Date of Award

1-1-2016

Embargo Period

1-1-2019

Document Type

Dissertation - MUSC Only

Degree Name

Doctor of Philosophy (PhD)

Department

Medicine

College

College of Graduate Studies

First Advisor

Dhandapani Kuppuswamy

Second Advisor

Amy Bradshaw

Third Advisor

Kristi L. Helke

Fourth Advisor

Robin C. Muise-Helmericks

Fifth Advisor

Terrence X. O'Brien

Abstract

Heart failure (HF) is one of the leading causes of morbidity and morality in the world. It is stimulated in various ways, with one of the major stimuli being hypertension. This disease stimulates pathological hypertrophy characterized by abnormal myocardial remodeling: increased cardiomyocyte growth and fibrosis. This dissertation primarily examines how caveolin-1 impacts pathological hypertrophy and ventricular function following pressure overload (PO). Low caveolin-1 expression has been reported to correlate with the development of fibrosis. Caveolin-1 scaffolding domain (CSD) peptide is able to mimic the activity of caveolin-1 and reverse fibrotic disease. In a transverse aortic constriction (TAC) murine model of PO, CSD is able to reduce extracellular matrix accumulation (ECM) measured by the expression of collagen and one of its chaperone proteins, heat shock protein 47 (HSP47). Treatment with CSD also improved ventricular function and geometry associated with heart failure. Fibrosis is encouraged by the activity of (myo)fibroblasts. Upon injury bone marrow cells (BMCs) migrate to the target tissue and become fibrocyctes, cells expressing the monocyte marker CD45 and the mescenchymal marker, collagen. In our model of PO, we have seen increased fibrocyte levels as measured by CD45, collagen I, HSP47 and alpha smooth muscle actin (ASMA) expression. CSD treatment is able to decrease the fibrocycte population seen in PO mice. To further understand the mechanisms behind pathological remodeling we investigated integrins, specifically beta3 (β3) integrin. ix Beta3 integrin has been previously reported to have a role in cardiomyocyte growth and survival and fibrosis. Whereas a germline knockout of β3 integrin (β3-/-) has been readily used in scientific investigation, a cell specific deletion model has not been explored in any species. Therefore, we created cell specific β3 integrin knockout mice for the two major cell types of the heart, cardiomyocytes and fibroblasts. A doxycycline inducible cardiomyocyte β3-/- mouse was made, using the cardiac specific promoter, cardiac troponin T (cTnT) and fibroblast specific β3 integrin knockout mice (constitutive and tamoxifen (Tam) inducible) were made using the following promoters: fibroblast specific protein (FSP1) and collagen type 1 alpha 2 (Col1α2). Biochemical analyses demonstrated successful deletion in all models; however, issues with inducibility and reproducibility emerged. The information presented within this dissertation has identified (1) caveolin-1 as a therapeutic target for reversing cardiac hypertrophy and (2) cell specific knockout mouse models as critical tools for parsing out mediators of cardiac remodeling, specifically β3 integrin.

Rights

All rights reserved. Copyright is held by the author.

Download

Share

COinS