AAV CRISPR editing rescues cardiac and muscle function for 18 months in dystrophic mice

Adeno-associated virus-mediated (AAV-mediated) CRISPR editing is a revolutionary approach for treating inherited diseases. Sustained, often life-long mutation correction is required for treating these diseases. Unfortunately, this has never been demonstrated with AAV CRISPR therapy.

The authors addressed this question in the mdx model of Duchenne muscular dystrophy (DMD). DMD is caused by dystrophin gene mutation. Dystrophin deficiency leads to ambulation loss and cardiomyopathy.

They treated 6-week-old mice intravenously and evaluated disease rescue at 18 months. Surprisingly, nominal dystrophin was restored in skeletal muscle. Cardiac dystrophin was restored, but histology and hemodynamics were not improved. To determine the underlying mechanism, the authors evaluated components of the CRISPR-editing machinery. Intriguingly, they found disproportional guide RNA (gRNA) vector depletion. To test whether this is responsible for the poor outcome, they increased the gRNA vector dose and repeated the study.

This strategy significantly increased dystrophin restoration and reduced fibrosis in all striated muscles at 18 months. Importantly, skeletal muscle function and cardiac hemodynamics were significantly enhanced. Interestingly, they did not see selective depletion of the gRNA vector after intramuscular injection. These results suggest that gRNA vector loss is a unique barrier for systemic AAV CRISPR therapy. This can be circumvented by vector dose optimization.

 

Hakim CH, Wasala NB, Nelson CE, Wasala LP, Yue Y, Louderman JA, Lessa TB, Dai A, Zhang K, Jenkins GJ, Nance ME, Pan X, Kodippili K, Yang NN, Chen SJ, Gersbach CA, Duan D. AAV CRISPR editing rescues cardiac and muscle function for 18 months in dystrophic mice JCI Insight. 2018 Dec 6;3(23). pii: 124297. doi: 10.1172/jci.insight.124297. [Epub ahead of print]