Duchenne muscular dystrophy (DMD) is a particularly nasty rare and fatal disease. It predominantly affects boys, slowly robbing them of their ability to control their muscles. By 10 years of age, boys with DMD start to lose the ability to walk; by 12, most need a wheelchair to get around. Eventually they become paralyzed, and need round-the-clock care.
There are no effective long-term treatments and the average life expectancy is just 25.
DMD Research team: Photo courtesy Ottawa Hospital Research Inst.
But now researchers in Canada have made a discovery that could pave the way to new approaches to treating DMD. In a study published in the journal Nature Medicine, they show that DMD is caused by defective muscle stem cells.
In a news release Dr. Michael Rudnicki, senior author of the study, says this discovery is completely changing the way they think about the condition:
“For nearly 20 years, we’ve thought that the muscle weakness observed in patients with Duchenne muscular dystrophy is primarily due to problems in their muscle fibers, but our research shows that it is also due to intrinsic defects in the function of their muscle stem cells. This completely changes our understanding of Duchenne muscular dystrophy and could eventually lead to far more effective treatments.”
Loss and confused
DMD is caused by a genetic mutation that results in the loss of a protein called dystrophin. Rudnicki and his team found that without dystrophin muscle stem cells – which are responsible for repairing damage after injury – produce far fewer functional muscle fibers. The cells are also confused about where they are:
“Muscle stem cells that lack dystrophin cannot tell which way is up and which way is down. This is crucial because muscle stem cells need to sense their environment to decide whether to produce more stem cells or to form new muscle fibers. Without this information, muscle stem cells cannot divide properly and cannot properly repair damaged muscle.”
While the work was done in mice the researchers are confident it will also apply to humans, as the missing protein is almost identical in all animals.
The researchers are already looking for ways they can use this discovery to develop new treatments for DMD, hopefully one day turning it from a fatal condition, to a chronic one.
Dr. Ronald Worton, the co-discoverer of the DMD gene in 1987, says this discovery has been a long-time coming but is both welcome and exciting:
“When we discovered the gene for Duchenne muscular dystrophy, there was great hope that we would be able to develop a new treatment fairly quickly. This has been much more difficult than we initially thought, but Dr. Rudnicki’s research is a major breakthrough that should renew hope for researchers, patients and families.”
In this video CIRM grantee, Dr. Helen Blau from Stanford University, talks about a new mouse model created by her lab that more accurately mimics the Duchenne symptoms observed in people. This opens up opportunities to better understand the disease and to develop new therapies.