Previous research had indicated that a protein known as insulin-like growth factor-1 (IGF-1), which stimulates nerve cell growth, was a good therapeutic candidate for ALS, but trials in which it was administered directly were not successful. Fred H. Gage of the Salk Institute for Biological Studies and his colleagues attempted a new strategy to deliver the protein to affected neurons. They exploited a so-called adeno-associated viral vector (AAV) to transport the IGF-1-producing gene from muscle tissue to the neurons that control it. When mice engineered to develop ALS-like symptoms received AAV injections in their quadriceps and muscles behind their ribs, they lived 40 days longer on average than animals that did not receive treatment. The researchers also observed beneficial results in animals that received the injections much later in life. "This animal study is the first to identify a treatment that slows the disease once symptoms have already appeared, a significant finding that offers insight into the disease mechanism and important therapeutic potential," notes study co-author Jeffrey Rothstein of Johns Hopkins University.
The scientists report that IGF-1 decreased the amount of a second protein involved in cell apoptosis, or programmed cell death, by 63 percent, allowing neurons to survive longer. Although the findings are encouraging--a clinical trial is currently being designed--further research is needed to determine whether the approach can work in humans.