Capricor Therapeutics Enrolls Patients in HOPE Clinical Trial


The Beverly Hills-based biotechnology company Capricor Therapeutics, Inc. (CAPR) has announced the enrollment of 25 patients for their randomized Phase 1/2 HOPE-Duchenne clinical trial.

“HOPE” stands for “Halt cardiomyOPathy progrEssion in Duchenne” Muscular Dystrophy. The HOPE trial will evaluate the company’s CAP-1002 investigational cardiac cell therapy in patients suffering from Duchenne muscular dystrophy (DMD)-associated cardiomyopathy. If all goes as planned, CAPR expects to the first data points from this trial in six months (first quarter of 2017).

DMD most seriously affects skeletal muscle, but the disease can also devastate heart muscle. In fact, the most common cause of death from DMD results from the consequences of the disease on heart muscle.

The HOPE trial will assess the safety and efficacy of CAP-1002 in these 25 patients.

In DMD patients, scar tissue gradually accumulates in the heart, which leads to a deterioration of cardiac function.

CAP-1002 consists of cells donated from the hearts of healthy volunteers. These “cardiosphere-derived cells” or CDCs, have been shown by work in the laboratory of Dr. Eduardo Marbán, Director of the Heart Institute at Cedars-Sinai Medical Center, to reduce scar tissue in damaged hearts and improve heart function in studies with laboratory animals. Furthermore, a clinical study with CDCs, the CADUCEUS study, showed that the reduction of heart scar tissue in patients given infusions of CDCs. Therefore CAD-1002 might be the only therapeutic agent that can potentially reduce scar tissue in the damaged heart.

The HOPE trial enrolled 25 boys with DMD who were at least 12 years of age at the time of screening and who show signs of DMD-associated cardiomyopathy. These boys all have significant scar tissue in at least four left ventricular segments, according to magnetic resonance imaging (MRI) scans.

Of these 25 subjects, 13 subjects were randomly assigned to receive CAP-1002 by means of intracoronary infusion into each of the three main coronary arteries in a single procedure.

The 12 subjects randomized to the control arm received usual care and received no such infusion.

Efficacy of CAD-1002 will be assessed by means of specified secondary outcome measures that include absolute and relative changes in cardiac scar tissue and cardiac function as measured by MRI, performance on the Six-Minute Walk Test (6MWT) and the Performance of the Upper Limb (PUL), and scoring on the Pediatric Quality of Life Inventory (PedsQL).

The HOPE trial is a multicenter study; it is being conducted at Cincinnati Children’s Hospital Medical Center in Cincinnati, Ohio, Cedars-Sinai Heart Institute in Los Angeles, Calif., and the University of Florida in Gainesville, Fla.

DMD is a genetically inherited condition. The dystrophin gene that is abnormal in DMD patients is on the X chromosome, and therefore, the vast majority of DMD patients are male. DMD afflicts approximately 20,000 boys and young men in the U.S. The dystrophin complex is a structural component of muscles, integral to the integrity of muscle fibers. Abnormalities in dystrophin leads to chronic skeletal and cardiac muscle damage.

Advertisements

AUF1 Gene Important Inducer of Muscle Repair


A new study in the laboratory of Robert J. Schneider at NYU Langone and his collaborators has uncovered a gene that plays integral roles in the repair of injured muscle throughout life. This investigation shows that this previously “overlooked” gene might play a pivotal role in “sarcopenia,” which refers to the loss of muscle tissues with age.

This collaboration between scientists at NYU Langone Medical Center and the University of Colorado at Boulder showed that the levels of a protein called AUF1 determine if stem cell populations retain the ability to regenerate muscle after injury and as mice age.

Changes in the activity of AUF1 have also been linked by past studies to human muscle diseases. More than 30 genetic diseases, known collectively as myopathies, show defective muscle regeneration and these anomalies cause muscles to weaken or waste away.

For example, muscular dystrophy is a disease in which abnormal muscles fail to function properly and undergo normal repair. Although the signs and symptoms of Duchenne Muscular Dystrophy vary, in some cases wildly, this disease develops in infants and affects and weakens the torso and limb muscles beginning in young adulthood. Sarcopenia, in healthy individuals occurs in older patients.

Skeletal muscles have a stem cell population set aside for muscle repair known as satellite cells. These cells divide and differentiate into skeletal muscle when skeletal muscle is damaged, and as we age, the capacity of muscle satellite cells to repair muscle decreases.

