“Junk” DNA is development gold for the dividing embryo

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Single two-cell mouse embryos with nuclear LINE1 RNA labeled magenta – Credit Ramalho-Santos lab

The DNA in our cells provide the instructions to make proteins, the workhorses of our body. Yet less than 2% of the 3 billion base pairs (the structural units of DNA) in each of our cells are actually involved in protein production. The rest, termed non-coding DNA for not being involved in protein production, has roles in regulating genetic activity, but, largely, these genetic regions have remained a mystery causing some to mis-characterize it as “junk” DNA.

One of the largest components of these “junk” DNA regions are transposons, which make up 50% of the genome. Transposons are variable length DNA segments that are able to duplicate and re-insert themselves into different locations of the genome which is why they’re often called “jumping genes”.

Transposons have been implicated in diseases like cancer because of their ability to disrupt normal gene function depending on where the transposon inserts itself. Now, a CIRM-funded study in Miguel Ramalho-Santos’ laboratory at UCSF has found a developmental function for transposons in the dividing embryo. The report was published today in the Journal Cell.

Of the transposons identified in humans, LINE1 is the most common, composing 24% of the entire human genome. Many investigators in the field had observed that LINE1 is highly expressed in embryonic stem cells, which seemed paradoxical given that these pieces of DNA were previously thought to be either inert or harmful. Because this DNA was present at such high levels, the investigators decided to eliminate it from fertilized mouse embryos at the two-cell stage and observe how this affected development.

To their surprise, they found that the embryo was not able to progress beyond this stage. Further investigation revealed that LINE1, along with other proteins, is responsible for turning off the genetic program that maintains the two-cell state, thus allowing the embryo to further divide and develop.

Dr. Ramalho-Santos believes that this is a fine-tuned mechanism to ensure that the early stages of develop progress successfully. Because there are so many copies of LINE1 in the genome, even if one is not functional, it is likely that there will be functional back up, an important factor in ensuring early mistakes in embryo development do not occur.

In a press release, Dr. Ramalho-Santos states:

“We now think these early embryos are playing with fire but in a very calculated way. This could be a very robust mechanism for regulating development…I’m personally excited to continue exploring novel functions of these elements in development and disease.”

CIRM funded study results in the first ever in utero stem cell transplant to treat alpha thalassemia

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Dr. Tippi MacKenzie (left) of UCSF Benioff Children’s Hospital San Francisco, visits with newborn Elianna and parents Nichelle Obar and Chris Constantino. Photo by Noah Berger

Imagine being able to cure a genetic disorder before a baby is even born. Thanks to a CIRM funded study, what would have been a mere dream a couple of years ago has become a reality.

Drs. Tippi MacKenzie and Juan Gonzalez Velez of the University of California San Francisco (UCSF) have successfully treated alpha thalassemia in Elianna Constantino, using stem cells from her mother’s bone marrow. Alpha thalassemia is part of a group of blood disorders that impairs the body’s ability to produce hemoglobin, the molecule that is responsible for transporting oxygen throughout the body on red blood cells. Present in approximately 5% of the population, alpha thalassemia is particularly prevalent among individuals of Asian heritage. Treatment options for this disease are severely limited, generally requiring multiple rounds of blood transfusions or a bone marrow transplant which requires immunosuppressive therapy. Normally, fetuses die in the womb or the pregnancy is aborted because of the poor prognosis.

The revolutionary treatment pioneered at UCSF involved isolating blood stem cells (cells that are capable of turning into all blood cell types) from the mother’s bone marrow and injecting these cells into Elianna’s bloodstream via the umbilical vein. The doctors were able to observe the development of healthy blood cells in the baby’s blood stream, allowing for efficient oxygen transport throughout the baby’s body. Because the cells were transplanted at the fetal stage, a time when the immune system is not fully developed, there was low risk of rejection and the transplant occurred without aggressive immunosuppressive therapy.

The baby was born healthy earlier this year and has been allowed to return home. While it is still too early to tell how effective this treatment will be in the long term, it is very encouraging that both the mother and baby have endured the treatment thus far.

