Stem Cells Faulty in Duchenne Muscular Dystrophy

Stem Cells Faulty in Duchenne Muscular Dystrophy

Thursday, 18 December 2014

Like human patients, mice with a form of Duchenne muscular dystrophy undergo progressive muscle degeneration and accumulate connective tissue as they age. Now, researchers at the Stanford University School of Medicine have found that the fault may lie at least partly in the stem cells that surround the muscle fibres.

They've found that during the course of the disease, the stem cells become less able to make new muscle and instead begin to express genes involved in the formation of connective tissue. Excess connective tissue – a condition called fibrosis – can accumulate in many organs, including the lungs, liver and heart, in many different disorders. In the skeletal muscles of people with muscular dystrophy, the fibrotic tissue impairs the function of the muscle fibres and leads to increasing weakness and stiffness, which are hallmarks of the disease.

The researchers discovered that this abnormal change in stem cells could be inhibited in laboratory mice by giving the animals a drug that is already approved for use in humans. The drug works by blocking a signalling pathway involved in the development of fibrosis. Although much more research is needed, the scientists are hopeful that a similar approach may one day work in children with muscular dystrophy.

"These cells are losing their ability to produce muscle, and are beginning to look more like fibroblasts, which secrete connective tissue," said Thomas Rando, MD, PhD, professor of neurology and neurological sciences.

"It's possible that if we could prevent this transition in the muscle stem cells, we could slow or ameliorate the fibrosis seen in muscular dystrophy in humans."

A paper describing the researchers' findings will be published Dec. 17 in Science Translational Medicine. Rando, the paper's senior author, is director of the Glenn Laboratories for the Biology of Aging and founding director of the Muscular Dystrophy Association Clinic at Stanford. Former postdoctoral scholar Stefano Biressi, PhD, is the lead author. Biressi is now at the Centre for Integrative Biology at the University of Trento in Italy.

A devastating disease

Duchenne muscular dystrophy is a devastating disease that affects about 1 in every 3,600 boys born in the United States. Patients usually experience severe, progressive muscle weakness that confines them to a wheelchair in early adolescence and eventually leads to paralysis. It's caused by mutations in the dystrophin gene, which encodes the dystrophin protein. The dystrophin protein serves to connect muscle fibres to the surrounding external matrix. This connection stabilizes the fibres, enhancing their strength and preventing injury. Sufferers are nearly always boys because the dystrophin gene is located on the X chromosome. (Girls would need to inherit two faulty copies, which is unlikely because male carriers often die in early adulthood.)

Under normal conditions, muscle stem cells respond to muscle damage by dividing into cells, one of which becomes new muscle, while the other remains a stem cell. However, in the mice missing the dystrophin gene, the muscle stem cells slowly assume a different fate. They begin to resemble fibroblasts instead of muscle-making machines.

To conduct the research, Biressi and Rando used a strain of laboratory mice in which the muscle stem cells were engineered to glow with a fluorescent light when treated with a drug called tamoxifen. They then bred the mice with another strain in which the dystrophin gene is mutated, and followed the fate of the cells over time.

The researchers found that the expression of myogenic genes, which are associated with the regeneration of muscle in response to injury, was nearly completely lacking in many of the muscle stem cells in the mice after just 11 months, while the expression of fibrotic genes had increased compared with that of control animals. The cells from the dystrophic animals were also oddly located: Rather than being nestled next to the muscle fibres, they had begun to move away into the spaces between tissues.

The role of a signalling pathway

Rando and Biressi knew that a similar, but much less pronounced, accumulation of connective tissue in muscle fibres occurs during normal aging. That process is governed by signalling proteins, which include the Wnt and TGF-beta protein families. Wnt plays a critical role in embryonic development and cancer; TGF-beta controls cell division and specialization. They wondered whether blocking the Wnt/TGF-beta pathway in the dystrophic mice would inhibit fibrosis in the animals' muscles.

The researchers turned to a drug called losartan, which is used to treat high blood pressure. Losartan inhibits the expression of the genes for TGF-beta types 1 and 2. The researchers thought it would probably interrupt the signalling pathway that leads the muscle stem cells astray.

Treating the mice with losartan, they found, did in fact prevent the muscle stem cells from expressing fibrosis-associated genes and partially maintained their ability to form new muscle.

"This scar tissue, or fibrosis, leaves the muscle less elastic and impairs muscle function," Rando said.

"So we'd like to understand why it happens, and how to prevent it. It's also important to limit fibrosis to increase the likelihood of success with other possible therapies, such as cell therapy or gene therapy."

Next steps

Because TGF-beta type 1 plays many roles throughout the body, the researchers are now working to find ways to specifically inhibit TGF-beta type 2, which is involved in the transition of the muscle stem cells. They're also interested in learning how to translate the research to other diseases.

"Fibrosis seems to occur in a vicious cycle," Rando said.

