Molecular Mechanisms of Intramuscular Adipose Tissue in Chronic Limb Threating Ischemia

University Of Florida, Gainesville FL

Investigators

Abstract

Abstract Chronic limb threatening ischemia (CLTI) is the most severe form of the atherosclerotic disease peripheral arterial disease (PAD). Unfortunately, there is only one approved therapy, Cilostazol, a mild vasodilatory agent, that modestly improves limb function in PAD patients, but is not widely used in CLTI patients. For CLTI patients, surgical interventions are commonly employed, but eventual limb amputation is still common evidenced by the ~45% amputation rate in the BEST-CLI trial. Several angiogenic therapies have been unsuccessful in clinical trials, suggesting that while improving limb blood flow should remain a primary treatment focus CLTI limb pathobiology involves pathological changes to other non-vascular cell types within the affected limb. In this regard, the replacement of skeletal muscle with intramuscular adipose tissue (IMAT) and fibrotic tissue is prominent in the CLTI population. However, it is not currently known how IMAT and fibrosis impact limb function in CLTI or whether therapeutic targeting of IMAT/fibrosis is a viable option. In this predoctoral fellowship proposal, I will test the hypothesis that IMAT contributes to the CLTI pathobiology by negatively impacting vessel growth and promoting muscle dysfunction. To test this hypothesis, I will employ rigorous genetic and pharmacologic approaches that either increase or decrease IMAT in mice subjected to femoral artery ligation (FAL). Considering that IMAT and fibrosis is believed to be formed by the differentiation of fibro-adipogenic progenitor cells (FAPs) that reside within the limb muscles, I will also perform experiments to define what drives this adipogenic conversion of FAPs in the CLTI condition. These experiments will leverage temporal single nuclei/cell RNA sequencing in mice with CLTI, as well as primary FAP cultures in hypoxia/normoxia to identify intercellular signaling molecules that drives FAP differentiation to IMAT and to define the secretome of FAPs which will allow me to explore how FAPs communicate with other cells in the CLTI limb. A detailed training program with strong mentorship that involves specific research skill enhancement in molecular genetics, stem- cell biology, and multi-omics, has been developed. I will receive additional career mentoring involving grant/manuscript writing, presentation skills, and professional development opportunities. Completion of this proposal will result in exceptional scientific and professional training which will provide a strong foundation for my career goals.