Thursday, 3 April 2014

Study Helps Unravel the Tangled Origin of ALS

Study Helps Unravel the Tangled Origin of ALS
Thursday, 03 April 2014

By studying nerve cells that originated in patients with a severe neurological disease, a University of Wisconsin-Madison researcher has pinpointed an error in protein formation that could be the root of amyotrophic lateral sclerosis.

In this microscope photo of motor neurons created
in the laboratory of Su-Chun Zhang at the University
of Wisconsin-Madison, green marks the nucleus, and
red marks the nerve fibres. Zhang and co-workers at
the Waisman Center have identified a mis-regulation
of protein in the nucleus as the likely first step in the
pathology of ALS, a fatal neurological disorder that
blocks nerve signals to the muscles, and later causes
motor neurons to die. Credit: Hong Chen and
Su-Chun Zhang, Waisman Center, University of
Wisconsin-Madison.
Also called Lou Gehrig's disease, ALS causes paralysis and death. According to the ALS Association, as many as 30,000 Americans are living with ALS.

After a genetic mutation was discovered in a small group of ALS patients, scientists transferred that gene to animals and began to search for drugs that might treat those animals. But that approach has yet to work, says Su-Chun Zhang, a neuroscientist at the Waisman Center at UW-Madison, who is senior author of the new report, published April 3 in the journal Cell Stem Cell.

Zhang has been using a different approach — studying diseased human cells in lab dishes. Those cells, called motor neurons, direct muscles to contract and are the site of failure in ALS.

About 10 years ago, Zhang was the first in the world to grow motor neurons from human embryonic stem cells. More recently, he updated that approach by transforming skin cells into iPS (induced pluripotent stem) cells that were transformed, in turn, into motor neurons.

IPS cells can be used as "disease models," as they carry many of the same traits as their donor. Zhang says the iPS approach offers a key advantage over the genetic approach, which "can only study the results of a known disease-causing gene. With iPS, you can take a cell from any patient, and grow up motor neurons that have ALS. That offers a new way to look at the basic disease pathology."

In the new report, Zhang, Waisman scientist Hong Chen, and colleagues have pointed a finger at proteins that build a transport structure inside the motor neurons. Called neurofilament, this structure moves chemicals and cellular subunits to the far reaches of the nerve cell. The cargo needing movement includes neurotransmitters, which signal the muscles, and mitochondria, which process energy.

Motor neurons that control foot muscles are about three feet long, so neurotransmitters must be moved a yard from their origin in the cell body to the location where they can signal the muscles, Zhang says. A patient lacking this connection becomes paralyzed; tellingly, the first sign of ALS is often paralysis in the feet and legs.

Scientists have known for some time that in ALS, "tangles" along the nerve's projections, formed of misshapen protein, block the passage along the nerve fibres, eventually causing the nerve fibre to malfunction and die. The core of the new discovery is the source of these tangles: a shortage of one of the three proteins in the neurofilament.

The neurofilament combines structural and functional roles, Zhang says.

"Like the studs, joists and rafters of a house, the neurofilament is the backbone of the cell, but it's constantly changing. These proteins need to be shipped from the cell body, where they are produced, to the most distant part, and then be shipped back for recycling. If the proteins cannot form correctly and be transported easily, they form tangles that cause a cascade of problems."

Finding neurofilament tangles in an autopsy of an ALS patient "will not tell you how they happen, when or why they happen," Zhang says. But with millions of cells — all carrying the human disease — to work with, Zhang's research group discovered the source of the tangles in the protein subunits that compose the neurofilaments.

"Our discovery here is that the disease ALS is caused by mis-regulation of one step in the production of the neurofilament," he says.

Beyond ALS, Zhang says "very similar tangles" appear in Alzheimer's and Parkinson's diseases.

"We got really excited at the idea that when you study ALS, you may be looking at the root of many neurodegenerative disorders."

While working with motor neurons sourced in stem cells from patients, Zhang says he and his colleagues saw "quite an amazing thing.”

“The motor neurons we reprogrammed from patient skin cells were relatively young, and we found that the mis-regulation happens very early, which means it is the most likely cause of this disease. Nobody knew this before, but we think if you can target this early step in pathology, you can potentially rescue the nerve cell."

In the experiment just reported, Zhang found a way to rescue the neural cells living in his lab dishes. When his group "edited" the gene that directs formation of the deficient protein, "suddenly the cells looked normal," Zhang says.

Already, he reports, scientists at the Small Molecule Screening and Synthesis Facility at UW-Madison are looking for a way to rescue diseased motor neurons. These neurons are made by the millions from stem cells using techniques that Zhang has perfected over the years.

Zhang says "libraries" of candidate drugs, each containing a thousand or more compounds, are being tested.

"This is exciting. We can put this into action right away. The basic research is now starting to pay off. With a disease like this, there is no time to waste."

