Title: Development of a Novel Ex Vivo “Breathing” Lung Slice Model to Investigate the Dynamic Relationship Between Tidal Ventilation, Deep Inspiration and the Development of Airway Remodelling
Funder: Asthma UK

Abstract: Transforming growth factor-β (TGFβ) is a widely distributed, pleiotropic cytokine. It is released from all cells as a latent complex sequestered in the extracellular matrix, which requires activation for biological function. TGFβ activation is fundamental to the maintenance of normal lung function and biological homeostasis. However, increased TGFβ activation promotes pathological changes in the lung in many respiratory diseases including asthmatic airway remodelling. There is therefore a clear unmet need to further understand the mechanisms governing homeostatic activation of TGFβ in order to understand how this process becomes dysregulated in disease. Several mechanisms of TGFβ activation have been described, however, activation in response to mechanical stimulation (for example cell contraction and stretching) via integrins is thought to be a key mechanism in vivo. This raises the possibility that cellular stretch during tidal ventilation may activate TGFβ in the lung. Certainly high-tidal-volume ventilation has been shown to increase TGFβ activation in vivo. However, the effect of inducing cyclic stretch in cells has opposing effects on TGFβ activation in vitro, with TGFβ activation increasing in some cell types but decreasing in other cell types. The dynamic relationship between normal tidal ventilation during breathing and TGFβ activation in the lung, and the role of tidal ventilation in regulating normal lung homeostasis and the development of asthmatic airway remodelling has not previously been investigated. Investigations in to the effects of tidal ventilation in ex vivo lung tissue are limited due to the absence of a suitable model. Precision-cut lung slices (PCLS) provide an excellent ex vivo system for studying airway biology and asthma pathogenesis. However, the PCLS are maintained in culture conditions that are not subjected to the constant mechanical stimulation observed during breathing in vivo. Therefore, the effects of tidal ventilation are not considered. Improving this model to incorporate mechanical stimulation to mimic breathing would provide a more physiologically relevant model for studying asthma and airway biology. The over-arching aim of this proposal is to develop a novel ex vivo “breathing” lung slice model that induces mechanical stimulation to PCLS to mimic tidal ventilation. This model will enable in-depth investigations in to the effect of tidal ventilation on homeostatic regulation of TGFβ activation in lung tissue, and the effects of tidal ventilation on the development of asthmatic airway remodelling. The proposal will address three specific aims: Develop a novel system to model the mechanical action of tidal breathing in ex vivo PCLS Utilise the novel ex vivo “breathing” lung slice model developed in Aim 1 to determine the effect of varying inspiration, and bronchoconstriction on mechanotransduced TGFβ activation and subsequent airway remodelling. Investigate how varying ventilatory strategies and matrix stiffness affect TGFβ activation and airway remodelling in asthma, and whether it differs from subjects without asthma.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS;2.5 RESEARCH DESIGN AND METHODOLOGIES (AETIOLOGY)
Health categories: RESPIRATORY