KCa3.1 channel inhibition prevents fibrotic responses in a human lung explant model

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a common, progressive and invariably lethal lung disease with little effective therapy. Animal models potentially help with understanding disease mechanisms, but to-date, the commonly used bleomycin mouse model of lung fibrosis has largely failed to predict efficacy in IPF. We hypothesise that human lung explant tissue will provide a predictive substrate for the assessment of anti-fibrotic strategies in IPF. Aims To examine pro-fibrotic TGFb1-dependent responses in ex vivo human lung parenchyma, and their modulation by KCa3.1 ion channel inhibition. Methods: 2 mm3 pieces of human lung parenchyma were cultured for 7 days in DMEM ± TGFβ1 (10 ng/ml) and pro-fibrotic pathways examined. The effects of KCa3.1 channel blockers, TRAM-34 and ICA-17043 on inhibiting “fibrosis” were examined. Results: Immunohistochemical staining demonstrated increased expression of collagen type I (P<0.001), αSMA (P<0.01), FSP-1 (P<0.05) after TGFβ1 exposure when compared to control tissue. qRT-PCR demonstrated increased TGFb1-dependent expression of αSMA, Collagen type I and Collagen type 3 (P<0.05). Collagen secretion was significantly increased following TGFβ1 stimulation (P<0.01). These pro-fibrotic responses were inhibited by KCa3.1 channel blockade. Conclusions: Human lung explants may provide an alternative to the use of animals for the study of fibrotic mechanisms and novel drug interventions in human lung fibrosis. In maintaining the complex cell-cell and cell-matrix interactions of human tissue, this model may better predict drug efficacy in clinical trials. This study also supports the view that KCa3.1 channels are a promising target for the treatment of IPF.