Fish umbrellas and human bone: protecting blood stem cells from the sun’s UV rays

Blood stem cells.jpg

Most people probably do not question the fact that human blood stem cells – those that give rise to all the cells in our blood – live inside the marrow of our bones, called a stem cell “niche”. But it is pretty odd when you stop to think about it. I mean, it makes sense that the hard, calcium-rich structure of bones provide our bodies with a skeleton but why is it also responsible for making our blood?

This week, researchers at Harvard report in Nature that the answer may come down to protecting these precious cells from the DNA-damaging effects of UV radiation from the sun. They arrived at those insights by examining zebrafish which harbor blood stem cells, not in their bones, but in their kidneys. Fredrich Kapp, MD, the first author of the report, was trying to analyze blood stem cells in zebrafish under the microscope but noticed a layer of other cells on top of the kidney was obscuring his view.

fishumbrella

In a zebrafish larva (illustration above), a dark umbrella formed by pigmented cells (white arrows point to these black spots in box, left) in the kidney protects vulnerable stem cells from damaging UV light. Right image is a closeup of the box. Scale bars equal 100 micrometers (left) and 50 micrometers (right). Credit: F. Kapp et al./Nature 2018
Read more at: https://phys.org/news/2018-06-blood-cells-bones.html#jCp

That layer of cells turned out to be melanocytes which produce melanin a pigment that gives our skin color. Melanin also protects our skin cells from the sun’s UV radiation which damages our DNA and can cause genetic mutations. In a press release, Kapp recalled his moment of insight:

“The shape of the melanocytes above the kidney reminded me of a parasol, so I thought, do they provide UV protection to blood stem cells?”

To answer his question, he and his colleagues compared the effects of UV radiation on normal zebrafish versus mutant zebrafish lacking the layer of melanocytes. Confirming Kapp’s hypothesis, the fish missing the melanocyte layer had fewer blood stem cells. Simply turning the normal fish upside down and exposing them to the UV rays also depleted the blood stem cells.

And here’s where the story gets really cool. In studying frogs – animals closer to us on the evolutionary tree – they found that as the tadpole begins to grow legs, their blood stem cells migrate from the melanocyte-covered kidney cells to inside the bone marrow, an even better form of UV protection. Senior author Leonard Zon explained the importance of this finding:

“We now have evidence that sunlight is an evolutionary driver of the blood stem cell niche. As a hematologist and oncologist, I treat patients with blood diseases and cancers. Once we understand the niche better, we can make blood stem cell transplants much safer.”

 

 

How mice and zebrafish are unlocking clues to repairing damaged hearts

Bee-Gees

The Bee Gees, pioneers in trying to find ways to mend a broken heart. Photograph: Michael Ochs Archives

This may be the first time that the Australian pop group the Bee Gees have ever been featured in a blog about stem cell research, but in this case I think it’s appropriate. One of the Bee Gees biggest hits was “How can you mend a broken heart” and while it was a fine song, Barry and Robin Gibb (who wrote the song) never really came up with a viable answer.

Happily some researchers at the University of Southern California may succeed where Barry and Robin failed. In a study, published in the journal Nature Genetics, the USC team identify a gene that may help regenerate damaged heart tissue after a heart attack.

When babies are born they have a lot of a heart muscle cell called a mononuclear diploid cardiomyocyte or MNDCM for short. This cell type has powerful regenerative properties and so is able to rebuild heart muscle. However, as we get older we have less and less MNDCMs. By the time most of us are at an age where we are most likely to have a heart attack we are also most likely to have very few of these cells, and so have a limited ability to repair the damage.

Michaela Patterson, and her colleagues at USC, set out to find ways to change that. They found that in some adult mice less than 2 percent of their heart cells were MNDCMs, while other mice had a much higher percentage, around 10 percent. Not surprisingly the mice with the higher percentage of MNDCMs were better able to regenerate heart muscle after a heart attack or other injury.

