A humanized animal model of pulmonary fibrosis based on cellular senescence

Abstract

Rationale: Cellular senescence is a key mechanism implicated in the pathogenesis of pulmonary fibrosis.

Objective: To test if the inoculation of senescent human fibroblasts in mice generates lung fibrosis, and whether this model is useful to assess antifibrotic or senolytic drugs in vivo.

Methods: Immunodeficient mice were inoculated intratracheally with proliferating human lung fibroblasts (IMR90), senescent human lung fibroblasts induced by γ-irradiation (gIR-IMR90), or bleomycin as control. After 21 days, lung fibrosis was determined by immunohistochemistry (IHC), and quantified by hydroxyproline assay and Ashcroft score. Gene expression analysis was performed using senescence markers. Furthermore, a group of mice with established fibrosis were treated with pirfenidone, nintedanib or placebo administrated orally for 14 days. Another group was treated with navitoclax (ABT-263) or vehicle. Collagen deposition was measured by hydroxyproline assay and IHC.

Results: Inoculation of gIR-IMR90 elicited a progressive lung remodeling process characterized by increased score of fibrosis (Ashcroft score, p<0.05) and collagen deposition (hydroxyproline assay, p<0.001). IHC using human vimentin detected human cells in the fibrotic lesions, and expression levels of CDKN2A (human p16INK4a) were higher in gIR-IMR90 group. Nintedanib, pirfenidone and navitoclax decreased pre-established lung fibrosis, confirmed by histology and reduced levels of hydroxyproline (p<0.001).

Conclusion: Intratracheal inoculation of gIR-IMR90 generates progressive lung fibrosis in mice that is reduced by antifibrotic drugs. This model can be used to test novel drugs for pulmonary fibrosis in vivo.