AUF1 is a protein that regulates muscle stem cell function by inducing the degradation of specific, targeted messenger RNAs (mRNAs). According to Robert Schneider, “This work places the origin of certain muscle diseases squarely within muscle stem cells, and shows that AUF1 is a vital controller of adult muscle stem cell fate.” He continued: “The stem cell supply is remarkably depleted when the AUF1 signal is defective, leaving muscles to deteriorate a little more each time repair fails after injury.”

The experiments in this study demonstrated that mice that lack AUF1 display accelerated skeletal muscle wasting as they age. These AUF1-depleted mice also showed impaired skeletal muscle repair following injury. When the molecular characteristics of these AUF1-depleted muscle satellite cells were examined, Schneider and his collaborators showed that auf1−/− satellite cells had increased stability and overexpression of so-called “ARE-mRNAs.” ARE mRNAs contain AU-rich elements at their tail-ends. AUF1 proteins bind to these ARE mRNAs and induce their degradation. In the absence of AUF1, muscle satellite cells accumulate ARE mRNAs. One of these ARE mRNAs includes that which encodes matrix metalloprotease, MMP9. Overexpression of MMP9 by aging muscle satellite cells causes degradation of the skeletal muscle matrix, which prevents satellite-cell-mediated regeneration of muscles. Consequently, the muscle satellite cells return to their quiescent state and fail to divide and repair skeletal muscle.

When Schneider and his coworkers and collaborators blocked MMP9 activity in auf1−/− mice, they found that they had restored skeletal muscle repair and maintenance of the satellite cell population.

These experiments suggest that repurposing drugs originally developed for cancer treatment that blocks MMP9 activity might be a way to dial down age-related sarcopenia.

“This provides a potential path to clinical treatments that accelerate muscle regeneration following traumatic injury, or in patients with certain types of adult onset muscular dystrophy,” said Schneider.

This work was published here: Devon M. Chenette et al., “Targeted mRNA Decay by RNA Binding Protein AUF1 Regulates Adult Muscle Stem Cell Fate, Promoting Skeletal Muscle Integrity,” Cell Reports, 2016; DOI: 10.1016/j.celrep.2016.06.095.

Beta-Integrin Implicated In Slow Healing Of Aged Muscles


With age, the function and regenerative abilities of skeletal muscles decrease. Therefore, the elderly can find it difficult to recover from injury or surgery.

A new study from the laboratory of Chen-Ming Fan from Johns Hopkins University has shown that a protein called β1-integrin is crucial for muscle regeneration. β1-integrin seems to provide a promising target for therapeutic intervention to combat muscle aging or disease.

Muscle stem cells are the primary source of muscle regeneration after muscle injury from exercise, accidents, or surgery. These specialized adult stem cells lie dormant in the muscle tissue, and muscles even have them stored off to the side of the individual muscle fibers. Because of their location, these muscle stem cells are known as muscle “satellite cells.” After damage, these satellite cells awaken and proliferate, and go on to make new muscle fibers and restore muscle function. Some satellite cells return to dormancy, which allows the muscle to keep a reservoir of healing cells that can repair the muscle over and over again. Fan and her colleagues determined that proteins called integrins, and in particular, β1-integrin, are integral for maintaining the cycle of hibernation, activation, proliferation, and then return to hibernation, in muscle stem cells.

Integrins are cell surface proteins that provide tight connections between cells and the immediate external environment.

Integrin Dimer Structure: Globular domain structures of α and β subunits in a stable dimer. Ligand binding happens at the interface of the αI (left panel) or β-propeller (right panel) and the βI domain.
Integrin Dimer Structure: Globular domain structures of α and β subunits in a stable dimer. Ligand binding happens at the interface of the αI (left panel) or β-propeller (right panel) and the βI domain.

Without integrins, almost every stage of the regeneration is disrupted. Fan and her group predicted that defects in β1-integrin likely contribute to aging, which is associated with reduced muscle stem cell function and decreased quantities of muscle stem cells. This means that healing after injury or surgery is very slow, which can cause a long period of immobility and an accompanying loss of muscle mass. Inefficient muscular healing in the elderly is a significant clinical problem. Therapeutic approaches would be quite welcome by the aging population and their physicians. One way to improve muscle regeneration would be to stimulate muscle satellite cells in older individuals.

