Gene Therapy Reverses Genetic Mutation Responsible for Heart Failure in Muscular Dystrophy
Heart Failure Treatment
Study conducted in hamsters with same genetic defect as human muscular dystrophy shows great promise for treating adult heart failure.
University of Pittsburgh investigators have for the first time used gene therapy to successfully treat heart failure and other degenerative muscle problems in an animal model that is genetically susceptible to a human muscular dystrophy. Reporting in the Oct. 25 edition of the journal Circulation, the authors say that this is the first successful attempt to deliver a therapeutic gene throughout the body.
"Previous attempts at systemic gene therapy for muscle have not been very effective because blood vessel capillaries act much like a mosquito net, blocking the gene drugs from reaching the muscle cells. Fortunately, we found a virus that is just small and sneaky enough to get through this net and deliver the therapeutic gene to both skeletal and cardiac muscle cells," said lead author, Xiao Xiao, Ph.D., associate professor of orthopaedic surgery at the University of Pittsburgh School of Medicine.
The virus used by Dr. Xiao and his colleagues for delivering the corrective gene is known as adeno-associated virus, or AAV, a class of relatively small viruses that do not cause any known disease. In earlier studies, Dr. Xiao's team found that direct intramuscular injection of AAV was effective in transferring a gene into muscle cells in a fairly wide area around the injection site. However, for gene therapy treatments to be successful, particularly for muscular dystrophies where many organs and tissues are affected throughout the body, intramuscular injection is not practical for delivering a corrective gene to the body's more than 600 muscle groups.
Recently, Dr. Xiao's team demonstrated that a type of AAV, known as AAV-8, is particularly efficient at penetrating the capillary barrier, making it a good candidate for whole-body gene delivery. In this study, they tested AAV-8 in an animal model of human muscular dystrophy called limb girdle muscular dystrophy, or LGMD. In human LGMD, defects in a muscle cell membrane protein known as delta-sarcoglycan lead to severe damage and weakness to muscles, particularly around the hips and shoulders