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New injection technique may boost spinal cord injury repair efforts — ScienceDaily

Writing in the journal Stem Cells Translational Medicine, an international research team, led by physician-scientists at University of California San Diego School of Medicine, describe a new method for delivering neural precursor cells (NSCs) to spinal cord injuries in rats, reducing the risk of further injury and boosting the propagation of potentially reparative cells.

The findings are published in the Jan. 29, 2020 print issue.

NSCs hold great potential for treating a variety of neurodegenerative diseases and injuries to the spinal cord. The stem cells possess the ability to differentiate into multiple types of neural cell, depending upon their environment. As a result, there is great interest and much effort to use these cells to repair spinal cord injuries and effectively restore related functions.

But current spinal cell delivery techniques, said Martin Marsala, MD, professor in the Department of Anesthesiology at UC San Diego School of Medicine, involve direct needle injection into the spinal parenchyma — the primary cord of nerve fibers running through the vertebral column. “As such, there is an inherent risk of (further) spinal tissue injury or intraparechymal bleeding,” said Marsala.

The new technique is less invasive, depositing injected cells into the spinal subpial space — a space between the pial membrane and the superficial layers of the spinal cord.

“This injection technique allows the delivery of high cell numbers from a single injection,” said Marsala. “Cells with proliferative properties, such as glial progenitors, then migrate into the spinal parenchyma and populate over time in multiple spinal segments as well as the brain stem. Injected cells acquire the functional properties consistent with surrounding host cells.”

Marsala, senior author Joseph Ciacci, MD, a neurosurgeon at UC San Diego Health, and colleagues suggest that subpially-injected cells are likely to accelerate and improve treatment potency in cell-replacement therapies for several spinal neurodegenerative disorders in which a broad repopulation by glial cells, such as oligodendrocytes or astrocytes, is desired.

“This may include spinal traumatic injury, amyotrophic lateral sclerosis and multiple sclerosis,” said Ciacci.

The researchers plan to test the cell delivery system in larger preclinical animal models of spinal traumatic injury that more closely mimic human anatomy and size. “The goal is to define the optimal cell dosing and timing of cell delivery after spinal injury, which is associated with the best treatment effect,” said Marsala.

Co-authors include: Kota Kamizato and Takahiro Tadokoro, UC San Diego and University of Ryukyus, Japan; Michael Navarro and Silvia Marsala, UC San Diego; Stefan Juhas, Jana Juhasova, Hana Studenovska and Vladimir Proks, Czech Academy of Sciences; Tom Hazel and Karl Johe, Neuralstem, Inc.; and Shawn Driscoll, Thomas Glenn and Samuel Pfaff, Salk Institute.

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Materials provided by University of California – San Diego. Original written by Scott LaFee. Note: Content may be edited for style and length.

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Egg stem cells do not exist, new study shows — ScienceDaily

Researchers at Karolinska Institutet in Sweden have analysed all cell types in the human ovary and found that the hotly debated so-called egg stem cells do not exist. The results, published in Nature Communications, open the way for research on improved methods of treating involuntary childlessness.

The researchers used single-cell analysis to study more than 24,000 cells collected from ovarian cortex samples of 21 patients. They also analysed cells collected from the ovarian medulla, allowing them to present a complete cell map of the human ovary.

One of the aims of the study was to establish the existence or non-existence of egg stem cells.

“The question is controversial since some research has reported that such cells do exist, while other studies indicate the opposite,” says Fredrik Lanner, researcher in obstetrics and gynaecology at the Department of Clinical Science, Intervention and Technology at Karolinska Institutet, and one of the study’s authors.

The question of whether egg stem cells exist affects issues related to fertility treatment, since stem cells have properties that differ from other cells.

“Involuntary childlessness and female fertility are huge fields of research,” says co-author Pauliina Damdimopoulou, researcher in obstetrics and gynaecology at the same department. “This has been a controversial issue involving the testing of experimental fertility treatments.”

The new study substantiates previously reported findings from animal studies — that egg stem cells do not exist. Instead, these are so-called perivascular cells.

The new comprehensive map of ovarian cells can contribute to the development of improved methods of treating female infertility, says Damdimopoulou.

