Duchenne muscular dystrophy (DMD) is a fatal, muscle-wasting disorder due to mutations/deletions in the dystrophin gene. Whilst improvements in palliative care have increased the life expectancy of patients, cardiomyopathy and respiratory complications are still the leading causes of death. A potential therapy for the treatment of DMD is antisense oligonucleotides (AOs), which modulate dystrophin pre-mRNA splicing to restore the dystrophin reading frame and generate a truncated functional protein. Conjugation of AOs to cell penetrating peptides (CPP), such as Pip5e-, significantly improves delivery to skeletal muscles and to the heart, which is imperative given the impact of cardiomyopathy to mortality. However, it should be noted that the contribution of skeletal muscles, such as the core respiratory muscle, the diaphragm, in dystrophic cardiopulmonary function is poorly understood. The specific aims of the work in this thesis were to (i) understand the effect of the diaphragm on cardiac function using magnetic resonance imaging (MRI), (ii) screen a number of derivatives of Pip5e (Pip6) in an effort to discover further promising peptides and define the properties integral to heart penetrating capacity, and (iii) assess whether Pip6-PMOs restore cardiac function (MRI) following a repeat, low dose regimen. In short, the specific restoration of dystrophin in the diaphragm of the dystrophic mouse model, the mdx mouse, did not improve cardiac function, highlighting the importance of a body-wide therapy. The screening of multiple Pip5e-PMO derivatives revealed 3 promising peptides with improved cardiac splicing capacity; however, serial deletions of amino acids from the central core resulted in the diminution of dystrophin restoration, possibly due to a reduction in hydrophobicity. Finally, the Pip6-PMO treatment regimen substantially restored dystrophin protein (28% in heart) and stabilised cardiac function, even with an increased work load. In conclusion, this study illustrates the importance of a body-wide treatment, such as the CPP strategy (Pip-PMO). These Pip-PMO conjugates demonstrate high dystrophin restoration in a number of muscles, including cardiac muscle, and have a beneficial effect on cardiac function.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:635272 |
| Date | January 2014 |
| Creators | Betts, Corinne A. |
| Contributors | Wood, Matthew J. A.; Hammond, Suzan M. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:545d586a-ad7b-4089-8537-b2677957b874 |
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