"As the muscle stem cells become less able to regenerate new muscle, the tissue is less able to repair itself after damage. This leads to fibrosis, which then further impairs muscle formation. Understanding the biological basis of fibrosis could have a profound effect on many other diseases."

Source: Stanford University Medical Center

Contact: Krista Conger

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iPS Cells Used to Correct Genetic Mutations that Cause Muscular Dystrophy

iPS Cells Used to Correct Genetic Mutations that Cause Muscular Dystrophy

Thursday, 27 November 2014

This image shows immunofluorescence staining

of skeletal cells differentiated from DMD-iPS

cells. Untreated DMD skeletal cells do not

express dystrophin (green) due to the deletion of

exon 44. However, after any of the three

correction strategies are applied to iPS cells,

differentiation into skeletal cells results in normal

dystrophin expression. Scale bar, 50 μm.

Credit: Dr. Akitsu Hotta, Kyoto University.

Researchers at the Center for iPS Cell Research and Application (CiRA), Kyoto University, show that induced pluripotent stem (iPS) cells can be used to correct genetic mutations that cause Duchenne muscular dystrophy (DMD). The research, published in Stem Cell Reports, demonstrates how engineered nucleases, such as TALEN and CRISPR, can be used to edit the genome of iPS cells generated from the skin cells of a DMD patient. The cells were then differentiated into skeletal muscles, in which the mutation responsible for DMD had disappeared.

DMD is a severe muscular degenerative disease caused by a loss-of-function mutation in the dystrophin gene. It inflicts 1 in 3500 boys and normally leads to death by early adulthood. Currently, very little is available in terms of treatment for patients outside palliative care. One option gaining interest is genomic editing by TALEN and CRISPR, which have quickly become invaluable tools in molecular biology. These enzymes allow scientists to cleave genes at specific locations and then modify the remnants to produce a genomic sequence to their liking. However, programmable nucleases are not pristine and often mistakenly edit similar sequences that vary a few base pairs from the target sequence, making them unreliable for clinical use because of the potential for undesired mutations.

For this reason, induced pluripotent stem cells (iPS cells) are ideal models, because they provide researchers an abundance of patient cells on which to test the programmable nucleases and find optimal conditions that minimize off-target modifications. CiRA scientists took advantage of this feature by generating iPS cells from a DMD patient. They used several different TALEN and CRISPR to modify the genome of the iPS cells, which were then differentiated into skeletal muscle cells. In all cases, dystrophin protein expression was convalesced, and in some cases, the dystrophin gene was fully corrected.

One key to the success was the development of a computational protocol that minimized the risk of off-target editing. The team built a database that all possible permutations of sequences up to 16 base pairs long. Among these, they extracted those that only appear once in the human genome, i.e. unique sequences. DMD can be caused by several different mutations; in the case of the patient used in this study, it was the result of the deletion of exon 44. The researchers therefore built a histogram of unique sequences that appeared in a genomic region that contained this exon. They found a stack of unique sequences in exon 45.

to Akitsu Hotta, who headed the project and holds joint positions at CiRA and the Institute for Integrated Cell-Materials Sciences at Kyoto University:

"Nearly half the human genome consists of repeated sequences. So even if we found one unique sequence, a change of one or two base pairs may result in these other repeated sequences, which risks the TALEN or CRISPR editing an incorrect region. To avoid this problem, we sought a region that hit high in the histogram".

With this target, the team considered three strategies to modify the frame-shift mutation of the dystrophin gene: exon skipping by connecting exons 43 and 46 to restore the reading frame, frame shifting by incorporating insertion or deletion (indel) mutations, and exon knock-in by inserting exon 44 before exon 45. All three strategies effectively increased dystrophin synthesis in differentiated skeletal cells, but only the exon knock-in approach recovered the gene to its natural state. Importantly, editing showed very high specificity, suggesting that their computational approach can be used to minimize off-target editing by the programming nucleases.

Moreover, the paper provides a proof-of-principle for using iPS cell technology to treat DMD in combination with TALEN or CRISPR. The group now aims to expand this protocol to other diseases.

First author Lisa Li explains: "We show that TALEN and CRISPR can be used to correct the mutation of the DMD gene. I want to apply the nucleases to correct mutations for other genetic-based diseases like point mutations".

Source: Center for iPS Cell Research and Application - Kyoto University

Contact: Akemi Nakamura

Reference:

Precise correction of the DYSTROPHIN gene in Duchenne Muscular Dystrophy patient-derived iPS cells by TALEN and CRISPR-Cas9

Hongmei Lisa Li, Naoko Fujimoto, Noriko Sasakawa, Saya Shirai, Tokiko Ohkame, tetsushi Sakuma, Michihiro tanaka, Naoki Amano, Akira Watanabe, Hidetoshi Sakurai, Takashi Yamamoto, Shinya Yamanaka, and Akitsu Hotta

Stem Cell Reports, November 26, 2014, DOI: http://dx.doi.org/10.1016/j.stemcr.2014.10.013

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Cardiac Stem Cell Therapy may Heal Heart Damage Caused by Duchenne Muscular Dystrophy

Late-breaking basic science research presented at American Heart Association Scientific Sessions shows stem cell treatment restores heart function damaged by muscular disease

Tuesday, 18 November 2014

Researchers at the Cedars-Sinai Heart Institute have found that injections of cardiac stem cells might help reverse heart damage caused by Duchenne muscular dystrophy, potentially resulting in a longer life expectancy for patients with the chronic muscle-wasting disease.