“The lack of knowledge about what a normal ovary looks like has held back developments,” she says. “This study now lays the ground on which to produce new methods that focus on the egg cells that already exist in the ovary. This could involve letting egg cells mature in test tubes or perhaps developing artificial ovaries in a lab.”

The results of the new study show that the main cell types in the ovary are egg cells, granulosa cells, immune cells, endothelial cells, perivascular cells and stromal cells.

The study was financed with the support of several bodies, including the Swedish Research Council, the Swedish Childhood Cancer Foundation, Horizon2020 (FREIA project), the Ragnar Söderberg Foundation, the Ming Wai Lau Centre for Reparative Medicine, the Centre for Innovative Medicine and Wallenberg Academy Fellows.

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Cells carrying Parkinson’s mutation could lead to new model for studying disease — ScienceDaily

Parkinson’s disease researchers have used gene-editing tools to introduce the disorder’s most common genetic mutation into marmoset monkey stem cells and to successfully tamp down cellular chemistry that often goes awry in Parkinson’s patients.

The edited cells are a step toward studying the degenerative neurological disorder in a primate model, which has proven elusive. Parkinson’s, which affects more than 10 million people worldwide, progressively degrades the nervous system, causing characteristic tremors, dangerous loss of muscle control, cardiac and gastrointestinal dysfunction and other issues.

“We know now how to insert a single mutation, a point mutation, into the marmoset stem cell,” says Marina Emborg, professor of medical physics and leader of University of Wisconsin-Madison scientists who published their findings Feb. 26 in the journal Scientific Reports. “This is an exquisite model of Parkinson’s. For testing therapies, this is the perfect platform.”

The researchers used a version of the gene-editing technology CRISPR to change a single nucleotide — one molecule among more than 2.8 billion pairs of them found in a common marmoset’s DNA — in the cells’ genetic code and give them a mutation called G2019S.

In human Parkinson’s patients, the mutation causes abnormal over-activity of an enzyme, a kinase called LRRK2, involved in a cell’s metabolism. Other gene-editing studies have employed methods in which the cells produced both normal and mutated enzymes at the same time. The new study is the first to result in cells that make only enzymes with the G2019S mutation, which makes it easier to study what role this mutation plays in the disease.

“The metabolism inside our stem cells with the mutation was not as efficient as a normal cell, just as we see in Parkinson’s,” says Emborg, whose work is supported by the National Institutes of Health. “Our cells had a shorter life in a dish. And when they were exposed to oxidative stress, they were less resilient to that.”

The mutated cells shared another shortcoming of Parkinson’s: lackluster connections to other cells. Stem cells are an especially powerful research tool because they can develop into many different types of cells found throughout the body. When the researchers spurred their mutated stem cells to differentiate into neurons, they developed fewer branches to connect and communicate with neighboring neurons.

“We can see the impact of these mutations on the cells in the dish, and that gives us a glimpse of what we could see if we used the same genetic principles to introduce the mutation into a marmoset,” says Jenna Kropp Schmidt, a Wisconsin National Primate Research Center scientist and co-author of the study. “A precisely genetically-modified monkey would allow us to monitor disease progression and test new therapeutics to affect the course of the disease.”

The concept has applications in research beyond Parkinson’s.

“We can use some of the same genetic techniques and apply it to create other primate models of human diseases,” Schmidt says.

The researchers also used marmoset stem cells to test a genetic treatment for Parkinson’s. They shortened part of a gene to block LRRK2 production, which made positive changes in cellular metabolism.

“We found no differences in viability between the cells with the truncated kinase and normal cells, which is a big thing. And when we made neurons from these cells, we actually found an increased number of branches,” Emborg says. “This kinase gene target is a good candidate to explore as a potential Parkinson’s therapy.”

This research was supported by grants from the National Institutes of Health (R24OD019803, P51OD011106 and UL1TR000427).

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Materials provided by University of Wisconsin-Madison. Original written by Chris Barncard. Note: Content may be edited for style and length.

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Inhalation therapy shows promise against pulmonary fibrosis in mice, rats — ScienceDaily

A new study from North Carolina State University shows that lung stem cell secretions — specifically exosomes and secretomes — delivered via nebulizer, can help repair lung injuries due to multiple types of pulmonary fibrosis in mice and rats. The work could lead to more effective, less invasive treatment for human pulmonary fibrosis sufferers.

