449 Progression of silica-induced pulmonary fibrosis is arrested after selective ablation of Col1a1+ fibroblasts

OBJECTIVES/GOALS: Silicosis is a highly fatal progressive fibrotic disease of the lungs characterized by accumulation and persistence of fibroblasts that excessively deposit Collagen1a1. We sought to eliminate Collagen1a1-expressing fibroblasts through a targeted genetic ablation strategy and hypothesized that this would arrest the progression of Silicosis. METHODS/STUDY POPULATION: Silicosis was induced with a single intratracheal (i.t.) instillation of silica particles ( RESULTS/ANTICIPATED RESULTS: Targeted ablation of Col1a1+ fibroblast in established Silicosis resulted in a decrease in: 1) Col1a1+ fibroblasts by flow cytometry and within fibrotic nodules by immunofluorescent staining, 2) total lung collagen content by histology and hydroxyproline assay, 3) tissue-associated disease by microCT and an increase in arterial oxygen saturation by pulse oximetry. Cessation of targeted Col1a1+ fibroblast ablation resulted in a rebound effect in Silicosis disease progression. Following ablation, Col1a1+ fibroblasts expanded by proliferation (Ki67+) and total lung collagen levels returned to pre-ablation levels. DISCUSSION/SIGNIFICANCE: Silicosis is a often fatal disease with no FDA approved therapies. These results suggest that targeted loss of Col1a1+ fibroblasts in Silicosis is sufficient to arrest disease progression. Thus, it is essential to understand how targeted loss of pro-fibrotic fibroblasts can alter disease progression as a tool to develop novel therapeutic strategies.