Date of Award

January 2019

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Jeffrey R. Bender

Abstract

Myocardial infarction (MI), a leading cause of mortality worldwide, results in the injury and consequent loss of cardiomyocytes, which have a limited ability to regenerate. Healing post-MI therefore depends highly on the resulting inflammatory response, in which macrophages play a critical role due to their ability to mediate both tissue injury and repair. The mammalian heart contains at least two major macrophage subsets. Embryonic-derived, tissue-resident cardiac macrophages, originating primarily from the fetal liver (FLDMs), seed the heart during neonatal development and persist throughout the adult lifetime. In contrast, adult bone marrow-derived macrophages (BMDMs) are recruited to the heart following an acute perturbation. Functional differences between these cell subsets have been described by total RNA analyses, which correlate only partially with protein levels due to dynamic post-transcriptional regulation by miRNAs and RNA-binding proteins such as HuR. We hypothesize that, following hypoxia in vitro, which partially assimilates ischemia in vivo, BMDMs are pro-inflammatory and promote injury, while FLDMs are anti-inflammatory and promote favorable repair and remodeling. To elucidate the molecular basis underlying these distinct functions, we employed translating ribosome affinity purification (TRAP), a novel translational profiling approach, to isolate intact, macrophage-specific polysomal RNA from murine BMDMs and FLDMs after hypoxia, and then performed TRAP-seq. Differential gene expression and gene ontology analyses identify a pro- inflammatory, hypoxia-induced translational signature for BMDMs, associated with C5ar1, Clcf1 and P2ry2, and an anti-inflammatory translational profile for FLDMs, associated with Acod1 and Adm. We also reveal insights into the HuR-dependent hypoxic-induction of these transcripts. Our data identifies potential targets for RNA-based therapeutics and provides a foundation for future experiments seeking to define a comparative translational profile for adult and tissue-resident cardiac macrophages in vivo following MI.

Comments

This thesis is restricted to Yale network users only. This thesis is permanently embargoed from public release.

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