So the USC team – with a little help from CIRM funding – dug a little deeper and did a genome-wide association study of these mice, that’s where they look at all the genetic variants in different individuals to see if they can spot common traits. They found one gene, Tnni3k, that seems to play a key role in generating MNDCMs.

Turning Tnni3K off in mice resulted in higher numbers of MNDCMs, increasing their ability to regenerate heart muscle. But when they activated Tnni3k in zebrafish it reduced the number of MNDCMs and impaired the fish’s ability to repair heart damage.

While it’s a long way from identifying something interesting in mice and zebrafish to seeing if it can be used to help people, Henry Sucov, the senior author on the study, says these findings represent an important first step in that direction:

“The activity of this gene, Tnni3k, can be modulated by small molecules, which could be developed into prescription drugs in the future. These small molecules could change the composition of the heart over time to contain more of these regenerative cells. This could improve the potential for regeneration in adult hearts, as a preventative strategy for those who may be at risk for heart failure.”

 

 

 

Stem cell stories that caught our eye: better ovarian cancer drugs, creating inner ear tissue, small fish big splash

Two drugs are better than one for ovarian cancer (Karen Ring). Earlier this week, scientists from UCLA reported that a combination drug therapy could be an effective treatment for 50% of aggressive ovarian cancers. The study was published in the journal Precision Oncology and was led by Dr. Sanaz Memarzadeh.

Women with high-grade ovarian tumors have an 85% chance of tumor recurrence after treatment with a common chemotherapy drug called carboplatin. The UCLA team found in a previous study that ovarian cancer stem cells are to blame because they are resistant to carboplatin. It’s because these stem cells have an abundance of proteins called cIAPs, which prevent cell death from chemotherapy.

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Ovarian cancer cells (blue) expressing cIAP protein (red) on the left are more sensitive to a combination therapy than cancer cells that don’t express the protein on the right. (UCLA Broad Stem Cell Research Center/Precision Oncology)

Memarzadeh discovered that an experimental drug called birinapant made some ovarian cancer tumors more sensitive to chemotherapy treatment by breaking down cIAPs. This gave her the idea that combining the two drugs, birinapant and carboplatin, might be a more effective strategy for treating aggressive ovarian tumors.

By treating with the two drugs simultaneously, the scientists improved the survival rate of mice with ovarian cancer. They also tested this combo drug treatment on 23 ovarian cancer cell lines derived from women with highly aggressive tumors. The treatment killed off half of the cell lines indicating that some forms of this cancer are resistant to the combination treatment.

When they measured the levels of cIAPs in the human ovarian cancer cell lines, they found that high levels of the proteins were associated with ovarian tumor cells that responded well to the combination treatment. This is exciting because it means that clinicians can analyze tumor biopsies for cIAP levels to determine whether certain ovarian tumors would respond well to combination therapy.

Memarzadeh shared her plans for future research in a UCLA news release,

“I believe that our research potentially points to a new treatment option. In the near future, I hope to initiate a phase 1/2 clinical trial for women with ovarian cancer tumors predicted to benefit from this combination therapy.”

In a first, researchers create inner ear tissue. From heart muscle to brain cells to insulin-producing cells, researchers have figured out how to make a long list of different human cell types using induced pluripotent stem cells (iPSCs) – cells taken from the body and reprogrammed into a stem cell-like state.

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Human inner ear organoid with sensory hair cells (cyan) and sensory neurons (yellow). An antibody for the protein CTBP2 reveals cell nuclei as well as synapses between hair cells and neurons (magenta). | Photo: Karl Koehler

This week, a research group at the Indiana University School of Medicine successfully added inner ear cells to that list. This feat, published in Nature Biotechnology, is especially important given the fact that the inner ear is one of the few parts of the body that cannot be biopsied for further examination. With these cells in hands, new insights into the causes of hearing loss and balance disorders may be on the horizon.