The study results were presented today at a Breaking Basic Science presentation during the American Heart Association Scientific Sessions in Chicago. After laboratory mice with Duchenne muscular dystrophy were infused with cardiac stem cells, the mice showed steady, marked improvement in heart function and increased exercise capacity.

Duchenne muscular dystrophy, which affects 1 in 3,600 boys, is a neuromuscular disease caused by a shortage of a protein called dystrophin, leading to progressive muscle weakness. Most Duchenne patients lose their ability to walk by age 12. Average life expectancy is about 25. The cause of death often is heart failure because the dystrophin deficiency leads to cardiomyopathy, a weakness of the heart muscle that makes the heart less able to pump blood and maintain a regular rhythm.

"Most research into treatments for Duchenne muscular dystrophy patients has focused on the skeletal muscle aspects of the disease, but more often than not, the cause of death has been the heart failure that affects Duchenne patients," said Eduardo Marbán, MD, PhD, director of the Cedars-Sinai Heart Institute and study leader.

"Currently, there is no treatment to address the loss of functional heart muscle in these patients."

During the past five years, the Cedars-Sinai Heart Institute has become a world leader in studying the use of stem cells to regenerate heart muscle in patients who have had heart attacks. In 2009, Marbán and his team completed the world's first procedure in which a patient's own heart tissue was used to grow specialized heart stem cells. The specialized cells were then injected back into the patient's heart in an effort to repair and regrow healthy muscle in a heart that had been injured by a heart attack. Results, published in The Lancet in 2012, showed that one year after receiving the experimental stem cell treatment, heart attack patients demonstrated a significant reduction in the size of the scar left on the heart muscle.

Earlier this year, Heart Institute researchers began a new study, called ALLSTAR, in which heart attack patients are being infused with allogeneic stem cells, which are derived from donor-quality hearts.

Recently, the Heart Institute opened the nation's first Regenerative Medicine Clinic, designed to match heart and vascular disease patients with appropriate stem cell clinical trials being conducted at Cedars-Sinai and other institutions.

"We are committed to thoroughly investigating whether stem cells could repair heart damage caused by Duchenne muscular dystrophy," Marbán said.

In the study, 78 lab mice were injected with cardiac stem cells. Over the next three months, the lab mice demonstrated improved pumping ability and exercise capacity in addition to a reduction in heart inflammation. The researchers also discovered that the stem cells work indirectly, by secreting tiny fat droplets called exosomes. The exosomes, when purified and administered alone, reproduce the key benefits of the cardiac stem cells.

Marbán said the procedure could be ready for testing in human clinical studies as soon as next year. The process to grow cardiac-derived stem cells was developed by Marbán when he was on the faculty of Johns Hopkins University. Johns Hopkins has filed for a patent on that intellectual property and has licensed it to Capricor, a company in which Cedars-Sinai and Marbán have a financial interest. Capricor is providing funds for the ALLSTAR clinical trial at Cedars-Sinai.

The Cedars-Sinai Heart Institute has been at the forefront of developing investigational stem cell treatments for heart attack patients.

Source: Cedars-Sinai Medical Center

Contact: Sally Stewart

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A New Way to Make Muscle Cells from Human Stem Cells

A New Way to Make Muscle Cells from Human Stem Cells

Friday, 21 March 2014

Muscle cells are stained green in this micrograph

of cells grown from embryonic stem cells in the

lab of Masatoshi Suzuki at the University of

Wisconsin–Madison. Cell nuclei are stained blue;

the muscle fibres contain multiple nuclei. Nuclei

outside the green fibres are from non-muscle cells.

Suzuki has developed a new method of growing

stem cells into muscle cells that could be more

suitable for treating disease. Suzuki hopes to

experiment next with animals that model muscular

dystrophy and amyotrophic lateral sclerosis.

Credit: Masatoshi Suzuki. 

As stem cells continue their gradual transition from the lab to the clinic, a research group at the University of Wisconsin-Madison has discovered a new way to make large concentrations of skeletal muscle cells and muscle progenitors from human stem cells.

The new method, described in the journal Stem Cells Translational Medicine, could be used to generate large numbers of muscle cells and muscle progenitors directly from human pluripotent stem cells. These stem cells, such as embryonic (ES) or induced pluripotent stem (iPS) cells, can be made into virtually any adult cell in the body.

Adapting a method previously used to make brain cells, Masatoshi Suzuki, an assistant professor of comparative biosciences in the School of Veterinary Medicine, has directed those universal stem cells to become both adult muscle cells and muscle progenitors.