In a press release, Dr. MacKenzie states:

“Her healthy birth suggests that fetal therapy is a viable option to offer to families with this diagnosis.”

The in utero stem cell transplant was performed as part of a clinical trial conducted at the UCSF Benioff Children’s Hospitals in San Francisco and Oakland. The trial is currently enrolling 10 pregnant women to test the safety and effectiveness of this treatment over a wider population.

If successful, this type of treatment is particularly exciting because it could be expanded to other types of hereditary blood disorders such as sickle cell anemia and hemophilia.

 

 

 

Friday Stem Cell Round: Ask the Expert Facebook Live, Old Brain Cells Reveal Insights and Synthetic Development

Stem Cell Photo of the Week: We’re Live on Facebook Live!

Our stem cell photo of the week is a screenshot from yesterday’s Facebook Live event: “Ask the Expert: Stem Cells and Stroke”. It was our first foray into Facebook Live and, dare I say, it was a success with over 150 comments and 4,500 views during the live broadcast.

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Screen shot of yesterday’s Facebook Live event. Panelists included (from top left going clockwise): Sonia Coontz, Kevin McCormack, Gary Steinberg, MD, PhD and Lila Collins, PhD.

Our panel included Dr. Gary Steinberg, MD, PhD, the Chair of Neurosurgery at Stanford University, who talked about promising clinical trial results testing a stem cell-based treatment for stroke. Lila Collins, PhD, a Senior Science Officer here at CIRM, provided a big picture overview of the latest progress in stem cell therapies for stroke. Sonia Coontz, a patient of Dr. Steinberg’s, also joined the live broadcast. She suffered a devastating stroke several years ago and made a remarkable recovery after getting a stem cell therapy. She had an amazing story to tell. And Kevin McCormack, CIRM’s Senior Director of Public Communications, moderated the discussion.

Did you miss the Facebook Live event? Not to worry. You can watch it on-demand on our Facebook Page.

What other disease areas would you like us to discuss? We plan to have these Ask the Expert shows on a regular basis so let us know by commenting here or emailing us at info@cirm.ca.gov!

Brain cells’ energy “factories” may be to blame for age-related disease

Salk Institute researchers published results this week that shed new light on why the brains of older individuals may be more prone to neurodegenerative diseases like Parkinson’s and Alzheimer’s. To make this discovery, the team applied a technique they devised back in 2015 which directly converts skin cells into brain cells, aka neurons. The method skips the typical intermediate step of reprogramming the skin cells into induced pluripotent stem cells (iPSCs).

They collected skin samples from people ranging in age from 0 to 89 and generated neurons from each. With these cells in hand, the researchers then examined how increased age affects the neurons’ mitochondria, the structures responsible for producing a cell’s energy needs. Previous studies have shown a connection between faulty mitochondria and age-related disease.

While the age of the skin cells had no bearing on the health of the mitochondria, it was a different story once they were converted into neurons. The mitochondria in neurons derived from older individuals clearly showed signs of deterioration and produced less energy.

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Aged mitochondria (green) in old neurons (gray) appear mostly as small punctate dots rather than a large interconnected network. Credit: Salk Institute.

The researchers think this stark difference in the impact of age on skin cells vs. neurons may occur because neurons have higher energy needs. So, the effects of old age on mitochondria only become apparent in the neurons. In a press release, Salk scientist Jerome Mertens explained the result using a great analogy:

“If you have an old car with a bad engine that sits in your garage every day, it doesn’t matter. But if you’re commuting with that car, the engine becomes a big problem.”

The team is now eager to use this method to examine mitochondrial function in neurons derived from Alzheimer’s and Parkinson’s patient skin samples and compared them with skin-derived neurons from similarly-aged, healthy individuals.

The study, funded in part by CIRM, was published in Cell Reports.

“Synthetically” Programming embryo development

One of the most intriguing, most fundamental questions in biology is how an embryo, basically a non-descript ball of cells, turns into a complex animal with eyes, a brain, a heart, etc. A deep understanding of this process will help researchers who aim to rebuild damaged or diseased organs for patients in need.

