Juline Deppen

BME PhD Defense Presentation

Date: 2023-01-12
Time: 10:30AM
Location / Meeting Link: Emory University Hospital, Hurst Conference Room E450; https://emory.zoom.us/j/98765411167

Committee Members:
Rebecca D. Levit, MD (Advisor); Luke P. Brewster, MD, PhD; Zhiyong Lin, PhD; John N. Oshinski, PhD; Krishnendu Roy, PhD


Title: A Cellular Therapeutic Strategy for Peripheral Artery Disease in a Swine Model of Limb Ischemia

Abstract:
Peripheral artery disease (PAD) remains a significant age-related disease. PAD is caused by the narrowing or obstruction of lower limb arteries and elicits distinct skeletal muscle adaptations. Cell therapies have been pursued to restore blood flow to the ischemic muscle and prevent amputation; however, clinical trial benefits have been modest with heterogeneous study designs and limited injected cell persistence. Small animal evaluation of PAD cell therapies does not permit scaling to humans nor the implementation of clinical techniques and outcomes. Alginate-encapsulated mesenchymal stromal cells (eMSCs) exhibit high retention and promote paracrine vascular generation in murine hind limb ischemia (HLI). In this thesis, we aimed to facilitate the bench-to-bedside translation of effective PAD cell therapies, including eMSCs, by enabling assessment on a human scale with investigation into muscle-specific outcomes. We first determined the optimal pelvic arterial ligation strategy to produce sustained HLI in swine. Objectively assessed walking dysfunction, adenosine-induced hyperemic muscle perfusion deficits, depressed limb blood pressure, macrovascular remodeling, and myopathy were successfully quantified after 6 weeks in a triple ligation porcine HLI model. We adapted a novel, non-invasive tracking strategy translatable to large animals and humans to PAD cell therapies. Swine eMSC viability and retention were longitudinally visualized in rodent hind limbs via positron emission tomography (PET). We next created an in vitro model of myotube ischemia that recapitulated features of both clinical PAD and our swine HLI model, utilizing it to examine muscle-specific MSC secretome benefits. Finally, we performed a pilot study of eMSC efficacy in porcine HLI. Intramuscular administration of autologous eMSCs significantly improved microvascular perfusion and gross muscle atrophy while normalizing limb dysfunction compared to empty alginate capsules. eMSC delivery was also associated with trending benefits in collateralization, local neovascularization, and muscle fibrosis. The porcine HLI, cell tracking, and in vitro muscle ischemia platforms in this dissertation could be utilized in concert for greater preclinical evaluation of novel PAD treatments. Optimization and evaluation on a human scale with a greater understanding of end-organ mechanisms can facilitate more meaningful and effective clinical trials. Prolonging cellular therapy persistence and/or exploiting their secretory effects, such as through alginate encapsulation, is a promising strategy for multifactorial limb benefits in PAD.