Arterial remodeling is a process by which arteries respond to sustained changes in their mechanical environment. This process occurs in a way such that an artery's local mechanical environment (circumferential, shear, and axial stress) is maintained at a homeostatic level. However, most studies utilize a methodology that controls the global parameters (pressure, flow rate, and axial stretch). This approach often confounds the results since the actual drivers of remodeling are not independently isolated. This research involved developing a methodology and system capable of independently controlling each of the local parameters and examining the effect of axial stress on remodeling. An organ culture system capable of monitoring and controlling the three global parameters and calculating the cross sectional geometry was developed. This combination of hardware was incorporated into LabVIEW which afforded the user the ability to define desired values for the local mechanical parameters. Porcine common carotid arteries were cultured for seven days in this system under physiologically normal circumferential and shear stresses and a constant axial stress of either 150 kPa or 300 kPa. Material response, general arterial morphology, tissue viability, and collagen synthesis were examined in order to gauge the effectiveness of the organ culture system and assess any arterial remodeling. The results of this study demonstrate the ability of the organ culture system in achieving and maintaining target values of stress throughout the culture period. Cell viability, general arterial morphology, and collagen synthesis rates were maintained for all arteries. The elevated axial stress appeared to cause a softening of the artery in both the axial and circumferential direction. It was hypothesized that this softening was the result of a changing collagen structure. Additional softening seen in arteries was attributed to the effects of the culture system.

Thesis (Ph. D.)--University of Missouri--Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves: 106-117). Also available on the Internet.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Errata slip inserted. Includes bibliographical references.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Errata slip inserted. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "December 2007" Includes bibliographical references.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Branchial arches (BAs) are a series of transient structures that develop on the ventro-lateral surface of the head in vertebrate embryos. BAs initially appear as a series of similar segments; as development proceeds each BA will contribute to different structures. Here, it was investigated the transcriptional mechanisms that instruct the different fates of the BAs in development. Initially, each BA contains a blood vessel, known as aortic arch (AA) artery, that connects the dorsal aorta with the heart. Remodelling of the AAs is crucial to form the adult heart circulation. This process leads to regression of the anterior AAs, running though the first and second BAs (BA1 and BA2), and persistence of the AAs contained in more posterior BAs (PBA). To identify the mechanisms that control remodelling of the AAs, we compared the transcriptomes and epigenomic landscapes of different BAs. Using RNA-seq and H3K27Ac ChIP-seq, we uncovered the activation of a vascular smooth muscle cell (VSMC) differentiation transcriptional program exclusively in the PBAs (and not in BA1/BA2). In support of this finding, we show that VSMC differentiation occurs specifically in the PBAs, but not BA1-2 in mouse embryonic development. Despite the absence of VSMC differentiation in developing BA1-2, cells harvested from these tissues reveal a spontaneous tendency to differentiate towards VSMC fate when grown in vitro, and activate several VSMC-specific genes (Myocd, Acta2, Tagln, Jag1). Together, our results suggest that forming VSMCs is a key process for the persistence of AAs. We also showed that cells derived from all BAs have the potential to differentiate to VSMCs in vitro. However, only cells in the PBAs differentiate to VSMCs in vivo, resulting in the maintenance of posterior AAs. In this study, we also uncovered a novel transcriptional principle that specifies the fate of BA2. Using ChIP-seq, we found that binding of Meis transcription factors establish a ground pattern in the BAs. Hoxa2, which specifies BA2 identity, selects a subset of Meis-bound sites. Meis binding is strongly increased at these sites, which coincide with active enhancers, linked to genes highly expressed in the BA2 and regulated by Hoxa2. Thus, Hoxa2 modifies a ground state binding of Meis to instruct segment-specific transcriptional programs.

