brain cells

Study reveals new evidence of key mechanism in Alzheimer’s

/ Esteban Cortez / 1 Comment

In California, 690,000 people aged 65 and older are living with Alzheimer’s, a degenerative brain disease and the most common form of dementia. In the United States, 5.8 million people aged 65 and older live with Alzheimer’s disease. Alzheimer’s affects memory, thinking and behavior and symptoms eventually grow in severity to interfere with daily tasks.  

There is no cure for Alzheimer’s, which is why Rutgers scientists are examining human brain cells in mice to identify a pivotal mechanism that could result in a potential therapy for the disease. In a recent study, the Rutgers team found more clear-cut evidence of how the destructive proteins linked to Alzheimer’s disease attack human brain cells and destroy surrounding tissue. 

The researchers studied human brain immune cells injected into the brains of specially bred immunodeficient mice, creating what they called a human-mouse chimera. The researchers detailed what happened to specialized immune brain cells known as microglia after those cells were exposed to tau proteins—destructive substances believed to be involved in Alzheimer’s and other severe human brain diseases. 

“This provided an unprecedented opportunity to investigate the role of human microglia in brains as well as the cognitive impairment seen in Alzheimer’s Disease and Down syndrome, a genetic disorder with a high risk of developing Alzheimer’s disease,” said Peng Jiang, an associate professor in the Department of Cell Biology and Neuroscience at the Rutgers School of Arts and Sciences. 

By studying the process in the newly-developed brain—which allowed human cells to grow, develop and mature with appropriate functions—the scientists were able to witness and analyze a cellular brain attack that has been largely elusive up to this point. 

In autopsies, scientists have been able to study the brains of people who died from Alzheimer’s and have seen residues of tau proteins and cellular changes. The human-mouse brain chimera has allowed the Rutgers team to extract and see human cells in the actual process of deterioration. 

The mice in the study were specially bred to be immunodeficient so that they could receive implanted human cells without rejecting them due to normal immune defenses.  The immunodeficient mice were injected with human microglial cells and, later, with tau proteins, which are linked to the development of the brain disease. 

“Since microglial cells are one of the first cell responders when something goes wrong in the brain, we believe the changes we saw to be significant,” said Mengmeng Jin, a postdoctoral researcher in the Department of Cell Biology and Neuroscience at Rutgers and first author on the study. 

The California Institute for Regenerative Medicine (CIRM) is committed to investing at least $1.5 billion—more than double what CIRM funded between 2006 and 2020—in treatments that target conditions affecting the brain and central nervous system (CNS), including Alzheimer’s. 

Read the source release about the study here.  

Teaching stem cells to play video games

/ Kevin McCormack / Leave a comment

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video games atari pong
Pong video game

Back when I was growing up, shortly after the extinction of the dinosaurs, there was a popular video game called Pong. It was, in fact, pretty much the only video game at the time. It was a pretty simple game. You moved a “paddle” to hit a ball and knock it back across the screen to your opponent. If your opponent missed it you won the point. It was a really simplified form of video ping pong (hence the name). 

So why am I telling you this? Well, researchers in the UK and Australia have devised a way of teaching blobs of brain cells how to play Pong. I kid you not. 

Playing Pong

What they did was turn stem cells into brain cells, as part of a system called Dishbrain. Using software, they helped these neurons or brain cells communicate with each other through electrical stimulation and recordings. 

In an article in Newsweek, (yup, Newsweek is still around) the researchers explained that using these electrical signals they could help the cells identify where the “ball” was. For example, if the signals came from the left that meant the “ball” was on the right. 

In the study they say: “Using this DishBrain system, we have demonstrated that a single layer of in vitro (in a dish) cortical neurons can self-organize and display intelligent and sentient behavior when embodied in a simulated game-world.” We have shown that even without a substantial filtering of cellular activity, statistically robust differences over time and against controls could be observed in the behavior of neuronal cultures in adapting to goal directed tasks.”

Now you might think this was just something the researchers dreamed up to pass time during COVID, but they say understanding how these brain cells can learn and respond could help them develop other methods of using neurons that might be even cooler than playing video games. 

The study is published in the journal BioRXiv

Heads or tails? Stem cells help guide the decision

/ Kevin McCormack / 1 Comment
Two cell embryo

There are many unknown elements for what triggers the cells in an embryo to start dividing and multiplying and becoming every single cell in the body. Now researchers at the Gladstone Institutes in San Francisco have uncovered one of those elements, how embryos determine which cells become the head and which the tail.

In this CIRM-funded study the Gladstone team, led by Dr. Todd McDevitt, discovered almost by chance how the cells align in a heads-to-tail arrangement.

Todd McDevitt

They had created an organoid made from brain cells when they noticed that some of the cells were beginning to gather in an elongated fashion, in the same way that spinal cords do in a developing fetus.

