Research Project
10187852
Abstract Peripheral artery disease (PAD) is caused by atherosclerosis of the peripheral arteries, most commonly in the lower extremities, and affects 8-12 million individuals in the U.S. Cilastozol was the last drug approved to treat patients with PAD (1999) and twenty years of trials and pre-clinical testing have failed to advance therapeutics. PAD presents as either intermittent claudication (IC; pain with exertion that is relieved with rest) or critical limb ischemia (CLI; pain at rest with or without tissue necrosis or gangrene). Although less common than IC, CLI carries a substantially higher morbidity and mortality; CLI patients have a risk of major amputation or death that approaches 40% in one year. Differences in the clinical course of IC and CLI together with results of recent pre- clinical studies raise the intriguing possibility that IC and CLI represent distinct phenotypic manifestations of the same disease process. We propose an innovative idea; regenerating and functionally competent skeletal muscle supports ischemic neovascularization and vessel maturation - ultimately leading to the recovery of tissue blood flow and the prevention of tissue loss. Our proposal will directly test the ability of ischemic cells in the local limb microenvironment to alter tissue outcomes. We will interrogate the role of human BAG3 (Bcl-2 associated athanogene 3 - an evolutionarily conserved 575 amino acid protein) specifically in the limb muscle and endothelial cells of patients and mice. BAG3 is a multifunctional scaffolding protein and co-chaperone with pleiotropic effects in heart and skeletal muscle. It is a promising genetic candidate for therapeutic development in PAD for the following reasons: 1) mutations in BAG3 cause muscle myofibrillar myopathy and dilated cardiomyopathy in humans, 2) BAG3 variants exist in both African Americans with CLI (a demographic disproportionately affected by PAD - Preliminary Data) and cardiomyopathy, and 3) a murine coding variant in BAG3 regulates muscle regeneration, vascular density, and limb survival in a pre-clinical model of PAD (hindlimb ischemia-HLI). To that end, this proposal brings together clinical vascular surgeons, a skeletal muscle biologist who focuses on physiologic outcome measures, a biochemist and mitochondrial biologist who focuses on interrogating mitochondrial form and function in disease, a clinical cardiologist and researcher, and a translational scientist who studies skeletal muscle adaptability to injury and endothelial cell biology and has developed an unparalleled biobank of human PAD tissues. The central hypothesis of this proposal states that genetic variants in BAG3 result in myopathy and mitochondriopathy that disrupts communication between muscle and endothelial cells and results in a local muscle environment insufficient to support the vasculature. To that end, the Specific Aims are: 1) In PAD relevant models, determine the functional link between ischemic myopathy and angiogenesis. 2) Determine whether Cox6a2 expression is sufficient to rescue BAG3 variant induced myopathy in PAD conditions. 3) Establish whether BAG3 variants are a link between AA race and differences in CLI patient outcomes.