A obesidade pode mudar as características das células endoteliais e musculares lisas (CMLVs). Reatividade e genes inflamatórios e de marcadores de fenótipo de CMLVs foram avaliados em artérias mesentéricas de resistência (AMRs) e de aorta de camundongos alimentados com dieta hiperlipídica (OB). RNAm para citocinas pró-inflamatórias e IL-10 foi aumentado em AMRs e aorta de OB. O relaxamento não foi alterado, mas a contração foi reduzida em AMRs e aorta de OB. AMRs apresentaram redução global da contração e a aorta apresentou redução específica para agonista adrenérgico. Maior modulação negativa por NO e prostanoides vasodilatadores foi observada em aorta, mas não em AMRs. RNAm para marcador do fenótipo sintético foi aumentado em AMRs de OB. Esses resultados mostram que as células endoteliais e as CMLVs de AMRs e aorta respondem diferentemente à obesidade. Inflamação e mecanismo de contrarregulação são induzidos em AMRs e aorta, que impediria a disfunção endotelial, mas não a mudança fenotípica das CMLVs em AMRs, que então, comprometeria sua capacidade contrátil. / Obesity may change the vascular endothelial cells and smooth muscle cells (VSMC) characteristics. Vascular reactivity and inflammatory and phenotypic markers for VSMC gene expression in resistance mesenteric arteries (RMA) and aorta from mice fed with high fat diet (OB). Pro-inflammatory cytokines mRNA and IL-10 were elevated in OB\'s RMA and aorta. The relaxation wasnt altered, however a reduction in contractility was observed in OB\'s RMA and aorta. A global reduction in contractility was observed in RMA and aorta demonstrated a specific reduction to adrenergic agonist. Higher negative modulation by NO and vasodilator prostanoids were seen only in aorta. Phenotypic markers mRNA were elevated in OB\'s RMA. The results shows that endothelial cells and VSMC from RMA and aorta respond differently to obesity. Inflammation and counter regulatory mechanisms are induced in RMA and aorta of which would prevent endothelial dysfunction but not VSMC phenotypic changing from RMA, compromising the contractile ability.

Vascular smooth muscle cells (VSMC) constitute an important component of blood vessels and are primarily responsible for vessel contraction. In vascular disorders such as hypertension and atherosclerosis as well as pregnancy and exercise, VSMC demonstrate increased capacity to proliferate and migrate, resulting in vascular remodelling. The actin cytoskeleton is an important component of vascular contractility and is also essential for proliferation and migration of VSMC. Vasoactive agonists such as Endothelin-1 (ET-1) and Noradrenaline (NA), have been shown to mediate VSMC contraction through changes in actin cytoskeleton and focal adhesion (FA) remodelling, and have also been reported to cause VSMC migration in the appropriate setting. The aim of this study was to investigate the signalling mechanisms responsible for FA dependent actin cytoskeleton remodelling of VSMC in response to ET-1 and NA, with a special focus on Hydrogen peroxide-inducible clone 5 (Hic-5). The latter is a FA protein shown to regulate actin cytoskeleton dynamics in small arteries in response to Noradrenaline (NA) and the response of VSMC to arterial injury and abdominal aortic aneurysm. We have shown that Src-dependent tyrosine phosphorylation of Hic-5 regulated its subcellular localisation in mouse embryonic fibroblasts and VSMC, but was not responsible for the effects of ET-1 and NA on actin filament remodelling or Hic-5 redistribution in VSMC. ET-1 stimulation caused an increase in Hic-5 localisation at FAs concurrent with an increase in the density of actin filaments, whereas NA stimulation caused a decrease in Hic-5 localisation at FAs in VSMC concurrent with actin filament redistribution at the cell cortex. Hic-5 was the FA protein that demonstrated the most dramatic changes in subcellular localisation in response to ET-1 and NA, when compared to paxillin (Hic-5 homologue) or vinculin (classical FA marker). NA-mediated changes in Hic-5 localisation and actin filament distribution were more pronounced compared to ET-1-mediated changes. Further investigation into the NA-induced changes suggested that actin filament disassembly preceded Hic-5 relocalisation from FAs to the cytosol. These results show that vasoactive peptides cause Hic-5 relocalisation and actin filament rearrangement in VSMCs in an agonist-dependent manner. Given that VSMC FA remodelling and actin cytoskeleton reorganisation occur during contraction and arterial remodelling, our data identify Hic-5 as a key regulator of these processes in response to NA and ET-1. Furthermore, these data have implications in agonist- specific VSM function such as migration and contraction.

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