The inner ear contains 75,000 sensory hair cells that convert sound waves into electrical signals to the brain. Loud noises, drug toxicity, and genetic mutations can permanently damage the hair cells leading to hearing loss and dizziness. Over 15%  of the U.S. population have some form of hearing loss and that number swells to 67% for people over 75.

Due to the complex shape of the inner ear, the team grew the iPSCs into three dimensional balls of cells rather than growing them as a flat layer of cells on a petri dish. With educated guesses sprinkled in with some trial and error, the scientists, for the time, identified a recipe of proteins that stimulated the iPSCs to transform into inner ear tissue. And like any great recipe, it wasn’t so much the ingredient list but the timing that was key:

“If you apply these signals at the wrong time you can potentially generate a brain instead of an inner ear,” first author Dr. Karl Koehler said in an interview with Gizmodo. “The real breakthrough is that we figured out the exact timing to do each one of these [protein] treatments.”

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Senior author, Eri Hashino, Ph.D., and first author, Karl R. Koehler, Ph.D. Photo: Indiana University

Careful examination shows that the tissue, referred to as organoids, not only contained the sensory hair cells of the inner ear cell but also nerve cells, or neurons, that are responsible for relaying the sound waves to the brain. Koehler explained the importance of this result in a press release:

“We also found neurons, like those that transmit signals from the ear to the brain, forming connections with sensory cells. This is an exciting feature of these organoids because both cell types are critical for proper hearing and balance.”

Though it’s still early days, these iPSC-derived inner ear organoids are a key step toward the ultimate goal of repairing hearing loss. Senior author, Dr. Eri Hashino, talked about the team’s approach to reach that goal:

“Up until now, potential drugs or therapies have been tested on animal cells, which often behave differently from human cells. We hope to discover new drugs capable of helping regenerate the sound-sending hair cells in the inner ear of those who have severe hearing problems.”

This man’s research is no fish tale
And finally, we leave you this week with a cool article and video by STAT. It features Dr. Leonard Zon of Harvard University and his many, many tanks full of zebrafish. This little fish has made a huge splash in understanding human development and disease. But don’t take my word for it, watch the video!

A Fishy Tale: A gene that blocks regeneration in fish blocks cancer in humans

Evolution is a fascinating thing. Over time, the human race has evolved from cavemen to a bustling civilization fueled by technology, science, and economics. While we’ve gained many abilities that separate us from other mammals and our closest ancestors, the apes, we’ve also lost a number of skills along the way.

One of them is the ability to regenerate. Some animals such as lizards, fish, and frogs, have a robust capacity to regenerate entire limbs and organs while humans can only partially regenerate some tissues and organs on a much smaller scale. Why did we lose this advantageous trait?

A human gene that stops cancer also blocks regeneration

Image courtesy of Flickr.

Zebrafish. (Image courtesy of Flickr)

Scientists from UCSF have found a new piece to this evolutionary puzzle in a paper published today in eLife. They found that a gene responsible for preventing cells from growing uncontrollably into deadly cancers in humans is also able to block tissue regeneration in zebrafish.

Detailed in a UCSF news release, professor and senior author on the study, Jason Pomerantz, was always intrigued by why humans can’t regenerate limbs like salamanders. To answer these questions, he turned to model organisms like fish and amphibians:

Jason Pomerantz, UCSF

Jason Pomerantz, UCSF

In the last 10 to 15 years, as regenerative organisms like zebrafish have become genetically tractable to study in the lab, I became convinced that these animals might be able to teach us what is possible for human regeneration. Why can these vertebrates regenerate highly complex structures, while we can’t?

 

Like other scientists, Pomerantz was curious to know if humans “grew out of” their regenerative abilities in order to acquire systems that block cancer growth. Humans and other mammals have genes called tumor-suppressors that are important for regulating tissue differentiation during development and for preventing excessive cell growth and tumor formation after birth and beyond. Many of these tumor suppressor genes are conserved across a wide range of species, but Pomerantz knew of one that wasn’t shared between humans and regenerative animals, a gene called ARF.

