- Title
- Fibroblast senescence as a driver of idiopathic pulmonary fibrosis
- Creator
- Waters, David
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Idiopathic pulmonary fibrosis (IPF) is a chronic fibrosing interstitial lung disease of unknown cause with a median survival of only 3 years. Little is known about the mechanisms that precede the excessive collagen deposition seen in IPF, but cellular senescence has recently been strongly implicated in disease pathology. Senescence is a state of irreversible cell cycle arrest accompanied by an abnormal secretory profile and under normal conditions is thought to play a critical role in both development and wound repair. Once a senescent cell has contributed to wound repair it is promptly removed from the environment via infiltrating immune cells. However, if immune clearance fails, the persistence of senescent cells is thought to drive disease pathology through their abnormal secretory profile. One of the major cell types involved in wound healing are fibroblasts, and increased numbers of senescent fibroblasts have been identified both in the lungs of IPF patients and in fibroblast cultures from IPF lungs. The question of what is driving abnormally high numbers of fibroblasts into senescence remains unanswered. Thus, we set out to develop a model of in vitro senescence and to investigate the effect of senescent lung fibroblasts on non-senescent lung fibroblasts. Chapter 1 reviews the literature on fibroblast senescence in the context of IPF. Chapter 2 characterises a model of fibroblast senescence in vitro. Exposing human lung fibroblasts to 150μM hydrogen peroxide (H₂O₂) for 2 hrs recapitulated features of the senescent phenotype. Moreover, we show that targeting signal transducer and activator of transcription 3 (STAT3) attenuated IL-6 production, reduced p21 levels, decreased SA-β-Gal accumulation and restored normal mitochondrial function. In Chapter 3 we investigate the stability of senescence in vitro and show that the oxidant-induced model of senescence is stable for at least 7 days. Although senescence was confirmed using multiple markers, increased expression of p21 was the most consistent and reproducible marker for identifying senescence in vitro. Chapter 4 reveals that conditioned media from senescent fibroblasts increases p21 and collagen Iα1 levels in non-senescent fibroblasts. In co-cultures of senescent and non-senescent fibroblasts, senescence was transferred from senescent to non-senescent fibroblasts, with the field of senescence dissipating with increasing distance from senescent cells. The content of this thesis provides the foundation for further research into fibroblast senescence in the context of IPF by modelling and characterising senescence in human lung fibroblasts in vitro. Two important conclusions have emerged from this work: i) investigations into STAT3 inhibition provide important proof-of-concept evidence for a novel pharmacological approach to prevent the onset of senescence, and ii) senescent primary human lung fibroblasts are capable of inducing senescence in neighbouring non-senescent cells to spread the phenotype in vitro and, potentially, in vivo.
- Subject
- IPF; senescence; wound repair
- Identifier
- http://hdl.handle.net/1959.13/1513915
- Identifier
- uon:56783
- Rights
- Copyright 2019 David Waters
- Language
- eng
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