Investigating the Role of Epithelial-mesenchymal Crosstalk in the Pathology of Idiopathic Pulmonary Fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a disease of unknown aetiology, characterised by the progressive and irreversible scarring of parenchymal lung tissue that leads to respiratory failure and death. The disease is understood to be driven by an impaired and aberrant wound healing response, with an inappropriate reactivation of developmental signalling. The greatest risk factor for the disease is age, which is a process intimately associated with an increase in the burden of senescent cells. Such cells acquire a unique secretory phenotype and are known to have a significant impact on their local micro-environment.

It was hypothesised that an alteration in epithelial-mesenchymal secretory communication, due to senescent-like changes in the fibroblast phenotype, may detrimentally contribute to lung homeostasis. An in vitro model of the lung airway was established in which primary human lung fibroblasts (HLFs) were co-cultured with human bronchial epithelial cells (HBECs). HBECs were cultured on a semi-permeable, transwell insert and co-cultured with either normal (NHLF), fibrotic (FHLF) or senescent fibroblasts. Over 72 hrs of co-culture, wound healing was assessed, via an epithelial scratch assay, and epithelial regeneration was measured, via trans-epithelial electrical resistance.

Co-culture with NHLFs improves epithelial regeneration, however, FHLFs and senescent cells in co-culture show a diminished ability to promote epithelial regeneration and wound repair. The secretory repertoire of these cells contains elevated levels of IL-6, CXCL8, CXCL1 and GCSF (when assessed at both an RNA and protein level), factors strongly associated with the senescent phenotype. Targeting this secretome via treatment with the JAK 1/2 inhibitor Ruxolitinib attenuates these impairments and may point towards a new therapeutic strategy for the treatment of IPF.