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Abstract
Vascular smooth muscle cells (VSMC) in the healthy adult arterial wall are a highlydifferentiated
cell type with low levels of proliferation. However, when activated these cells can
undergo a phenotypic change to become proliferative, migratory and excrete higher levels of
extra-cellular matrix. While this cellular change is an essential element of the adaptable
vasculature, excessive proliferation of VSMC underpins the development of a number of
disease states, including atherosclerosis and restenosis after balloon angioplasty.
The activation of VSMC is dependent on intracellular signalling pathways broadly altering gene
expression. A key feature of this process is the initial potent regulation of transcription factors
such as Egr-1, c-Jun and Ets-1, which then drive further transcriptional changes resulting in
phenotypic change. The aim of this thesis was to discover novel genes, particularly transcription
factors, regulated early upon stimulation and to characterise their contribution to the activation
of VSMC.
A key stimulus for activation of VSMC is the release of fibroblast growth factor 2 (FGF-2). A
microarray used to explore the effects of FGF-2 exposure demonstrated the extensive nature of
transcriptional modulation. In addition, it highlighted a number of transcription factors that were
not previously described in VSMC: p8, ATF-4 and SHARP-2. In particular, SHARP-2 was
potently upregulated and was reconfirmed in animal models of vascular injury. The subsequent
contribution these factors make to VSMC activation was also demonstrated. p8 strongly induced
VSMC proliferation, while ATF-4 contributed to cytokine production and SHARP-2 potently
downregulated VSMC differentiation markers.
A second area that was explored related to a gene known as YRDC, which was found to be
upregulated upon stimulation of VSMC. YRDC is highly conserved across almost all cellular
life, however its function remains unknown. A number of novel splice variants of YRDC were
discovered and demonstrated to be differentially regulated in VSMC upon stimulation. Further
work to commence characterising its function showed that it interacts with key ribosomal
proteins and most likely plays a role in regulating translation.
The discovery of the relevance of these genes to vascular biology in addition to their
transcriptional regulation makes an important contribution to increasing our understanding of
the molecular mechanisms behind vascular remodelling.