Duchenne Muscular Dystrophy (DMD) is a progressive disorder in which the absence of the dystrophin protein results in loss of the dystrophin bridge at the muscle membrane. Recent work demonstrates the involvement of dystrophin in blood flow regulation, which is disturbed in DMD and causes increased muscle damage. However, the importance of angiogenesis in DMD treatment has not yet been well addressed. We propose that administration of pro-angiogenic factors can restore muscle fibers and blood vessels. To reveal the relationship between neuromuscular disease and angiogenesis, we recently created Flt-1 heterozygous mdx mice (mdx:Flt- 1+/-). mdx mice serve as a model for DMD, and vascular endothelial growth factor (VEGF) binds with Flt-1 receptors to negatively regulate angiogenesis. Recently, our work revealed that the mdx:Flt-1+/- mice display an increased number of blood vessels in addition to improved muscle pathology and function (Verma et al., 2010). Utrophin deficient mdx mice (mdx:utrn-/-) display a more severe phenotype than mdx mice, and the mdx:utrn-/- mice more closely resemble a human DMD phenotype. Importantly, mdx:utrn-/-:Flt-1+/- triple mutant mice display improved muscle histology and significantly higher survival rates compared to mdx:utrn-/-:Flt-1+/+ mice. Our project will build on these preliminary data to more closely reveal how increased angiogenesis ultimately affects the DMD phenotype in mdx mice. In addition, we will examine whether increased vasculature provided by the administration of an anti-Flt-1 peptide or shRNA for Flt-1 that block Flt-1 function can improve the muscular dystrophic phenotype in mdx and mdx:utrn-/- mice.
Project Narrative Duchenne Muscular Dystrophy (DMD) is caused by mutations in the dystrophin gene, which normally functions to maintain muscle membrane integrity and prevent contraction-induced damage. It may be possible to reduce muscle fiber damage by using pro-angiogenic factors to increase the number of blood vessels and observe the resultant effects on the muscular dystrophy phenotype. We predict that these pro-angiogenic factors will assist development of new therapies for DMD via increased vascular density in blood starved dystrophic muscles.