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Researchers programmed cells to self-assemble into complex structures such as this one with three differently colored layers. Credit: Wendell Lim/UCSF

A fascinating report published this week describes a system that allows researchers to program cells to self-organize into three-dimensional structures that mimic those seen during early development. The study applied a customizable, synthetic signaling molecule called synNotch developed in the Wendell Lim’s UCSF lab by co-author Kole Roybal, PhD, now an assistant professor of microbiology and immunology at UCSF, and Leonardo Morsut, PhD, now an assistant professor of stem cell biology and regenerative medicine at the University of Southern California.

A UCSF press release by Nick Weiler describes how synNotch was used:

“The researchers engineered cells to respond to specific signals from neighboring cells by producing Velcro-like adhesion molecules called cadherins as well as fluorescent marker proteins. Remarkably, just a few simple forms of collective cell communication were sufficient to cause ensembles of cells to change color and self-organize into multi-layered structures akin to simple organisms or developing tissues.”

Senior author Wendell Lim also explained how this system could overcome the challenges facing those aiming to build organs via 3D bioprinting technologies:

“People talk about 3D-printing organs, but that is really quite different from how biology builds tissues. Imagine if you had to build a human by meticulously placing every cell just where it needs to be and gluing it in place. It’s equally hard to imagine how you would print a complete organ, then make sure it was hooked up properly to the bloodstream and the rest of the body. The beauty of self-organizing systems is that they are autonomous and compactly encoded. You put in one or a few cells, and they grow and organize, taking care of the microscopic details themselves.”

Study was published in Science.

CCSF’s CIRM Bridges scholars: the future of stem cell research is in good hands

In need of an extra dose of inspiration? You might read a great book or listen to that podcast your friend recommended. You might even take a stroll along the beach. But I can do you one better: go to a conference poster session where young stem cell scientists describe their research.

That’s what I did last week at the City College of San Francisco’s (CCSF) Bioscience Symposium held at UC San Francisco’s Genentech Hall. It’s a day-long conference that showcases the work of CCSF Bioscience interns and gives them a chance to present the results of their research projects, network with their peers and researchers, hear panelists talk about careers in biotechnology and participate in practice job interviews.

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CCSF’s CIRM Bridges Scholars (clockwise from top left): Vanessa Lynn Herrara, Viktoriia Volobuieva, Christopher Nosworthy and Sofiana E. Hamama.

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CCSF’s CIRM Bridges Scholars (clockwise from top left): Seema Niddapu, Mark Koontz, Karolina Kaminska and Iris Avellano

Eight of the dozens of students in attendance at the Symposium are part of the CIRM-funded Bridges Stem Cell Internship program at CCSF. It’s one of 14 CIRM Bridges programs throughout the state that provides paid stem cell research internships to students at universities and colleges that don’t have major stem cell research programs. Each Bridges internship includes thorough hands-on training and education in stem cell research, and direct patient engagement and outreach activities that engage California’s diverse communities.

In the CCSF Bridges Program, directed by Dr. Carin Zimmerman, the students do a 9-month paid internship in top notch labs at UCSF, the Gladstone Institutes and Blood System Research Institute. As I walked from poster to poster and chatted with each Bridges scholar, their excitement and enthusiasm for carrying out stem cell research was plain to see. It left me with the feeling that the future of stem cell research is in good hands and, as I walked into the CIRM office the next day, I felt re-energized to tackle the Agency’s mission to accelerate stem cell treatment for patients with unmet medical needs. But don’t take my word for it, listen to the enthusiastic perspectives of Bridges scholars Mark Koontz and Iris Avellano in this short video.

Livers skip stem cells, build missing structures from scratch via direct cell identity conversion

Stem cells…eh, who needs them anyway?!

That’s what you might be thinking after today, at least for some forms of liver disease. That’s because a team of researchers from UCSF and Cincinnati Children’s Hospital Medical Center just published results in Nature showing liver cells can directly change identity, or transdifferentiate, in order to build, from scratch, structures missing due to disease.

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The liver contains a network of tubes called bile ducts that carry fat-digesting bile to the small intestine via the gallbladder.
Image: National Cancer Inst.

