Gene therapy treats muscular dystrophy in dogs

"This discovery took our research team more than 10 years, but we believe we are on the cusp of having a treatment for the disease," says Dongshen Dua. (Credit: "boy and dog" via Shutterstock)

Researchers have successfully treated dogs with Duchenne muscular dystrophy (DMD) and say that human clinical trials are being planned in the next few years.

Muscular dystrophy, which affects approximately 250,000 people in the US, occurs when damaged muscle tissue is replaced with fibrous, fatty or bony tissue and loses function.

“This is the most common muscle disease in boys, and there is currently no effective therapy,” says study leader Dongsheng Duan, professor in medical research at the University of Missouri School of Medicine. “This discovery took our research team more than 10 years, but we believe we are on the cusp of having a treatment for the disease.”

Patients with Duchenne muscular dystrophy have a gene mutation that disrupts the production of a protein known as “dystrophin.” Absence of dystrophin starts a chain reaction that eventually leads to muscle cell degeneration and death. Affected boys lose their ability to walk and breathe as they get older.

Dystrophin also is one of the largest genes in the human body. “Due to its size, it is impossible to deliver the entire gene with a gene therapy vector, which is the vehicle that carries the therapeutic gene to the correct site in the body,” Duan says. “Through previous research, we were able to develop a miniature version of this gene called a microgene. This minimized dystrophin protected all muscles in the body of diseased mice.”

However, it took the team more than 10 years to develop a strategy that can safely send the micro-dystrophin to every muscle in a dog that is afflicted by the disease. The dog has a body size similar to that of an affected boy. Success in dogs will set the foundation for human tests.

In this latest study, the team demonstrates for the first time that a common virus can deliver the microgene to all muscles in the body of a diseased dog. The dogs were injected with the virus when they were two to three months old and just starting to show signs of DMD. The dogs are now six to seven months old and continue to develop normally.

[Muscular dystrophy affects 1 in 5,000 U.S. boys]

“The virus we are using is one of the most common viruses; it is also a virus that produces no symptoms in the human body, making this a safe way to spread the dystrophin gene throughout the body,” Duan says.

“These dogs develop DMD naturally in a similar manner as humans. It’s important to treat DMD early before the disease does a lot of damage as this therapy has the greatest impact at the early stages in life.”

The technology used to create the gene-therapy has been licensed by Solid GT, LLC.

The journal Human Molecular Genetics published the study, which the Department of Defense, Jesse’s Journey-The Foundation for Cell and Gene Therapy, the National Institutes of Health, Hope for Javier, the Kansas City Area Life Sciences Institute and the University of Missouri supported. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

Source: University of Missouri