Modulating type two alveolar epithelial senescence in acute lung injury and fibrosis
Item statusRestricted Access
Embargo end date31/07/2022
The work presented in this thesis aims to advance the understanding the role of cellular senescence following acute lung injury, and the subsequent processes that lead to pulmonary fibrosis and ventilator dependence. Herein is described various approaches that were taken to investigate type II alveolar epithelial (AT2) cell senescence as a potential therapeutic target in acute respiratory distress syndrome (ARDS). ARDS is common within the intensive care unit, consisting of the exudative, restorative and fibrotic phases, this disease is spatially and temporally heterogeneous across areas within the lungs. There are no biological therapies routinely used in clinic for this extremely challenging syndrome meaning there is an incredibly high mortality rate of around 40% in patients that are diagnosed with moderate to severe ARDS. Therefore, greater understanding of potential avenues for therapeutics in ARDS are needed, something all the more prominent during the recent SARS-CoV-2 pandemic. The AT2 cell is the stipulated progenitor cell in the lung, as AT2 hyperplasia is required for the repopulation of the alveolar epithelium following injury. Characterisation of senescent AT2 cells in-vitro (chapter 3) investigates the features of senescent cells that can be detrimental to functional tissue repair such as proliferative arrest and a pro-inflammatory senescence-associated secretory phenotype (SASP). Chapter 4 investigates senolytics, an emerging class of compounds that exploit specific phenotypic changes to selectively deplete senescent cells, as a possible pharmacological intervention in acute lung injury. Senescent AT2 cells demonstrate susceptibility to the senolytic compound ABT263 (Navitoclax) invitro, which shows promise for further study. ARDS is classically considered to be neutrophil-mediated disease, with neutrophil elastase (NE)-null mice reported to show reduced levels of active TGF-β and pulmonary fibrosis. In-vitro and in-vivo models were used to investigate the effects of NE as an inducer of senescence in AT2 cells (chapter 5). Finally, chapter 6 describes the development and characterisation of a β-galactosidase activated fluorescent probe, called XD-βGal, aimed at specifically labelling senescent cells for imaging both in-vitro and in-situ. Optical molecular imaging of senescent cells with fluorescent probes is an appealing method as it is iii incredibly versatile, and the monitoring of senescent cell burden within tissue would be of huge advantage for diagnosis and the stratification of patient treatments.