The extraordinary regenerative power of the liver in animals is well-documented. A human liver, for instance, can fully regrow from just 25% of its original mass. That’s thanks to the hepatocyte, the main type of liver cell, that has the ability to replenish pre-existing tissue lost due to disease or injury. What hasn’t been as clear cut, is whether the hepatocyte has the capacity to change identity and build functional liver structures from scratch that never developed in the first place due to genetic disorders.

To examine that possibility, the study – funded in part by CIRM – focused on an inherited liver disease called Alagille syndrome which is caused by abnormal bile ducts. Produced by the liver, bile helps digest fats in our diet. It travels from the liver via bile ducts – tree branch-like tube structures in the liver – to the gallbladder, where it’s stored before moving on to the small intestine. In Alagille syndrome, the bile ducts are fewer in number, narrower in size or altogether missing. As a result, the bile builds up in the liver causing scarring and severe damage. Nearly half of all those with Alagille syndrome, require a liver transplant, usually in childhood.

The research team mimicked the symptoms of Alagille syndrome in mice by genetically engineering the animals to lack cholangiocytes, the cells that form bile ducts. Sure enough, liver damage from bile buildup was observed in these mice at birth due to the missing bile duct structures, also called the biliary tree. However, 90% of the mice survived and eventually formed a functional biliary tree. The team went on to show, for the first time, that the hepatocytes had converted en masse into cholangiocytes and created the wholly new bile ducts.

liver cell switching

Mice that mimic Alagille syndrome are born without the branches of the biliary tree, an important “plumbing system” in the liver (A), but show a near-normal biliary system as adults (B). To build the missing branches, liver cells switch identity and form tubes, shown in green, that connect to the trunk of the biliary tree, shown in blue (C). Image: Cincinnati Children’s

The underlying molecular mechanisms of this process were further examined. The researchers showed that the lack of a particular gene activity pathway due to the absence of cholangiocytes during development causes a replacement pathway, stimulated by a protein called TGF-beta, to kick into gear. As a result, the hepatocytes convert into cholangiocytes and form bile ducts. To make a direct connection with the human form of the disease, the researchers found evidence that TGF-beta is active in the liver samples of some patients but not in the livers from healthy individuals.

With this Alagille syndrome mouse model in hand, the researchers want to identify which transcription factors – proteins that bind DNA and regulate gene activity – are involved in changing the liver cells into bile duct cells. Holger Willenbring, MD, PhD, a senior author and CIRM grantee, explained the rationale behind this approach in a press release:

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Holger Willenbring

“Using transcription factors to make bile ducts from hepatocytes has potential as a safe and effective therapy. With our finding that an entire biliary system can be ‘retrofitted’ in the mouse liver, I am encouraged that this eventually will work in patients.”

So rather than developing a stem cell-based therapy in the lab which is then transplanted into a patient, this approach would rely on stimulating the regenerative capacity of liver cells that are already inside the body. And if it eventually works in patients with Alagille syndrome, which only affects 1 in 30,000, it’s possible it could be applied to other liver diseases as well.

Therapies Targeting Cancer, Deadly Immune Disorder and Life-Threatening Blood Condition Get Almost $32 Million Boost from CIRM Board

An innovative therapy that uses a patient’s own immune system to attack cancer stem cells is one of three new clinical trials approved for funding by CIRM’s Governing Board.

Researchers at the Stanford University School of Medicine were awarded $11.9 million to test their Chimeric Antigen Receptor (CAR) T Cell Therapy in patients with B cell leukemias who have relapsed or are not responding after standard treatments, such as chemotherapy.CDR774647-750Researchers take a patient’s own T cells (a type of immune cell) and genetically re-engineer them to recognize two target proteins on the surface of cancer cells, triggering their destruction. In addition, some of the T cells will form memory stem cells that will survive for years and continue to survey the body, killing any new or surviving cancer cells.

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Maria T. Millan

“When a patient is told that their cancer has returned it can be devastating news,” says Maria T. Millan, MD, President & CEO of CIRM. “CAR T cell therapy is an exciting and promising new approach that offers us a way to help patients fight back against a relapse, using their own cells to target and destroy the cancer.”

