Stem Cell Roundup: watching brain cells in real time, building better heart cells, and the plot thickens on the adult neurogenesis debate

Here are the stem cell stories that caught our eye this week.

Watching brain cells in real time

This illustration depicts a new method that enables scientists to see an astrocyte (green) physically interacting with a neuronal synapse (red) in real time, and producing an optical signal (yellow). (Khakh Lab, UCLA Health)

Our stem cell photo of the week is brought to you by the Khakh lab at UCLA Health. The lab developed a new method that allows scientists to watch brain cells interact in real time. Using a technique called fluorescence resonance energy-transfer (FRET) microscopy, the team can visualize how astrocytes (key support cells in our central nervous system) and brain cells called neurons form connections in the mouse brain and how these connections are affected by diseases like Alzheimer’s and ALS.

Baljit Khakh, the study’s first author, explained the importance of their findings in a news release:

“This new tool makes possible experiments that we have been wanting to perform for many years. For example, we can now observe how brain damage alters the way that astrocytes interact with neurons and develop strategies to address these changes.”

The study was published this week in the journal Neuron.


Turn up the power: How to build a better heart cell (Todd Dubnicoff)

For years now, researchers have had the know-how to reprogram a donor’s skin cells into induced pluripotent stem cells (iPSCs) and then specialize them into heart muscle cells called cardiomyocytes. The intervening years have focused on optimizing this method to accurately model the biology of the adult human heart as a means to test drug toxicity and ultimately develop therapies for heart disease. Reporting this week in Nature, scientists at Columbia University report an important step toward those goals.

The muscle contractions of a beating heart occur through natural electrical impulses generated by pacemaker cells. In the case of lab-grown cardiomyocytes, introducing mechanical and electrical stimulation is required to reliably generate these cells. In the current study, the research team showed that the timing and amount of stimulation is a critical aspect to the procedure.

The iPS-derived cardiomyocytes have formed heart tissue that closely mimics human heart functionality at over four weeks of maturation. Credit: Gordana Vunjak-Novakovic/Columbia University.

The team tested three scenarios on iPSC-derived cardiomyocytes (iPSC-CMs): no electrical stimulation for 3 weeks, constant stimulation for 3 weeks, and finally, two weeks of increasingly higher stimulation followed by a week of constant stimulation. This third setup mimics the changes that occur in a baby’s heart just before and just after birth.

These scenarios were tested in 12 day-old and 28 day-old iPSC-CMs. The results show that only the 12 day-old cells subjected to the increasing amounts of stimulation gave rise to fully mature heart muscle cells. On top of that, it only took four weeks to make those cells. Seila Selimovic, Ph.D., an expert at the National Institutes of Health who was not involved in the study, explained the importance of these findings in a press release:

“The resulting engineered tissue is truly unprecedented in its similarity to functioning human tissue. The ability to develop mature cardiac tissue in such a short time is an important step in moving us closer to having reliable human tissue models for drug testing.”

Read more at: https://phys.org/news/2018-04-early-bioengineered-human-heart-cells.html#jCp


Yes we do, no we don’t. More confusion over growing new brain cells as we grow older (Kevin McCormack)

First we didn’t, then we did, then we didn’t again, now we do again. Or maybe we do again.

The debate over whether we are able to continue making new neurons as we get older took another twist this week. Scientists at Columbia University said their research shows we do make new neurons in our brain, even as we age.

This image shows what scientists say is a new neuron in the brain of an older human. A new study suggests that humans continue to make new neurons throughout their lives. (Columbia University Irving Medical Center)

In the study, published in the journal Cell Stem Cell, the researchers examined the brains of 28 deceased donors aged 14 to 79. They found similar numbers of precursor and immature neurons in all the brains, suggesting we continue to develop new brain cells as we age.

This contrasts with a UCSF study published just last month which came to the opposite conclusion, that there was no evidence we make new brain cells as we age.

In an interview in the LA Times, Dr. Maura Boldrini, the lead author on the new study, says they looked at a whole section of the brain rather than the thin tissues slices the UCSF team used:

“In science, the absence of evidence is not evidence of absence. If you can’t find something it doesn’t mean that it is not there 100%.”

