Protein that boosts growth of damaged muscle tissue identified: study

Washington: Scientists have identified a key protein that can boost the growth of damaged muscle tissue, a breakthrough that may lead to treatment for muscle degeneration caused by old age and diseases such as muscular dystrophy.

Researchers at the Johns Hopkins University found that the protein called integrin is present on the stem cell surface and used by stem cells to interact with, or "sense" their surroundings.

How stem cells sense their surroundings, also known as the stem cell "niche," affects how they live and last for regeneration, researchers said.

The presence of the protein beta one-integrin was shown to help promote the transformation of those undifferentiated stem cells into muscle after the tissue has degraded, and improve regenerated muscle fibre growth as much as 50 per cent.

While the presence of beta one-integrin in adult stem cells is apparent, its role in these cells has not been examined, especially its influence on the biochemical signals promoting stem cell growth, researchers said.

The experiment shows that beta one-integrin - one of 28 types of integrin - maintains a link between the stem cell and its environment, and interacts biochemically with a growth factor called fibroblast growth factor (FGF) to promote stem cell growth and restoration after muscle tissue injury.

Aged stem cells do not respond to FGF, and the results also show that beta one-integrin restores aged stem cell's ability to respond to FGF to grow and improve muscle regeneration.

By tracking an array of proteins inside the stem cells, researchers tested the effects of removing beta one-integrin from the stem cell.

This is based on the understanding that the activities of stem cells are dependent on their environment and supported by the proteins found there.

"If we take out beta one-integrin, all these other proteins are gone," said Chen-Ming Fan, a professor at the Carnegie Institution for Science.

Why that is the case is not clear, but the experiment showed that without beta one-integrin, stem cells could not sustain growth after muscle tissue injury.

By examining beta one-integrin molecules and the array of proteins that they used to track stem cell activity in aged muscles, researchers found that all of these proteins looked like they had been removed from aged stem cells.

They injected an antibody to boost beta one-integrin function into aged muscles to test whether this treatment would enhance muscle regeneration.

Measurements of muscle fibre growth with and without boosting the function of beta one-integrin showed that the protein led to as much as 50 per cent more regeneration in cases of injury in aged mice.

When the same beta one-integrin function-boosting strategy was applied to mice with muscular dystrophy, the muscle was able to increase strength by about 35 per cent.

The findings appear in the journal Nature Medicine.