 

 

Sangamo-logoThe CIRM Board also approved $8 million for Sangamo Therapeutics, Inc. to test a new therapy for beta-thalassemia, a severe form of anemia (lack of healthy red blood cells) caused by mutations in the beta hemoglobin gene. Patients with this genetic disorder require frequent blood transfusions for survival and have a life expectancy of only 30-50 years. The Sangamo team will take a patient’s own blood stem cells and, using a gene-editing technology called zinc finger nuclease (ZFN), turn on a different hemoglobin gene (gamma hemoglobin) that can functionally substitute for the mutant gene. The modified blood stem cells will be given back to the patient, where they will give rise to functional red blood cells, and potentially eliminate the need for chronic transfusions and its associated complications.

UCSFvs1_bl_a_master_brand@2xThe third clinical trial approved is a $12 million grant to UC San Francisco for a treatment to restore the defective immune system of children born with severe combined immunodeficiency (SCID), a genetic blood disorder in which even a mild infection can be fatal. This condition is also called “bubble baby disease” because in the past children were kept inside sterile plastic bubbles to protect them from infection. This trial will focus on SCID patients who have mutations in a gene called Artemis, the most difficult form of SCID to treat using a standard bone marrow transplant from a healthy donor. The team will genetically modify the patient’s own blood stem cells with a functional copy of Artemis, with the goal of creating a functional immune system.

CIRM has funded two other clinical trials targeting different approaches to different forms of SCID. In one, carried out by UCLA and Orchard Therapeutics, 50 children have been treated and all 50 are considered functionally cured.

This brings the number of clinical trials funded by CIRM to 48, 42 of which are active. There are 11 other projects in the clinical trial stage where CIRM funded the early stage research.

The Story of a South African Bubble Boy and a Gene Therapy That Gave Him His Life Back

Ayaan Isaacs, health24

Ayaan Isaacs was born in South Africa on March 4th, 2016 as a seemingly healthy baby. But only a few days in to life, he contracted a life-threatening liver infection. He thankfully survived, only to have the doctors discover a few weeks later that he had something much more troubling – a rare disease that left him without a functioning immune system.

Ayaan was diagnosed with X-linked severe combined immunodeficiency (SCID), which is often referred to as ‘bubble baby’ disease because patients are extremely susceptible to infection and must live in sterile environments. SCID patients can be cured with a blood stem cell transplant if they have a genetically matched donor. Unfortunately for Ayaan, only a partially matched donor was available, which doesn’t guarantee a positive outcome.

Ayaan’s parents were desperate for an alternative treatment to save Ayaan’s life. It was at this point that they learned about a clinical trial at St. Jude Children’s Research hospital in Memphis, Tennessee. The trial is treating SCID patients with a stem cell gene therapy that aims to give them a new functioning immune system. The therapy involves extracting the patient’s blood-forming stem cells and genetically correcting the mutation that causes SCID. The corrected blood stem cells are then transplanted back into the patient where they rebuild a healthy immune system.

Ayaan was able to enroll in the trial, and he was the first child in Africa to receive this life-saving gene therapy treatment. Ayaan’s journey with bubble boy disease was featured by South Africa’s health24 earlier this year. In the article, his mom Shamma Sheik talked about the hope that this gene therapy treatment brought to their family.

“No child should have to die just because they are unable to find a donor. Gene therapy offered Ayaan a chance at life that he ordinarily would not have had. I was fortunate to have found an alternative therapy that is working and already showing remarkable results. We are mindful that this is still an experimental treatment and there are complications that can arise; however, I am very optimistic that he will return to South Africa with a functioning immune system.”

Carte Blanche, an investigative journalism program in South Africa, did a feature video of Ayaan in February. Although the video is no longer available on their website, it did reveal that four months after Ayaan’s treatment, his condition started to improve suggesting that the treatment was potentially working.