Pulmonary fibrosis is a fatal disease that thickens and scars healthy lung tissue, creating inflammation and replacing the lining of the lung cells with fibrotic tissue. In the last five years, Ke Cheng and his lab developed spheroid-produced lung stem cells (LSCs) as a potential therapeutic for pulmonary fibrosis. Cheng is the Randall B. Terry Jr. Distinguished Professor in Regenerative Medicine at NC State, a professor in the NC State/UNC-Chapel Hill Joint Department of Biomedical Engineering, and corresponding author of the research.

“The mixture of cells in LSCs recreates the stem cells’ natural microenvironment — known as the stem cell niche — where cells secrete exosomes to communicate with each other just as they would inside your body,” Cheng says. “LSCs secrete many beneficial proteins and growth factors known collectively as ‘secretome’ — exosomes and soluble proteins which can reproduce the regenerative microenvironment of the cells themselves. In this work we took it one step further and tested the secretome and exosomes from our spheroid-produced stem cells against two models of pulmonary fibrosis.”

Cheng and his colleagues tested lung spheroid cell secretome (LSC-Sec) and lung spheroid cell exosomes (LSC-Exo) against commonly used mesenchymal stem cells (MSCs) in mouse and rat models of chemically induced and silica- or particle-induced pulmonary fibrosis. The stem cell-derived therapeutics were delivered through a “stem cell sauna,” a nebulizer that allowed the therapeutic proteins, small molecules and exosomes to be inhaled directly into the lungs.

In the mouse model of chemically induced fibrosis, the researchers found that although inhalation treatment with either LSC-Sec or MSC-Sec led to improvements compared to the saline-treated control, LSC-Sec treatment resulted in nearly 50% reduction of fibrosis compared to 32.4% reduction with MSC-Sec treatment.

In the mouse model of silica-induced pulmonary fibrosis, LSC-Sec treatment resulted in 26% reduction of fibrosis compared to 16.9% reduction with MSC-Sec treatment.

The researchers also looked at rat models of both types of pulmonary fibrosis, and tested both LSC-exosome and LSC-Sec treatments against MSC-Exo with similar results. Additionally, they found that while LSC-exosome inhalation treatment alone can elicit a therapeutic effect similar to LSC-Sec treatment, the full secretome was still the most therapeutic.

“This work shows that lung spheroid cell secretome and exosomes are more effective than their mesenchymal stem cells counterparts in decreasing fibrotic tissue and inflammation in damaged lung tissue,” Cheng says. “Hopefully we are taking our first steps toward an efficient, non-invasive and cost-effective way to repair damaged lungs.

“Given the therapy’s effectiveness in multiple models of lung fibrosis and inflammation, we are planning to expand the test into more pulmonary diseases, including chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS), and pulmonary hypertension (PH).”

“The finding that products released by lung stem cells can be just as efficacious, if not more so, than the stem cells themselves in treating pulmonary fibrosis can be a major finding that can have implications in many other diseases where stem cell therapy is being developed,” says Kenneth Adler, Alumni Distinguished Graduate Professor at NC State and a co-author of the paper.

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A molecular atlas of skin cells — ScienceDaily

Our skin protects us from physical injury, radiation and microbes, and at the same time produces hair and facilitates perspiration. Details of how skin cells manage such disparate tasks have so far remained elusive. Now, researchers at Karolinska Institutet in Sweden have systematically mapped skin cells and their genetic programs, creating a detailed molecular atlas of the skin in its complexity. The study is published today in the scientific journal Cell Stem Cell.

Mammalian skin has several important tasks to perform. It provides a waterproof protective barrier against the outside world, produces hair and harbours sweat glands. This tissue complexity requires many types of cells, such as fibroblasts, immune cells, nerve cells and pigment cells. To systematically study the skin, researchers at Karolinska Institutet have mapped the genes that are active in thousands of individual cells using a technique called single-cell RNA sequencing. Examining tissue from the skin and its hair-producing hair follicles at different stages of hair growth, the researchers uncovered how cells are coordinated during the phases of hair growth and rest.