Fan and others determined that β1-integrin function is diminished in aged muscle stem cells. When they artificially activated integrins in aged mice, their regenerative abilities were restored to youthful levels. Improvement in regeneration, strength, and function were also seen when this treatment was applied to animals with muscular dystrophy, which underscores the potential importance of such an approach for the treatment of muscle disorders.

Muscle stem cells use β1-integrin to interact with many other proteins in the external environment of the muscle. Among this forest of proteins in the external environment of the muscle, Fan and her coworkers found one called fibronectin that might be the most relevant. They discovered that aged muscles contain substantially less fibronectin compared to young muscles. Like β1-integrin, eliminating fibronectin from young muscles makes them function as though they were old. However, restoring fibronectin to aged muscle tissue restores muscle regeneration to youthful levels. Fan’s group demonstrated a strong link between β1-integrin, fibronectin and muscle stem cell regeneration.

Taken together, the results show that aged muscle stem cells with compromised β1-integrin activity and aged muscles with insufficient amount of fibronectin both root causes of muscle aging. This makes β1-integrin and fibronectin very promising therapeutic targets.

This work appeared in the following journal: Michelle Rozo et al., “Targeting β1-integrin signaling enhances regeneration in aged and dystrophic muscle in mice,” Nature Medicine, 2016; DOI: 10.1038/nm.4116.

LIF Increases Muscle Satellite Expansion in Culture and Transplantation Efficiency


Transplantation of satellite stem cells, which are found in skeletal muscles, might potentially treat degenerative muscle diseases such as Duchenne muscular dystrophy. However, muscle satellite cells have an unfortunate tendency to lose their ability to be transplanted then they are grown in culture.

In order to generate enough cells for transplantation, the cells are isolated from the body and then they must be grown in culture. However, in order to properly grow in culture, the cells must be prevented from differentiating because fully differentiated cells stop growing and die soon after transplantation. Several growth factors, cytokines, and chemicals have been used in muscle satellite cell culture systems. Unfortunately, the optimal culture conditions required to maintain the undifferentiated state, inhibit differentiation, and enhance eventual transplantation efficiency have not yet been established satisfactorily.

Because it is impossible to extract enough satellite cells for therapeutic purposed from biopsies, these cells must be expanded in culture. However this very act of culturing satellite cells renders them inefficient for clinical purposes. How can we break away from this clinical catch-22?

Shin’ichi Takeda from the National Center of Neurology and Psychiatry and his colleagues have used growth factors to maintain muscle satellite cell efficiency during cell culture. In particular, Takeda and others used a growth factor called leukemia inhibitory factor (LIF). LIF effectively maintains the undifferentiated state of the satellite cells and enhances their expansion and transplantation efficiency. LIF is also thought to be involved in muscle regeneration.

This is the first study on the effect of LIF on the transplantation efficiency of primary satellite cells,” said Shin’ichi Takeda of the National Center of Neurology and Psychiatry. “This research enables us to get one step closer to the optimal culture conditions for muscle stem cells.”

The precise mechanisms by which LIF enhances transplantation efficiency remain unknown. Present work is trying to determine the downstream targets of LIF. Identifying the precise mechanisms by which LIF enhances satellite cell transplantation efficiency would help to clarify the functional importance of LIF in muscle regeneration, and, even more importantly, further its potential application in cell transplantation therapy.

The reference for this paper is: N. Ito et al., “Enhancement of Satellite Cell Transplantation Efficiency by Leukemia Inhibitory Factor,” Journal of Neuromuscular Diseases, 2016; 3 (2): 201. DOI: 10.3233/JND-160156.

Dying Muscles Leave “Ghost Fibers” that Direct Muscle Regeneration


When muscles are injured, they die off in order to make room for the growth of replacement muscles. However, it turns out that these moribund muscle leave behind small evanescent fibers that have been called “ghost fibers.” Ghost fibers seem to be remnants of the gooey stuff that provides the substratum upon which muscle cells sit. This gooey foundation is called “extracellular matrix” or ECM. The ECM consists of acid sugars called “glycosaminoglycans,” which are given the unfortunate abbreviation of GAGs, proteins to which GAGs are attached called “proteoglycans,” and proteins that glue cells to the ECM, such as fibronectin, laminin, and collagen IV. Cells adhere to the ECM by means of receptors embedded in their cell membranes called integrins.