In a news article, Nick Elder, a graduate student at Gladstone and the co-author of the study, published in the journal Development, says this was not what they had anticipated would happen: “Organoids don’t typically have head-tail directionality, and we didn’t originally set out to create an elongating organoid, so the fact that we saw this at all was very surprising.”

Further study enabled the team to identify which molecules were involved in signaling specific genes to switch on and off. These were similar to the process previously identified in developing mouse embryos.

“This is such a critical point in the early development of any organism, so having a new model to observe it and study it in the lab is very exciting,” says McDevitt.

This is not just of academic interest either, it could have real world implications in helping understand what causes miscarriages or birth defects.

“We can use this organoid to get at unresolved human developmental questions in a way that doesn’t involve human embryos,” says Dr. Ashley Libby, another member of the team. “For instance, you could add chemicals or toxins that a pregnant woman might be exposed to, and see how they affect the development of the spinal cord.”

Using biological “codes” to generate neurons in a dish

/ Pallavi Penumetcha / Leave a comment

BrainWavesInvestigators at the Scripps Research Institute are making brain waves in the field of neuroscience. Until now, neuroscience research has largely relied on a variety of animal models to understand the complexities of various brain or neuronal diseases. While beneficial for many reasons, animal models do not always allow scientists to understand the precise mechanism of neuronal dysfunction, and studies done in animals can often be difficult to translate to humans. The work done by Kristin Baldwin’s group, however, is revolutionizing this field by trying to re-create this complexity in a dish.

One of the primary hurdles that scientists have had to overcome in studying neuronal diseases, is the impressive diversity of neuronal cell types that exist. The exact number of neuronal subtypes is unknown, but scientists estimate the number to be in the hundreds.

While neurons have many similarities, such as the ability to receive and send information via chemical cues, they are also distinctly specialized. For example, some neurons are involved in sensing the external environment, whereas others may be involved in helping our muscles move. Effective medical treatment for neuronal diseases is contingent on scientists being able to understand how and why specific neuronal subtypes do not function properly.

In a study in the journal Nature, partially funded by CIRM, the scientists used pairs of transcription factors (proteins that affect gene expression and cell identity), to turn skin stem cells into neurons. These cells both physically looked like neurons and exhibited characteristic neuronal properties, such as action potential generation (the ability to conduct electrical impulses). Surprisingly, the team also found that they were able to generate neurons that had unique and specialized features based on the transcription factors pairs used.

The ability to create neuronal diversity using this method indicates that this protocol could be used to recapitulate neuronal diversity outside of the body. In a press release, Dr. Baldwin states:

KristinBaldwin

Kristin Baldwin, PhD

“Now we can be better genome detectives. Building up a database of these codes [transcription factors] and the types of neurons they produce can help us directly link genomic studies of human brain disease to a molecular understanding of what goes wrong with neurons, which is the key to finding and targeting treatments.”

These findings provide an exciting and promising tool to more effectively study the complexities of neuronal disease. The investigators of this study have made their results available on a free platform called BioGPS in the hopes that multiple labs will delve into the wealth of information they have opened up. Hopefully, this system will lead to more rapid drug discovery for disease like autism and Alzheimer’s

Scientist grow diseased brain cells in bulk to study Alzheimer’s and Parkinson’s disease

/ Karen Ring / Leave a comment

Daily trips to the local grocery store have become a thing of the past for many with the rise of wholesale stores like Costco and online giants like Amazon. Buying in bulk is attractive for people who lead busy lives, have large families, or just love having endless pairs of clean socks.

Scientists who study neurodegenerative diseases like Alzheimer’s and Parkinson’s use disease-in-a-dish models that are much like the daily visits to the nearby Safeway. They can make diseased brain cells, or neurons, from human pluripotent stem cells and study them in the lab. But often, they can’t generate large enough quantities of cells to do important experiments like test new drugs or develop diagnostic platforms to identify disease at an earlier age.

What scientists need is a Costco for brain cells, a source that can make diseased brain cells in bulk. Such a method would open a new avenue of research into what causes neurodegeneration and how the aging process affects its progression.

This week, this need was answered. A team of researchers from Lund University in Sweden developed a method that can efficiently generate neurons from patients with a range of neurodegenerative diseases including Parkinson’s, Huntington’s and Alzheimer’s disease. The study was published in EMBO Molecular Medicine and was led by senior author Dr. Malin Parmar.

Diseased neurons made by the Lund University team. (Photo, Kennet Ruona)

Parmar and her team took an alternative approach to making their neurons. Their technology involves converting human skin cells into neurons without reprogramming the skin cells back to a pluripotent stem cell state first. This process is called “direct conversion” and is considered an effective shortcut for generating mature cells like neurons in a dish. Direct conversion of skin cells into neurons was first published by Dr. Marius Wernig, a CIRM-grantee and professor at Stanford University.

