RxPG News : Spinal Cord Diseases

Stem cells repair damaged spinal cord tissue

Sun, 10 Oct 2010 06:06:53 PST

( from http://www.rxpgnews.com ) A joint study by Professor Jonas Frisén's research group at Karolinska Institutet and their colleagues from France and Japan, and published in Cell Stem Cell, shows how stem cells and several other cell types contribute to the formation of new spinal cord cells in mice and how this changes dramatically after trauma.

The research group has identified a type of stem cell, called an ependymal cell, in the spinal cord. They show that these cells are inactive in the healthy spinal cord, and that the cell formation that takes place does so mainly through the division of more mature cells. When the spinal cord is injured, however, these stem cells are activated to become the dominant source of new cells.

The stem cells then give rise to cells that form scar tissue and to a type of support cell that is an important component of spinal cord functionality. The scientists also show that a certain family of mature cells known as astrocytes produce large numbers of scar-forming cells after injury.

"The stem cells have a certain positive effect following injury, but not enough for spinal cord functionality to be restored," says Jonas Frisén. "One interesting question now is whether pharmaceutical compounds can be identified to stimulate the cells to form more support cells in order to improve functional recovery after a spinal trauma."

Discoveries should aid research into cause of ALS

Wed, 26 Apr 2006 14:53:00 PST

( from http://www.rxpgnews.com ) Two teams of researchers at Northwestern University have found a novel pathological hallmark of the neurodegenerative disease amyotrophic lateral sclerosis (ALS) at the molecular level. The neurologists and biochemists show how and why the mutated superoxide dismutase (SOD1) protein, which is associated with a familial form of ALS, becomes vulnerable and prone to aggregation and also provide evidence linking disease onset with the formation of intermolecular aggregates.

ALS is a progressive paralytic disorder caused by degeneration of motor neurons in the brain and spinal cord. The cause and development (pathogenesis) of the fatal disease are not known, and there is no effective treatment. Fifteen years ago, an international consortium led by Teepu Siddique, M.D., Les Turner ALS Foundation/Herbert C. Wenske Foundation Professor at Northwestern's Feinberg School of Medicine, mapped the first ALS gene to chromosome 21. Subsequently, they found that mutations in the SOD1 gene are responsible for 20 percent of familial (inherited) ALS cases. Siddique and his colleagues also made the first ALS transgenic mouse models.

Although more than 100 types of a single mutation in the SOD1 gene have been identified and multiple lines of the mouse models developed, a key question remains to be answered: How does the genetic mutation alter this incredibly stable protein to make it so toxic that it kills motor neurons and causes neurodegenerative disease?

The presence of aggregated proteins is common to many neurodegenerative disorders, including ALS and Alzheimer's, Parkinson's and prion diseases, but the relevance of these aggregates to the diseases is not well understood. In ALS patients with SOD1 mutations and mouse models overexpressing mutant SOD1, SOD1-positive aggregates were identified in neurons. Researchers do not know if these aggregates are causative, harmless or even beneficial to ALS. Furthermore, the fundamental molecular mechanism by which the SOD1 mutants form aggregates is not clear.

Six years ago Siddique and Han-Xiang Deng, M.D., associate professor of neurology at the Feinberg School, started to develop and analyze various SOD1 transgenic mouse models and found, as they report in the first of the two PNAS papers, that aggregated and insoluble SOD1 is the pathogenic form that causes disease. The aggregation takes place in mitochondria, the powerhouse of the cell, which becomes damaged.

"We also have discovered a mechanism whereby 'normal' molecules of SOD1 are recruited in the presence of mutant SOD1 proteins to participate in the pathogenesis of ALS by forming intermolecular disulfide bonds," said Siddique. "This phenomenon is in some ways akin to the recruitment noted in prion disorders and provides molecular sites for therapeutic intervention." This molecular mechanism also may help explain other types of ALS in which no mutations have been detected in SOD1.

The normal form of SOD1 is a molecule composed of two identical parts, each with an amino acid chain, a copper ion, a zinc ion and an intramolecular disulfide linkage -- a bond within an SOD1 molecule that stabilizes the structure. Intermolecular disulfide bonds, or cross-links, are incorrect bonds that form between, not within, SOD1 molecules.