Pomerantz and his team decided to see what happened when they added the human Arf gene into the genome of a highly regenerative animal, the zebrafish. While the addition of ARF did not affect zebrafish development, it did almost fully block their ability to regrow their tail fins after the tips were removed.

Normal zebrafish can regrow their tail fins after they are clipped, but fish that have the ARF gene cannot. (eLife)

Normal zebrafish can regrow their tail fins after they are clipped (top) , but fish that have the human ARF gene cannot (bottom). (Image from eLife)

Pomerantz explained ARF’s anti-regenerative role in the fish:

“It’s like the gene is mistaking the regenerating fin cells for aspiring cancer cells. And so it [ARF] springs into action to block it.”

Is Wolverine our future?

Wolverine. (Courtesy of wired.com)

Marvel’s Wolverine has regenerative powers. (Courtesy of wired.com)

Knowing that ARF suppresses tissue regeneration in fish, the obvious question that arises from this study is whether blocking the Arf gene in humans would promote tissue regeneration. Would doing this mean we could all be regenerative super heroes like Wolverine one day?

Pomerantz explained further in the UCSF new release that boosting regeneration in humans that need new organs or limbs could be possible but would require a careful balance to avoid setting off rampant tumor growth:

Future efforts to promote regeneration in humans will likely require carefully balanced suppression of this anti-tumor system. The same pathway in humans theoretically could be blocked to enhance researchers’ ability to grow model organs from stem cells in a laboratory dish, to enhance patients’ recovery from injury. Since tumor suppressors are thought to play a role in aging by limiting the rejuvenating potential of stem cells, blocking this pathway could even be a part of future anti-aging therapies.

Scientists will likely have to weigh the risks and benefits for human tissue regeneration on a case by case basis. Pomerantz concluded with this admission:

The ratio of risk and benefit has to be appropriate. For instance, there are certain congenital diseases that cause craniofacial deformities so severe that the risks of such a treatment might be clinically reasonable.

 

In living color: new imaging technique tracks traveling stem cells

Before blood stem cells can mature, before they can grow and multiply into the red blood cells that feed our organs, or the white blood cells that protect us from pathogens, they must go on a journey.

A blood stem cell en route to taking root in a zebrafish. [Credit: Boston Children's Hospital]

A blood stem cell en route to taking root in a zebrafish. [Credit:
Boston Children’s Hospital]

This journey, which takes place in the developing embryo, moves blood stem cells from their place of origin to where they will take root to grow and mature. That this journey happened was well known to scientists, but precisely how it happened remained shrouded in darkness.

But now, for the first time, scientists at Boston Children’s Hospital have literally shone a light on the entire process. In so doing, they have opened the door to improving surgical procedures that also rely on the movement of blood cells—such as bone marrow transplants, which are in essence stem cell transplants.

Reporting in today’s issue of the journal Cell, Boston Children’s senior investigator Leonard Zon and his team developed a way to visually track the trip that blood stem cells take in the developing embryo. As described in today’s news release, the same process that guides blood stem cells to the right place also occurs during a bone marrow transplant. The similarities between the two, therefore, could lead to more successful bone marrow transplants. According to the study’s co-first author Owen Tamplin:

“Stem cell and bone marrow transplants are still very much a black box—cells are introduced into a patient and later on we can measure recovery of the blood system, but what happens in between can’t be seen. Now we have a system where we can actually watch that middle step.”

And in the following video, Zon describes exactly how they did it:

As outlined in the above video, Zon and his team developed a transparent version of the zebrafish, a tiny model organism that is often used by scientists to study embryonic development. They then labeled blood stem cells in this transparent fish with a special fluorescent dye, so that the cells glowed green. And finally, with the help of both confocal and electron microscopy, they sat back and watched the blood stem cell take root in what’s called its niche—in beautiful Technicolor.