Importantly, the new technique grows the pluripotent stem cells as floating spheres in high concentrations of two growth factors, fibroblast growth factor-2 and epidermal growth factor. These growth factors "urge" the stem cells to become muscle cells.

"Researchers have been looking for an easy way to efficiently differentiate stem cells into muscle cells that would be allowable in the clinic," says Suzuki. The novelty of this technique is that it generates a larger number of muscle stem cells without using genetic modification, which is required by existing methods for making muscle cells.

"Many other protocols have been used to enhance the number of cells that go to a muscle fate," says co-author Jonathan Van Dyke, a post-doctoral fellow in Suzuki's laboratory.

"But what's exciting about the new protocol is that we avoid some techniques that would prohibit clinical applications. We think this new method has great promise for alleviating human suffering."

Last year, Suzuki demonstrated that transplants of another type of human stem cells somewhat improved survival and muscle function in rats that model amyotrophic lateral sclerosis (ALS). Also known as Lou Gehrig's disease, ALS destroys nerves and causes a loss of muscle control. The muscle progenitors generated with Suzuki's new method could potentially play a similar role but with enhanced effect.

The new technique can also be used to grow muscle cells from iPS cells from patients with neuromuscular diseases like ALS, spinal muscular atrophy and muscular dystrophy. Thus, the technique could produce adult muscle cells in a dish that carry genetic diseases. These cells could then be used as a tool for studying these diseases and screening potential drug compounds, says Suzuki.

"Our protocol can work in multiple ways and so we hope to provide a resource for people who are exploring specific neuromuscular diseases in the laboratory."

The new protocol incorporates a number of advantages. First, the cells are grown in defined supplements without animal products such as bovine serum, enhancing the clinical safety for the muscle stem cells. Second, when grown as spheres, the cells grow faster than with previous techniques. Third, 40 to 60 percent of the cells grown using the process are either muscle cells or muscle progenitors, a high proportion compared to traditional non-genetic techniques of generating muscle cells from human ES and iPS cells.

Suzuki and his group hope that by further manipulating the chemical environment of the spheres of stem cells, they may increase that number, further easing the path toward human treatment.

Source: University of Wisconsin-Madison 

Contact: Masatoshi Suzuki

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Successful Regeneration of Human Skeletal Muscle in Mice Enables Accelerated Research in Muscular Dystrophy

Kennedy Krieger researchers develop valid and accurate model for FSHD

Tuesday, 28 January 2014

Researchers at the Kennedy Krieger Institute recently announced study findings showing the successful development of a humanized preclinical model for facioscapulohumeral muscular dystrophy (FSHD), providing scientists with a much needed tool to accelerate novel therapeutic research and development.

Published in Human Molecular Genetics, the study outlines the validity of a unique model that, for the first time, mirrors the gene expression and biomarker profile of human FSHD tissue. Previously, there has been no accepted preclinical model for FSHD, a complex and rare neuromuscular disorder that affects approximately 4 - 7 per 100,000 individuals. As a result, therapeutic development for the disorder has been stymied.

“The inability to mimic the FSHD’s genetic mechanism in preclinical models has been an ongoing challenge for the research community. Without an accurate model, making the leap to clinical research commonly fails,” said Kathryn Wagner MD, PhD, director of the Center for Genetic Muscle Disorders at the Kennedy Krieger Institute in Baltimore, MD.

“We believe this unique model will open the door to studying muscle regeneration over time and help better predict clinical response to therapeutic drugs.”

Inspired by cancer preclinical models developed with human tumour tissue, Dr. Wagner and her research team leveraged both basic science and clinical research resources available at Kennedy Krieger to successfully regenerate grafted muscle within the models. Human bicep muscle biopsies transplanted into models survived for over 41 weeks and retained features of normal and diseased tissue.

“This model is not only applicable to genetic muscle diseases for which we lack appropriate research models, but for other acquired muscle conditions,” said Wagner.

“Now there will be more research possibilities related to the overall impact of age and disease on the regenerative and growth capacity of human skeletal muscle.”

Source: Kennedy Krieger Institute 

Contact: Jennifer Burke

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Human Muscle Stem Cell Therapy Gets Help from Zebrafish

HSCI researchers improve therapy prospects

Thursday, 07 November 2013

Zebrafish in Research Lab for Animal Testing.

Harvard Stem Cell scientists have discovered that the same chemicals that stimulate muscle development in zebrafish can also be used to differentiate human stem cells into muscle cells in the laboratory, a historically challenging task that, now overcome, makes muscle cell therapy a more realistic clinical possibility.

The work, published this week in the journal Cell, began with a discovery by Boston Children's Hospital researchers, led by Leonard Zon, MD, and graduate student Cong (Tony) Xu, who tested 2,400 different chemicals in cultures of zebrafish embryo cells to determine if any could increase the numbers of muscle cells formed. Using fluorescent reporter fish in which muscle cells were visible during their creation, the researchers found six chemicals that were very effective at promoting muscle formation.

