Researchers at the University of California San Diego School of Medicine published research describing a new way to deliver a gene-silencing vector to mice with ALS.
Amyotrophic lateral sclerosis (ALS), sometimes called Lou Gehrig’s disease, is a neurodegenerative disease affecting nerve cells in the brain and spinal cord. Researchers at the University of California San Diego School of Medicine published research describing a new way to deliver a gene-silencing vector to mice with ALS. The therapy resulted in long-term suppression of the disease if the treatment was given before the disease started. It also blocked disease progression in the mice if symptoms already appeared.
The study was published in the journal Nature Medicine.
“At present, this therapeutic approach provides the most potent therapy ever demonstrated in mouse models of mutated SOD1 gene-linked ALS,” said senior author Martin Marsala, professor in the Department of Anesthesiology at UC San Diego School of Medicine. “In addition, effective spinal cord delivery of AAV9 vector in adult animals suggests that the use of this new delivery method will likely be effective in treatment of other hereditary forms of ALS or other spinal neurodegenerative disorders that require spinal parenchymal delivery of therapeutic gene(s) or mutated-gene silencing machinery, such as in C9orf72 gene mutation-linked ALS or in some forms of lysosomal storage disease.”
ALS appears in two forms, sporadic and familial. The most common form is sporadic, responsible for 90 to 95% of all cases. Familial ALS makes up 5 to 10% of all cases in the U.S., and as the name suggests, is inherited. Studies have shown that a least 200 mutations of the SOD1 gene are linked to ALS.
In healthy individuals, the SOD1 gene provides instructions for an enzyme called superoxide dismutase. This enzyme is used to break down superoxide radicals, which are toxic oxygen molecules that are a byproduct of normal cellular processes. It is believed that the mutations in the gene cause ineffective removal of superoxide radicals or potentially cause other toxicities resulting in motor neuron cell death.
The new research involves injecting shRNA, an artificial RNA molecule that can turn off, or silence, a targeted gene. This delivers shRNA to cells by way of a harmless adeno-associated virus (AAV). In the research, they injected the viruses carrying shRNA into two locations in the spinal cord of adult mice expressing an ALS-causing mutation of the SOD1 gene. They were performed just before disease onset or after the laboratory animals started showing symptoms.
The researchers have tested the approach in adult pigs, whose have spinal cord dimensions closer to those in humans. They found that by using an injector developed for adult humans, the procedure could be performed without surgical complications and in a reliable fashion.
The next step will be more safety studies with a large animal model.
“While no detectable side effects related to treatment were seen in mice more than one year after treatment, the definition of safety in large animal specimens more similar to humans is a critical step in advancing this treatment approach toward clinical testing,” Marsala said.
About 5,000 people are diagnosed with ALS in the U.S. each year, with about 30,000 people living with the disease. There are symptomatic treatments, but no cure. Most patients die from the disease two to five years after diagnosis.