“We found over 50 different kinds of cells in the skin, including new variations of cell types that have not been described before,” says Maria Kasper, research group leader at the Department of Biosciences and Nutrition, Karolinska Institutet. “We’ve also seen that most types of skin cells are affected by different phases of hair growth.”

As part of the study, the researchers described exactly where in the skin these cells are located and which genes they express. The authors have made this information available in an open-access online atlas, which helps others interested in specific genes to quickly find out if and where they are expressed. Conversely, researchers interested in specific cells can find out how gene expression changes during their task specification. The researchers behind this atlas believe that this information will be useful to other scientists studying for example skin diseases, wound healing or skin cancer.

By using their own atlas the authors have made several discoveries. For example, they have found that the outermost layer of the hair follicle consists of several types of cells organised in a specific way. They could also see how the hair progenitors, a type of stem cell that has started its specialisation towards specific hair follicle parts, goes through different molecular stages.

“This gives us vital knowledge on the flexibility of the skin, what the skin does to maintain its function and structure in different situations,” says Simon Joost, first author and recent graduate from Maria Kasper’s research group. “This knowledge may help us understand the flexibility of other organs, how they renew themselves and respond to different needs.”

The study was financed with grants from the Swedish Research Council, the Swedish Cancer Society, the Swedish Foundation for Strategic Research, the Ragnar Söderberg Foundation, the LEO Foundation, the Center for Innovative Medicine (CIMED), the Göran Gustafsson Foundation, the Wenner-Gren Foundation and Karolinska Institutet PhD (KID) funding.

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Molecular motors direct the fate of stem cells — ScienceDaily

Scientists at the University of Groningen and the University Medical Center Groningen used molecular motors to manipulate the protein matrix on which bone marrow-derived mesenchymal stem cells are grown. Rotating motors altered the protein structure, which resulted in a bias of the stem cells to differentiate into bone cells (osteoblasts). Without rotation, the stem cells tended to remain multipotent. These results, which could be used in tissue engineering, were published in Science Advances on 29 January.

‘Cells are sensitive to the structure of the surface that they attach to,’ explains Patrick van Rijn, associate professor in Materiobiology and Nanobiomaterials. ‘And movement is an important driver in biology, especially continuous movement.’ That is why Van Rijn and Feringa and their colleagues decided to use molecular motors to manipulate the protein matrix on which stem cells are grown. The light-driven motor molecules were designed by the 2016 Nobel Laureate in Chemistry Ben Feringa.

Structural changes

The scientists linked molecular motors to a glass surface. Subsequently, the surface was coated with protein and either exposed to UV irradiation to power the motors or not exposed to it at all. After about an hour, the motor movement was stopped and cells were seeded onto the protein layer and left to attach. Finally, differentiation factors were added. These experiments showed that cells grown on protein that was submitted to the rotary motion of the molecular motors tended to specialize into bone cells more often, while cells seeded on protein that was not disturbed were more inclined to maintain their stem-cell properties.

Observations of the protein layer using atomic force microscopy and simulations of the interaction between the motor molecules and proteins, performed by Prof. Marrink’s research group, showed that the movement induced subtle structural changes in the protein matrix. ‘The movement of motor molecules interferes with the alpha-helices in the proteins, which causes structural changes,’ explains Van Rijn. He compares it to the difference in texture between an unwhipped egg white and a whipped one.

Cell fate

The change in the surface structure of the adhered protein affects how the cells attach, for example how much they stretch out. This sets off a signaling cascade that eventually leads to altered behavior, such as the differentiation into bone cells. Thus, molecular movement leads to nanoscopic changes in surface structure, which in turn leads to differences in cell attachment, cell morphology and eventually, cell differentiation. ‘It’s like a domino effect, where smaller stones consecutively topple slightly larger ones so that a large effect can be achieved with a small trigger.’

‘Changing the properties of a surface to affect cell fate has been used before,’ says Van Rijn. However, this was done primarily with switches, so there was just a change from one state to another. ‘In our study, we had continuous movement, which is much more in line with the continuous motion found in biological transport and communication systems. The fact that the motors are driven by light is important,’ Van Rijn adds. ‘Light can be carefully controlled in space and time. This would allow us to create complex geometries in the growth matrix, which then result in different properties for the cells.’ Therefore, light-controlled molecular motors could be a useful tool in tissue engineering.