“Nobody’s ever visualized live how a stem cell interacts with its niche,” explained Zon. “This is the first time we get a very high-resolution view of the process.”

Further experiments found that the process in zebrafish closely resembled the process in mice—an indication that the same basic system could exist for humans.

With that possibility in mind, Zon and his team already have a lead on a way to improve the success of human bone marrow transplants. In chemical screening experiments, the team identified a chemical compound called lycorine that boosts the interaction between the zebrafish blood stem cell and its niche—thus promoting the number of blood stem cells as the embryo matures.

Does the lycorine compound (or an equivalent) exist to boost blood stem cells in mice? Or even in humans? That remains to be seen. But with the help of the imaging technology used by Zon and the Boston Children’s team—they have a good chance of being able to see it.

CIRM Scientists Discover Key to Blood Cells’ Building Blocks

Our bodies generate new blood cells—both red and white blood cells—each and every day. But reproducing that feat in a petri dish has proven far more difficult.

Pictured: sections from zebrafish embryos. Blood vessels are labeled in red, the protein complex that regulates inflammation green and cell nuclei in blue. The arrowhead indicates a potential HSC. The image at bottom right combines all channels. [Credit: UC San Diego School of Medicine]

Pictured: sections from zebrafish embryos. Blood vessels are labeled in red, the protein complex that regulates inflammation green and cell nuclei in blue. The arrowhead indicates a potential HSC. The image at bottom right combines all channels.
[Credit: UC San Diego School of Medicine]

But now, scientists have identified the missing ingredient to producing hematopoietic stem cells, or HSC’s—the type of stem cell that gives rise to all blood and immune cells in the body. The results, published last week in the journal Cell, describe how a newly discovered protein plays a key role in generating HSC’s in the developing embryo—giving scientists a more complete recipe to reproduce these cells in the lab.

The research, which was led by University of California, San Diego (UCSD) professor David Traver and supported by a grant from CIRM, offers renewed hope for the possibility of generating patient-specific blood or immune cells using induced pluripotent stem cell (iPS cell) technology.

As Traver explained in last week’s news release:

“The development of some mature cell lineages from iPS cells, such as cardiac or neural, has been reasonably straightforward, but not with HSCs. This is likely due, at least in part, to not fully understanding all the factors used by the embryo to generate HSCs.”

Indeed, the ability to generate HSCs has long challenged scientists, as outlined in a CIRM workshop from last year. But now, says Traver, they have found a crucial piece to the puzzle.

Specifically, the researchers investigated a signaling protein called tumor necrosis factor alpha—or TNFα for short— a protein known to be important for regulating inflammation and immunity. Previous research by this study’s first author, Raquel Espin-Palazon, and others also discovered it was related to the healthy function of blood vessels during embryonic development.

In this study, Traver, Espin-Palazon and the UCSD drilled down even further—and found that TNFα was required for the normal development of HSCs in the embryo. This surprised the research team, as the young embryo is generally considered to be sterile—with no need for a protein normally charged with regulating immune response to be switched on. Explained Traver:

“There was no expectation that pro-inflammatory signaling would be active at this time or in the blood-forming regions.”

While preliminary, establishing this relationship between TNFα and HSC formation will be a boon to researchers looking for new ways to generate large quantities of healthy, patient-specific red and white blood cells for those patients who so desperately need them.

Learn more about how stem cell technology could help treat blood diseases in our Thalassemia Fact Sheet.

Stem Cell Stories that Caught our Eye: A Zebrafish’s Stripes, Stem Cell Sound Waves and the Dangers of Stem Cell Tourism

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.