Extracellular matrix

Dying muscle cells leave collagen fibers in their wake and these collagen fibers constitute these so-called ghost fibers. However, these ghost fibers provide the structure into which new muscle cells are inserted. A new study by research teams at the Carnegie Institution for Science and the National Institute of Child Health and Human Development that was published in the journal Cell Stem Cell has established that ghost fibers guide new muscle cells to grow in place and ultimately heal muscle injury in laboratory mice.

Ghost Fibers
Ghost Fibers

Chen-Ming Fan at the Carnegie Institute of Washington in Baltimore, Maryland and his colleagues, in collaboration with and Jennifer Lippincott-Schwartz and her colleagues from the NIH disabled the hind limb muscles of laboratory mice by means of physical injury (laceration), or the administration of toxins. These insults to the skeletal muscles caused the injured muscle fibers to die and disintegrate. They also confirmed that as the skeletal muscle disappeared, they left networks of collagen ghost fibers in their wake.

Then, this team utilized three-dimensional, time-lapse intravital imaging to directly visualize the process of muscle regeneration in live mice. What they saw was stunning. The extracellular matrix remnants or ghost fibers left by the injured skeletal directed muscle stem/progenitor cell behavior during muscle regeneration. The two-photon imaging and second-harmonic generation microscopy employed by this team enabled them to precisely observe the muscle stem and precursor cells in individual mice orient themselves along the ghost fibers and grow new muscle tissue.

The muscle stem cells were quiescent and did not move in uninjured muscle tissue. Only when muscle cells were injured did the muscle stem cells come to life, move to the site of injury and begin the healing process. Both the cell division of these muscle stem cells and their migration were oriented along the longitudinal axes of the ghost fibers.

ImageJ=1.49m unit=inch
ImageJ=1.49m
unit=inch

If the ghost fibers were artificially reoriented, then the muscle progenitors migrated and divided in different planes and gave rise to disorganized regenerated muscle fibers.

From these results, Fan and his team concluded that “the ghost fiber (1) is a key determinant for patterning muscle stem cell behavior and (2) provides the foundation for proportional regeneration. They concluded that “ghost fibers are autonomous, architectural units necessary for proportional regeneration after tissue injury.” They continued, “This finding reinforces the need to fabricate bioengineered matrices that mimic living tissue matrices for tissue regeneration therapy.”

Muscular Dystrophy is a Stem Cell-Based Disease


Michael Rudnicki, who has done pioneering work in muscle stem cell biology and muscle regeneration, and whose work has been featured several times on this blog, has struck again. Rudnicki, who serves as director of the Regenerative Medicine Program at The Ottawa Hospital and a professor at the University of Ottawa and holds the prestigious Canada Research Chair in Molecular Genetics, teamed up with workers from the Sprott Centre for Stem Cell Research and the Sinclair Centre for Regenerative Medicine to investigate the role of muscle-specific stem cells in patients who suffer from Duchenne muscular dystrophy. This new earth-shaking study, which was published in the journal Nature Medicine (November 16, 2015), has changed the way we think about muscular dystrophy and will almost certainly force people to rethink the treatments and cures for this dreadful disease.

According to this new study, Duchenne muscular dystrophy directly affects muscle stem cells, and is, largely a disease of muscle stem cells.

Rudicki said: “For nearly 20 years, we’ve thought that the muscle weakness observed in patients with Duchenne muscular dystrophy is primarily due to problems in their muscle fibers, but our research shows that it is also due to intrinsic defects in the function of their muscle stem cells. This completely changes our understanding of Duchenne muscular dystrophy and could eventually lead to far more effective treatments.”

Muscular dystrophy comes in several different forms, but the predominant sign of muscular dystrophy is progressive muscle weakness. Altogether, muscular dystrophy refers to a group of more than 30 genetic diseases, all of which cause progressive weakness and degeneration of skeletal muscles used during voluntary movement. Approximately half of all who suffer from muscular dystrophy have Duchenne muscular dystrophy (DMD). Because muscular dystrophy results from mutations in the dystrophin gene, which is on the X chromosome, the vast majority of muscular dystrophy patients are male. Girls can be carriers of muscular dystrophy and can be mildly affected.

Interestingly, somewhere around one-third of boys who suffer from DMD have no family history of the disease. Because the dystrophin gene is so large, spontaneous mutations in it are probably relatively common.

The signs and symptoms typically appear between the ages of 2 and 3, and may include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, a strange, shuffling way of walking or having a tendency to walk on their toes, calf muscles that are abnormally large, muscle pain and stiffness, and some learning disabilities.

