Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common hereditary muscular disease among children, often forcing victims into the wheelchair before the age of twelve and reducing life expectancies. A tailored pig model for DMD was instrumental for the development of a gene therapy that may provide relief for those suffering from DMD. The same model has recently been for validating a novel non-invasive procedure for monitoring disease progression.

Duchenne muscular dystrophy (DMD) is the most common lethal inherited X-chromosomal muscular disease, occurring in one of 3,800–6,000 live male births. DMD is caused by loss-of-function mutations in the DMD gene (ca. 2.5 Mb, 79 exons) that lead to a shift in its reading frame, out-of-frame transcripts and loss of the essential muscle cytoskeletal protein dystrophin. The hotspots for mutations are in the regions of exons 3–7 and of exons 45–55. DMD is characterized by progressive muscle weakness and wasting: patients present first symptoms before the age of 5 years, lose ambulation around the age of 12 years and die of respiratory or heart failure in the second to fourth decade of life. The mdx mouse is the most widely used animal model for DMD and has been instrumental to understand the pathophysiology of DMD and to develop therapeutic strategies, such as exon skipping and editing. However, the mdx mouse does not develop severe muscular dystrophy. To to its small size, delivery parameters of drugs or viral vectors are difficult to extrapolate to human patients.

The group of Eckhard Wolf developed a porcine DMD model resembling a frequent human DMD mutation (loss of exon 52) and biochemical, clinical and pathological features of the human disease. In an interdisciplinary research team with scientists at TUM and HMGU, the group has for the first time succeeded in correcting the mutated DMD gene in living pigs. Using CRISPR/Cas delivered intramuscularly by adeno-associated viral vectors (AAV9-Cas9-gE51), DMD exon 51 was additionally deleted, resulting in expression of a shortened dystrophin (DMDΔ51–52) and improved skeletal muscle function. Moreover, systemic application of AAV9-Cas9-gE51 led to widespread dystrophin expression in muscle, including diaphragm and heart, prolonging survival and reducing arrhythmogenic vulnerability. The ability of Cas9-mediated exon excision to improve DMD pathology in this clinically severe large animal model paves the way for new treatment approaches in patients with this devastating disease. The new findings have just been published in the journal Nature Medicine (Moretti et al. Nat Med 2020).
The same pig model has recently been used to validate detection of collagens by multispectral optoacoustic tomography as an imaging biomarker for progression of DMD (Regensburger et al. Nat Med 2019).

Original Publication:

Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy.
Moretti A, Fonteyne L, Giesert F, Hoppmann P, Meier AB, Bozoglu T, Baehr A, Schneider CM, Sinnecker D, Klett K, Fröhlich T, Rahman FA, Haufe T, Sun S, Jurisch V, Kessler B, Hinkel R, Dirschinger R, Martens E, Jilek C, Graf A, Krebs S, Santamaria G, Kurome M, Zakhartchenko V, Campbell B, Voelse K, Wolf A, Ziegler T, Reichert S, Lee S, Flenkenthaler F, Dorn T, Jeremias I, Blum H, Dendorfer A, Schnieke A, Krause S, Walter MC, Klymiuk N, Laugwitz KL, Wolf E*, Wurst W*, Kupatt C*.  Nature Medicine 2020 Jan 27. https://doi.org/10.1038/s41591-019-0738-2 [Epub ahead of print]

Reference:

Detection of collagens by multispectral optoacoustic tomography as an imaging biomarker for Duchenne muscular dystrophy.
Regensburger AP, Fonteyne LM, Jüngert J, Wagner AL, Gerhalter T, Nagel AM, Heiss R, Flenkenthaler F, Qurashi M, Neurath MF, Klymiuk N, Kemter E, Fröhlich T, Uder M, Woelfle J, Rascher W, Trollmann R, Wolf E, Waldner MJ, Knieling F.  Nat Med. 2019 Dec;25(12):1905-1915.