Angiopoietin 1 Attenuates Dysregulated Angiogenesis in the Gastrocnemius of DMD Mice

Duchenne muscular dystrophy (DMD) is a degenerative neuromuscular disease caused by a lack of functional dystrophin. Ang 1 paracrine signalling maintains the endothelial barrier of blood vessels, preventing plasma leakage. Chronic inflammation, a consequence of DMD, causes endothelial barrier dysfunction in skeletal muscle. We aim to elucidate changes in the DMD mouse's gastrocnemius microvascular niche following local administration of Ang 1. Gastrocnemii were collected from eight-week-old mdx/utrn+/- and healthy mice. Additional DMD cohort received an intramuscular injection of Ang 1 to gastrocnemius and contralateral control. Gastrocnemii were collected for analysis after two weeks. Using immunohistochemistry and real-time quantitative reverse transcription, we demonstrated an abundance of endothelial cells in DMD mouse's gastrocnemius, but morphology and gene expression were altered. Myofiber perimeters were shorter in DMD mice. Following Ang 1 treatment, fewer endothelial cells were present, and microvessels were more circular. Vegfr1, Vegfr2, and Vegfa expression in Ang 1-treated gastronemii increased, while myofiber size distribution was consistent with vehicle-only gastrocnemii. These results suggest robust angiogenesis in DMD mice, but essential genes were underexpressed-furthermore, exogenous Ang 1 attenuated angiogenesis. Consequentially, gene expression increased. The impact must be investigated further, as Ang 1 therapy may be pivotal in restoring the skeletal muscle microvascular niche.