The zebrafish (Danio rerio) owes its name to a repeating pattern of blue stripes alternating with golden stripes. [Credit: MPI f. Developmental Biology/ P. Malhawar]

The zebrafish (Danio rerio) owes its name to a repeating pattern of blue stripes alternating with golden stripes. [Credit: MPI f. Developmental Biology/ P. Malhawar]

How the Zebrafish Got its Stripes. Scientists in Germany have identified the different pigment cells that emerge during embryonic development and that determine the signature-striped pattern on the skins of zebrafish—one of science’s most commonly studied model organisms. These results, published this week in the journal Science, will help researchers understand how patterns, from stripes to spots to everything in between, develop.

In the study, scientists at the Max Planck Institute for Developmental Biology mapped how three distinct pigment cells, called black cells, reflective silvery cells, and yellow cells emerge during development and arrange themselves into the characteristic stripes. While researchers knew these three cell types were involved in stripe formation, what they discovered here was that these cells form when the zebrafish is a mere embryo.

“We were surprised to observe such cell behaviors, as these were totally unexpected from what we knew about color pattern formation”, says Prateek Mahalwar, first author of the study, in a news release.

What most surprised the research team, according to the news release, was that the three cell types each travel across the embryo to form the skin from a different direction. According to Dr. Christiane Nüsslein-Volhard, the study’s senior author:

“These findings inform our way of thinking about color pattern formation in other fish, but also in animals which are not accessible to direct observation during development such as peacocks, tigers and zebras.”

Sound Waves Dispense Individual Stem Cells. It happens all the time in the lab: scientists need to isolate and study a single stem cell. The trick is, how best to do it. Many methods have been developed to achieve this goal, but now scientists at the Regenerative Medicine Institute (REMEDI) at NUI Galway and Irish start-up Poly-Pico Technologies Ltd. have pioneered the idea of using sound waves to isolate living stem cells, in this case from bone marrow, with what they call the Poly-Pico micro-drop dispensing device.

Poly-Pico Technologies Ltd., a start-up that was spun out from the University of Limerick in Ireland, has developed a device that uses sound energy to accurately dispense protein, antibodies and DNA at very low volumes. In this study, REMEDI scientists harnessed this same technology to dispense stem cells.

These results, while preliminary, could help improve our understanding of stem cell biology, as well as a number of additional applications. As Poly-Pico CEO Alan Crean commented in a news release:

“We are delighted to see this new technology opportunity emerge at the interface between biology and engineering. There are other exciting applications of Poly-Pico’s unique technology in, for example, drug screening and DNA amplification. Our objective here is to make our technology available to companies, and researchers, and add value to what they are doing. This is one example of such a success.”

The Dangers of Stem Cell Toursim. Finally, a story from ABC News Australia, in which they recount a woman’s terrifying encounter with an unproven stem cell technique.

In this story, Annie Levington, who has suffered from multiple scleoris (MS) since 2007, tells of her journey from Melbourne to Germany. She describes a frightening experience in which she paid $15,000 to have a stem cell transplant. But when she returned home to Australia, she saw no improvement in her MS—a neuroinflammatory disease that causes nerve cells to whither.

“They said I would feel the effects within the next three weeks to a year. And nothing – I had noticed nothing whatsoever. [My neurologist] sent me to a hematologist who checked my bloods and concluded there was no evidence whatsoever that I received a stem cell transplant.”

Sadly, Levington’s story is not unusual, though it is not as dreadful as other instances, in which patients have traveled thousands of miles to have treatments that not only don’t cure they condition—they actually cause deadly harm.

The reason that these unproven techniques are even being administered is based on a medical loophole that allows doctors to treat patients, both in Australia and overseas, with their own stem cells—even if that treatment is unsafe or unproven.

And while there have been some extreme cases of death or severe injury because of these treatments, experts warn that the most likely outcome of these untested treatments is similar to Levington’s—your health won’t improve, but your bank account will have dwindled.

Want to learn more about the dangers of stem cell tourism? Check out our Stem Cell Tourism Fact Sheet.