Well, that resolves that debate. At least until the next study.

Stem Cell Roundup: Rainbow Sherbet Fruit Fly Brains, a CRISPR/iPSC Mash-up and more

This week’s Round Up is all about the brain with some CRISPR and iPSCs sprinkled in:

Our Cool Stem Cell Image of the Week comes from Columbia University’s Zuckerman Institute:

Mann-SC-Hero-01-19-18

(Credit: Jon Enriquez/Mann Lab/Columbia’s Zuckerman Institute).

This rainbow sherbet-colored scientific art is a microscopy image of a fruit fly nervous system in which brain cells were randomly labeled with different colors. It was a figure in a Neuron study published this week showing how cells derived from the same stem cells can go down very different developmental paths but then later are “reunited” to carry out key functions, such as in this case, the nervous system control of leg movements.


A new therapeutic avenue for Parkinson’s diseaseBuck Institute

Many animal models of Parkinson’s disease are created by mutating specific genes to cause symptoms that mimic this incurable, neurodegenerative disorder. But, by far, most cases of Parkinson’s are idiopathic, a fancy term for spontaneous with no known genetic cause. So, researchers at the Buck Institute took another approach: they generated a mouse model of Parkinson’s disease using the pesticide, paraquat, exposure to which is known to increase the risk of the idiopathic form of Parkinson’s.

Their CIRM-funded study in Cell Reports showed that exposure to paraquat leads to cell senescence – in which cells shut down and stop dividing – particularly in astrocytes, brain cells that support the function of nerve cells. Ridding the mice of these astrocytes relieved some of the Parkinson’s like symptoms. What makes these results so intriguing is the team’s analysis of post-mortem brains from Parkinson’s patients also showed the hallmarks of increased senescence in astrocytes. Perhaps, therapeutic approaches that can remove senescent cells may yield novel Parkinson’s treatments.


Discovery may advance neural stem cell treatments for brain disordersSanford-Burnham Prebys Medical Discovery Institute (via Eureka Alert)

Another CIRM-funded study published this week in Nature Neuroscience may also help pave the way to new treatment strategies for neurologic disorders like Parkinson’s disease. A team at Sanford Burnham Prebys Medical Discovery Institute (SBP) discovered a novel gene regulation system that brain stem cells use to maintain their ability to self-renew.

The study centers around messenger RNA, a molecular courier that transcribes a gene’s DNA code and carries it off to be translated into a protein. The team found that the removal of a chemical tag on mRNA inside mouse brain stem cells caused them to lose their stem cell properties. Instead, too many cells specialized into mature brain cells leading to abnormal brain development in animal studies. Team lead Jing Crystal Zhao, explained how this finding is important for future therapeutic development:

CrystalZhao_headshot

Crystal Zhao

“As NSCs are increasingly explored as a cell replacement therapy for neurological disorders, understanding the basic biology of NSCs–including how they self-renew–is essential to harnessing control of their in vivo functions in the brain.”


Researchers Create First Stem Cells Using CRISPR Genome ActivationThe Gladstone Institutes

Our regular readers are most likely familiar with both CRISPR gene editing and induced pluripotent stem cell (iPSC) technologies. But, in case you missed it late last week, a Cell Stem Cell study out of Sheng Ding’s lab at the Gladstone Institutes, for the first time, combined the two by using CRISPR to make iPSCs. The study got a lot of attention including a review by Paul Knoepfler in his blog The Niche. Check it out for more details!

 

Bioengineers make breathtaking step toward building a lung

Tissue engineers have made amazing progress when it comes to using stem cells to build tissues such as blood vessels, which have relatively simple tubular shape. In fact, a late stage CIRM-funded clinical trial run by Humacyte is testing an engineered vein to improve dialysis treatment for people with kidney disease. Building a lung that works properly, on the other hand, has proven elusive due in no small part to its extremely intricate structure. But in a Science Advances report published yesterday, Columbia University bioengineers describe a potentially breakthrough method for building a functional lung in the lab.