Becker muscular dystrophy (BMD) has signs and symptoms that are largely similar to those of DMD, but BMD tends to be a milder form of the disease that progresses more slowly. Symptoms typically begin in the teens but, some patients may not experience symptoms until their mid-20s and some may not experience symptoms until later.

There are also several different types of muscular dystrophy-type diseases. Steinert’s disease or myotonic muscular dystrophy, which is characterized by an inability to relax muscles at after contractions, is the most common form of adult-onset muscular dystrophy. The first muscles to be affected are the muscles of the face and neck. Facioscapulohumeral muscular dystrophy affects the muscles of the face and shoulders, where symptoms first begin. When patients with facioscapulohumeral raise their arms, their shoulder blades noticeably protrude. This disease may first manifest itself in children, teenagers as late as age 40. This disease tends to affect one side more than the other.

Limb-girdle muscular dystrophy affects the muscles of the shoulders and hips. There are over 20 inherited forms of this disease, and because this condition is not due to mutations in dystrophin, but to mutations in genes that encode proteins that interact with dystrophin, the inheritance of limb-girdle muscular dystrophy is not sex-linked. Some forms of this disease are recessive and some are dominant. Patients with this type of muscular dystrophy usually trip more often because they have trouble raising the front part of their feet. Some autosomal recessive forms of the disorder are now known to be due to a deficits in proteins called sarcoglycans or dystroglycan.

Congenital muscular dystrophy is extremely varible and is probably a cluster of several different diseases caused by mutations in different genes. Some of types of congenital muscular dystrophy show sex-linked inheritance while others do not. Most cases of congenital muscular dystrophy result from the absence of a muscle protein called merosin, which is found in the connective tissue that surrounds muscle fibers. Other types of congenital muscular dystrophy have normal merosin and still others result from abnormal motor neuron migration. Clinically, this disease is also extremely variable and can manifest itself at birth or before age 2, progress slowly or rapidly, and cause mild disability or severe impairment.

Muscular dystrophy affects all ethnic groups and occurs globally. It affects around 1 in every 3,500 to 6,000 male births each year in the United States.  DMD affects approximately one in 3,600 boys.

Because DMD results from mutations in the dystrophin gene, the vast majority of muscular dystrophy research was based on a simple model in which the Dystrophin protein played a structural role in the structural integrity of muscle fibers. Abnormal versions of the Dystrophin protein caused the muscle fibers to become damaged and die as a result of contraction.  Dystrophin anchors the cytoskeleton of the muscle fibers, which are essential for muscle contraction, to the muscle cell membrane, and then to the extracellular matrix outside the cell that serves as a foundation upon which the muscle cells are built.

gb-2001-2-4-reviews3006-3

However in this current study, Rudnicki and his team discovered that muscle stem cells also express the dystrophin protein. This is a revelation because Dystrophin was thought to be protein that ONLY appeared in mature muscle. However, in this study, it became exceedingly clear that in the absence of Dystrophin, muscle stem cells generated ten-fold fewer muscle precursor cells, and, consequently, far fewer functional muscle fibers. Dystrophin is also a component of a signal transduction pathway that allows muscle stem cells to properly ascertain if they need to replace dead or dying muscle.  Muscle stem cells repair the muscle in response to injury or exercise by dividing to generate precursor cells that differentiate into muscle fibers.

“Muscle stem cells that lack dystrophin cannot tell which way is up and which way is down,” said Dr. Rudnicki. “This is crucial because muscle stem cells need to sense their environment to decide whether to produce more stem cells or to form new muscle fibres. Without this information, muscle stem cells cannot divide properly and cannot properly repair damaged muscle.”

Even though Rudnicki used mice as a model system in these experiments, the Dystrophin protein is highly conserved in most vertebrate animals. Therefore, it is highly likely that these results will also apply to human muscle stem cells.

Treatment for DMD patients is limited to steroids to decrease muscle inflammation and muscle cell death, and physical therapy to increase muscle use and prevent muscle atrophy. These approaches only delay the progression of the disease and alleviate symptoms. Gene therapy experiments and trials are in progress and even show some promise, but Rudnicki’s work tell us that gene therapy approaches must target muscle stem cells as well as muscle fibers if they are to work properly.

