Stem cells find a way to repair damaged muscles

When a muscle is injured, it will give out signals a dormant, mature stem cell called a satellite cell to "wake up" and begin repairing it. Scientists at the university of Missouri have found that even if the satellite cells are far away from the injured muscle, there are guides for the stem cells to travel through the muscle tissue to help repair the damage. The findings could lead to more effective new treatments for diseases such as muscular dystrophy.

In the experiment, the researchers coated a sheet of glass with narrow "streaks" made of different proteins and then used a time-lapse microscope to track the movement of the satellite cells along the "streaks". They found that several subtypes of a protein called ephrin had the same effect on the satellite cells, which turned and changed direction as soon as they touched the stripes made by ephrin. "The stem cells act like a blindfolded person walking down a aisle," Nathan connery explains, associate professor of biological sciences at the university of Missouri college of arts and sciences and a researcher at the bond center for life sciences. "they sense the path by touching a wall like a person. These proteins are found on the surface of long, parallel muscle fibers, which help satellite cells travel in a more straight line to the distance that sends a distress signal.

The experiment also found that using the stripes to signal the satellite cells differently allowed them to line up in parallel to form the muscle fibers found in living tissue, which had never been done in a dish before. The researchers believe that the ephrin may regulate several different steps necessary to move from the satellite cells' departure from the stem cell population to the distribution of all muscle cells to the formation of new, organized and well-defined fibers. These steps are essential.

Patients with human muscular dystrophy, whose muscles are vulnerable to injury, would need about 100 injections of stem cells per square centimetre, compared with about 4,000 for a single muscle, according to current treatments. 'if we understand how normal satellite cells travel within tissues, we can use that information clinically to change the way we inject them and find more effective treatments,' Dr. Conelison said.
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