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Bone or cartilage? Presence of fatty acids determines skeletal stem cell development — ScienceDaily

In the event of a bone fracture, fatty acids in our blood signal to stem cells that they have to develop into bone-forming cells. If there are no blood vessels nearby, the stem cells end up forming cartilage. The finding that specific nutrients directly influence the development of stem cells opens new avenues for stem cell research. Biomedical scientists from KU Leuven and Harvard University published these results in Nature.

Bone fractures heal through the action of skeletal progenitor cells: stem cells that have evolved further but can still develop into different types of cells. Bone healing occurs in one of two ways: the progenitor cells evolve into bone-forming cells when the fracture is small, and into cartilage cells when the fracture is bigger. This cartilage is later replaced by bone. Until now, scientists did not know how progenitor cells decide whether to become bone or cartilage cells.

“Our hypothesis was that the presence of blood vessels plays a role,” explains first author Nick van Gastel. “Despite what many people think, our bones are full of blood vessels, while cartilage does not have any.” This new study on mice confirmed the team’s assumption: when blood vessels surrounding a fracture were blocked, cartilage was formed. When they were not, new bone was created immediately.

In a second phase of the study, the researchers tried to find out which signal the blood vessels actually send to the progenitor cells to make them evolve into either a bone or a cartilage cell. “Our previous research had already shown that nutrients play a role in the biology of progenitor cells,” explains Professor Geert Carmeliet from the Clinical and Experimental Endocrinology Unit at KU Leuven, who led the study. For the current study, the team tested how the presence of different nutrients influences progenitor cell fate. Their results show that the fatty acids present in blood cause progenitor cells to grow into bone-forming cells.

If there are no fatty acids nearby, progenitor cells activate the SOX9 gene, which plays an important role in skeletal development. This is the signal for the cell to become a cartilage cell. Cartilage cells do not need fatty acids to survive and form cartilage.

“This study is useful for researchers in regenerative medicine, since we still know little about cartilage formation,” says Professor Carmeliet. “Research into cartilage disorders such as osteoarthritis may also benefit from these findings. There are indications that cartilage cells receive more fatty acid signals and don’t produce enough of the SOX9 gene in patients with such disorders, which can have adverse effects on the joints. Finally, our study shows for the first time that specific nutrients can inform stem cells which type of cell they should become. That is an important step forward in stem cell research.” Eventually, the researchers hope to map out the effects of different nutrients on different types of progenitor cells.

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Scientists boost gene-editing tools to new heights in human stem cells — ScienceDaily

During the past decade, the gene editing tool CRISPR has transformed biology and opened up hopeful avenues to correct deadly inherited diseases. Last fall, scientists began the first human clinical trials using CRISPR to combat diseases like cancer. They remove some of a person’s cells, CRISPR edit the DNA, and then inject the cells back in, where hopefully, they will cure the disease.

But along with this promise of regenerative, personalized medicine, CRISPR can also have significant safety limitations. CRISPR may not edit in the right place (so-called off-target gene effects) or not being terribly efficient (successful editing may only be achieved in about 10% of the time for every available cell target).

These limitations have frustrated scientists such as Arizona State University’s David Brafman, a cell bioengineer. Brafman initial hopes are to use gene editing to get at the heart of uncovering the causes of studies in his lab of neurodegenerative diseases like Alzheimer’s.

“We study neurodegenerative diseases like Alzheimer’s and use stem cells to study specific mutations or risk factors associated with Alzheimer’s disease,” said Brafman, a biomedical engineering faculty member in ASU’s Ira A. Fulton Schools of Engineering. “We are not necessarily a gene-editing tool development lab, but we were running into difficulty generating stem cell lines by using a traditional CRISPR-based editing approach. For reasons that are still unknown, stem cells are really resistant to that sort of genetic modification.”

Green light means go

Now, Brafman, using a new update to the CRISPR base editing technology originally developed in the lab of David Liu at Harvard, has vastly outperformed previous efforts by making highly accurate, single DNA base editing with an efficiency of up to 90% of human stem cells. The results were published in the journal Stem Cell Reports.

