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Molecular Regulation of Collagen Deposition in the Extracellular Matrix of Cultured Ventricular Fibroblasts From Rainbow Trout, Oncorhynchus mykiss

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Title: Molecular Regulation of Collagen Deposition in the Extracellular Matrix of Cultured Ventricular Fibroblasts From Rainbow Trout, Oncorhynchus mykiss
Author: Johnston, Elizabeth
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: Gillis, Todd
Abstract: Rainbow trout remain active in temperate waters that annually fluctuate by ~16°C in temperature. This is impressive as vertebrate cardiac function is highly sensitive to temperature change. Trout are able to compensate for the detrimental effects of temperature on cardiac function by remodeling both the active (muscle) and passive (extracellular matrix, ECM) components of the myocardium. The extent to which rainbow trout are able to remodel cardiac ECM is notable in comparison to other vertebrates such as mammals, as mammalian hearts have a limited capacity to remove collagen from the heart. Therefore, rainbow trout may represent a useful model to study ECM remodeling in the vertebrate heart. However, little is known about the mechanisms that regulate this response in trout. The objective of this thesis was to investigate the signaling factors and pathways involved in collagen type I deposition and removal in cardiac fibroblasts, the cells responsible for producing ventricular collagen. The application of cytokine transforming growth factor-beta 1 (TGF-β1) to cardiac fibroblasts induced collagen synthesis and altered the expression of key genes involved in remodeling. Repetitive treatment of TGF-β1 caused the fibroblasts to differentiate into myofibroblasts. The trout myofibroblasts exhibited increased gelatinase activity in response to TGF-β1, which may have played a role in the decrease in collagen observed in myofibroblasts. It was then hypothesized that deformation of cardiac fibroblasts could stimulate the pathways associated with remodeling. To test this hypothesis, fibroblasts were stretched and the phosphorylation levels of mitogen activated protein kinases (MAPKs) involved in remodeling were quantified. p38 and ERK1/2 MAPKs were significantly phosphorylated in response to stretch. The final goal of this thesis was to investigate the role of microRNA (miR) in collagen removal. This was achieved by transfecting trout cardiac fibroblasts with miR-29b, a miR known to be involved in collagen regulation. miR-29b transfection significantly decreased collagen type I protein. Associated with this response was a decrease in the transcript levels of col1a3 isoform. Together, the results of this thesis establish several key molecules and pathways involved in trout cardiac remodeling, and also provide further evidence that these factors are highly conserved between vertebrate species.
URI: http://hdl.handle.net/10214/16135
Date: 2019-05
Rights: Attribution 4.0 International


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