Zon shared his results with Harvard Department of Stem Cell and Regenerative Biology professor Amy Wagers, PhD, and Mohammadsharif Tabebordbar, a graduate student in her laboratory, who tested the six chemicals in mice. One of the six, called forskolin, was found to increase the numbers of muscle stem cells from mice that could be obtained when these cells were grown in laboratory dishes. Moreover, the cultured cells successfully integrated into muscle when transplanted back into mice.

Inspired by the successful application of these chemicals in mice, Salvatore Iovino, PhD, a joint postdoctoral fellow in the Wagers lab and the lab of C. Ronald Kahn, MD, at the Joslin Diabetes Center, investigated whether the chemicals would also affect human cells and found that a combination of three chemicals, including forskolin, could induce differentiation of human induced pluripotent stem (iPS) cells, made by reprogramming skin cells. Exposure of iPS cells to these chemicals converted them into skeletal muscle, an outcome the Wagers and Kahn labs had been striving to achieve for years using conventional methods. When transplanted into a mouse, the human iPS-derived muscle cells also contributed to muscle repair, offering early promise that this protocol could provide a route to muscle stem cell therapy in humans.

The interdisciplinary, cross-laboratory collaboration between Zon, Wagers, and Kahn highlights the advantage of open exchange between researchers.

"If we had done this screen directly on human iPS cells, it would have taken at least 10 times as long and cost 100 times as much," said Wagers.

"The zebrafish gave us a big advantage here because it has a fast generation time, rapid development, and can be easily and relatively cheaply screened in a culture dish."

"This research demonstrates that over 300 million years of evolution, the pathways used in the fish are conserved through vertebrates all the way up to the human," said Wagers' fellow HSCRB professor Leonard Zon, chair of the Harvard Stem Cell Institute Executive Committee and director of the stem cell program at Boston Children's Hospital.

"We can now make enough human muscle progenitors in a dish to allow us to model diseases of the muscle lineage, like Duchenne muscular dystrophy, conduct drug screens to find chemicals that correct that disease, and in the long term, efficiently transplant muscle stem cells into a patient."

In a similar biomedical application, Kahn, who is chief academic officer at the Joslin, plans to apply the new ability to quickly produce muscle stem cells for diabetes research. His lab will generate iPS-derived muscle cells from people who are at risk for diabetes and people who have diabetes to identify alterations that lead to insulin resistance in the muscle.

Going forward, Zon plans to apply this platform of cross-species discovery to other stem cell lines, including those involved in blood and eye development.

"We have a new system to use to study tissue development, and it's not just muscle that can be studied, every single organ can be studied in the zebrafish system," he said.

Source: Harvard University 

Contact: B. D. Colen

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Stem-cell Approach Shows Promise for Duchenne Muscular Dystrophy

Stem-cell Approach Shows Promise for Duchenne Muscular Dystrophy

Monday, 14 January 2013

Researchers have shown that transplanting stem cells derived from normal mouse blood vessels into the hearts of mice that model the pathology associated with Duchenne muscular dystrophy (DMD) prevents the decrease in heart function associated with DMD.

University of Illinois comparative biosciences 

professor Suzanne Berry-Miller, veterinary 

clinical medicine professor Robert O’Brien 

and their colleagues developed a method 

that enhanced cardiac function in a mouse

model of Duchenne muscular dystrophy. 

Credit: L. Brian Stauffer. 

Their findings appear in the journal Stem Cells Translational Medicine.

Duchenne muscular dystrophy is a genetic disorder caused by a mutation in the gene for dystrophin, a protein that anchors muscle cells in place when they contract. Without dystrophin, muscle contractions tear cell membranes, leading to cell death. The lost muscle cells must be regenerated, but in time, scar tissue replaces the muscle cells, causing the muscle weakness and heart problems typical of DMD.

The U.S. Centers for Disease Control and Prevention estimates that DMD affects one in every 3,500 males. The disease is more prevalent in males because the dystrophin mutation occurs on the X chromosome; males have one X and one Y chromosome, so a male with this mutation will have DMD, while females have two X chromosomes and must have the mutation on both of them to have the disease. Females with the mutation in one X chromosome sometimes develop muscle weakness and heart problems as well, and may pass the mutation on to their children.

Although medical advances have extended the lifespans of DMD patients from their teens or 20s into their early 30s, disease-related damage to the heart and diaphragm still limits their lifespan.

"Almost 100 percent of patients develop dilated cardiomyopathy," in which a weakened heart with enlarged chambers prevents blood from being properly pumped throughout the body, said University of Illinois comparative biosciences professor Suzanne Berry-Miller, who led the study.

"Right now, doctors are treating the symptoms of this heart problem by giving patients drugs to try to prolong heart function, but that can't replace the lost or damaged cells," she said.

Treatment with stem cells derived from 

blood vessels spurred nestin-positive 

stem cells already present in the heart 

to form new cardiac muscle cells (see 

arrows). Credit: Suzanne Berry-Miller. 