Contact: Su-Chun Zhang

Reference:
Modeling ALS with iPSCs Reveals that Mutant SOD1 Misregulates Neurofilament Balance in Motor Neurons
Hong Chen, Kun Qian, Zhongwei Du, Jingyuan Cao, Andrew Petersen, Huisheng Liu, Lisle W. Blackbourn, CindyTzu-Ling Huang, Anthony Errigo,Yingnan Yin, Jianfeng Lu, Melvin Ayala, Su-Chun Zhang
Cell Stem Cell, April 3 2014, DOI: http://dx.doi.org/10.1016/j.stem.2014.02.004
.........


For more on stem cells and cloning, go to CellNEWS at
http://cellnews-blog.blogspot.com/

Patient Stem Cells Help Identify Common Problem in ALS

Discovery will lead directly to clinical trials
Thursday, 03 April 2014

Harvard stem cell scientists have discovered that a recently approved medication for epilepsy may possibly be a meaningful treatment for amyotrophic lateral sclerosis (ALS) — Lou Gehrig's disease, a uniformly fatal neurodegenerative disorder. The researchers are now collaborating with Massachusetts General Hospital to design an initial clinical trial testing the safety of the treatment in ALS patients.

Kevin Eggan, a principal faculty member of the
Harvard Stem Cell Institute and Professor in
Harvard's Department of Stem Cell and
Regenerative Biology is credited with first moving
ALS – Lou Gehrig's disease into a laboratory dish
in 2008, paving the way for the study of treatments
using human cells. Credit: B.D. Colen/Harvard
University. 
The investigators all caution that a great deal needs to be done to assure the safety and efficacy of the treatment in ALS patients, before physicians should start offering it.

The work, laid out in two related papers in the April 3 online editions of Cell Stem Cell and Cell Reports, is the long-term fruition of studies by Harvard Stem Cell Institute (HSCI) Principal Faculty member Kevin Eggan, PhD, who, in a 2008 Science paper, first raised the possibility of using ALS patient-derived stem cells to better understand the disease and identify therapeutic targets for new drugs.

Now Eggan and HSCI colleague Clifford Woolf, MD, PhD, have found that the many independent mutations that cause ALS may be linked by their ability to trigger abnormally high activity in motor neurons. Using neurons derived from stem cells made from ALS patient skin cells, the two research teams conducted clinical trials of the anti-epilepsy medication on neurons in laboratory dishes, finding that it reduced the hyper-excitability of the cells.

ALS is a devastating and currently untreatable degradation of motor neurons, the long nerve cells that connect the spinal cord to the muscles of the body. While several potential treatments have looked promising in mice, all proved disappointing in the clinic.

"The big problem in ALS is that there are more than a hundred mutations in dozens of genes that all cause the disease, but almost all of the therapeutics that have gone forward in the clinic have done so for just one of those mutations, SOD1, which almost everyone studies in mice," said Eggan, a professor in Harvard's Department of Stem and Regenerative Biology.

"And so, the key question that we really wanted to address was — are clinical efforts failing because the mouse is taking us on a wild goose chase, or is it simply that people haven't had the opportunity to pre-test whether their ideas are true across lots of forms of ALS?", he continued.

In the Cell Stem Cell study, Eggan and postdoctoral fellow Evangelos Kiskinis, PhD, led an effort to make stem cell lines from two women with ALS who have SOD1 mutations to compare human biology and mouse biology. Using a technology called RNA sequencing to look at how the mutation changes gene expression in these lines, the researchers then traced the changes to their impact on biological pathways.

"We found that the mutation makes changes in the motor neurons, which aren't so different from the changes that you see in the mice," Eggan said.

"I think our paper says that while there are definitely some human-specific biology, the mice weren't totally misleading."

Eggan's lab then created more stem cell-derived motor neurons from patients with another form of ALS, as well as people without the disease, to see what changes occur in ALS cells and if these were present across independent genetic mutations.

The surprising result, reported in the Cell Reports study, was that the motor neurons that possessed ALS mutations had a sporadic increase in motor neuron firing while the healthy neurons were quiet unless stimulated in some way.

The ALS hyper-excitability was further examined by Woolf's team, led by Harvard Medical School neurologist Brian Wainger, MD, PhD. Working with Eggan and Kiskinis collectively, they found a cyclical relationship between the increased neuron activity and abnormal protein folding. In the two papers, they describe how the over-excitable ALS neurons generate more abnormally folded proteins, further increasing their excitability. The strain of this cycle seems to put the neurons in a vulnerable state where they are more likely to die.

"The convergence on a single mechanism offered a very attractive place to intervene therapeutically," said Woolf, a Harvard Medical School professor in neurology and neurobiology at Boston Children's Hospital, who also co-leads HSCI's Nervous System Diseases Program.

"It looked like there's a deficit in potassium channels in the ALS motor neurons and that led us to then test whether drugs that open the potassium channels may reduce this hyper-excitability — and indeed that's exactly what we found," he said.

