C95 STEM CELLS AND ALS/MND: WHERE ARE WE NOW?
SVENDSEN C
The Waisman Center, University of Wisconsin, United States
E-mail address for correspondence: [email protected]
Keywords: stem cells, cell therapy, MND model
The hope of one-day producing new motor neurons to replace those lost in ALS/MND remains the holy grail of stem cell research for motor neuron diseases. However, connecting new upper or lower motor neurons to their targets remains an enormous challenge, which will require a significant amount of new research in cellular and animal models.
But there is far more going on in the stem cell field than simply motor neuron replacement. Astrocytes, the support cells of the brain and spinal cord, may also be affected in ALS/MND and it is now possible to grow human stem cells that can make astrocytes following transplantation. Furthermore, they can be modified to produce powerful growth factors such as GDNF and IGF-1 which, while potentially important for protecting motor neurons, are difficult to get into the brain and spinal cord any other way. Thus, combining stem cell replacement of astrocytes with growth factor therapy is far more practical than motor neuron replacement at the present time, and may be translatable to the clinic in the near future.
In addition to stem cells providing a potential new cell therapy for ALS/MND they may also provide a tool for studying the mechanisms underlying motor neuron degeneration. New studies have shown that induced pluripotent stem (iPS) cells can be generated from adult human skin samples. These iPS cells are identical in many respects to human embryonic stem cells and can be made to differentiate into motor neurons under the correct conditions. We and others have begun to generate iPS cells from patients with ALS/MND and spinal muscular atrophy (SMA). Motor neurons and astrocytes generated from these cells give a new source of important human tissue to study how the disease may lead to cell death. They may also be used to screen potential new drugs.
Clearly this is a very exciting time in the stem cell world – both from a cell therapy and drug discovery aspect. But hope and hype must be carefully balanced and new discoveries and therapies will take require significant time and effort over the next few years.
C96 IMMUNISATION APPROACHES TO THERAPY FOR ALS
JULIEN JP, GROS-LOUIS F, BOSCO D, BROWN R
Laval University, Quebec, Canada
E-mail address for correspondence: [email protected]
Keywords: SOD1, immunization
The finding that mutant SOD1 can be secreted and that extracellular SOD1 mutants can trigger the death of motor neurons in culture led us to test immunization protocols aiming to reduce the burden of SOD1 mutant in nervous tissue of mice models of ALS. Initially, vaccination approaches were tested in G37R SOD1 mice using bacterially-purified recombinant SOD1 mutant protein as immunogen. We showed that vaccination of G37R SOD1 mice by injections of adjuvant-SOD1G93A was effective in delaying disease onset and extending life span by over 4 weeks. However, we believe that passive immunisation approaches would be safer in future human ALS clinical tests. In order to develop a passive immunisation approach, we have derived mouse monoclonal antibodies against SOD1 species using standard hybridoma technology. This was done with the use of recombinant G93A SOD1 apo-form as immunogen. The apo-form of the protein was selected because it has been reported that in SOD1 lacking metal some regions of the molecule become more exposed to external environment, especially the hydrophobic β-strands. The concept is that regions normally buried in the native dimer would become exposed, thereby acting as antigens. Using this approach, we succeeded in generating 12 antibodies that bind specifically to SOD1 mutants but not intact WT SOD1. These conformation-specific antibodies can be used to detect the accumulation and distribution of misfolded human SOD1 species during disease progression in mutant SOD1 mice. Misfolded SOD1 species are first detected in motor neurons and then spread out to other cell types as the disease progresses. Using immunoprecipitation (IP) assays, we found that some of these monoclonal antibodies can detect specifically misfolded SOD1 species in spinal cord extracts of fALS with SOD1A4V mutation. Moreover, our antibodies were able to detect misfolded SOD1 species in autopsy spinal cord samples from sporadic ALS patients using IP assay or immunohistochemistry examination. These data support the view that SOD1 misfolding might represent a common pathogenic pathway to fALS and sALS. We have tested a passive immunization approach through intraventricular infusion of conformation specific antibodies using osmotic minipumps starting at 90 days of age in G93A SOD1 mice. Such immunotherapy succeeded in prolonging the lifespan of SOD1G93A mice. For development of human ALS immunotherapy, strategies are now being considered to derive humanised antibodies.