“Previously, with CRISPR, it’s just been a random guess,” said Brafman. “And so, if you are picking at random stem cells and the efficiency is low, you’ll likely get only 10% or 5% because you have no idea if the edits have been made — the cell isn’t telling you.”

Brafman’s lab has developed a new TREE method (an acronym short for transient reporter for editing enrichment, or TREE), which allows for bulk enrichment of DNA base-edited cell populations — -and for the first time, high efficiency in human stem cell lines.

“”Most of the studies are done in immortalized cell lines or cancer cell lines, which are relatively easy to edit,” said Brafman. “This is the first example of using base editors in pluripotent stem cells, which is a very valuable cell population to genetically modify. We envision this method will have important implications for the use of human stem cell lines in developmental biology, disease modeling, drug screening and tissue engineering applications,”

Last year, they had shown that their TREE approach can work in human cell lines, but wanted to further push the technology further to find a way to rapidly and efficiently edit human stem cell lines.

Unlike CRISPR, which cuts across both DNA stands, their TREE method only makes a single strand nick in DNA. For example, when a single DNA base is successfully edited from a C to a T, a protein gives off a signal, turning from blue to green.

“Now, if a cell is telling you, ‘if I’m glowing green I have a 90% chance of being edited you are going to have better luck identifying edited populations,” said Brafman. “Then, you can exclude all of the cells that are not edited. We isolate single cells that are glowing green, then grow those up into clonal populations that you are able to expand indefinitely.”

Targeting Alzheimer’s

Pluripotent stem cells are valued for regenerative medicine because they have the ability to become or differentiate into any cell type in the human body.

Brafman explains that there are two general sources, “embryonic stem cells, which are derived from the inner cell mass of a preimplantation blastocyst, and then there are induced pluripotent stem cells, which are derived from taking somatic cells like skin or blood from patients.”

Brafman’s lab uses the induced pluripotent stem cells for their research.

“For this study, we used pluripotent stem cells from both healthy patients and then patients with Alzheimer’s disease. Some of the genes that we were interested in modulating are related to Alzheimer’s disease. The majority of the patients suffering from Alzheimer’s disease suffer from late onset, or sporadic Alzheimer’s disease.”

To provide their proof-of-concept, they targeted the APOE gene, which can come in three flavors. One of the three gene variants, called APOE4, has been associated with a higher risk for late onset Alzheimer’s disease. For the study, they introduced single DNA based edits into the APOE gene.

“That’s why we are interested in having these cells,” said Brafman. “They are representative of the neurons and the various cell types in the central nervous system with patients with these various risk factors. Then, we can understand why an APOE variant can increase or decrease risk, and then we can start targeting those pathways that are affected.”

Not only could TREE make single DNA edits to the APOE4 gene, but unlike CRISPR, make highly accurate corrections to both copies of the APOE4 gene that humans possess.

“The traditional CRISPR approach is that you have to edit once to get a heterozygous edit , then isolate that clone, edit again to get another heterozygous edit,” said Brafman. “So, it’s very inefficient in that way. We are generating homozygous edits at an efficiency approaching 90%. I haven’t seen any other technologies that can do that in pluripotent stem cells.”

In addition, TREE could also be used to engineer critical gene knockout mutations into stem cell lines. “The most fundamental experiment you can do if a gene has important implications in disease, development or physiology is knock it out,” said Brafman. That opens up a whole bunch of questions that we can address. Using APOE as a case study, now we can knock out APOE in these cells if you don’t have APOE at all. Is it beneficial? Detrimental? Or no difference?”

Complex cases

While diseases like sickle-cell anemia or cystric fibrosis are caused by single mutations in DNA, for most diseases and leading causes of death, like heart disease or high blood pressure, are complex, and involve multiple genes. Brafman wanted to also address the complex, root causes of Alzheimer’s.

“Especially as it related to Alzheimer’s disease, there can be multiple risk factors that act in concert, so we wanted a way to introduce multiple edits simultaneously in pluripotent stem cells. Because otherwise, you would have to take this sequential iterative approach, where you introduce one edit, isolate a clonal population introduce another edit, and so on.

They successfully demonstrated that TREE could be used to make new stem cell lines that had been simultaneously edited at multiple gene locations. Their results showed that more than 80% of stem clones had been targeted at all three different gene sites, and with all clones editing both gene copies.