Building a better lung that removes and repopulates lung cells without hurting blood vessels. Figure courtesy of N. Valerio Dorrello and Gordana Vunjak-Novakovic, Columbia University.

Lung disease tends to not get as much attention as other deadly diseases like cancer and heart failure. Yet it’s the world’s third leading cause of death with 400,000 deaths per year in just the United States. The only true treatment is a very drastic one: a lung transplant. This option is not very attractive even to those with severe disease because it’s a very expensive procedure that only has a 10-20% survival rate after 10 years. On top of that, donor lungs are in very short supply. So, clinicians and their patients are in desperate need for other approaches.

Tissue engineering approaches to building a lung face many challenges due to the organ’s complex structure. How complex, you ask? Science writer and scientist, Shelly Fan, uses a great analogy to describe it in her Singularity Hub article about this study:

“The lung is a real jungle: at the microscopic level, the tree-like airways contain alveoli, tiny bubble-like structures where the lungs exchange gas with our blood. Both arteries and veins enwrap the alveoli like two sets of mesh pockets.”

Now, one approach to building an organ is to start from scratch by manufacturing a synthetic scaffold resembling the shape of the organ and then seeding it with stem cells or other precursor cells. But because of this complicated microscopic jungle, bioengineers have steered clear of this path. Instead, the Columbia team has generated a natural scaffold by removing the cells from rat lungs using detergents. What’s left behind is a lung “skeleton” of proteins and molecules called the extracellular matrix that’s devoid of cells.

Building a better lung that removes and repopulates lung cells without hurting blood vessels. Figure courtesy of N. Valerio Dorrello and Gordana Vunjak-Novakovic, Columbia University.

In previous experiments using rat lungs, the team stripped out the lung cells, called epithelial cells, which are the type typically damaged in lung disease. Their method also removed the blood vessel cells, called endothelial cells, which make up the vascular system that is key to taking up the oxygen inhaled into the lungs. While repopulating the functional epithelial cells has been achieved, restoring the blood vessels is another story as mentioned in a university press release:

“An intact vascular network—missing in these scaffolds—is critical not only for maintaining the blood-gas barrier and allowing for proper graft function, but also for supporting the cells introduced to regenerate the lung. This has proved to be a daunting challenge.”

So, the current study attempted to only clear out the lung epithelial cells without disturbing the blood vessels to see if they would have better results. This approach makes sense on another level when envisioning future clinical applications: the therapy would be less complex if you only had to remove the diseased cells, which typically are the lung epithelial cells.

The researchers devised a cell removal method that was specific to the airways so that only epithelial cells would be cleared away. A battery of tests showed that, that although the lungs lost much of their ability to inflate and expand, the blood system remained intact after the procedure. The team then introduced either human epithelial cells or human induced pluripotent stem cell-derived epithelial cells into the scaffold. Within a day, they watched as the cells began to repopulate the lung in the correct areas. Follow-up experiments showed that the addition of new epithelial cells restored a good portion of the lungs expansion abilities.

Lead author, Dr. N. Valerio Dorrello, gave a big picture perspective on how this proof-of-concept study could one day help those who suffer from lung disease:

Nicolino Valerio Dorrello, MD

“Every day, I see children in intensive care with severe lung disease who depend on mechanical ventilation support. The approach we established could lead to entirely new treatment modalities for these patients, designed to regenerate lungs by treating their injured epithelium.”

Stem cell stories that caught our eye: relief for jaw pain, vitamins for iPSCs and Alzheimer’s insights

Jaw bone stem cells may offer relief for suffers of painful joint disorder
An estimated 10 million people in the US – mostly women –  suffer from problems with their temporomandibular joint (TMJ) which sits between the jaw bone and skull. TMJ disorders can lead to a number of symptoms such as intense pain in the jaw, face and head; difficulty swallowing and talking; and dizziness.

ds00355_im00012_mcdc7_tmj_jpgThe TMJ is made up of fibrocartilage which, when healthy, acts as a cushion to enable a person to move their jaw smoothly. But this cartilage doesn’t have the capacity to heal or regenerate so treatments including surgery and pain killers only mask the symptoms without fixing the underlying damage of the joint.