We’ve written previously about another young boy named Ronnie who was diagnosed with X-linked SCID days after he was born. Ronnie also received the St. Jude stem cell gene therapy in a CIRM-funded clinical trial at the UCSF Benioff Children’s Hospital. Ronnie was treated when he was six months old and just celebrated his first birthday as a healthy, vibrant kid thanks to this trial. You can hear more about Ronnie’s moving story from his dad, Pawash Priyank, in the video below.

Our hope is that powerful stories like Ayaan’s and Ronnie’s will raise awareness about SCID and the promising potential of stem cell gene therapies to cure patients of this life-threatening immune disease.

Ronnie and his parents celebrating his 1st birthday. (Photo courtesy of Pawash Priyank)


Related Links:

Patients at the heart of Alpha Stem Cell Clinics Symposium

I have been to a lot of stem cell conferences over the years and there’s one recent trend I really like: the growing importance and frequency of the role played by patient advocates.

There was a time, not so long ago, when having a patient advocate speak at a scientific conference was almost considered a novelty. But more and more it’s being seen for what it is, an essential item on the agenda. After all, they are the reason everyone at that conference is working. It’s all about the patients.

That message was front and center at the 3rd Annual CIRM Alpha Stem Cell Clinics Network Symposium at UCLA last week. The theme of the symposium was the Delivery of Stem Cell Therapeutics to Patients. There were several fascinating scientific presentations, highlighting the progress being made in stem cell research, but it was the voices of the patient advocates that were loudest and most powerful.

First a little background. The CIRM Alpha Stem Cell Clinics Network consists of six major medical centers – UCLA/UC Irvine (joint hosts of this conference), UC San Diego, City of Hope, UC San Francisco and UC Davis. The Network was established with the goal of accelerating the development and delivery of high-quality stem cell clinical trials to patients. This meeting brought together clinical investigators, scientists, patients, patient advocates, and the public in a thoughtful discussion on how novel stem cell therapies are now a reality.

It was definitely thoughtful. Gianna McMillan, the Co-Founder and Executive Director of “We Can, Pediatric Brain Tumor Network” set the tone with her talk titled, “Tell Me What I Need to Know”. At age 5 her son was diagnosed with a brain tumor, sending her life into a tailspin. The lessons she learned from that experience – happily her son is now a healthy young man – drive her determination to help others cope with similar situations.

Calling herself an “in the trenches patient advocate champion” she says:

“In the old days doctors made decisions on behalf of the patients who meekly and gratefully did what they were told. It’s very different today. Patients are better informed and want to be partners in the treatment they get. But yet this is not an equal partnership, because subjects (patients) are always at a disadvantage.”

She said patients often don’t speak the language of the disease or understand the scientific jargon doctors use when they talk about it. At the same time patients are wrestling with overwhelming emotions such as fear and anxiety because their lives have been completely overturned.

Yet she says a meaningful partnership is possible as long as doctors keep three basic questions in mind when dealing with people who are getting a new diagnosis of a life-threatening or life-changing condition:

  • Tell me what I need to know
  • Tell me in language I can understand
  • Tell me again and again

It’s a simple formula, but one that is so important that it needs to be stated over and over again. “Tell me again. And again. And again.”

David Mitchell, the President and Founder of Patients for Affordable Drugs, tackled another aspect of the patient experience: the price of therapies. He posed the question “What good is a therapy if no one can afford it?”

David’s organization focuses on changing policy at the state and federal level to lower the price of prescription drugs. He pointed out that many other countries charge lower prices for drugs than the US, in part because those countries’ governments negotiate directly with drug companies on pricing.

He says if we want to make changes in this country that benefit patients then patient have to become actively involved in lobbying their government, at both the state and local level, for more balanced prices, and in supporting candidates for public office who support real change in drug-pricing policy.

It’s encouraging to see that just as the field of stem cell research is advancing so too is the prominence of the patient’s voice. The CIRM Alpha Stem Cell Clinics Network is pushing the field forward in exciting ways, and the patients are becoming an increasingly important, and vital part of that. And that is as it should be.

