A new Hope for Muscle Wasting Diseases
Muscle wasting diseases can be difficult to watch. They are typically slow and have a very painful progression, some to the point of not even being able to breath on ones own. But new research might change all that. Scientists have developed a novel technique to promote tissue repair in damaged muscles. The technique also creates a sustainable pool of muscle stem cells needed to support multiple rounds of muscle repair.
The study provides promise for a new therapeutic approach to treating the millions of people suffering from muscle diseases, including those with muscular dystrophies and muscle wasting associated with cancer and aging.
First a little background, there are two important processes that need to happen to maintain skeletal-muscle health. The first, when muscle is damaged by injury or degenerative disease such as muscular dystrophy, muscle stem cells—or satellite cells—need to differentiate into mature muscle cells to repair injured muscles. The second is the pool of satellite cells need to be replenished so there is a supply to repair muscle in case of future injuries.
In the case of muscular dystrophy, the chronic cycles of muscle regeneration and degeneration that involve these satellite-cell activations exhaust the muscle stem-cell pool to the point of no return. This is primarily why the progression of these diseases are “slow”. It also is (unfortunately) why finding a way to treat this class of diseases is so difficult.
“Our study found that by introducing an inhibitor of the STAT3 protein in repeated cycles, we could alternately replenish the pool of satellite cells and promote their differentiation into muscle fibers,” said Alessandra Sacco, Ph.D., assistant professor. “Our results are important because the process works in mice and in human muscle cells.”
“Our next step is to see how long we can extend the cycling pattern, and test some of the STAT3 inhibitors currently in clinical trials for other indications such as cancer, as this could accelerate testing in humans,” added Sacco.
“These findings are very encouraging. Currently, there is no cure to stop or reverse any form of muscle-wasting disorders—only medication and therapy that can slow the process,” said Vittorio Sartorelli, M.D., chief of the Laboratory of Muscle Stem Cells and Gene Regulation. “A treatment approach consisting of cyclic bursts of STAT3 inhibitors could potentially restore muscle mass and function in patients, and this would be a very significant breakthrough.”
STAT3 (signal transducer and activator of transcription 3) is a protein that activates the transcription of genes in response to IL-6, a signaling protein released by cells in response to injury and inflammation. Prior to the study, scientists knew that STAT3 played a complex role in skeletal muscle, promoting tissue repair in some instances and hindering it in others. But the precise mechanism of how STAT3 worked was a mystery.
The research team first used normally aged mice and mice models of a form of muscular dystrophy that resembles the human disease to see what would happen if they were given a drug to inhibit STAT3. They found that the inhibitor initially promoted satellite-cell replication, followed by differentiation of the satellite cells into muscle fibers. When they injected the STAT3 inhibitor every seven days for 28 days, they found an overall improvement in skeletal-muscle repair, and an increase in the size of muscle fibers.
“We were pleased to find that we achieved similar results when we performed the experiments in human muscle cells,” said Sacco. “We have discovered that by timing the inhibition of STAT3—like an “on/off” light switch—we can transiently expand the satellite-cell population followed by their differentiation into mature muscle cells.”
I don’t really want to hold my breath for this research to go to clinical trials, after all this wouldn’t be the first time research into muscle wasting has provided some new advancement. Fingers crossed that this research will pan out and actually provide something useful to people suffering with these diseases. In any case, it never hurts to hope!
Vittorio Sartorelli, & Alessandra Sacco (2014). STAT3 signaling controls satellite cell expansion and skeletal muscle repair Nature Medicine : 10.1038/nm.3656