Reporting this week in Nature Communications, researchers at Columbia University’s College of Dental Medicine identified stem cells within the TMJ that can form cartilage and bone – in cell culture studies as well as in animals. The research team further showed that the signaling activity of a protein called Wnt leads to a reduction of these fibrocartilage stem cells (FSCSs) in animals and as a result causes deterioration of cartilage. But injecting a known inhibitor of Wnt into the animals’ damaged TMJ spurred growth and healing of the joint.

The team is now in search of other Wnt inhibitors that could be used in a clinical setting. In a university press release, Jeremy Mao, a co-author on the paper, talked about the implications of these results:

“They suggest that molecular signals that govern stem cells may have therapeutic applications for cartilage and bone regeneration. Cartilage and certain bone defects are notoriously difficult to heal.”

Take your vitamins: good advice for people and iPS cells
From a young age, we’re repeatedly told how getting enough vitamins each day is important for a healthy life. Our bodies don’t produce these naturally occurring chemicals but they carry out critical biochemical activities to keep our cells and organs functioning properly.

800px-carrots

Carrots: a great source of vitamin A. Image source: Wikimedia Commons

Well, it turns out that vitamins are also an important ingredient in stem cell research labs. Results published the Proceedings of the National Academy of Sciences (PNAS) this week by scientists in the UK and New Zealand show that vitamin A and C work together synergistically to improve the efficiency of reprogramming adult cells, like skin or blood, into the embryonic stem cell-like state of induced pluripotent stem cells (iPSCs).

By the time a stem cell has specialized into, let’s say, a skin cell, only skin cell-specific genes are active while others genes, like those needed for liver function, are shut down. Those non-skin genes are silenced through the attachment of chemical tags on the DNA, a process called methylation. It essentially provides the DNA with the means of maintaining a skin cell “memory”. To convert a skin cell back into a stem cell-like state, researchers in the lab must erase this “memory” by adding factors which demethylate, or remove the methylation tags on the silenced, non-skin related genes.

In the current research picked up by Science Daily, the researchers found that both vitamin A and C increase demethylation but in different ways. The study showed that vitamin A acts to increase the production of proteins that are important for demethylation while vitamin C acts to enhance the enzymatic activity of demethylation.

These insights may help add to the growing knowledge on how to most efficiently reprogram adult cells into iPSCs. And they may prove useful for a better understanding of certain cancers which contain cells that are essentially reprogrammed into a stem cell-like state.

New angles for dealing with the tangles in the Alzheimer’s brain
The memory loss and overall degradation of brain function seen in people with Alzheimer’s Disease (AD) is thought to be caused by the accumulation of amyloid and tau proteins which form plaques and tangles in the brain. These abnormal structures are toxic to brain cells and ultimately lead to cell death.

But other studies of post-mortem AD brains suggest a malfunction in endocytosis – a process of taking up and transporting proteins to different parts of the cell – may also play a role. While follow up studies corroborated this initial observation, they didn’t look at endocytosis in nerve cells so it remained unclear how much of a role it played in AD.

In a CIRM-funded study published this week in Cell Reports, UC San Diego researchers made nerve cells from human iPSCs and used the popular CRISPR and TALEN gene editing techniques to generate mutations seen in inherited forms of AD. One of those inherited mutations is in the PS1 gene which has been shown to play a role in transporting amyloid proteins in nerve cells. The research confirmed that this mutation as well as a mutation in the amyloid precursor protein (APP) led to a breakdown in the proper trafficking of APP within the mutated nerve cells. In fact, they found an accumulation of APP in a wrong area of the nerve cell. However, blocking the action of a protein called secretase that normally processes the APP protein helped restore proper protein transport. In a university press release, team leader Larry Goldstein, explained the importance of these findings:

goldsteinphoto2014cr

Larry Goldstein.
Image: UCSD

“Our results further illuminate the complex processes involved in the degradation and decline of neurons, which is, of course, the essential characteristic and cause of AD. But beyond that, they point to a new target and therapy for a condition that currently has no proven treatment or cure.”