“We found that if you multiplex you still get the same efficiency of editing as you would if you just edited a single allele,” said Brafman. “Now, we can use these cells as in vitro models to study the disease and screen drugs.”

Brafman is hopeful that their new tools will generate excitement in the gene editing community, and spur others on to make new discoveries.

“We want to keep expanding on that toolbox,” said Brafman. “We’ve already gotten a high level of interest from other scientists who will be using this to generate their own cell lines. That’s a good thing.”

Funding for this work was provided by the National Institutes of Health (R01GM121698 to David Brafman, R21AG056706 to D.A.B, R01GM106081 to X.W.) and the Arizona Biomedical Research Commission (ADHS16-162401 to D.A.B).

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New hydrogels wither while stem cells flourish for tissue repair — ScienceDaily

Baby diapers, contact lenses and gelatin dessert. While seemingly unrelated, these items have one thing in common — they’re made of highly absorbent substances called hydrogels that have versatile applications. Recently, a type of biodegradable hydrogel, dubbed microporous annealed particle (MAP) hydrogel, has gained much attention for its potential to deliver stem cells for body tissue repair. But it is currently unclear how these jelly-like materials affect the growth of their precious cellular cargo, thereby limiting its use in regenerative medicine.

In a new study published in the November issue of Acta Biomaterialia, researchers at Texas A&M University have shown that MAP hydrogels, programmed to biodegrade at an optimum pace, create a fertile environment for bone stem cells to thrive and proliferate vigorously. They found the space created by the withering of MAP hydrogels creates room for the stem cells to grow, spread and form intricate cellular networks.

“Our research now shows that stem cells flourish on degrading MAP hydrogels; they also remodel their local environment to better suit their needs,” said Dr. Daniel Alge, assistant professor in the Department of Biomedical Engineering. “These results have important implications for developing MAP hydrogel-based delivery systems, particularly for regenerative medicine where we want to deliver cells that will replace damaged tissues with new and healthy ones.”

MAP hydrogels are a newer breed of injectable hydrogels. These soft materials are interconnected chains of extremely small beads made of polyethylene glycol, a synthetic polymer. Although the microbeads cannot themselves cling to cells, they can be engineered to present cell-binding proteins that can then attach to receptor molecules on the stem cells’ surface.

Once fastened onto the microbeads, the stem cells use the space between the spheres to grow and transform into specialized cells, like bone or skin cells. And so, when there is an injury, MAP hydrogels can be used to deliver these new cells to help tissues regenerate.

However, the health and behavior of stem cells within the MAP hydrogel environment has never been fully studied.

“MAP hydrogels have superior mechanical and biocompatible properties, so in principle, they are a great platform to grow and maintain stem cells,” said Alge. “But people in the field really don’t have a good understanding of how stem cells behave in these materials.”

To address this question, the researchers studied the growth, spread and function of bone stem cells in MAP hydrogels. Alge and his team used three samples of MAP hydrogels that differed only in the speed at which they degraded, that is, either slow, fast or not at all.

First, for the stem cells to attach onto the MAP hydrogels, the researchers decorated the MAP hydrogels with a type of cell-binding protein. They then tracked the stem cells as they grew using a high-resolution, fluorescent microscope. The researchers also repeated the same experiment using another cell-binding protein to investigate if cell-binding proteins also affected stem cell development within the hydrogels.

To their surprise, Alge’s team found that for both types of cell-binding proteins, the MAP hydrogels that degraded the fastest had the largest population of stem cells. Furthermore, the cells were changing the shape of the MAP hydrogel as they spread and claimed more territory.

“In the intact MAP hydrogel, we could still see the spherical microbeads and the material was quite undamaged,” said Alge. “By contrast, the cells were making ridges and grooves in the degrading MAP hydrogels, dynamically remodeling their environment.”

The researchers also found that as the stem cells grew, the quantity of bone proteins produced by the growing stem cells depended on which cell-binding protein was initially used in the MAP hydrogel.

Alge noted that the insight gained through their study will greatly inform further research and development in MAP hydrogels for stem-cell therapies.