"A year ago we demonstrated that ALS mutations have the greatest effect on the most immature form of the SOD1 protein, causing it to misfold and form incorrect disulfide bonds that facilitate protein aggregation," said Thomas V. O'Halloran, professor of chemistry. "Those were test tube experiments, but we really wanted to know if we would find the same process in a physiological environment."

To investigate their hypothesis further, O'Halloran and Yoshiaki Furukawa, formerly a post-doctoral fellow in O'Halloran's lab, teamed up with Siddique and Deng. As reported in the second PNAS paper, they show that increased oxidative stress leads to the mutant SOD1 protein forming incorrect disulfide bonds early in its life. The researchers isolated and examined aggregates from the spinal cord of several ALS-model mice. In the diseased mice the scientists found intermolecular disulfide bonds that cross-linked SOD1 molecules together, resulting in the formation of insoluble aggregates. The SOD1 aggregates were specific to the spinal cord, the part of the body most damaged in ALS. Tissues unaffected by the disease, such as the brain and liver, had no aggregates.

Oxidation and protein aggregation have been suspected to play an important role in the pathogenesis of neurodegenerative disorders as well as in the normal aging process. However, the relationship between protein oxidation, protein aggregation and neurodegeneration remains unclear. The oxidative intermolecular disulfide cross-linking paradigm established by the Northwestern researchers provides direct links between protein oxidation, protein aggregation and neurodegeneration in SOD1-mediated ALS. This mechanism may play an important role not only in SOD1-mediated ALS but also in some other neurodegenerative disorders.

"For some time researchers have been thinking that copper, which causes the protein to be bluish-green in color, was the bad guy in this disease," said O'Halloran. "But the data has been building up to say that something else may be responsible for the toxicity. Our results suggest that the status of the disulfide bond, a long overlooked part of the SOD1 protein, plays a pivotal role. The ALS mutations appear to predispose SOD1 to form incorrect disulfide bonds that lead to aggregation of the protein and perhaps initiation of the disease. If these ideas are borne out, our next step is to look for therapeutic approaches that could prevent formation of the disulfide cross-linked aggregates."

First diagnostic indicator for Amytrophic Lateral Sclerosis (ALS) identified

Thu, 23 Feb 2006 12:15:00 PST

( from http://www.rxpgnews.com ) Researchers from Mount Sinai School of Medicine identified three proteins that are found in significantly lower concentration in the cerebral spinal fluid of patients with ALS than in healthy individuals. These are the first biomarkers for this disease.

"ALS is a very difficult disease to diagnose. To date, there is no one test or procedure to ultimately establish the diagnosis of ALS. It is through a clinical examination and series of diagnostic tests, often ruling out other diseases," website of the ALS Association.

Giulio Pasinetti, MD, PhD, Professor of Psychiatry, Neuroscience, and Geriatrics and Adult Development, Mount Sinai School of Medicine and colleagues compared cerebral spinal fluid from patients diagnosed with ALS, patients with other neurological disorders, and healthy individuals. They found that fluid from patients with ALS had significantly lower concentrations of three proteins than either of the other groups. Evaluating the levels of these three proteins proved 95% accurate for diagnosing ALS.

The researchers found that the changes in concentration of these proteins were evident within 1.5 years of onset of symptoms. With current methods, the average time from onset of symptoms to diagnosis is two years. Testing for these protein concentrations may provide a means of early diagnosis, allowing patients to receive relief from symptoms years earlier.

"For the first time we have the possibility of developing a test that can definitively say whether or not a patient has ALS," said Dr. Pasinetti. "Such a test would eliminate the need for patients to undergo months of diagnostic evaluation and remove the uncertainty that currently lingers with physicians and patients even after a diagnosis is made."

Specific signaling link between neurons and muscles in the fruit fly is essential for keeping the nervous system stable.

Sun, 04 Sep 2005 07:20:00 PST

( from http://www.rxpgnews.com ) A UCSF study has found that a specific signaling link between neurons and muscles in the fruit fly is essential for keeping the insect's nervous system stable.

