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Title: Lung disease in the cystic fibrosis mutant mouse
Author: Davidson, Donald J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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The discovery, in 1989, of the gene responsible for Cystic Fibrosis (CF), the cystic fibrosis transmembrane conductance regulator (CFTR), led to the development of mouse models of this disease. Such models were designed to facilitate the dissection of disease pathogenesis, to study the correlation between genotype and phenotype and to establish an invaluable resource for the development and evaluation of novel therapeutic agents. Fundamental to the success of such studies was the requirement that the mutant animals should develop the key phenotypic features of CF in humans. Initial characterisation of the first mouse models of CF demonstrated that they could be unequivocally distinguished from their wild type littermates and displayed many important disease features. However, the most important clinical consequence of CF, the development of chronic pulmonary infection with fibrotic lung damage, was not initially evident. In studies that preceded this thesis, we demonstrated an abnormal pulmonary phenotype in the Edinburgh CF mouse on an outbred MF1 background, in response to repeated exposure to CF related respiratory pathogens. These observations established this mouse as an important model system for studies aimed at elucidating the mechanisms involved in the development of CF lung disease. The aims of this thesis were 1) to further characterise lung disease in mouse models of cystic fibrosis, and 2) to study the mechanisms underlying the development of this disease. Firstly, this thesis describes 1) the development and quantification of methods for the delivery of bacteria to the murine lung and 2) the analysis of the histopathological phenotype of mouse models of CF congenic on a C57B1/6N background, in response to such techniques. These studies were performed using a clinical strain of Staphylococcus aureus, a pathogen that is characteristic of the early stages of lung infection in CF. Until recently the mechanisms by which dysfunction of CF lR could lead to the development of characteristic CF lung pathology remained unclear. However, several compelling, and competing, hypotheses have been proposed, based largely on in vitro studies. This thesis also describes studies designed to complement the published research by utilising mouse models of CF and address the relevance of several of these theories in this model system. It has been proposed that CFTR interacts directly with P. aeruginosa to internalise these bacteria into airway epithelial cells. It is postulated that this process plays a role in lung defence and is compromised in CF. This thesis describes preliminary in vivo studies addressing this mechanism in mouse models of CF. Although internalisation of P. aeruginosa was observed, no difference was demonstrated between CftrtinlHg" /Cftrtrr,lHgu mice and non -CF littermates. Airway surface liquid (ASL) from primary cultures of human airway epithelial cells has been shown to display salt sensitive antibacterial activity, the dysfunction of which has been implicated in the pathogenesis of CF lung disease. Airway Beta Defensins have been demonstrated to constitute an important component of this defence system. This thesis describes studies to characterise mouse Beta Defensin -1 (mBD1) and contrast it with human Beta Defensin -1 (hBD1) and concludes that a) synthetic hBD1 and mBD1 both display salt- sensitive antibacterial activity, b) hBD1 may play a role in determining the spectrum of lung pathogens that characterise CF and the predilection of P. aeruginosa for the human CF lung, c) dysfunction of mBD1 in Cftr helHgu mice may contribute to the lung phenotype observed in response to S. aureus, and d) the differences demonstrated between mBD1 and hBD1 may result in species specific profiles of bacterial susceptibility secondary to CFTR dysfunction. In order to complement these studies by performing analysis of native murine ASL this thesis describes the development and characterisation of a primary culture model of differentiated mouse tracheal epithelium, grown at air/liquid interface. This model demonstrates confluent, polarised epithelium, with differentiation to produce ciliated and secretory cells, expression of Cftr and murine Beta Defensin genes and a characteristic electrophysiological profile.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available