New Hope for Muscular Dystrophy

Gene Therapy Effectively Treats Muscular Dystrophy in Dogs

By Meghan Kurz

Purpose of This Assignment

The purpose of this assignment is to learn about new genetic research and findings that are working toward improvement and understanding of disease processes and improvement of health care. There is much that is not yet understood with genetics and this generation of researchers and health care providers are learning and exploring new and exciting information regarding genetics every day.

What is muscular dystrophy?

The most common form of muscular dystrophy is called Duchenne muscular dystrophy. DMD is a sex-linked recessive genetic disorder caused by a mutation in an allele for the gene that codes for dystrophin. "Dystrophin is a structural protein that functions to maintain muscle integrity." (Beery, T., & Workman, M, 2012, pg 194). When dystrophin is inactive or mutated, the muscles in the body (including skeletal, smooth, and cardiac muscle) are destroyed, presenting in the body with progressive muscular weakness. Damaged muscle tissue is replaced by fat, fibrous, or bony tissue, losing function. This genetic disorder most commonly affects males. This normally presents in young boys with difficulty maintaining balance and walking after having learned to walk. Falling occurs frequently. This genetic condition occurs in about 1 out of every 3,600 male infants. Due to progressive decreased muscle function, many of these children lose the ability to walk by age 12, and develop heart disease and breathing difficulties by age 20. Sadly, the lifespan of this disease is approximately 25-30 years.
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Genetics in the News

Gene Therapy Treatment Successful in Dogs with Muscular Dystrophy

Interestingly enough, it has been found that dogs can develop Duchenne Muscular Dystrophy (DMD) in the same fashion as the human body. Through the same alteration, deletion, or inactivity of dystrophin, canines are left with similar symptoms that are seen in boys with DMD. More than 10 years ago researchers were able to mimic dystrophin. However, dystrophin is one of the largest genes in the human (and canine) body, and it was impossible to transfer the created gene because it simply does not fit into a harmless virus or vector. A vector is defined as "any agent that acts as a carrier or transporter, as a virus or plasmid that conveys a genetically engineered DNA segment into a host cell. " (http://dictionary.reference.com/browse/vector) The therapy also needs to treat all muscles throughout the body, not just one single muscle or organ. This has also caused a set back.


For years, researchers at University of Missouri School of Medicine have worked to successfully creat a smaller, more compact version of the dystrophin gene (called an microgene). Previously, this microgene has successfully treated dystrophic mice. The most recent study has advanced to treating DMD in larger animals. "The research was funded in part by NIH’s National Heart, Lung, and Blood Institute (NHLBI). The study was published on October 15, 2015, in Human Molecular Genetics" (Torgan, Ph.D., 2015, paragraph 4).


Dr. Dongsheng Duan has lead a team at Missouri School of Medicine to deliver the gene therapy through a commonly used viral vector known as AAV-9. This viral vector does not create any symptoms or sickness in humans or canines. During their study, the researchers have delivered the dystrophin microgene through the vector to the blood stream of puppies with muscular dystrophy who have depressed immune systems.


The study found that the puppies tolerated the injections incredibly well. The gene therapy did not stunt growth at all. In addition, the researchers were able to detect dystrophin protein in several muscles in the puppies body, including the diaphragm, heart, and limbs for at least 4 months. The puppies' muscle tissue cells showed improvements as well. The dogs are now 6-8 months old and continue to develop within normal limitations.


There is still much to be researched, such as long term side effects and effectiveness in large mammals, but Duan says "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” (Torgan, Ph.D., 2015, paragraph 7).

Duchenne Muscular Dystrophy - Virus Delivers Microgene Therapy

Why are These Findings Important to Nurses

This can be useful in consideration with nursing because if we are capable of treatment of DMD or even just prolonging non-sedentary activities of daily living we may be able to make a patient's quality of life much richer. I will keep in mind that in the future, early diagnosis of this disease could potentially help with this child's life expectancy. If you catch this disease early enough and are capable in the future of starting this gene therapy, perhaps you can reverse or halt the dystrophy of muscles. This could help patient's continue walking and being active, but can also perhaps help with respiratory and cardiac disease related to this treatment. I will definitely continue to monitor and research this treatment as it becomes more well understood, and will always be an advocate of genetic testing for this particular illness, especially if I know there's hope on the horizon for the innocent victims of this malicious disease.

References

Basi, C. (2015, October 22). Gene Therapy Treats All Muscles in the Body in Muscular Dystrophy Dogs; Human Clinical Trials are Next Step. Retrieved November 15, 2015, from http://munews.missouri.edu/news-releases/2015/1022-gene-therapy-treats-all-muscles-in-the-body-in-muscular-dystrophy-dogs-human-clinical-trials-are-next-step/



Torgan, Ph.D., C. (2015, November 2). Gene therapy treats muscular dystrophy in dogs | National Institutes of Health (NIH). Retrieved November 15, 2015, from http://www.nih.gov/news-events/nih-research-matters/gene-therapy-treats-muscular-dystrophy-dogs



Basi, C. (2015, October 23). Gene therapy treats muscular dystrophy in dogs - Futurity. Retrieved November 15, 2015, from http://www.futurity.org/duchenne-muscular-dystrophy-dogs-1032682-2/



Beery, T., & Workman, M. (2012). Genetics and genomics in nursing and health care (1st ed.). Philadelphia, Pennsylvania: F.A. Davis.



vector. (n.d.). The Free On-line Dictionary of Computing. Retrieved November 15, 2015, from Dictionary.com website: http://dictionary.reference.com/browse/vector