Date of Award

2017

Degree Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Washkewicz College of Engineering

First Advisor

Ramamurthi, Anand

Subject Headings

Biomedical Engineering

Abstract

Abdominal aortic aneurysms (AAA) are localized expansions of the aorta wall that continue to grow until they reach a critical size and fatally rupture. This growth is driven by the chronic disruption, degradation, and subsequent loss of aortal wall elastic fibers by matrix metalloproteinases (MMPs) secreted by inflammatory cells recruited to the aorta wall following an injury stimulus, and the inherent inability of vascular smooth muscle cells (SMCs) to naturally repair or regenerate elastic fibers. This leads to a net loss of elastic matrix and the continuing weakening of the aortal wall until eventual rupture. Current treatments seek to reinforce the vessel wall with grafts or stents, but do not arrest or reverse AAA growth. Therefore, inhibiting the proteolytic degradation of the elastic matrix while also stimulating elastic matrix neoassembly is needed to stop AAA growth and regenerate the vessel wall. We have previously shown utility of doxycycline (DOX), an MMP inhibitor drug, to stimulate elastic matrix neoassembly and crosslinking at low µg/ml doses in addition to inhibiting MMPs. We currently show in aneurysmal SMC cultures, that effects of exogenous DOX in this dose range are linked to its upregulation of transforming growth factor beta (TGF-ß1) via its inhibition of the regulatory protein c-Jun-N-terminal kinase isoform 2 (JNK 2). We have identified a DOX dose range that stimulates elastogenesis and crosslinking without adversely impacting cell viability. Using JNK 2 inhibition as a metric for pro-regenerative matrix effects of DOX, we further demonstrate that sustained, steady state release of DOX at the useful dose, from poly(ethylene glycol)-poly(lactic glycolic acid) nanoparticles (NPs) provides pro-elastogenic and anti-proteolytic effects that could potentially be more pronounced than that of exogenous DOX. We attribute these outcomes to previously determined synergistic effects provided by cationic amphiphile groups functionalizing the polymer NP surface. Released DOX inhibited expression and phosphorylation of JNK to likely increase expression of TGF-ß1, which is known to increase elastogenesis and lysyl oxidase-mediated crosslinking of elastic matrix. Our results suggest that JNK inhibition is a useful metric to assess pro-elastic matrix regenerative effects and point to the combinatorial regenerative benefits provided by DOX and cationic-functionalized NPs.

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