or differentiate, into a wide range of cell types.

 But on the other side, they have the capacity to remain unspecialized and continually self-renew.This is great for producing enough cells to treat many people. Researchers try to make sure only more mature cells are transplanted, but if any of these propagating, undifferentiated cells get carried along with a stem cell-based treatment, there’s a risk of introducing uncontrolled cell growth and cancers instead of remedies. Human pluripotent stem cells (hPSCs), which can form almost any cell type found in our body, are believed to be especially susceptible to this dangerous potential side effect.

Reporting this week in the journal, eLife, CIRM-funded researchers at UCSD found a way to dodge the risk of tumor growth by identifying a unique, alternate stem cell type that could be applied to kidney disease. To find this cell type, the research team focused on cells that were a bit further along a differentiation path compared to unspecialized hPSCs.

Repeat after me: endoderm, ectoderm, mesoderm

In the earliest stages of embryo development, three germ layers form. (image: Internet Science Room)

In the earliest stages of embryo development, three germ layers form. (image: Internet Science Room)

To explain, let’s take a brief detour into developmental biology. In the very early stages of specialization, the cells of the embryo form the three germ layers: ectoderm, endoderm and mesoderm. Each layer gives rise to specific set of cells and tissues. Endoderm forms, to just name a few, the lungs, intestines and pancreas; ectoderm develops into skin, the brain and spinal cord; mesoderm forms blood, muscle, bone and kidneys. Within each germ layer lie progenitor stem cells, that maintain the capacity to self-renew and can also differentiate into the adult cells formed by that germ layer.

Finding a mesoderm progenitor
While methods for growing ectoderm and endoderm progenitor stem cells from hPSCs had been previously developed, few, if any, labs had done the same for mesoderm. So the UCSD team systematically tested thousands of combinations of nutrients and chemicals for both growing and differentiating hPSCs into mesoderm. Using this approach, they successfully tracked down a recipe that gave rise to mesoderm progenitor cells with the potential to multiply and grow in population yet lacking the ability to form tumors when transplanted into mice.

Color tagged surface proteins indicate a kidney fate for activated mesodermal progenitors (Fig 7c Kumar et al. eLife 2015;4:e08413)

Color tagged surface proteins indicate a kidney fate for activated mesodermal progenitors (Fig 7c Kumar et al. eLife 2015;4:e08413)

The research team planned to work out the various conditions to specialize the progenitor cells into a wide range of mesoderm tissues. But to their surprise, when triggered to differentiate, the progenitors only gave rise to cells of the kidney. This very limited specialization is actually desired for clinical applications since purity of cell therapies is a requirement for testing in humans.

Our kidneys thank you
Putting it all together, the team has identified a cell source with unlimited self renewal capacity that can differentiate into a very specific cell type and doesn’t carry a risk of tumor formation when transplanted. These qualities make the mesoderm progenitor cell an exciting tool for developing future kidney repair or replacement treatments. And as Dr. Karl Willert, senior author and associate professor at UC San Diego, states in a UCSD press release, there is also reason to be excited about near-term applications:

“Our cells can serve as building blocks to generate kidneys that may one day be suitable for cell replacement and transplantation. I think such a therapeutic application is still a few years in the future, but engineered kidney tissue can serve as a powerful model system to study how the human kidney interacts with and filters drugs. Such an application would be of tremendous value to the pharmaceutical industry.”

New Video: Spinal Cord Injury and a CIRM-Funded Stem Cell-Based Trial

Just 31 years old, Richard Lajara thought he was going to die.

Picture1

Richard Lajara, the 4th participant in Geron’s stem cell-based clinical trial for spinal cord injury.

On September 9, 2011 he slipped on some rocks at a popular swimming hole and was swept down a waterfall headfirst into a shallow, rocky pool of water. Though he survived, the fall left him paralyzed from the waist down due to a severed spinal cord.

Patient Number Four
At that same time period, Geron Inc. had launched a clinical trial CIRM helped fund testing the safety of a stem cell-based therapy for spinal cord injury (SCI). It was the world’s first trial using cells derived from human embryonic stem cells and Lajara was an eligible candidate. Speaking to CIRM’s governing Board this past summer for a Spotlight on Disease seminar, he recalled his decision to participate:

“When I participated with the Geron study, I was honored to be a part of it. It was groundbreaking and the decision was pretty easy. I understood that it was very early on and I wasn’t looking for any improvement but laying the foundation [for future trials].”

A few months after his treatment, Geron discontinued the trial for business reasons. Lajara was devastated and felt let down. But this year the therapy got back on track with the announcement in June by Asterias Biotherapeutics that they had treated their first spinal cord injury patient after having purchased the stem cell assets of Geron.