The findings are relevant for ongoing research in identifying causes and developing treatments for neuromuscular neurodegenerative diseases in humans, such as amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, says study co-author Graeme Davis, PhD, associate professor and vice chair of the Department of Biochemistry and Biophysics at the University of California, San Francisco.

"If we want to make new drugs to treat neurodegenerative disease, then we have to identify new drug targets, and our study findings present that potential," he says. "This study is a significant step forward because we have shown that a signaling system composed of several genes is important for keeping the nervous system stable."

The findings are reported in the September issue of the journal Neuron.

The nervous system is a complex pattern of connections that exists for the entire life of the organism, and understanding how the myriad patterns and pathways of these connections are maintained for long periods of time presents an ongoing challenge to scientists, says Davis.

Davis and co-author Benjamin Eaton, PhD, a post-doctoral fellow in Davis' lab, were led to the new discovery through ongoing experiments with a signaling system in fruit flies that is tied to a protein called bone morphogenetic protein, or BMP. They found that the BMP signaling system is required for the long-term stability of the neuromuscular synapse, the point where a nervous impulse passes from a neuron to a muscle to cause muscle movement.

In the absence of BMP signaling, their research showed, the synapse between the nerve and muscle disassembles and degenerates. This observation enabled the team to look for new genes involved in the BMP signaling system, which led to the identification of specific stabilizing factors in the nervous system.

"It is a very complicated task to keep the nervous system stable. We are using a model organism, the fruit fly, to help us rapidly identify the genetic basis for the long-term stability," Davis says. "What we have been able to do with this study is to hone in on several genes that are essential for this stability."

By examining genetic mutations that delete individual genes, the scientists were able to demonstrate that BMP signaling is required for the stability of synaptic connections. Further genetic tests demonstrated that a cytoplasmic enzyme called LIM Kinase1 is an essential link that enables BMP signaling molecules to stabilize the synapse.

Davis notes that working with fruit flies allows scientists to identify the function of new genes very rapidly. "We can easily observe the connections between the nerve and muscle, and see if the nerve is degenerating. Each week we can test hundreds of genes and determine if they are important for stabilizing the synapse between the nerve and muscle."

"The signaling molecules that are present in fruit flies are basically the same as in humans," explains Davis. "In a matter of a few years we hope to test the function of every gene in the genome and identify a whole array of genes that are necessary to keep the neuromuscular synapse stable."

ALS, for example, is a degenerative neuromuscular disease. "If we can find a way to keep the neuromuscular synapse stable, then we might be able to slow down the rate of degeneration," he adds.

"With ALS and other neuromuscular degenerative diseases, only a handful of genes have been identified that either cause the diseases or contribute to their progression."

"The exciting thing about this study," says Davis, "is that it starts to tell us how we can keep a synapse stable. And that can lead us to understanding why synapses degenerate at the muscle cells of people with ALS. If we can identify more genes that are important for synapse stability, then there will be more targets for the development of new drugs to treat these diseases. Currently, the number of potential targets for new drug development is quite limiting and we hope to help change that. This is an exciting time with the potential for real progress in terms of understanding the biology of these diseases."

Mutant Cu/Zn superoxide dismutase (SOD1) enzymes implicated in Lou Gehrig's disease

Thu, 11 Aug 2005 02:51:00 PST

( from http://www.rxpgnews.com ) A new study indicates that mutant Cu/Zn superoxide dismutase (SOD1) enzymes that are associated with an inherited form of Lou Gehrig's disease cause the protein to become sticky in tissues. Partial unfolding of the mutant protein can expose hydrophobic residues that may promote abnormal interactions with other proteins or membranes in the cell.

Over 5,600 people in the U.S. are diagnosed with amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease each year. About 30,000 Americans have the disease at any given time, and 10% of cases are inherited.

"Amyotrophic lateral sclerosis is a neurodegenerative disorder in which neurons of the motor pathways in the brain and spinal cord die," explains Dr. Lawrence J. Hayward of the University of Massachusetts Medical School. "It typically strikes during middle age, and although it may start with only mild weakness, the symptoms can spread insidiously over months to impair mobility, speech and swallowing, and ultimately the muscles required for respiration."