“Although MAP hydrogel degradability profoundly affects the growth of the stem cells, we found that the interplay between the cell-binding proteins and the degradation is also important,” he said. “As we, as a field, make strides toward developing new MAP hydrogels for tissue engineering, we must look at the effects of both degradability and cell-binding proteins to best utilize these materials for regenerative medicine.”

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Scientists solve long-debated puzzle of how the intestine heals itself — ScienceDaily

Deep within the lining of the human intestine lies the source of the organ’s ability to renew itself and recover from damage: intestinal stem cells (ISCs), lodged in pockets of tissue called crypts, generate the cells that continuously repopulate the intestinal lining. Even the stem cells themselves have a safety net: when they’re damaged, healthy replacements appear in less than a week.

For years, scientists have debated how the ISCs’ re-emergence occurs. Some have held that the intestine keeps a pool of ISCs on reserve — a kind of backup-backup supply — to replenish the cache of front-line ISCs that have been lost. Others have maintained that something more involuted is as work: The ISCs, like queen bees, give rise to more specialized, or “differentiated,” progeny — in this case, daughter cells that form the inner lining of the intestine. When the ISCs are damaged, this school of thought held, the daughter cells reverse course and “de-differentiate” — reverting into the ISCs from which they arose.

A new study by Dana-Farber Cancer Institute scientists comes down solidly on the latter option. Published online today by the journal Cell Stem Cell, the researchers found that ISCs and their daughter cells have a strikingly reciprocal relationship: under normal conditions, ISCs differentiate into daughter cells, and, if the ISCs are lost, the daughter cells simply reverse course and become ISCs.

“Our findings suggest that the restoration of intestinal stem cells occurs entirely by the process of de-differentiation,” says the study’s senior author, Ramesh Shivdasani, MD, PhD, of Dana-Farber, Brigham and Women’s Hospital (BWH), and the Harvard Stem Cell Institute. “We showed there’s no need for a reserve set of ISCs.”

Bolstering their findings, the researchers were also able to capture the de-differentiation process in real time. When cells begin to de-differentiate, they switch on a gene that that allows them to be isolated and collected with laboratory techniques, Shivdasani explains. Through this process, researchers were able to capture the cells along a continuum of de-differentiation. Shivdasani likens it to a baseball play in which a runner is tagged out between first and second base.

Heavy turnover

The intestine is one of just three tissues in the body, along with the skin and blood, in which cells are constantly turning over — dying and being replaced by freshly made cells. They share this quality because they are the tissues most intimately in contact with material from the environment, and therefore with potentially harmful substances. The constant turnover, it’s thought, is a way to prevent toxic substances from having lasting effects on cells and their offspring.

The crypts that hold ISCs are, in a sense, misnamed. Far from being enclosures where dead cells are entombed, they are the sites where ISCs daily generate the billions of daughter cells that take the place of defunct intestinal cells.

One of the chief characteristics of ISCs is that they are extremely radiosensitive, or vulnerable to radiation. People exposed to high levels of radioactivity, in the form of nuclear fallout, for example, can suffer severe intestinal damage because the loss of ISCs halts production of cells to regenerate the damaged tissue. But if ISCs succumb easily to radiation, they also make a rapid return. Patients with radiation-induced intestinal damage who can be kept alive for a week often recover as their ISC levels bounce back.

To determine whether this rebound is due to a reserve stockpile of ISCs or to de-differentiation of daughter cells, Shivdasani and his collaborators performed a kind of time-lapse experiment. They treated a collection of ISC cells with the drug tamoxifen, which caused the cells and their offspring to become fluorescent. They waited 48 hours for the label to take hold, then killed the ISC cells. If the daughter cells were indeed de-differentiating, any ISC cells produced after that point would be fluorescent. That’s exactly what researchers found.

While scientists have been able to convert many kinds of differentiated cells into stem cells using laboratory techniques, Shivdasani and his colleagues’ discovery demonstrates that de-differentiation ismore than a curious act of nature; it is the principal means to restore damaged stem cell in the intestine. It’s not known whether cells in other organs and tissues have this capability, but it remains an open avenue of investigation.

“It also isn’t clear how the crypt knows that stem cells have died and need to be replaced,” Shivdasani remarks, “or how the daughter cells receive the signal to de-differentiate. This is a subject we’re currently exploring.”

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