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Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease
characterized by death of the neurons regulating muscle movement, called
motor neurons. Failure of the breathing muscles is fatal and patients
typically die within 2-5 years from diagnosis. ALS is a multifactorial
disease where different cell types contribute to the pathologic mechanisms.
In 1993 researchers identified the first mutation associated with familial
ALS, a mutation in superoxide dismutase 1 (SOD1), a gene involved in
detoxification of radicals. This finding lead to the generation of transgenic
animal models carrying the human mutant gene and developing neuronal
degeneration similar to patients affected by ALS.
Experiments using the mouse models of this disease highlighted the role that different cell types play
in determining onset or progression of disease. Recent studies have demonstrated that the cells
normally involved in supporting the neurons in the brain and spinal cord, called glia, are implicated in
disease development and progression.
With the discovery that adult human skin cells could be transformed into induced pluripotent stem
(iPS) cells and subsequently into nerve cells and glia, the field of ALS saw the opportunity to finally
model not only the familial, but especially the sporadic disease in vitro.
In 2011 researchers managed to isolate cells from the brain and spinal cord that could be
differentiated into glial cells, in particular astrocytes, one of the cells types supporting neurons. The
studies conducted using these cells demonstrated that astrocytes from ALS patients are not able to
support neurons; on the contrary, they induce their death.
Project objectives
In this study we aimed at identifying factors that determine or contribute to astrocyte toxicity against
neurons. During the first year we planned to identify selected genes that contribute to astrocyte
toxicity and neuronal death in ALS, with the final aim to use gene therapy approaches to silence these
toxic genes and improve neuronal activity and survival.
In the second period of the Fellowship we aimed at screening about 4000 drugs to identify chemical
compounds that, in a similar way, can decrease glia toxicity towards neurons.
Description of the work performed since the beginning of the project
We performed a gene expression study to look at what genes are more or less expressed in astrocytes
from the ALS mouse model compared to control healthy mice. Using the bioinformatics expertise
available in Sheffield, we identified several candidate genes and pathways potentially involved in
astrocyte toxicity. In particular, in Columbus the Fellow focused on the role of the immune system,
including genes belonging to or regulating the complement system, inflammation and the immune
response adopted by glia.
Moreover, the Fellow joined the Kaspar lab when one graduate student had just started studying the
effect of decreasing the expression of the superoxide dismutase 1 (SOD1) gene at different time points
of the disease in the mouse model of ALS using a gene therapy approach. The study developed further
into testing the safety of this approach for clinical trial.
Co-cultures of human astrocytes and motor neurons were set up to test the toxic properties of
astrocytes from ALS patients.
The Fellow contributed to setting up a new method to develop glia cells from skin cells isolated from
patients affected by familial or sporadic ALS patients and healthy individuals and then culture them
with healthy neurons to test the effect of these supporting cells onto neuronal survival.
Decreasing the expression of selected genes involved in inflammation and immune system regulation
in glial cells from ALS patients was extremely successful in rescuing neuronal survival in co-culture.
During the last year of this fellowship, the Fellow screened more than 1000 compounds on ALS
astrocytes and healthy neurons to identify drugs that can rescue neuronal survival. We identified 17
compounds that are more effective in protecting neurons than Riluzole, the only FDA approved drug
used on ALS patients.
In conclusion, this study has produced new models to study sporadic as well as familial ALS. Skinderived neurons and glia are the only way to model the sporadic form of ALS, the variant that is not
linked to any genetic mutation and, therefore, cannot be easily modelled. This study has brought to
light new targets for gene therapy and drug screening to silence astrocyte toxicity, thus identifying
new therapeutic treatments.
The new tools developed to model human glia in vitro have generated the unique opportunity to test a
large number of chemical compounds on several different cell lines each representing a different form
of ALS and a different patient.
Ultimately, this project has opened the door to personalised drug screenings and treatments (Fig1).
Fig1. Use of skin-derived astrocytes and neurons to model ALS and identify new drugs for disease
treatment.