In the new study, the researchers injected stem cells known as aorta-derived mesoangioblasts (ADM) into the hearts of dystrophin-deficient mice that serve as a model for human DMD. The ADM stem cells have a working copy of the dystrophin gene.

This stem cell therapy prevented or delayed heart problems in mice that did not already show signs of the functional or structural defects typical of Duchenne muscular dystrophy, the researchers report.

Berry-Miller and her colleagues do not yet know why the functional benefits occur, but proposed three potential mechanisms. They observed that some of the injected stem cells became new heart muscle cells that expressed the lacking dystrophin protein. The treatment also caused existing stem cells in the heart to divide and become new heart muscle cells, and the stem cells stimulated new blood vessel formation in the heart. It is not yet clear which of these effects is responsible for delaying the onset of cardiomyopathy, Berry-Miller said.

"These vessel-derived cells might be good candidates for therapy, but the more important thing is the results give us new potential therapeutic targets to study, which may be activated directly without the use of cells that are injected into the patient, such as the ADM in the current study," Berry-Miller said.

"Activating stem cells that are already present in the body to repair tissue would avoid the potential requirement to find a match between donors and recipients and potential rejection of the stem cells by the patients."

After injecting dystrophin-deficient mouse hearts

with normal, blood-vessel-derived stem cells,

researchers saw an increase in cell division among

nestin-positive stem cells (shown in green) in the heart.

These stem cells are found in the hearts of adult

humans, rats, and mice, but their function is not yet

known. An increase in formation of new heart muscle

cells from the nestin-positive stem cells was also

detected. Credit: Suzanne Berry-Miller. 

Despite the encouraging results that show that stem cells yield a functional benefit when administered before pathology arises in DMD mouse hearts, a decline in function was seen in mice that already showed the characteristics of dilated cardiomyopathy. One of these characteristics is the replacement of muscle tissue with connective tissue, known as fibrosis.

This difference may occur, Berry-Miller said, as a result of stem cells landing in a pocket of fibrosis rather than in muscle tissue. The stem cells may then become fibroblasts that generate more connective tissue, increasing the amount of scarring and making heart function worse. This shows that the timing of stem cell insertion plays a crucial role in an increase in heart function in mice lacking the dystrophin protein.

She remains optimistic that these results provide a stepping-stone toward new clinical targets for human DMD patients.

"This is the only study so far where a functional benefit has been observed from stem cells in the dystrophin-deficient heart, or where endogenous stem cells in the heart have been observed to produce new muscle cells that replace those lost in DMD, so I think it opens up a new area to focus on in pre-clinical studies for DMD," Berry-Miller said.

Source: University of Illinois at Urbana-Champaign 

Contact: Diana Yates

Reference:

Injection of vessel derived stem cells-prevent dilated cardiomyopathy and promote angiogenesis and endogenous cardiac stem cell proliferation in mdx/utrn-/-but not aged mdx mouse models for Duchenne muscular dystrophy

Ju Lan Chun, Robert O'Brien, Min Ho Song, Blake F. Wondrasch and Suzanne E. Berry

Stem Cells Trans Med, December 27, 2012, doi:10.5966/sctm.2012-0107

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Advance Understanding of Spinal Muscular Atrophy with Stem Cells

Cedars-Sinai's Regenerative Medicine Institute research sheds new light on cell death in a common, lethal genetic disease in children, suggesting paths for potential treatment
Thursday, 21 June 2012 

Cedars-Sinai's Regenerative Medicine Institute has pioneered research on how motor-neuron cell-death occurs in patients with spinal muscular atrophy, offering an important clue in identifying potential medicines to treat this leading genetic cause of death in infants and toddlers.

The study, published in the June 19 online issue of PLoS ONE, extends the institute's work to employ pluripotent stem cells to find a pharmaceutical treatment for spinal muscular atrophy or SMA, a genetic neuromuscular disease characterized by muscle atrophy and weakness.

"With this new understanding of how motor neurons die in spinal muscular atrophy patients, we are an important step closer to identifying drugs that may reverse or prevent that process," said Clive Svendsen, PhD, director of the Cedars-Sinai Regenerative Medicine Institute.

Svendsen and his team have investigated this disease for some time now. In 2009, Nature published a study by Svendsen and his colleagues detailing how skin cells taken from a patient with the disorder were used to generate neurons of the same genetic makeup and characteristics of those affected in the disorder; this created a "disease-in-a-dish" that could serve as a model for discovering new drugs.

As the disease is unique to humans, previous methods to employ this approach had been unreliable in predicting how it occurs in humans. In the research published in PLoS ONE, to the team reproduced this model with skin cells from multiple patients, taking them back in time to a pluripotent stem cell state (iPS cells), and then driving them forward to study the diseased patient-specific motor neurons.