Stem Cell Roundup: No nerve cells for you, old man; stem cells take out the trash; clues to better tattoo removal

Stem cell image of the week: Do they or don’t they? The debate on new nerve cell growth in adult brain rages on.

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Young neurons (green) are shown in the human hippocampus at the ages of (from left) birth, 13 years old and 35 years old. Images by Arturo Alvarez-Buylla lab

For the longest time, it was simply a given among scientists that once you reach adulthood, your brain’s neuron-making days were over. Then, over the past several decades, evidence emerged that the adult brain can indeed make new neurons, in a process called neurogenesis. Now the pendulum of understanding may be swinging back based on research reported this week out of Arturo Alvarez-Buylla’s lab at UCSF.

Through the careful examination of 59 human brain samples (from post mortem tissue and those collected during epilepsy surgery), Alvarez-Buylla’s team in collaboration with many other labs around the world, found lots of neurogenesis in neonatal and newborn brains. But after 1 year of age, a steep drop in the number of new neurons was observed. Those numbers continued to plummet through childhood and were barely detectable in samples from teens. New neurons were undetectable in adult brain samples.

This week’s stem cell image shows this dramatic decline of new neurons when comparing brain samples from a newborn, a 13 year-old and a 35 year-old.

It was no surprise that these surprising results, published in Nature, got quite a bit of attention by a wide range of news outlets including the LA Times, CNN, The Scientist and NPR to name just a few.

Limitless life of stem cells requires taking out the trash

It’s minding blowing to me that, given the proper nutrients, an embryonic stem cell in a lab dish can exist indefinitely. The legendary fountain of youth that Ponce de León searched in vain for is actually hidden inside these remarkable cells. So how do they do it? It’s a tantalizing question for researchers because the answers could lead to a better understanding of and eventually novel therapies for age-related diseases.

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Cartoon of a proteosome, the cell’s garbage disposal. Image: Wikipedia

A team from the University of Cologne reports this week on a connection between the removal of degraded proteins and the longevity of stem cells. Cells in general use special enzymes to tag wonky proteins for the cellular trash heap, called a proteasome. Without this ability to clean up, unwanted proteins can accumulate and make cells unhealthy, a scenario that is seen in age-related diseases like Alzheimer’s. The research team found that reducing the protein disposal activity in embryonic stem cells disrupted characteristics that are specific to these cells. So, one way stem cells may keep their youthful appearance is by being good about taking out their trash.

The study was published in Scientific Reports and picked up by Science Daily.

Why tattoos stay when your skin cells don’t ( by Kevin McCormack)

We replace our skin cells every two or three weeks. As each layer dies, the stem cells in the skin replace them with a new batch. With that in mind you’d think that a tattoo, which is just ink injected into the skin with a needle, would disappear as each layer of skin is replaced. But obviously it doesn’t. Now some French researchers think they have figured out why.

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Thank your macrophages for keeping your tattoo intact. Tattoo by: Sansanana

It’s not just fun science, published in the Journal of Experimental Medicine, it could also mean that that embarrassing tattoo you got saying you would love Fred or Freda forever, can one day be easily removed.

The researchers found that when the tattoo needle inflicts a wound on the skin, specialized cells called macrophages flock to the site and take up the ink. As those macrophages die, instead of the ink disappearing with them, new macrophages come along, gobble up the ink and so the tattoo lives on.

In an interview with Health News Digest, Bernard Malissen, one of the lead investigators, says the discovery, could help erase a decision made in a moment of madness:

“Tattoo removal can be likely improved by combining laser surgery with the transient ablation of the macrophages present in the tattoo area. As a result, the fragmented pigment particles generated using laser pulses will not be immediately recaptured, a condition increasing the probability of having them drained away via the lymphatic vessels.”

New Insights into Adult Neurogenesis

To be a successful scientist, you have to expect the unexpected. No biological process or disease mechanism is ever that simple when you peel off its outer layers. Overtime, results that prove a long-believed theory can be overturned by new results that suggest an alternate theory.

UCSF scientist Arturo Alvarez-Buylla is well versed with the concept of unexpected results. His lab’s research is focused on understanding adult neurogenesis – the process of creating new nerve cells (called neurons) from neural stem cells (NSCs).