"We found that retigabine, which has recently been approved as an anticonvulsive, normalized this activity; so now we can formally go from the dish to the patient and actually explore whether the drug might have any beneficial effect."

Massachusetts General Hospital neurologist Merit Cudkowicz, MD, with Wainger, will be running the clinical trials, which will first test for side effects when giving the drug to ALS patients. The researchers caution against calling this work a breakthrough or having doctors prescribe this drug to patients immediately. Clinical trials are necessary to determine whether there are any unusual interactions between the drug and having ALS, as having a particular disease can make someone more sensitive to certain types of drugs.

"The whole intact nervous system is more complicated than the cells that we have in the dish at the moment," Eggan said.

"And now the next step is to say whether or not the drug will be helpful in that context, and it's too early to say for sure."

The scientists credit emerging technologies and the unique collaboration between a stem cell lab and a neuron physiology lab as an essential part of making this research clinically relevant for ALS patients.

"I think it's the beginning of a complete change in the way we do medicine for serious diseases like this," Woolf said.

"In a traditional clinical trial, you give the patient the placebo or an active ingredient to see the effects they have and it's over. Here we can take the same stem cell lines and have an infinite capacity to do clinical trials in a dish."

Contact: B.D. Colen

References:
Intrinsic membrane hyperexcitability of amyotrophic lateral sclerosis patient-derived motor neurons 
Brian J. Wainger, Evangelos Kiskinis, Cassidy Mellin, Ole Wiskow, Steve S.W. Han, Jackson Sandoe, Numa P. Perez, Luis A. Williams, Seungkyu Lee, Gabriella Boulting, James D. Berry, Robert H. Brown Jr., Merit E. Cudkowicz, Bruce P. Bean, Kevin Eggan, Clifford J. Woolf
Cell Reports, April 24, 2014 [published early online April 3, 2014]

Pathways disrupted in human ALS motor neurons identified through genetic correction of mutant SOD1 
Cell Stem Cell, June 5, 2014 [published early online April 3, 2014]
.........


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

New Study Casts Doubt on Heart Regeneration in Mammals

New Study Casts Doubt on Heart Regeneration in Mammals
Thursday, 03 April 2014

The resected area is still missing and scar
formation (red) is seen in the border of the
resection line. Red: Non-muscle myosin, green:
Desmin, blue: Dapi. Credit: Stem Cell Reports,
Andersen et al..
The mammalian heart has generally been considered to lack the ability to repair itself after injury, but a 2011 study in new-born mice challenged this view, providing evidence for complete regeneration after resection of 10% of the apex, the lowest part of the heart. In a study published by Cell Press in Stem Cell Reports on April 3, 2014, researchers attempted to replicate these recent findings but failed to uncover any evidence of complete heart regeneration in new-born mice that underwent apex resection.

"Our results question the usefulness of the apex resection model for identifying molecular mechanisms underlying heart regeneration after damage and underscore the need for the scientific community to firmly establish whether or not the mammalian heart is capable of regeneration," says lead study author Ditte Andersen of Odense University Hospital and the University of Southern Denmark.

The apex is still missing in AR hearts and scar
formation with connective tissue and fat is seen. 
Credit: Stem Cell Reports, Andersen et al.. 
Cardiovascular disease is currently one of the leading causes of death worldwide, and scientists have mainly attributed this high mortality rate to the inability of the mammalian heart to regenerate after injury. Novel therapies capable of enhancing the heart's ability to recover after a heart attack or other type of injury are urgently needed. That's why a 2011 Science report from Porrello et al. that provided evidence of complete heart regeneration in new-born mice attracted a great deal of attention and raised hopes for identifying factors that could improve heart regeneration.

The AR heart is more rounded and the apex is
lined by a scar composed of Collagen (red). 
Credit: Stem Cell Reports, Andersen et al.. 
This study prompted Andersen, Søren Sheikh, and their colleagues to look for factors that enable heart regeneration, but they were surprised to find no signs of true heart regeneration in new-born mice that underwent apex resection. Three weeks after this procedure, the damaged hearts were about 10% shorter and weighed 14% less than the hearts of control mice that underwent the same surgical procedure without apex resection. Moreover, the damaged hearts had large scars and lacked proliferating muscle cells crucial for restoring heart function.

"The notion of mammalian heart regeneration has given a lot of hope in the scientific community for finding important factors that may be used for improving adult heart regeneration," Andersen says.

"We hope that our study will add another view on this important matter and spur a lot of studies from other independent labs that may shed further light on this controversial area of research."

Source: Cell Press 
Contact: Mary Beth O'Leary

Reference:
Do Neonatal Mouse Hearts Regenerate following Heart Apex Resection?
Ditte Caroline Andersen, Suganya Ganesalingam, Charlotte Harken Jensen, and Søren Paludan Sheikh
.........


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