Getting Hope Back on Track
Dr. Jane Lebkowski, Asterias’ President of R&D and Chief Scientific Officer, also spoke at the Spotlight on Disease seminar to provide an overview and update on the company’s clinical trial. A video recording of Lebkowski’s and Lajara’s presentations is now available on our web site and posted here:

As Dr. Lebkowski explains in the video, Asterias didn’t have to start from scratch. The Geron study data showed the therapy was well tolerated and didn’t cause any severe safety issues. In that trial, five people (including Richard Lajara) with injuries in their back received an injection of two million stem cell-derived oligodendrocyte progenitor cells into the site of spinal cord damage. The two million-cell dose was not expected to show any effect but was focused on ensuring the therapy was safe.

Oligodendrocyte Precursors: Spinal Cord Healers
As the former Chief Scientific Officer at Geron, Lebkowski spoke first hand about why the oligodendrocyte precursor was the cell of choice for the clinical trial. Previous animal studies showed that oligodendrocyte progenitors, a cell type normally found in the spinal cord, have several properties that make them ideal cells for treating SCI: first, they help stimulate the growth of damaged neurons, the cell type responsible for transmitting electrical signals from the brain to the limbs.

Second, the oligodendrocytes produce myelin, a protein that acts as an insulator of neurons, very much like the plastic covering on a wire. In many spinal cord injuries, the nerves are still intact but lose their myelin insulation and their ability to send signals. Third, the oligodendrocytes release other proteins that help reduce the size of cysts that often form at the injury site and damage neurons. In preclinical experiments, these properties of oligodendrocyte progenitors improved limb movement in spinal cord-severed rodents.

Together, the preclinical animal studies and the safety data from the Geron clinical trial helped Asterias win approval from the Food and Drug Administration (FDA) to start their current trial, also funded by CIRM, this time treating patients with neck injuries instead of back injuries.

The Asterias trial is a dose escalation study with the first group of three patients again receiving two million cells. The trial was designed such that if this dose shows a good safety profile in the neck, as it did in the Geron trial in the back, then the next cohort of five patients will receive 10 million cells. In fact, Asterias reported in August that the lower dose was not only safe but also showed some encouraging results in one of the patients. And just two days ago Asterias announced their data monitoring committee recommended to begin enrolling patients for the 10 million cell dose.  If all continues to go well with safety, the dose will be escalated to 20 million cells in the third cohort of five patients. While two million cells was a very low safety dose, Asterias anticipates seeing some benefit from the 10 and 20 million cell doses.

Changing Lives by Increasing Independence
Does Lebkowski’s team expect the patients to stand up out of their wheelchairs post-treatment? No, but they do hope to see a level of improvement that could dramatically increase quality of life and decrease the level of care needed. Specifically, they are looking to see a so-called “two motor level improvement.” In her talk Lebkowski explained this quantitative measure with the chart below:

“If a patient is a C4 [meaning their abilities are consistent with someone with a spinal cord injury at the fourth cervical, or neck, bone] they will need anywhere from 18 to 24 hours of attendant care for daily living. If we could improve their motor activity such that they become a C6, that is just two motor levels, what you can see is independence tremendously increases and we go from 18 to 24 hour attendant care to having attendant care for about four hours of housework.”

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Small improvements in movement abilities can be life changing for people with spinal cord injuries.

It’s so exciting the field is at a point in time that scientists like Dr. Lebkowski are discussing real stem cell-based clinical trials that are underway in real patients who could achieve real improvements in their lives that otherwise would not be possible.

And we have people like Richard Lajara to thank. I think Dr. Oswald Stewart, the Board’s spinal cord injury patient advocate, summed it up well when speaking to Lajara at the meeting:

“Science and discovery and translation [into therapies] doesn’t happen without people like you who are willing to put yourselves on the line to move things forward. Thank you for being in that first round of people testing this new therapy.”

Don Reed Reflects on the California Stem Cell Initiative

StemCellBattlesCoverYesterday was stem cell awareness day. In honor of this important event, Don Reed held a book reading at CIRM for his newly released book, STEM CELL BATTLES: Proposition 71 and Beyond: How Ordinary People Can Fight Back Against the Crushing Burden of Chronic Disease.

Don has worn many hats during his life. He’s been a power lifter, a diver at Sea World, and is one of California’s most tenacious stem cell research advocates. His stem cell journey began when his son, Roman Reed, was seriously injured in a football accident, leaving him mostly paralyzed from the neck down.

Both Don and Roman didn’t let this tragic event ruin their lives or steal their hope. In fact, both Don and his son were instrumental for getting proposition 71 to pass, leading to the birth of CIRM and new hope for patients with uncured diseases.

At yesterday’s book reading, Don chronicled the early battles to get human stem cell research off the ground in California, the progress that’s been made so far and the promise for future therapies. It was truly an inspiring event, bringing together patients, friends of Don and his wife Gloria, and CIRM scientists to celebrate the stem cell research accomplishments of the past ten years.

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Enjoy more pictures of the event below and a short video of Jonathan Thomas, Chair of the Governing Board of CIRM, who said a few words in praise of Don Reed’s efforts to fight for stem cell research in California.

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Don Reed and his wife Gloria share a smile with CIRM’s Pat Olson.

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Jonathan Thomas and Don Reed.


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