Children born with this disorder have a genetic mutation that doesn't allow their motor neurons to manufacture a critical protein necessary for them to survive. The study found these cells die through apoptosis – the same form of cell death that occurs when the body eliminates old, unnecessary as well as unhealthy cells. As motor neuron cell death progresses, children with the disease experience increasing paralysis and eventually death. There is no effective treatment now for this disease. An estimated one in 35 to one in 60 people are carriers and about in 100,000 new-borns have the condition.

"Now we are taking these motor neurons (from multiple children with the disease and in their pluripotent state) and screening compounds that can rescue these cells and create the protein necessary for them to survive," said Dhruv Sareen, director of Cedars-Sinai's Induced Pluripotent Stem Cell Core Facility and a primary author on the study.

"This study is an important stepping stone to guide us toward the right kinds of compounds that we hope will be effective in the model – and then be reproduced in clinical trials."

Source: Cedars-Sinai Medical Center 

Contact: Nicole White

Reference:

Inhibition of Apoptosis Blocks Human Motor Neuron Cell Death in a Stem Cell Model of Spinal Muscular Atrophy

Dhruv Sareen, Allison D. Ebert, Brittany M. Heins, Jered V. McGivern, Loren Ornelas, Clive N. Svendsen

PLoS ONE, 19 Jun, 2012, 201210.1371/journal.pone

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Researchers Develop New Muscular Dystrophy Treatment Approach Using Human Stem Cells

Researchers Develop New Muscular Dystrophy Treatment Approach Using Human Stem Cells

Saturday, 05 May 2012

Researchers from the University of Minnesota's Lillehei Heart Institute have effectively treated muscular dystrophy in mice using human stem cells derived from a new process that – for the first time – makes the production of human muscle cells from stem cells efficient and effective.

The research, published today in Cell Stem Cell, outlines the strategy for the development of a rapidly dividing population of skeletal myogenic progenitor cells (muscle-forming cells) derived from induced pluripotent (iPS) cells. iPS cells have all of the potential of embryonic stem (ES) cells, but are derived by reprogramming skin cells. They can be patient-specific, which renders them unlikely to be rejected, and do not involve the destruction of embryos.

This is the first time that human stem cells have been shown to be effective in the treatment of muscular dystrophy.

According to U of M researchers – who were also the first to use ES cells from mice to treat muscular dystrophy – there has been a significant lag in translating studies using mouse stem cells into therapeutically relevant studies involving human stem cells. This lag has dramatically limited the development of cell therapies or clinical trials for human patients.

The latest research from the U of M provides the proof-of-principle for treating muscular dystrophy with human iPS cells, setting the stage for future human clinical trials.

"One of the biggest barriers to the development of cell-based therapies for neuromuscular disorders like muscular dystrophy has been obtaining sufficient muscle progenitor cells to produce a therapeutically effective response," said principal investigator Rita Perlingeiro, Ph.D., associate professor of medicine in the Medical School's Division of Cardiology.

"Up until now, deriving engraftable skeletal muscle stem cells from human pluripotent stem cells hasn't been possible. Our results demonstrate that it is indeed possible and sets the stage for the development of a clinically meaningful treatment approach."

Upon transplantation into mice suffering from muscular dystrophy, human skeletal myogenic progenitor cells provided both extensive and long-term muscle regeneration which resulted in improved muscle function.

To achieve their results, U of M researchers genetically modified two well-characterized human iPS cell lines and an existing human ES cell line with the PAX7 gene. This allowed them to regulate levels of the Pax7 protein, which is essential for the regeneration of skeletal muscle tissue after damage. The researchers found this regulation could prompt naïve ES and iPS cells to differentiate into muscle-forming cells.

Up until this point, researchers had struggled to make muscle efficiently from ES and iPS cells. PAX7 – induced at exactly the right time – helped determine the fate of human ES and iPS cells, pushing them into becoming human muscle progenitor cells.

Once Dr. Perlingeiro's team was able to pinpoint the optimal timing of differentiation, the cells were well suited to the regrowth needed to treat conditions such as muscular dystrophy. In fact, Pax7-induced muscle progenitors were far more effective than human myoblasts at improving muscle function. Myoblasts, which are cell cultures derived from adult muscle biopsies, had previously been tested in clinical trials for muscular dystrophy, however the myoblasts did not persist after transplantation.

"Seeing long-term maintenance of these cells without major adverse side effects is exciting," said Perlingeiro.

"Our research proves that these differentiated stem cells have real staying power in the fight against muscular dystrophy."

According to John Wagner, M.D., scientific director of clinical research at the University's Stem Cell Institute and renowned blood and marrow transplant expert,

"This research is a phenomenal breakthrough. Dr. Perlingeiro and her collaborators have overcome one of the most significant obstacles to moving stem cell therapies into the treatment of children with devastating and life threatening muscular dystrophies."

The U of M researchers say alternative methods of Pax7 induction will need to be investigated before this study can be turned into a human clinical trial. Their method of delivering the Pax7 protein involved genetic modification of cells with viruses and because viruses sometimes cause mutations, they add risk to a clinical trial. But the U of M researchers are committed to developing a safe and effective clinical protocol, and are actively testing alternate methods of delivering Pax7.