There is also scientific evidence suggesting that reprogramming patient cells back to a pluripotent state wipes out the effects of aging in those cells and has a Benjamin Button-like effect on the resulting neurons. By directly converting patient skin cells into neurons, many of these aging “signatures” are retained and the resulting neurons are more representative of the aging brain.

So how did they make brain cells in bulk? Parmar explained their method in a Lund University news release,

Malin Parmar

“Primarily, we inhibited a protein, REST, involved in establishing identity in cells that are not nerve cells. After limiting this protein’s impact in the cells during the conversion process, we’ve seen completely different results.”

 

Besides blocking REST, the team also turned on the production of two proteins, Ascl1 and Brn2, that are important for the development of neurons. This combination of activating pro-neural genes and silencing anti-neural genes was successful at converting skin cells into neurons on a large scale. Parmar further explained,

“We’ve been playing around with changing the dosage of the other components in the previous method, which also proved effective. Overall, the efficiency is remarkable. We can now generate almost unlimited amounts of neurons from one skin biopsy.”

As mentioned previously, this technology is valuable because it provides better brain disease models for scientists to study and to screen for new drugs that could treat or delay disease onset. Additionally, scientists can study the effects of the aging in the brain at different stages of neurodegeneration. Aging is a well-known risk factor for many neurodegenerative diseases, especially Alzheimer’s, so the ability to make large quantities of brain cells from elderly Alzheimer’s patients will unlock new clues into how age influences disease.

Co-author Dr. Johan Jakobsson concluded,

Johan Jakobsson

“This takes us one step closer to reality, as we can now look inside the human neurons and see what goes on inside the cell in these diseases. If all goes well, this could fundamentally change the field of research, as it helps us better understand the real mechanisms of the disease. We believe that many laboratories around the world would like to start testing on these cells to get closer to the diseases.”

For more on this study, check out this short video provided by Lund University.

New stem cell technique gives brain support cells a starring role

/ Kevin McCormack / 1 Comment

Gage et al

The Salk team. From left: Krishna Vadodaria, Lynne Moore, Carol Marchetto, Arianna Mei, Fred H. Gage, Callie Fredlender, Ruth Keithley, Ana Diniz Mendes. Photo courtesy Salk Institute

Astrocytes are some of the most common cells in the brain and central nervous system but they often get overlooked because they play a supporting role to the more glamorous neurons (even though they outnumber them around 50 to 1). But a new way of growing those astrocytes outside the brain could help pave the way for improved treatments for stroke, Alzheimer’s and other neurological problems.

Astrocytes – which get their name because of their star shape (Astron – Greek for “star” and “kyttaron” meaning cell) – have a number of key functions in the brain. They provide physical and metabolic support for neurons; they help supply energy and fuel to neurons; and they help with detoxification and injury repair, particularly in terms of reducing inflammation.

Studying these astrocytes in the lab has not been easy, however, because existing methods of producing them have been slow, cumbersome and not altogether effective at replicating their many functions.

Finding a better way

Now a team at the Salk Institute, led by CIRM-funded Professor Fred “Rusty” Gage, has developed a way of using stem cells to create astrocytes that is faster and more effective.

Their work is published in the journal Stem Cell Reports. In a news release, Gage says this is an important discovery:

“This work represents a big leap forward in our ability to model neurological disorders in a dish. Because inflammation is the common denominator in many brain disorders, better understanding astrocytes and their interactions with other cell types in the brain could provide important clues into what goes wrong in disease.”

Stylized microscopy image of an astrocyte (red) and neuron (green). (Salk Institute)

In a step by step process the Salk team used a series of chemicals, called growth factors, to help coax stem cells into becoming, first, generic brain cells, and ultimately astrocytes. These astrocytes not only behaved like the ones in our brain do, but they also have a particularly sensitive response to inflammation. This gives the team a powerful tool in helping develop new treatment to disorders of the brain.

But wait, there’s more!

As if that wasn’t enough, the researchers then used the same technique to create astrocytes from induced pluripotent stem cells (iPSCs) – adult cells, such as skin, that have been re-engineered to have the ability to turn into any other kind of cell in the body. Those man-made astrocytes also showed the same characteristics as natural ones do.

Krishna Vadodaria, one of the lead authors on the paper, says having these iPSC-created astrocytes gives them a completely new tool to help explore brain development and disease, and hopefully develop new treatments for those diseases.

“The exciting thing about using iPSCs is that if we get tissue samples from people with diseases like multiple sclerosis, Alzheimer’s or depression, we will be able to study how their astrocytes behave, and how they interact with neurons.”