Despite the prevalence of ALS, the biological mechanisms that kill the motor neurons in most patients are incompletely understood. However, for a fraction of inherited ALS patients, mutations in the gene for SOD1 cause the disease by creating a toxic enzyme. Evidence suggests that misfolding or partial unfolding of mutant SOD1 proteins in these patients might be key to the toxicity.

Hoping to learn more about how SOD1 contributes to ALS, Dr. Hayward began to study the properties of several ALS-causing SOD1 mutants in research sponsored by the National Institutes of Health and the ALS Association.

"Our efforts have focused upon trying to explain how over 100 different mutant forms of SOD1 cause inherited ALS," says Dr. Hayward. "The initial results were puzzling because some mutations had dramatic effects on copper and zinc binding, enzymatic activity, and stability of the protein, but many other mutations seemed to cause only subtle changes in these properties in vitro. Yet all of the mutants were known to be toxic in patients."

As a result of several additional experiments done in his lab and by other groups, Dr. Hayward suspected that the mutant proteins might be more vulnerable than the normal enzyme to specific stresses in tissues. In their Journal of Biological Chemistry paper, Dr. Hayward and his colleagues at the University of Massachusetts Medical School show that when the mutant SOD1 enzymes are exposed to reagents that can disrupt some of the protein's bonds or remove its metal ions, they become much stickier than the normal protein.

"The mutants, but not the normal SOD1, adhere to a hydrophobic or 'greasy' surface, and this property could promote abnormal interactions with other proteins or membranes in the cell," explains Dr. Hayward. "How well different tissues can handle this burden of sticky protein, especially during aging, may be one factor that determines which cell types are most vulnerable in the disease. It was interesting to us that the adherent forms were not restricted to the nervous system in the mouse models but were also seen in other tissues such as heart and skeletal muscle. It is possible that this property could contribute to abnormalities in muscle, while other tissues such as kidney do not accumulate hydrophobic SOD1 despite a high expression level of the mutants."

These results may lead to new treatments for some forms of ALS. For example, if researchers can minimize the hydrophobic exposure or can understand how certain tissues prevent build-up of the sticky forms of SOD1, they might be able to boost defenses in tissues known to be susceptible to mutant SOD1 accumulation.

Arimoclomol Significantly Inhibits Progression of Amyotrophic Lateral Sclerosis

Wed, 20 Apr 2005 09:24:00 PST

( from http://www.rxpgnews.com ) CytRx Corporation (Nasdaq: CYTR - News) today announced the completion of a meeting with representatives of the U.S. Food and Drug Administration (FDA) prior to the submission of the Company's Investigational New Drug (IND) application for its lead small molecule drug candidate arimoclomol for the treatment of amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease). The FDA's pre-IND meeting programs are designed to provide sponsors with advance guidance and input on drug development programs.

Jack Barber, Ph.D., CytRx's Senior Vice President, Drug Development, stated, "The purpose of our meeting was to seek guidance from the FDA concerning the upcoming submission of our IND application for arimoclomol. We plan to file an IND application with the FDA and expect to begin a Phase II clinical trial for the treatment of ALS in the current quarter."

Arimoclomol provides cellular protection from abnormal proteins by activating molecular "chaperone" proteins that can repair or degrade the damaged proteins that are believed to cause many diseases, including ALS.

Arimoclomol was previously shown to be well tolerated in two Phase I clinical trials in healthy volunteers. Originally developed to treat diabetic complications, arimoclomol was recently discovered to significantly inhibit progression of ALS in an experimental animal model of the disease (Kierin et al., Nature Medicine, April 2004, Vol. 10(4), 402-5).

According to the ALS Survival Guide, 50% of ALS patients die within 18 months of diagnosis and 80% of ALS patients die within five years of diagnosis. Approximately 30,000 people are living with ALS and nearly 6,000 new cases are diagnosed each year in the U.S. alone, according to the ALS Association. There are over 120,000 people living with ALS worldwide.

CytRx Corporation makes no representation that the FDA will allow any clinical trial to take place upon the filing of the IND, or take any other action to allow arimoclomol to be studied or marketed.