Source: University of Minnesota Academic Health Center 

Contact: Caroline Marin

Reference:

Human ES- and iPS-Derived Myogenic Progenitors Restore DYSTROPHIN and Improve Contractility upon Transplantation in Dystrophic Mice

Radbod Darabi, Robert W. Arpke, Stefan Irion, John T. Dimos, Marica Grskovic, Michael Kyba, Rita C.R. Perlingeiro

Cell Stem Cell, Volume 10, Issue 5, 610-619, 4 May 2012, 10.1016/j.stem.2012.02.015

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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Next-generation DNA Sequencing to Improve Diagnosis for Muscular Dystrophy

Next-generation DNA Sequencing to Improve Diagnosis for Muscular Dystrophy
Tuesday, 06 March 2012

Scientists at The University of Nottingham have used a revolutionary new DNA-reading technology for a research project that could lead to correct genetic diagnosis for muscle-wasting diseases.

The technique could be used to offer people with muscular dystrophy, or a related neuromuscular condition, a more accurate prognosis, which would enable them to make more informed choices on life decisions, including family planning.

The researchers used a next-generation DNA sequencing machine to investigate the condition of a patient who had previously been misdiagnosed with the wrong type of muscular dystrophy.

The research, led by Professor Jane Hewitt in the University's School of Biology, was funded by the Muscular Dystrophy Campaign through a PhD studentship for Andreas Leidenroth.

Andreas said:

"Our case study demonstrates how genetic diagnostics will be done in the future. New DNA sequencing machines will be cheap to run, easy to use, fit on a desk and decode an entire human genome in minutes. High-throughput DNA sequencing in the NHS is no longer a question of 'if', but of 'when'. The biggest challenge will be to develop standardized filtering guidelines so that we can easily extract medically relevant information from these large DNA datasets."

The study, published in the European Journal of Human Genetics, focused on a person who had previously been diagnosed with facioscapulohumeral muscular dystrophy (FSHD) — a type of muscular dystrophy that predominantly affects muscles of the face, shoulder and upper arm. However, when the researchers studied her DNA more closely they found several inconsistencies and realized that she was highly unlikely to have FSHD.

To gain a genetic diagnosis for this, traditionally genes known to be involved in muscular dystrophies would have to be tested one by one, which can be a laborious and time consuming process. This would also have limited the search to a small number of genes and risked missing the mutation.

Instead, the Nottingham team used whole genome sequencing which, rather than reading the code of a single gene at a time, can simultaneously decipher the more than 25,000 genes of the human genome. This had the advantage of almost guaranteeing to examine the mutated gene but also poses a serious challenge: human DNA can vary from one person to the next so how could they tell which was a harmful genetic mutation rather than a harmless 'spelling difference' unique to that person?

The Nottingham researchers used different data filters to carefully narrow them down. First they ignored all spelling differences that had already been reported in the genomes of healthy people, assuming them to be harmless. This left 950 differences, of which 450 looked like they might be harmful mutations. When they compared this shortlist to 30 known muscular dystrophy genes, they found two matches: the patient had two mutations in a gene known to cause limb-girdle muscular dystrophy (LGMD) type 2A, correcting the genetic diagnosis of this patient.

Due to the complexities of these diseases, more than 20 per cent of all people with muscular dystrophy or a related neuromuscular condition are currently living without a genetic diagnosis, leaving around 10,000 people in the UK without accurate information about how their condition will progress. Treatments are on the horizon for many of these conditions and to access these patients will need an accurate diagnosis.

The study demonstrates the power of next generation sequencing as a diagnostic tool. While health services like the NHS are likely to adopt similar technologies in the near future, these methods are still rapidly evolving and research-based case studies such as this one will provide important guidance for other researchers and prove the feasibility of these methods.

Dr Marita Pohlschmidt, Director of Research at the Muscular Dystrophy Campaign said:

"Diagnosing neuromuscular disorders can be extremely difficult — there are currently thousands of people in the UK living in a state of limbo with no definite answers about their condition. Not only is it psychologically difficult but it can have real consequences upon people's lives, making decisions about treatment options and having children much harder. This research is extremely promising and will bring hope to many families."

The Nottingham researchers worked on the DNA sequencing in collaboration with colleagues at the Norwegian High-Throughput Sequencing Centre in Oslo, which was enabled by a Nottingham Robert's Money Building Experience and Skills Travel Scholarship (BESTS).

Source: University of Nottingham

Contact: Emma Thorne

Reference:

Diagnosis by sequencing: correction of misdiagnosis from FSHD2 to LGMD2A by whole-exome analysis
Andreas Leidenroth, Hanne Sørmo Sorte, Gregor Gilfillan, Melanie Ehrlich, Robert Lyle and Jane E Hewitt
European Journal of Human Genetics, 29 February 2012; doi: 10.1038/ejhg.2012.42
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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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