“We’re already looking at approaches to correct this problem in muscle stem cells,” said Dr. Rudnicki. “I’m not sure if we will ever cure Duchenne muscular dystrophy, but I’m very hopeful that someday in the future, we will have new therapies that correct the ability of muscle stem cells to repair the muscles of afflicted patients and turn this devastating, lethal disease into a chronic but manageable condition.”

This paper has received high praise from the likes of Ronald Worton, who was one of the co-discovers of the dystrophin gene with Louis Kunkel in 1987.  Worton later served as Vice-President of Research at The Ottawa Hospital from 1996 to 2007.

“When we discovered the gene for Duchenne muscular dystrophy, there was great hope that we would be able to develop a new treatment fairly quickly,” said Dr. Worton, who is now retired. “This has been much more difficult than we initially thought, but Dr. Rudnicki’s research is a major breakthrough that should renew hope for researchers, patients and families.”

Human Muscle Satellite Cells Isolated and Characterized


A research group from the University of California, San Francisco have isolated and characterized human muscle stem cells. In addition, they have established that these stem cells can robustly replicate and repair damaged muscles when they are grafted onto an injured site. These remarkable findings might open the door to potential treatments for patients with severe muscle injuries, paralysis or genetic diseases that adversely affect skeletal muscles (e.g., muscular dystrophy).

Jason Pomerantz, MD is an assistant professor of plastic and reconstructive surgery at UCSF, and served as the managing author of this work. “We’ve shown definitively that these are bona-fide stem cells that can self-renew, proliferate and respond to injury,” said Pomerantz.

Badly damaged muscles can suffer terrible depletion of their native populations of stem cells or even obliteration of the stem cell niches and populations. Since such muscles have lost the very things that can heal them, these muscles will not be able to heal the damage they have sustained. This very fact represents a terrible hurdle for physicians who specialize in patients who have been crippled by muscle injury and paralysis. One of the worse cases is those conditions that cause damage or paralysis in the critical small muscles of the face, hand and eye, according to Pomerantz.

When muscles are badly damaged, they can lose the native populations of stem cells that are needed to heal. This has posed a major roadblock for treating patients crippled by muscle injury and paralysis, particularly in the critical small muscles of the face, hand and eye, Pomerantz said.

Fortunately, there have been remarkable surgical advances in restoring nerves in damaged muscles. Unfortunately, if the healing process takes too long, the stem cell pool is exhausted and the regenerative capacity is attenuated and eventually. Such injured muscles fail to connect to the nerve tissue and without accompanying motor and sensory nerves, skeletal muscles then to degenerate.

“This is partly why we haven’t had major progress in treating these patients in 30 years,” Pomerantz said. “We know we can get the axons there, but we need the stem cells for there to be recovery.”

A group of stem cells called “satellite cells” line the borders of muscle fibers and, in mice, can function as stem cells and contribute to muscle growth and repair. Until now, however, it wasn’t clear whether human satellite cells worked the same way. It was also terribly unclear how to isolate muscle satellite cells from human tissue samples or even adapt them to help treat patients with muscle damage.

Muscle satellite cells in section

Pomerantz and colleagues tackled this problem used muscle tissue from surgical biopsies of muscles of the head, trunk and leg. Then they used antibody staining to show that human satellite cells can be identified by the expression of the transcription factor PAX7 in combination with the cell-surface proteins CD56 and CD29. Pomerantz and his colleagues use this molecular signature to isolate populations of human satellite cells from these patient biopsies. Then they grafted these satellite cells into mice with damaged muscles whose own muscle stem-cell populations had been depleted. Five weeks after the transplantation, these human cells had successfully integrated into the mouse muscles and divided to produce families of daughter stem cells; effectively replenishing the stem cell niche and repairing the damaged muscle tissue.

This characterization of human muscle stem cells and the ability to transplant them into injured muscles has varied and wide-ranging implications for patients who are presently suffering from muscle paralysis, whose damaged muscles have lost the ability to regenerate. Additionally, protocols that allow us to isolate and manipulate human stem cells also may have applications for understanding why our muscles lose their regenerative capacity during normal aging or in the case of genetic diseases such as muscular dystrophy.

“This gives us hope that we will be able to extract healthy stem cells from other muscles in the patient’s body and transplant them at the site of injury,” Pomerantz said. “If replenishing a healthy muscle stem cell pool facilitates reinnervation and recovery, it would be a significant leap forward.”

These findings appeared the Sept. 8 edition in the open access Cell Press journal, Stem Cell Reports.