For a long time, the field of adult neurogenesis has settled on the theory that brain stem cells divide asymmetrically to create two different types of cells: neurons and neural stem cells. In this way, brain stem cells populate the brain with new neurons and they also self-renew to maintain a constant stem cell supply throughout the adult animal’s life.

New Insights into Adult Neurogenesis

Last week, Alvarez-Buylla and his colleagues published new insights on adult neurogenesis in mice in the journal Cell Stem Cell. The study overturns the original theory of asymmetrical neural stem cell division and suggests that neural stem cells divide in a symmetrical fashion that could eventually deplete their stem cell population over the lifetime of the animal.

Arturo Alvarez-Buylla explained the study’s findings in an email interview with the Stem Cellar:

Arturo Alvarez-Bulla

“Our results are not what we expected. Our work shows that postnatal NSCs are not being constantly renewed by splitting them asymmetrically, with one cell remaining as a stem cell and the other as a differentiated cell. Instead, self-renewal and differentiation are decoupled and achieved by symmetric divisions.”

In brief, the study found that neural stem cells (called B1 cells) divide symmetrically in an area of the adult mouse brain called the ventricular-subventricular zone (V-SVZ). Between 70%-80% of those symmetric divisions produced neurons while only 20%-30% created new B1 stem cells. Alvarez-Buylla said that this process would result in the gradual depletion of B1 stem cells over time and seems to be carefully choreographed for the length of the lifespan of a mouse.

What does this mean?

I asked Alvarez-Buylla how his findings in mice will impact the field and whether he expects human adult neurogenesis to follow a similar process. He explained,

“The implications are quite wide, as it changes the way we think about neural stem cell retention and aging. The cells do not seem open ended with unlimited potential to be renewed, which results in a progressive decrease in NSC number and neurogenesis with time.  Understanding the mechanisms regulating proliferation of NSCs and their self-renewal also provides new insights into how the whole process of neurogenesis is choreographed over long periods by suggesting that differentiation (generation of neurons) is regulated separately from renewal.”

He further explained that mice generate new neurons in the V-SVZ brain region throughout their lifetime while humans only appear to generate new neurons during infancy in the equivalent region of the human brain called the SVZ. In humans, he said, it remains unclear where and how many neural stem cells are retained after birth.

I also asked him how these findings will impact the development of neural stem cell-based therapies for neurological or neurodegenerative diseases. Alvarez-Buylla shared interesting insights:

“Our data also indicate that upon a self-renewing division, sibling NSCs may not be equal to each other. While one NSC might stay quiescent [non-dividing] for an extended period of time, its sister cell might become activated earlier on and either undergo another round of self-renewal or differentiate. Thus, for cell-replacement therapies it will be important to understand which kind of neuron the NSC of interest can produce, and when. The use of NSCs for brain repair requires a detailed understanding of which NSC subset will be utilized for treatment and how to induce them to produce progeny. The study also suggests that factors that control NSC renewal may be separate from those that control generation of neurons.”

Scientists developing adult NSC-based therapies will definitely need to take note of Alvarez-Buylla’s findings as some NSC populations might be more successful therapeutically than others.

Neural Stem Cells in the Wild

I’ll conclude with a beautiful image that the study’s first author, Kirsten Obernier, shared with me. It’s shows the V-SVZ of the mouse brain and a neural stem cell in red making contact with a blood vessel in green and neurons in blue.

Image of the mouse brain with a neural stem cell in red. (Credit: Kirsten Obernier, UCSF)

Kirsten described the complex morphology of B1 NSCs in the mouse brain and their dynamic behavior, which Kirsten observed by taking a time lapsed video of NSCs dividing in the mouse V-SVZ. Obernier and Alvarez-Buylla hypothesize that these NSCs could be receiving signals from their surrounding environment that tell them whether to make neurons or to self-renew.

Clearly, further research is necessary to peel back the complex layers of adult neurogenesis. If NSC differentiation is regulated separately from self-renewal, their insights could shed new light on how conditions of unregulated self-renewal like brain tumors develop.